Crazy Threads...

Pierre,

My thread dial has a 16T gear and 8 tpi lead gear. It does 4 to 60 tpi inch threads and 7 to ,4 mm metric.
Sometimes the dial is spinning quickly (coarse threads) and its hectic to catch the mark (8 marks on dial). Its a budget lathe.
I can see how a 32T gear on the dial would slow it by half and make life easier.
 
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Hukshawn said:
No, it spins on it's own when in metric. so it must be geared onto the same shaft inside the gear box as the inch.
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Thanks Shawn,
Yup I see your system better now.
There is only one shaft into the gear box on mine so the gear has to be slid in or out on the shaft depending on the metric or inch set up. There are three knobs on the gear box to set threading options. Any chance that I could see a clearer picture of your threading chart?
 
If your lead screw is 8tpi then your thread dial gear must be 16 tooth if you have 2 numbers or 32 teeth if you have 4 numbers. Measured travel must be one inch per number. IF not that is the problem, end of story. A 14 tooth gear will give you an incorrect engagement. The half nut may engage but the dial will not give guide you to engage at the correct spot on the lead screw. Your video shows a 4 number thread dial. It must work with a 32 tooth gear or your half nut will not engage at the proper point on the lead screw's thread. IF all the facts given in this post are correct, lead screw pitch =8; proper gears in place for SAE threads; half nut assembled properly; no parts off another lathe. Rules of screw threads and gears demand that installing a 32 tooth gear on this lathe will solve the issue.
 
TakeDeadAim said:
If your lead screw is 8tpi then your thread dial gear must be 16 tooth if you have 2 numbers or 32 teeth if you have 4 numbers. Measured travel must be one inch per number. IF not that is the problem, end of story. A 14 tooth gear will give you an incorrect engagement. The half nut may engage but the dial will not give guide you to engage at the correct spot on the lead screw. Your video shows a 4 number thread dial. It must work with a 32 tooth gear or your half nut will not engage at the proper point on the lead screw's thread. IF all the facts given in this post are correct, lead screw pitch =8; proper gears in place for SAE threads; half nut assembled properly; no parts off another lathe. Rules of screw threads and gears demand that installing a 32 tooth gear on this lathe will solve the issue.
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youre right. i completely agree. we had a few ideas about what size gear to use, i was just going to make one out of plastic to try. but there is a bigger problem with the change gears not giving the right tpi.

so, on a side note. i was home tonight for a rare change. so i took some time on the lathe. now that i know metric will work, i threaded my project with a 1mm thread, worked perfect. but, as a result of trying to thread this thing before i posted, the walls of my project ended up too thin... so thats a scrapped piece of 2" bar stock...
on an unrelated note, lets all hear it for the parting tool!!! yayyy... its my favorite.
 
Even more unrelated... here's a brass hammer I just made... cause apparently it's impossible to find (let alone affordable) a brass hammer near Bowmanville, Ontario, Canada...

IMAG0687.jpg
 
I think if you resolve the thread dial gear issue you may resolve your TPI issue. Im not positive but I do know that must be resolved in order for you to cut SAE threads on your lathe. So I would resolve what we do know is wrong and then see what happens with the TPI issue. Have you seen if this company is still in business or if a manual can be had? Im just thinking they, if still around or a manual may clarify gearing issues that may effect TPI.

Your hammer looks good, nice thing about brass hammers, they may be hard to find but not too hard to make.
 
There's a lot of pages in this thread that have explained all these issues.

The tpi issues have been discovered without using the thread dial. leaving the half nut engages and reversing the lathe back to the start.

And thanks for the comment about the hammer. Most fun I've had on the lathe I'm the past week. it took me longer to whittle down the handled (that's far too long, really...) to fit the hole than it did to make the piece.

Actually, that's not true. it took me longer to do the math to find out what length of 1" brass I needed to make an 8oz hammer.
 
Yes, good looking hammer, how much do want for it? :)

Re the thread pitch problem, so far we know that your lathe can produce some thread pitches properly but not all of them. Imperial thread pitches of 8,12,16 and 24 all came out coarser than they should. These were run without opening the half nuts.


For the settings that are coming out coarser, it means that the lead screw is turning faster than it should and that can only mean gearing is off.


Which gearing and why?


It would be important to determine if all the inch pitches are off or only some of them. The testing done so far has only involved the AZ and BZ options in the inch mode. Likewise, only the BX and CX options have been tested in the metric mode. Shawn, please confirm this.


If all the inch pitches are off and all the metric are on, then that means something. If only part of the inch and part of the metric pitches are off then that means something else. Do you feel like doing more testing? :)


Shawn, just curious but how does the shifting feel when changing gears? Is it positive? Does a shift lever feel the same when moved in both directions? Does the shifting always feel the same from day to day?
 
Some gears are definitely harder to get into than others. I turned a 1mm thread last night and it took me about 3 minutes to figure out how to get the gear box into C. it wouldn't mesh. even when turning the spindle. then randomly without me noticing (not magically... I had my hand on the lever and was paying attention to something else) and it clicked in.
I'm wondering if this warranting taking the gear box and giving a good cleaning. it's been oiled, lots... it has pan with wicks accessible via a 3/8" looking screw in the top of the gear box.
when I was cleaning the lathe after I got it, I debated taking the gear box off but instead sprayed a bunch of break cleaner up from underneath and let all the old grease fall to the floor, then blew it out, let dry, then filled with new oil... lots.

Last nights night off was a bit of a rarity. when I have a bit more time, I'll clean up that bar stock I was using and run through as many threads as I can to look for consistencies/inconsistencies.

Edit - maybe instead of running through all of the pitches, I'll just make sure I hit every major gear clusters?
Should I assume it's more unlikely that the quick change gears are incorrect than the lever gears?
 
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