SMLE Bolt Head Underturn

[Peter Laidler]

The same applied to some No4 bolts, believe me! It's all down to drawing/machine tolerances. But the mere fact that you have bolts that will fit into rifles means that someone in the past(hopefully an Armourer....) will have fixed any underturn problems that might have been there initially.

As I said, we all made various tools during our apprenticeship but like most of these special tools, you used them during the course of the apprenticeship but once you got into the real world, you learned to do the job - properly!

If you have too much overturn, which you can, easily, the load of discharge is transmitted through the threads as opposed to the full diameter of the bolt

[gc1054]

The same applied to some No4 bolts, believe me! It's all down to drawing/machine tolerances. But the mere fact that you have bolts that will fit into rifles means that someone in the past(hopefully an Armourer....) will have fixed any underturn problems that might have been there initially.

As I said, we all made various tools during our apprenticeship but like most of these special tools, you used them during the course of the apprenticeship but once you got into the real world, you learned to do the job - properly!

If you have too much overturn, which you can, easily, the load of discharge is transmitted through the threads as opposed to the full diameter of the bolt

Peter,
Thanks.
To potentially wrap this thread up I've got two bolt heads back from the machine shop that were skim cut on the rear shoulder (I decided at the lat minute to send three bolt head to the shop....a scrap one for the shop to use for setup and two usable bolt heads). One under turned by 15 degrees and the other under turned by 40 degrees. The first one had 1.3 thou skimmed off and the second one had 3.9thou skimmed off( this bolt head was long and had a longer shoulder than the first one) Both ended up just a smidge under turned (<5 degrees) and so I carefully polished the bolt head shoulder 600 grit and 1200 grit paper on a surface plate edge and worked the bolt headsI into the bolt body. it took about 30 minutes each but both ended up exactly aligned to the recoil rib with no over or under turn. I've checked CHS and it is good for both bolt heads installed on the new bolt body. Cocking piece lift and striker length are also ok. Bolt assembly installed in the rifle with no troubles and since i put a new (different) cocking piece on this bolt I' m moving on to the trigger pull offs. First results were ok although the second stage pull was 6.5lb and a smidge draggy. Will work to tweak this over the weekend.
Thanks to everyone for their assistance.
GC