measuring indent crimp?

[coppercone2]

How do you measure a machine pin indent crimp after crimping to verify if its crimped correctly? I can only find tutorials online about normal crimps that fold.

[coppercone2]

this is for the 4 indent crimps btw, like avionics, I thought there must be a guide some where but I cannot find it. Do people just blindly trust these crimps? I thought they are used all the time for every airplane.

[David Hess]

Do some test crimps and then dissect them to see if the metal surfaces fused to make a hermetic joint like they should.

[coppercone2]

hmm, so there is no way to do it with a caliper?

What do you recommend for cutting them so its easy to make a nice profile? I got a old indent crimper that I want to verify (usually I don't buy old but this one is nice, some kind of amphenol), it does not look ridiculous like the new ones that have a dial on them, it is instead a normal screw, I thought the aviation crimper was some kinda beer opener at first

I have jewelers saw, hack saw, dremel with various disks (abrasive, zicronium super durable abrasive (whatever the 20 dollar disk is that I can plunge into granite and cut steel glued inside), jig saw with metal cutting blade

I am not sure if there is something specific with cutting crimps apart like if some type of cutting action may yank on the wires that are compressed together in some way that distrubs the profile, since these are so tiny with tiny wires.

Then I suppose I lap it on my surface plate and expose it to ferric chloride? How do I hold that steady when its so small? I think I would need a special fixture with a bore in it to put the crimp into then push down on it while I am lapping

I get how it works for a big fat crimp, but this one I am not sure about. I am kind of.. in disbelief that this is the process that a normal small aviation shop goes through to do this.

someone at work actually measured them with a crimp micrometer, at least the normal crimps, but I never ran into this in the wild before, they are not friendly for being belt fed into machines so it was not popular. I only use them for my home solar with the reischsomething green crimp tool, but those are massive and I bought the tool brand new for $$$, and it has to be a improvement over the folded crimps. The solar panel is not exactly an airplane. It also does a single detent at 1.2 tons so I can trust the mechanism more, this one I want to test has 4x detents.

Is everyone just fuckit yoloing this?

What I want to do is put it in the 3 jaw chuck in the proxxon mill with a abrasive blade so I can cut it very flat and hopefully get away with not polishing it. I think a normal milling machine with a thin cut blade would work better though, and leave a smoother finish. I think abrasives might cause the materials to smear, but its the only way I can do it perpendicular. Maybe a fine blade in my mini chop saw?

Is there another way to do this like a big over current or pull test?

This is what I want to use:
https://www.digikey.com/en/product-highlight/h/harwin/datamate-t-contact-female-power-contacts

[David Hess]

What do you recommend for cutting them so its easy to make a nice profile?

I use a dremal with abrasive cut-off disk.

If you can peal the crimp apart, then the individual wires should stick to the connector because they have effectively been welded by pressure.  This is how wire wrap joints are tested and why wire wrap pins are square instead of round; the sharp corners fuse with the wire which becomes apparent when you unwrap them.

After you measure some test joints and verify that they are properly crimped, then their measured crimp height might be an acceptable proxy.

[coppercone2]

you mean cut a slot down the tube and try to pry it open like a banana?

[David Hess]

you mean cut a slot down the tube and try to pry it open like a banana?

That is not exactly what I was thinking of but it would also work.

[coppercone2]

I think I can grind it in the proxxon with a silicon carbide grinding wheel after cutting it with a cutting wheel to make it better and just look at a cross section. I always wanted to do it myself. I have some cup stones that came with my purchase that look very flat and possibly correct for the purpose of some kind of surface grinding operation

Or I can set it up the 3 jaw mini vise sideways and manually spin it into the grinding wheel by hand while traversing the bed.. i wonder what will happen.. like a really bad caricature of 'superfinishing' comes to mind since there are two rotating bodies.. I even 3d printed a water cooling attachment

[penfold]

I think the accepted method for validating crimp depth is to just use a go/no-go gauge in the crimper itself to check the depth at the end of the ratchet cycle. It's not a bad assumption for something like the DMC crimpers (I don't know if other brands allow the jaws to slip and potentially not go far enough). A successful crimp can often be judged by passing a pull test though.

There are a variety of micrometers with pointy anvils for measuring that kind of feature, I just can't remember the name of them, I think "groove callipers" have which have interchangeable anvils for getting into grooves and holes on a diameter, small enough ones with sufficiently pointy tips may exist.

[coppercone2]

There is no tables to tell you what is right.

And it sounds like this would be difficult to hold, it sounds like maybe you need a bench micrometer?

[penfold]

Bench micrometer, or a bench vice or perfect the art of holding the mic between 4th and 5th finger whilst adjusting the barrel with your thumb.

I apparently didn't read the post correctly because I just noticed the Harwin Datamate link. There's a pull-off force specified in the datasheet. There should also be a specified go/no-go gauge called up for the given crimp setting. So long as you're using the correct wire gauge and crimp setting and the crimp is occasionally calibrated (go/no-go check and occasional pull-to-destruction tests) you can expect consistent results.

I think there's a standard from IPC that gives a method of determining a production pull-test limit from the datasheet pull-off value.

Also just thinking that measuring the indent depth isn't necessarily a good indicator of successful crimp because the tool will only cycle through to release the ratchet after going that full distance, so it would measure the same depth even without a wire in there.

[coppercone2]

True.  Iwas thinking that maybe its like, deformed at the tip, but I guess I should be able to find it on a microscope to see if they all look the same, or off center.. if its off center it should be plainly visible but I think it would like pinch the walls into themselves rather then forcing pressure on the wire directly. I can get some drill blanks to do the go no go test if I can find them in the right size or maybe buy the thing

For pull force is wrapping a wire around a barbel plate and slowly lifting the crimp up in a hand vise good enough? I never did a real pull force test, only yanking to see if crimps come off and if the wire gives the characteristic tension of good metal bonding after I make a crimp, and only on the crappy fast on connectors

Also, is this suitable for optical fiber? They sell the same looking tool for optical fiber crimps.