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Just recently finished a full tear down and rebuild of a mark v. Replaced all the bearings minus the quill bearing, waxed everything and rebuilt. Two things have happened. First, using the ss as a drill press, the drive shaft was pulled out of the headstock when a drill bit got stuck in a piece of wood (fortunately not while running). Put it back in and it ran with no issues. Fast forward a few weeks, I mount a spindle blank and the main spindle stops spinning when i get near top speed (not sure how fast). Ran the speed down and turned it off. Waited a couple minutes and turned it back on. The main spindle is hot to the touch. Any ideas where the problem might be?

DGear74 wrote:Just recently finished a full tear down and rebuild of a mark v. Replaced all the bearings minus the quill bearing, waxed everything and rebuilt. Two things have happened. First, using the ss as a drill press, the drive shaft was pulled out of the headstock when a drill bit got stuck in a piece of wood (fortunately not while running). Put it back in and it ran with no issues. Fast forward a few weeks, I mount a spindle blank and the main spindle stops spinning when i get near top speed (not sure how fast). Ran the speed down and turned it off. Waited a couple minutes and turned it back on. The main spindle is hot to the touch. Any ideas where the problem might be?

Did you reinstall the quill bearing retaining ring?

Is the poly-v belt tension correct?(assuming you do NOT have a gilmer drive). A slipping belt will create heat.

I have a Gilmer belt. I did install the retaining ring on the spindle side. I had one retaining ring that I couldn't get back in on the gilmer side, I may not have gotten the bearings pressed enough.

Could the spindle assembly be slipping where it inserts into the drive sleeve assembly?

On the high-speed slipping issue only:

In order to determine what is slipping, observe your upper and lower auxiliary spindles in addition to the quill spindle. In sequence, the motor drives the lower aux, which drives the upper aux, which drives the quill spindle.

Most likely, IMO, for high speed slipping is that you are losing contact between the lower belt and the "idler" shaft (lower aux). (In the test above you would see that none of the spindles are turning at the right speed.) Possible contributors are lower belt compatibility (i.e an improperly substituted part), lower belt wear (should be at least 0.50 inches at the wide part of the "V"), a high speed alignment error simply allowing you to move the pulley sheaves too far apart with the speed control, or something preventing the motor sheaves from reaching the high speed position (close together).

Many Gilmers have a clutch, which I guess could be slipping, but I'd expect that more as a low speed high torque thing. Same for what you asked, spindle slipping where it inserts into the drive assembly.

-David

Thanks for the reply, I will check that out. On low speed, if i rest my hand on the spindle it will momentarily stop spinning.

When you say high speed alignment error, could it be that when I did my high speed adjustment I set the speed too high?

Could the issue be too much tension or not enough in eccentric bushing?

-Dylan

OK with a Gilmer, only the motor belt will cause slipping.(ignoring the clutch)

The motor pulley(floating fan sheave) is the likely culprit. The pulley is not closing sufficiently to maintain belt tension. If so, the idler shaft will also be 'slipping'.

I am assuming the gilmer belt is not slipping cogs(too little eccentric tension).

Spindle not likely slipping in the drive sleeve.

Both drive sleeve retaining rings should 'fit'.

Gilmer Belt is not slipping.

When putting the headstock back together, I could not get the drive sleeve assembly in and both retaining rings, which I think is due to the bearings not pressed together tight enough. I needed 1/16 in or less for both to fit. Try as i might, i couldn't get them any closer without a press, which I don't have at home.

Is it the tension of the spring on the floating fan sheave?

/////

I adjusted the tension on the eccentric bushing, put some 3 in 1 on the fan sheave. So far that seems to have fixed it. I also moved the spindle knob just a hair, apparently it was rubbing against the spindle. I let it run for a minute and it wasn't getting hot.

Thanks for the help gents, I'll try to get some real time on it this weekend and will post an update.

-Dylan