update: rigid reamer holder

[LVLAaron]

Ultimate Reloader got this idea from Bruce Thom (BAT Machine).

It's a machined-in-place tailstock holder made from an MT-Jacobs adapter. The merits are appealing. Very rigid, very simple, and if machined properly should be dead nuts to the specific machine.


I'm curious if one could machine it well enough to achieve the desired effect. Adjusting a single-point boring bar in a 4-6 jaw chuck seems difficult for the desired accuracy. If the hole is oversized even a few tenths, you'll end up with oversized chambers.


What say you, internet?

 

[xr650rRider]

I don't think I would be using a boring bar in a 4 jaw to bore that hole. If you use a carbide endmill that is dialed in to 0 and slightly undersized of your reamer shank, then final ream the hole again dialed in to 0, then in that exact position where your tailstock is at, it's 0. But will it remain 0 when you move your tailstock. Is your tailstock exact centerline height to your spindle?

 

[Walt Krafft]

Asking for issues to do it that way.

 

[VA_XTC_Shooter]

It's only "dialed" in to that machine at that specific location on the bed. If your bed is perfect and has no wear, then the dialed in aspect may be true from chuck to tail stock, but many are using older lathes with some wear and the bed height is different depending on location along the bed.

 

[Dusty Stevens]

Not a very good plan. Youd have to have your tailstock at the exact spot everytime cinched down with a torque wrench

 

[LVLAaron]

Thanks. Suspicions confirmed.

 

[paperpuncher]

Additionally the amount of extension in the quill could effect the equation as well. If I was going to attempt it I would just use a boring head held in a 3 jaw. I have a couple heads that are a little beat up and use them in such applications

 

[xr650rRider]

Thanks. Suspicions confirmed.

Lot of naysayers but the designer/builder of Bat actions says it's the best way. Nobody else has your lathe in their possession. You've got the tools, make one and measure it. You might be surprised.

You can also add a torque wrench capability to your tailstock. I took tailstock apart and cut the end off of a 1/2" socket and tig welded to end of lockdown shaft. It helps with consistency on locking it down.

 

[LVLAaron]

I'm willing to try anything non-destructive. My first concern is cutting an accurate hole. If it's a thou oversized it's an immediate no go.

 

[xr650rRider]

I'm willing to try anything non-destructive. My first concern is cutting an accurate hole. If it's a thou oversized it's an immediate no go.

Say you have a .4375" reamer shank. If you put a hole making cutting tool that measures .4375" OD in a set-tru chuck/collet and you indicate it to 0, then bore a hole in the MT? adapter. You just created a reamer holding hole that is centered with your spindle.

An MT3 to 4JT Shars adapter is around $20 on Ebay.

 

[Larry Boers]

To start with I think one needs to be honest with yourself. Is you lath in the same class as his? Is your abilities and knowledge in the same class? Listen to the video again and he did state that he worked in the industry as a tool and die maker and what he did to make the lathe straight and true. I would never try that with the lathe I bought but would never question what Bruce did with his lathe.

 

[ShtrRdy]

Short Action Custom did a video which shows their non-floating reamer .

 

[Alex Wheeler]

Hold a boring head in your chuck. Should be able to bore the hole accurate. I'd mount a block on the cross slide and bore the block before I'd use a tail stock though. However the reason this probably works is because there is some play in the quill and reamers can flex more than you think.

 

[Ksracer]

Say you have a .4375" reamer shank. If you put a hole making cutting tool that measures .4375" OD in a set-tru chuck/collet and you indicate it to 0, then bore a hole in the MT? adapter. You just created a reamer holding hole that is centered with your spindle.

An MT3 to 4JT Shars adapter is around $20 on Ebay.

How are you going to advance the tool to bore the hole?

If you advance the the quill or slide the tailstock along the ways, you just bored a hole that's parallel with the travel of either method and any angular misalignment it transferred directly to your hole.

 

[xr650rRider]

How are you going to advance the tool to bore the hole?

If you advance the the quill or slide the tailstock along the ways, you just bored a hole that's parallel with the travel of either method and any angular misalignment it transferred directly to your hole.

What are you using to pre-drill, advancing the reamer? The tailstock quill. That's what you have to check, is everything parallel with no runout. If the tailstock is not true to spindle centerline, then your better off using a floating reamer holder.

The OP has a brand new PM-1440GT, I've got a relatively new PM-1340GT, flame hardened ways and at least mine is very true. I'm assuming his is as well. My tailstock quill is very smooth and no play. If everything is true, why introduce float?

 

[GenePoole]

They stole my patented coolant deflection system!

 

[Ksracer]

What are you using to pre-drill, advancing the reamer? The tailstock quill. That's what you have to check, is everything parallel with no runout. If the tailstock is not true to spindle centerline, then your better off using a floating reamer holder.

The OP has a brand new PM-1440GT, I've got a relatively new PM-1340GT, flame hardened ways and at least mine is very true. I'm assuming his is as well. My tailstock quill is very smooth and no play. If everything is true, why introduce float?

Right, that was my point. If somebody bores a hole in a MT adapter, the hole will only be as concentric with the spindle as the tailstock alignment was to begin with.

 

[B Nettesheim]

I watched the video and liked the idea, it was an easy project the most difficult part was getting the morse taper correct.

 

[WSnyder]

If the hole is oversized even a few tenths, you'll end up with oversized chambers.

You could bore it undersize by .006-.008" and finish ream with an on-size reamer. That'll give you a touch of leeway for error when boring.

That spherical adjustable tool holder in the SAC video is very similar to a production toolholder my buddy has used on his bigger HAAS lathe in the turret. I wonder if SAC got the idea from one of those?

 

[X Count]

Before you do it buy yourself a MT parallel Rod and put it in your tailstock and indicate it's length on 2 axis and then extend the quill and repeat in various locations. I did. . . . .then went down a rabbit hole of line boring my tailstock and making an oversize quill to suit.

Bruce is a very smart and capable guy and just making a rigid reamer holder might not be the full story of how he achieves his results. How much work did he do to the quill, base if tailstock and lathe bed BEFORE he made that holder? Also he only indicates the throat and uses a bushing to support the muzzle in the spindle with no indication. How many here think that that's the best way?