Measuring precision length while part is on the lathe

Wow RJ, you just raised the bar for giving explanations to this old brain. I think I get it. Now I'm just a little jealous of your computer drawing and layout skills too. More to learn


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I have set the compound rest to parallel with the bed and used the dial on the compound, when I didn't have my mag base. Just face off and set your zero from there. I can only get about 2" of travel this way however.
 
Ryan383 said:
I have set the compound rest to parallel with the bed and used the dial on the compound, when I didn't have my mag base. Just face off and set your zero from there. I can only get about 2" of travel this way however.
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Won't help John without a DRO but I do the same with a scale on the carriage and one on the compound. The readout sums the two, or will read either. The carriage on my large lathe probably weighs 5 or 600 pounds, tough to nudge it that last thou, so I get it close and use the compound for the final setting. Had a similar setup from DRO Pros on a Colchester that didn't have graduations on the carriage wheel.

Greg
 
Thanks Ryan and Greg, both good thoughts and I will try to put these and other suggestions learned from this thread to use. Hope this old brain remembers theses tips when I need them. Also, I need to get better at the search function. I didn't even know some carriage wheels had graduations. Humm seems I have scale envy!


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The one that I have been using for many years is the "Travadial" it consists of a wheel that rolls against the front vertical surface of the lathe bed; this wheel is crowned and textured so that it does not slip, and by fine tuning the angle that the wheel contacts the way or other surface, it can be fine tuned for accuracy; the display is a dial indicator face with 100 grads of .001 each, and there is also a separate dial that is zero resettable (as is the dial indicator) and marks one inch distances up to 5"subdivided into .100" graduations. They are made by Southwest Industries Incorporated (SWI). They seem to be quite accurate and repeat nicely and of course can be used on any length lathe bed or any other machine that has a surface parallel to the travel to bear against. I also use step gages subdivided in 1/16" steps from 1/8 to 1"; when used against the carriage saddle wing and a micrometer adjustable stop and a 1-2-3 block is used, the combination has a significant range for a lot of jobs.
 
Another tip from me (although I am sure others will have thought of this). If you lathe has a DRO on the the carriage then you also have a DRO on the tailstock. When drilling with the tailstock bring your drill up to touch on your part, now advance your tool holder on the carriage up to the drill chuck until it comes to rest against any flat reference surface on the chuck and zero your dro. Now advance your carriage towards the workpiece until the intended drill depth is displayed on your dro and lock the carriage. The tool holder will now form a stop on the advancing drill chuck at the required depth. Beauty is you can retract the tail stock ram and relocate the tailstock and this stop will still be correct provided you do not movement the drill in the chuck.

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atunguyd said:
Another tip from me (although I am sure others will have thought of this). If you lathe has a DRO on the the carriage then you also have a DRO on the tailstock. When drilling with the tailstock bring your drill up to touch on your part, now advance your tool holder on the carriage up to the drill chuck until it comes to rest against any flat reference surface on the chuck and zero your dro. Now advance your carriage towards the workpiece until the intended drill depth is displayed on your dro and lock the carriage. The tool holder will now form a stop on the advancing drill chuck at the required depth. Beauty is you can retract the tail stock ram and relocate the tailstock and this stop will still be correct provided you do not movement the drill in the chuck.

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Having Aloris tool holders for my 19" Regal lathe, I use the Morse taper holder and do virtually all of my drilling with the carriage, using power feed.
 
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