Cutting True Center

L

Lucky Shooter A

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Someone had posted about an easy way to cut a true center with a center drill.

I looked for this but didn't find it.

The method involved pulling/pushing on the tail stock as I recall.

Will appreciate any info on this.

A. Weldy
 
no tail stock is ever at true center for the length of the bed. it can be set at one specific place each time. move it and lose it.
 
My tail stock is about .003" high. If I extend the unlocked quill 2 or 3 inches, a small, sharp center drill, fed slowly, will cut a center with no run out in a smoothly faced work piece in the chuck. The rotating work piece tends to force the drill towards center and the quill's flexibility allows it. I have done this many times and it always works in alum. and brass and most of the time in steel. This might be the reason a gun drill rotates the barrel blank as well as the drill, but I am speculating. YMMV.

RWO
 
You can drill with the center drill, then use a small boring bar with the compound set at 60* to take a light skim cut. That will give you a true center.
 
Issues

I'm not having any issues.

Have been cleaning up with a boring bar----no problems with this.

The method I read about-----as I recall----sounded like a quicker
and easier method and I just wanted to revisit it.

Thanks for all the replies.

A. Weldy
 
Lucky Shooter A said:
I'm not having any issues.

Have been cleaning up with a boring bar----no problems with this.

The method I read about-----as I recall----sounded like a quicker
and easier method and I just wanted to revisit it.

Thanks for all the replies.

A. Weldy
Click to expand...

Ok.

As was noted, if establishing a true center in a piece is a requirement, the one fool proof way is to single point it. It removes all doubt.
 
Found what I wanted----

in a 5/13/11 post by Dave Tooley.

I got my best results after a very wise man gave me a bit information one day at a match. I have never seen a discussion of how to put an accurate center in a barrel. This is the key to consistancy using this chambering method. In the past I always got a close fitting bushing and jammed the center reamer in until I had the depth I wanted. Thought I was good to go. There was one very important step I was ommitting. Here's how I do it. Set the barrel up either in the chuck if it will fit or run it in a steady rest and run it at about 100 rpms. Push the center reamer in by hand to the depth you want, here's the bit information that makes a big difference, with the lathe still running pull the reamer to one side until it stops cutting. You have just removed all the tolerences that stack up between the fit of the bushing to the bore and the bushing to the reamer. You now have a center that is in perfect alginment to the bore.

That wise man who gave me that tip was George Kelbly at a 1k yd. match. Thank You Sir.


Thanks to all for info.

A. Weldy
 
Lucky Shooter A said:
in a 5/13/11 post by Dave Tooley.I got my best results after a very wise man gave me a bit information one day at a match. I have never seen a discussion of how to put an accurate center in a barrel. This is the key to consistancy using this chambering method. In the past I always got a close fitting bushing and jammed the center reamer in until I had the depth I wanted. Thought I was good to go. There was one very important step I was ommitting. Here's how I do it. Set the barrel up either in the chuck if it will fit or run it in a steady rest and run it at about 100 rpms. Push the center reamer in by hand to the depth you want, here's the bit information that makes a big difference, with the lathe still running pull the reamer to one side until it stops cutting. You have just removed all the tolerences that stack up between the fit of the bushing to the bore and the bushing to the reamer. You now have a center that is in perfect alginment to the bore. That wise man who gave me that tip was George Kelbly at a 1k yd. match. Thank You Sir Thanks to all for info.A. Weldy
Click to expand...
.OK, it's 10:30 pm and I should have gone to bed an hour and a half ago so I'll ask the stupid question. Doesn't that give you an oversize chamber?
 
adamsgt said:
.OK, it's 10:30 pm and I should have gone to bed an hour and a half ago so I'll ask the stupid question. Doesn't that give you an oversize chamber?
Click to expand...

This is talking about establishing a true center in the end of a barrel. I see what he is doing.

As with anything in machine shop work, the one thing that counts is the results. If this results in what ever you wish to run true in doing so, then it works.

I am a little vague on just what the purpose of having a true center in a barrel is. They come with one on both ends. Perhaps it has to do with establishing a true steady rest spot for those that chamber in a steady rest.
 
Lucky to remember

I'm lucky to remember much of anything from almost 7 years ago.

This doesn't pertain to the method I use for barrels-----through the headstock, indicating
at the throat and muzzle.

It won't hurt me to know a little more about machining.

Thanks again to all.

A. Weldy
 
Establishing a true center on the barrel is for setting the barrel up between centers and chambering in the steady rest. If you do your work in the headstock then it becomes less of a benefit to establish true centers on each end of the barrel.
 
I work between centers so I find that "tip" interesting; but I have always felt that a precise center isn't critical in setting up the steady isn't critical as my floating reamer holder (pusher style) will allow plenty of float for the reamer pilot to follow the bore. If I held the reamer rigid- as in a collet, then it would be more relevant.

Thoughts?
 
BG Gunworks said:
I work between centers so I find that "tip" interesting; but I have always felt that a precise center isn't critical in setting up the steady isn't critical as my floating reamer holder (pusher style) will allow plenty of float for the reamer pilot to follow the bore. If I held the reamer rigid- as in a collet, then it would be more relevant.

Thoughts?
Click to expand...

I consider a perfect or as close to perfect barrel setup the most important thing. Then the floating reamer holders and pusher can't screw it up. Their primary purpose is to not screw it up. Depending on a reamer to have the ability to wobble around to get a good chamber is counter productive.

I run the finish reamer in by hand even on my Haas. I often stop when I have half the chamber cut and put and indicator on the reamer shank to check alignment.
 
Dave Tooley said:
I consider a perfect or as close to perfect barrel setup the most important thing. Then the floating reamer holders and pusher can't screw it up. Their primary purpose is to not screw it up. Depending on a reamer to have the ability to wobble around to get a good chamber is counter productive.

I run the finish reamer in by hand even on my Haas. I often stop when I have half the chamber cut and put and indicator on the reamer shank to check alignment.
Click to expand...

Dave,

Have you ever had misalignment when you stop halfway of the finished chamber and indicate the reamer shank? If so, how do you make correction to the misalignment now that chamber is halfway finished?

Is the alignment you mentioned the same as runout?

Thank you.

Nez
 
Nez,

If there is going to be runout on the reamer shank I know it before I get that deep. I'm really just getting a data point to make me feel good. Also to hopefully make a point with those that think a floating/pusher reamer holder cures misalignment issues. If by chance something funny is going on I check barrel setup, throat and roughed chamber to see what's off. Re adjust the throat as needed and true up a short portion of the roughed chamber. While not a perfect scenario in regards to concentricity, with the bushing and chamber mouth running true it's then difficult to force a reamer off center when it's supported on each end and a bit of friction. 99.9% of my chambers are roughed in with a caliber specific core drill. The front follows the bore and the rear, which I'm sure isn't perfectly aligned axially, can act like a single point tool. I've measured runout of roughed chambers and they are in tenths. Chambers measure the same. For the odd chambers I rough them with a drill then true with a boring bar to get the pilot in the bore when the body starts cutting. That's really the same process for re aligning the barrel.
Is any of this the perfect process? No there is nothing perfect. After inspecting hundreds of my chambers for concentricity in the throat I know this works for me every time.

Working between centers and using a steady rest is a completely different animal.
 
Something I found interesting

was a tool post keyless chuck Edge Products sells. It can be set up to a dead nuts center on one's tool post, eliminating the need for a tail stock in a lot of cases, it seems to me, this or one of the MT tool post holders one could/can get, to more or less do the same thing. The carriage is a lot easier to use than a tail stock, and way more versatile. Got a MT#3 block coming to try, me. Can use my ER 40 collets as well in it. Thinking about getting a lot closer to good centers here:

I once watched watched a Smith of some renown run a reamer into a chamber he was doing for me straight in, chucked into his tail stock. I must say, I was freaked a bit but the dern rifle shot great, sooooooooo.

Pete
 
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Pete Wass;80937}I once watched watched a Smith of some renown run a reamer into a chamber he was doing for me straight in said:
Pete, running a Reamer in with a solid mount as you described I'll not nessssarilly produce a crooked chamber, but in all likelyhood could produce a chamber that is larger than it should be. The Rifle will shoot fine in all likeklyhood, but the brass will suffer over repeated firings.
Click to expand...
 
As it turned out

jackie schmidt said:
Pete, running a Reamer in with a solid mount as you described I'll not nessssarilly produce a crooked chamber, but in all likelyhood could produce a chamber that is larger than it should be. The Rifle will shoot fine in all likeklyhood, but the brass will suffer over repeated firings.
Click to expand...

that chamber was fine and dandy. Prolly he knew his tailstock was running dead true.

Pete
 
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