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  #11  
Old 01-19-2017, 09:53 PM
Essexmetal Essexmetal is offline
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Die changes are not instantaneous and there is a reason for having a double headed hammer. Leave the shrink set up on the one side and the stretch dies on the other.

The key is once you have run in each set of dies is to store it with all the shims and wedges. This speeds the change over. A fresh from scratch set up might max out at 1/2 an hour, run them in, do an adjust etc. The trick to checking the hit is to oil up a piece of linen and hammer on it to check the hit is square and centered. If you have any threads still connected you move the die until you get a clean cut that reflects the shape of the die contact area.

Just two cents worth here.... every method of die retention has been tried. Bore and pin, set screws into a lug, set screws into the dove tail, set screws against a gib that presses against the dovetail. Nothing works as well as the shims and tapered wedge. There is a huge amount of force and vibration and a tapered wedge is the best at sucking up these forces and keeping the die tight. You don't need to change dies that often. In general a stretch set with around a 1" hit , blow, contact, what ever you want to call it, will do a large variety of work for you. You may need to switch to linear stretch dies, etc and that's when start getting better and setting up a machine. The only exception of an original hammer that I know of that did not use the shim and wedge method was the Beatty Quickwork. It did have set screws and a gib. Instead of raising the die block with plywood or leather shims like Pettingell or Yoder's the Quickwork used a monster acme screw. There may be other methods with hammers but those were the most common.
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  #12  
Old 01-21-2017, 05:47 PM
John Buchtenkirch John Buchtenkirch is offline
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Originally Posted by Gareth Davies View Post
Thanks for the reply John. Obviously, it's not my thread but, I agree, it's in the wrong section.

Out of interest, what sort of thickness would the dovetail keys be? I'm guessing at around 3/16" to 1/4" but it'd be nice to know for sure.

I understand what you are saying about die height and that makes perfect sense. I've done a bit of scaling on other people's photos and it looks like the 3" dies sit at about 2.1/2" high and the 2.1/4" dies at around 1.3/4" height. Just estimations on my part but those proportions look about right to me.
You need several thicknesses of tapered die keys because when you shim your hammer dies closer & closer together you need thinner & thinner die keys. I have a rag tag collection of hammer dies Iíve picked up thru the years so my dies are several different heights. So to be totally honest I donít even know if thereís a definitive answer to your question on die heights. Iíve been able to make what I have work for me by changing the distance between dies but the down side to that is it can be time consuming. ~ John Buchtenkirch
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  #13  
Old 01-23-2017, 09:20 PM
John Buchtenkirch John Buchtenkirch is offline
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Originally Posted by crystallographic View Post
The "hammermen" I have asked (Leo Berger, Jack Hagemann, etc) about this all said, "about 6 hours."
Iíd say if it took them 6 hours they were probably talking about putting a new die in the hammer where they had to spend time dressing the face to get the hit point correct. Unlike Pullmaxes and CP planishing hammers very few power hammers had their arms true to each other so then instead of having a round radially stretching hit point you ended up with a quarter moon hit point over to one side that stretches mostly directionally. Depending on how bad the hit point was could cause it to take quite a bit of time to correct. Also they might have had to change the shim pack under the anvil to raise or lower the die, not really a big deal but still more time in setup. No one said hammer work was easy . ~ John Buchtenkirch
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  #14  
Old 10-04-2017, 11:26 AM
jmcglynn jmcglynn is offline
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Hmm, I know this is an old thread but wanted to comment here.

The comments about shimming and time required for changing dies seem off to me. If a machine is set up properly with a matched set of dies (all at the same working height) then the die change should be very quick I'd think. Less than a minute, just as long as it takes to drive the wedge out and back in, with a check to make sure the dies are aligned.

If they dies have slightly different working heights, then shimming or even changing the height of the anvil block would be necessary. If the arms or die travel isn't exactly square then you have a problem getting a clean contact patch (and yeah, that would be a big pain in the butt to change dies then).

FWIW, at Fay's class he changes dies just that quickly. Yeah, he's Fay, but I'd bet he has his machines dialed in to make that possible.
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  #15  
Old 10-04-2017, 12:01 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by jmcglynn View Post
Hmm, I know this is an old thread but wanted to comment here.

The comments about shimming and time required for changing dies seem off to me. If a machine is set up properly with a matched set of dies (all at the same working height) then the die change should be very quick I'd think. Less than a minute, just as long as it takes to drive the wedge out and back in, with a check to make sure the dies are aligned.

If they dies have slightly different working heights, then shimming or even changing the height of the anvil block would be necessary. If the arms or die travel isn't exactly square then you have a problem getting a clean contact patch (and yeah, that would be a big pain in the butt to change dies then).

FWIW, at Fay's class he changes dies just that quickly. Yeah, he's Fay, but I'd bet he has his machines dialed in to make that possible.

I'd just guess that if a craftsman were changing his dies all the time in the same machine he'd Have to get pretty fast at it.

Otherwise, if the dies get changed once every 6 months or every year, then it Might take him longer .... (Quinn Epperle)

Also, if the ways are nice and tight, die-change might be quicker than if the ways are loose (Red Tweit).
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  #16  
Old 10-04-2017, 01:34 PM
John Buchtenkirch John Buchtenkirch is offline
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Many power hammers do not hit true, meaning unlike Pullmaxes and CP planishing hammers the centerline of the ram may not be truly square to the lower die. The mounting pads (where the upper arm bolts to the pedestal) on both my Pettingells isnít even a machined surface so how good could they be, I donít know about Yoder. If you are installing new dies in your hammer they may need tuning / surfaces polished down to get the hit point correct and that can take time. Also dovetails donít have a standard size so you might have to shim them or have different thickness keys to lock them in if you have dies from several sources. Having said that if your die is tuned for your hammer and you keep a correct key with it you could change dies in under 5 minutes including some time to check your hit point. ~ John Buchtenkirch
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  #17  
Old 10-05-2017, 11:53 AM
jmcglynn jmcglynn is offline
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John, Kent, thanks - that makes sense.
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