Lathe not cutting on center

[robtnort]

I am a beginner and am not familiar with the correct terminology so please bear with me. I just bought a Logan 10" Model 2136. It came with a quick-change tool holder and 3/8" cutters. When cutting to the center of the piece I am turning, there is a 1/8" nub left on the piece. The tool is cutting 1/16" below center. Is there no way to raise the cutter or do I simply replace the 3/8" cutters with 7/16" cutters?

[jdunmyer]

If this "quick-change toolholder" is of the 4-sided European design, you need to put a shim pack under the toolbit. Keep the shims with the bit when removing them.

A better alternative is an Aloris-type of QC toolholder, Phase II has a cheap knockoff that works OK.

[Yankee1]

Or you could put a 1/16" thick piece under the whole tool holder if its the four sided type.

[SGW]

Like the others said -- adjust the tool holder (if possible) or shim.

Changing toolbits won't really help, because the height of the cutting edge will vary slightly depending on how is ground. The tool height needs to be adjustable, somehow.

[robtnort]

Thank you all for your input. I think shimming will solve my problem.

[Paul Alciatore]

Adjusting the height of the tool tip is really fundamental. The old fashoned lantern style toolholders allow adjustment by rocking the tool which sat on a piece with an arc shaped bottom that sat on a ring with a circular depression. The tool could be adjusted in all directions. Problem was, all the adjustments had to be done at once and were locked down by the single screw at the top of the post. To change one parameter, you had to take the chance of all of them changing.

The various QC tool posts allow different settings to be made more or less independent of each other and this is a very distinct advantage. I designed my own QC post that is based on a round post with a generous flat for both clamping and angular alignment. The tool holders have a screw adjustment for tool height. Tools can be removed and replaced with good repeatability. And I didn't have to machine any dovetails like the commercial holders use. And it allows one hand tool changes. I wrote it up and submitted it to Neal so perhaps it will be published soon.

Paul A.