Hi I was going through Kuhnhausens shop manual for Mauser and came across his tool for lapping the primary torque shoulder on Pg. 163, Fig. 193.

Came you purchase this tool anywhere? If not it looks east to fabricate one. Where would a person get a diamond abrasive head to use? (looking at the picture kind of looks like a take off barrel stub)

Do many of you do the facing of the Primary torque shoulder in the making of a rifle?

Thanks for your time, input, and help in this matter

I do not reface it unless I am going to reharden. And yes, a barrel stub is a fine way to go as long as you keep everything square when you bore the chamber out. You can make the "diamond" with just some 0-1 "Washers" hardened and some clover compound.

Once the action is set up on a mandrel use a tenths indicator (.0001" type) and check it for run out. I personally allow no more then .0005" before I will face it off.

FYI The other thing is the Lap should be soft not hard. This allows the grit to bight into the lap and stick there while you are lapping the face. If you use a hard lap the grit will stick into the softer material and lap the harder face.

Any time you lap or hone anything with a paste or compound on a lap or other surface that surface must be softer then the part being finished or your surfacing will work in reverse.

quote:

Originally posted by kcstott:
I personally allow no more then .0005" before I will face it off.

You consider .0006 a deal breaker do you?

Build every rifle as accurately as you possibly can then the only thing you have to blame is your self. For what it's worth I'm a tool maker I work to these tolerances daily.

But lets be realistic here. If a rifle came in at say .0007" then it would come down to the end use of the rifle. Big bores don't need that kind of precision.

But all things being equal if you start out with a high precision platform then the end result will be far and above what you'd expect. and it doesn't necessarily take that much longer to do.

But you must take into consideration the face of the barrel as well as this will crush into the seat and if the face of the barrel is out or the threads are not square to the axis of the action well you're fighting an uphill battle.

quote:

Originally posted by kcstott:
Build every rifle as accurately as you possibly can then the only thing you have to blame is your self. and it doesn't necessarily take that much longer to do.

This is one requirement for 'best' work; building it the best way you know.
Regards, Joe

I think you guys have the wrong idea. If what I believe Siam-Krag is referring to is lapping the compression shoulder and not the receiver ring face. If memory servers, it often don’t anymore, this is the tool pictured in Jerry’s book. It uses a FIXED diamond lap.

quote:

Originally posted by kcstott:
I personally allow no more then .0005" before I will face it off.

I got to ask! If you are going with only .005 run out what are you using as a reference? You have the compression shoulder, bore centerline and threads. The only way to check for run out would be to spin between centers and that would mandate having a mandrel which would centerline the bore and make the threads impossible to measure run out. With a proper register the compression ring would be dead nuts and not be measurable as well. If you are cutting a new face on the ring then it would not matter what run out it had as it would be null after the cut.

Face the front ring square and seat the barrel against it. Leave the back of the barrel .005" short from the inner ring and don't bother with it any more.

quote:

Originally posted by Big Earl:

quote:

Originally posted by kcstott:
I personally allow no more then .0005" before I will face it off.

I got to ask! If you are going with only .005 run out what are you using as a reference? You have the compression shoulder, bore centerline and threads. The only way to check for run out would be to spin between centers and that would mandate having a mandrel which would centerline the bore and make the threads impossible to measure run out. With a proper register the compression ring would be dead nuts and not be measurable as well. If you are cutting a new face on the ring then it would not matter what run out it had as it would be null after the cut.

For one it's .0005" not .005" Big difference here.

Two I don't use a store bought mandrel to set up my actions on. Yes you are correct in the sense that if I used a threaded mandrel how could I take a measurement of the secondary shoulder? The mandrel is in the way. Correct! But I don't use a standard mandrel I use a precision test bar that I made to set up my actions on. and as needed I will make others to suite other actions.
What I do is set the action up essentially between centers as you stated. I do this in my lathe after indicating the tail stock true to center as a double check.

With a bar that is center drilled on one end, I place one end of the bar in a four jaw chuck and indicate in to zero on a tenths indicator. I then bring the tail stock with live center into contact with the center drilled spot on the opposite end of the test bar.
I then indicate that end as well and adjust the pressure on the tail stock to get as close to zero as possible. I shoot for less then +/-.0001". Sometimes this is not possible but that is the over all length of the action so +/-.0003" run out over eight to ten inches is not bad at all when all I'm looking for is +/-.00025" over .990"(the minor diameter of the threads give or take a bit I'm calling that number off the top of my head so don't quote me on it) Then I measure with gauge pins the bolt thru hole diameter and cut the test bar to fit with a mild press fit into the action.

This assures me that everything from there on out is referenced off of the bolt bore or the true center line axis of the action.
At this point it's a pain but it can be done with the right indicator and some very careful positioning get that indicator tip down in the front receiver ring. Sometimes I've left the test bar just shy of coming through the action and indicated this way as it is much easier to do but you must have an absolute rigid test bar or just the weight of the action alone will cause the bar to sag enough to cause a misread on the indicator.

at this point you can then face the primary and secondary shoulder if needed, chase the threads if needed, and with the proper tool face the bolt lug bearing surface all in one setup.

I still don't believe that face the receiver ring will automatically eliminate the internal shoulders run out.

This rifle was designed to that both shoulders seated on the barrel at the same time with a little more pressure on the inner shoulder. this also gives the proper amount bearing area to support the breach face.

Now all this said some may feel it is over kill. Well maybe but I'm a firm believer in knowing where something is in relation to everything else. If you don't at least check, you don't know for sure. And I'm setting the action up anyway to to true the faces so i may as well take some extra time to get to the gnat's ass

I also don't believe in leaving the inner shoulder out of contact with the barrel. I feel this is a big mistake and severely reduces the bite the barrel has on the receiver. Some may say it's OK but I believe Paul Mauser knew what he was doing so I won't second guess him on this.

Alright, let me get this straight. Lathe set up correctly, check. You mildly press a tapered mandrel into the action and with nine inches hanging out of your four jaw, you can cut a new compression shoulder, receiver ring and re-thread it? All while maintaining .0005” tits? And you can do this with a heavy ten?

Pardon me if I seem a bit skeptical, it’s just my nature. I went for a second opinion with my in-house, seasoned machinist and barrel fitter and explained your set up to him. Told him you were using a miniature version of his lathe and hold half a thou asked for an opinion:

quote:

Face the front ring square and seat the barrel against it. Leave the back of the barrel .005" short from the inner ring and don't bother with it any more.

You are right, however, Proper fitting to a Mauser is between .002” and .003’ compression between the face and compression ring. I seriously doubt if many guys do this and I really do not think it matters much. I do it but it’s not extra work, it’s just doing the right math, minding the DRO and taking the proper measurements.

quote:

Originally posted by Big Earl:
Alright, let me get this straight. Lathe set up correctly, check. You mildly press a tapered mandrel into the action and with nine inches hanging out of your four jaw, you can cut a new compression shoulder, receiver ring and re-thread it? All while maintaining .0005” tits? And you can do this with a heavy ten?

Pardon me if I seem a bit skeptical, it’s just my nature.

I have no dog in this fight so no attempt at throwing gas on a fire. Just a simple question, "Is there a reason a ‘heavy ten’ cannot maintain these tolerances?"

Jim,
No fight here, I think all the egos are still stewing over bolt handle welding. KC’s first post got my head to thinking and I felt I best either learn something new or share that pain a wee bit. There is no reason why a Heavy ten cannot hold those tolerances. There is no reason that a Wal-Mart Mossberg can’t shoot ¼” with Chinese ammo or my wife cannot cook like Martha Steward. The Heavy tens are good solid lathes and capable of some of the best performance in their class, they are just not Tool room lathes. Even in S-B sales litature they specified one thou and in the old reel to reel’s they promoted this as well. With the chucked mandrel KC mentioned, unsupported and with a 5 pound payload (Action + mandrel) sticking out 9 inches I cannot phantom holding .0005” when the belts spun.
Currently of my nine lathes I have three S-B’s and two will make it to the new shop. I have owned over three dozen of them over the years and have done two collar test on at least half of them as well as several other S-B’s. Your Harrison AA and Monarch EE will typically hold this close but they both have balanced spindles. With all new bearings and fresh ground spindle the heavy ten might be close to holding this, or might not. Kind of hit or miss. I would not scrap a Mauser action because it was off .0005” on any dimension. I have seen the Nardini and Misel operations in person and have talked with some of their best engineers and sales people (I married one) and they can hold up to those tolerances, but again, we are talking tool room lathes. The Nardini’s started at over 16 grand back then and are some fine machines. I have been in contact with Shiraz Balolia and given my ideas on the new 2011 S-B heavy tens he will be bringing out and have been assured by him that they will have Meehanite ways and be ground to higher tolerances than the original. These should hold close tolerances but I doubt they could do so with 9 inches of unsupported weight hanging out of a chuck.

Thanks Big Earl, very informative post. I like gadgets but heavy machinery is well beyond my capabilities. Again thanks.

Earl
Lets put it this way.
I'm fighting a very steep up hill battle on my machine to get it to hold that close.
But it can be done with a little finesse and a little practice.
My lathe is a wee bit tighter then most but as stated it's no tool room lathe. And to be quit honest sometimes no matter what I do to change the set up it just won't get that close. Now as I don't have a set of bench centers the question begs is it my machine or the action?

Now please keep in mind I'm not saying you can just walk up to any old machine... toss in you action and indicate it in. Far from the truth there. You are skeptical for good reason. It's a BITCH pure an simple to get it that damn close but it can be done. And because it is not easy I would assume a lot of people choose not to bother with it.

With the greatest of respect this seems like a nonsensical argument.

If you take an average lathe with an 24" drive chain, 6" of chuck depth and a 9" job.

The linear expansion of steel on average is, 11 x 10 to the power of minus 6 x temp change in degrees Celsius. Over 39" that equals=.000429" per degree C temp change.

So it doesn't matter what lathe you run or how good you are, it comes down to the climate control in the building. Just warming up the machine will have 0.0001 tolerances all to cock in a minute.
If you just take a 10" piece of steel and lay it on the bench its length will move circa 0.0001 per degree Celsius of temp change.
And none of this factors in the changes in the measuring instrument itself.

Regards

That's all well and good but we are not dealing with the expansion of the machine, Part, or indicator.
All I care about is how far from zero does the part read on the indicator. Yes as things heat up it will change but it will not affect run out to a great degree. Yes the part will get larger and longer but it will not double the run out.

Example
Take a piece of steel chucked in the lathe.
And lets assume that this piece of steel is 2" in diameter and as near perfectly round as we can measure. The OD is running true in concentricity and angularity to the spindle axis.
But the face is not square to the diameter. So the face wobbles a bit. and say it wobbles .005" and lets also say that it's a nice California day so the temp is 22 degrees C and a One degree change in temp would then equate to .000022" change in diameter. 22 millionths of an inch???? I'm not to worried about something I can't measure.

So I would just call that nil in 99% of the cases. It may matter for rocket parts but not on a rifle.

So you get .0005 run out? OK, I won’t argue what you can do. Most new machines won’t do this but to be fair to the S-B, It does have an extremely strong and wide spindle and the S-B “superfinish” is considered one of the best. It also has some out sized bearings and with an excellent quality chuck would allow you to get awfully tight tolerances. You might want to save yourself some time and aggravation and pick up a collets attachment and at least one (5/8”) Lydex collet. One of these is of more value than a bucket full of cheap collets. If you grind your mandrel between centers this set up will give you about as best chance for null run out as can be achieved. If you are interested in a nice electronic bench center I have an extra I will let go cheap.

Earl
The key here is the use of a four jaw chuck and very precise positioning of the mandrel.

If the spindle is running out this can be corrected by the four jaw chuck Where as a collet can not. I have a good collection of Hardinge 5C collets and an original SB spindle adapter.

Once again i'll say One it might be over kill. and two it doesn't work every time but given a bit of time to play with things I can compensate for the run out of the spindle and any variation in the mandrel. You just have to know what to do.

Oh and you mandrel should be made of good quality tool steel Preferable prehardened P-20 this is the most stable stuff around if you lack a heat treat furnace. Machines nice and finishes well.
Now The spindle on my machine runs out about .001" and with the four jaw chuck set up I can dial it down to where I think my indicator is broke because sometimes the needle doesn't even twitch. And I'm using a brown and sharp best test tenths indicator.

What I'm tryto say here is when you set up an action and your indicator shows .0005" or less O consider that to be zero in my book when it comes to actions. We aren't building dies here so a few tenths here or there is dead on as far as I'm concerned. But back to my original statement.
I said If the action runs out more then .0005" I would face the surface. And that is true for the most part. Like I said it really depends on what the end result is expected to be.
Keep in mind I only work on My own stuff or for friends I'm not a Gunsmith by trade. I'm a tool maker that just so happens to have a rather well equipped garage. So.... One I'm not in this to make money.... Two I haven't played with enough action to say that this is even necessary or not. It's just that way I do things.

If the rifle is going to be used as a varmint rifle, a tack driver, a Sniper weapon system. I want it built to the highest degree possible in term of accuracy and precision. If it is going to be a general purpose hunting rifle. Then you can loosen up the tolerances a bit. If it is going to be a big bore Or a DG rifle then MOA accuracy is not needed and those tolerances can be loosened up further But On that same hand the last two rifles need to be reliable more then accurate especially the last one. I'd take a any DG rifle that can hold a 4" and function without failure. then one that can hold 1.5 MOA but screw up every few rounds.

It all depends on what you are building.

quote:

Originally posted by kcstott:
Build every rifle as accurately as you possibly can then the only thing you have to blame is your self.

quote:

Originally posted by kcstott:
If the rifle is going to be used as a varmint rifle, a tack driver, a Sniper weapon system. I want it built to the highest degree possible in term of accuracy and precision. If it is going to be a general purpose hunting rifle. Then you can loosen up the tolerances a bit. If it is going to be a big bore Or a DG rifle then MOA accuracy is not needed and those tolerances can be loosened up further...

Just curious which it is, do you build them all as accurately as you can, or, just certain ones? Seems to me that a DGR requires nothing less than maximum performance and precision. Don't lose sight of the fact that big bullets still miss their mark as easily as little ones.

I got to admit I have never understood that reasoning as well. I can build an accurate big bore as easily as a varmint rifle and just as reliable, just like anyone else. I might not be able to shoot it as well, but that is a rather moot point. When I open my eyes the bullet is at least downrange and in the paper. Accuracy has to do with a lot of factors and none of which (In a sporting rifle) are derogatory to reliability. That is not directed twards you KC, just a general idea on a subject that seems to show up at times.

Here's the deal
If my brother brought over his Eddystone 1917 Enfield and said Re barrel it.
Would you spend the time to fully blueprint, lap and hone the action? I'm sure as hell not. Not unless that what he want and is paying for.

Yes I made a very blanket and general statement by saying build every rifle as accurate as you possibly can. What I should have said was Build it as accurately as you can within reason.

now let me explain my way of thinking on big bores and DGR's
and by definition I mean .375 H&H and up.

I'm not going to expect a .375 to hold MOA or less off the bench or other wise. as that's not what it was intended for nor what I'll use it for. If that rifle can hold 2" at 100 yards I'd be damn happy with it. Now I'm sure there are more then a few .375's out there that can do this day in day out.
But how about .416 Rigby?

Now the Rigby may also be able to hold at or near one MOA but there again I'm not expecting it to nor will I be disappointed if it doesn't. As it will be used to hit the vital area twice the size I'm use to shooting at and maybe larger still. So if I was to build a Rigby and the Primary torque shoulder was running out say one thou' then no I wouldn't face it off. More then that and yes simply because you need at least two thou" of crush on the barrel and if your run out is more then half of the crush dimension then that's not good fitting at all.
And the chamber needs not be tight as on a precision rifle and it may make the rifle unreliable and even dangerous to use if your life is on the line.
A DGR in my opinion should chamber a round damn near ever time without failure aside from just plain extraordinary circumstances. Like a barrel full of mud or a action full of dirt or dirty ammo.

And really this has all been enlightening to me as it made me take a closer look at my procedures and re examine how I do things.

quote:

Originally posted by Big Earl: Accuracy has to do with a lot of factors and none of which (In a sporting rifle) are derogatory to reliability.

I disagree. Would you want a tight chamber on a DGR?

quote:

Originally posted by JBrown:

quote:

Originally posted by Big Earl: Accuracy has to do with a lot of factors and none of which (In a sporting rifle) are derogatory to reliability.

I disagree. Would you want a tight chamber on a DGR?

That is one point I was getting at.

Military and DGR's and others are built on the loose side of the chamber dimension to facilitate ease of chambering and extraction.

And a loose chamber doesn't do a damn thing to improve accuracy

And ANYONE who doesn't run each & every one of his cartridges through his 'DGR' to check for function before he goes into the bush, well....
Regards, Joe

DGR are do not employ tight chambers because function and reliability are more important than extreme accuracy and case life.

Tight chambers are unnecessary for the application, the rifle is built to function with most any ammo including replacement or dirty cartridges.

Chambering a DGR to benchrest specs is machine shop masturbation.

Jason,
Tight? You mean below SAAMI? To the best of my knowledge I have never chambered a barrel below that and suspect never will. No problem if anyone else wants to. With the exception of half a dozen wildcats I designed and two others, I have either ordered stock reamers from Elliot, Manson or Kiff or just went with store bought from Midway or Brownells. All of these are advertised at “minimum dimension” and I have never had any issue with reliability or accuracy. To be quite honest, I consider concentricity and quality of cut and finish too be more desirable that minor dimensions. If you have a rifle, any rifle, and it won’t group less than 4 inches due to the chamber, there are some issues with the chamber. DGR rifles do not need to be inaccurate to shoot reliably. A well cut “standard” sized chamber ought to shoot well and function without issues.
I also do not believe that a tight chamber is required to get accuracy. Most of the guys who talk about this are referring to bench rifles and not hunting rifles and from what I have gathered the philosophy tends to be more of a need to match chamber with dies. Possibly I am wrong, but I don’t think so.
My personal “Happy Medium” I built in ’03 took its first and fortieth head of game in south Zim that same year during September/October. The temp was to 120 degrees every day by noon and often by 10 am. The rifles baked in the truck rack, were carried all day and never cleaned until after the three week hunt. The metal was so dam hot it could not be touched but for a moment and the shooting was pretty heavy. This chamber was cut with a minimum dimension Manson reamer and the brass only neck sized. Thermal dimension changes? Nope, no problems what so ever. Two years later I hunted wildebeest in a sleet storm with the same rifle, action frosted over. Again, no problems and one inch groups are pretty much standard. This is a sporting rifle.