G0766 Tailstock quill and lead screw

  1. Jeff Buyer
    Jeff Buyer
    Does anyone happen to know what the thread is on the tailstock quill and lead screw on the G0766? And is it an Acme thread? No information on the website or in the manual.
  2. Brice Rogers
    Brice Rogers
    I took mine apart once. All I remember is that it did NOT appear to be an acme thread. I recall that it looked like a standard 60 degree thread.

    If your quill and lead screw still work, you can determine the thread pitch by turning the lead screw handle a number of times (for example, 10 turns or 20 turns) and measure the advance of the quill and divide by the number of turns. The thread pitch will most likely be metric.

    Question: did your lead screw and quill fail ?
  3. Jeff Buyer
    Jeff Buyer
    Thanks Brice. No, it hasn't failed. My woodturning teacher is advising someone else on what lathe to buy, and I think he is trying to compare the Grizzly to the Powermatic. He has had to replace the quills and/or lead screws on quite a few older lathes, so Acme threads would be a plus for the Grizzly. Apparently Powermatic is now using Acme threads on the 3520C.
  4. Brice Rogers
    Brice Rogers
    Hello Jeff, I took a closer look at my G0766 tailstock. The thread pitch appears to be 1.5 mm (close to 16 tpi). That's a fairly fine pitch, especially for an acme thread. Although I haven't taken my tailstock apart recently, I still think that it is a Vee thread. (Perhaps others can chime in if I'm wrong).

    I checked the combined price of the Quill and Leadscrew from Griz and it is $ 50. Not very expensive. It probably wouldn't hurt to have a spare on hand. In comparison, the same parts for a 3520C is about $160. Of course, the 3520 costs almost double the G0766.

    BTW, I suspect that in a classroom environment that occasionally someone may apply more force than necessary on the tailstock. That may account for some lathes needing the quill/leadscrew replaced.

    My lathe is 5 years old and gets regular use. I haven't had any quill/leadscrew problems.

    I'm hoping that others with the G0766 will share their own experiences with the leadscrew and quill.
  5. Roger Chandler
    Roger Chandler
    The lead screw in the tailstock of the G0766 has standard threads.......I've not had any issues with mine. My G0800 does have acme threads on the lead screw.
  6. Brice Rogers
    Brice Rogers
    Thanks for posting, Roger. I forget, are the Powermatics and G0800's made in the same Chinese factory ?

    I'm wondering if the feed rate on the tailstock of the G0800 is similar to the G0766 ?? The reason for my question has to do with using a fine-pitch acme thread? When I looked in the Machinery's handbook the finest acme thread that they listed was 16 tpi (close to what I measured on the G0766). Most of the Acme threads that I've seen are much coarser. I'm wondering if there are machining issues with making a fine pitch acme thread??
  7. Roger Chandler
    Roger Chandler
    Brice, I have not actually measured the threads on my G0800 tailstock, but I did have it all apart for cleaning about six weeks ago. It appears to me like they are probably 6 tpi, or maybe 7 or 8 tpi. They are not "V" threads either, but have a flat on the top. Harvey Machine Tool Co. manufactures both the Powermatics and the G0800.
  8. Jeff Buyer
    Jeff Buyer
    My woodturning instructor does say that quill and lead screw replacements are due to students applying excessive force to the tailstock.
    However, I watched some Lyle Jamieson demos recently, and he really cranks down on the tailstock when turning the outside of a bowl between centers. I would guess that with his technique you'd be guaranteed trouble unless you had a heavy-duty lathe with Acme threads. But, at $50 per replacement, its not so bad if you only have to do it every few years.
  9. Brice Rogers
    Brice Rogers
    Roger, even V-threads have a flat, but not as much as Acme threads.

    I occasionally do some "single point" thread cutting using my metal lathe (vee threads). I always look up all of the specs because there are a bunch of nuances. I use the Machinery's Handbook.

    It is interesting that the G0800 has threads that are much more coarse than the G0766. With coarser threads, it is faster to advance the quill. An advantage to most. But, perhaps that is why they used Acme threads - - to compensate for the higher forces needed to tighten a coarser thread.
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