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Repair of Change Gears

C E Dunn

Plastic
Joined
May 6, 2002
Location
Cartersville, GA USA
Hi all. I have a Monarch lathe that was built in 1967. It came out of a school shop and so probably did not receive the best of care. The ways are in good shape and all of the feeds and speeds work. The lathe
has been more than accurate enough for the machines that we build for our plant. (I’m looking for a face plate by the way – LO). I have recently come across a problem, however. Maybe some of you could give
me some advice on the best way to correct it.
I was fixing to cut some 7/16-14 threads. After setting up the machine for this thread and getting ready to cut this thread I turned the machine on and engaged the half nut to take a slight cut to make sure that I hadn’t made a mistake and had it set correctly for 14 threads before I took a heavier cut. When I engaged the half nut the
leadscrew stopped. I cut the motor off and double checked the levers to make sure they were engaged properly. Sometimes you have to fiddle with the levers to get all the gears in mesh on this lathe. No luck. You turn the lathe on engage the half nut the screw stops – no torque. I figure there might be a clutch of some kind that needed adjusting or maybe a key or pin that was broken or partly so. I took the cover off to take a look inside the gearbox.

What I found was the following: The change gear for 14 threads has one tooth missing. The teeth on this gear are partly stripped on one side maybe a forth of the width of the face. The biggest problem is that the main gear which is always engaged on every change gear and transmits the torque to each change gear, the one which is moved laterally to engage each change gear, is also stripped on about a third of the face width. Evidently there has been a wreck in the past between these two gears. If these two gears are not lined up exactly
then when torque is applied the screw can be stopped. Eveidently I didn’t have these lined up exactly when I noticed the problem. The problem is that now I know how the main gear is weakened and could go under a heavy load which , of course, is sometimes applied. The gears, as near as I can tell without taking the gears out, are hardened.

What to do? ( 1) I’m told that to get a hardened gear made might be as much as $350-$450. (2) I could sell the lathe but I’m honest and I would point this problem out to a perspective buyer. This would also
cost me money, maybe more than replacing the gear. (3)Make a gear myself but it would have to be a soft gear and might not hold up with the hardened gears it would mesh with. (4) Find a used gear, but where? That might take forever. (5) Find a similar lathe that is worn out for parts. Might take forever. (6)Make a whole new set of soft
gears in the shop, maybe several spares. Can anyone give me some advice on this? I would appreciate it.

Thanks

Charles Dunn
 

Tommy

Cast Iron
Joined
Mar 12, 2002
Location
Brandon, MS
Hey - sounds like we may now have "a friend at the factory." Scott, please tell us a little about yourself.
 

C E Dunn

Plastic
Joined
May 6, 2002
Location
Cartersville, GA USA
Scott, I appreciate ya'lls help at Monarch. I didn't realize parts were still available for a lathe that is this old. Maybe for the benefit of the fellas here you could give all of us a short exsposition of the oldest lathes Monarch can still supply parts for. It would probably be enlightening for every one and would also be good advertising for Monarch.
Thanks again for the help.

Charles Dunn
 

Herb W

Cast Iron
Joined
Mar 14, 2002
Location
Manitoba, Canada
Scott
Great to see you participating here!
I took note of your mention of *used* gears and am wondering; are many used parts available?
 

Tommy

Cast Iron
Joined
Mar 12, 2002
Location
Brandon, MS
Scott.

I would guess your field work involves mostly later model machines, however do you ever get a chance to work on earlier models such as the "works in a drawer" version?
 

carla

Stainless
Joined
Mar 12, 2002
Location
W. Coast, USA
hello, scott,

thank you ever so much for helping out with the monarch lathe situation here......i'd like to ask, if i may, whether you'd ever considered going back to a mg set type of drive for the "ee" machines???.....the reason i ask is that we'd run some of the mg drive machines for years, years ago, and found them to be ever so much better in practise than the tube drive units....better low speed torque and speed control under load, no fussy adjustments as electronic components changed value over time, no reliability or maintenence problems other than occasionally renewing brushes, and giving the motor and mg set bearings a bit of light grease......the only down side to the mg drives is that awful 3600 rpm whine....

wouldn't it just make all the sense in the world to have reliance....or whomever...make up a mg set wound to run at 1200, for a gentle "whirr" or "purr" sound, with the mg set itself mounted in a cabinet external to the lathe????....say, inbuilt into the operator's bench, with a little quite blower, and some acoustic damping???....easy enough to run the power leads either in an armoured cable up a suitable bracketing to cross over to the lathe above the operator's head......or, maybe, to groove the floor for the installation, to run the cabling from bemch to machine, then back-fill with a bit of grouting????.....slightly more first cost in the installation, to be sure, but not really all that much, i'd think...

also, i'd like to ask you about some parts for my pet "ee", if i may.....its #48261....

do you have any cross-feed and compound screws w/nuts in stock????(mine has the standard taper attachment)....if so, what price???.....a set of new spindle bearings???....new half nuts???.....motor brushes???......a good used longitudinal feed handwheel???

this may be no little bit unlikely, but i thought i'd ask.....any chance you might have a set of the motor and spindle pulleys on hand for the 2500 rpm version of this machine???...mine is 4000 now, but i'd rather have the low speed torque without using back gear, cos i often use hs instead of carboloy on little one-off parts....easier to grind form tools in hs....

if there's no chance on a set of the pulleys, could i get a copy of the drawings for them???

any chance of a used trava-dial mount for the right hand end of the carriage???.....one left over from a digital readout re-fit, maybe???

cheers

carla
 
D

D. Thomas

Guest
Carla, your new and improved M/G situation makes sense, but I suspect Monarch's response would be that using an oversize AC 3phase motor and VFD with 2 speed gearbox, is the answer for the modern situation, as VFD's are quite reliable and not finicky. I sure would like to operate one outfitted that way, just to be sure though...uh, Scott, my facitlity is available for long term testing...
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