Reamer Pusher

[ELR LVR]

It’s not off center in the sense that it’s not cutting a concentric on center hole. The reamer when pushed with a center is acting like a single point tool. There’s nothing to “center itself back up later” because the hole is not off center, it is round and concentric to the bore.

If for instance- as most tailstocks are, If the tailstock is high some amount
There will be some amount of force directed in that offset direction
it will push the back of the reamer up while pushing it into the bore
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how can it not?

 

[WSnyder]

Redundant. It doesn’t matter if it does “push the back of the reamer up” for the reasons I stated.

because the hole is not off center, it is round and concentric to the bore.

My tailstock as many others are, slightly high and it makes not a whit of difference in the end starting the reamer with the center.

 

[DaveTooley]

It’s not off center in the sense that it’s not cutting a concentric on center hole. The reamer when pushed with a center is acting like a single point tool. There’s nothing to “center itself back up later” because the hole is not off center, it is round and concentric to the bore.

I respectfully disagree. In this setup I have not seen a tailstock quill that didn't move under pressure. A nonconcentric hole means nonconcentric cutting reamer. This is what pushes the freebore area off center. Does it correct itself when you switch to a pusher? Possibly but why chance it. Any wobble in the reamer holders handle indicates a problem. YMMV

 

[WSnyder]

A nonconcentric hole means nonconcentric cutting reamer.

I don’t end up with a non-concentric hole or off center throat when I start my chambers with the center. I adopted it after many of the very same discussions on another forum years ago after Mike Bryant discussed doing it.

All I can tell you with my whole process is my throats and chambers finish concentric and on size. I’ve tried many different ways of doing it and it works for me. Experiment and find your way is all I can say.

Edit: To add I’m not advocating to ignore and not check your tailstock alignment altogether. I’m just reporting that my slightly high (and somewhat normal) tailstock doesn’t cause issues with my method. The other pondering I now have is most tailstocks have some play in the quill so who’s to say mine doesn’t center up a couple of thousandths under load when pushing on the reamer???

 

[ELR LVR]

This is a Trig problem With a 60 degree coned tool (Live/Dead Center) being used to push with
divide that angle by 2 and we have 30 degrees
You will have compound leverage pushing upward in a ratio to the Cosine of 30 deg in relation to how many pounds of force is pushing the reamer inward
just like a 30 degree thread
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In other words , you will have MORE force pushing / deflecting the tool, the tailstock, the quill etc than you will have pushing the reamer because the 60 degree point of the dead center is acting like a wedge to wedge the rear end of the reamer off center until the rear hole of the reamer makes full contact all the way around on the dead center, which is off/ (or High)
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It may clean up in the end once you switch over to a straight pusher because the back of the reamer is cutting away material and enlarging the chamber as it is inserted further.
but then we have to figure out at what point in the reamer will it cut away the amount we initially cut off center

 

[Sniperhandle]

No this one was made in the UK. Gifted to me by Dave Manson.

Very cool!

 

[Carl S]

If the muzzle and throat is dialled in perfect and the start of the chamber is prebored concentric.that section of the barrel- chamber to be.should be running dead true.if you're tailstock is good to the lathes spindle bore axis.what ever method you use with some degree of 'float' in it should not make a great deal of difference to the finished chamber.the reamer will follow that prebored straight hole.and the finished chamber should come out correct..concentric and to spec.

 

[ELR LVR]

If the muzzle and throat is dialled in perfect and the start of the chamber is prebored concentric.that section of the barrel- chamber to be.should be running dead true.if you're tailstock is good to the lathes spindle bore axis.what ever method you use with some degree of 'float' in it should not make a great deal of difference to the finished chamber.the reamer will follow that prebored straight hole.and the finished chamber should come out correct..concentric and to spec.

If I drill a 1/4" pilot hole
then take a 3/8" drill bit and start drilling the next step up with the base of the drill bit skewed 3 degrees off .......................................................................................................................................................................................
You're saying it'll come out just fine ?
Because the initial pilot hole that was dead true

 

[wvlongshot]

I prebore every barrel after dialing in the throat. Most with a core drill. It's held rigid in the Haas and the front flexes to center up in the bore and the back is rigid and acts like a single point tool holding concentricity. If I don't have a core drill I dial in the throat, pre bore with a drill and then bore maybe .500" for concentricity. This procedure has never failed me.
Attached are pics of what I have for my manual machine and the Haas.

View attachment 1668088View attachment 1668089

Dave, is there a style or brand of core drill that stands out? Spiral or straight flutes?
Thanks

 

[WSnyder]

Where how do you get 3˚ off?

A tailstock .002" high over the length of 2.5" equates to an ∠α of 0.0458°. If you drill undersized and bore who cares if the drilled hole is perfect or not? That's the point of boring a hole after rough drilling.

 

[ELR LVR]

Where how do you get 3˚ off?

A tailstock .002" high over the length of 2.5" equates to an ∠α of 0.0458°. If you drill undersized and bore who cares if the drilled hole is perfect or not? That's the point of boring a hole after rough drilling.

A tailstock .002" high.......will try to push the reamer .002" high..........if using a pointed dead center to push into the hole in the rear of the reamer.
regardless of how dead nuts concentric the prebore is
This defeats the purpose of having the prebore perfect
And can Thereby run the risk of cutting an enlarged chamber
The angle error may be 0.0458 deg.
But the chamber can still be .004" larger
it doesn't matter if it's .002" off or 3 Degrees off,
off is still off
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It sounds like some guys are suggesting that just because they cut a nice prebore
the reamer will perfectly follow the prebore regardless of how it is pushed
even if being pushed off center from the rear end
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This is why I am suggesting that 2 flats pushing against one another allows the base of reamer to float and keep itself aligned without being pushed off center
---Any amount, Any degree

 

[WSnyder]

A tailstock .002" high.......will push the reamer .002" high..........if using a pointed center to push into the hole in the rear of the reamer.
doesn't matter if it's .002" off or 3 Degrees off, its still off

All true but as I've stated (and explained why) in the end it doesn't matter if the chamber ends up on size and concentric.

 

[paperpuncher]

A tailstock .002" high.......will push the reamer .002" high..........if using a pointed center to push into the hole in the rear of the reamer.
doesn't matter if it's .002" off or 3 Degrees off, its still off

The reamer acts like a boring bar It doesn’t take the hole out of concentricity it just cuts bigger than the reamer was designed to cut Since most cartridges are tapered bodies, as long as you switch to the pusher before you finish the chamber the reamer will follow the prebored hole and cut on size.

 

[LVLAaron]

Dave, is there a style or brand of core drill that stands out? Spiral or straight flutes?
Thanks

His looks exactly like mine - They're in the JGS catalog. Best money I've spent on reamers. They're such a joy to use.

 

[DaveTooley]

Dave, is there a style or brand of core drill that stands out? Spiral or straight flutes?
Thanks

I use JGS solid pilot core drills. My jobs go from one off's up to 400 on the last big job. For the average guy they might be over kill.

 

[LVLAaron]

For you guys with CNC lathes; Why not run a program to pre-bore an undersized body?

 

[DaveTooley]

That's one option. You would still need to drill a hole for clearance.
It's much easier for me to zero the tool, input the depth in the program and press the green button.

 

[SKWERLZ]

That's one option. You would still need to drill a hole for clearance.
It's much easier for me to zero the tool, input the depth in the program and press the green button.

After playing with the green button stuff a bit I’m really starting to like it.

 

[WSnyder]

For you guys with CNC lathes; Why not run a program to pre-bore an undersized body?

Nate from Straight Shot Gunsmithing (TBAS chucks) does just that on his TL-1. He used to sell a ready made gang tool holder for the TL-1. He also uses a fully adjustable but rigid reamer holder. Phil aka 4Mesh used to do complete CNC chambers. I believe at one point he said he had never used a chamber reamer in the CNC to chamber his barrels. He made his own custom toolholders that used Circle inserts. He was quite successful in his short time in the 1K BR world. Nate from Straight Shot also at one time was working on total CNC's chambers with custom tooling but I think he gave that up. Chad Dixon aka NesikaChad proprietor of Long Rifles Inc I believe roughed chambers CNC. I remember all of the naysayers that told Chad he was destined to fail with the CNC gunsmithing thing

 

[LVLAaron]

Cool. If the stars align, and WW3 doesn't start, I'll be able to retire in a couple of years... at which point I can take the gun plumbing a little more seriously.