# SB 10L Toothed Spindle Drive Belt



## HMF (Aug 23, 2011)

This question was asked on another forum, and was not really answered (or answered in a flippant way), so I wanted to post it here and see if we can get some salient answers.

Thanks,

Nelson

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I hope to finish up the rebuild on my 10L this Fall. One of the things I need to look at is the spindle drive. As a bit of background, I got the lathe without a cabinet, so I need to build one. It is a 4' hard bed, large dial, D1-4 spindle with a taper attachment. I have the underdrive pulley assembly but will not use it. I plan on doing a direct drive with a PM servo motor and I already have all the electronics. I would like to use a toothed belt like an HTD or XL series so I won't need a second encoder directly off the spindle shaft to compensate for belt slip when threading with the servo driven leadscrew. I would make or modify the spindle pulley for the toothed belt. 

I am worried that a toothed belt could induce vibration that would affect the surface finish. All the small lathes I am familiar with use a flat or V belt. I am sure that the larger CNC lathes must use a toothed belt with their higher horsepower, but they have a lot more mass in to soak up any vibrations and they are using tapered or roller bearings not a plain bearing. So, am I over-thinking this? I'd appreciate any pro's and con's.


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## Tony Wells (Aug 23, 2011)

I wouldn't hesitate for a second to make a change away from a V section belt. A cogged belt, or a synchronous drive belt is what they are generally referred to as. You might pass this along.


http://www1.eere.energy.gov/industry/bestpractices/pdfs/replace_vbelts_motor_systemts5.pdf


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## Tony Wells (Aug 23, 2011)

*Re: SB 10L Toothed Spindle Drive Belt*

Right Dave, I shouldn't have included that in what sounded like a recommendation.

Quote from that article:

Synchronous belts are the most efficient choice. *However, cogged belts may be a
better choice when vibration damping is needed or shock loads cause abrupt torque
changes that could shear a synchronous belt's teeth.* Synchronous belts also make a
whirring noise that might be objectionable in some applications.

Part of that is the shape of the "teeth". Some are more rounded, and some have more of a squared tooth profile.


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## Tony Wells (Aug 23, 2011)

Well, I knew that already, but doing a handful of other tasks along with posting here kind of made me fail to mention that part of it. Synch belts do well at low speeds, but cogged belts do much better.


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## Tony Wells (Aug 23, 2011)

I've seen them on 30hp VMC spindle drives, so they can't be all bad. I'd still do it. There are variants for low speed, high torque applications, and those for high speed, such as the VMC spindle.


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## joesmith (Aug 29, 2011)

dud u make the large pulley? If not source? joe 

BTW nice job!.


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## pdentrem (Aug 29, 2011)

Just a viewpoint on this style of belt.

I just ordered a 800H200 belt at 105 bucks for our primary rolling mill. 
The speed of the mill is not fast due to gear reduction box but at the bottom end you can hear the individual tooth engaging the gears. No vibs due to the massive weight of the machine. The one on the machine is 15 years old. I am just getting a spare as the machine can not be down for long. We just serviced the DC motor and motor controller. The controller went down and since I had to wait I pulled the motor as there were birds living inside. Bad bearings and changed the brushes.


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