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Gunsmithing bore indicating on a lathe

S

smithy308

Private
Minuteman
Sep 27, 2009
29
0
72
idaho,usa
#1
Hi everyone, I am a newbie here and a newbie to gun smithing... I would like to ask the experienced Smiths of an easy way to center a rifle barrel with a bore test indicator or is there an easier way.. I saw a you tube video of a guy on griz lathe using some kind of a bushing bar inserted into the bore and indicating on the bushing bar..does anyone know where to get that bushing bar? Any tricks? I have used the test indicators and it is darned time consuming to get everything centered that way.. Thanks ahead of time for your input...

mtnsmith
 
#3
Re: bore indicating on a lathe

i have not tried it yet but gordy gritters method makes a lot of sense to me. i use a range rod and two test indicators right now. you can buy the indicating rods from pacific tool and gauge: link. which ever method you choose, you need to make sure to order a bushing kit for the caliber you will be working with. link
 
#4
Re: bore indicating on a lathe

thanks for the info guys.. I am looking forward to hearing from everyone... I don't even have my lathe set up yet as I am building my shop from the ground up..I am doing all of the building myself so it is taking awhile.. I am to the painting stage right now, so it won't be long before I am in, Although my wife and I are taking 10 days off to go down to Front Sight for some fun shooting..

mtnsmith
 
#5
Re: bore indicating on a lathe

Gordy just runs the saddle back and forth instead of using two indicators. Saves him about $170.
wink.gif


I use the range rod and a dial indicator initially. Once I get close I switch to the test indicators. I find that using the dial indicator initially saves time, as it has a greater range.

As I found out the hard way recently, it also helps to have indicator rods available when you have a learning experience. The difference in the taper is small, but makes a big difference when indicating a chambered barrel.
 
#6
Re: bore indicating on a lathe

what i did to speed up my process was to use a .001 dial indicator and dial both ends of the barrel's od to .001" or better. this only takes a few minutes and gives me a pretty good head start on dialing in the bore. then i place the range rod and fitted bushing in the bore at end i am working on. i only use one indicator now with the magnetic base on my cross slide. i put the .001 indicator as close to the barrel as i can get it and dial it in with the chuck. i move the indicator to the end of the rod and dial it in with the spider. back and forth a few times gets me to better than .001" in both spots. now i switch out to my .0001" mitatoyo indicator and do the same thing. the last one i did took less than 10 minutes total to dial the bore in to .0001" or better in two spots on the range rod. now i am down from a few hours it took to dial in my first barrel to 10-30 minutes of set up time per side.
 
#7
Re: bore indicating on a lathe

There are several wasy to do it but, I beleive this is the most used method. After the initial dial in is complete, I switch to a Brown & Sharp .0001" Last Word indicator for the final dial in.

juiicm.jpg


wum6g9.jpg


The same holds true when blueprinting receivers unless you’re trying to save $100.00, then you can use the Manson Tap/Reamer method. All truing cuts should be made by the "Single Point Method" in a lathe if precision work is desired. You can’t hold tolerances of .0002" or better with piloted tools or taps.

k2jxi1.jpg


 
#8
Re: bore indicating on a lathe

I just did (3) 7mmMag chambers and threads in 4 days.
Two were for practice on my new lathe [4th lathe purchase in 10 years]. The 3rd barrel I may be hunting with this year.

1) One Rem700 Chrome Moly take $33 Ebay [plus shipping] off barrel onto a 1908 Brazilian M98
2) One WinM70 Stainless $14 Ebay [plus shipping] take off barrel onto a 1908 Brazilian M98.
3) One Lothar Walther Chrome moly 1300 taper blank $235 retail [plus shipping] barrel onto a VZ24 Brazilian M98.

The take off barrels got the threads cut off, and then a test indicator put into the chamber.
The stylus would only reach 3/8" inch into the remaining chamber, and so I indicated 3/8" in AND at the orifice. I used the left side spider to cant the barrel in the AWG#10 copper wire forming a gimbal in the right side 4 jaw chuck.

All I could hope to do was get concentric and parallel with the original factory chamber.
1) When I was done, the Rem barrel was withing .0050" of the lathe. The burr from cutting the threads off got the reamer eccentric, and the pilot never steered it straight again in 1" of reaming.
2) When the Win barrel was done, it was within .0005" of the lathe. I de burred the burr from the cut off tool.

3) The Lothar Walther was a virgin blank.
I ordered a Vermont Gauge .2765 - " pin gauge 2" long.
With 3/4" protruding, I could get the barrel dialed in to within .0002" both where the pin just enters the barrel AND at the end of the pin.

I went into a mode of 29/64ths" drill [.453" dia] 1/2" deep, boring bar 1/2" deep until the chamber was .475", I would de bur the drill hole, followed by the 7mmMag reamer 1/2" deep with the .490" shoulder.
I repeated for 1" deep, I repeated for 1.5" deep, and then I finished reaming to 1.9" deep.
When I was done the chamber was within .0007" of the lathe.

4) We chambered a Lothar Walther 257RAI 2300 taper barrel for me 10 years ago that finished at .0010". That rifle averages .8" 5 shot groups @100mters with 72 gr Bergers or 75 gr Vmax, and has shot .45" groups.
10 years ago we were dialing in the left side spider with a test indicator in the muzzle on the left side.
Since then I spoke with Randy Ketchum, who has done benchrest gunsmithing. He tool post grinds a spud to within .0002" of the bore, and uses the muzzle to cant the length of the barrel until the breech dials in not only concentric but parallel. He says that all barrels are bent, and have a spine, or high spot in the middle. He says the important thing is to get the throat cut concentric and parallel to the bore locally.




 
#9
Re: bore indicating on a lathe

Clark, neck time indicate off the bore, not the existing chamber or any part of it. You'll never know where the existing chamber is in relation to the bore if you don’t. Get the bore running at least .0002" or better then touch off with a small boring bar in the existing chamber at its shoulder/body juncture point to just make it round and concentric to the bore dial in. This will help your reamer start straight giving it a concentric path to follow.

You got close but <span style="font-weight: bold">"When I was done the chamber was within .0007" of the lathe."</span> You're closer to .001" than .0002"
 
#10
Re: bore indicating on a lathe

wnroscoe,
I like your posts and your web site.

If I cut off enough of the old chamber to get at the bore, there is not enough barrel diameter left for a shoulder or even threads.

These old take off barrels are sporting tapers, not sniper bull barrels.

My brother bought an old Rem700 30-06 for $75 that shoots 1" groups. Some factory barrels must have been done right.
Those rifles I indicated on the chamber might shoot well.
It could happen:)
 
#11
Re: bore indicating on a lathe

Thanks, as long as we learn something in our efforts it wasnt in vain, good luck. I'm sure the barrels will shoot fine, they're bound to be better than they were.
 
#12
Re: bore indicating on a lathe

Just to make it clear the dial indictor must be moved near the barrel then out on the tip of the rod, or you need to use two indicators. One indicator monitors the chuck end and the other is for the spider end. Dialing in the barrel with just the indicator at one location is going to cause you issues.
 
#13
Re: bore indicating on a lathe

hey roscoe, i meant to ask this once before but forgot. what is the finish on your action truing jig? did you do that for some bling or was the material left from something else.
 
#14
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 300sniper</div><div class="ubbcode-body">hey roscoe, i meant to ask this once before but forgot. what is the finish on your action truing jig? did you do that for some bling or was the material left from something else. </div></div>

I was just playing around one day and stretched the plastic barrel wrap over it and shot it with fine glass beads. Bling Bling
 
#15
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">Just to make it clear the dial indictor most be move near the barrel then out on the tip or the rod, or you need to use two indicators. One indicator monitors the chuck end and the other is for the spider end. Dialing in the barrel with just the indicator at one location is going to cause you issues. </div></div>

I knew that
wink.gif
 
#17
Re: bore indicating on a lathe

Wnroscoe,can you post a few pics of action thruing jig. I have a similar one to the GTR/your is intersting in that it looks a lot smaller and the bolts look very close together. I made one which I bolted onto a backplate,maybe I shouldnt have gone to so much trouble.
 
#18
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gamma</div><div class="ubbcode-body">Wnroscoe,can you post a few pics of action thruing jig. I have a similar one to the GTR/your is intersting in that it looks a lot smaller and the bolts look very close together. I made one which I bolted onto a backplate,maybe I shouldnt have gone to so much trouble. </div></div>

http://www.louisianaprecisionrifles.com/blueprinting.aspx
 
#20
Re: bore indicating on a lathe

I went to the range with the 3 Mauser rifles with the cut up VZ24 stocks, the same type bedding job in place of the recoil lug, the same type of scope mount bedded in the same way, the same 8 pound weight before scope, the same 25X scope swapped from rifle to rifle, and the same 162 gr 7mmMag ammo.

Rem700 take off barrel chamber finished .0050" off lathe center:
0.75 moa at 100y

Win M70 take off barrel chamber finished .0005" off lathe center:
2.00 moa at 100y

Lothar Walther 1300 taper barrel blank finished .0007" off lathe center:
0.77 moa at 100y

The only way I can rationalize an eccentric chamber shooting as well as a concentric chamber is that the bullet gets thrown by centrifugal force in a consistently the same radial direction every time. This would be unlike eccentric ammo, which would throw it radially in a random direction.
 
#21
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">I went to the range with the 3 Mauser rifles with the cut up VZ24 stocks, the same type bedding job in place of the recoil lug, the same type of scope mount bedded in the same way, the same 8 pound weight before scope, the same 25X scope swapped from rifle to rifle, and the same 162 gr 7mmMag ammo.

Rem700 take off barrel chamber finished .0050" off lathe center:
0.75 moa at 100y

Win M70 take off barrel chamber finished .0005" off lathe center:
2.00 moa at 100y

Lothar Walther 1300 taper barrel blank finished .0007" off lathe center:
0.77 moa at 100y

The only way I can rationalize an eccentric chamber shooting as well as a concentric chamber is that the bullet gets thrown by centrifugal force in a consistently the same radial direction every time. This would be unlike eccentric ammo, which would throw it radially in a random direction. </div></div>

Problem is the barrels are neither the same nor the rifles the same so I would expect different results even if they were chambered exactly the same. You would have other issues then just accuracy with your off center chamber jobs.

Accuracy is not the only issue with chambering a barrel that has not been properly indicated in the lathe. You will get excessive or uneven throat wear, screwed up brass, and a whole list of other issues.
 
#22
Re: bore indicating on a lathe

wnroscoe I chamber my barrels exactly like you do but some rifle builders chuck the muzzle in a 3 jaw and use a live center for the tennon and threads then a steady rest for the chamber. Is one way more accurate or just preference. Thanks, SPM
 
#23
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SPM</div><div class="ubbcode-body">wnroscoe I chamber my barrels exactly like you do but some rifle builders chuck the muzzle in a 3 jaw and use a live center for the tennon and threads then a steady rest for the chamber. Is one way more accurate or just preference. Thanks, SPM </div></div>

Think about this, the barrel is chucked at the muzzle and running in a live center that’s in the tail stock. A skim cut is made on the OD of the breech for the entire length of the flat and then a steady rest is installed. Yes, the barrel is now running at what appears to be true but, what is the bore doing in relation to the OD of the barrel. How can we adjust the bore for the deep hole drilling (Gun Drilling) issues that occurred during the rifling process? The problem is this, the bore will never run dead true with the blank with Gun Drilling and will always be on a different center line when compared to the OD of the barrel.

Indicating with a Range Rod at the breech in a four Jaw or Buck Chuck and using a Spider at the muzzle allows us to align the bore and make corrections for the Gun Drilling issues. Indicating the bore is in my opinion the only true way to chamber a rifle barrel if you desire a precision job. There are those that use a long stemmed indicator in lieu of a range rod and pre-drill, taper bore then chamber. This is also an excepted method for precision work.
 
#24
Re: bore indicating on a lathe

SPM,

In my experience, there is no way to truly get an accurate "dial in" by the method you are describing with the 3 jaw and tail stock..... just too many chance for errors. In my opinion, there is NO substitue for using the 4 jaw and spider with a last word indicator. The reason I say that is this, Even if the 3 jaw was dialed in perfectly, very few barrels , if any have an OD that is true to the ID. If you were to chuck or "indicate" by using the chuck on the OD of the barrel, you would be off by what ever the variance is between the two. If you used a "pilot" and inserted it in the bore and then chucked to it, you would be alot closer but as I said above, the three jaws are nowhere as accurate as dialing something in with a 4 jaw and a last word indicator....at least in my experiences.....

Whether you use the Range rod or indicating rod method is more of a preference but running the barrel through the headstock is THE only way in my mind to get an accurate "dial in" and a good straight chamber.


Edit to add:

I guess I was typing when Roscoe posted. I think he described it as good or better than I did...sorry for the redundant info...

 
#25
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"> You will get excessive or uneven throat wear
</div></div>

All three throats were virgins.
 
#26
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"> You will get excessive or uneven throat wear
</div></div>

All three throats were virgins. </div></div>

Makes no difference, all three barrels are still different.

If you chamber a barrel that isn't indicated properly you can and will get an out of round chamber which in turn will give you an out of round throat which can and will lead to excessive and uneven throat wear, makes no difference if they are virgins or not.
 
#27
Re: bore indicating on a lathe

Thanks wnroscoe and gunjunkie, thats what I thought but not being a "true rifle builder", just for myself, I couldn't understand why people do it that way. I'm not trying to bash anybody because it apparently works for them. It would be cool if one of you smiths would chamber the barrel one way and see how it shoots and rechamber the other way and compare. That would be a test I would help fund and bet others on here as well would. Thanks again, SPM
 
#28
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SPM</div><div class="ubbcode-body">Thanks wnroscoe and gunjunkie, thats what I thought but not being a "true rifle builder", just for myself, I couldn't understand why people do it that way. I'm not trying to bash anybody because it apparently works for them. It would be cool if one of you smiths would chamber the barrel one way and see how it shoots and rechamber the other way and compare. That would be a test I would help fund and bet others on here as well would. Thanks again, SPM </div></div>

I've done it both ways just for the what if factor. It can be done but its a little disconcerting to watch the chamber reamer wobble with the barrel run-out as you feed the reamer into the barrel. At the very least you are going to get an out of round chamber. If you have lots of run-out this can be dangerous when you touch off the round. You will have screwed up brass. Your throat will wear excessively and unevenly.

Will the rifle shoot? Yes, have seen them shoot very well, but like I said you will get premature barrel wear and screwed up brass, and a few other things that I haven't mentioned.

There's really no need to have a smith chamber a barrel this way, just go buy a factory Remington rifle. Almost every one of those chambers are not centered and have run-out, some of them shoot very well and some don't.
 
#29
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"> .. It can be done but its a little disconcerting to watch the chamber reamer wobble with the barrel run-out as you feed the reamer into the barrel. ..

Will the rifle shoot? Yes, have seen them shoot very well,..</div></div>

I saw the wobble last week.
The tap wrench was rubbing a circular pattern on my crossfeed.
A little disconcerting?

And then it shot well this week.
That was just puzzling.
 
#30
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"> .. It can be done but its a little disconcerting to watch the chamber reamer wobble with the barrel run-out as you feed the reamer into the barrel. ..

Will the rifle shoot? Yes, have seen them shoot very well,..</div></div>

I saw the wobble last week.
The tap wrench was rubbing a circular pattern on my crossfeed.
A little disconcerting?

And then it shot well this week.
That was just puzzling.
</div></div>

But how does the fired brass look?

Is it buldged in the rear?

How does it extract?

Why not cut as straight a chamber as possible without the reamer wobble?
 
#31
Re: bore indicating on a lathe

I had a $33 Ebay Rem700 7mmMag take off barrel I was practicing on.
I cut off the threads with a parting tool.
I dialed in to .0005" with the test indicator on the existing remaining chamber very close to the orifice, AND the 3/8" in that the test indicator would reach. I manipulated the left side spider so that both the breech orifice and 3/8" in were concentric with the lathe at the same time.
I put the 7mm Mag reamer in the hole and started chambering, but the burr from the parting tool got it .005" off center and it stayed that way all for the ~3/4" deeper I was making the chamber. It never straightened out. I put the test indicator in the chamber when it was done, and it measured .005" run out.
The process was disappointing, but the rifle surprised me with good groups.

The next practice barrel was a $14 Ebay Win 70 take off barrel that I cut off the threads.
I then de burred the the hole with a 4 flute 90 degree countersink in tail stock.
That barrel ran true for the ~ 3/4" of reaming.
I tested the chamber 10 times truer, but that rifle did not shoot well.

What I was practicing for was an expensive Lothar Walther blank, that I cut the whole chamber, and it ran true AND shot well.

The first two practice rifles will get put in storage and probably never shot again.
I am trying to get the third ready for antelope next week.

I have now done 23 rebarrelings in 7 years, all on my own guns. I am not doing professional quality work like you, but I am getting better.

 
#32
Re: bore indicating on a lathe

Clark,

Try this. Cut off threads, indicate the barrel in by the bore. Take a small boring bar and just clean up the remaining chamber/shoulder area to make it concentric to the bore. Dont take off too much, just a clean up. This will give your reamer a straight hole to start in and follow. Taper boring would be best.
 
#33
Re: bore indicating on a lathe

I indicate off a pin gauge in the bore with a test indicator.
The pin guages are 2" long and only stick out 1".
The test indicator stylus only reaches 3/8".

I might cut off the threads and indicate on the bore of a 6mmBR, but not a 7mmMag.
 
#35
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body">
SPM said:
its a little disconcerting to watch the chamber reamer wobble with the barrel run-out as you feed the reamer into the barrel.
</div></div>

Freekin wobbling reamers. Just spit coffee on the keyboard.


Wobbling reamers give you wobblegated holes.

Mr Roscoe, does my .223 have a wobblegated chamber? Is that your secret to making them shoot so good?
grin.gif



Trilogymac
Click to expand...
 
#36
Re: bore indicating on a lathe

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: trilogymac</div><div class="ubbcode-body">Mr Roscoe, does my .223 have a wobblegated chamber? Is that your secret to making them shoot so good?
grin.gif

Trilogymac </div></div>

Wobblegated chambers are an extra charge, as you didnt pay for that option I provided you with a straight chamber.
 
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