No4 Bolt head question

[Claven2]

Anyone know if it is also 16-20 degrees for the No.1MkIII bolt head?

[Peter Laidler]

I think that the permissible bolt head overturn will be the same for both the No1 and the No4. That's because of the need on both rifles that the shock of discharge travels down the length of the bolt head directly onto the longitudinal part of the bolt body and NOT down the threads

[Alan de Enfield]

Anyone know if it is also 16-20 degrees for the No.1MkIII bolt head?

The 1912 and 1931 "Instructions to Armourers" do not appear to quote an acceptable displacement of the bolt head in relation to the bolt - except for -


4. Action:—Bolt and bolt-head.

(i) Test the distance of the bolt from the end of the chamber with gauges .064-inch No. 1 and .074-inch No. 1; the bolt should close over the .064, but not over the .074; when using the latter gauge, light thumb-pressure only should be applied to the knob. Also test to see that the wing of the bolt-head does not lift off the rib of the body.

(ii) Examine the bolt for fracture and damage, especially at the cocking cam and recoil shoulders. Test the striker for free movement and fit in the cocking-piece: gauge the length and radius of the striker point; examine the bents and condition of the cam stud of the cocking-piece.

(iii) Test the fit of the bolt-head in the bolt, and examine the face for erosion; when erosion is excessive or the rib turns beyond the rib of the bolt freely, fit a longer bolt-head and adjust to the 064 gauge as necessary.

(iv) Examine the extractor at the hook and for fit on the screw, and test to see that the screw is secure. Weigh the spring from the hook with the trigger tester - not less than 6 lb. and not more than 9 lb. should be required to move it.

Note.—The bolts of rifles in use should be completely stripped at each annual examination and lubricated lightly with G.S. oil.


Are they talking about the overturn ?

[Peter Laidler]

MMmmmmm. Not quite sure about that. Fitting a longer bolt head? Wsa there a longer one on the No1 rifle in the, say, 20's ? And would fitting a longer bolt head cure the problem?

That's the trouble with the REME tech librarians and the blokes working at the coal face..

They would say things like gently swage the mating surfaces! 'Gently' is a matter of opinion, what's got to be fixed and where you are and as my pal always use to say, who is crying out for the kit you are working on!
Another classic was their keenness to 'ring-punch'. Nobody told them that you could only ring punch something once....... Sterling SMG butt are a good example! Fix it properly or not at all I say!

[Alan de Enfield]

MMmmmmm. Not quite sure about that. Fitting a longer bolt head? Wsa there a longer one on the No1 rifle in the, say, 20's ? And would fitting a longer bolt head cure the problem?

They go on to explain about fitting a 'longer' bolt head (either getting a used one out of the armourers drawer (used bolt heads did not count as a stock requisition) or get a new bolt head and grind down to correctly fit (instructions for grinding down are included in the instructions).

Agree - I cannot see how a longer bolt head alters the bolt overturn - but - another bolt head may/will have a different thread start point.


7. To fit new bolt-head to Rifles No. l.—(Spare part bolt- heads, marked “S” on the top, are longer at the front.) Assemble the bolt-head to the bolt, insert it in the body, and test with .064-inch No. 1 gauge; should the bolt not close over the gauge, remove the bolt-head from the bolt, and having placed a piece of emery cloth (No. F) on a flat surface, rub the face of the bolt-head on the emery cloth, maintaining a circular motion in order to preserve a flat surface, until sufficient metal has been removed to enable the assembled bolt to close over the gauge. The bolt should not close over the .074-inch No. 1 gauge. Care should be taken to keep the-face of the bolt-head flat and square. After fitting and adjusting, the top front edge of the face of the bolt-head is to be rounded to a radius not exceeding .02-inch.


Note.—When it is found that the bolts of several rifles turn over the 074-inch No. 1 gauge, the bolt-heads should be ex- changed among such rifles, as, owing to the varying lengths of bodies and bolts, bolt-heads which are too short in one rifle may be serviceable in another. Bolt-heads that have been replaced in rifles by longer ones, should be kept by the armourer and used whenever possible in rifles requiring the bolt-head replaced, so as to avoid unnecessary use of new spare part bolt-heads. Part-worn bolt-heads held as required by armourers in accordance with the foregoing need not be accounted for as part of the annual allowance of new spare parts.

[Surpmil]

Then there is this appliance: Repro, Bolt Head Wrench for SMLE, Rifles No1 and No2

These are reproduction Wrenches, Bolt Head, for SMLE Series Rifles, Both the .303" Rifle No1 and the .22" Rifle No2.

These substantial tools, cut from 5mm steel plate, are used not for removing or replacing bolt heads as may be imagined, but for fitting new bolt heads, or part worn bolt heads onto new bolts, in a process known as 'tapping up'.

On Lee Enfield rifles the bolt head rotates within the body of the bolt as the bolt is manipulated to open or close the breech - the bolt head being held in position by a machined rib on the right side of the receiver when the bolt rotates as the bolt handle is lifted or forced down by the hand of the firer. When the bolt head is screwed into the bolt it should do up until the extractor lug on the bolt head is in line with the rib (long locking lug) on the body of the bolt. This should be achieved without having to force the bolt head, so that the bolt can fully lock in position when the bolt is closed without excessive force being applied, and unlock again without having to force the bolt handle up. To avoid undue wear and ensure the strength of the bolt when the rifle is fired, the bolt head lug should only just line up with rib, using finger pressure (when the bolt is removed from the rifle) and should not over turn the rib by more than 7 degrees.

New bolt heads, and new bolts, are often shot blasted and phosphated during manufacture, and this coating - along with machining tolerances - frequently mean that a new bolt head (or new bolt) will not quite achieve alignment of the bolt head lug and the bolt rib unless forced. To overcome this without taking a file to the front face of the bolt body (NOT recommended!), this wrench is used after lubricating the threads of the bolt and bolt head, to spin the bolt head into the bolt, then undo the bolt head and repeat the process, until correct alignment is achieved. The spining on of the bolt head both mates the thread surfaces in the bolt body and on the bolt head (similar to grinding in a valve in on an engine) and subtly stretches the threaded portion of the bolt head, until a good finger tight fit is achieved with the correct alignment. This is known as 'tapping up'.

These tools are made for us. Original tools are rare and difficult to find as they were never an issue tool, but were hand made by Armourers as part of their training and as such were never sold off as 'surplus'. Please note that our current stock now has a black painted finish to provide a rust proofed surface for the tool.

[Alan de Enfield]

To avoid undue wear and ensure the strength of the bolt when the rifle is fired, the bolt head lug should only just line up with rib, using finger pressure (when the bolt is removed from the rifle) and should not over turn the rib by more than 7 degrees.

I wonder where the manufacturers of the repro tool got that from ?

[Bruce_in_Oz]

A couple of other things to consider:



The very early versions of the Lee rifle had a separate bolt head, but it was NOT threaded to the bolt body. There was a hardened retaining screw that retained the bolt head. thus NO "helical drive" / movement at that end of the bolt..

All of the "threads" in a No1 and No 4 are right-hand; locking recesses / lugs included..

Looking closely at a closing action, the bolt is cammed forward on the 1:1/10 inch locking helix of the bolt locking lugs and body recesses / surfaces. At the same time, the RH bolt head thread is drawing the bolt head rearward; into the bolt body. If the bolt head thred were LEFT hand, it would be driving the bolt head AWAY from the bolt body as it rotated. The old geezers put quite a bit of thought into their product. There is probably some clever little vegemite out there who has built a 3D animation of this behaviour.

[Alan de Enfield]

Then there is this appliance: Repro, Bolt Head Wrench for SMLE, Rifles No1 and No2

I have spoken with DS solutions asking if he could give me a source for the figure of 7-degrees max overturn for the SMLE.

He is not aware of any documentary evidence where this has been stated, and nor has he seen anything except the 1912 and 1932 Instructions to Armourers where 'the bolt head ahould align with the bolt rib'.

What was interesting was he said there was a bolt head overturn go/no go gauge for the No4, and, he had managed to secure one marked for the SMLE.

His feeling was that this was a mid war relaxtion of the instructions to allow for the 'beaten up' MKIIIs' to remain in service.

Maybe he has a point, and I was grateful for his input.

Thinking about this - I wonder if this aligns with the relaxation of the bolt head / headspace to 0.080" in the 1942 "Army Council Instructions Affecting Armourers"

[Alan de Enfield]

Duplicate post.