Reason of twisting under PH

[Gergely]

Hello,

It may be a very basic problem, but I've not been able to figure it out:

When I draw square points or chisel points on the power hammer, sometimes a sort of twisting occurs in the stock. It's like this, seeing from front view:

I can't determine the reason of this occuring, and so I can't avoid or correct it. I just have to take the stock to the anvil and correct it by hand, which is not too effective.

Can someone please enlighten me what causes this deformation and maybe the way to correct it? (My dies are parallel, and this happens only in some cases, so I think it has to do with my positioning.)

Thank you very much for your help. Bests:

Gergely

[Frosty]

It's twisting in your hand, OR the top die on your hammer has a bit of side lash in it. Meaning the top die has a little side movement on impact.

My bet is operator control, we all did that to steel even hand hammering, especially early on.

Frosty The Lucky.

[bigfootnampa]

Several causes are possible.  You may be feeding the stock into the dies at an angle.  Sometimes I have observed my stock twisting instead of drawing down when I am hitting the narrower side of the taper... usually near the small end of the taper.  You might be twisting the taper as you forge it... it is easy to do this purposely... just as easy by accident!  You may be able to correct it by feeding your stock at an opposite angle to the dies.  If caught early enough you can correct it by forging in your corners... back to round, then starting off square again.  You can also twist your stock slightly in the opposite direction as you forge, unwinding the accidental twist.  

[Gergely]

10 hours ago, Frosty said:

My bet is operator control, we all did that to steel even hand hammering, especially early on.

Frosty The Lucky.

Hi and thank you, Frosty! You're right, it has to be the operator control, because it mostly happens when I'm getting tired. 

 

5 hours ago, bigfootnampa said:

Several causes are possible.  You may be feeding the stock into the dies at an angle.  Sometimes I have observed my stock twisting instead of drawing down when I am hitting the narrower side of the taper... usually near the small end of the taper.  You might be twisting the taper as you forge it... it is easy to do this purposely... just as easy by accident!  You may be able to correct it by feeding your stock at an opposite angle to the dies.  If caught early enough you can correct it by forging in your corners... back to round, then starting off square again.  You can also twist your stock slightly in the opposite direction as you forge, unwinding the accidental twist.  

Thank you Bigfoot! I go and test it tomorrow. Feeding stock at an angle is indeed a problem I notice and correct all the time - cases when it's left unnoticed can be the cases when my twistings happen. Also giving a try to the correction method with opposite angle.

Bests:

Gergely

[Judson Yaggy]

Is this happening with your new Beche?  Hope you are loving it!  I find that small errors in hand control are quickly multiplied by die misalignment or tup (ram) lateral movement upon impact.  

Try filming a close up of the work and dies in action from an angle slightly different than your point of view.   Use common photo editors to slow down the action if you can.  Watching a video of yourself working can be very insightful.  

[Alan Evans]

What is your eye sight like? Get them checked.

Do you wear glasses? Try single magnification rather than varifocals. Maybe get a new prescription.

What light do you have at the hammer? Ensure it is even sided and well lit.

What profile tools are you using?

What action do you employ?

Toby Hickman always uses a 90˚ twist back and forth with every blow...I could only do that on small bars/tapers, and even then sometimes managed to get it going lozenge or twisted. So I usually run along the entire taper in one plane and then rotate 90˚ and run the entire length again.

I push in (thin to thick) if I am working with flat pallets and pull out (thick to thin) if I am using fullers.

With a heavy bar long taper...if the tools are not well matched...or if you do not hold the workpiece at the correct height...and if you do not do a 180˚ rotation so that the bar is kept straight, a banana shape overhanging the bottom pallet can cause a progressive twist unless you have a good porter bar or Tee bar to counteract it.

Practice...try deliberate twisting it to the right or to the left and note the results...

Alan

[Gergely]

So, I tested the feeding at angle theory in this morning. It worked. Not only the twisting occured but I was able to fix it. Well, to diminish my enthusiasm I have to say that this was only a short test run with a 16mm / 5/8" square 150 mm/6" long taper. 

5 hours ago, Judson Yaggy said:

Is this happening with your new Beche?  Hope you are loving it!  I find that small errors in hand control are quickly multiplied by die misalignment or tup (ram) lateral movement upon impact.  

Try filming a close up of the work and dies in action from an angle slightly different than your point of view.   Use common photo editors to slow down the action if you can.  Watching a video of yourself working can be very insightful.  

Unfortunately the Beche is still in the dry-dock. I haven't got any time to work on it, hopefully in Jan. It's so frustrating to see it every time and just not touch it at all.

I work on my Hungarian Ajax type 30kg/66 pounds springhammer. 

Thanks for the filming idea! I give it a try.

 

5 hours ago, Alan Evans said:

What is your eye sight like? Get them checked.

Do you wear glasses? Try single magnification rather than varifocals. Maybe get a new prescription.

What light do you have at the hammer? Ensure it is even sided and well lit.

What profile tools are you using?

What action do you employ?

Toby Hickman always uses a 90˚ twist back and forth with every blow...I could only do that on small bars/tapers, and even then sometimes managed to get it going lozenge or twisted. So I usually run along the entire taper in one plane and then rotate 90˚ and run the entire length again.

I push in (thin to thick) if I am working with flat pallets and pull out (thick to thin) if I am using fullers.

With a heavy bar long taper...if the tools are not well matched...or if you do not hold the workpiece at the correct height...and if you do not do a 180˚ rotation so that the bar is kept straight, a banana shape overhanging the bottom pallet can cause a progressive twist unless you have a good porter bar or Tee bar to counteract it.

Practice...try deliberate twisting it to the right or to the left and note the results...

Alan

I'm nearsighted with pretty strong lenses. The glasses are good, my eyes don't  

Lighting is an issue indeed. The hammer is lit only from one side. I have had problems with lighting for a while now, I have to reconfigure its concept in the whole shop - welding is a PITA because of the lights, too.

For basic point-drawing I use the flat dies. I mostly pull out the stock. I go with the "pull one side through then turn 90˚ or 180˚ and pull" method. (I tried to turn with every blow, but this hammer is too fast for me to do so.)

Can you please tell more about the "good porter bar or Tee bar" or maybe add a picture?

The tought you wrote about the banana shaped and twisted bar made me think: I may leave the curve unstraightened sometimes and I bet it can cause twisting, too. But that's a whole other case.

 

Thank you and bests:

Gergely

[bigfootnampa]

Aha!  Now that you have uncovered both cause and correction you'll make it look easy!  The best masters make plenty of mistakes... but often correct them so quickly and effectively that few observers notice!

[Glenn]

Consider the brightness difference between the hot metal and the hammer dies. Try putting a strong light with reflector on both sides of the hammer dies. Connect them to independent positionable light stands or stationary from the ceiling. For ideas, you may want to visit a hospital or dentist office and look at the multiple joint swing arms they use for adjusting their lighting. Several joints involved but the result is exact placement of the lighting on the subject.

Welding a short bar to the stock at 90* may help in referencing the stock in the hammer. This way you can visually tell if the stock is at the same angle and not rotated. It can also be used as a handle if needed. 

 

For welding:

A strong portable and positionable light on the welding table helps, They can be mounted on a swing arm floor stand. Try a 150 watt spot light or even a 500 watt shop type light aimed at the work area. Depending on the shade of the welding lens this sometimes helps a lot. If you do a lot of welding, you may want to try a lighter shade lens, or an auto-darkening lens. 

Another consideration is the color or reflectivity of the shop walls. Bounce lighting from the arc may be getting under and/or into the hood

[Alan Evans]

Here are a few porter bars...as usual many of them made mid heat in a panic to counter a particular problem!

As Glenn mentioned the rotation control bar / tell tale can just be a welded piece. I have often just bent the handle end of the workpiece at right angles to act as a rotation indicator. It all depends on the circumstances of the job.

The banana problem is often encountered when forging from a bit of round stock. With square and flat you obviously always have a better control of rotation.

Alan

[Gergely]

On December 19, 2016 at 4:11 AM, bigfootnampa said:

Aha!  Now that you have uncovered both cause and correction you'll make it look easy!  

 We'll see that next time when it happens working on an actual piece. But sure I can practice for that now.

 

On December 19, 2016 at 8:32 AM, Glenn said:

Consider the brightness difference between the hot metal and the hammer dies. Try putting a strong light with reflector on both sides of the hammer dies.

Thank you for your great suggestions, Glenn!

One more thing came to mind besides the lightning: the floor is uneven in front of my PH, and maybe it can also effect my position. I think if my feet try to reach for a stable place instead of the perfect one for the work, it's not the best.

 

On December 19, 2016 at 9:05 AM, Alan Evans said:

Here are a few porter bars...as usual many of them made mid heat in a panic to counter a particular problem!

As Glenn mentioned the rotation control bar / tell tale can just be a welded piece. I have often just bent the handle end of the workpiece at right angles to act as a rotation indicator. It all depends on the circumstances of the job.

Thank you for the pics, Alan! Those got me thinking if these old threader "wrenches" would be good for the same? After modifying the threader dies first. (I now use these for twisting bigger stock. Again, with modifeid dies in them.)

 

Thanks and bests:

Gergely

[BeaverNZ]

Ive read this with great interest thankyou for the premeptive info cheers

[Smoggy]

I found it very interesting and informative too, no idea when I will ever get a chance to use a power hammer, but so much here applies to other processes and machines.

Fundamentally basic stuff but so easy to overlook to our detriment.

[Frosty]

In my initial reply I said we've all been there, bending or twisting stock under the hammer. It takes practice to learn to turn 90* even though our wrists will index 90* naturally. It still takes practice. We also tend to have a learning curve to get the stock laid flat on the anvil while we hammer. The natural tendency is to lift a little too high and cause an upwards curve. This is true under a power hammer, hydrauic press, rail car coupler or a Chinese ASO.

This is why we're seeing so many ways to control or compensate for a twist or curve, everything from practice and keep track of what happens till you get it right to some darned clever tools. It's what the free exchange of information is all about.

Frosty The Lucky.

[Gergely]

Hi and thanks for all the input!

Yesterday I experimented with some spring steel. Was shaping an L from a 4"x3"x7/8" piece. While forming the stem it twisted real nice. I saw it coming just couldn't get any better control, also the shortness of the workpiece made hard to see good alignment. From the same reason the opposite angle correction wasn't possible. Still managed to get it right as I had plenty of mass to deal with: simply forged in the twisted corner lines, and re-established the square cross section. I was pretty happy until I totally messed up punching a hole in it  

I thought I report in. (Also found a tap wrench like the one in the middle of Alan's picture.)

Bests to all:

Gergely