[yeepman2]

Are the spidle belt idlers supposed to turn 360 degrees when the belts have no tension?Mine only turn about 30 degrees and the belts squeel when I turn the spinle on.The cylinders seem to stroke all the way.

[Roy's cnc]

Which model machine?

[yeepman2]

It an 1988 904-1 4020 with 10k spindle

[AndyB]

How are the belts ? are they cracked, are they clean, aligned properly? The idler pulleys turn on a crank arm, are they aligned, or are they loose up and down? Also check the spindle motor mount? grab the motor and push back and forth.

[DareBee]

The factory motor mounts are rubber and often need replaced in older machines.
I just did mine with solid mounts.
About $50 to buy.

[Roy's cnc]

The idler wheels should roll freely. They have 2 sealed bearings in each wheel . Pull the mounting block for the cam,ram assembly,hold the motor up with a wood block ,allen screw in the idler wheel shafts. You may need a simple pully puller to remove. Replace 2 bearings in both pullys as they are very cheap. Check carefully the inside of the wheel, as the bearing could have spun inside it. As these are no longer available you can weld the inside and rebore. They are not hardened wheels. Good luck, not too hard to do. Ps. Gooood time to change belts during this teardown.

[nathwil]

I replaced the idlers on our 3060 because the belts were squealing verry badly. This was done after I installed new belts because I was "sure that was the problem." When that made no change I started looking at the idlers. I ordered new idlers and wehn they came I pulled out the old ones. They are now sitting in my tool room just in case they are needed on another machine. The mounts were the source of the squeal. They start to get soft and the pullys get out of alingment just a little.