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Phooey! Broken front sight clamping screw
Loosening the clamping screw this morning at the range during my first outing w/ the 10/43 No4 Mk1 ROF (F), it went POP! Sheared right in twain. Thought I'd broken the tool at first, but no...
Should I attempt to drill out the remainder or is it too hard? I reckon that the sight base can be removed w/o breaking anything else, but the screw stub resists a file rather more than was expected! No EDM to which I have access any more, so what to do?
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Last edited by jmoore; 12-04-2009 at 03:41 PM.
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12-04-2009 12:44 PM
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The few that I have messed with were not that bad. A swiss mico file cut them like butter. Try a good bit in the pin vise first. You can always drop back to a Carbide bit.
If you are worried about cutting the thread peaks in the hole hit the sides of the drill flutes with a stone so the sides of the bit will not cut, only the front face will.
Last edited by JBS; 12-04-2009 at 01:36 PM.
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Take a tip......... replace it with a 4BA allen screw.
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Easy out or drill center of screw out just leaving threads, chase with tap. Standard practice in pre EDM days. The heat from drilling should loosen the screw but try some Kriol and then the easy out.
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If the screw were bigger, drilling would be easy! Done hundreds and thousands, more maybe! Its the little bitty ones that give fits, esp. if its unusually hard like this one. Will report back later.
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Looks like if its drilled from the rear the unthreaded portion will act as a drill guide. Now to round up a carbide drill of appropriate size. I suspect the hole wasn't tapped deep enough, but I'm not inclined to pull apart the trials rifle just to look, since its apt to be different anyway. There'll be spares to inspect at home.
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May the lords of all things screwed be with you,,,,, wait that did not come out right !
Hope you get it out.
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The unthreaded portion (the rear) measures ~0.118"/3mm which would be great IF I lived anywhere but the US. The nearest carbide drill bit on hand is 0.125" which may have to do if the M42 #32(0.116") bit doesn't work.
If it was just a shooter, it would have a new sight base right quick, but gotta try and save this one- it has that rough machined look that matches well w/ the rest of the rifle. I really hate having drill bits crash the parent metal threads, its just not acceptable w/o a repair of the entire grip length. (Too many years working highly stressed/ highly cycled parts!)
Do you think there's Heli-coil thread inserts this size?
No coffee! Bad eyes-sort of, and up for 21 hours so far, think I'll try later! Thanks for the drill motor offer, but I think it'll go on my Motor Avey (size 2 type B style MA-6). Its-a verra nice-a!
Last edited by jmoore; 12-04-2009 at 06:38 PM.
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If I were you JM, I'd remove the block, band foresight from the barrel (take care with the taper pin first) then drill it out from the rear where you'll see the exit hole. Use a drill this size and I bet you that as soon as the drill starts to grip, it'll unwind the broken screw out. I don't think that the reverse headed screw is hard......
If you're really stuck, just tell me and I'll see if there's a new or used/perfect block in the Armourers shop, with their compliments.
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Thank You to Peter Laidler For This Useful Post:
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Originally Posted by JBS
