More punching on the Hydraulic press... | Page 2 | Power Hammers and Presses | Forum

Your press looks good Larry. Looks like it is working well for you.

I like David's idea for a punch holder but it does mean that the base of all the punches needs to be machined because they rely on a flat surface to align them. This means that forged punches either have to be done very carefully so as not to mess up the collar or the machining has to be done after forging and annealing. I suppose the collar could be forged in a die and the end ground flat but it still involves being careful not to mess up the collar.

I was thinking about it this afternoon while I was doing some milling and I thought of using a simple collet to hold punches. I like the idea of making any complication in tool holders rather than the tool, so tools can be really simple to make on the fly. How about this idea? I have left the sides off so it can be viewed and there would either have to be a way to break the taper loose or the taper could be made steep enough that it is not self holding. The plate on the bottom would be bolted to the body to tighten the collet. Different sized collets could be made fairly easily for different punch stock sizes.

John, yeah you're right about it means you can't do forged or extra wide punches with a machined shoulder. For wide punches I use a 2 part system with the top part having the shoulder and the punch part screwed to it with a 12.9 grade allen bolt.

If you look at one of the photos in the thread on punch geometry, it might explain it. The image is on my laptop which is at the workshop so I can't post it here. I'll try to take some more detailed shots today. The punch in my hand is one of the 2 parts (note the thread), the top part is near the edge of the bench by the welding clamp. I guess Larrys concerns about upsetting apply to the interface of the 2 parts but I've had no problems in quite a few years. My press is only 15T but the system works a treat so I'm sure it should for 40T if suitably scaled

The only difference between what I suggested to Larry and my punch is that mine uses a screw on collar to "clamp" the punch, my proposal uses bolts. I'm sure if these were big enough, with a suitable thread area they wouldn't pull out. With hindsight I think I would have gone for something like this to start with.

I agree TOTALLY with you about making the punch simple and the clamping having any comnplicated machining. With the two part sytem, its a compromise, all you have to have is a turned parallel end with a thread in it. I do this before forging for material such as H13 that are difficult to machine after forging

Having said all the above, I like Johns idea if it can stand the pull out forces

Photos will make more sense of my verbiage.

I know I'm a little above my pay grade here:unsure: but while reading this thread, it occurred to me that a hybrid of JNewman's system with the flat on the chisel and a bolt through the collar. What about a wedge instead of the bolt? It would mean a bigger coller to occomadate the 2 holes need for the wedge. Then tolerances could be a little looser for hand made tooling. My description is a bit vague but I could take a picture of what I mean. I have something like this on a power hacksaw.

Interesting idea. I've always gone for tools with a head like the ironworker punch. In long run production, I've never found anything else to work. Your wedge is actually much easier than it first seems. You'd only need an intersecting cross hole in the holder and a flat on the tool shank. Grind a taper flat on a round bar that fits the hole and drive it in. Taper angle wouldn't matter either, the shank will rotate to match automatically. Needs to be of generous size and heat treated, you sure don't want it getting distorted or you'll never get it out!

Holy Crap! They got a name for it? Hmm, "cotter crank" well, what ever works. Like I said, I'd sure want a good hardened pin.

So here's a picture of what I was talking about. The shaft is 1" and the pin is 1/2" and very hard. Note the long taper. The set up is spring loaded a little. I think this could be a nice simple set up.

This press thread is awesome! What a great tool for production work. Even play...

I have a small press, but this thread is urging me to build a larger one. I don't do production, but it still would be fun.

Hey guys,
What I know about presses is that I want one. So with that in mind, would you explain how this works? What part is the press retainer? Do you intend to have a flat surface on both retainer and bit to prevent distortion in the internal area? It seems to me a taper would have a negative effect in preventing that, And that shims of some sort would be required to keep the fit perfect for each bit. Pull me back in line if I’m heading in the wrong direction but I think, if the shank is strait, the meeting point is two flat surfaces external from the shaft and the slot for the wedge is longer than it can enter into the female part distortion would be minimized in the hidden parts. Is this what you guys are talking about? Or am I gathering this information together incorrectly? Reel me in, please summarize all this information, I think most of us non gurus are lost.
Bob

Grant,
I’m thinking this may be a good thread for the tutorial section, apparently a system for this has not been perfected. Perhaps you guys can find it.
Bob