The Shop > Tools

Mini Lathe Roller Bearings.

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bogstandard:
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

Stilldrillin:
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

NickG:
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

Stilldrillin:
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

bogstandard:
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

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