Lathe tool holder relief groove?

[jaek]

Lathe turning/facing tool shanks typically have a square cross section with sharp corners. The slot in an Aloris-style tool post holder usually has an internal corner radius. This means that the tool shank doesn't repeatably seat in the shank of the holder. What do people do about this?

Grind a bevel on the tool shank because tools are cheaper and replaceable? Grind a relief groove in the tool holder so that any tool will seat securely? Not worry about it and accept a bit more finicky alignment challenge for stuff like threading and cutoff tools where it actually matters?

 

[extropic]

Lathe turning/facing tool shanks typically have a square cross section with sharp corners. The slot in an Aloris-style tool post holder usually has an internal corner radius. This means that the tool shank doesn't repeatably seat in the shank of the holder. What do people do about this?

Grind a bevel on the tool shank because tools are cheaper and replaceable? Grind a relief groove in the tool holder so that any tool will seat securely? Not worry about it and accept a bit more finicky alignment challenge for stuff like threading and cutoff tools where it actually matters?

It's never crossed my mind before. I just hold the tool against the back of the slot and tighten the set screws. The tool will slide down any fillet until it's seated under the set screws. I certainly wouldn't grind a clearance chamfer on any tool shank or relieve (weaken) the tool holder with a corner relief.
If you're troubled by the alleged "alignment challenge", for more mechanically precise positioning, you could get in the habit of placing a piece of shim stock between the tool shank and the vertical surface of the tool holder slot.

 

[GeneT45]

I had to go take a look... Most of my tool holders have pretty sharp inside corners. I don't have an Aloris to compare to, but my Dorian holders *do* have a shallow relief, top and bottom. Accusize might be doing the same thing, or just squaring things up - there's something there, but it's nearly imperceptible. Most of my generic imports just have pretty sharp corners and the tools appear to sit well against the back.

I've never really given it any thought before, but it's never been a problem. However, for parting, threading, etc, I align the tool to the work rather than the tool holder, so it wouldn't impact me in any case.

GsT

 

[Eddyde]

In that case, I would just grind the shank of the tool.
I have also milled out the slot of several of my tool holders to accommodate thicker shanks. This leaves a sharp inside corner in the bottom of the slots, though I have not had any negative issues from doing so.

 

[Winegrower]

It seems to me you must be changing tools in QC tool holders frequently. The solution is to buy more QC tool holders, so you load a tool in a holder and leave it there.