taper bearings

[Ian L2Participant @ianl2]

Posted by Michael Gilligan on 12/12/2014 16:12:32:

Ian,

I just found this 'archive' of notes

There may be something useful in amongst them.

… I suggest you grab a copy in case it disappears.

Found and saved Cheers Thanks

[Max ToleranceParticipant @maxtolerance69251]

Depends entirely on how accurate you want your lathe to run. I would never even consider mixing old and new bearing parts. Bearings usually wear because of either bad fitting or lack of lubrication/ingress of contaminants and if yours are worn then they are worn all over. When the lathe was first manufactured the Timken bearings were fitted because they are specially designed for machine tool spindles. The design of these bearings is very specialised and there is a massive difference between them and the "common" taper roller. Timken normally sold these bearings as pairs or sets and they were designed to run with a certain amount of preload. If fitted correctly they would run as sweet as a nut as long as the lubrication was adequate and of the correct grade and quality. Fitting commercial quality bearings would be o.k. but don't expect super fine surface finish, chatter free machining etc.

Colchester and Harrison among others changed to using Gamet (pronounced Gamay) bearings and even put a plate on the outside of their lathes to advertise the fact. These are also a very high quality unit often manufactured to special order (and odd sizes !!). It is worth remembering that as a previous poster noted the price reflects the quality. Unfortunately machine tool bearings are usually the best quality for the reasons given above.

It is still possible to buy matched sets of bearings to order but obviously this is reflected in the price. Many of the far eastern manufacturers at the budget end of the market use the lower quality type in order to keep prices down (and this can be heard and felt if you choose to do so).

It is also worth noting that bearings have a shelf life if unused. Often the lower priced bearings offered for sale have exceeded this and have been sold off cheaply hence the "bargain" price.

[Ian L2Participant @ianl2]

Hi Max

Some good points "why do they have shelf life" its one of the occasions that one could end up spending more restoring than the cost to purchase new budget lathe. Problem is having never had this lathe running I am unsure on how good or bad it is, it looks as its done very little for a very long time and to get the bearing off it required the hydraulic press which has not done it any good. I'm hoping a contact has some good used parts once running I can decide if it justifies the extra expense to perfect it.

[Max ToleranceParticipant @maxtolerance69251]

The reason for the shelf life is because the bearings are shipped in a preservative oil or coating in cardboard boxes usually. This coating is intended to protect the bearing from corrosion due to the atmosphere and acids from the cardboard and general storage conditions. If the surface of the bearing is allowed to oxidise or become pitted from corrosion then the bearing service life is severely shortened . Reputable bearing factors rotate their stock constantly and will return unsold out of date stock to the manufacturer (or sell it to bargain suppliers) The problem comes when the preservative has aged and becomes unreliable allowing for the deterioration above. One of the problems with early far eastern cars was the corrosion caused by the long sea journey in salt laden atmospheres. This also is the reason for minimal handling of bearings before use, your skin is salty and corrosive.

Bearings unfortunately are often unwittingly abused by ignorance and misunderstanding. As for whether the cost is justified I cannot comment, not having seen your lathe. However these older machines were usually very solid rather over engineered pieces of kit and if the slides and lead screws are good then they are far superior to the modern budget machines in every way. If however the slides are very worn or damaged and you are not able to get them back to good order then maybe you do need to decide how best to spend your money.

I currently have about fifteen different lathes (I lost count a while ago and it pays to be hazy when the wife enquires where her house keeping has gone !!!!) All of them are older ex industrial machines ranging from tiny 6mm watchmakers up to a Colchester triumph long bed and all of them have been lovingly restored where needed. They are a privilege and a pleasure to use and the work produced is first class and accurate. That is what I need in order to produce my models to the standard I want. Not everyone needs to work to the tolerances I do and many find the modern machines well up to the demands they need. As the old adage goes you pays your money and take your choice. I should add that I am referring specifically to the budget machines, the better industrial type machines produced in the far east can be as good as any but you will find the price matches!!

[Neil WyattModerator @neilwyatt]

I would recommend contacting Arc Euro trade and asking for advice on a replacement. The proprietor, Ketan, was a bearing specialist before he went into the ME business.

Neil

[Ian S CParticipant @iansc]

With the threaded nose, if it's as damaged as you say is there enough meat to turn off the old thread plus a little bit, cyt a fine thread, then make a sleeve with a matching internal thread, assemble it with Shaft Lock Loctite, then cut a new nose thread. Better fix the bearings first I suppose.

Ian S C

[Russell EberhardtParticipant @russelleberhardt48058]

I think the other Ian was referring to the threaded part at the back of the spindle rather than the spindle nose:

The threaded collar B applies the pre-load to the bearings. There is plenty of meat available to just turn off the old thread and cut a smaller diameter thread and make a new collar to suit.  No need to change anything else.

The drawing is for the under-drive version with the back-gear under the spindle but the principle is the same.

To use the bearings without the flange, the inner oil baffles could be replaced with flanged retainers screwed to the inside of the headstock. You will have to be careful that they can support the pre-load which is set with the spindle at working temperature (about 25 C above ambient) by tightening the collar until all fore/aft play measured with a dial gauge is eliminated and then given another 1/16 of a turn.

If Ian L2 would like a copy of that drawing I have put a higher resolution version here

Russell.

Edited By Russell Eberhardt on 14/12/2014 17:11:50

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