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What edge radius on flat dies do you prefer?


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Picked up my c41-40kg hammer and am up and running now (had problems with a huanyang VFD that would trip at 6.5 amps; now got a TECO). The edges on the flat dies came sharp so I radiused them at about 1/32" or so to start but was wondering what everyone here prefers.

 

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I radiused the new dies for my LG wider than that, maybe 1/8"r on one side and 1/4"r at 90* but I'm in favor of starting too sharp and widening them as you go. I'd have to do a LOT of grinding if I decided 1/8"r as too much.

Frosty The Lucky.

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As stated by HWooldridge above, cold shuts are the hazard, avoiding 90degree edged steps in the workpiece is the goal. If the steps in the workpiece come halfway up the curve of your radius then the edges will be less than 45degrees and will forge in easily. 

Remember that the hammer generates the most energy when the pallets meet and very little at the top of the stroke. The heaviest blow will be when you are on the thin end of a taper. But you will have backed off the treadle...

Each hammer weight requires different radii given a similar workpiece. I have a larger radius on the pallets of my 3cwt hammer than on the 1cwt.

So the time to look for your 40kg hammer is when you have it going flat out on say, a bit of very hot 20-25mm (3/4" - 1") especially if it is a bit of flat on edge.

If you start with a small radius and increase if you find you are still generating cold shuts.

As I become familiar with a  hammer and any given process I find I can hit harder with out fear of going to far, but with even heavy tapers you want to just make a lot of narrow steps rather than a few big ones. 

Alan

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I'm no expert, but I run about a 1/8" radius on mine. The next set that I make I will probably do a 1/4" radius on though. Also, your hammer is fantastic, and one day I wish to get an 2 piece 88 or a 1B. It looks great in the blue/black. Congrats on getting it!

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It is all a bit of a compromise, but you definitely don't want sharp edges for direct forging. You can always use an drop on block, a top set or pair of spring tools etc. if you need to dress a shoulder square.

The only negative thing about the edge radius There are some occasions where too much radius can cause the metal to spit back at you when taking a little bite on the end of a taper a bit like the  action of the tiddlywink disks we flipped as children. But just like tiddlywinks it is a function of weight of blow and position of workpiece to control it.

Alan

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I have very light crowning on my main 50kg hammer (4mm rad) and recently went back to using my goliath spring hammer which is feathered  over an inch of the tooling to give a very gradual taper into the block. for my work on knives I can thin forge a blade with no visible tooling marks. great fro free forging, no use for tooling.

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The primary dies on my Massey  are just over 1/8" although I have worn them to 3/16 in the center.  You have to be careful not to get shuts but they work well for most things.  I have another set that I modified to a 3/8" radius which are good for heavy drawing and are far better for drawing steep tapers or shallow tapers that won't have a flatter or taper die used on them.  A lot of my work involves fairly sharp shoulders which is why the 1/8 dies are my primary dies.  As well I want the full width of the die for lots of things.  I would not want to use dies sharper than the 1/8" mine are on a day to day basis. 

Edited by JNewman
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