Leblond Regal 15" knocking timing pulley

MEDTECH · Sep 4, 2017

Hello good morning everyone,

I like to request the benefit of the wisdom and knowledge of the forum. So I'll lay out the story behind the problem.

I purchased this nice 15 inch Leblond servo shift from a school auction last year and have just recently started using it after building a RPC for it. Since it has a 7.5 hp motor it took me a while to find another motor to convert.

At first I used a VFD to run the lathe at low speeds and was successful in testing functionality but now that I have run it at full speed I noticed a knocking noice when high speeds are engage 640 -1200. After examination and looking all over the internet everything was fine but then I observed when I turned the spindle with a power drill, that it was coming from the high speed spindle. Closer examination revealed that the timing pulley has a little play and each revolution it clicks. It's not a major play but with the pressure from the timing belt it clicks noticeably at high speeds

I looked for set screw to tighten but found none, so I though I could drill and tap to add one but also figured it's a design feature and I should just let it be. After all I don't think it will wear out the shaft and the pulley in my lifetime with it, or then again it might?

What do you think? Has this been seen On Other lathes?

Thank you in advance

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moonlight machine · Sep 4, 2017

MEDTECH said:
Hello good morning everyone,

I like to request the benefit of the wisdom and knowledge of the forum. So I'll lay out the story behind the problem.

I purchased this nice 15 inch Leblond servo shift from a school auction last year and have just recently started using it after building a RPC for it. Since it has a 7.5 hp motor it took me a while to find another motor to convert.

At first I used a VFD to run the lathe at low speeds and was successful in testing functionality but now that I have run it at full speed I noticed a knocking noice when high speeds are engage 640 -1200. After examination and looking all over the internet everything was fine but then I observed when I turned the spindle with a power drill, that it was coming from the high speed spindle. Closer examination revealed that the timing pulley has a little play and each revolution it clicks. It's not a major play but with the pressure from the timing belt it clicks noticeably at high speeds

I looked for set screw to tighten but found none, so I though I could drill and tap to add one but also figured it's a design feature and I should just let it be. After all I don't think it will wear out the shaft and the pulley in my lifetime with it, or then again it might?

What do you think? Has this been seen On Other lathes?

Thank you in advance

Sent from my iPhone using Tapatalk

I have a Servo Shift Regal that I have been using daily for 10 years. A fine machine that definitely does not have a knock as a "design feature". The timing belt pulley on the spindle is a tight fit and held in place with a snap ring, it should not be loose. The other timing belt pulley is locked on the shaft by a tapered hub, if it is loose tighten the 3 bolts on the hub. Many years ago mine got a knock, it was the driven v belt pulley. It is held on with a peg spanner nut. The nut is locked in place after tightening by a set screw through the nut hitting the pulley, not the shaft. Fix the problem properly, adding a setscrew is not a proper repair. If there is clearance and you add a setscrew the pulley will be off center causing vibration issues. I do have some headstock parts including extra timing belt pulleys.

MEDTECH · Sep 4, 2017

Leblond Regal 15" knocking timing pulley

Thank you moonlight machine, I went back to check the driven pulley,it is properly secured with no slop, when I checked the drive pulley it's strange. When I rock it back and forth it clicks, I took off the snap ring to review and there was the culprit, the pulley seems to be egg shape for lack of a better term. I though of putting shin stock to take up the slack?
Leblond Regal Knocking - YouTube

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moonlight machine · Sep 4, 2017

MEDTECH said:
Thank you moonlight machine, I went back to check the driven pulley,it is properly secured with no slop, when I checked the drive pulley it's strange. When I rock it back and forth it clicks, I took off the snap ring to review and there was the culprit, the pulley seems to be egg shape for lack of a better term. I though of putting shin stock to take up the slack? I'll try and upload a short video clip of it

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Remove it and check the spindle for damage. If it is OK I have a good tooth belt pulley I can sell. How wide is your pulley? There should be no slop in it. Mine is size on, a tight fit unless you warm it up a bit. Shim stock and 620 Locktite may fix it but it is a of a bit half ass way to do it.

MEDTECH · Sep 4, 2017

Leblond Regal 15" knocking timing pulley

I measured 1 3/8" wide, I set the shin stock and boy was it in need.

I used the following feeler gauges as shim stock:
0.15 mm
0.10 mm
0.08mm

I'll have to live with it for a little while before I tear it up, I was hopping to get a project done on the four day weekend but instead spent time troubleshooting this knock, I'll defenetly replace the pulley but I'll wait a few weeks before I tear it and inspect, I'll get in touch with you to confirm the dimensions, thank you

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moonlight machine · Sep 4, 2017

MEDTECH said:
I measured 1 3/8" wide, I set the shin stock and boy was it in need.

I used the following feeler gauges as shim stock:
0.15 mm
0.10 mm
0.08mm

I'll have to live with it for a little while before I tear it up, I was hopping to get a project done on the four day weekend but instead spent time troubleshooting this knock, I'll defenetly replace the pulley but I'll wait a few weeks before I tear it and inspect, I'll get in touch with you to confirm the dimensions, thank you

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Some dumb ass has put it on the wrong way around! That is a hub, straight on the inside, tapered on the outside. There is a flange on the other side with 3 bolts to tighten the hub to the pulley and pinch it down on the shaft. Normally you put the pulley on with the bolts out so you can tighten them. Don't be tempted to reach around with a long wrench and tighten it up. If you ever have to remove it you need to be able to remove the bolts and put them in the jack screw holes to push the taper hub out of the pulley and release the shaft.

MEDTECH · Sep 4, 2017

That makes sense, I rotated the shaft a couple RPM's and saw I still a little more gap, used three more fillers but now it's true, I checked the back of the pulley but I did not see any screews or holes, I also looked at the parts diagram but it doesn't show them either, I feel I most definitely will find out out when I remove the pulley and inspect

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moonlight machine · Sep 4, 2017

MEDTECH said:
That makes sense, I rotated the shaft a couple RPM's and saw I still a little more gap, used three more fillers but now it's true, I checked the back of the pulley but I did not see any screews or holes, I also looked at the parts diagram but it doesn't show them either, I feel I most definitely will find out out when I remove the pulley and inspect

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My lathe has the pulley I described. The spare pulley is as described. You have the narrow timing belt, my lathe has one about 2" wide. The spare pulleys I have are for the narrow belt. I have a high speed shaft as well. Another LeBlond I have worked on has the same pulley set up. I have never seen one without a taper lock hub but that does not mean they don't exist.

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