Crazy Threads...

I FOUND IT! FOR **** SAKES I FOUND IT.....

the metric gear on the back of the 74 that's SUPPOSED to be a 34, is in fact, actually 32t.... CHRIST....

So here's an amazing new problem... the one gear set up that actually works, is the one that's wrong....


Aaaand back to square one...

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I apologize... apparently you're not allowed to swear on here.. lol

i also apologize over the fact that you guys asked me on numerous occasions to make sure i counted the gearing correctly... i did not... i counted all the gears i could reach without taking something apart... i ASSumed... 7 pages of messages later... it WAS actually what you guys suspected all along...

Okay, so, I potentially have the wrong lead screw, and a wrong gear?

Yous guys's that are super at math, now that ive finally found the problem, what do I need to fix it? I will have new parts bought or custom made if I have to... there are two other 34T gears in the train that i could supply to a shop as a template, as well as the lead screw to be turned to something metric...

another item... im still assuming that with the correct gear and the correct lead screw, this lathe is, in fact, capable of cutting both a metric and an inch thread?... right?
 
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Hukshawn said:
Ok tozguy, I need you to tell me what you want to see... I cannot see anything wrong in here and I have no idea what I'm looking for
Click to expand...

To my way of thinking, the test results indicate that all the gears involved in cutting metric threads are OK. That indicates to me that the problem is not in the gear box with one reservation with respect to how the gear box is geared to handle two input shafts?

But while you can see into the gear box , try all the gear shifts to see that gears line up well, that nothing is broken or bent, no crud obstructing any movement. Also, do you see any thing that would indicate modification such as gears a different color or finish, buggered screws, etc. ?

Brino's No. 184 post is a good idea if you are up to it.

If all the inch pitches are off, then can we conclude that the problem is somewhere in the gears used only for all inch thread pitches?

It is quite common to change gears in the primary drive to get different ranges of thread pitches. My lathe came with 5 change gears. On your lathe, the 51T gear would be the likely candidate to change. For example, to change a 15 pitch thread to 16 it would take a 54T gear. But we would need to know more precisely how much of a change is required before committing to a new gear.

The fact that the 34T in the diagram is actually a 32T means that the diagram is not reliable and is an invitation to question the requirement of a 51T for inch threads.

BTW congratulations on the progress you are making. I am impressed with the quality of that lathe and believe that it is worth the effort to get it sorted.
 
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I did not noticed anything amiss in the gear box. I did a good clean out. but there was not much in the way of "crud". just old grease. all gears move and mesh nice. there us a tiny bit of gear noise between one lever change gear and the numbered gear cluster. I spent nearly an hour trying to figure out why there's noise and one tooth of mild stiffness. I gave up and assumed it was just a bit of wear or that's just the nature of this beast.

However, I still don't know how to fix this.
Do you still believe the lead screw is wrong? which could indicate the inch gear train might be correct?
And coupled with the 32t gear? how confident are you a 54t gear would correct this? that would be cheaper to have made than a 34t and a lead screw...
 
if that leadscrew was actually changed, then any tables marked on that lathe are useless! You will have to measure every gear , plus use a dial indicator to see how much movement results in the saddle and record whassup. ( yeah, it's a pain.) Then make your own truth table .
 
Hukshawn said:
gear noise between one lever change gear and the numbered gear cluster. I spent nearly an hour trying to figure out why there's noise and one tooth of mild stiffness. I gave up and assumed it was just a bit of wear or that's just the nature of this beast.

However, I still don't know how to fix this.
Do you still believe the lead screw is wrong? which could indicate the inch gear train might be correct?
And coupled with the 32t gear? how confident are you a 54t gear would correct this? that would be cheaper to have made than a 34t and a lead screw...
Click to expand...
 
To my mind the lead screw and any gear involved in metric pitches are OK until further notice. Therefor the lead screw, 32T and 62T gears are not suspect.

The inch thread pitch 'problem', with what we now know, can be isolated to the inch only gears i.e. the 74 to 51 combination. We know that the 51T gear can be adjusted away from the 74T gear to accommodate a larger gear.

The hypothesis that a 54T would give exactly 16 tpi when everything is set according to the charts can be verified.
If true, the 51T gear that is on there now would give 15,11 tpi. So to confirm this we need to measure the pitch coming from the 16TPI settings more accurately. The way that I would do this is to turn the chuck say exactly 64 turns and then measure how far the carriage has moved. Put start and finish marks on the ways with a Sharpie.
If the carriage moves 4,24 inches then you have 15,11 TPI and confirmation.

You do not need to put anything in the chuck except maybe a crank handle for turning the chuck.:)
 
Tozguy, I just realized you're in Quebec. that makes your use of commas instead of decimals much more sense. man, you we're throwing me there for a moment.

I have to go home for a moment. I will run that test quickly. (Or as quickly as 64 turns will go...)

Edit - Uhhg after I put the gear box back on
 
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