[rrbmachining]

I am resigned to the fact that I will have to strip and clean the worm drive on my HRT 210 rotary table. The gear has virtually siezed probably due to contamination. Has anyone had to do this and can offer any advice or know of any pitfalls
Any help or advice would be much appreciated

[Machineit]

Dear rrbmachining,

I haven't had a 210 apart, but I have taken others apart, such as my SRT.

First, I'm assuming that the unit had oil in it. I would check it to see if there is any metal in it. The worm shaft is hardened steel and the worm gear is generally bronze.

Since you said it was binding up, I assume you have the cover off. There are bearing plates on either end of the unit, (where the degree dial is on the outside and under the belt sprocket on the inside). They are usually held by 4 bolts on each. These are the bearing plates for the worm shaft. On the bottom of the unit are two small set screws, under where the worm shaft is. When you loosen the two plates, you can adjust the backlash on the shaft by tightening or loosening these two screws, which move the shaft itself. This is how the worm shaft is adjusted to the worm gear. If you back these off slightly and the worm shaft turns more easily, then you have a problem with the worm gear system. If it just gets sloppy, but still turns hard, then you have a problem with the bearings for the platter itself.

If my memory serves me correctly, if you remove the bearing plates from each end of the worm shaft, you can remove the worm shaft and check it directly and also look at the worm gear through the opening. My unit is older and has the bronze and cast iron bushing system, your has standard ball bearings. It's a better system, but more parts that can go bad break off and get caught in the gear.

Just a note: If you reassemble the shaft back in and are setting the backlash, the bearing plates must be snugged up somewhat, but not tightened. Them being too loose during adjustment will make it way tight when you do tighten the bolts as the shaft will move when they are tightened. It kind of the little game of check and check after tightening.
So, start there and let us know what you find out.

Cheers---Mike