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Posted

Been looking at YT at taper technique, and all say to start from the point and work back. But a 'long' taper on these videos is something like 4". I have a need to make a 30" continuous taper, eventually finishing as round, ending in a leaf. I threw it into CAD to get the numbers and it comes out to about 3/32" of a taper per foot. Suggestions for order of operations would be appreciated.
 

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Posted

This is how i would go about it.

Use a starting stock in the size you wish to finish the large end of the taper. Isolate the finial portion. Neck down the taper to the size you wish behind the finial end. The start will taper with a much more aggressive angle than your 3/32" a foot. Then slowly start decreasing the angle back till you get to your finished size paying attention along the way to any lumps and bumps keeping it nice and smooth. Just short of finished length then round it up. Rounding the square will push out a smidge more length. There will really be no need to check the O/D along the way, that should naturally come out as you taper. The finial can be made at any time you wish after isolating. 

The hardest part is going to be your starting length. So i would make a couple test pieces. For a 30" finished length i would first try 15" And adjust from there. IIRC, my notes are out in the shop, when i do fire pokers i start with a 24" piece of 1" x 1/4" flat, and after tapering they end up at 36". Just make sure that when you get done to write that down so next time the guess work is already done. But that is isolating 2 1/2" for the business end and about 4" for the handle end. 

Also keep those test pieces along with your notes making them. Never know one day you may want the same design in a different length or a customer. 

Anyway that is how i would do it, others may do it differently and hopefully they will chime in. Like they say, more than one way to skin a cat. 

Posted
3 hours ago, BillyBones said:

The start will taper with a much more aggressive angle than your 3/32" a foot.

I'm not understanding this statement.  Can you explain?

FYI, I plan to start with 1/2" square bar, since squaring the round stock would be the first step anyway.

Posted

If I've interpreted Billy's instructions correctly (and I think I have), he means isolate your finial section by fullering/butchering in behind it and  create a "short" steep taper from that now smaller fullered section (eg 3/32" in 1"), getting larger as you get further from the finial section, back up to starting stock size. Then lengthen the taper by forging where the edge of that first taper gets back to the starting stock size. This will lengthen the taper to, say, 3/32" in 2". Each time you do this, you blend it into the existing taper to create a shallower angle each time you move back along the bar. If you fuller in to the correct size behind the finial at the start, and you're always tapering back to starting stock size, the only limit is your ability to evenly draw 30" between those dimensions.

I hope that helps. I know it's always harder to communicate these things purely with words. 

Cheers, 

Jono.

Posted

Another way to do this is to calculate how large the taper is supposed to be at various lengths from the starting point and work on each section to that size.  For example, if the taper is supposed to be 3/32 per foot then at 1 foot from the starting point if you are starting with 1" x 1" stock the tapered size will be 29/32.  Make a sheet metal gauge with a 29/32 notch and keep fitting it at the 1 foot mark until you get the right size.  Do the same for 26/32 (13/16ths) at the 2 foot mark.  Rinse and repeat until you get the length and size you want.

Alternatively, you can do it by length.  if you calculate that you want a taper going from 1" to 1/2" over, say, a 3 foot length, calculate how much steel would be in that shape and calculate how long the equivalent, untampered stock would have the same volume.  For example, if you want a 3 foot (36") length you can calculate that you may need a starting length of 30.5". (Not a calculated amount I'm just SWAGing it for illustration).  Then Isolate your ends and start drawing out until you have a 36" length.  You can keep the taper even by eyeballing it.

"By hammer and hand all arts do stand."

Posted

A couple of thoughts on this.  First, if you want to calculate the amount of material required, you can use the formula for the volume of a four-sided pyramid:  L X W X H / 3.  If you continued your taper to a point, it would be 60" long.  1/2 X 1/2 X 60 / 3 gives 5 sq inches.  The part you aren't making is 1/4" at the base and 30" long, which gives .625 square inches.  Subtracting gives you 4.375 square inches, or 17.5" of 1/2" square.  Of course, that doesn't account for scale losses or for rounding up, so you need to allow a little windage.

To forge it out, I'd probably start by drawing steps.  First, I'd mark off the stock you need for the taper, maybe 18" or 19".  Then I'd make Billy's fuller at the mark at what will be the small end of the taper, and also make his short taper to avoid any possible cold shuts.  

Now, your final taper will get 1/16" narrower every 7-1/2".  I'd make four stepped sections each maybe 7" long -- the idea it to allow some for the growth when you make the final taper, but also leave a little extra stock to work with.  Starting from the big end, I'd mark off a 7" section to leave at 1/2" square, then draw out the rest of the piece (except the leaf, of course) to 7/16.  I'd then mark a point 14" from the big end and draw the remainder to 3/8, then 21" and 5/16.  Your 5/16 section probably will come out short, so borrow a little from the 3/8 section, and adjust the other two sections accordingly.

At that point, you'll have the metal largely in the right place, and you can forge the final taper by eye.  (Mathematically, the thinner sections will grow a little more percentage-wise when you make the final taper, so you could start with a 7" section at the big end, then maybe 6-3/4", 6-1/2",  and so on.  But ultimately you're forging and judging by eye anyway.)   

 

 

Posted

Forget about all the numbers, ratios, etc. you watch and hear on Utube, trying to make it come out 3/32": 1', will make you crazy. The blacksmith's craft isn't about numbers, it's about the product, your eye, ears and hands. 

You know your minimum and maximum dia. and length. The ONLY other thing you need to know is where to start and the "SECRET":ph34r: Stop when it's right. PERIOD.

First forge the leaf, if you do the leaf AFTER it's necked to minimum dia. it WILL break off. 

Set the area behind the leaf to CLOSE to finish dia. leave some thickness or it WILL break off. Remember, every time you take it out of the fire you WILL lose thickness to scale so leave plenty, 16" at least.

Actually your best chance of keeping the leaf from breaking off while forging the stem is to weld a leaf to the end afterwards.

Trying to calculate how much stock to use is often a good way for a beginner to plan a failure. I stopped in all but special circumstances a long time ago.

Here's how I'd forge that taper. Draw the end to about 3/8" sq. The extra 1/8" should be plenty to account for scale loss. You can draw everything to the desired dimension when you finish/texture/etc. the finished stem.

Then draw the transition point between the taper and the stock, when this section meets the point STOP.

Remember and this is IMPORTANT!:angry: Hold your hand the SAME HEIGHT above the anvil till the steel is too cold to forge each step! The natural tendency for people is to lift their hands higher as they forge long stock it's a habit well worth the effort of breaking.

Next, lean it back on the transition point and again forge it till it meets the point and STOP.

Repeat until it's 30" long and STOP.

The last step if you wish a smooth piece is to dress the faces with a flatter at black heat. You don't want to do any "forging" you're only smoothing the roughness off by driving the high spots even with the taper.

With the number of heats you take the tip will have lost thickness if you can work fast enough it should be within reason of your 1/4" desired finish dimension, a little file work isn't unexpected and is a perfectly Blacksmitherly practice.

I'd start with maybe 36" so I had plenty to hold without getting burned. The bar will lengthen considerably as you taper it which makes measuring it by section ahead of time counter productive. Remember this is an exercise in solid geometry, smithing is ABOUT solid geometry. A 1" piece of 1/2" square drawn to 1/4" WILL be 4" long. There are formula for calculating how much stock makes how much taper but that's more for production shops than hobby smiths. 

This is easier and faster to DO than describe let alone explain. 

Frosty The Lucky.

 

Posted

I like Frosty's way.   It's too early and I haven't had enough coffee, or the evening equivalent, to do that much math.  There are all kinds of smiths,  some love the math and design, some like to just grab a hammer and go.   I think I see both of them represented here.   

 

Posted

Are these going to be a production run?  Or just a one off?  I know it maybe against the spirit of forging,  but a lathe may be an option.  You'd certainly get that taper to your specs, if those are the most crucial aspect of the project.   And you'd still have to forge the leaf, so it wouldn't be a totally machined piece.

Posted

Forget turning on a lathe.  It would be quite slow and due to the length and the 1/4" final size it would be flexing between centers.  Since your desired piece will be round when finished, start with apiece of 1/2" round long enough that it will serve as your handle as well.  If you want to be a purist, leave a small bit at the end untouched to forge later into the leaf shape, or not and plan on welding the leaf on when done which would be easier.  Guesstimate where you will need to begin hammering and work the piece square, tapering as you go.  As the piece grows in length you will get an idea of where you need to begin the taper to end up with the desired length.  Don't worry if you end up forging it smaller than 1/4" at the small end as you can cut that off.  Be mindful of the tendency for the piece to go parallelogram and work the long corners back to square.  Once you have something of the desired size, work the corners to create an octagon and once that is made, work the edges to make it more round in a swage block if you have one.  If the hammer marks are acceptable you are done with the taper and then weld the leaf shape on by whatever welding method you have available.  If you want it smooth you could spin it against a belt grinder but realize it is easy to create divots in the piece.  Have fun!

Posted
On 11/4/2024 at 9:51 AM, ShoreB said:

Are these going to be a production run?  Or just a one off?  I know it maybe against the spirit of forging,  but a lathe may be an option.  You'd certainly get that taper to your specs, if those are the most crucial aspect of the project.   And you'd still have to forge the leaf, so it wouldn't be a totally machined piece.

These will be a one-off.  Trust me, if I had a lathe, this would already be a done deal.  

Thank you to everyone that's replied.  It's interesting to see the two camps, the "Do the math" guys and the "Grab a hammer and smack it until it's right" guys.  I appreciate the math involved in this work, but rarely has it ever worked out correctly for me, which is entirely due to my own mistakes, I'm sure.

Here's my plan: I don't have access to a lathe, but I DO have access to a milling machine.  And a hydraulic forge press.  The press jaws are 3" deep and are obviously parallel.  I re-drew my original CAD drawing with 3" long steps, each step reducing in height by the distance required to stay within the taper outline.  I measured the height of each step every 3" and will mill a pair of spacers to constrain the press to that thickness.  Hopefully, when I'm done I'll have something approaching this drawing.  I'll then go back and smooth out the steps.  

Should this not work, I'll be attempting the BillyBones/Hefty approach, as I finally understand it (after reading it several times).

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  • 2 weeks later...
Posted

Watch this video for an excellent tutorial on forging.  While he does not do a taper, the same hammer technique is applicable.  

I think you are thinking to hard about your project.  Seriously, your using four digits to spec out your piece!  Do you realize how small .0003" is?  These kinds of tolerances are for serious high precision tools or scientific instruments.  Get your hammer, anvil and forge and start having fun with it.

Posted

Oh come ON Gazz you DON'T forge to a ten thousandth? :o Oh man, sloppy sloppy sloppy, I'll bet you don't even do ex-ray spectroscopy on road kill steel either! I'm shocked, SHOCKED I say!

Frosty The Lucky.

Posted

I've gotten folks at the scrapyard to use their XRF gun on different bits of scrap, often with very pleasing results (e.g., the crate of 2" dia. x 36" long round bars that turned out to be 4140). Alas, the place where I first did this is now completely gone, and the second is now closed to the public. I'm afraid to try a third.

Posted

To give a bit of perspective on how big .0003" is, a sheet of notebook paper is ~.003"-.005", or approximately 10-15X thicker than .0003". 

My job is a machinist, i am the tool maker in the shop i work. I work with tolerances of +/- .00025", sometimes less, all day everyday. It can be tricky holding that with precision machinery much less by hand with a hammer.     

Posted

I hear you, my Father was a metal spinner and machinist when the most automatic was the feeds and instrumentation was vernier scale, calipers or mic. He did a lot of aerospace work and the tolerances were insane. I don't recall the lunar probe that had nested spheres that after soft landing opened to expose the instruments which remained in the same position as on the launch pad. The annulus between the spun sphere sections was to be one molecule of whale oil. 

While I grew up running a lathe and spinning I don't consider myself either, holding a 0.001 is all I've ever needed. Thinking back on working with Dad in his shop as a kid I'm frankly glad OSHA ran me out when his operation became large enough to draw their attention. He paid a big price for the amount and level work he did and not a CNC anything anywhere. Spinning really beat him up, all the ribs on his right side were fused together from holding the scissor tool. 

Frosty The Lucky.

Posted

I still use scale, calipers, and mics that are not digital. Same as the ones that your dad would have used. I do have digital gauges that read down 6 digits, .000005" i use and then we have a laser gauge that is insanely accurate, but also measures all dimensions of a part at one time. 

Before i became the tool maker i ran a Davenport 5 spindle screw machine. No CNC all the adjustments made by turning a bolt against a dead stop. What is kind of funny i have found is that the guys running the CNCs do a lot more work that the guys in the screw machine department. If i am slow in the tool room sometimes i will come out on the floor and run a machine. In the CNC department almost every single part needs back work or 100% inspected on a dimension or 2. (back work is things like deburring) While in the screw machine department once the machine is making good parts, 5 or 10 in a row, you sit down and watch it run for 1/2 hour or so then check some parts. 

On a side note i had a fun one today. Just simply drill a hole, ream it, and tap it for a 1/8 NPT fitting. The hole was 5/8" deep. Drilled into a 1" coolant through drill. It had a small hole all the way through the drill that i was able to use as a pilot. But it was still hardened steel and took me almost 4 hours to cut, ream, and tap. 

Posted

When I told Dad I'd bought a lathe he gave me all the instrumentation he still had, 95% of which I have no use for. Worse I've offered it for sale, even in local machine shops and a high school and nobody has use for anything that isn't digital. Even instructors can't read a vernier scale. I'll probably have to make a mantel or desk decoration out of my 24" Starrett height gage, caliper and or mic. 

I bought a $9.95 digital caliper in a "closeout" tool store as a throw away in the shop and I was really surprised when I checked it against Dad's jo blocks. The darned thing is or was accurate to 5 decimals. So, I put the jo blocks in the fridge and then on a shelf behind the wood stove, about 60f difference and darned if they weren't accurate on the COE chart.

I pulled the COE table up online I didn't look it up in the COE book I got from Dad, that one goes into alloys and humidity. I have NO idea what humidity would have to do with almost any metal's COE but Dad had the tables. I wouldn't be surprised if there is a barometric correction table in them somewhere.

While I really like CNC for repetitive mass production, screw machines are more efficient in setup and breakdown in many cases but you can email CNC around the world insert the memory stick, chuck up the stock and turn it on. 

On the other hand by time an IT can read the print or upload the cad and write the program a screw machine would be in production. 

It's like our Dodge Journey, we've had an intermittent problem with the headlights for some time and our turn finally came up at a local auto shop. Forget the dealer! After close to an hour reading codes and doing tests on the onboard computer block it showed nothing. However the mechanic solved the problem by physically testing the sensor on the dashboard that automatically turns the lights on and operates the high beams. 

Alaska is a headlights on if you're on the road state so having the stupid car decide to turn them off if the sun's out doesn't work. Sooooo, I keep the sensor covered. The computer block used to have a setting for always on headlights but an upgrade removed the option. Yeah, the CAR is online and updates without notice.

The world's changing all the time, change is the ONLY constant. <sigh>

Frosty The Lucky.

 

Posted

When i was rebuilding transmissions i bought a cheap set of mics that were the old school digital, not electronic with the rolling numbers cant remember what that is called. They only measured out 3 points.  Some of the parts like certain washers had to be measured. But the choice of washer would be like one is .125" thick and the other .200" thick. You could pretty much eye ball it so i was not looking for accuracy in them. I took them to work just to use as reference but they still had to be tagged into the system. Me and the head quality guy were both surprised just how accurate they were. They now reside next to my drill press so i can find drills out of the pile that i never organize. 

Industry standard is now mostly digital. I can not blame them though. I have had to teach basic algebra and geometry to so many kids i have tried to train it is not even funny. I could not imagine having to also teach them to read mics as well... but i digress. Most machinist anymore do not even own mics and calipers. The company owns them. But like our GM said if the mics are out of calibration it is not the fault of the machinist now. So it is kind of a good idea. 

 

Posted

I tend to agree digital is better, reading a vernier scale can require interpretation and no two people do it the same. 

I used to give guys a few hours of introduction to smithing and in the past 10 years I've been running into young people who couldn't do basic math. One not only couldn't find the area of a square he didn't know what area meant. 

A friend taught middle school for a while a couple years ago and even arithmetic involved estimating rather than adding, subtracting, multiplication or division. Plane geometry was a game of drawing on graph paper and counting the squares. 

At least I know how my Father felt when he said kids "today" aren't learning anything useful in school. I already knew multiplication and division when the Cal. school system implemented the "new math" and it's only getting worse.

Frosty The Lucky.

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