Head Stock Bearings

[Alan .204Participant @alan-204]

Hi chaps been having problems with the Bantam Lath can't seam to get a very good finish so after going through every thing I can think of its time to change the head stock bearings, have them out so hopefully tomorrow will try to get some new ones, so I was wondering how do I know when I fit them if they are too tight or not, how do you tell, other thing I will need to make a new gasket on one end or is best to use some gasket sealant, one more question the oil level sight glass leaks oil but I can't see how you get it out has any one taken one out of a Bantam before if so how do you do it with out breaking it.

Thanks Alan.

[Alan .204Participant @alan-204]

[Anonymous]

Seems rather radical, are you sure you've tried absolutely everything else?

Andrew

[Alan .204Participant @alan-204]

yep.

[JasonBModerator @jasonb]

If you don't know how to set the new bearing preload how do you know its been correctly set on the old ones?

Before pulling them I would make sure the existing have been properly adjusted.

[Michael GilliganParticipant @michaelgilligan61133]

Alan,

Have a look through this thread on RCgroups

Skip lightly through the banter and there are some useful comments and contacts.

MichaelG.

[TrevorhParticipant @trevorh]

Hi Alan,

When pre loading bearings that run at a wide range of speed we use to use the "rule of Thumb" method .001" per 1" dia of the largest Chuck to get the amount of end float, run it up and then check the Bearing Temp, making sure not to under lubricate or over lubricate ie apply the grease by finger

cheers

[Russell EberhardtParticipant @russelleberhardt48058]

Note that, as the bearings heat up, the spindle expands so it's best to make any adjustments after it has run for over half an hour. The instructions for my lathe (not a Colchester) suggest adjusting until the end-float is reduced to zero and then tightening the adjusting nut a further 1/16 turn. Of course that will depend on the pitch of the adjusting nut thread.

Russell.

[Russell EberhardtParticipant @russelleberhardt48058]

Note that, as the bearings heat up, the spindle expands so it's best to make any adjustments after it has run for over half an hour. The instructions for my lathe (not a Colchester) suggest adjusting until the end-float is reduced to zero and then tightening the adjusting nut a further 1/16 turn. Of course that will depend on the pitch of the adjusting nut thread.

Russell.

[KMPParticipant @kmp]

Alan

I wrote the guide mentioned in the reference given in Michaels’ post and will send you a copy if it would help.

Taper bearing adjustment is somewhat subjective unless you can very accurately measure the torque on the shaft. It is also affected by many factors as have already been mentioned and will require some running checks and subsequent adjustment after initial fit and setup. With a little trial and error however it is fairly easily achieved and will result in bearings that last many years. The Gamet bearings in the Bantam are superb but very expensive; unfortunately trouble is not that unusual if it has been run for years without proper adjustment. If yours is fitted with the originals I would inspect them closely to ensure that replacement is necessary as changing for new cheaper bearings may not improve the situation. Main issue when adjusting is the inner race sticking on the spindle which makes the fine adjustment difficult.

Let me know if a copy of my rough (very) guide will help and I will send you a copy.

Best regards

Keith

[Alan .204Participant @alan-204]

Thanks chaps for the reply,s, Keith they are Gamet bearings they are not too bad but will see how much new ones are before I put it back together Gamet bearings closed a long time ago apparently so will have to see what they come up with, your information would be gratefully received, every little helps as they say.

Alan.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I'm not familiar with the Bantam,but below shows the method for another make of lathe biginning with B.

A similar method may be able to be used for any spindle with taper roller bearings configured as in my skecth below, but you should go by the makers recommendations.

Regards Nick.

[KWILParticipant @kwil]

Alan,

According to the 600 Group current web page showing 2013 Preliminary Results they still make Gamet bearings, so when did they close?

K

Edited By KWIL on 02/07/2013 14:29:11

[Michael GilliganParticipant @michaelgilligan61133]

The Gamet web-site is "live" but it's strange that the latest Press Release is dated 2009.

MichaelG.

[Sub MandrelParticipant @submandrel]

Hi Nick,

That's very useful, but what If I have only got metric string!

Neil

[frank brownParticipant @frankbrown22225]

Many years ago when I was an apprentice, the boss thought that an evaluation of our machines was overdue. The lead apprentice then got hold of a lump of 4" X 2" wood and lifted the mounted chuck of our Southbend lathe by about .01", so not much wear then!. Anyway the boss then wrote a note saying that the lathe was required to be replaced, to the managing director. This chap came down to our workshop in his suit, took his jacket off and proceeded to a, grind up a lathe tool and b, surface a bit of 2" bar. The results were an eye opener, fantastic finish and only tenths of taper. Needless to say, we did not get our new lathe!

There are many factors that govern the final finish on a turned surface and unless the bearings are actually running rough, I would think that the wear in the bearings rank low down in the list of possible causes.

Frank

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Neil, I guess you could buffer your metric string between the lbs spring balance with one that reads in Kg and then fit some sort of adaptors to your shoes, so that you can walk backwards in M's/mm's instead of your feet, that should give you an instant metric conversion.

Regards Nick.

[KMPParticipant @kmp]

Alan

Have had problems with BT but now fixed so if you would like a copy of the rough guide please send me PM with an email address.

The "string" method is well known and works for some, we always found that it was extremely sensitive to the speed of pull particularly when setting very lightly loaded bearings with minimal drag. We felt it was very prone to applying excessive pre-load and very easy to adjust your speed (subconsciously) to get the reading necessary. A simple pulley with a known weight to provide the pull was supposedly more consistent.

Neil

Right hand pull for imperial and left hand for metric, unless of course you are left handed then it's all reversed again. The real problem is mixing metric and imperial string as the effective radius of the pull is changed

Regards

Keith

[Sub MandrelParticipant @submandrel]

You guys are tying me in knots!

Neil

[1Participant @1]

Rather sounds as if they're stringing you along Neil.

Jim

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

You can identify rough running bearings just by listening to them via a screwdriver – doesn't even need any real skill and saves a lot of stripping down to examine bearings visually .

More sophisticated versions of the same thing using electronic detectors and processing are available as standard equipment in industry .

The most common cause of premature failure of rolling contact bearings in machinery is not putting on enough preload .

The second most common cause is putting on too much preload .

Premature failure of properly set up bearings due to normal working loading in a quality lathe is actually a quite rare event .

MikeW

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