Lathe headstock bearings.

[Retired]

Hi,

During the last 60 years I've changed many types of bearings but I thought it might be worthwhile adding a few details of how easy it actually is to change headstock bearings. I'll try to put this thread together as I go along because otherwise I could get bogged down adding all the images. I like other mechanical engineers change machine bearings without having to give the job much thought.

Cleanliness; patience and gentleness are needed; dirt of any kind and bearings are enemies; it's no good dashing in just trying to pull everything apart because a mistake could prove costly; gentleness is needed because using excessive force could render the lathe as scrap; cast iron can be fractured/broken.

The first lathe is a very easy one it being a Record Power DML24" I've owned this wonderful small lathe for over 30 years and a few years ago it was not running as smoothly as it used to run so no problem just replace the headstock bearings so here it is possibly not in the correct order otherwise I'll be here all day;

I've always liked this DML it being a special present from my lovely wife all those years ago when we had little spare money; it was bought new from Tabwell tools in Bakewell as a Christmas present to me costing £199.00 having no sooner got it home Record slashed the price to £99.00 which really did infuriate me but this aside it's still a lovely lathe.

The headstock mandrel is removed towards the tailstock; I screwed in a set screw ensuring it was well home as seen top; the bottom is just the motor plate. See lower because the mandrel isn't ready yet to be removed. When everything is ready a hammer is used to tap the mandrel free by hitting the head of the set screw; this will eject the mandrel and main bearing but leave the outboard bearing still within the headstock.

The mandrel fully removed without causing damage.

Here's the mandrel but please note the small machined flat top right; this is very very important indeed because it's the section where the pulleys are installed and a grub screw bears down tightly on this flat; to attempt to drift the mandrel out without first removing the grub screw could break the casting so please be warned.

The main bearing fitted from the factory; NTN is a decent make of bearing; there are many bearing manufacturers making this size; I tend to use SKF bearings finding these reliable and reasonably priced but for a novice don't think bearings are very expensive when in fact it might surprise you; on eBay an SKF double metal shielded 6204 can be had for as little as £3.50 including postage the outboard bearing will be even cheaper so a pair of bearings could only cost around £7. For this lathe rubber or metal shielded bearings could be used.

Gently withdrawing the outboard bearing using a spacer the spacer needs to have an inner diameter larger than the outer diameter of the bearing this allows the bearing to be pulled into the spacer. Whilst removing any bearing if it locks up never ever apply undue force but find out the reason.

The three step Poly V pulley; as I said earlier regarding the small machined flat on the mandrel here's the reason for it; the grub screw which must be removed; screw it well out so that it no longer binds; on many lathes there could be two grub screws and these into indents but on the DML it's straightforward enough; if in doubt completely remove the grub screw but do not lose it. A set of Allen keys will be needed but a set doesn't cost much; I used to buy sets from Poundland. It's worth noting for a novice the set screw unscrews anti clockwise. be careful to reinstall the pulleys the correct way round.

The clean bearing housing; bearing housing must be very clean indeed and bearings too kept away from dirt.

The drive belt and guess a very common mistake that can be made; yes to fully assemble the lathe with new bearings thining what a good job I've made of this only to find the drive belt hasn't been installed; if new bearings are being installed then also install a new drive belt these don't cost much and are available from many places even eBay.

The new SKF bearings only costing around £7; the large bearing is the main bearing the small bearing the outboard bearing but it does depend on the type of headstock being worked upon; these are classed as double metal shielded.

More yet to follow so please bear with me.

Kind regards, Colin.

 

[Retired]

Hi,

Continuation from above.

I always have odds and ends kicking around I can press into service; here I'm using a short length of steel pipe the inner diameter of the pipe locating the inner race of the bearing; never do this by applying any force to the outer race of the bearing; at work special heating ovens warmed bearings allowing them to simply drop into place then as they cooled they gripped the motor shaft but I've never bothered heating bearings always using this method to gently drift them home I stress without undue force and taking care the bearing is going home straight otherwise it will lock solid giving no end of grief; patience is wonderful.

Upon assembly with the pulley loosely in position there are a couple of ways to locate the grub screw on the flat on the mandrel; I simply draw a line as seen and then align against the line but with more experience using the correct Allen key screw in the grub screw until it just touches the mandrel; do not nip the grub screw down but apply very gentle pressure whilst rotating the mandrel within the pulley; suddenly the grub screw will become slack indicating the correct position; just rock the mandrel to find where the grub screw goes in most and tightly nip the grub screw. It takes a lot longer to describe in text than to actually do the job.

Here the small outboard bearing is being drawn home using a long set screw. this time though pressure needs to be on the outer bearing race; installing bearings needs pressure on the inner bearing race when on shafts or mandrels but into a machined bore pressure needs to be on the outer race. I might be over cautious but I've never had problems with bearings I've installed.

Here I'm installing the mandrel with it's main bearing; long threaded rods are cheaply available from places like Screwfix; I have pulley drawers as seen so use these but even timber battens could be used in similar manner.

I take it for granted replacing bearings but for a novice it can be very daunting not only understanding which way a mandrel comes out; how to do it; how to remove and replace the bearings and where to buy the new bearings and drive belt; if in any doubt at all I suggest taking along both original bearings and drive belt to a local bearing supplier; go in workshop clothes looking reasonably scruffy and drop the items on the counter saying do you have these in stock please; if the bearings are an unusual size they'll need to be ordered in but usually can be collected the next day; these days I just buy online the bearings are numbered as are drive belts.

I hope this is of use and this DML is about as simple as it gets; I hope to add two more different lathe headstocks but enough for now.

Kind regards, Colin.

 

[Democritus]

Great stuff, Colin. But what about us poor souls who don’t have a DML?
D.

 

[marcros]

is there such a problem as fake branded bearings?

 

[Jelly]

is there such a problem as fake branded bearings?

Yes.

I believe SKF were the first to have a major issue with it, but multiple manufacturers have been burned by it.

The story I heard was that engineers looking into quality issues with a failed train wheelset which nearly caused a derailment sent some lot numbers to the manufacturer to see the QA documents, the manufacturer responded that those weren't real lot numbers, cue much confusion.

They eventually took the physical bearings and found that both the materials and machining were well out of spec, but the external visual appearance and manufacturers markings very close to perfectly matched a proper one.

That raised alarm bells, and their customer traced the issue through the supply chain to bearings which were imported from a wholesaler in the Far East because they were cheaper.

That wholesaler had provenance which claimed they were ordered by a company from SKF and then sold to them at discount as an over-stocked item, but the lot numbers were all identical (and nonsense) and no paper trail existed to show them having ever been exported from Germany (to subsequently get passed around and re-imported).



Obviously for cheap nasty sealed bearings in consumer applications then for most purposes it makes no difference.

But when you start talking about big bearings in critical situations (like train wheels, or mining equipment) the cost per unit can be astronomical most of which is the cost of QA to ensure it will work like it should for as long as it should...

If some disreputable individual doesn't bother doing any of that expensive and bothersome QA but sells them under the guise of a trusted brand for close to full price, they can thus net a very tidy profit.

 

[Retired]

Hi,

is there such a problem as fake branded bearings?

Good question; I selected the DML just to show how easy it is to replace headstock bearings in a basic lathe however the principle applies to all lathes some though are a lot more complicated.

This is the headstock assembly from a Union Jubilee lathe I fully restored; it's got a spacer included; once again be aware there are usually some kind of locking here the outer spacer and pulleys have grub screws; a lot of care is needed to check all locking devices are loosened or better still completely removed.

Here is the Union Graduate mandrel with bearings and one of the collars (spacers). This mandrel has both a machined flat and also two indents for grub screws.

The Graduate stripped ready for a comprehensive rebuild.

The two collars from the Graduate; note they are both different so any work where parts are removed needs careful notes/images otherwise it's so easy to lose the plot if relying on memory alone. Seen on the left is another grub screw hole.

New main bearing being pulled home taking a lot of time and care to ensure it's aligned and not binding. I use anything to hand for this kind of job; a length of square and a shorter length of steel tubing plus even a pulley all used with a long threaded rod; I don't recommend using a drift and hammer; this method takes a lot longer but it pays long term.

The outer bearing being pulled home onto the collar; it's very easy indeed to damage components by being rough; a simple dent on a bearing landing throws up a ridge that can cause a lot of grief.

The Graduate being made ready for paint.

Here's a much more complicate lathe mandrel it running on plain tapers; this is out of my extremely rare Lorch Schmidt precision engineering lathe; unlike caged bearings these taper bearings are a lot more difficult to adjust; standard caged bearings as long as they are located correctly can be ignored but any tapered bearing has to be very finely adjusted some taper bearings also need pre loading. Adjustment on the lorch mandrel is afforded by locking ring nuts and there is also a thrust bearing which also needs fine adjustment; I don't recommend a novice playing around with this type of mandrel until experience is gained on simpler mandrels. I have detailed pictures somewhere but adding these threads takes a lot of time.

Years ago I restored a very old Myford engineering lathe it having a broken headstock casting at the main bearing but this is way out of general DIY capabilities

Sorry about picture quality but here are the new bearing caps I made for the Myford; the top one is completed the bottom just has the bearing land machined; I'm an old fashioned engineer taught the old fashioned ways so used hack saw and files to bring the caps down to correct shape; the metal is Meehanite cast iron; I hand cut the headstock to accept these; I can file to a thou of an inch but it took a lot of time and effort; I don't have a milling machine or shaper but can still do precision work like this.

Definitely not a job for a novice to take on; I made new plain bearings out of Whale Tufnol and the mandrel was so bad I had it metal sprayed with stainless steel then brought to original specification. The bearing caps were nipped down tightly having shim adjustment. I've restored many machines over the years and it always gives me such personal satisfaction to put an old cast iron machine back to as new usually costing little money wise.

It's surprising what can be achieved with a bit of TLC on these old machines.

Kind regards, Colin.

 

[Jelly]

I made new plain bearings out of Whale Tufnol

What kind of speed is that running at, and how have you found they've held up?

I've got a plain bearing to replace in a mill headstock (the assembly uses a close fitting cylindrical plain bearing to reduce run-out, backed up by two taper roller bearings to support the axial load), and was considering using either Oil-ite sintered bronze or babbit metal, and had assumed Tufnol wouldn't hold up as a rotary bearing material, having only seen it used for refacing slideways.

 

[Retired]

Hi,

Thanks for asking Jelly. After repair I just used the lathe as I normally would; at first the new bearings warmed up a bit but soon settled in and worked fine. The Tufnol is very easy to turn to accurate tolerances but I didn't like the dust especially whilst sanding it ending up with a massive headache so had to resort to wearing a dust mask then I coped OK. Whale Tufnol is the grade for bearings;

Tufnol bearings | PTFE | cotton fabric grades | Carp Brand | Bear brand | thermoplastics | Bearing grades | Plastic machining components

I'm unable to offer guidance as to Tufnol applications other than what I've used Tufnol for and it worked for me; a guy on another forum did state he had a huge farm trailer and Tufnol bearings were used in the axle showing no wear even after heavy use; a plain bearing will accept an higher load than a rolling element bearing. It's possible my Tufnol bearings ran warm at first because I might have been a bit too keen on a tight tolerance.

These are the new bearing caps I made from scratch.

The new Tufnol bearings being turned. I do recommend a dust mask because the Tufnol dust did upset me. Here I'm using a boring bar in the lathe; I didn't have the slightest problem in getting better than half a thou tolerance.

New Tufnol bearings completed and ready for final assembly after a paint job. I had the mandrel metal sprayed by Metallizers who asked me to supply the bearings; they were highly impressed by the close tolerances I'd achieved with this Tufnol it being new to them.

The split bearing with oil hole in cap.

If in doubt you could possibly contact Tufnol directly for advice on your own application giving full details; I'd also ask what tolerances they recommend.

Tufnol, Engineering plastics and composites | Plastic machining | Fabrics laminates | Machining components

Kind regards, Colin.

 

[clogs]

for solid bearings with high loading or not have also look at :-
[email protected]...they are a S.African firm but now have a place in the UK.....
their application chart is something to behold......really modern stuff that works well.....
Blanks are available to machine ur'self......

I beleive the VB 36 has solid cast iron bearings but o so special....similar design to gas turbines......

I have a job in the planning that needs a bearing like the headstock type above......
but I will use a bearing from the rear axle from a car /small truck......
these are a double row, deep groove bearing that are locked by a nut....
this nut when torqued up supplies just enough preload pressure between the bearing to take up the slack....
using this style of bearing takes away the need for a seperate double bearing and very cheap/easy available......
My thought's are that if you can drive a car/truck at 70mph or more with a 1 ton load plus the weight of the vehicle for at least 100,000 miles it will be good enough for my application....

thanks for the above Colin,
I'm sure there are a lot of worried people on here that want to change their bearings.....
you have said it, just take your time in doing this job it's not a race....lay the items out as you take em off.....
so all you have to do for reassembly is to go in reverse...
and get your new bearings from a dedicated supplier and dont be afraid to ask for genuine bearings.....
the offerings on eBay are not always the best.....esp on a jobs like the above.....
I've seen the cheapo bearings, the sealed variety put together without any lube......!!!!!

All the best for this New Year.....
thanks for a great forum.....

 

[Retired]

Hi,

Thanks clogs; a happy New Year to you too; 2021 looks like it's going to be a good un.

I buy bearings both from local bearing suppliers and eBay; as you say there could be poor bearings for sale but I've never experienced any problems; on eBay I buy from bearing suppliers who have a good track record so they have much to lose if they supply faulty goods; if I was in industry I'd want Timken bearings but for my use I find decent grade good enough but never buy the budget grades. I generally use SKF bearings.

Bearings - Suppliers of Ball Bearings, Roller Bearings, Bearing King Ltd

Simply Bearings Ltd ~ Oil Seals SKF *** TIMKEN KOYO NTN NKE TRULOC Needle Rollers Taper Rollers Rod Ends Oil Filled Bushes Loose Balls O Rings Grease Plain Thrust

I wanted to keep details as simple as possible hence I chose the DML which just about anyone who can use a spanner wouldn't have problems with in replacing headstock bearings but I'm very familiar with lots of other styles of bearings; there's a bearing for just about any application and these days easily available on the web; I'm a dinosaur and remember days we didn't even have electricity in our cottage and only gas lighting with a single coal fire for heating I come from a coal mining family.

Kind regards, Colin.