Printable View
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?
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.
Take a tip......... replace it with a 4BA allen screw.
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.
https://www.milsurps.com/images/imported/deleted.gif
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.
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.
May the lords of all things screwed be with you,,,,, wait that did not come out right !
Hope you get it out.
Actually his age, vision and how much coffee he drank today will determine how much his drill hand shakes. :eek:Quote:
Originally Posted by JBS
I have a Polish Machinist battery powdered hand drill if you want to borrow it. :rolleyes:
https://www.milsurps.com/images/impo...d20drill-1.jpg
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!
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.
Got the block off and discovered that the rear does seem to have plenty of unused (untapped even!) bore that ought to help line things up. I'm hoping that it will loosen, but that never seems to work out w/ aircraft parts!
Dab nag stinkin' screw portion that came out is really pretty hard- much more than it ought to be. I'll try and check it on a Rockwell hardness tester in a few days when I see the fellow that has one.
Thanks for the offer of a new block, but if this operation doesn't work there's another that I pulled from an incomplete Long Branch that has a 1955 Faz. bbl. assembly.
Do the block retaining pin holes line up from rifle to rifle, generally? They sure DON'T on M-16s!
BTW I think this is the first part I've broken on a L-E variant! Must not be trying hard enough...
.
Wow! Tried 2 new cobalt split point drill bits and did not get the first chip! The 0.125" carbide bit worked fine, but the chips were hard enough to break up rather than string. Best of all it stayed centered. The block was definitely not tapped deep enough, so it got a 4BA tap run in (after having cleaned out the old threads). Now to find that pesky cross pin.
:dancingbanana::dancingbanana:
Lots of fretting over such a little thing: I just have no sense of scale.:p
Remember when you get the sight all back together and tighten the new clamping screw, to tighten the screw until the threads start to smoke and then give it two full turns more. :rolleyes:
I’ll let you borrow my surplus NASCAR impact wrench. ;)
https://www.milsurps.com/images/imported/deleted.gif
Your pictures brighten me up on a dreary Sunday Morning Ed. Who could have thought of the Polish hand drill like that!
A retired Colonial Rebel with too much time on his hands who has a Polish mother-in-law.Quote:
Originally Posted by Peter Laidler
Aim High, U.S. Air Force
https://www.milsurps.com/images/impo...untitled-1.jpg
I think that's how it was installed the last time!Quote:
Originally Posted by Edward Horton
FYI The screw head itself measured ~8Rc, not hard at all. However it quickly increased in hardness as we moved down the sectioned threads, going from 22Rc (OK) hardness upwards! Judging from the difficulty drilling from the tip towards the fractured portion, it was probably 50-60Rc at the tip. Bad day at the heat treat facility, I guess.
BTW If that lug bolt pic isn't photoshopped, it's amazing! Misspent too much time at the GT "trade school" playing at failure analysis...
Jmoore
The next time your in a garage or service station ask yourself when was the last time the impact wrenches were checked for torque calibration. On aircraft they were never used because they were unreliable, torque wrenches were always used and they were checked and calibrated every 90 days.
Below impact wrench over torque. :nono:
https://www.milsurps.com/images/imported/deleted.gif
Nice ductile failures. I think that one difference w/ these abused fasteners and the ones we failed is that the ones you show are too "short" for whatever they were they were installed. A/C fasteners, as you know well, are selected so that the unthreaded shank is run as close as possible to the nut+washer resulting in generally short thread lengths and -failures- at or near the thread origin if overstressed.
Not only do I not use impact wrenches except when disassembling fasteners that won't be reused (in any application, including farm equipment) but my torque wrenches for critical work are also calibrated. Not to mention my other measuring equipment....And firearms people think the govn't have too much involvement in their lives!
We don't use impact wrenches (or whizzy-wig hammers as we call them) either and our torque wrenches are calibrated annually, together with our gauges and other measuring equipment.
Nuts, screws and bolts are a science in themselves....
How I cringe when I see the tyre (or tire as you wild untamed colonials call them...) garages where they whizzy-wig the wheel nuts back onto the wheels/hubs. No wonder you never get them off again at the roadside
Good technical thread here guys..........
Hey I resemble that remark. :lol:Quote:
How I cringe when I see the tyre (or tire as you wild untamed colonials call them...) garages where they whizzy-wig the wheel nuts back onto the wheels/hubs. No wonder you never get them off again at the roadside
You should here what Peter calls the Australians when they cheat at Rugby and bite the British player’s ankles and poke them in the eye during the silly game. :yikes:Quote:
Originally Posted by Doug Rammel
(At least the wild untamed colonials wear protective head gear) :D
I've got plenty of new blocks if you need a replacement. One day service to Atlanta!
I need to make a road trip over there, if I ever get caught up! Atlanta is a place I try to skirt around.
I know what you mean. It was piled up on the east side when I came back on I-20 the other day finishing up three long days driving back from SAR West in Phoenix. I almost bought the farm in Texas in the bad weather too on Monday night. It was a big time wake up call.