Retaining bearing on small shaft: press fit, snap ring or bonding?

[kjoiner]

Hello,

I have a small lead screw application and am considering methods for securing the bearing to the screw. The screw will have around 95lbs axial force in one direction and could occasionally have 10-20 lbs in the other. I'm turing the end of 3/8 x .500 lead screw down to 1/4 x 1.75" for the bearing and timing pulley drive. The shoulder on the screw will handle the large axial load but I've got some options for the other direction:

1. Press fit
2. Turn a groove into the shaft and install a snap ring
3. Use a bonding or retaining agent
4. Nut - would have to turn down and thread the shaft which drives up cost and weakens the shaft

The screw is SSTL and the bearing is a standard single row bearing - .250 bore, .750 OD, .281 thick, sealed.

If I press fit, I will have to press the bearing over 1.75" down the shaft and I would have to keep tighter control over the diameter which drives up the cost.

Mainly I'm interested in experience/opinions on using a retaining agent.

This application is not precision positioning - we can tolerate ±.03 of endlplay etc.

Thanks,

Kyle

 

[MikeHalloran]

A press fit on a small diameter requires extremely close tolerances.

Loctite, properly applied to properly toleranced clean surfaces, is incredibly strong. Note that some minimum clearance is required; see the data sheet. Call your Loctite rep for help.



Mike Halloran
Pembroke Pines, FL, USA

 

[kjoiner]

Mike,

Thanks for the reply. The close tolerances are my concern as well and I would probably have to resort to cooling down the shaft since I can't heat the sealed bearings.

I'll take a look at the loctite data and see what I can find. Do most people use something like 271 or do they use a special version?

Kyle

 

[MikeHalloran]

The grade you should use depends in part on the clearance you can maintain, which depends on the tolerances you can provide. For example, 271 will work with very little clearance, but you might want a grade with higher viscosity to deal with a larger clearance. It also depends on the materials involved and the bond strength you need. That's why I suggested getting your local rep involved; they can be very helpful.





Mike Halloran
Pembroke Pines, FL, USA

 

[kjoiner]

Mike,

I looked at the Loctite web site and found a couple of products that are for retaining shafts etc. We use 271 in house quite a bit, but I think I'll try some of the products made for the application as well and do a comparison between the two.

Kyle