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Floating Reamer holder verse rigid.

A 7/16 drill blank installed in the floating holder would let you indicate the holder. IMO angular runout is a killer. If the reamer is at an angle to the axis, it can only be concentric in one place.
 
@LVLAaron Is it just like the distance between the barrel and the reamer is axial? I don't get it. I really need to read more stuff. I found a helpful video but unfortunately it sounds like it was in Gujarati and closed captioning wasn't available. I'm just going to get my buddy to show me I think.

@xr650rRider my 5Rs don't chatter with the JGS one.
 
Axial can be when your tailstock is pointed up or down relative to your spindle. You can have it perfectly aligned parallel to the ways and in alignment with spindle in the X-direction. You can have Y-direction perfectly aligned until you change Z. When you extend/retract the tailstock, it could shift lower or higher than the spindle centerline.
 
xr650rRider said:
Axial can be when your tailstock is pointed up or down relative to your spindle. You can have it perfectly aligned parallel to the ways and in alignment with spindle in the X-direction. You can have Y-direction perfectly aligned until you change Z. When you extend/retract the tailstock, it could shift lower or higher than the spindle centerline.
Click to expand...
That makes a bunch of sense now, I appreciate it!
 
xr650rRider said:
He's got a DVD for that.
https://www.gretanrifles.com/product-page/tailstock-alignment-for-reaming-dvd

The holder is nothing more than a dead-center with an aluminum ring to hold the reamer that can be centered up with the chamber, so you don't have to hold it when pushing into chamber. The essence is to perfectly align your machine. Your 5R chatter will disappear.
Click to expand...

So, pretend your tailstock sags a little bit. You install this holder. How does it raise the axis back to center? It looks like it might get the reamer pointed towards the center, but the reamer would just be at the opposite angle of your tailstock sag.
 
LVLAaron said:
So, pretend your tailstock sags a little bit. You install this holder. How does it raise the axis back to center? It looks like it might get the reamer pointed towards the center, but the reamer would just be at the opposite angle of your tailstock sag.
Click to expand...

It doesn't. It's a dead-center. Your tailstock has to be aligned.

Helpful hint: If you don't know how, or your tailstock simply can't be realigned, then one of the manufactured floating reamer holders on the market is what you will need to purchase to correct axis misalignment and give you the ability to ream straight chambers. But, on a floating reamer holder, nothing guides the back of the reamer, it goes where it wants. If the reamer starts crooked, it stays crooked, no matter how the barrel is lined up. It's up to you, my system where you know you're straight, or the others where you hope you're straight.

From a thread a couple of years back.
https://forum.accurateshooter.com/t...e-gretan-reamer-holder-in-these-pics.4007860/

That thread gets into tailstock alignment by cutting a 2 collar test on a bar. Which you would do if your turning a long bar and don't want a taper. From the DVD description

This video shows how to dial in the tailstock along with the why the turning of a shaft for alignment is fighting and ruining all your efforts for flawless precision in the chamber reaming operation.
 
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New machines typically have a tailstock that's a couple thou high, to allow for some wear-in.
Even with that, tailstock bases typically don't wear evenly and you get the axial misalignment-just like the front way/front of saddle wear more than the rear due to tool pressure, the front of the tailstock base wears faster than the rear (forward pressure/chips ) resulting in a downward tilt at the front. Then there's the quill...any movement when locked vs unlocked when extended? Wear without correction leaves you with a tailstock angled downwards, and a quill that droops until it's tightened.

When I obtained my Sheldon the bore of the quill was scored pretty well- so I decided given that and the wear (which was much lighter than most lathes of its vintage) to chuck up/dial in an MT reamer and re-bore the tailstock (after getting front/back alignment correct with the base set screws) to both clean it up, and get the axial alignment as close to "right" as I could get it- losing about 3/8" off the front of the quill in the process. Machining a new quill (with extended travel) is on the to do list, someday...but all of the above is why a rigid setup ain't for me.
 
With the variations in tailstock alignment from use clamping force, etc. there is always a chance for introducing misalignment.
How then is a simple pusher (flat smooth piece in tailstock) against the back of the reamer holder an issue? The smooth flat on flat allows the reamer holder to "slide" in any direction needed to keep the reamer center.
 
xr650rRider said:
It doesn't. It's a dead-center. Your tailstock has to be aligned.

Helpful hint: If you don't know how, or your tailstock simply can't be realigned, then one of the manufactured floating reamer holders on the market is what you will need to purchase to correct axis misalignment and give you the ability to ream straight chambers. But, on a floating reamer holder, nothing guides the back of the reamer, it goes where it wants. If the reamer starts crooked, it stays crooked, no matter how the barrel is lined up. It's up to you, my system where you know you're straight, or the others where you hope you're straight.

From a thread a couple of years back.
https://forum.accurateshooter.com/t...e-gretan-reamer-holder-in-these-pics.4007860/
Click to expand...

It claims it corrects radial misalignment. How does it do that?

(I misspoke in my earlier example about the tailstock sagging... that would be axial sag..) Either way I don't see how having an adjustment point at the base of the reamer can create anything straighter than you started with.
 
It holds up the reamer for insertion. It's not correcting for radial at back of reamer, you have to be aligned, it corrects the front of the reamer for insertion. Almost like a couple fingers on a dong.
 
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If you were to replace the 60 degree cone seat in the GTR holder with a ball nose on the fixed portion seating on a hole in the part holding the reamer would that be an improvement?
 
skeeljc said:
If you were to replace the 60 degree cone seat in the GTR holder with a ball nose on the fixed portion seating on a hole in the part holding the reamer would that be an improvement?
Click to expand...
You would have duplicated a bald eagle pusher but spent 2X as much.
 
skeeljc said:
If you were to replace the 60 degree cone seat in the GTR holder with a ball nose on the fixed portion seating on a hole in the part holding the reamer would that be an improvement?
Click to expand...
I’d think you get exactly the same thing. It’s still centered but can pivot so the nose of the reamer enters the bore aligned.
 
The part with the springs is just a disc of aluminum with a .4375" hole bored thru it. The 60 degree seat is the reamer center.
 
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