Step pulley question: Should i tap and install a set screw?

[modela]

What should I do with the set screw in this situation?

I have been rebuilding a Nantong. Large drill press and came up with a dilemma in the step pulley. Pictured below is the shaft with key.

There is a hole drilled in the pulley that lines up with the key but there are no threads in the hole.

Shown below is the pulley slipped on the shaft. My question is should I tap the hole and put in a set screw or leave it as it is. I have worked with Chinese equipment before and have seen things undone and left out. Your experiences would be helpful here.

 

[12bolts]

James,
There really should be a set screw in there to stop the pulley moving about. The key takes care of the torque but you dont want the pulley sliding around on its keyway. Is the thread stripped out or just never tapped. You probably dont want a huge grub screw in there if its already been tapped before. Is there length on the key to move up or down one pulley groove and still hit it somewhere near the middle?

Cheers Phil

 

[Tony Wells]

Affirmative. There should be a socket set screw there.

 

[modela]

Hi Phil,

The hole lines up toward the top of the key. The key is clean like a set screw had never been installed. I think there is enough meat to tap the existing hole but it seems like it should be more toward the middle of the key. It would have to be drilled and tapped down lower to hit the center of the key.

I will probably set the motor up there and see how it lines up.

I have seen similar defects in Taiwanese tools. This drill press looks pretty good although the castings are pretty rough.

Jim

 

[Pacer]

Oh, definitely get a set screw in there! In fact, if its never had one and the motor ran even a little bit theres probably excess 'slop' in the shaft. If you can feel any looseness when the pulley is on the shaft, then add another set screw -- or even two (Like on this Chinese stuff) On my 4x6 band saw I had the have 3 screws to stop the rattley sound it would make.

 

[kd4gij]

looks like someone drilled out the setscrew. I would put a heli coil in there with locktight let it sit over night then install it.

 

[modela]

looks like someone drilled out the setscrew. I would put a heli coil in there with locktight let it sit over night then install it.

I would think so except there are no marks on the key. But that is possible.

Jim

 

[November X-ray]

Chances are if it was drilled out, it was probably done so while on the shaft and the key was damaged and then replaced. As suggested you could install a heli coil or drill a new hole and tap it in another groove below the existing hole.

 

[george wilson]

The best thing is a short setscrew with ANOTHER set screw tightened down over the first one(both buried in the hole). Quality machinery usually uses the double set screw to make sure it doesn't vibrate loose. Even my old 8" Delta jointer with a die cast motor pulley used a stacked set screw. So does my Hardinge HLVH lathe. If you don't realize there's another set screw in the hole,and try forcing something off a shaft,you'll groove the shaft,so keep this tidbit in mind.

 

[Tony Wells]

They also make a socket jam screw. Like a jam nut, they are thin and designed to lock against the set screw.