Milling out dies for 50# Murray mechanical (basically an LG)

[DanielC]

So I am lucky to have a machinist brother, and this weekend he had time to help me with this project.

 

I am making japanese style bladesmithing dies for my appropriately sized hammer. Going with a 2" round face.

 

Started off with a block of 4140 I bought from a reputable steel supplier in my area. From this we took measurements from my original die, found the angle of the dovetail with a very expensive Intercomp angle finder, and began the dovetails. So far so good. Will be working on the face today, and then sometime this week, mill out the dovetail for the much larger bottom die. Also tried fitting the die in the hammer using the same keys, and it worked. Though I want to make new keys. Does anyone know the taper of the keys for these?

 

I plan on HT'ing each die seperated by a day, since I am working with 5gal of Parks 50, and if need be another 5gal of pre-heated canola beside it. I planned of using just parks for the smaller upper die, and maybe a very fast interrupt with the parks 50 and canola with the much heavier bottom die. I am trying to both avoid overheating my parks 50, and get past the cooling rate curve, and I am not sure that just 5gal of parks by itself will get the job done. I have read about several people using water for larger cross sections of 4140, but I am a chicken and will try this oil method first. Any objections to this? Have also been told to use a 450F temper. Anyone else pull back the hardness that much? For the upper die I was thinking closer to 350F.

[basher]

I would be very interested to see how you are working out the angles and tapers of the top die. I have Just hand ground a top die for my 90 lb spring hammer to use as a blade forging hammer. very slightly crowned center with tapers both sides It is a suck it and see work in progress. There is enough hammer ajustment to re flatten the die If I am way out . so far so good though.

[mike-hr]

Several concerns.. I see by the mill setup you are cutting the dovetail angle, but is this also tapered? you would need a shim between the die and the mill table.

The LG100 I made dies for, the sow block had approx. 1/8inch/foot taper. I reproduced this by sticking a 1/16" TIG filler under one end of the 6 inch parallels on the mill vise.

I feel your 5 gallons ain't enough, and the heat in the center will temper out any hardening you can get. I used a 15G beer keg with warm water. The die screamed a bit, but had good results.

Read up on Prussian Blue to dial the wedge key in, plan on a good half day to get 90% involvement.

It's been a year since I did this, I'm a bit fuzzy on who is tapered, and who isn't. Hopefully someone will chime in and correct me.

Edited December 7, 2015 by mike-hr
clarification

[DanielC]

I was under the impression that I didn't need to cut a taper on the dies, since the taper is on the female end in the hammer (could be totally wrong here. Wish there were literature)? My current dies, which were originals seems to be measuring somewhat the same width from both end, with maybe 1/32"-1/64" difference.

 

Currently they are milled with no taper. Is it absolutely necessary for this slight taper? And if it is, are both sides being tapered or just the one? Thanks.

[phabib]

FWIW, I was also surprised to only see taper in a single direction.  I expected to see both right/left taper and up/down taper.  Won't life be grand when we can 3D print whatever dies we want.  There are people 3D printing metals, but I don't know if anyone is doing tool steels yet.

[DanielC]

Unfortunately I jumped into it too quickly. We have feeler gauges I can use as shim stock, and have it fixed. I just misunderstood the full function of the single key dovetail. My mind has been on the Bradley so much.

 

So I just measured my lower and upper dovetail and it seems to follow the 100# LG of 1/8" per 12" as well.

And now that I look at the original die more, the more I understand where I totally screwed up. Sigh. So I guess the plan of action is to support it up and mill it out, while making a slightly thicker key. I mean we're only talking a .02 or. .03" diff. right?

[DanielC]

....or just buy another block and try again.

[mike-hr]

I'm sure you can save it. On the one I did (not saying it was correct), I marked the edge of the lower die that will end up being closest to the operator. I didn't taper this side, so it would lay against the sow block always. I called that point 'Home'. I cut the taper out of the off side, and used the key to drive the die toward 'Home'. Make sense? I think you can re-mill the off side with the 1/8/ft scenario, and be fine.

[DanielC]

21 hours ago, mike-hr said:

I'm sure you can save it. On the one I did (not saying it was correct), I marked the edge of the lower die that will end up being closest to the operator. I didn't taper this side, so it would lay against the sow block always. I called that point 'Home'. I cut the taper out of the off side, and used the key to drive the die toward 'Home'. Make sense? I think you can re-mill the off side with the 1/8/ft scenario, and be fine.

Is this the case for single dies? Just the one taper on the key side, to allow an actual wedge? It's hard to tell on my sow block which side is doing the actual taper since it is so minoot. I am assuming the taper in the sow block is on the key side?

[jeremy k]

You will be the first to know if your tapers or no tapers are right, or if the dies mating surfaces to the female dovetail are correct when both are in and the front edge of the dies either line up vertically or not (as in lengthwise "in line" with each other).

[mike-hr]

I was shooting in the dark when I did the lg100, and it was confusing as one of the parts works upside down. I backed off for a couple days, bought a slab of hard maple, glued and squared the wood so it was the same size as my steel blanks. I cut my dovetails and tapers in the maple first. it was fast, tangible, and helped me work out the cobwebs in my head

[jeremy k]

Even the new dies I got from Little Giant for my 100LG needed some modifying/different wedges so they lined up right, compared to the worn out set that were in it when I got it. All good now and they are seated and stay in place.

[DanielC]

Alright, so today we only had a little bit of time to get things set up for another day. Basically milled off one of the sides (End of the die, not where we milled before) of the die that weren't exact from the steel supplier (Cut with a bandsaw), to get a good edge. Used indicators to get it all set-up. Going to raise the die by 1/32" at the 3" long (Our of 4" long) mark, and clamping it down. Will check over and over until we feel it is all true and cut in the last taper on this die.

 

Will eventually get to the face of the die. This was but a minor hiccup. I usually always get something right eventually. My brother is a racecar engine machinist, and has a lot of nice little tools and gadgets to get what we need done, correctly. Of course, this is his first dovetail he has had to mess with, and going off of some of my direction, such as the omission of this 2nd taper. *shrug*

[DanielC]

Just an update. Took a break off of the project to finish other things. Bought an endmill to quickly finished the swoops that appear at the top of the dovetail, as all we had was a tiny one and it took forever. This new one shiuld get it in a single pass.

 

Also bought another 5gal of Parks 50, upping my volume to 10 gallons of parks. Which the big block weighs 12# currently. I'm hoping that us closer to 10 once the dovetails are cut. I'm sure a half pound over isn't going to noticeably effect much. I am pretty set on a fast oil instead of water for this large cross section. I tested 3.5# 4140 hammers in my sword kiln recently and they turned out great. It will easily handle these.

[zombieresponder]

Tempering 4140 at 350F doesn't accomplish anything other than some slight stress relief....if it's held at temp long enough(2 hours per my Crucible books and every other source I've checked). Tempering at 450 will only knock maybe a point or two of rockwell C hardness off. Water is fine to use as a quench liquid for thicker sections of 4140. I would definitely add some dish soap to the water though, to keep it from boiling away from the steel surface as quickly. I can only recall doing heat treat/tempering on 4140 once....all other heat treating I've done has been on tool steels(A2/D2/H13/etc.).

 

If you are unsure about the taper, then verify that two sides are parallel. Clamp those sides in the vise, then use an indicator(dial test type) on the dovetailed surface to determine the amount of taper(if any) from end to end. Then repeat on the other side. Your machinist brother should understand what I'm getting at. The other way to measure external dovetails is with two pieces of round stock. I've seen people use drills(same size), but precision ground shaft or drill blanks are much better. Put the round stock in the "v" on each side and measure over it.  A little bit of right angle trig will give you the actual measurements with this method. The same method works in reverse for measuring internal dovetails, though it's easier to use an adjustable parallel and then measure the parallel after removing it. Cock the mill head over for one angle and shim it in the vise to achieve the second angle(if required). I'd use a sine bar + indicator to set the mill head and an accurate protractor to set the angle in the vise.

[DanielC]

Came back to this project. Cut the second angle in. Next while the bottom die dovetails are being cut, I will cut out two chinks out of the face of the die, and use a rotary table to mill it into a cylinder.

[DanielC]

Using an indicator on the bottom die, it is showing basically zero taper on either side. Instead of the 1/8th inch per foot. Why is this? My dies look like factory made California drawing dies. 

 

I read on little giants site that the older models had straight dovetails and the newer ones with removable sow blocks had the 1/8th inch per foot. My Murray doesn't have a removable sow block.

 

I guess right now I am going to give it a straight dovetail.

[DanielC]

Though looking back, I did measure the female dovetails, and there is a taper there. Just not on this seemingly factory dovetail.

[Richard Furrer]

As all these tools are older in manufacture and specs change over time it is always a good idea to measure the very one you are making the tool for and not depend upon the factory specs.

Have a look at FX2 steel for dies..I have some on my 3B Nazel and they are only now showing wear. They can be machined "as delivered" from Finkl Steel with carbide cutters and need no heat treatment after. They offer several other steel in hardened, but millable condition. FX2 is the only one I have used, but others seem good as well.

Just a thought.

 

Ric

 

[DanielC]

Thanks Ric.

I am milling the die like the one previously used, like you suggest.

I have a source to some H13 this size I can use from a friend, but will give fx2 some thought. It may be a thought for the 4b I am in the middle of purchasing though, as the H13 will not be big enough.

[DanielC]

Ok so talked to the owner of little giant, and his ans for Murray and as indicated by my machine, that a Murray hammer has taper in tje female dovetails on the machine, but the dies are straight.

 

I originally had my top die correct for my machine.

 

LG's have a 2 degree taper, but my murray has a 1 degree taper.

 

My top die that i milled the 2nd taper in as per instruction here can still work for my machine with a custom key, that they are also willing to make.

[BIGGUNDOCTOR]

I would leave a radius at the top of the dovetail on the die to prevent possible cracking during quenching, Sharp inside corners are stress risers.

 

[DanielC]

Of course, planned on it.

[DanielC]

The dies came annealed. After all the machine work i normalized 3x at 1650F, and then hardened at 1550F in 10 gallons of Parks 50 which was at 75F.

 

I am not overly concerned if the main body wasnt as hard as the face of the die. Since its roughly the same diameter as many of my 4140 hand hammers thats are hardened in Parks, i knew it would take on full hardness.

 

Now for final fitting of the key.

[DanielC]

Testing everything out. Works better than i had hoped. Die fits tight. Keys fit rather well.