Question on tenon size after threading...

[entoptics]

I've run into a problem where my recoil lug won't fit over my tenon on a brand new Savage prefit (not the first time, sadly). No need to mention names at this point, but my question for you smiths is this...

If the nominal diameter is 1 1/16" (1.0625") how big would the tenon be after threading?

My OEM recoil lug is giving me 1.0625" on the nose with my calipers.

2 OEM barrels, and the shot out Shilen I'm replacing, are giving me 1.049-1.050 OD of threads. Recoil lug obviously drops right on these without fuss.

The new barrel I'm trying to install is giving me 1.060" OD, and there's no way I can squeeze the recoil lug down over this diameter with only 2 thousands clearance. The new barrel does thread into the barrel nut and receiver OK, but with a little bit of resistance not felt with OEM or Shilen.

Let's pretend it's irrelevant that this is a "drop in" prefit, and should work with whatever the OEM provides regardless of "nominal", but for arguments sake, assume that "nominal 1 1/16" is the "tenon diameter". I'd always assumed that was the diameter before threading, and the final threaded diameter would be smaller (and that's apparently what Savage and Shilen think), but since I've never done any threading, I guess I have no idea if the OD stays nearly the same during a threading job, or if some material is cut back from the OD of the threads.

What say you?

 

[BillLarson]

if your numbers are correct.... you should have .0025 Clearence...... ???

 

[44-40]

Your measurements are wrong. Cause the. 1.0625" hole will fit easily over a 1.060" shaft or tenon. .0025" clearence will easily fit. The orginal barrel as you measured is out of print for a 1.062× 16 thread at 1.050" ot 1.049" OD if that measurement is even correct.
So if the barrel will thread into your action... without the recoil lug ...thats good. Check for a burr or ding on the recoil lug ID and remove or polish it off.
All ya got to do is open up the recoil lug hole dia..
Or easier you, grab or buy another or new recoil lug 1.0625" hole dia ... it will fit.

 

[grouse]

Do you have a large shank savage barrel? Savage made two tenon sizes

 

[JuddL]

UN imperial screw thread calculator

theoreticalmachinist.com

Great resource for thread specs…machinist handbook is what a lot of folks use too.

Thread micrometers or wires is what you need to measure threads to the degree you're trying. Something is out of spec and based upon your comment about this happening before and the barrel you are questioning threads into the action…I'm going to be odd man out thus far and say it's likely your recoil lug.

But it's hard to tell without having the stuff in hand.

 

[M1A1ABRAMS]

I've run into a problem where my recoil lug won't fit over my tenon on a brand new Savage prefit (not the first time, sadly). No need to mention names at this point, but my question for you smiths is this...

If the nominal diameter is 1 1/16" (1.0625") how big would the tenon be after threading?

My OEM recoil lug is giving me 1.0625" on the nose with my calipers.

2 OEM barrels, and the shot out Shilen I'm replacing, are giving me 1.049-1.050 OD of threads. Recoil lug obviously drops right on these without fuss.

The new barrel I'm trying to install is giving me 1.060" OD, and there's no way I can squeeze the recoil lug down over this diameter with only 2 thousands clearance. The new barrel does thread into the barrel nut and receiver OK, but with a little bit of resistance not felt with OEM or Shilen.

Let's pretend it's irrelevant that this is a "drop in" prefit, and should work with whatever the OEM provides regardless of "nominal", but for arguments sake, assume that "nominal 1 1/16" is the "tenon diameter". I'd always assumed that was the diameter before threading, and the final threaded diameter would be smaller (and that's apparently what Savage and Shilen think), but since I've never done any threading, I guess I have no idea if the OD stays nearly the same during a threading job, or if some material is cut back from the OD of the threads.

What say you?

Is there anyway you could post a few pictures or a short video of what your dealing with. Maybe another set of eyes on what you're dealing with may help better than trying to explain it over the internet. A few of these guys can really dial in on stuff in picts.

 

[DoneNOut]

Do you have a large shank savage barrel? Savage made two tenon sizes

That's like a hotdog down a hallway fit. The threads of a small shank won't even engage in the large shank receiver. I know, I've tried it!

Northland Shooters Supply sells "trued" recoil lugs. They claim to set up Team Savage with their stuff.

@entoptics You could get one of those to try a remedy.

 

[ntsqd]

The first thing to know is that calipers lie to you when measuring the ID of a hole. The smaller the hole, the worse this is. Yesterday we had some tooling at work that was undersize. Starrett electronic calipers claimed the hole was .413", Fowler electronic calipers claimed that the hole was .415", Gauge pins say that the hole is .4245" Note that I don't report or consider the 4th place number that the calipers report - those are worthless because a caliper can not reliably measure that accuracy.
The problem is the shape of the jaws on the caliper. They all have a small flat on the face of the ID jaws. This is a necessary feature, but it does skew their measurements.

If you really need to know the size of the hole you need either an ID micrometer or some skill and a set of snap-gauges with a std. micrometer.

None of which solves the problem. I'd buy an NSS lug and move on. That's assuming that the barrel threads into the action?

 

[ShtrRdy]

I'm not a machinist but it seems you could knock the tops of the threads down a couple thousandths with some Emery cloth.

 

[grouse]

Is this a carbon barrel by chance?

 

[DoneNOut]

I'm not a machinist but it seems you could knock the tops of the threads down a couple thousandths with some Emery cloth.

You know, you are hinting at something with this, although I wouldn't recommend your technique going about this. I am not a machinist either, but when I took a chambering class, Bob Pastor showed me how he uses a setting on the lathe to make the threads flat on top. Illustrating to me on a white board he showed how the "trapezoidal" barrel thread has more surface contact with the V threading channels in the receiver. Putting two Vs together creates issues as the two points wouldn't provide the same mating of the threads.

OP - I managed to condition the threads on a savage shank via use of an Aero P. barrel nut. The nut spun on tight, I needed a towel and channel locks, but when I was done, those threads were proper flat on top and it's been a solid shooter. Just FYI. I know you might not have the exact nut, but hopefully picking up what I'm throwing down!

 

[ShtrRdy]

You know, you are hinting at something with this, although I wouldn't recommend your technique going about this. I am not a machinist either, but when I took a chambering class, Bob Pastor showed me how he uses a setting on the lathe to make the threads flat on top. Illustrating to me on a white board he showed how the "trapezoidal" barrel thread has more surface contact with the V threading channels in the receiver. Putting two Vs together creates issues as the two points wouldn't provide the same mating of the threads.

OP - I managed to condition the threads on a savage shank via use of an Aero P. barrel nut. The nut spun on tight, I needed a towel and channel locks, but when I was done, those threads were proper flat on top and it's been a solid shooter. Just FYI. I know you might not have the exact nut, but hopefully picking up what I'm throwing down!

The way I think about it, there shouldn't be much holding force on the very tips of the threads anyway.

 

[FEENIX]

I've run into a problem where my recoil lug won't fit over my tenon on a brand new Savage prefit (not the first time, sadly). No need to mention names at this point, but my question for you smiths is this...

If the nominal diameter is 1 1/16" (1.0625") how big would the tenon be after threading?

My OEM recoil lug is giving me 1.0625" on the nose with my calipers.

2 OEM barrels, and the shot out Shilen I'm replacing, are giving me 1.049-1.050 OD of threads. Recoil lug obviously drops right on these without fuss.

The new barrel I'm trying to install is giving me 1.060" OD, and there's no way I can squeeze the recoil lug down over this diameter with only 2 thousands clearance. The new barrel does thread into the barrel nut and receiver OK, but with a little bit of resistance not felt with OEM or Shilen.

I agree with others, it should fit.

Let's pretend it's irrelevant that this is a "drop in" prefit, and should work with whatever the OEM provides regardless of "nominal", but for arguments sake, assume that "nominal 1 1/16" is the "tenon diameter". I'd always assumed that was the diameter before threading, and the final threaded diameter would be smaller (and that's apparently what Savage and Shilen think), but since I've never done any threading, I guess I have no idea if the OD stays nearly the same during a threading job, or if some material is cut back from the OD of the threads.

What say you?

I do not like pretending; if you need more ID in a recoil lug, you might give this a try.

http://www.bugholes.com/product-p/bug-lug-1077.htm

They are currently out, but give them a holler and ask them if this can work for you. Good luck!

 

[entoptics]

Remeasured the recoil lug hole, and the problem there is that it's slightly oblong (Savage OEM). The minimum diameter I found is actually 1.059, hence the failure to feed. Thought 0.002 should have allowed it to slide on, but wrote it off to sloppy measuring.

From my googling, a Savage tenon should be 1.055" (for example, Preferred Barrel Blanks) so this one is definitely oversized. As were two previous ones I purchased a couple years back, which wouldn't take a different OEM recoil lug or a EABCO aftermarket one, and one of them wouldn't even thread into the nut/receiver.

Have contacted manufacturer, and won't be doing any DIY fixes till that has gone it's course. The last time they fixed it in a relatively quick turn around.

Regardless, back to my initial question. How much does a standard threading job knock off the OD of a tenon, or is it variable?

EDIT TO ADD: I went ahead and bought another EABCO, which claims it will fit 1.060 tenon. I didn't get one initially, as they will not fit OEM Savage accustock inlet, and I had to modify the first one I purchased. Sorta forgot that this action is going into an XLR Element Mg, which has plenty of space for the oversize lug and tapered sides of the EABCO.

Hopefully, this $40 saves a round trip to the mothership, and is also a nice improvement with the indexing screw and much better uniformity than OEM.