First time post. Neighbor gave me a Sheldon Sebastion gear head lathe. I think it is a B60. Everyone says it's in good shape. Lots of extras. My problem is, we tried to cut some threads and when you set it for ten threads per inch,as per the lever chart, you get eight. Is there a possibility some one has changed gears. How can I find out what I have or need? Originall owner doesn't remember much about it and I haven't been able to find much info on it. I'm not a lathe guru. Just trying to make a few things and learn to operate a new toy.
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Sheldon Sebastion lathe
- Thread starter mf294-4
- Start date
- Joined
- Jan 22, 2011
- Messages
- 8,031
Welcome to the forum. Toss in a picture or two and we'll see who can help you. If you can, show us the geartrain that drives the leadscrew, and the selection chart/panel.
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4GSR
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MF294,
Take and set it for 8-pitch and check for a 1:1 ratio from the spindle to the screw. Does your QC gear box have two levers or is it the newer one that has the three knobs?
I have the A6 version which is a 13" where yours is a B6 which is a 15" swing lathe.
If still not right, let me know and I'll go count the teeth on the spindle stud gear and lead screw on mine and let you know what I find out.
Post a pic of the end gearing on yours and I'll compare against mine to make sure the gearing is correct.
Ken
Take and set it for 8-pitch and check for a 1:1 ratio from the spindle to the screw. Does your QC gear box have two levers or is it the newer one that has the three knobs?
I have the A6 version which is a 13" where yours is a B6 which is a 15" swing lathe.
If still not right, let me know and I'll go count the teeth on the spindle stud gear and lead screw on mine and let you know what I find out.
Post a pic of the end gearing on yours and I'll compare against mine to make sure the gearing is correct.
Ken
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4GSR
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I looked at the picture you posted and yours shows a large gear on the stud and a smaller gear on the screw going into the gear box.
Mine has the same size gear on both the stud and screw, which means it is a 1:1 ratio from the spindle to the gearbox.. I have the same QC gear box as you have.
I suspect someone changed the gearing on your lathe over the years to cut a special thread pitch. if you put the gear levers in the 8-pitch you'll find it cutting a much coarser thread. So , I would count the number of teeth on the stud gear and the gear going into the gear box to establish the ratio. Then from there, determine if it will cut a standard thread and not a odd ball thread pitch and go from there.
Mine has the same size gear on both the stud and screw, which means it is a 1:1 ratio from the spindle to the gearbox.. I have the same QC gear box as you have.
I suspect someone changed the gearing on your lathe over the years to cut a special thread pitch. if you put the gear levers in the 8-pitch you'll find it cutting a much coarser thread. So , I would count the number of teeth on the stud gear and the gear going into the gear box to establish the ratio. Then from there, determine if it will cut a standard thread and not a odd ball thread pitch and go from there.
?Re: Sheldon Sebastion lathe
Checked tonight. Spindle gear is 45 tooth. Next set 45 tooth. Then a idler with 72 teeth. Lead screw gear has 36. Set the levers for a 8 thread and got 6 threads per inch. Do I need a 45 tooth on the lead screw? Looks like a fiber gear. Where can one be found , If that is what I need? Thanks.
Checked tonight. Spindle gear is 45 tooth. Next set 45 tooth. Then a idler with 72 teeth. Lead screw gear has 36. Set the levers for a 8 thread and got 6 threads per inch. Do I need a 45 tooth on the lead screw? Looks like a fiber gear. Where can one be found , If that is what I need? Thanks.
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MF294,
You can either replace that 36 tooth with a 45 tooth or replace the 45 tooth with 36 tooth gear.
Or, put the tumbler in the 10 pitch selector and see if that cuts a 8-pitch thread.
The way the the apron is designed on the Sheldon Sebastin lathe you can engage the feed lever but not at the same time, but in 8 pitch slector it only feeds .060"/rev., if the end gearing is correct. There is a mechanical interlock that prevents both from engaging at the same time. With the gear combination mentioned, 6-pitch makes sense. He is not engaging the feed lever to get 8-pitch!!!
Oh, I forgot to mention the fiber gear, it is no longer available from B & C unless you want to pay $$$$$ for them to make one. The original fiber gear is made of Micarta, there has been several that have made them from Delrin and even aluminum. A replacement does not have to be made of Micarta, casr iron or steel is just fine. I suspect the reasons for the fiber gear is to "quiten" the gear train and make this the "weakest link" of the gear train. The gear is a common gear pitch, 16-pitch, either 14-1/2 or 20 deg pressure angle. They can easily be made if a person has a mill and a dividing head available to cut the gear teeth. I do not know of any "used" ones out there.
You can either replace that 36 tooth with a 45 tooth or replace the 45 tooth with 36 tooth gear.
Or, put the tumbler in the 10 pitch selector and see if that cuts a 8-pitch thread.
The way the the apron is designed on the Sheldon Sebastin lathe you can engage the feed lever but not at the same time, but in 8 pitch slector it only feeds .060"/rev., if the end gearing is correct. There is a mechanical interlock that prevents both from engaging at the same time. With the gear combination mentioned, 6-pitch makes sense. He is not engaging the feed lever to get 8-pitch!!!
Oh, I forgot to mention the fiber gear, it is no longer available from B & C unless you want to pay $$$$$ for them to make one. The original fiber gear is made of Micarta, there has been several that have made them from Delrin and even aluminum. A replacement does not have to be made of Micarta, casr iron or steel is just fine. I suspect the reasons for the fiber gear is to "quiten" the gear train and make this the "weakest link" of the gear train. The gear is a common gear pitch, 16-pitch, either 14-1/2 or 20 deg pressure angle. They can easily be made if a person has a mill and a dividing head available to cut the gear teeth. I do not know of any "used" ones out there.
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Glad site is back up. Talked to the previous owner. He got it from Kraft Foods. He never changed any gears. Found a manual on another site for a 13 inch lathe. It has 36 tooth gears with a 60 tooth intermediate idler where mine is a 72 tooth idler. I do not have a mill. The way I figure it, It wouldn't make any difference if I get a 45 or 36 tooth gear depending on which one I replace. Just so the two are equal tooth gears. Would there be any advantage one over the other? Is there any place that has replacement off the shelf gears? I found Rush Gears but don't know enough to safely order one.
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Rush Gear, Boston Gear, or Martain Gear can provide you with a proper stock gear.
Just need to determine if it is 14-1/2 or 20 deg pressure angle. Most all of the gears Sheldon used were 16 pitch, but they used both pressure angles.
The bore may not be the same as what you need. If not, bore out the stock gear and drag you a keyway using a boring bar with a bit turned sideways in it. Or use a Dumont Broach and broach a keyway.
I can check the gearing on my 13" and let you know what it is when I get back in town if you like.
Just need to determine if it is 14-1/2 or 20 deg pressure angle. Most all of the gears Sheldon used were 16 pitch, but they used both pressure angles.
The bore may not be the same as what you need. If not, bore out the stock gear and drag you a keyway using a boring bar with a bit turned sideways in it. Or use a Dumont Broach and broach a keyway.
I can check the gearing on my 13" and let you know what it is when I get back in town if you like.