Swage for nesting 1/2" emt conduit

[AndyA]

Originally Posted by ThorsHammer

the problem with that design is it takes a lot more force to force something through a hole than it does to compress it. not to mention that you'd need some sort of ram to get it to work.

I was still talking about a split die that you use with a press.
Just do two hits. One to start the dimples and eggshape it a little. And the second to size it.

[CosmicRambler]

Originally Posted by AndyA

Why not make a die with two holes side-by-side. The first hole is the same size as the original tube, but with strips to start the dimples. The second hole is the one that reduces the diameter and crushes the dimples. You might even design the first hole so that it intentionally egg shapes the tube just a little (makes the dimpled sides a little closer together). Then you can rotate it 90deg when moving to the second hole so it fits nicely in the reduced diameter. The dimples would be along the parting plane of the die and that may help solve any 'pinch out' problems.

Yeah that might be a great approach. Two passes or even three if that is what it takes. Ye olde progression.

Could just work and he has the ability to make one. With enough tries you always come up with a solution.

[ThorsHammer]

thats essentially what he has, the only difference is it has wings instead of dimples. He's looking for something to do it in a single step. instead of two.

[papaharley03]

And there's nothing that says it has to be two dimples. Could go with just one.

Plus, I think that a sharp point like I illustrated is better at starting a dimple than a rounded dimple surface.in the die.

[forhire]

Ok, I messed around with this a little tonight. First I retrofitted a two wheel knurling tool with two small bearings. The knurling tool defects the pipe too much and has little results. Supporting the tube with a live center made it impossible to shrink the end and an attempt to shrink in the middle, while it appeared to work somewhat, it belled the end like a horn.

Next I removed the cutting blade from a pipe cutter and replaced it with a bearing. Initial tests by hand suggested it might work. In the end the conduit became square. I thought maybe I had gone too quickly so I mounted the cutter in the tool post and went at it. Even after a few passes it was clear it was going to be square. I now know how to make square tube.

I suspect that the pressure from the single roller against the two rollers made a flat spot and as the tube shrinks it becomes more pronounced. Maybe squeezing with one roller opposite another may work... sounds like the scissor knurl idea

Don't bother giving me grief about the chuck jaws. I've been facing large rounds today and more of the same tomorrow... I didn't want to change my setup for a quick test.

Well... now I know what doesn't work.

I snapped a couple pictures. Enjoy

[ThorsHammer]

I wonder if having the three rollers evenly placed would help?

[forhire]

Originally Posted by ThorsHammer

I wonder if having the three rollers evenly placed would help?

I don't think so. The lower single roller is pushing straight up creating a rise between the two upper rollers, eventually leading to square shape. Two rollers on the bottom equal to the two uppers might do the trick.

[ThorsHammer]

so two total, or 4 total?

[forhire]

Originally Posted by ThorsHammer

so two total, or 4 total?

Two might work... four would likely be better... all I know is three makes squares

[ThorsHammer]

three wheels to compress it = how to fit a round peg into a square hole.

[dumb as a stump]

Ya know I am thinking that what you are looking at doing is very much like making a tent pole, for an older type tent. Perhaps looking at one may provide some light on the subject. I am watching this because i have had a desire for the exact same thing but dont have the gear to machine etc. I know that our local electrical suppliers carried 2 inch swedged emt (about 5 years ago when I saw it as a new product) but nothing smaller. I thought it was a great idea at the time.

[Oldiron2]

During metal spinning, the speed it usually fairly high, the point of contact is quite small and a small area of the surface is deformed by just a tiny amount each revolution, but because of the high speed and many resulting revolutions, the shape does gradually change. In your test, due to the large rollers you were just bending the whole surface. Didn't mean it would be easy, but do still think it can be done with your available equipment.

I also agree with earlier members who think expanding the end would be easier. If the tool is properly made, the forces are spread around the entire inside, not concentrated in one place, so splitting won't occur. It is easier to stretch then to swage into a new shape.

The most fun way might be to build a one piece outside die of the required shape into which the tube fits, insert a mechanical stop into the tube above the area to expand but within the die still, add a bit of mud, then an electrical blasting cap, then more mud, ....."Fire In The Hole" and it's done except for removal and cleaning.... Oh well,,,

The standard multi-piece inside die with a tapered hole, a tapered bolt or rod, and perhaps a hydraulic cylinder attached to the rod to work it isn't that hard to machine, but should have hardened insides to reduce deformation and thus friction. An alternative material might be 'hard' but still flexible rubber just compressed by a bolt, or a variation with a tight bronze seal at the operating end and a viscous liquid inside the hard rubber sleeve....

Or suppose you had a mandrel mounted on the lathe carriage with a few hardened pockets for small bearing balls, perhaps tiny lubricant/coolant passages running to the bottom of each from the tool's rear end so the fluid could be fed under decent pressure; then the carriage could be fed into the tube under power. A fine feed, rolling balls and small contact area should allow the micro-deformation while the lube would prevent galling of the tube and stop wear of the ball or pocket. Maybe add screwed-in bottom plugs to adjust the protrusion of the balls in the pockets.

BTW an external version to reduce the tube could be made, I suppose.

"Just thinking out loud."

[forhire]

I tried spinning a piece tonight. Understand I'm no spinning expert but I've done a fair share. The conduit was too large to fit through the spindle of my spinning lathe (I also don't have a three jaw chuck on that lathe either) so I did a quick test on the Lablond, which lacks the rpm and the pin post of the spinning lathe. One thing that came out of the test is that the material will need to be annealed (which I did part way through) and the weld seam is a problem. As soft as emt appears... it's not. The weld seam is hard. Definitely not fast. I'm not really interested in spinning the quantity required. Remember, I built this swage to save time and money.

See how the conduit creased at the weld. The weld may have been the root cause of the square shrink yesterday

[RaptorDuner]

I had good results with 1" EMT in our Aeroquip Procrimp 1380. The smallest die we have (#4) doesn't quite get it small enough.

[forhire]

Originally Posted by RaptorDuner

I had good results with 1" EMT in our Aeroquip Procrimp 1380. The smallest die we have (#4) doesn't quite get it small enough.

I unzipped the images and attached them.

Looks great! I actually expected the crimp to have ridges similar to a hose... but it looks round. The results actually look better than expected.

[ThorsHammer]

but it's still not small enought to go into the un crimped end? can you get a smaller die?

[forhire]

Originally Posted by ThorsHammer

but it's still not small enough to go into the un crimped end? can you get a smaller die?

I'm sure you could get/modify a die to get the diameter desired. I don't foresee a hydraulic hose crimper in my near future... I have other tools on my wish list. I've attached what the die looks like. RaptorDuner was kind enough to test it with his machine just to see if the segmented static die would work or if it had to be a rotary swag.

RaptorDuner, this is a #10... does it look the same as your die?

[AndyA]

I wonder if you could make a collet style crimper? Have maybe 6 or 8 fat slots cut into it to allow plenty of shrink.
Perform the crimp using threads to draw the collet down into a female tapered piece.
I don't know what pitch you'd want to make the taper. A slight angle should give you more force, but may be more likely to get stuck.
You might want acme threads and a thrust bearing on the closer nut since this may take quite a bit of force to shrink the tube.

This could probably also be adapted to use a hydraulic pull cylinder instead of threads to tighten the collet.

[RaptorDuner]

Looks just like that. Our smallest die is a #4 and doesn't quite get 1/2" EMT small enough. The 1" EMT is actually undersized a little too much and fits quite loosly. Our crimper is programmable so with some messing around to find the right preset, you could get a perfect crimp everytime. A #2 die may be available but we don't have a need so I don't see us getting one to do 1/2" EMT.

One note: while crimping I would crimp about 3/4 of the way and back off slightly and turn an 1/8th of a turn and finish. Adds literally 2 seconds at most. If I didn't turn it, it might get better traction in the joint with the small "wings" it would leave. Might have to try that Monday.

We don't actually own this crimper. It's provided by Applied Industrial because we buy hydraulic fittings from them. Forhire, you could contact them and say you'll buy from them if they provide you a crimper.

[fred_dot_u]

Even though this is an older thread, I'd like to join in and comment on AndyA's suggestion. The way I read it is to have two slots, not holes, in the block. One slot is the tubing diameter with a wedge at the top and bottom, with the vertical diameter of the joined blocks to be less than the stock diameter. The tubing would dimple as desired and would remain within the block.

The second slot in the block would resemble the original design, with respect to diameters, but would not have to deal with the spread of the tubing outside of the slot, as it would be the correct finished diameter from the above step. It would be necessary to rotate the tubing ninety degrees in order to place it in the slot, but instead of spreading the tube as the upper part is pressed on, the dimples would compress that much more.

If this is an incorrect interpretation, I'm open to constructive criticism.

If someone is already building one of these, please let me know. My searches online have all petered out, except for this one. It should not require thousands of dollars of hydraulic equipment to crumple ordinary EMT, in my opinion, and this particular thread shows that to be true!

fred

[zipzit]

I know this is a pretty old topic, but I really like interesting engineering problems.

I'm pretty sure forHire has a full size lathe. Not sure, but I suspect he has access to a hydraulic press. How about a cone shaped die and nest? Easier to show you then explain.

I'm assuming a pipe nipple placing force on the ends of the die, forcing them into the nest around the pipe to be compressed. The seven degree angle on the die mates to the 7 degree angle in the nest (in theory) compressing the tube OD smaller.

Assumptions: nominal conduit 1/2" OD=0.840, ID=0.632
Not sure how big your lathe chuck is, I just grabbed 5x5x3" stock for the nest, 2" thick x 3" diameter stock for the die(s). I assumed you'd turn the inner die(s) on the lathe, then cut into fourths with a band saw. I used a 7 degree cone shape. No reason for that number, I just pulled that number outta... the air. The four die pieces complete their motion when bottom of die(s) is flush with bottom of nest.

One problem could be how long the tubes are.. If too long, you'd have to rotate the press sideways and thats a major pain.

comments?
--zip

[fred_dot_u]

I like the simplicity of the cone press method. EMT can be as long as ten feet (50 toes) and would not work well in most presses, I suspect. One reason to perform this swaging is to make longer lengths from stock pieces.

Regardless of the method, dual slot, single slot, cone-press, I envisioned a lever system for my own use, just a ten foot length of pipe pushing down on a short fulcrum to provide quick action and high forces necessary to make the swaging. It would be just as simple to make the lever arm swing sideways, perhaps easier on the back to do so.

I'd want six inch swaging, so a six inch tall block would do the trick.

Before the four sections of the cone come fully together, would the tubing dimple into the gaps and prevent proper forming?

[forhire]

Good ideas. The taper needs to be fairly steep or you'll never get it apart... I'd go with 15 degrees or better at least. Zip were you thinking 7.5 total or per side? I like the hand idea.

I have a couple lathes... wouldn't take long on my cnc.

[fred_dot_u]

Fairly steep meaning closer to parallel or in the other direction, as in closer to 45 degree sides?

How would one consolidate the four cone segments to allow semi-production performance? Add guide pins pm the top of the cone segments that engage a slot on the plate that does the pressing into the die? That doesn't sound right, now that I've typed it out here.

I would look for something to attach either part to a lever, with the other part on a fixed base. Grab the long lever, push it open, slide in the tubing, pull the lever closed, then open to remove. Horizontal movement as noted above.

Four loose cone segments would fall out when the lever was opened, but then again, it would not have to open very far to release the tubing.

[forhire]

I should have said fast instead of steep.

I'll have to measure the angle on one of the hydraulic dies in the morning. My guess the are 30 degrees.