Lathe tool height setting system

[andrew mcgregor]

I’ve seen lots of various types of lathe tool height setting aids. They all work, but I find them either a little too awkward to use, sometimes a little less than accurate or too complicated. I developed a system to help with adjusting tool heights accurately and easily.

This idea is similar to there concept of using a dead centre in the tail stock but I find that a slightly awkward and inaccurate method.

I started with replacing all of the tool height adjustment nuts on my quick-change tool holders. I find the round knurled nuts supplied with tool holders to be difficult to adjust because you can’t use a spanner to tighten or loosen them. I used 1 inch hex brass bar (which matches several nuts on my lathe) to create hexagonal adjustment nuts with an M10x1 thread.

This allows for easier adjustments using two spanners to lock and unlock the adjuster.

Using the same 1” hex brass bar in the lathe I cut a 60 degree taper (the angle isn’t that important) and faced off the resulting sharp point to create a 1mm diameter blunt tip. This protects the tip from being bent but also gives a visual reference of a known size to adjust tool heights.




With a tool moved up close to the brass taper I use the Magnifier function on my iPhone to zoom in very close. The Magnifier can enlarge by about a factor of 10 and makes it very easy to see clearly and avoid parallax in otherwise awkward positions. With the tip of the brass taper being a known diameter of 1mm it’s very easy under magnification to accurately estimate the amount of adjustment required in comparison to the brass tip. Using the M10 x 1 adjuster screw and hex nut on the tool holders it’s quite easy to move the tool up and down by very small, known amounts.




To assist with registration of the brass taper in the three jaw chuck I numbered the faces of the hex bar to correspond with jaw numbers and marked the amount of ‘stick out’ of the tool in the chuck. If, in the future, I suspect that the registration of the hex rod is no longer accurate it’s a simple matter to lightly re-cut the taper to restore accuracy.



I considered making the taper in a hardenable steel to improve durability but thought better of it. Brass means the taper can be easily recut to restore accuracy where hardened steel can only be ground.

[Toolmaker51]

Your process is correct, and can be reasons to need magnification.
Please don't take following as ridicule, just hard-won experience. I have no proof that absolute center height is critical except on very small OD/ID's, and possibly the occasional long part. Reality says at center or slightly below (the range depends on diameter) is sufficient, but no question above center is to be avoided. Boring sounds like an exception, but physically works best at or just above center. Both are direct functions of tool form and clearance.
That said, I appreciate knowing center, not much time passes facing another lathe to create a new one.
Most centerline gauges rely on tactile or contact with a register surface, few are visual; and dismounting an unfinished part is not popular. This includes us with too few holders for entire job, having to reset from turning to facing, boring, threading, etc. Finally, when running left hand bits, obstructions can obscure seeing the cutting edge...
There are endless posts on CL gauges, most suit the particular user, as shown here https://www.homemadetools.net/forum/...archid=2639102 ..... A part of this extensive topic is simple yet disregarded in half the submissions, (especially youtube) some lathes have finished cross slides, others remain as cast.
You might happen across one of mine too at Another in the endless precession of Lathe Center Line Gauges ......

The most interesting feature, the attraction we share toward machine tools is not just gray iron, sparks, or job satisfaction. It's realization no method is ideal, universal, or fail safe; no matter range of available techniques, there will be more.

PS. None of the commercial tool height 'gauges' are worthwhile. Especially the red anodized versions with a spirit level. Could be fact, all the red tools are more eye candy that shop floor essentials.

[andrew mcgregor]

Many thanks Toolmaker51. That’s my first forum post. I’ve also learned that photos don’t seem to upload in forum posts. Pretty dry reading at the best of times - let alone without photos. I’ll work on resolving that. Cheers

[Jon]

If you're having photo upload problems, you can always attach them to an email and send them to me at jon@homemadetools.net.