Heavy 10 Apron sticking

colinag · Aug 13, 2020

Hello; I have a mid 50s? Heavy 10. I've searched but had no luck with this problem. When in power feed at any speed I get a regular pattern on the piece being turned in time with the rotation of the lead screw. It is not one for one but reduced as though it's through the worm and clutch but in a regular pattern . I have rebuilt (replaced bearings) the quick change gearbox and found no problem with it. The lead screw is straight and the tail stock end bearing is good. I have stripped and reassembled the apron and can find no problem yet on re assembly of the lathe can feel a tight spot when turning the quick change input by hand. this is about every 20th or so revolution of the lead screw with power feed engaged but not with out. I am using non detergent 30 oil in the apron I'm at a loss here. Thanks for reading through my 1st world problem. Can you offer any advice? Thanks Colin

texasgeartrain · Aug 13, 2020

Will it happen in both crossfeed and longitudinal ?

SLK001 · Aug 13, 2020

Check your gearing that drives the gearbox. Look for chips embedded in the teeth.

Can you hear it?

Is it in the same place on the bed?

How are you driving your spindle? Is it a continuous belt, or a split belt?

BDRetz · Aug 13, 2020

I will be following this thread closely. I get the same pattern with my 1974 Heavy 10. It is most visible on larger diameter pieces, made a nice pattern on rim of cast iron chuck back plate I just finished. I did not see or hear it with the facing cuts just longitudinal. Kind of a harmonic was set up as the speed slowly varied in the cut.

I have checked the input gears for chips. I have not checked the apron or gearbox though. I have a continuous belt and am similarly using 30 weight oil in the apron.

I am curious to see what others have found.

Ben

texasgeartrain · Aug 13, 2020

There's a pinion gear coming out the back of apron, it drives saddle up and down ways by the rack mounted under bed way. I'd be curious what kind of backlash you have between that pinion and rack. Are there any tight spots, or is the backlash in gear teeth between the two excessive ? Also, is the amount of backlash consistent from under chuck to further along ways ?

With apron in neutral you can grab hand wheel for longitudinal and see how much end play there is at varying points along ways. Also getting down on knees, look at pinion gear to rack and watch how much play bumping hand wheel back and forth.

Not sure on a heavy 10, but on a 16" I can shim rack down to tighten up backlash, if too loose. Or shim in a way to get consistent free play the total length of travel on bed.

Also in line with SLK001's thought, on something is a gear tooth, highly possible you have a tight spot. I'd also watch gear on tumbler arm. Sometimes they are very close to an adjacent gear, of the gear they are engaged to, and in being close to adjacent gear, might actually touch and bind on that adjacent gear.

Brandenberger · Aug 13, 2020

BDRetz said:
I will be following this thread closely. I get the same pattern with my 1974 Heavy 10. It is most visible on larger diameter pieces, made a nice pattern on rim of cast iron chuck back plate I just finished. I did not see or hear it with the facing cuts just longitudinal. Kind of a harmonic was set up as the speed slowly varied in the cut.

I have checked the input gears for chips. I have not checked the apron or gearbox though. I have a continuous belt and am similarly using 30 weight oil in the apron.

I am curious to see what others have found.

Ben

Have either of you tried the same cut in threading mode (set gears for fine pitch, and an *appropriate* speed)? Obviously the mechanism for carriage movement is different and might help you eliminate a potential source of the issue.

Also, can you tell if the impact on the cut is coming from vertical movement of the tool relative to the work, saddle relative to ways, or inconsistent rate of advance of the carriage?

For instance, mount a precision bar in the machine, indicate it to be running true. Now put the indicator on your compound, and indicate the bar, and see what kind of result you get? Do you see the periodicity in the indicator reading when power feeding?

If you rig up a power drill to the carriage handwheel and advance it that way, do you get the same result?

-Phil

colinag · Aug 13, 2020

Thanks for reply's. Have not tried in crossandfeed. With drive gear to gear box disconnected and shaft turned by hand I can feel a tight spot regardless of where saddle is along bed. haven't tried with thread half nuts engaged with finest thread. Drive belt is jointed but does not appear to be in sync with pattern. All gears in apron and gearbox have been wire brushed and are chip free. Will try all suggestions in the next day or 2 and reply. Thanks Colin

garyphansen · Aug 13, 2020

My guess is that you have a single phase motor. Am I correct?

carlherrnstein · Aug 13, 2020

Sounds like a metal chip in a gear, gear catching on the one beside it or a pin through a gear that's not seated all the way. Switch the feed around and see if catching increases of decreases in frequency. It might help identify the gear.

kitno455 · Aug 14, 2020

Drop the right gearbox tumbler out of engagement, and turn the leadscrew by hand. If you feel the drag at that point, its either the output of the gearbox, the leadscrew, or the apron. I'm guessing a chip in the wormwheel in the apron, or something wrong with the clutch.

allan

colinag · Aug 16, 2020

Thanks to all for suggestions. This problem has always pointed to a chip stuck in a tooth yet every time I strip the gear box, apron or the reverse / drive gear set , I find nothing. They say a definition of insanity is doing the same thing over and over again and expecting a different result. I have yet again put the lathe back together. This time I cut a small piece out of the headstock casting where the 3rd screw from the left that holds the gear box to bed is obscured by the headstock. I , then covered this small gap with a removable patch to allow for quicker tear down should it be needed again.
I have removed and cleaned and checked the rack. Nothing found. I have a 1 HP 220v single phase. Three phase would be better, but can't see this as the cause. Everything points to the apron power feed clutch as the problem. With drive gears disconnected and shaft turned by hand a slight drag can be felt every 20th or so revolution of the leadscrew regardless of which feed speed is engaged but only when the clutch is engaged. I do not get the pattern if I use the half nuts and 480 thread to advance the carriage. Maybe, like me, it's just old and damn near worn out! It's frustrating when after stripping to base components, cleaning, filing teeth, checking mesh and clearance no problem can be found. For what it's worth the pattern, which is definitely caused by variation in speed of carriage advance , is less noticeable after this last attempt to cure than it was before, BUT IT'S STILL THERE. Colin

texasgeartrain · Aug 16, 2020

colinag said:
Thanks to all for suggestions. This problem has always pointed to a chip stuck in a tooth yet every time I strip the gear box, apron or the reverse / drive gear set , I find nothing. They say a definition of insanity is doing the same thing over and over again and expecting a different result. I have yet again put the lathe back together. This time I cut a small piece out of the headstock casting where the 3rd screw from the left that holds the gear box to bed is obscured by the headstock. I , then covered this small gap with a removable patch to allow for quicker tear down should it be needed again.
I have removed and cleaned and checked the rack. Nothing found. I have a 1 HP 220v single phase. Three phase would be better, but can't see this as the cause. Everything points to the apron power feed clutch as the problem. With drive gears disconnected and shaft turned by hand a slight drag can be felt every 20th or so revolution of the leadscrew regardless of which feed speed is engaged but only when the clutch is engaged. I do not get the pattern if I use the half nuts and 480 thread to advance the carriage. Maybe, like me, it's just old and damn near worn out! It's frustrating when after stripping to base components, cleaning, filing teeth, checking mesh and clearance no problem can be found. For what it's worth the pattern, which is definitely caused by variation in speed of carriage advance , is less noticeable after this last attempt to cure than it was before, BUT IT'S STILL THERE. Colin

On a 16" I have an adjusting screw at bottom right of qcgb. This helps get lead screw centered through apron. Do you have that on yours, do you feel like lead screw flows through apron nice ?

SLK001 · Aug 16, 2020

Well, all your efforts have eliminated everything except the apron feed mechanism. I would start focusing on the clutch mechanics, or, the 20:1 problem seems to indicate maybe the apron gear. Check THAT gear for a chip.

colinag · Aug 17, 2020

Thanks Texas gunsmith. The gearbox does have the adjuster but have no spec on how to adjust. My guess is you leave the mount screws snug and fiddle about with the adjustment till the leadscrew feels right sliding through the worm gear then fully tighten . Thanks Hot Rolled, every gear has been cleaned up with a file and there aren't any chips. The clutch discs have been stoned and shuffled . Will try loosen and re fit of gearbox adjuster.

SLK001 · Aug 17, 2020

If what you say below is really true, then the problem is NOT in your gearbox.

colinag said:
...With drive gears disconnected and shaft turned by hand a slight drag can be felt every 20th or so revolution of the leadscrew regardless of which feed speed is engaged but only when the clutch is engaged. I do not get the pattern if I use the half nuts and 480 thread to advance the carriage.

It seems to me that you should concentrate your efforts on the apron itself, since it takes approximately 20 turns of the leadscrew to make one turn of the apron gear. I'm not sure, but I think that this is a clue.

colinag · Aug 17, 2020

SLK100 thanks, yes what I say about turning shaft by hand is true. I have thought all along that the problem is/was in the apron. After many attempts to find a problem in there, I moved on to the gearbox and drive gears. That's when I turned to this forum for advice. Here is what I have just found thanks to a tip from texasgunslinger. The adjustment on the bottom of the gearbox makes a HUGE difference to the pattern on the piece being turned. Unless you can loosen the screws holding the box to the bed, moving the adjuster does nothing. On the heavy10 the headstock covers one of the box mount screws so you can't loosen it. I had previously cut a notch in the headstock to allow access to this screw to make it possible to remove the box without taking the headstock off. When slightly loosened a very small adjustment makes a big difference to the position of the leadscrew in or out in relation to the bed, then re-tighten the mount screws. This has made a difference to the amount of drag felt when turning the shaft by hand. I will try by trial and error to get this "drag" to zero which I hope will get rid of the pattern. Colin

colinag · Aug 18, 2020

texasgunsmith said:
On a 16" I have an adjusting screw at bottom right of qcgb. This helps get lead screw centered through apron. Do you have that on yours, do you feel like lead screw flows through apron nice ?

This is/was the problem. Trying to adjust this screw with the mount screws tight does nothing. Loosen the bolts and by trial and error adjust screw until pattern is gone ( on the 2in Dia aluminum test piece I was using. )Thanks to all on this forum for your help. Colin

SLK001 · Aug 18, 2020

colinag said:
This is/was the problem. Loosen the bolts and by trial and error adjust screw until pattern is gone on the 2in Dia aluminum test piece I was using.

Okay, then why wasn't the pattern there when you used the half-nuts to feed the carriage? The rack pinion gear is out of gear when you use the half-nuts, but the leadscrew is still in the same position. If your leadscrew alignment really was the issue, then some of the statements you previously made were simply not accurate.

I'm afraid that you really haven't fixed your problem (as you have stated it), especially from any adjustments at the gear box end. I still contend that your problem is an embedded chip in one of the apron's gears, either the idler or the rack pinion gear. What you may have done, is unmesh the leadscrew and the idler gear enough to now be driving the gear above or to the side of the enbedded chip. Although this may appear to have fixed the problem, you don't want to operate your lathe without proper leadscrew-gear meshing, as the gear will wear irregularly. Look down the leadscrew and note where the idler gear intersects with the leadscrew. It should mesh symmetrically about the vertical axis and not off to one side or the other.

I don't want to be a Debbie Downer to you, I just offer these thoughts for your consideration.

Did the pattern appear when you turned left to right (in reverse)?

colinag · Aug 18, 2020

SLK001 said:
Okay, then why wasn't the pattern there when you used the half-nuts to feed the carriage? The rack pinion gear is out of gear when you use the half-nuts, but the leadscrew is still in the same position. If your leadscrew alignment really was the issue, then some of the statements you previously made were simply not accurate.

I'm afraid that you really haven't fixed your problem (as you have stated it), especially from any adjustments at the gear box end. I still contend that your problem is an embedded chip in one of the apron's gears, either the idler or the rack pinion gear. What you may have done, is unmesh the leadscrew and the idler gear enough to now be driving the gear above or to the side of the enbedded chip. Although this may appear to have fixed the problem, you don't want to operate your lathe without proper leadscrew-gear meshing, as the gear will wear irregularly. Look down the leadscrew and note where the idler gear intersects with the leadscrew. It should mesh symmetrically about the vertical axis and not off to one side or the other.

I don't want to be a Debbie Downer to you, I just offer these thoughts for your consideration.

Did the pattern appear when you turned left to right (in reverse)?

Changing the position of the gearbox does not affect the clearance between the rack and pinion. That is a function of the bottom of the carriage and the top of the apron. As stated previously there are no chips embedded in the rack or any of the gear teeth. Slightly changing the angle of the gearbox has allowed the worm gear and key to slide freely along the leadscrew thereby eliminating any binding. I believe it has more than appeared to solve the problem it actually has. Thanks for your help Colin

texasgeartrain · Aug 18, 2020

Appreciate the updates. I like knowing results one way or another for troubleshooting.

I'm a big believer in getting all the alignments right for clean flowing travel, regardless which pieces. Makes operation real pleasant.

Heavy 10 Apron sticking

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