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New bolt head issue.

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Frameman 1 View Drop Down
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    Posted: October 31 2019 at 5:07pm
I am aware of problems with regard to bolt head over clocking but I just purchased a replacement bolt head from Numrich. It appears to be an NOS part.
My old bolt head had a pretty big chip in the edge that locks over the receiver rail. No headspace issue.
The problem I’m having is that when the bolt head is threaded in it bottoms out against the bolt body about 2 degrees before the bolt aligns with the top locking lug. Can I carefully stone the bolt body until I get proper alignment? It won’t take much to get 2 degrees more turn.
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Canuck View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck Quote  Post ReplyReply Direct Link To This Post Posted: October 31 2019 at 5:10pm
Can you take some pictures possibly of what it all looks like up close?
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Frameman 1 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: October 31 2019 at 5:42pm
I’ll get a few pics tomorrow. I locked up my toys for the night.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Goosic Quote  Post ReplyReply Direct Link To This Post Posted: October 31 2019 at 8:44pm
Long and short of it is yes, you can stone the bolt to get the bolthead to align with the bolt itself. You can go 10°-15° over rotation of the bolthead and still be in specifications.  Take your time and go slow...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bear43 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 5:19am
Just so you know, Frameman, it's not unusual to have to try several bolt heads to find one that properly clocks in. It is one bit of a downside. Sometimes you get lucky and get one that fits right out of the gate but that is unusual.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 5:51am
There was a wrench for armorers to do this. Think "Receiver wrench for bolt head". Basically you immobilized the head with the device in a big bench vice & kinda "broke the threads in" by tightening & releasing the bolt body several times.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Canuck Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 7:26am
In essence, stretching the threads to make it fit. To the OP, check to make sure there are no burrs between the bolt head and bolt body interface before doing anything else, that is my suggestion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 7:33am
I’ve seen the bolt wrench in use. I’m not that confident.
This thing is so close that I will go ahead and stone the bolt body to get where it needs to be. The new bolt is brand new an just long enough to put the headspace just right.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 7:47am
Not really stretching, more lie scraping off burrs & so on.
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Post Options Post Options   Thanks (2) Thanks(2)   Quote englishman_ca Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 10:52am
Don't stone the body. It will work, yes, but not the prescribed way. Use that method only as a last resort.

Most people don't have the luxury of a drawer full of bolt heads to find one that fits both head space and clocking specs.

Put the bolt in a padded bench vise and crank on that bolt head with a wrench. I can guarantee that you will not strip the threads. It will move the last two degrees with some encouragement and a cheater bar. Lots of oil, work it back and forth.

Stretching the threads is inconsequential. They will form to one another and wear as they break in.
The only time that they are actually under any load is when cycling the bolt by hand, chambering and extracting a round. That loading is insignificant.

There are early Lee Metfords that don't even have threads on the bolt head. The bolt head is held in the bolt body by a grub screw in a slot. The force of recoil is taken by the ring of the end of the bolt body where it touches the bolt head.
However, a grub screw in a slot makes for lots of slop at extraction and some of the primary extraction travel was lost. Hence the update change to a robust threaded bolt tenon on the MLM Mk.II .

The brunt force of recoil on yours is also taken on that anulus of the end of the bolt body where it contacts the bolt head, not the threads. Even a tiny amount of over clocking will give a little thread slack when bolt is in the battery position. The threads should not be under any pre-load with the bolt in battery. 

The bearing anulus is a very important part. That is why stoning it is frowned upon as it can knock that bearing surface out of true.

Armourers did not stone the bolt as doing this once or more over the course of service maintenance would alter the bolt permanently out of spec so that many perfectly good bolt heads that would normally be suitable for use would now be overclocking on the stoned bolt.

One should hand fit the replacement part to the rifle, and not fit the rifle to the replacement part.

But in your case, this would likely be the last time in future life that this bolt head will ever need changing again. I guess stoning would not hurt.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 11:37am
I appreciate the tutorial. I will try your method first. I can always go to plan B if I get scared.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 1:22pm
Don't forget the often quoted 15° is MAXIMUM ALLOWABLE, not  "AIM"! once you're on or just past dead on you're GTG.
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 3:28pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 3:51pm
well I finally found the time to revisit my new bolt head and am glad to report that by “force fitting” the new head I was able to get it perfectly aligned. I also tweaked the extractor spring to soften it a little and now it extracts rounds a bunch easier. The she!! casings were dragging heavily on the edge of the chamber and receiver as they were being drawn to the rear.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Frameman 1 Quote  Post ReplyReply Direct Link To This Post Posted: November 01 2019 at 3:54pm
Old bolt head
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shamu Quote  Post ReplyReply Direct Link To This Post Posted: November 02 2019 at 7:02am
Sweeet!
Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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