Problem with Duality Lathe Tool Post Holder Alignment

[anglin]

I set up my Duality lathe a few weeks ago to turn a few parts. I (thought I) was satisfied with the alignment of the tool holder. However, when it was time to drill a hole in the center of the part, I discovered my alignment left a lot to be desired. I can't find any mention of the problem I'm having (perhaps it's too basic of a problem to bother posting about), so I've started this thread to see what other people have done. Here are the steps I went through.

First, I aligned the tool post holder on the spindle nose. I did this three ways, as mentioned in section 2.2.3 of Tormach's "Using the Tormach PCNC Duality Lathe" manual. The first step is to align the tool post holder by eye, using a rule to assist, with the T slots in the table. Next align by setting a dial indicator base on the table and the dial indicator tip on tool holder in the QCTP itself. I used jogging of the table to square the tool post to the table travel in both X (Z in lathe coordinates) and Z (X in lathe coordinates) directions.

While this alignment seems perfectly adequate when turning and facing (and probably for parting), it is totally unacceptable for drilling operations. The controlled point of the drill is a very long way away from the QCTP compared to the turning tools and this distance exaggerates any misalignment.

I've setup my tool table repeatedly, thinking it was just related to the challenges of measuring the centerline of the drill chuck, but I had the same problem. An attempt to drill a pilot hole would put the drill into the material about .050 inch from the centerline, leaving me with a groove in the part.

The misalignment seems to be related to the "align by eye" step of attaching the tool post holder to the spindle nose. So, it is out of alignment in the horizontal plane.

The solution that I came up with was to put the drill chuck tool holder into the QCTP and put a straight bar into the drill chuck and indicate off of it. I've found that most "precision ground rods" are very accurate in diametral tolerance but not quite as accurate, relatively speaking, in the straightness tolerance. The best I found was ±.003 inch tolerance over 12 inches.

So, I used a straight round bar chucked up in the drill chuck, and checked and adjusted the tool post as required. I also rotated the round bar in the drill chuck several times to minimize the effects of the straightness tolerance of the bar. The end result is that the drill chuck centerline is within .018° angle, in the horizontal plane, of the direction of table travel.

Has anyone else had trouble with this alignment? What we're your solutions? I'm going to use the lathe with the alignment as is to see what results it produces. However, I'd be glad to realign.

Thanks.

[Gundawg]

I like using these for most of my edge and center finding on the CNC or manual machines they make tramming in a vise real fast. I do not own a Duality Lathe so this may or may not help you. They even make one with a dot and concentric circles they make finding the center of a drilled hole easy.

I find they are accurate to about .002"

Mike

Welcome to Laser Center/Edge Finder

[anglin]

I spent some time aligning again today. I'm satisfied with the alignment of the lathe spindle centerline, relative to the direction of table motion. I'm satisfied with the alignment of the centerline of the drill chuck mounted in the QCTP, relative to the direction of table motion. I'm pretty confident that the controlled point of the tool is on the axis of the spindle centerline in the X direction (lathe coordinate system, so it's the Z axis in milling).

This leaves the tool "height" which is set according to the thumbscrew on the tool holder. I set this with the height gauge setup that Tormach sells. Of course, due to the complicated geometry of the tool holder (it doesn't rest on a flat surface with a drill chuck in it like all the other tool holders because the size of the drill chuck prevents that from happening) and the fact that the centerline of the drill chuck is really an empty space (unlike all the other tool holders, where you can actually measure the cutting tip), you have to get creative to measure the height of the controlled point. I chucked up a ground rod, measured it and calculated the radius.

I don't want to manually adjust the thumbscrew height, I want to set it according to measurements and have it be right. Looks like that won't be happening, though.

Is there any further input from anyone?

Thanks.