Belt Drive 12X36 Enco, Etc

[SlkipperG]

I picked up a dirty but low usage Enco 1236 belt drive lathe last summer and have just finished going through it and making it about as good as one of these little critters gets. It all started with irritation at the patterned spiral chatter finish produced during cuts. At first I chalked this up to cyclical feeding from poorly cut gears but this really was not the issue. I was noticing that my tenth reading dial indicator would "flutter" about .001" with the motor running and nothing rotating. I rebuilt the motor (new bearings) and changed out the belts and the problem still persisted. What was happening is that the motor, because of the way it is mounted behind the lathe, sets up a harmonic vibration that is imparted to the turned finish when the lathe runs. What I did to nearly eliminate this was pretty crude--I made a wooden wedge and tapped it between the motor & the back casting of the lathe base. To completely eliminate the issue I may install a 3 phase motor or DC motor and use rubber isolation mounts, but it works so well now I most likely will leave it. The motor mounts for these lathes are a hinged steel plate adjusted by a length of allthread. Apparently the mechanical resonance of this mess is such that the whole lathe buzzes during operation. With the wedge this resonance is at a different frequency and the lathe is smooth. There is a HUGE difference. Some other items to look out for: chips embedded in the drive gears. One chip between 2 gear teeth will create a cyclical feed pattern.
I will post some pictures of what I did to this lathe if anyone is interested. It isn't a Hardinge, but it works pretty well now. I have the head adjusted so that it cuts straight and the new Polish chuck I put on it has very little runout. I also adapted one of the hex 5C collet holders I use on my Bridgeport for use on the lathe. It works well and I will make a post on my Quick & dirty collet chuck conversion if anyone has interest.
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[Ray C]

That's a lot of good investigation work you did. Been there, done that and it can be frustrating at times. When I got into that situation, I nearly scrapped the thing a couple times figuring it wasn't worth it. Turns-out I should have followed through as the ways were worn... Got sucked-in even further and fixed the ways as best I could. It finally ended-up cutting OK and I used it for a year after that. Getting a new machine was like a home-coming!


Sure, post some pics...


Ray

 

[Chrispy]

I would be interested in pics of what you did as well. I have a similar lathe and get harmonics when I'm turning at certain speeds. It really makes a noise when I'm parting off. My son calls it my whomp, whomp machine because of the sound it makes :thinking:
Thanks,
Chrispy

 

[SlkipperG]

The rubber mount idea is a good one and is the proper way of solving the problem. It will be my next step. My crude wedge was only a band-aid, but validated my harmonic vibration analysis. This is a whole area of engineering expertise in industrial machinery. It is also another reason why some of the classic machines like Monarch lathes work so well. There is no substitute for cubic cast iron when it comes to vibration damping.

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[metalmole]

I have a Grizzly G4003, they look like the same lathe....I have been having the same problem with my threads, they have a slight chatter pattern, its not bad but its there if you look at it closely. If you guys could post some pictures of your fix it would be great.... also would like to see your collet chuck conversion, been thinking about that as well.....thanks..AD

 

[Pontiac Freak]

I picked up a dirty but low usage Enco 1236 belt drive lathe last summer and have just finished going through it and making it about as good as one of these little critters gets. It all started with irritation at the patterned spiral chatter finish produced during cuts. At first I chalked this up to cyclical feeding from poorly cut gears but this really was not the issue. I was noticing that my tenth reading dial indicator would "flutter" about .001" with the motor running and nothing rotating. I rebuilt the motor (new bearings) and changed out the belts and the problem still persisted. What was happening is that the motor, because of the way it is mounted behind the lathe, sets up a harmonic vibration that is imparted to the turned finish when the lathe runs. What I did to nearly eliminate this was pretty crude--I made a wooden wedge and tapped it between the motor & the back casting of the lathe base. To completely eliminate the issue I may install a 3 phase motor or DC motor and use rubber isolation mounts, but it works so well now I most likely will leave it. The motor mounts for these lathes are a hinged steel plate adjusted by a length of allthread. Apparently the mechanical resonance of this mess is such that the whole lathe buzzes during operation. With the wedge this resonance is at a different frequency and the lathe is smooth. There is a HUGE difference. Some other items to look out for: chips embedded in the drive gears. One chip between 2 gear teeth will create a cyclical feed pattern.
I will post some pictures of what I did to this lathe if anyone is interested. It isn't a Hardinge, but it works pretty well now. I have the head adjusted so that it cuts straight and the new Polish chuck I put on it has very little runout. I also adapted one of the hex 5C collet holders I use on my Bridgeport for use on the lathe. It works well and I will make a post on my Quick & dirty collet chuck conversion if anyone has interest.
Skip

I would really like to see your pictures of the collet setup!