Crazy Threads...

Shawn, I bet it can, we just have to find out how.
That would be next question to answer which all the fellas here can help you with.

From the video it looks like you are getting the hang of using the half nuts. The 'slop' in the lead screw, half nuts and gearing in the apron might make it just a question of practise so you can get a feel for it and pick up the right point on the lead screw every time.

However, considering that your thread dial has 16 segments it does not make sense that it have a 14 tooth gear. That renders it useless for anything. The teeth have to correspond to the marks on the dial, which means a 16 tooth gear is required.
 
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Hukshawn said:
So I did the test. Set the gears to metric, set the gear box to 1.5..... guess what it cut...?
A 1.5....
16 didn't fit

Edit - I just hand cranked the lathe in front gears.
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Hukshawn said:
So I'm freezing in my underwear in the garage...

I set up to cut a 1.5, a 2.0, a 2.5, and a 3.0. All match perfectly in the thread gauge.
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Boy, was I wrong! So much for theories, but I can't believe the math worked out like it did. I'm going back to something I know. Checkers, anyone?
Hukshawn said:
AND... why can't it cut imperial as it seems to be designed to?
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Cause it's in Canada? ;)

Tom

Edit: Just for grins, try cutting a metric thread using the thread dial. We know it doesn't work for Imperial threading, but my lead screw theory just crashed and burned. So, maybe....
 
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Tozguy said:
Shawn, I bet it can, we just have to find out how.
That would be next question to answer which all the fellas here can help you with.

From the video it looks like you are getting the hang of using the half nuts. The 'slop' in the lead screw, half nuts and gearing in the apron might make it just a question of practise so you can get a feel for it and pick up the right point on the lead screw every time.

However, considering that your thread dial has 16 segments it does not make sense that it have a 14 tooth gear. That renders it useless for anything. The teeth have to correspond to the marks on the dial, which means a 16 tooth gear is required.
Click to expand...

I will make a new gear foe the thread dial even if it's just out of delryn to test, maybe if someone has some math to help me figure out dimensions?
 
If u are patient enough and somewhat computer familiar, I can download a file that will install, on a windows computer, a program that lets u set up lathe gears in any possible combination and results tpi or metric. Or start with thread spec and tells u what gears u have that will work. I got it a couple of years ago ..... once the variable entries are set up for your lathe, you will know exactly what thread(s) can be cut. It made my Chinese lathe behave !! Tried to download it in this post, but the forum's safety won't allow .exe files thru.
I "think" I have another program for dimensioning gears ...somewhere...
 
higgite said:
Yes, set it up to cut a 1.5 mm pitch thread. That is, set the adjustable lever on the end gears for metric and set the gear box for 1.5 mm. I'm thinking that will make a 16 TPI thread with the 8 TPI leadscrew that's on the machine.

Tom
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Yes, exactly. I suspect that the machine originally had a metric leadscrew and has transposing gears. With the original screw setting it up for metric gave you metric threads and the dial worked (to the limited extent that threading dials ever work for metric). Setting it up for imperial threads gave you imperial threads. A previous owner replaced the metric leadscrew with an 8TPI one. This reversed the effect of the transposing gears so that to cut metric threads he had to set it up for imperial, and vice-versa. The threading dial became useless.

I suggested setting it up for 8TPI because then everything becomes very simple.

The half a revolution slop in the leadscrew could be due to the previous owner bungling installation of the new leadscrew.
 
juiceclone said:
If u are patient enough and somewhat computer familiar, I can download a file that will install, on a windows computer, a program that lets u set up lathe gears in any possible combination and results tpi or metric. Or start with thread spec and tells u what gears u have that will work. I got it a couple of years ago ..... once the variable entries are set up for your lathe, you will know exactly what thread(s) can be cut. It made my Chinese lathe behave !! Tried to download it in this post, but the forum's safety won't allow .exe files thru.
I "think" I have another program for dimensioning gears ...somewhere...
Click to expand...
Ha, both my wife and I have macs, the only pc we have has a gnarly virus right now.
 
so i tried a few tests over lunch.
trying to cut an imperial thread in metric gear set up was a no go. i tried to cut 8tpi with metric setup and it cut something super thin, like a 30tpi or something, i couldnt measure it cause im using a carbide tip rather than a tool steel with a nice point.

put it back into imperial gears and cut an 8tpi, a 12, and a 24. each one came out from what id describe as about 1/2 tpi less than the number i set to. BUT, it did not line up with metric either...

i will try the thread dial in metric after i eat and go visit the wife and kid so she doesnt get mad at me for only coming home for lunch to play with my machinery and eat...
 
also, i did recount all the gears in the train and compared them to the diagram, as far as the diagram is concerned, they are correct...
 
So 8 tpi settings give 7 1/2,
12 tpi settings give 11 1/2,
and 24 tpi settings give 23 1/2.

offset is not a constant proportion....where's the Tylenol?
 
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