Author Topic: Mini Lathe Roller Bearings.  (Read 21089 times)

Offline Stilldrillin

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Mini Lathe Roller Bearings.
« on: June 04, 2009, 04:29:13 AM »
I decided it was time I fitted taper roller bearings to my Mini Lathe......

I had read several stories of needing another lathe to machine spacers, but gained confidence reading the later part of David, Twinsquirrel`s posting.  :clap:

http://madmodder.net/index.php?topic=899.15

NO Problem!

No special tools needed....... Anyone who has changed a car wheel bearing need have no worries!  :thumbup:




.....BUT!

Why does the bearing spacer/ tumbler gear/ locknut assembly wiggle like a swashplate???  :bugeye:




I had noticed this occasionally, over the years. But it was bought new, so must be ok (& out of sight under the cover)......

The spacer bore has 2mm clearance on the spindle.

The 2 locknuts are threaded very wobbly to their faces!!!!

What`s all that about?  :bang:

And now what to do?  ::)

Turn up a new larger dia spacer, a sliding fit onto the spindle.





This correctly aligned the tumbler gear, for the first time in it`s life.

But not the nuts.......





Soooo....... I screwed a piece of bronze to a tight fit in the nut`s threads.




This allowed me to face up square with the thread.

Had to remove approx .035" per side from touch on, to leaving a witness.....




Super job...... Now!  :thumbup:



Still rather puzzled over the apparent April Fool bodge........

WHAT was all that about?  :scratch: :scratch:

More to follow, when I`ve taken some more pics.......

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Darren

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Re: Mini Lathe Roller Bearings.
« Reply #1 on: June 04, 2009, 04:45:54 AM »
Some nice work as usual again there Stew  :thumbup:

Now I'll have to take another look at my nuts  :jaw:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline sbwhart

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Re: Mini Lathe Roller Bearings.
« Reply #2 on: June 04, 2009, 04:53:34 AM »
Some nice work as usual again there Stew  :thumbup:

Now I'll have to take another look at my nuts  :jaw:

Stew  :scratch:  I'm Stew this thread was started by David  :doh:   :lol: :lol: :lol:

David

Nice work getting thing correct I recon what was wrong was a bit of good old Chinese quility control, I've found odd bits of things wrong similar to what you've found they probibly didn't clean the chuck out when then threaded those nuts so a bit of shonet threw the work out of kilter.

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Darren

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Re: Mini Lathe Roller Bearings.
« Reply #3 on: June 04, 2009, 05:05:44 AM »
 :doh:

Done it again, sorry chaps, keep mixing you two up.... :lol:

Still a good job done though David  :thumbup:

 :ddb: :ddb: :ddb:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline Stilldrillin

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Re: Mini Lathe Roller Bearings.
« Reply #4 on: June 04, 2009, 05:30:38 AM »
A`m confussted agin.......  ::)



DAVID D     :D
« Last Edit: June 04, 2009, 05:32:40 AM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

bogstandard

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Re: Mini Lathe Roller Bearings.
« Reply #5 on: June 04, 2009, 07:05:04 AM »
Darren,

I'm glad you are the one checking your nuts, I'm sure I wouldn't like to do it. The ones on the lathe are a different matter all together.  :lol:

Dave,

If the lathe works as well or better than when you first started, it is a good fix.

Looks like a gud 'un.

John

Offline Stilldrillin

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Re: Mini Lathe Roller Bearings.
« Reply #6 on: June 04, 2009, 08:17:41 AM »
The following day, (yesterday), I had a visitor bearing gifts.......

Dave, Bluechip dropped these off........

The usefull remains of a smashed Warco mini lathe.




It was a great pleasure to meet him. What a nice guy!  :thumbup:

In among the spares were 2 locknuts & a spacer!




The original nuts were screwed a very loose fit on the spindle thread, these fit and spun perfectly true.

So, as Dave`s nuts are bigger & better than mine, I fitted `em.......




Time to get back to making swarf again.......  :D

David D

« Last Edit: June 04, 2009, 01:05:47 PM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline NickG

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Re: Mini Lathe Roller Bearings.
« Reply #7 on: June 04, 2009, 09:52:20 AM »
Nice job David,

Will be interesting to see if you notice a difference. I know some people say it makes a huge difference and I've seen a video somewhere of somebody parting off after the mod, looked like a hot knife through butter.

What are all your other goodies for?

Nick
Location: County Durham (North East England)

Offline Stilldrillin

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Re: Mini Lathe Roller Bearings.
« Reply #8 on: June 04, 2009, 12:35:26 PM »
Nick,
I`ve not done much with the mod, as yet.

Spent some time getting as little bearing drag as possible allied with no chuck movement.

The rythmic squark has now gone!  :ddb:

The rear bearing must have been really tortured, with it`s inner race held only at one point of the tilted spacer.  :borg:

I have given it some (comparative) welly, using a 45dgr tool into a piece of 7/8" steel bed iron......

It performed just like I remember grown up lathes working....... No squealing, no chatter, just got on with it!  :thumbup:


The other goodies are all mini lathe parts. For spares, as & when.  :clap:

As Dave remarked, I`ll never break my headstock gears, `cos I`ve got a spare set now!  :D

David D
« Last Edit: June 04, 2009, 12:37:34 PM by Stilldrillin »
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

bogstandard

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Re: Mini Lathe Roller Bearings.
« Reply #9 on: June 04, 2009, 01:56:27 PM »
The main difference between roller and taper bearings is the loading they can take.

Taper bearings will run a lot truer when subjected to side loads. Also, if run correctly, they will be more accurate when doing facing cuts, as the end float is negligible.

The taper bearings require the correct preloading. If you haven't got that information, or can't find it, then a general rule of an engineer's thumb is, tighten the nut up tight finger tight, then put approx another 1/16th of a turn on using a spanner. You should 'feel' friction when you turn the chuck by hand. Some tapered bearings are set up using a spring balance on an arm of a fixed length sticking up from the side of the chuck, and the nut is adjusted until you get a certain 'pull off' pressure.

The main difference is that after the taper bearings are preloaded, the lathe should always be allowed to run a few minutes on the first startup of the day, or if used intermittently, before each machining session during the day. This allows the spindle to 'warm up' and reach operating length (the spindle 'grows' by about 0.002" or 0.05mm). This then takes a little of the preloading off the bearings and they will run much smoother and more accurately.
There is one slight disadvantage with taper headstock bearings. If you are not going to use the lathe for a month or more, you should always release the preload off the bearings, because if you don't, the bearings will become 'brinelled', this is where the balls are forced onto the races in a stationary place and become pocketted, coupled with very rough running. If that happens, the bearings will require replacing. Or you can just make sure you run the spindle up for a couple of minutes each week.
Also, be aware, that you should never fill a tapered head bearing completely with grease, use only a maximum of 50% full. This prevents hydraulic(k)ing, spell how you like, so causing damage to the bearing at high speeds.

I bought a second hand tapered bearing head for my Atlas from the US. I don't know how long it had stood in the salvage yard, but I could feel the indentations on the races with my fingernail, all because it had not had the preload released. Luckily I managed to get the races reground, as a new pair of bearings needed a second mortgage.

This is information that you needed to know, because the layman thinks it is just a matter of fitting tapered races and that is the end of the matter. Far from it, they need slightly different operating and maintenance methods than ball raced heads.

I just hope it helps.

John

Offline Bluechip

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Re: Mini Lathe Roller Bearings.
« Reply #10 on: June 04, 2009, 05:41:11 PM »
Bigger and better nuts Dave SD ?? Size isn't everything, so I've been told. Wiggly nuts can be very alluring to some. Being a batchelor I wouldn't presume to comment on a subject of which I have no experience.  ::)

Whether 'tis Nobler in the mind
To donate one's once cherished but now redundant nuts,
Or cast them unto a sea of Landfill
And by thus disposing, end them ??

Yup! Too much Glen Morangie   ... AGAIN !

Off to kip, while I still have a vague idea of how to work my landing gear ...

Dave


I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline Stilldrillin

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Re: Mini Lathe Roller Bearings.
« Reply #11 on: June 05, 2009, 02:20:12 AM »
John,
Some really usefull information there, thank you!  :thumbup:

I have had problems on locking the locknuts together, so varying the bearing`s pressure.

I eventually locked them together as a stiff assembly, then adjusted until the clearance disappeared, but no drag.
I think I`ll just tweak them very slightly tighter now.

I had noticed the sound changed after some 15 seconds free running, warming up I guess......


Dave,

I couldn`t possibly comment.......  :lol:


Thank you, again.......  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline CrewCab

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Re: Mini Lathe Roller Bearings.
« Reply #12 on: June 05, 2009, 05:09:29 PM »

It performed just like I remember grown up lathes working.......


I love that quote  :clap:

CC