bronze bearings and machines?

[New_Guy]

ok not sure where i should put this, ill try asking this as clear as i can

years ago all machines had bronze bearings right and then slowly things changed and now roller and ball bearings are so well made and cheap they are the obvious choice for nearly everything

lets look at the lathe i have heard the old southbend's used tapered bronze bearings that are easy to adjust and even if you over tighten them its ok because they settle themselves out.

now an argument for a southbend copy (Hercus) was that Hercus lathes were better because they were the first to use tapered roller bearings and that improved the quality ???

so do tapper roller bearings improve the quality of a machine or is it simply a change in times where its cheaper and easier to use roller bearings and leave the bronze for special applications?

 

[Twmaster]

Here's a post that addresses some of your question. It's about halfway through his post.

http://madmodder.net/index.php?topic=2359.msg25087#msg25087

 

[Deanofid]

It's a good question.

I don't know if the Hercus was improved based on the bearings. Rolling bearings last a long time, and will let you run the spindle faster, but that may not make it better. Some older machines with bronze bearings will cut a really nice finish, and they will last too, as long as they are well oiled and adjusted right.

When it comes to SB lathes, a lot of old ones used plain cast iron bearings bored right through the headstock. No roller of any kind, and not even bronze or babbitt. I don't think there are many people who would call them lesser quality because of that.

Some smaller lathes, (relative term) used a kind of babbitt, and are still thought of as top quality machines. Think Myford, for one.

Just my two beans worth.

Dean

 

[Deanofid]

Just looked at your link, Mike. Another forum to mesmerize me!

DW

 

[Twmaster]

Geez Dean, are you stalking me?

 

[Deanofid]

Geez Dean, are you stalking me?

Ha!
I was here first!


Dean

 

[New_Guy]

lol

yeah i know Myford used to use white metal bearings, i thought the only problem was if they were not lubricated enough and running at to high speed they melted also heard if bronze is not lubricated enough the heat can make it bind and stick to the shaft i understand its common for this to happen with back gears

i know Babbitt bearings are not strictly for small lathes lots of engine lathes used Babbitt bearings but im not sure of any that are still in production

i just remembered that the clausing company tried to make a lathe better than the southbend lathe and one point they made was to use roller bearing ???

 

[Deanofid]

lol

yeah i know Myford used to use white metal bearings, i thought the only problem was if they were not lubricated enough and running at to high speed they melted also heard if bronze is not lubricated enough the heat can make it bind and stick to the shaft i understand its common for this to happen with back gears

If you don't lubricate rolling bearings, they have the same problem as babbitt or bronze. Self destruction. Neglect isn't a quality issue.

Most every manufacturer wants the buyer to think their product is superior to the competition. Changing something that worked perfectly well already doesn't necessarily make it better. It might. Might not, too. It might just sell better, because the buyer thinks it's better, so the change is made.

Was the Clausing a better lathe than the SB? Who knows? And better for what purpose?

Dean

 

[New_Guy]

yeah so maybe it was used as a marketing ploy in years past maybe by the bearing companies ??? maybe by the machine tool makers ??? i have to say if you talk big words to someone who doesnt know better they will believe it so maybe roller bearings were talked up to be more precise where now days it makes scene as bearings are so cheap sort of a win win

oh i read that post on mad modeler very interesting i knew that roller bearings still had vibration in the spindle, its good to know how to adjust them thanks for the link Thm:

on to tapered bearings the tapper is so any wear from normal use can but tightened up right? if the bearings are lose thats called end float right?

 

[Blogwitch]

You have to be careful between the differences in adjustment of ball raced bearings and tapered bearings.

Ball raced bearings in a lathe head shouldn't be tightened up together unless they have a rigid and accurate spacer between the two inner races, and even then the outer races should still be totally central to the inners, otherwise the bearings can be badly damaged.

Taper bearings are a different kettle of fish, the outer races are usually in a fixed position, and you tighten the tapered inner races onto them. The preload isn't just for taking up free play, but it does do that, it is to allow the bearing to take up the ideal running position, with little drag and little clearance (if any), only AFTER the spindle has reached running temperature. That is why you should always run a tapered bearing head for a short while before use, to allow the preload to be relieved by the expansion of the spindle due to warming up and extending a bit.

I hope that makes it a little clearer.

Tapered bearings are not the be all and end all to accuracy and good finishes as people seem to think, if you don't set them up and use them correctly, you are liable to get even worse machining problems than you had before fitting them.
I just wish that all these places selling these bearings as upgrades for a lathe, or any other machine, would at least give the correct preload figures for the actual bearings supplied, so they can be set up accurately, rather than relying on a rule of thumb setup.
But I suppose it is a matter of profit making rather than customer satisfaction.


Blogs

 

[New_Guy]

:bow:Blog i learn so much from your posts thank you, you are a very talented craftsman :bow:

i get why TRB's need a proper preload on a lathe man it gets difficult when you have to think about the spindle stretching not sure ill adjust the ones on my lathe until i know more :-[

so if you have a tapered Babbitt bearing to tight, to fast and heaven forbid the oil ran out then the spindle will expand, friction will build up ??? and it will bind right so the correct preload would be so its not tight at running speed scratch.gif would that be its not loose when the spindle is cold but doesn't get tight at running speed?

 

[GWRdriver]

Tapered bearings are not the be all and end all to accuracy and good finishes as people seem to think

I have heard and read many times hat the old hands always preferred plain (ie, bronze, babbit, etc) bearings to ball or roller bearings, especially in surface grinders, because ball and roller bearing machines always imparted a harmonic pattern to the work and well adjusted plain bearings did not. Personally I can't see the difference, but then I didn't run a grinder for 40 years.

 

[Blogwitch]

I have never seen or worked on a tapered Babbit bearing, so I couldn't comment on it.

Some of the more complex machines with plain bearings actually have thrust bearings at each end, so in that situation, you would tweak up until there was no play.

Lack of lubrication on a plain bearing head is certain death for it, and that is why they usually have some sort of reservoir on there, even if it is a small oil cup, as it was on my Atlas, so lack of lubrication shouldn't ever happen.

For adjusting a plain bearing, it is normally adjusted up until just a very slight drag is felt when the head is cold. It then uses spindle expansion and lubrication to keep things at the correct running gaps.

I used to love the plain bearing head on my Atlas because the finishes I used to obtain were like mirrors, without even trying. I can't seem to replicate that since I have changed over to a head with bearings in. That is called progress.

When I changed over the Atlas from a plain to tapered bearing head, I measured the spindle on the old head, and where the bearings sat, there was a 0.002" reduction in diameter, not much wear for over 60 years use, and it was only a soft, non hardened spindle. So lubrication and plain bearings do work, if looked after.



Blogs

 

[GWRdriver]

Then you have the German and Swiss watchmaker's and jeweler's lathes which were typically steel in steel spindle bearings. I have a Boley WW model with steel in steel spindle and information and instruction on how to keep the bearings lubricated and adjusted has been hard to come by, unless you read German. I just keep mine well lubricated and hope for the best.

 

[Powder keg]

I ran a G & L Horizontal boring mill made in 1905 for about ten years. It has a big tapered bronze bushing for the spindle nose. I could bore a hole within a half thou. with not too much trouble on that old mill. When I adjusted the spindle on it It would need about .002 up and down movement. I think when it was running it was supported in oil. I over halled quite a bit of things in that old mill. New feed nuts, gears, brazed up a couple of breaks. And there were no roller bearings at all used in building it. It was all bronze bushings.

It was amazing what you could do with that old mill considering how old it was.

 

[Noitoen]

I've seen an industrial/production cnc lathe that uses a special type of ball bearing with a bore of about 120mm that runs up to 6000 rpm with no lubrication. I asked the technician why and he said that the lubrication would compromise the precision. The bearings have 2 rows of small (about 5 mm diameter) spheres almost touching each other and are made of some kind of metal. I've seen ceramic ball bearings without lubrication but metal to metal, never. ???

 

[New_Guy]

thanks to all of you guys for taking the time in discussing this i hope im not the only one benefiting from all your knowledge

i have been doing some more research on the Babbitt bearings and what machines use them particularly the "tapered" type. the first i remembered was the Matra....

under here is a link to a rebuild where you can see the bearings. it so happens that this Matre lathe had a problem of seizing while running at 500rpm and while rebuilding it they found that the oil pipes that lubricated the front bearings had been cut and so the lathe seized from lack of lubrication. im still not sure what type of bearing it uses but i bet its tapered to the sleeve it sits in with the bore that the spindle sits in being parallel, this i think would have been a great idea in that normal wear could be taken up by pulling the bearing tighter into the tapper (also why it has slits in it like a collet) and secured with the lock nuts..... or i could be very wrong

the link to the rebuild
http://sites.google.com/site/dannympwillems/latherestorationpart5.

and the Matra lathe on Tony's site
http://www.lathes.co.uk/matra/

another lathe that uses tapper bearings is the Cromwell smallpeice lathe. Tony has it listed on his site and says "it ran in continuously adjustable, precision plain-bearings of the taper-split type, with internal cones at either end that engaged with cones on the adjusting nuts; this method of construction ensuring that the bearings were held firmly outwards against the taper bore of their housings" he also has pictures inside the headstock and a diagram of the spindle but not taken apart. ill bet that the Matra's bearings work in a similar way. here is a link
http://www.lathes.co.uk/cromwell/index.html

also worth a look on Tony's site is his page on the Wade headstock, it uses different roller and ball bearings take a look
http://www.lathes.co.uk/wade/page15.html

while looking i came across heaps of stuff on the plain/split Babbitt bearings like those used on the Southbend and Sheldon lathes. these bearings look very simple but think it would be far easier for the manufacturer to use off the shelf TRB's rather than machine and precisely scrape expensive bronze bearings maybe thats a factor in why they are no longer used in lathes ???

ill try latter to find some information on the glass hard metal on metal bearings like those used in watch makers lathes as i have heard they can run at very high speeds

 

[Deanofid]

ill try latter to find some information on the glass hard metal on metal bearings like those used in watch makers lathes as i have heard they can run at very high speeds

My Webster Whitcomb watchmakers lathe has cone bearings. They are made of hardened steel, and the steel spindle runs right on them. They take very little oil.

Dean

 

[New_Guy]

My Webster Whitcomb watchmakers lathe has cone bearings. They are made of hardened steel, and the steel spindle runs right on them. They take very little oil.

Dean

i think there is still a company in the UK who makes precise watchmakers lathes and tiny mills that run metal on metal but im still trying to to find them again

today i came across a very interesting thread on PM talking about high precision spindle bearings for lathes here is a link
http://www.practicalmachinist.com/vb/showthread.php/lathe-spindle-bearings-and-163580.html?t=163580

its a very good read i tell you