Taper bearing endfloat

Hello all, I'm asking for advice again,please bear with me! I have fitted new taper roller bearings to the spindle of my Hobson H7 lathe and I need advice as to what preload or endfloat is appropriate. I have set them to give a total endfloat of 0.001", is this too much? as the rear bearing is fairly tight fit on the spindle I am wary of over tightening the threaded adjustment collar and not being able to readily reduce excessive preload thus introduced. In any event is a running in period necessary before final adjustment?Thanks in advance for any replies.

Regards Paul

Yes, endfloat for taper bearings should be zero, unlike plain bearings they should have either no or very small amount of preload.

For critical applications you raise the preload until a noticeable temperature rise is detected and back off a little.

For us mortals, run the bearings until at normal operating temperature, then adjust to just get rid of any float or shake. Run at operating speed for a decent time and make sure they don't overheat.

When greasing before assembly aim to fill about 25% of the space in the bearing, no more.

You may hear otherwise, especially advice suggesting higher preload, but this is a much condensed version of advice from at least two authoritative sources.

Neil

Edited By Neil Wyatt on 10/05/2015 17:09:09

Hi Neil,

Thanks very much for your reply, I'll Just have to creep up on the adjustment! these are big thee inch od bearings and they are splash lubricated with nice clean oil now.

best regards Paul

Might be worth a nooge around one of the bearing makers websites for technical information before you start adjusting. The SKF site looks as if useful information may be readily accessible. Especially if you are reasonably tolerant of maths!

This sort of job I always like to run some numbers to get a feel of whats going on rather than just push on with an empirical technique, however well recommended. Saved me messing up by the numbers a time or two when either the situation for or my application / understanding of the empirical technique wasn't quite correct.

About 30 years back I had to install new Timkin taper rollers around 6" diameter in a lathe and Mr Timkins installation instructions were a bit more involved than simply testing the temperature. As I recall matters the temperature rise was considered primarily verification of correct, or incorrect, installation once the job was finished and a useful check that all is well during subsequent operation rather than something to rely on whilst doing the job. Darned if I recall the procedure now but I do know that I borrowed some decent gear from work to get the job done. With the ebst part of two weeks wages in said bearings now way was I gonna risk messing up.

Clive

Boxford used to specify a low torque value as a preload to its' small range lathes ( 4 1/2 & 5" . This was checked with string wrapped around a chuck and a small weight.

Some say the chuck should make one turn when given a good pull, others give an actual measurement and some give the torque value with the string around the chuck.
Warco's instructions are tighten them up so no play is seen and the chuck still turns freely so I'd go with that one, I also made a round tube from Aluminium and gave it a knock on the locking ring to make sure the bearing has moved on the spindle, mine is also very tight.

Steve

Hello all of you,

Thanks very much for taking the trouble to respond to my plea,I now feel more confident that I can adjust these bearings to an acceptable level without causing damage to relatively expensive bearings. I was quoted more than £200 for the taper roller at the nose end, luckily I was able to machine the spindle to allow fitting a bearing with a fractionally smaller ID 1.500 as opposed to 1.574. It never fails to amaze me that bearings from the same branded manufacturer can vary hugely in price especially from imperial to metric, economies of scale cannot account for these large variations.Thanks again to all of you.

best regards

Paul

Hi, actually it is their catch plate and a spring balance, but you should get the same result with a chuck using the formula in paragraph 7 below.

Regards Nick.

///hello Nick

Thanks very much for that information, I will invest in a string balance!

regards Paul