punch & die build (video)

[Tony]

for better or for worse here it is, for anyone interested:

http://youtu.be/Dmj42zD8yEs

you can see in the vid that i run into trouble with the stripper. I'm still having
problems and can't quite figure it out. Sometimes the stripper 'plate' gets really
stuck to the punch. couple of times I had to flip it over and use the press to
get it apart!

its acting like:
1. the punch is bent (but best I can tell actually looks fine)
2. some small amount of material that i'm punching is wedging in between the punch
and the stripper plate? (though I haven't found evidence of that either)

maybe just poor design?

comments/crits welcomed.
Tony

[Jaakko Fagerlund]

Too weak spring and/or hole in the stripper is too small compared to your punch and it sticks to it.

Usually a stripper plate is actually a plate that sits on the die with a couple of screws or on the upper half of your press frame, so it is fixed in relation to the punch.

[torker]

Strippers need to be pretty heavy duty with heavier plate. On my 40 ton machine they are 3/8" forgings that bolt solid. No springs...
Also....(a trick I learned here)....oil your punch. Just swab a bit on with a brush. Punches way easier...and strips off easier.
Good job on the punches tho
Russ

[Stern]

Great video, thanks for putting the link up.

[Rustybolt]

2nd torker
Heavier spring and a little lube.
Nice job.

[Toolguy]

+1 Heavier spring and some lube. Looks fine otherwise.

[bborr01]

Too weak spring and/or hole in the stripper is too small compared to your punch and it sticks to it.

Usually a stripper plate is actually a plate that sits on the die with a couple of screws or on the upper half of your press frame, so it is fixed in relation to the punch.

How is the stripper supposed to strip the part off of the punch if is fixed in relation to the punch? The punch needs to come up through the stripper plate to strip the part off from the punch.

Brian

[TGTool]

How is the stripper supposed to strip the part off of the punch if is fixed in relation to the punch? The punch needs to come up through the stripper plate to strip the part off from the punch.

Brian

That probably means fixed to the die. A box stripper is bolted to the die or shoe with just a space for the strip to feed through. The part drops through and the scrap feeds out the other side.

[krutch]

I didn't watch entire video, just to the channel punching part. You should have different punch/die combinations for the different thick materials.
Ideally, punch/die clearance is based on %-edge of material thickness. Thicker the material more clearance between punch and die hole. You may always have issues for such thickness variations using one size p/d set.
Stripper spring should be heavier and stripper hole could be tighter for thinner material. OK for stripper to be with punch as you have it. Especially for varying material thickness use.
Other than those considerations, you are on the right track.

[Jaakko Fagerlund]

Here is one picture found by Google of the stripper plate, hopefully explains.

[bborr01]

That probably means fixed to the die. A box stripper is bolted to the die or shoe with just a space for the strip to feed through. The part drops through and the scrap feeds out the other side.

Oh, I thought that when Jaakko said that the stripper plate is fixed in relation to the punch, he meant that the stripper plate was fixed in relation to the punch. I have spent a fair amount of time servicing high speed carbide progressive dies and have a pretty good understanding of how they work, although I have never built one from scratch.

Brian

[cameron]

Here is one picture found by Google of the stripper plate, hopefully explains.

Is B supposed to have the fixed stripper as well as the movable? I can't see how that would work.

[Stern]

I think they messed up on the pic, as the one on the right should be shown without the stripper plate they point to on the left. Got to love "cut and paste" lol

[Juergenwt]

If you use a spring stripper figure about 25% of punching pressure for the stripper spring. Clearance should be 6% total for perforating since you are using a range of thickness. Your spring is much to weak. Slug looks good. Once you get a "double die break" you will know your clearance is to small for the thickness of material. I you are getting to much of a roll-over than your clearance is to big.
If you can't find a stronger spring you need to go to a solid stripper plate or stripper hooks on both sides of your strip.
Instead of a spring try Polyurethane - just a piece with a hole for the punch. Adjust the length of the polyurethane by putting washers on the top end. Must protrude over the end of the punch.

[outback]

It is not proper practice to place the spring around the punch. The spring stripper plate is preferred where more springs
can be added along with heavier springs. A spring stripper always makes contact with the work piece, not shown in the sketch. The spring stripper also holds the stock down and flat while punched then strips the stock off the punch.

The part that holds the punch, called the punch holder, usually has a bored hole for the punch and a counterbore to clear the head. The counter bore has as precise depth so the punch is held stationary. If the punch moves in the punch holder it will wear the bored hole. Eventually the punch will become loose, wobble and may clip the die edge thus dulling both.

The concave punch will not reduce tonnage.

However, I'm thrilled to see someone that has interest in die making.

Jim