Air Power Hammer Class - tinmantech.com

[Tom Walter]

John -- It is pure magic, that is all there is to it.

I get the idea of shrinking metal. Got to do a lot of that in Kent's class. First three days are hand tools to get the basics down, before going near the air hammer. Kent showed up some great tricks on shrinking, and then off the air hammer.

I did some shrinking on the air hammer. Pretty cool.... but I didn't understand it until months later the light bulb sent off! It really is a magicians trick with everything in plain site, until you understand how much work went into those dies and technique. I'd made a UHME shrinking bowl. Well, that is a great way to wear out your arms! With a little pixie dust (from the sand blast cabinet, look I can shrink!). Friction is the key to shrinking, hence those mystery material dies.

I have no idea who "Leo" is on the previous links, but looks like he just collects other video's and post them up under his name. You'll find more of Kent's video's under his name.

Kent's youtube link is:
http://www.youtube.com/user/tinmantech/videos

The video on the 1100 aluminum is here:
http://www.youtube.com/watch?v=kgDggbr63ws



The biggest irony with my company loosing out "non-qualifying" health plan is next year deductible will be $6000 on surgery. So it is really cheaper to buy an air hammer and save my shoulders/elbow issues. I'm sure my wife will buy that!

[Irrational Metalworks]

The "mystery metal" that the shrinking dies are made from is magnesium. That's the secret to these dies working so well. I also own a couple of mag hammers that work real well for shaping. Something about mag that is resilient enough to keep from stretching your material, but hard enough not to deform the hammer or dies. I'm not a metallurgist, so that's the best description I can come up with! I bought one hammer years ago, and I don't remember where. The other I made from some billet I had.

[Maxakarudy]

Still being new around here, I think I've understood the principle of shrinking metal, ie the process of crushing metal into a smaller area making it thicker.
I can see how an Eckold and thumbnail dies work to achieve this, also tucking forks and stump shrinking.
However I can't see what's happening to Kent's dies that follow these principles, ok the metal doesn't stretch because the top die grips the metal and stops it spreading, but would it be considered as shrinking?, where are the shrinking marks, all of the above mentioned processes have them.
I consider it more of a 3 dimensional bending process from what I see in the videos.

[sblack]

If you watch the youtube videos of Wray Schelin shrinking with a mallet, he surrounds a ruffle with hammer blows to trap the metal or he can even do it in the middle of a panel using a concave stump. Then when it's trapped he pounds it down. That's what Kent is doing with the air hammer.

[weldtoride]

Originally Posted by Maxakarudy

However I can't see what's happening to Kent's dies that follow these principles, ok the metal doesn't stretch because the top die grips the metal and stops it spreading, but would it be considered as shrinking?

I purchased one of Kent's hammers many years ago for the high school shop I taught in, I mention this so that my answer bears credence. I also can only speak very highly of his hammer and his service to me as a vendor.

The operator uses a much different and a little more complex motion than the simple in-out-in-out of a thumbnail die.

Like several have mentioned above, an "aha" moment is necessary in the learning curve to shrink with Kent's hammer. Martin, as you mentioned above, the shrinking top die does grip the metal and stop it from spreading. What you are not seeing yet (your "aha" moment) is the tuck that has been put in there just before, but still using the same hammer and die, just a different what I described to my students as "wrist" technique.

In this video around 1:30 in and following, you can see the tucks being formed rather clearly: https://www.youtube.com/watch?v=zuLMI4hapEc for any readers on the fence about following the link, it's 14 g hot roll, try shrinking that with a "planishing" hammer.

This is how he forms tucks: close observation will reveal how he uses his wrist and arms to bend the the sheet down, watch the height of the rear sheet edge near his apron in relation to the die set, and you see how far. I found a subtle side bend was helpful as well.

Once a tuck is formed, he runs it in and there is your shrink.

It's not so hard really, I successfully taught my hs students his technique.

One of Kent's hammer kits is on my wishlist.

[crystallographic]

Originally Posted by Maxakarudy

Still being new around here, I think I've understood the principle of shrinking metal, ie the process of crushing metal into a smaller area making it thicker.
I can see how an Eckold and thumbnail dies work to achieve this, also tucking forks and stump shrinking.
However I can't see what's happening to Kent's dies that follow these principles, ok the metal doesn't stretch because the top die grips the metal and stops it spreading, but would it be considered as shrinking?, where are the shrinking marks, all of the above mentioned processes have them.
I consider it more of a 3 dimensional bending process from what I see in the videos.

I understand your concerns here, Martin, as the process shown is not quite graphically clear. I cannot demonstrate this particular shrinking process here any more clearly than I can show any of the other shrinking processes. So, perhaps some photos and some mathematics will help?
In the following photos you will see a flat ring of cut sheet aluminum, a bulge in the aluminum, the bulge "disappeared" and then a 3 dimensional aluminum ring. (We trust that the flat blank is indeed being shaped into the 3D ring, and that this is not surreptitious camera tricks.)

The mathematics of the ring are:
circumference of the blank: 127.0 inches
circumference of the finished ring: 85.25 inches
net change: 42.25 inches, or about a 30% loss of circumference, with the thickness of the aluminum going from .063" to .071" and the directional grain of the metal changing to omnidirectional.

Marks? Well, they can be added in if you really need them but my process leaves the metal fairly smooth. Most folks like smooth metal, however it seems that not all of them do, in fact.

Nacelle, start, profile.jpg

Nacelle_ring_2024_bulge.jpg

Nacelle_ring_2024_shrink.jpg

Nacelle ring, proto, finished.jpg

[Frank.de.Kleuver]

Wow, that's an impressive shrinking action. Did you have to anneal in between?

And what kind of material is used as hammerform?

Many thanks for sharing.

Grt

Frank

[Overkill]

In reading the other posts, I realize I forgot to mention how long it takes to change between die sets. To do so, you simply release the lever that holds the motor in place, lift the motor, take out the upper and lower, install new upper and lower, lower the motor back down - and that's it. Seconds really.

Changing the motor takes a few more seconds, as you have to disconnect the quick connect air hose fitting.

There is no comparison to how long it takes me to change my thumbnail dies in the Pullmax.

[sblack]

Wow - was that whole piece made on the air hammer or was it pounded down over the hammer form with a mallet and then cleaned up on the AH? That is really nice - lays down perfectly. Medium air unit or heavy?

Maxarudy you can see how he trapped that bit from all 3 sides, then pounded it down. Soft dies mean no marks.

[crystallographic]

Originally Posted by Frank.de.Kleuver

Wow, that's an impressive shrinking action. Did you have to anneal in between?

And what kind of material is used as hammerform?

Many thanks for sharing.

Grt

Frank

We do not anneal 2024 in making these parts. The game is to make the part fully-formed, from 0 condition, without the work-hardening causing fatigue failure.

The part is then heat treated and naturally aged, with distortion removed and all contours brought into .020" compliance. Lasers are used for contour confirmation, and then dye-check penetrant, ultrasound, and eddy current for metal soundness, prior to acceptance for use.

Since this is aircraft work, the tool is traditionally called a form block, and is machined from RenShape 5166 (Ren Materials is now under CIBA-Geigy). ("Hammer form" is a fairly recent automotive term, while "form block" dates back nearly 100 years in aviation.)