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  • #31
    Atlas back gear mystery?

    I apologize. I was not clear. The "bull" gear on my head stock arbor is approximately 5.970 inches. the one that I inquired about was 5.875 inches in diameter. I was able to use my vernier caliper to measure it in the lathe. I know it doesn't seem like much but the smaller gear would seem to cure both problems. (back gear mesh & index pin alignment) That is why I am so interested in other Atlas head stock "bull gear" dimensions. Could the 12" atlas use a different gear?
    I do appreciate everyone's input very much. I have already learned a lot from the forum and hope to learn more. Fuzzy

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    • #32
      I'll go out on a limb here and say these Atlas gears have a diametral pitch of 12. That works very well with the diameters and tooth counts you posted back at #22.

      Except for the bull gear. It shows a DP of about 11.7. If I work the numbers the other way and use a DP of 12, the diameter of the gear would be 5.83", very much like the e-bay guy's.

      Anyway, I have a hard time accepting the idea that Atlas would make a bull gear with the right part number and a different DP. Or make a non-standard gear for no obvious reason.

      I'll get back into the basement tonight.

      Atlas lathe forum (low activity)
      And ask on the Atlas yahoo group. It's pretty active.
      Last edited by Tony Ennis; 02-08-2012, 07:37 AM.

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      • #33
        FWIF, the bull gears on my 1947 QC54, SN 2533, and my late 12" both have 69 teeth. The parts lists for both lathes show part number 10-241. I was not able to measure the diameters.
        Don Young

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        • #34
          I just rechecked the gears on my QC54. The spindle gears are 69 and 30 teeth. The back gears are 63 and 24. This gives a tooth sum of 93 for both pairs. I know it is real easy to miscount gears by one tooth so I generally mark one tooth and then count the spaces from one side around to the other side of that same tooth.

          Since the eccentrics on the back gear shaft are separate pieces, it seems possible that they are not in alignment with each other. In the parts list it looks like they are supposed to be pinned to the shaft but it is not real clear how they are supposed to be aligned. The parts list does show 0.002" and 0.003" shims to adjust the back gear mounting brackets.

          I believe Atlas made some lathes besides the common 10" and 12" versions. If the index pin does not align with the bull gear holes when the gear is concentric with the headstock bore and the pin is concentric with its hole, then the gear and headstock have to be mismatched, in my opinion.
          Don Young

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          • #35
            Atlas back gear mystery?

            The back gear cams are pinned to the eccentric shaft and everything seems fine. I measured a friends Atlas 10" "bull" gear and it measured 5.875 which is about .100 smaller than mine. Both gears have 10-241 cast in them. His lathe is an older change gear type. I think that I will go ahead and dismantle my head stock to better measure everything. I will let everyone know what I discover. Wish me luck! Fuzzy

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            • #36
              The size of the bull gear.

              I also have a 12 inch Craftsman lathe. It appears to have the same problem that you are experiancing. The bull gear on it seems to be swelled to a larger size. The back gears seem hard to engage and the indexing pin also does not line up with the index holes. Also about half of my teeth are missing on the bull gear and it seems to be crystalized. I do have another bull gear coming that I purchased on ebay and will measure it along with the one that is on my lathe in a few days.

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              • #37
                Mark Ball frequents the Shop Floor Talk forum.I don't know if he comes over to this one.
                He has the same lathe and loves to help people.

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                • #38
                  Atlas back gear mystery?

                  I have a replacement "Bull" gear on the way for my Atlas 10" lathe. I see that the Atlas horizontal uses a similar arbor to the Atlas lathe. I wonder if the gear that came with the lathe could be off of an Atlas mill? Fuzzy

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                  • #39
                    Did the new gear lineup

                    When you replaced the gear did the index holes line up and did the back gears engage correctly?

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                    • #40
                      Atlas back gear mystery?

                      I got the new(to me) bull gear (and had it in in one hour!). The index holes line up perfectly and the back gear works as it should. Now I am going to enjoy the lathe and the taper and milling attachments that came with it!.
                      If anyone has any thoughts as to what the larger "bull" gear fits please message me. Thanks to all who commented.

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                      • #41
                        Atlas back gear mystery?

                        RGS let me know how your "bull" gear fits and it's diameter. I want to know if it is the same as the 10" or different

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                        • #42
                          ...and the part numbers, too.

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                          • #43
                            And pictures.
                            Andy

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                            • #44
                              My gear new to me gear fits and indexs

                              I installed the new to me gear and it fits well and the index holes line up. The back gears feel better when they are engaged. The new gear is about 5.87".

                              Do not have a camera now to take pictures but my old bull gear seems to have crystallized. This seems to have enlarged it and also caused it be become brittle. From your discription I beleave that it was slightly larger than yours but it was hard to get a good measurement as over half the gears where broken off on mine.

                              I inherited my lathe from my grandfather who purchased it new in the 50s. He seems to have kept all the other broken gears and I did not have another bull gear so I believe that it was the original one. Its part # is 10-241. The 12 and 10 inch lathes used a lot of the same parts. I believe that all the gears are the same in both.

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                              • #45
                                Atlas back gear mystery?

                                I put my old "back" gear on e-bay and had one bid which is fine. The bidder says it fits his "antique" (his words) Atlas lathe. I am pleased that it will go to someone who can use it.

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