lathe toolholder rotation

Bob S fired this volley in news: snipped-for-privacy@4ax.com:

With an Aloris-style toolpost, re-aligning it is as easy as "kissing" the front face of your chuck with the empty toolpost, and tightening the capture nut. Quick, easy.

LLoyd

I use Arthur R. Warner Co

. They are expensive, but work well.

Pete Keillor

I had to saw off and replace the bent and mushroomed M7 clamping screws.

It's nice, but I didn't claim it's any better than the Aloris / Dorian style, especially if you use carbide bits which already have the correct cutting edge angles.

I can tolerate a lantern or turret toolpost by planning the job carefully and milling custom-height shim blocks, some of which I still use to position small bits under the screws on the Multifix.

I started with a lantern toolpost I made from a bolt, partly by hand, and partly by clamping a tool bit to the top of the compound with a strap and two carriage bolts with heads ground down to fit the slot. jsw

You're welcome Bob. That's part of what this group is supposed to be all about. Eric

Thanks again, yes I had forgotten about rotating the compound requiring rotating the tool holder.

I gather that you seldom use the compound rotation for anything but threads and the rare fast taper, is that correct?

Bob

You can set the compound to 5 or 6 degrees off parallel to the ways and gain a decimal place of control over the cutting depth, that is,

0.001 of compound travel moves the bit 0.0001" toward or away from (boring) the centerline axis. I haven't found this precise enough to try to set the compound to the angle whose sine is 0.1000, 5.739 degrees. 5 degrees cuts slightly less than indicated, which is safer, and it's easy to remember.

With the compound parallel to the ways you can control the feed into a recess in a face, such as an o-ring groove in a pipe flange, or the width of a shoulder if you don't have an indicator displaying carriage travel or a micrometer carriage stop.

The proper groove angle for a vee belt pulley varies with its diameter, since the belt grabs by expanding sideways against the groove walls when it wraps around the pulley.

I made a vee belt drive for a heavily loaded hydraulic pump on my tractor that needed everything done by the book to survive. jsw

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Start using your machine more -- it will remind you of these things. :-)

That is correct. One other possible use of the rotation is when you are using a toolpost grinder on the lathe (in which case the toolpost is off anyway), and you want to get extra-fine diametric infeed. In that case, you want the compound rotated as close as you can get it to either 84.28 degrees or 5.71 degrees -- whichever gets your compound closer to the axis of the workpiece. This trick gives you

0.0001" infeed for each 0.001" on the compound's dial. You're not likely to get much benefit from that trick with normal turning, except with a *very* rigid lathe, and a *very* sharp tool edge, but the forces involved in toolpost grinding are quite low, and the possibility of removing in "tenths" is there, while usually with normal turning tools, the spring in both the lathe and the workpiece means that a very fine infeed will probably just spring things until you build up to a certain level, at which it will cut it all at once -- and likely overshoot your target dimension.

Enjoy, Don.

Agreed. As long as the chuck is not occupied by something too large.

My lathes are a bit too far apart in size to do that, and while the 12x24" Clausing has an Aloris style system (really a Dorian for the toolpost, and a mix of new and used Aloris and some Phase-II holders, the Compact-5/CNC has a toolpost patterned after the Dickson ones, but smaller than any I have seen. That is a little 5" swing machine. So, there is little point to trying to keep the same style of toolpost on both machines, since swapping between them is pretty useless anyway. The Aloris knurling head on the Clausing is bigger than the cross-slide on the Compact-5. :-)

Enjoy, DoN.

I've used a Compact-5 on only aluminum, to learn G code. Is it actually capable of good accuracy on hard metals like drill rod or stainless? jsw

"Jim Wilkins" fired this volley in news:lhe8d1$i3t$1 @dont-email.me:

Which is it, Jim? Hard, or stainless?

Lloyd

All of them are easy for you, right?

"Jim Wilkins" fired this volley in news:lhehcq$tli$1 @dont-email.me:

No, but stainless is what I'd call "tough", not "hard", unless you mistakenly work-harden it.

Lloyd

Compared to aluminum??

"Jim Wilkins" fired this volley in news:lhepvm$7om$1 @dont-email.me:

"Hard" carries certain connotations not associated with aluminum or stainless steel. Aluminum is SOFT, SS not so, but 'hardly hard'.

(unless you make it so)

Lloyd

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"Good accuracy" is asking a lot of a machine whose diameter turning varies in steps of either 0.02mm or 0.002" -- and both are approximations based on what the ballscrew can deliver with the step size of the stepper motors. Try to turn a Morse taper with it, and it will be *visibly* stepped.

Coarse threads are sort of a stairstep wrapped around the shank, too. Limited by the step size, and the number of indicated points for a full rotation of the spindle. I think that it is either 100 or

128 points. And the CPU is an ancient 6502 (the thing which ran old Commodore PETs and Apple-][s among other things. It is seriously strained, and limits the spindle speed to something like 200 RPM or less for coarser threads.)

And even repeatability is a problem. Especially in inch mode, it tends to gain or lose a step every run or so -- either diameter or Z-axis (along the bed). If you are doing a long series of runs, set up indicators to allow you to verify position at the start of each run, and adjust it before you hit the "start" button.

But -- it is the easiest way to cut metric threads that I have. I've got a change gear set for the Clausing, but metric threads on an inch leadscrew are a real pain.

And certain complex things are easier to do on it than on a manual machine.

Now -- I recently saw one which had been modified by another member of the local metalworking club, with finer and faster stepper motors (with microstepping), and a LinuxCNC controller. That would make it a much nicer machine.

Some of these days, I plan to retrofit mine with servo motors and encoders instead of the coarse steppers. A *lot* faster, and smoother -- even if the resolution is only 0.001" on radius (and it can be made a lot better during the conversion) the servo operation would make the Morse taper a proper smooth taper instead of a stepped cone.

Oh yes -- the original has filled plastic wear strips on the underside of the bed, held down by two cap screws, and they tend to wear rather quickly under the heads, and give a lot more play to the carriage. Take some 1/8" aluminum, cut it to the size of the wear strips, counterbore the holes for the screws, and it spreads the force of the screws over a much larger percentage of the wear strips, and causes a lot more operating time between needs to adjust the strips. (Like years instead of months). Enjoy, DoN.

Thanks. They show up second-hand sometimes but it sounds like they aren't that useful as-is, or worth the time and expense to upgrade, if you have larger machines that also need attention. I suspected that the training exercises concealed their limitations. jsw