Engage large threads without cross threading
Engage large threads without cross threading
(OP)
I'm designing an axial adjuster for positioning the outer ring of a tapered roller bearing, to control end play. One method for doing this is to use shims under the retaining flange. My client and his customers have been doing this for decades and have found it very awkward, and have asked me to come up with something better.
The bearing outer ring o.d. is 7.125". I am considering making a threaded adjusting ring to adjust the position of the bearing outer ring. The adjusting ring would have 7.375-8 male threads which would engage with female threads in the housing. However, I am always leery of large threads that will be assembled by hand, because it is so easy to cross thread them. I thought it might help to have a cylindrical male pilot diameter that registers with the minor diameter of the female threads before the male and female threads actually start to engage, but I'm not sure this would be enough to assure reliable thread engagement.
Any suggestions regarding ways to help assure reliable thread engagement would be appreciated.
The bearing outer ring o.d. is 7.125". I am considering making a threaded adjusting ring to adjust the position of the bearing outer ring. The adjusting ring would have 7.375-8 male threads which would engage with female threads in the housing. However, I am always leery of large threads that will be assembled by hand, because it is so easy to cross thread them. I thought it might help to have a cylindrical male pilot diameter that registers with the minor diameter of the female threads before the male and female threads actually start to engage, but I'm not sure this would be enough to assure reliable thread engagement.
Any suggestions regarding ways to help assure reliable thread engagement would be appreciated.





RE: Engage large threads without cross threading
RE: Engage large threads without cross threading
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Engage large threads without cross threading
RE: Engage large threads without cross threading
Kinematically, think of a steamboat jack, with two differences from classical form:
Instead of right and left hand threads on opposing ends of the adjusting spindle, both threads would be of the same hand.
The threads would be of slightly differing lead.
I.e., the adjusting ring would be double ended, with 7.375" threads as described, except one end would have a lead of 0.1250", and the other end would have a lead of 0.1240" or maybe 0.1230", depending on how much range of adjustment you want.
Distributing the tolerances will be fun....
Mike Halloran
Pembroke Pines, FL, USA
RE: Engage large threads without cross threading
Thanks very much for your input.
Geesamand - speed and running accuracy running requirements are low, so end play allowance is fairly generous - it amounts to about 29 degrees of rotation of the adjuster.
Greglocock - I like your idea - I'm going to give it a try. I'm also going to mark the parts where the threads end, so the assembler can line up the parts to immediately start a clean engagement.
RE: Engage large threads without cross threading
Also consider that a threaded retainer would need to incorporate some sort of device to lock it after adjustment. One benefit of using shims and a flanged retainer is that no adjustment should be required if the bearing was simply removed and reinstalled, while a threaded retainer would require readjustment.