Damion78's diy vise design

[aessinus]

First, thanks Damion78 - for posting your vise build.  This thing should trump my other 4", 4.5" & 5" vises; all gracile type.   I don't reckon I'll hurt this dude with a 6-10# hammer.  The old vise screw is just for the picture, btw. Kevin_Olson, great suggestion to move the pivot to the base.  

Got two tines from our equipment service rep on Monday, por nada.  Took a good part of the day for the horizontal bandsaw to get thru them using old blades, but at least the tool shop mgr didn't yell at me for using any new blades.  36"tall x 4 "jaws x .  Now for a hinge block to go with the 7/8" round head RR bolt.   I may have even scored a 1" ball screw from scrap; I did get a recirculating ball nut that was replaced on our NC machines.   One of the maintenance guys took some worn 20 foot ballscrews home 10 years ago for fence top rails...   Said he'd try to cut a couple feet off his fence over the weekend.  Not good enough for 0.001" but should work a peach for this vise.   Guess I'll have to make him a bottle opener.

During the remaining lunch breaks, I milled the fixed jaw straight & about a 10" radius on the moving jaw.  There was also a 28" dia x 1" torch drop that they've been moving around/tripping over for 5-10 years.   When I told the shop mgr I was gonna borrow the welder to fab a base next week, he told me to load that in my Geo on Tuesday after the holiday.   A few gussets, hinge cheeks tomorrow & then I get to drill screw & box holes.   Luckily I can borrow the mag base drill overnite & I have cobalt.  After the milling, I know I'm going to need it..  

The only drawback is I may have to take it back to the shop for them to use on big straightening jobs.  You know, the projects created by new lift drivers tearing up rails, and gantry crane tracks, etc.  The jaws are 110# & the plate should be around 180#, so with the gussets, screw & handle, should be a bit over 300#.   I'm wondering if perhaps I should make it break down some.  

Opinions, anyone?

[matto]

More pics please!!

[aessinus]

There you go!  8# sledge for scale.

Planning to  drift the hinge cheek plates tomorrow.  Left side has to have an elongated hole; round head rail splice bolt has a 7/8 x 1 shoulder.

Still contemplating the post mount to keep it semi-portable.   That 300# weight has me pondering the wisdom of it.

Checked a different 1" x 5tpi acme screw.  It would be stout, but I'm afraid too slow for hot work.  Hopefully, there is a length of thomson shafting on my desk.

[gote]

This will be a fantastic vise. Both jaws heavy and transferring the load down to the base plate. I like that. It will be a dream for upsetting.

[aessinus]

1 hour ago, gote said:

This will be a fantastic vise. Both jaws heavy and transferring the load down to the base plate. I like that. It will be a dream for upsetting.

Moving the hinge to the ground was Kevin Olson's suggestion.  Since they were full forks, I figured "Why not"?   It will look like a hand-vise for the Jolly Green Giant, but it ought to be sturdy.

After checking load ratings for Thomson ball-screw shafting vs acme, I ordered 1-1/2" acme & three nuts.  At <$90 from Mcmaster, I'm fairly pleased to have that be the only purchase so far, and that's enough shafting to do two more vises, maybe. 

On the scrounge for something both hold two nuts, in time, to prevent them locking.  I have a 4" ball hitch, but it's justs looks too big.  Hunting a 3" & several buddies looking too.   Still need something fairly heavy wall for the hinge barrel & settle on an initial mount design....

If only work would stop interfering with my play time. 

 

[arftist]

Nice.

Looks like a nice direction for some of us to start heading in. 

Wouldn't mind seeing an 8 or 10 inch jaw from some of the multiple cwt hammer owners.

[aessinus]

One of my buddies scored me a ball hitch that's 2 5/16; mounting stud is within 0.050" of the acme minor diameter, so welding should be fairly straightforward.  Have to clean, anneal & bore it for a handle.

32 minutes ago, arftist said:

Wouldn't mind seeing an 8 or 10 inch jaw from some of the multiple cwt hammer owners.

As it stands, the jaws are 4", however, I could modify them to make them wider...  I have a scavenged EDM machine way, 3/4"x 3"x16"long that is hardened.  Could be cut to about 8" jaws and left unhardened.  I would have to anneal and check for air-hardening alloy of course, but I'm not in any particular rush on this dude.  Reduce some current jaw length (2"right now) & weld in place.

Jaw width opinions?

[navasky]

That looks fantastic. I've been wanting to make a vise from forklift tines forever. Just out of curiosity have you thought of putting the screw on the outside a la the vertical vise? It would save having to drill those 2 big holes and you would be able to grip longer pieces.

[aessinus]

Thanks for the link.  I might make one of those for the shop at work,  We have a short, heavy 6" there already, but could stand another taller one for filing & oddball shapes.  That vertical looks pretty adaptable, just not super robust.  This one should fit the robust need at home pretty well.  Got the hitch ball drilled  & handle 50% done; planning to upset one end tomorrow at lunchtime & maybe thread a ball for the other.  I'm still on the prowl for a big bushing that's already drilled for the bottom hinge.  Carrying all the parts around in my truck, just in case I get some spare time to work on it.  

[nkearns]

This looks great. Any update?

[aessinus]

@nkearns Only a bit.  Screw ball (go ahead people, I'm calloused) is welded on, drilled for the handle & screw box is welded with key.  I've only used a single nut for the threads thus far, but I located another nut that I may weld to the 1st to double the thread length.  I'm still debating on total screw length because I've left the screw itself about 18". 

Just this am I received the email for the 1st set of spherical washers (1-9/16") from grainger are finally here for pickup.  The 2" had a 1-2 month leadtime, so maybe by mid-Dec....  2" set are for the fixed jaw to allow the key relief.

Handle is going to get @jlpservicesinc's blacksmith diamond treatment.  Huge thanks to her for the sketches of the particular facets & step-by-step instructions.  I printed the sketch & pinned it to my office wall so I can stare at it daily.  Should make the vise a bit of a showpiece.

Hopefully next week I can get back in the welding area for the lower hinge block.  Then boring the screw holes on the mill.  I may even get to EDM the hole/keyway in the fixed jaw.  Been itching to play with the Charmilles anyway.  Final grinding to bell the holes & internal keyway is all going to be by hand to get the travel arc just so. 

Still deciding on the distance from the jaws to the screw centerline.  Measured my 3 shop vises & the heavy one at work; they all are approximately 6".  I'm thinking though that around 8" down would give me more throat & I don't believe I will get any noticeable flex in the 1-1/2 x 4 tine material.... 

I'll try for some pictures this afternoon in the daylight.

[jlpservicesinc]

Traditional leg vises use several different technologies to keep the jaws in line..  

 

First is the bottom pivot is actually tapered.. Secondly the side plate and the bottom plate on the vise jaw are has the exact taper as the 2 side plates.. 

This is actually how the vises last so long even in smaller lighter sizes..  basically the bottom mount to the moving arm acts as a tapered seat with the bolt acting as a way to keep load on one side of the bosses while not loaded.. 

On vise size.. It comes down to what you are making.. If you look at the statistics most vises are in the 5" and down range..   Rarer are the 6" and up.. 

As you increase jaw width you also increase thickness..  

If you are making 20lbs leaf scrolls then a larger vise would offer greater support to the forged mass.. 

If you are making knives then the added size can get in the way.. 

If you are making colonial style hardware a vise that is 6" wide with narrow jaw faces will serve you the best as then you can run hinges down the side of the vise and the hinge barrel will have good support where on a 5" jaw the hinge would only be partially supported.. 

So, be careful making a vise to big unless you know what the intended purpose will be..  

 

I've attached a bolt made for a 8.5" jawed vise.. the jaw thickness is just over 1" perfect for hardware, and filing..  this vise still needs to have the joint rehabbed..  You can see where the bolt was missing the nut as it had been replaced at some point in history with a straight bolt which messed the joint up completely.. 

[JHCC]

Fascinating; I never knew that about the tapered pivot bolts. Learn something new every day.

Impressive callouses in that last photo, by the way.

[aessinus]

2 hours ago, jlpservicesinc said:

First is the bottom pivot is actually tapered.. Secondly the side plate and the bottom plate on the vise jaw are has the exact taper as the 2 side plates.. 

This is actually how the vises last so long even in smaller lighter sizes..  basically the bottom mount to the moving arm acts as a tapered seat with the bolt acting as a way to keep load on one side of the bosses while not loaded.. 

.......

I've attached a bolt made for a 8.5" jawed vise.. the jaw thickness is just over 1" perfect for hardware, and filing..  this vise still needs to have the joint rehabbed..  You can see where the bolt was missing the nut as it had been replaced at some point in history with a straight bolt which messed the joint up completely.. 

Well, now I have to go take all four vises apart..... Thank you once again for the explanation & photos.  I had no idea.

Size-wise, I have a 4", 4-1/2", 5" at home & bought a short heavy 6" for the maintenance shop at work.  For light filing of blades or similar, I actually prefer my bench mount saw vise.  Was my grandfather's vise to file his cross-cut & 2-man.  Been using it for work/pleasure for 40+ years.  I have a fair few vises. 

This one was rather a personal challenge & the plan is to make it semi-portable for the instances we need it at work.  Amazing what forklifts will "modify" by inexperienced drivers.  I can always easily thin the jaws, add width extensions etc. without the nagging notion of messing with a piece of history.  Besides, I had everything as found items, except for the spherical washer sets.  Guess I get to go in search of a tapered reamer for the hinge or make a drift.... 

[jlpservicesinc]

2 hours ago, aessinus said:

Well, now I have to go take all four vises apart..... Thank you once again for the explanation & photos.  I had no idea.

Size-wise, I have a 4", 4-1/2", 5" at home & bought a short heavy 6" for the maintenance shop at work.  For light filing of blades or similar, I actually prefer my bench mount saw vise.  Was my grandfather's vise to file his cross-cut & 2-man.  Been using it for work/pleasure for 40+ years.  I have a fair few vises. 

This one was rather a personal challenge & the plan is to make it semi-portable for the instances we need it at work.  Amazing what forklifts will "modify" by inexperienced drivers.  I can always easily thin the jaws, add width extensions etc. without the nagging notion of messing with a piece of history.  Besides, I had everything as found items, except for the spherical washer sets.  Guess I get to go in search of a tapered reamer for the hinge or make a drift.... 

I think it's a personal undertaking.. I've always wanted to build a 10" one.. do I need a 10" forged leg vise.. NO.. But it would be cool.. for some reason Large vises have a coolness factor.. Everybody who see's one always says"  Boy where did you find that one"?  how much does it weigh?  And then I'd love to have one that big..  

I have attached pictures of the support bosses of the main leg with the joints clearly seen.. You can see the taper from top to bottom.. first few are the 8" columbian, next is a generic 4.5" I use both in the trailer and the little one gets used more and is mounted right on the forge..  The next are of the (3)  extra for the school once up and running and range from 5.5" for 2 of them and 6" for the other one.. All tapered bosses..   

On the 8.5" model I have also shown where the bosses don't align and is the reason it needs a rebuild.. Not sure if you can see in the photo but it's all clamped together  to keep everything straight for when it goes into the forge to redress the joint area.. 

This information isn't well known and is the reason I shared it..  The new style leg vises don't have a tapered bolt or tapered bosses and will last probably a lifetime of use..  I just know that them old anvil and vise makers had it figured out so I try to emulate what they did..   

[gote]

On 2016-10-14 at 4:44 PM, jlpservicesinc said:

Traditional leg vises use several different technologies to keep the jaws in line..  

First is the bottom pivot is actually tapered.. Secondly the side plate and the bottom plate on the vise jaw are has the exact taper as the 2 side plates.. 

This is actually how the vises last so long even in smaller lighter sizes..  basically the bottom mount to the moving arm acts as a tapered seat with the bolt acting as a way to keep lo

 

I do not really understand this. Of course a tapered pivot in tapered holes can be pushed in so that there is zero play but how do you do that if there is a head on the pivot? It seems to me that it is no better than a non-tapered. I would have thought that the play between the plates would be the most important way to control the jaw. The distance from the center of rotation (sideways) is much larger. I have in the pipeline to shim my vise to decrease lateral movement. I do not trust my skill to be able to bend the plates the exact amount. I will also have to figure out how to lower the holes in the side plates since this is a German style vise where the moving jaw slides on circular surfaces on the fixed jaw and these surfaces no longer support as they should.

[jlpservicesinc]

2 hours ago, gote said:

I do not really understand this. Of course a tapered pivot in tapered holes can be pushed in so that there is zero play but how do you do that if there is a head on the pivot? It seems to me that it is no better than a non-tapered. I would have thought that the play between the plates would be the most important way to control the jaw. The distance from the center of rotation (sideways) is much larger. I have in the pipeline to shim my vise to decrease lateral movement. I do not trust my skill to be able to bend the plates the exact amount. I will also have to figure out how to lower the holes in the side plates since this is a German style vise where the moving jaw slides on circular surfaces on the fixed jaw and these surfaces no longer support as they should.

Not clear on what you mean by  " I do not really understand this. Of course a tapered pivot in tapered holes can be pushed in so that there is zero play but how do you do that if there is a head on the pivot?"....                 What head on a pivot???? 

 

The bolt does not center the jaw.. The pressure on the side forces of the taper force the jaw mount to one side..  This puts force onto one side of the cheek plate keeping the jaws in alignment at the the top..  Side pressure against only one cheek plate.. 

The bottom portion of the vise jaw boss has a taper the same as the cheek plates..  Narrower at the bottom than the top..  The bolt that goes through both cheek plates and the  vise jaw leg boss has the same taper with a tapered hole.. 

The tapered pin (threaded bolt that goes through) takes up the cheek plates to keep them fairly tight and from spreading.. 

A tapered cheek vise will not open past a certain distance between the jaws because of the wedging effect of the cheek plates.. If you loosen the bolt it will open more because you are forcing the wedge into the cheek plates spreading them.. 

[gote]

I am learning something new all the time Thank you. It never occured to me that the plates would not be parallel but you are right I have a taper of about 0.5%. The difference in dimension is about the same as the play between the plates. I still have not time to disassemble the vise but I tried to push in temporary shims. That made the side play in the jaws disappear nearly completely. I still do not understand how the tapered pin can push the jaw against one side.  Maybe I am using the wrong word. With pivot I mean the bolt that goes through the plate and is the hinge. It has a head on one side and a nut on the other. It cannot be forced further than the head. allows.

I would be possible to turn a pin with a step and let it push the jaw against the plate with different hole sizes in the plates but it is not something I would like to do.

[JHCC]

29 minutes ago, gote said:

I still do not understand how the tapered pin can push the jaw against one side. 

If I understand jlpservicesinc correctly, you have to think of what happens when the vise is under load. When you tighten the screw, there is pressure at three points: where the jaws grip the workpiece, where the screw squeezes the jaws, and the pivot at the base of the movable. If there is any room for the pieces at these three points to move, they will, until they come to some limit on their range of motion. The limit at the jaws is the thickness of the workpiece; at the screw, its length. Now, when there is no load on the vise, the boss at the base of the jaw has a certain amount of sideways play, but when it goes under load, that load will force it to take the path of least resistance: towards the thin end of the tapered pin. It moves in this direction until it reaches the cheek plate and stops. Because there is this sideways force between the boss and the cheek plate, the jaws are forced into alignment, and the sideways play is eliminated.

[jlpservicesinc]

2 hours ago, JHCC said:

If I understand jlpservicesinc correctly, you have to think of what happens when the vise is under load. When you tighten the screw, there is pressure at three points: where the jaws grip the workpiece, where the screw squeezes the jaws, and the pivot at the base of the movable. If there is any room for the pieces at these three points to move, they will, until they come to some limit on their range of motion. The limit at the jaws is the thickness of the workpiece; at the screw, its length. Now, when there is no load on the vise, the boss at the base of the jaw has a certain amount of sideways play, but when it goes under load, that load will force it to take the path of least resistance: towards the thin end of the tapered pin. It moves in this direction until it reaches the cheek plate and stops. Because there is this sideways force between the boss and the cheek plate, the jaws are forced into alignment, and the sideways play is eliminated.

Ok, so just to clarify:  It's the vise cheeks and taper that keep the jaws in alignment when under pressure.. The bolt limits the spreading and this keeps the outside jaw from sinking lower when impact is made. This downward force acts like gravity and pushes the bottom jaw boss more sideways then down... The thru bolt is not receiving all the pressure.. This side load transfers some of the forces to the cheek.. 

Since the cheek plates and the boss on the jaw are tapered as the jaws open it wedges the jaws deeper at the front of the wedge.. This keeps the jaws in alignment as the jaws open past a certain point.. 

3 hours ago, gote said:

I am learning something new all the time Thank you. It never occured to me that the plates would not be parallel but you are right I have a taper of about 0.5%. The difference in dimension is about the same as the play between the plates. I still have not time to disassemble the vise but I tried to push in temporary shims. That made the side play in the jaws disappear nearly completely. I still do not understand how the tapered pin can push the jaw against one side.  Maybe I am using the wrong word. With pivot I mean the bolt that goes through the plate and is the hinge. It has a head on one side and a nut on the other. It cannot be forced further than the head. allows.

I would be possible to turn a pin with a step and let it push the jaw against the plate with different hole sizes in the plates but it is not something I would like to do.

The play is more than likely caused by either a worn bolt or a loose nut and worn bolt..  The cheek plates will flex some when tightened.. 

 

Think of a hill and a ball.. The ball will always roll down hill.. The tapered pin is the hill and the ball is the vise bottom boss.. The taper serves 2 functions: increases the contact area between the jaw lower boss (pivot) and the bolt vs a straight bolt  and helps to shed the load sideways into the cheek when struck.. 

 

It also helps with shear loads since the sideway forces involved redirects the load..

 

I've attached a crude drawing but it should help explain some of it..    Them old workmen who made all this stuff really had it figured out.. More knowledge has been lost than has been gained in my mind.   

 

Also while a lot of this information applies to blacksmithing foot vises as a whole there are variations for any given maker and/or where it was made..  German made vises and the older italian made vises are beautiful and beautifully made..   American's simplified and expedited everything.. 

 

By the way all the new commercially available vises have done away with the tapered bolt and bottom cheeks..  Costs more to MFG.. 

[Anachronist58]

I rilly like the RiffRaff this site attracts!

[gote]

I really appreciate the effort you are putting in. The pic is very helpful.

A tapered jaw will obviously take up some of the downward force and transmit to the side but how much? I do not have the time to calculate today but I doubt that it is very much. In the German pattern I have, the jaw rests directly on the top of the plates (which are rounded) so the bolt is unloaded from above. Unfortunately the bearing surfaces are worn so the bolt now takes the force. I will have to open the hole in the jaw upwards.

You draw with a play under the head and this of course solves my question regarding the head. However:

If the play would be 0 to 1 mm and the taper - as in my case - is 0.5%, the combined tolerance on the pin diameter and the hole is 0.005mm = 5 microns. Somehow this feels difficult to achieve in a blacksmith's vise. Even with the larger tapers shown in the photos, the tolerances will be very narrow.

Further if the taper of the pin/bolt pushes the jaw against one plate it will jam in the jaw. Compare a morse cone that has a much steeper taper. Thus it will turn with the jaw which will defeat the key you are showing on the head. My own pin/bolt does not turn with the jaw but sits fixed. That is a good thing, since I consider a bolt  that turns that way to be a design error. The nut will quickly get loose unless it is locked positively by peening, split pin or similar method.

If the nut is locked against the plate, a turning bolt will tighten when the vise is opened (Assuming nut to the right and right hand thread). Nut on the left hand will open the jaw and counteract the wedging you talk about.

What prevents lateral movement of the jaw is the top and bottom of the plates but the bolt sits in the middle. The plates do not necessarily move as flats when pinched in the midde. The corners may move less. I still think shimming is more effective and my test confirms that this works.

[jlpservicesinc]

1 hour ago, gote said:

I really appreciate the effort you are putting in. The pic is very helpful.

A tapered jaw will obviously take up some of the downward force and transmit to the side but how much? I do not have the time to calculate today but I doubt that it is very much. In the German pattern I have, the jaw rests directly on the top of the plates (which are rounded) so the bolt is unloaded from above. Unfortunately the bearing surfaces are worn so the bolt now takes the force. I will have to open the hole in the jaw upwards.

You draw with a play under the head and this of course solves my question regarding the head. However:

If the play would be 0 to 1 mm and the taper - as in my case - is 0.5%, the combined tolerance on the pin diameter and the hole is 0.005mm = 5 microns. Somehow this feels difficult to achieve in a blacksmith's vise. Even with the larger tapers shown in the photos, the tolerances will be very narrow.

Further if the taper of the pin/bolt pushes the jaw against one plate it will jam in the jaw. Compare a morse cone that has a much steeper taper. Thus it will turn with the jaw which will defeat the key you are showing on the head. My own pin/bolt does not turn with the jaw but sits fixed. That is a good thing, since I consider a bolt  that turns that way to be a design error. The nut will quickly get loose unless it is locked positively by peening, split pin or similar method.

If the nut is locked against the plate, a turning bolt will tighten when the vise is opened (Assuming nut to the right and right hand thread). Nut on the left hand will open the jaw and counteract the wedging you talk about.

What prevents lateral movement of the jaw is the top and bottom of the plates but the bolt sits in the middle. The plates do not necessarily move as flats when pinched in the midde. The corners may move less. I still think shimming is more effective and my test confirms that this works.

Look at the picture again..  The notch in the bolt head and the same cutout in the cheek keeps the bolt from turning..  Look at the pictures I posted earlier.of the newly made bolt. It shows these notches clearly.. 

I think in some way you guys over think this stuff..  

The drawing it shows that the bolt to the vise jaw is "almost" a tapered press fit.. I didn't say it "IS" a tapered press fit (and pull the bolt in till it binds) that would bind like a "Morse taper" by the way a morse taper "Will Not Hold" very well or bind (which is how it really works) if there is ample oil, dirt or grease in the socket with no inward pressure.. Remember for a morse taper to hold properly it has to be clean or lightly oiled and then "Forced in" till the two sides (faces of the female and male socket) have pressure evenly placed (IE Jammed together)..   This pressure inside the so called "almost tapered press fit" is controlled by how tight the nut is on the outside and hopefully you grease or at least oil the joints upon assembly.

The bolt is not to support the jaw, the cheeks are to support the jaws,,  The bolt is to add cheek pressure and it keep them from spreading as well as acting as the pivot for the jaw and keeping it located in the cheeks (pivot). 

It is a combination of all things.. Tapered cheeks, tapered jaw boss, tapered  bolt.. .  This makes the vise nearly indestructible and why they last so long.. without the tapered cheeks  the bolt becomes the main weight bearing. It will fail in short order as the bolt is in a shear plane all the time..  (They did make the cheaper ones  that way).

German vises use the cheek plates as part of the weight bearing and supporting structure but in a somewhat different manner.. If your cheek plates are damaged or the receiver bosses in the jaw for the cheek plates are damaged.. Then the first culprit to make it straight will be the bolt most likely deformed.. means there is deformation at the bolt, the vise jaw boss and the cheeks or a combination of all 3..

The only fix for this is to make everything like it was brand new with the proper clearances.. Adding shims is not how this is fixed.. Fixing it the right way with adding materials (IE welding) or putting back the materials (peening back) that have been distorted, checking to make sure the bolt is not deformed, making sure the clearance in the vise boss is not egged out..  ETC, ETC..  

For clearance you can make what every you want or find what works.. Your going to make the thing right... Just forge it out and then see what works..

(In regards to your question about bolt clearance under the head)

for the clearance around the side cheek with the bolt head on it..  The shaft under the head can be the same taper as the rest of it with no clearance at all.. Problem is if you tell someone this who has never made one they make the head exactly at the cheek and this  eliminates the ability for further adjustment in the future. and will actually make it so the contact area between the bolt and the jaw boss will be to small (it will be Sloppy).

 Then they come back and say I don't know what I'm talking about..  Because it didn't work for them and they spent all the time when they could have just drilled the hole out and put a regular bolt in.. 

 So after a new bolt is made.. make it exactly to the tapered fit.. Just leave some clearance under the head.. Is that more helpful.. 

then I say figure it out on your own.  The information is there.  "It's correct for this type of vise pivot"..   I've seen hundreds of examples and this design is the most robust.. I've also seen straight jaw bosses, straight bolts. I've seen lots with stripped threads because the jaws didn't align and the person just over tightened the bolt and as soon at they open the jaws which are now very tight at the 0-1" mark can barely be opened the rest of the way and they force it and the threads sheared off the bolt so no nut.. 

 

Give it some more thought and though it may seem frustrating and that its not understandable when the "Ah Ha" moment comes it will be crystal clear.. 

 

Just because something is made by hand via a blacksmith  does not mean it can not be accurate and made to an exact size..   By the way.. I'm not an artist blacksmith.. I'm a trades blacksmith..   

So, the simplest answer is to just fix what you find to be wrong..  If your vise doesn't have a tapered bolt forget all about what I wrote.. It's that simple.. 

Oh one other thing.. Some of the vises don't have a hotch to hold the tapered bolt..  since the taper on both cheeks has great area vs the pivot it still gets held against the pressure of the pivot to turn the bolt.. 

[gote]

I am afraid that the Ah Ha moment only goes further away.

I apologize if I misunderstand but you wrote: “with the bolt acting as a way to keep load on one side of the bosses while not loaded”. And “The pressure on the side forces of the taper force the jaw mount to one side.  This puts force onto one side of the cheek plate keeping the jaws in alignment at the top.  Side pressure against only one cheek plate”.

I understand this as that you mean that the bolt pushes the jaw against one of the plates because it is tapered. I cannot measure your vises but I measured on the pic. of one of them and find that the side plates deviate by 3.4% from vertical. Since the picture is taken from above it is probably less.

The situation when lateral play in the moving jaw is a nuisance is when one is gripping a round object and puts in a twist such as when tapping a hole axially in a round rod.

I understand you as that you mean that the taper in the bolt makes the jaw slide to the side.  

If something is going to slide to the side, the slope must be more than the coefficient of friction and that is several times higher than 3.4%. (already the pyramide builders knew this) Even if friction were zero, the side force is only about 3.4% of the lateral force, which hardly is enough to stabilize the jaw in the tapping operation referred to above.

The other possible way that the bolt can move the jaw, is that it pulls by engaging in the taper of the hole in the jaw and with a slope of 3.4% it will certainly jam. The Morse cone is a middle way between jamming too much and jamming too little. 3,4% is less than the Morse and will jam very efficiently.

Thus I very much doubt that a tapered bolt can stabilize the jaw by pushing it against one of the side plates.

Does the taper in the plates take up the forces from above if the bolt pulls them together?

Assume we have a force from above of 100 pounds. There is friction between the jaw and the plates. Say 90 pounds are taken up by friction. 10 pounds left. These ten pounds exert a side pressure on the plates of 10/0.034=294 pounds. Assume the cross section of the bolt is 1 square inch. Thus the tensile stress in the bolt is 294 PSI. Now assume pure shear in the bolt. There are two shear planes thus we get 50 pounds per plane and that gives us 50 PSI. The tensile stress in the taper-jaw-situation is thus nearly six times the shear stress in the pure- shear-situation.

Have I assumed too little friction? I do not think so. The coefficient of friction is 90/294=0.3 definitely not too low. If we assume 0.2 instead, the tensile stress will be 9 times higher. Have I forgotten the stiffness in the plates? No since the bolt has been pulled tight the plates do not relieve the bolt. They increase the tensile stress.

My conclusion is: Yes the taper will transfer force to the plates but that does not put less strain on the bolt. It only changes from shear to a much higher tension AND it is mostly by friction. The friction will only develop if the jaw sinks a little so it wedges. Thus there must be sufficient radial play in the bolt. Otherwise it is a question of shear anyway. If the bolt is pulling the plates so tight that the wedge-support situation develops without this radial play in the bolt, the spring will be unable to open the vise.  

The shear situation causes a stress concentration. How important this is, depends upon how soft the pieces are and how close the contact areas are.

Is shimming a bad idea? No. In my vise, the plates are much higher than vide. The distance from the bolt to the leg is much less than the distance from the bolt to the upper and lower edge of the plates. The bolt pinches in the wrong place. The edges of the plate will move less than the centre. This differs very much from the pics you show of rusty vises. In those cases you may be right.

Tolerances: With a 3,4% taper, the tolerances are about the H/h8 magnitude and that can be achieved with a suitable reamer (100$ if I can find on with the correct taper) and a good lathe  (and someone who knows how to do it). With my taper of 0.5% it will cost a fortune to have it done.

On 2016-10-29 at 10:27 PM, Anachronist58 said:

I rilly like the RiffRaff this site attracts!

 

RiffRaff = People regarded as disreputable or worthless. (Check your dictionary)

 

 

[jlpservicesinc]

39 minutes ago, gote said:

I am afraid that the Ah Ha moment only goes further away.

I apologize if I misunderstand but you wrote: “with the bolt acting as a way to keep load on one side of the bosses while not loaded”. And “The pressure on the side forces of the taper force the jaw mount to one side.  This puts force onto one side of the cheek plate keeping the jaws in alignment at the top.  Side pressure against only one cheek plate”.

I understand this as that you mean that the bolt pushes the jaw against one of the plates because it is tapered. I cannot measure your vises but I measured on the pic. of one of them and find that the side plates deviate by 3.4% from vertical. Since the picture is taken from above it is probably less.

The situation when lateral play in the moving jaw is a nuisance is when one is gripping a round object and puts in a twist such as when tapping a hole axially in a round rod.

I understand you as that you mean that the taper in the bolt makes the jaw slide to the side.  

If something is going to slide to the side, the slope must be more than the coefficient of friction and that is several times higher than 3.4%. (already the pyramide builders knew this) Even if friction were zero, the side force is only about 3.4% of the lateral force, which hardly is enough to stabilize the jaw in the tapping operation referred to above.

The other possible way that the bolt can move the jaw, is that it pulls by engaging in the taper of the hole in the jaw and with a slope of 3.4% it will certainly jam. The Morse cone is a middle way between jamming too much and jamming too little. 3,4% is less than the Morse and will jam very efficiently.

Thus I very much doubt that a tapered bolt can stabilize the jaw by pushing it against one of the side plates.

Does the taper in the plates take up the forces from above if the bolt pulls them together?

Assume we have a force from above of 100 pounds. There is friction between the jaw and the plates. Say 90 pounds are taken up by friction. 10 pounds left. These ten pounds exert a side pressure on the plates of 10/0.034=294 pounds. Assume the cross section of the bolt is 1 square inch. Thus the tensile stress in the bolt is 294 PSI. Now assume pure shear in the bolt. There are two shear planes thus we get 50 pounds per plane and that gives us 50 PSI. The tensile stress in the taper-jaw-situation is thus nearly six times the shear stress in the pure- shear-situation.

Have I assumed too little friction? I do not think so. The coefficient of friction is 90/294=0.3 definitely not too low. If we assume 0.2 instead, the tensile stress will be 9 times higher. Have I forgotten the stiffness in the plates? No since the bolt has been pulled tight the plates do not relieve the bolt. They increase the tensile stress.

My conclusion is: Yes the taper will transfer force to the plates but that does not put less strain on the bolt. It only changes from shear to a much higher tension AND it is mostly by friction. The friction will only develop if the jaw sinks a little so it wedges. Thus there must be sufficient radial play in the bolt. Otherwise it is a question of shear anyway. If the bolt is pulling the plates so tight that the wedge-support situation develops without this radial play in the bolt, the spring will be unable to open the vise.  

The shear situation causes a stress concentration. How important this is, depends upon how soft the pieces are and how close the contact areas are.

Is shimming a bad idea? No. In my vise, the plates are much higher than vide. The distance from the bolt to the leg is much less than the distance from the bolt to the upper and lower edge of the plates. The bolt pinches in the wrong place. The edges of the plate will move less than the centre. This differs very much from the pics you show of rusty vises. In those cases you may be right.

Tolerances: With a 3,4% taper, the tolerances are about the H/h8 magnitude and that can be achieved with a suitable reamer (100$ if I can find on with the correct taper) and a good lathe  (and someone who knows how to do it). With my taper of 0.5% it will cost a fortune to have it done.

 

RiffRaff = People regarded as disreputable or worthless. (Check your dictionary)

 

 

You are saying the basic same information..   Only one clarification..   The tapered bolt only holds the the jaws in alignment by keeping pressure of the bottom boss/pivot in contact with the cheek when there is no load and the jaws are nearly shut.. 

the bolt only holds the jaws straight while in the nearly closed position to about 1.5 -2" out..(nothing said about a load or force)    After that it's the taper of the cheek plates that holds the jaws straight..  If you want to talk about loads take a vise as in the pictures and it will make sense.. Tighten the nut as you move the jaws you will see the results.. Rust has nothing to do with it.. 

I high lighted your example above.. 

You are also talking about Torquing forces verses hammer forces or linear forces..   2 total different forces and this I was not referring to at all nor mentioned..  

A blacksmith leg vise will always have twist in it if you are threading a round rod.. it is deforming to offset the forces you are putting into it,    It's not really designed for the greatest jaw stiffness in a torsional use environment..  It's designed to be pounded on and the reason all the pieces are designed the way they are.. 

Those same torsion forces come into play when holding anything off center of the jaws..in a small vise you can see the amount of torque being applied as the off side jaw moveds towards the stable jaw very easily.. Larger vises have less deviation because of the larger mass.. 

a Torsion rod in a car twists to create a load at either end of it's attachment points an this is supposed to help recenter the car body mass..   so it bends then once the car is level again.. so is the rod.. 

A leg vise has very long members in relation to jaw and then screw distances and then pivot.. that 2FT of torsion rod..   You will get twisting in the front jaw no matter what you do.. it's like a torsion rod in a cars suspension.. 

You can tighten the joint all you want and it will still torque..  It's how it's designed.. 

The only way you can get little or no  torque movement is a very short jaw profile with very short pivot like in a machinist vise..

Your looking at this from a very different perspective..   What you see is a different picture of what I'm showing because of perspective..   I'm showing how the vise jaws stay in alignment with forces being applied in hammering which are downward or backwards (towards the rear jaw) for the most part..    

What I took away is : You are looking at twisting motion..    Ain't no way you are going to get them to stay straight to much torque load out at the very end of a long member.. 

You'd have to redesign the whole thing if you want to overcome torque loads.. 

Buy a very high quality machinist vise and you will be all set... . Apples, oranges.. Pineapples..   No wonder why it doesn't make any sense..  Your looking at how to stabilize the jaws against torque instead of straight downward force..

So,  because you are looking at this all torquey..    It is the exact opposite..  because the bottom boss and the cheeks are a taper.. As you twist the rod in the jaws the vise front jaw will want to torque as its' not only over coming your twisting forces but also now you have a wedged cam going on at the bottom. .  Basically your are wedging the jaw at the boss and this will actually cause a loosening of the area and the bolt will have little effect other than holding the cheeks together and keeping the jaw from rising..

In this situation  a straight sided wall would be best, (not wedging) but then you would end up with all the load when hamming on the vise going into the bolt unless you had a german vise where this load is shed partially by the cheeks and the guides bosses on the jaw... 

   Just put a wood wedge in a vise and tighten it slowly.. the wedge will raise..  or put it in a vise and just twist it with your hand.. it will raise as well... or a cold hardie. Even a better example..  

If the twisting of the jaws is really what your looking at eliminating they a high quality machinist vise will solve your problem.. 

Most old time shops had a leg vise and a machinist vise for the exact reason you are talking about...   

Even the big  8" Columbian vise which weighs 230lbs and the moving jaws leg  2.5"X 1.5" twists when I'm threading 3/4" rods. 

If a free world, with free thought..  You can do all you want to.. I'm merely showing how these things were made..   If shimming works for you.. Go for it. 

Personally I go and fix what is wrong and then I also account for the limitations of the equipment I am using and adjust to get the desired results..  I tap and thread rods in the foot vise all the time and find the twisting of little consequence other than having to realize there are other counter forces at play.. 

If it's the tapered bolt,   don't use one..   there is a reason this stuff works..    I'm not the designer or the engineer.. I'm just a user who shared what they know.. 

 

In the end you can do what ever you would like.. It's all good..  Right or wrong makes no difference as it's all perspectives which change with time...