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broken/tored off ballend thread

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Well, this is what I am most afraid of. Theoreticly the arm its not broken but most likely it will be when trying to pull out the leftover thread. I am wondering if I should post it here or asking my dentist instead. :lol:

If it would have happened on my motobike, I would weld a nut on the broken stud, which works like a charme. You center the nut on the stud and fill it up inside through welding. Usually you can screw it out after.
But not in this case, plastic will melt away. Even if I use the tiny proxxon with flexible shaft and handpiece, it might get too hot and melt the ABS around.

Any tricks welcome, even black magic and other rituals.

DS_rear_susp_01.jpg

 

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If you have a pillar drill and a desk vice I’d suggest boring it out and bonding a dowel in to remove it. Ideally a reverse cut bit so any torque into the faster will unscrew it rather than have it strip the thread, some WD-40 applied as you machine you should be ok if not. If you stuff it up and strip the thread, bore out a little larger and see if you can helicoil it. If you have a matching fastener measure the core size first! You can get bolt removal tools that once you drill the core you can reverse screw in, but I’m not sure what size you’re at if it’s M3 you might not find one.

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you could try and cut a slot and get a flat blade screw driver on it but it looks as if it hasn't sheered of flush so not to easy to do but the first way of getting it out that i thought of was the same as @Lee76 But WD40 attacks plastic so you would have to give the arm a thorough bath or spray it with brake cleaner.

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Easiest option is to lower or raise the suspension and use a different hole...

I've had similar problems before and clamped it in the vice on the milling machine and drilled it out with a milling bit. A drill bit will bend and wander and these things never shear off flat. Line it up with a 3mm rod and then drill it out with a 2.5mm milling cutter.

This is another good reason to tap all your holes in plastic with an M3 tap. When the end shears off the remaining stud is usually quite loose and can be persuaded to undo.

Your best bet is to clamp it in a vice, and use a sharp piece of steel rod to centre punch the brass stud, then drill it out with a 2mm drill bit. Get a piece of 2mm steel (e.g. old drill bit) and loctite it in the hole in the brass. then try and undo it with a good pair of pliers.

 

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Yes guys you are all right with your idears. It will be more or less a surgery. First I have to get a 2mm milling cutter, drills are not really good because the start to bend trough, as you mentioned.

Cutting a slot is not possible because the rest of the thread is lower then the plastic arm. I want it out to keep the present geometry, othervice I would just take the next hole.

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I bought a set of diamond burrs for my rotary tool and one of them is a 6mm diameter disc on the end of the 3mm shaft, and is about 1mm thick, so you might be able to get something like that in to cut a slot without damaging the plastic. 

If you choose the drilling route, you don't need a milling cutter, a round burr will do to create a dip in the centre of the remaining stud. You can then drill without it wandering. 

Finally, have you thought of getting something like a chisel (or on this scale it might need to be the end of a broken drill - something hard that will dig into the metal) and unscrew it by tapping the stud around by its edge? This works on larger screws - not sure how successful it will be on something this small but it might be worth a try. 

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