Screw press?

Why vee threads? Not recommended for power transmission.

We have three small screw presses at work (roughly 18" tall when closed). When apprentices perform their final practical exams under the supervision of instructors from Germany, the screw presses are used. Probably because you can actually *feel* how much tonnage is required to get the punch through the die.

They use double start square threads (not sure if the Germans use Acme or anything like it) roughly 25-35mm IIRC.

I can ask what kind of tonnage is expected if it would help you.

You should generally not run a press at more than 80% of what it might be capable of. Perhaps not an issue in your case but in production, exceeding this value will cause premature wear (causing misalignment between the ram and the bolster, in a number of ways).

Regards,

Robin

I know.. but I'm working out of the hardware store remember. (Both ;) and :( are applicable here.)

Isn't square the same as Acme?

At 20 or 30ksi, a 1" hole in .03" metal should take a little over a ton by my figuring. I should be able to get some pretty heavy stuff done with 16 tons!

Understood. Speaking of wear, I was thinking of mixing up some high-lead bronze to use for the bearing parts (thread, thrust bearing). :) Also optionally stripping the galvy off the allthread (like I said, HW store..) and case hardening it. But that'll be a bitch without a larger furnace (to keep the rod and carbon packing hot for hours(?)), or some Kasenit.

Tim

-- "That's for the courts to decide." - Homer Simpson Website @

How about starting with a really big C-clamp instead of Allthread, et al? That would give you a strong square threaded rod and a cast iron "nut" to work with. Hacksaw off the "C" from the clamp and mount the threaded portion in your frame. In fact you might be able to scrounge a broken C-clamp from a junkyard or similar.

Alternatively, look for an old office chair at the dump. The piece that attaches the seat to the legs is heavy square threaded rod, about an inch OD. If you could cast an iron nut for that it'd be pretty strong.

Nope -- similar, but not the same. The included angle on Acme is 29 degrees, IIRC. Square would have truly parallel sides.

Square is harder to cut, so Acme is found more often these days.

Enjoy, DoN.

I always thought a little flyball press would be neat to make up, they had one at the S.F. Old Mint before it closed. It used a multi-start square thread of fairly coarse dimensions. On the other hand, there have been a number of small presses written up in the mags like HSM using bottle jacks that would be a lot easier to make up. Depends on whether producing a punch press or punching the holes is more important to you. Personally, I'd look for a Roper-Whitney in some of the larger sizes. The Jr is good up to a little more than 1/4" dia. and 18-20 ga. in steel, there are larger ones for thicker sheet metal and bigger holes. I've got one that uses a screw, takes about a half turn to punch holes, the others are toggle presses.

Stan

---------- Try to find a junk garbage compactor. It has just what your looking for , 1" dia Acme threaded rod and a bronze nut. Don Warner

I completely forgot about that. As long as Tim's willing to invest in a bottle jack (almost certainly under $20 for something like 6-10T) it'd be pretty easy to make. You can really just bolt the steel tubing together if welding isn't your thing.

Much easier than fiddling around with screws and linear bearings.

BTW, I don't think the press tonnage, in this case, is really limited by the screw's ability to resist the force, or the power supply's ability to produce it. Rather, it'll be the press' frame. At school they had a 50T manual hydraulic. Someone went nuts on it and bent the steel tubing on the bolster way out. Consider that a *real* 20T mechanical press would have a large cast frame (weighing probably more than a ton).

Regards,

Robin

Looks like time to break out one of the old vise screws I have accumulated over the years. Gerry :-)} London, Canada

If you just want a press, and not a project, you might be able to pick one up for scrap value at an auction. Even on ebay, they are usually pretty cheap.

Tim, Email me your address (at my real email address of paulhagenATinsightbbDOTcom) and I'll send you a large screw suitable for the press you envision. I happen to be particularly blessed with large screws just now. Paul

If you happen to get one, ask about safety here and on AMC (or ask a professional). Rarely does one get a "second chance" or a "close call" with a mechanical press.

Good for making holes though. If you don't need great quality, you could make a punch and die set reasonably easily...

Regards,

Robin

Even hand powered ones? From stuff blowing apart and shooting out at you?

Hell yes....

was using a little #3 arbor press and grabbed a drill blank to help push something through. Not thinking that night, I reefed on it (no cheater bar) and the set-up slipped, the blank broke, sending the blank flying into my gut. Slightly penetrated and bruised like hell. Had this been a bigger press I would have probably had a good hole to fill afterward. Oh yea...wasn't wearing eye protection....the right conditions and I would have been ol' one eye too.

Koz

ATP wrote:

I was more talking about powered mechanical presses, but you're right that things can explode inside any type of press. I believe hydraulic presses are really bad for this because you can't easily feel how much pressure there is - and they're capable of lots exerting lots of pressure.

The larger manual hydraulic press at school had a lexan/plexiglass sheet to protect the operator...

Regards,

Robin