Need change gear help with a Vevor model YS-1835-A mini lathe!

[6Sally5]

Hi @6Sally5

Forgive me if I am late to the party. I just saw your original posting and so searched for the manual for your lathe. I found it and according to the manual, the gear set you have is the one that is supplied with the lathe!! There is no 65. Bummer. Just (30T,35T,40T,40T,45T,50T,60T,60T).

https://d2v0huudrf11kh.cloudfront.net/vevor-center-goods/金属车床说明书1835A(3)(1)(2)_1687946788233.pdf

Dave

Yessir. That is what I got. As I kind of understand it, with the patient help of several here on this thread, I don’t need the other gears that I thought were missing so long as the first and last gears in the chain are correct. The other gears are idlers (I looked up and read what that is), and I could use any gear as an idler so long as I could get them all to mesh together. At least…that’s what I think? ‍

 

[6Sally5]

I just ran out to the shop and put a thread gauge on the leadscrew. It looks like it is a 16 TPI Imperial leadscrew.

Here also is a closeup of the thread I cut on an aluminum rod next to a steel 1/4-20 bolt.

 

[WobblyHand]

I just ran out to the shop and put a thread gauge on the leadscrew. It looks like it is a 16 TPI Imperial leadscrew.

It seems close. Can't quite tell from the photo how good the fit is over the whole length, it's a little blurry when I blow it up.

If you have a metric pitch gauge, try a 1.5mm. 16 TPI and 1.5mm only differ by a very small amount. If I recall correctly, by ~ 0.0025"/thread. So 10 threads would be a difference of ~0.0225". Wondering if both fit nearly the same. That was kind of my motivation to measure over 32 threads, as the difference would be more obvious. One of the gauges will fit much better than the other.

 

[6Sally5]

Here also is a photo of a rule against the leadscrew. Hope this helps?

 

[6Sally5]

It seems close. Can't quite tell from the photo how good the fit is over the whole length, it's a little blurry when I blow it up.

If you have a metric pitch gauge, try a 1.5mm. 16 TPI and 1.5mm only differ by a very small amount. If I recall correctly, by ~ 0.0025"/thread. So 10 threads would be a difference of ~0.0225". Wondering if both fit nearly the same. That was kind of my motivation to measure over 32 threads, as the difference would be more obvious. One of the gauges will fit much better than the other.

I’ll go see.

 

[6Sally5]

It seems close. Can't quite tell from the photo how good the fit is over the whole length, it's a little blurry when I blow it up.

If you have a metric pitch gauge, try a 1.5mm. 16 TPI and 1.5mm only differ by a very small amount. If I recall correctly, by ~ 0.0025"/thread. So 10 threads would be a difference of ~0.0225". Wondering if both fit nearly the same. That was kind of my motivation to measure over 32 threads, as the difference would be more obvious. One of the gauges will fit much better than the other.

Here’s a pic of a1.5mm gauge against the leadscrew. Close, but no cigar.

 

[6Sally5]

I am still confused. That manual states that the lathe has a metric (1.5mm pitch) leadscrew. If that's true (and I have always assumed that all the Vevor lathes had 1.5mm leadscrews) I don't see how @6Sally5 could have cut an accurate 20 TPI thread using a 40 and 50 change gear combination. 20 TPI is a thread pitch of .050" A 40/50 gear set with a 1.5mm pitch leadscrew will produce a thread with a pitch of 1.2mm or .047"
That's a pretty big error (about 6%?). It would be interesting to see a close-up picture of that lathe-cut thread held up to a regular 1/4-20 bolt or threaded rod.
Or, take a piece of 3/8-16 threaded rod and hold it up to the leadscrew to check that pitch?
On a different Vevor lathe, MatthiasWandel found that the threading chart was full of errors, and apparently Vevor hired him to correct the charts.

Matthias said: "After much investigation, I realized the included threading table was very inaccurate, to the point of being practically useless for imperial threads."

So, perhaps the saga continues?

Good Lord! I retired 6 years ago, so the way I figured it, math, for me, no longer needs to exist. Looks like I’m going to have to throw that math circuit breaker back on in my brain! ‍

 

[WobblyHand]

Here’s a pic of a1.5mm gauge against the leadscrew. Close, but no cigar.

That's rather definite! Looking like it's really 16 TPI. That's good, since it means when you single point imperial threads you will be able to use the thread dial and to disengage the half nuts. Can't do that in general with metric.

 

[WobblyHand]

Here also is a photo of a rule against the leadscrew. Hope this helps?

Hard to tell on that picture. There's some lens stuff that's making it tough to tell on the left side. But the two thread pitch gauges are telling me it's very likely to be 16 TPI not 1.5mm. Maybe this lathe is a Little Machine Shop or Sieg second? They both can come with imperial lead screws. If so, that's good for you, since you will be able to find repair parts for your lathe, if necessary.

 

[VicHobbyGuy]

Something else that is handy to have are thread pitch gauges. They can be purchased quite inexpensively and have saved me many a time. Buy both an imperial and metric set, you'll need them. With a pitch gauge, it's pretty easy to see if you achieved the correct pitch. I always check my scratch pass when threading to ensure it's right. Just something one learns to do. If it's the wrong pitch, you can fix it then. Later, you're stuck with the wrong thread.

Thread pitch gauges are definitely 'must have' tools, and I do check my scratch pass when starting thread cutting to catch big mistakes with the change gears. However, my gauges aren't very long, and definitely wouldn't pick up an error of a few percent - I usually don't suspect that the change gear chart will be full of mistakes.
A known-good long bolt or threaded rod works well for checking a partly or fully-cut threads. Using a pitch gauge or another bolt and holding 'meshed' threads up to the light will reveal (for my eyes) discrepancies that I couldn't measure with calipers.
Long 'barrel' nuts (threaded connectors) can also reveal bad or slightly too tight threads that a normal cut will not. MathiasWandel used that in his video about the Vevor gear chart.