Sieg Super C3 bearing change

[John Rudd]

I posted some time ago that I treat myself to a new minilathe...

After taking delivery and asking one or two pertinent questions it was time to strip clean and install some new bearings.

The job from start to finish has taken some three weeks, from purchasing new bearings, receiving advice and finding time and the good health needed, it is all back together and I'm rather pleased.

I've put together this as a project with photos and a bit of a commentary on what was done, I hope you like it...
So to kick off, I've cut out the boring bit like how I stripped it down to the last nut and bolt..and move right on to the rebuild...

Here's a couple of shots of the bearing outer races installed in the headstock

[John Rudd]

Next up, the spindle. The original bearings were standard ball races and as such were a press fit onto the shaft. Their removal shouldn't challenge any of us on here...
However, as I'm changing these for taper rollers a slight adjustment of the bearing journals is required to allow the inner races to 'slide' on the shaft to enable the correct amount of preload to be set. This required the spindle to be mounted between centres on the lathe and the journals polished with a fine abrasive paper until the new bearing race would be a tight slide on with a hand push fit...



After polishing the shaft it was treated to a good wash in solvent to remove all traces of grease and abrasive prior to adding the  chuck end dust cover and bearing...

[John Rudd]

Next up,  the drive end race added along with the dust cover.



....the spindle was offered up into the headstock housing and the other bearing added.



Now the fun part....

The orignal bearings were 16mm thick, the new ones are slightly thicker at approx 1.6mm.
Thsi means that the drive pulley and the spur gear are out of alignment with their respective counterparts....




There are two plastic spacers fitted as part of the spindle assembly...Obviously these need 'madmodding   to accomodate the extra thickness of the two bearings....

[John Rudd]

The spindle on the later minilathe is slightly different in make up...



There are several items that fit on the shaft and obviously need to be in the right place...


As the spacers were made of plastic, in true Madmodder spirit, new ones just had to be made from metal 



Apologies for the out of focus shot on this one..( are there any more? ) I was in a bit of a hurry.... 

[John Rudd]

After a quick rummage with 'Er indoors in the garage...( oooeeerrrrr missus mind me brass bits  )

I managed to find some aluminium bar that would do just fine....

A quick fettling in the lathe....




and we soon had two new shiny bits to add to the assembly.....

Unfortunately, the spacers had a keyway cut in them .....Hmmm...more work


Time for a bit of quick thinking on how to make a keyway...

Here's the setup I came up with..



A bit Heath Robinson but got the job done...

[John Rudd]

Sooo, after adding the new spacers, time for a trial fit of all the bits..



Apologies for this too...(I'm no good with a camera, can you tell?  )

Now the spindle drive pulley lines up nicely....

After adding the nuts and setting the preload we seem to be getting somewhere..



Even the gears for the tumbler reverse line up...



Not much left to do now...

[John Rudd]

Completion of the rebuild is basically just adding back all the bits that were taken off and giving them a clean and grease/lube in the process...

A couple of more hours work yesterday saw the machine back together in its glory...( is it a 'glory' machine?   I'm rather taken by it personally...)



I've since added new brass gibs to the crosslide/topslide and made saddle stop and added a qucik change tool post...I've yet to complete the holders for that..



A quick wipe with an oily rag and that's me done....

My thanks go to Ketan and the staff at Arc for their help on relieving of my hard earned for the latheand the gib strip kit and also the advice I received from them on the choice of grease, that was free of charge...

I'd like to thank myself for taking the time to strip and rebuild the lathe and also 'Er indoors' for enduring my never ending whinging about the cold in the garage.

[Brass_Machine]

Nice write up! 

You said you got a gib kit from Arc?

Eric

[Stilldrillin]

Nicely done and shown, John. 

It will make an L of a difference! (Love the soft focus shots)..... 



Eric. My lathe's having a brass cross slide gib, sometime this winter.     
 
Near bottom of page......   http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/Model-C3-Mini-Lathe/C3-Super-C3-Mini-Lathe-Accessories/C3-Super-C3-Upgrades

David D

[loply]

John,

I have a similar lathe myself and have extensively modified it.

I'm interested in your comments about the taper bearings requiring a sliding fit. I fitted the same to mine many moons ago and this never occurred to me, I just pressed them on using a screw press of some kind. I wonder if I should re-do this.

Whilst I'm here can I share with you what I think is a real big tip for these lathes- The cross slide screw has a 'bearing' surface which is like a plain metal disc turned in to the screw, this bears against the metal part where the dial is. The trouble with this arrangement is that the materials involved are steel on steel which has a bad amount of friction, further compounded by the tightening of cross slide gibs which pushes the two surfaces into each other with greater force. End result? Tightening the cross slide gibs produces a disproportionate increase in force required to turn the cross slide handle, which is small to begin with, meaning you will not tighten the gibs enough.

Solution is to remake the whole lot using thrust bearing to absorb the obvious thrust without increasing friction, and also give yourself a bigger handle with a rotating outer cover whilst you're at it. You will consequently be able to tighten the gibs up to the necessary amount and thus take either larger or more stable cuts.

All of the above applies to the compound too.

I also had good results from increasing the size of the pulley on the back of the headstock, off the top of my head to 67t, whilst decreasing the size of the one on the motor, to give new top speeds of 800rpm and 1600rpm in high and low gears. Makes it a lot harder to stall and allows deeper cuts.

Cheers,
Rich

[John Rudd]

John,

I'm interested in your comments about the taper bearings requiring a sliding fit. I fitted the same to mine many moons ago and this never occurred to me, I just pressed them on using a screw press of some kind. I wonder if I should re-do this.
Cheers,
Rich

Rich,

Fitting taper bearings takes me back to the time when I used to 'do' cars....

Typically Fords had taper rollers on the front...I remember overtightening one to the point that after a few miles it got all hot and bothered and broke up...I didnt realise this at the time until I arrived at my folks house..attempts at removing the inner race( even with oxy-acetylene) were futile as it had welded itself to the stub axle...a new s.a was needed to get me home( courtesy of the local breakers yard)...

Besides, if the inner race isnt allowed to float on the shaft how does one adjust the end float with a spanner?.... Oh, I know, an even bigger spanner..
I applied the same thought process when I changed the bearings on my Chester minimill, which happen to be the same ball bearing races as the minilathe.....

[WillieL]

John,

That is an outstanding job that is well documented. 

Regarding the fit of the bearings I could not agree more having 'done' cars for a living for a lot of years. The chuck end of the spindle could be a press fit (I would recommend it actually) but as you stated the 'tail end' bearing needs to be able to slide a bit in order to properly set the bearing pre-load. And the finial setting should be done after the lathe has been run awhile, and the bearings are up to normal running temperature.

Do you by chance remember the bearing numbers you used? Any problems with grease leaking out of the housing?

I've added a ball bearing to the cross slide on my little 7x10 which made things much smoother, but I really like the idea of using the tapered bearings in the headstock. I have a 4" chuck on mine which is quite hefty for it's size, and I think this mod would be a good move for me.

Thank you for sharing all the info.   

[John Rudd]

Do you by chance remember the bearing numbers you used? Any problems with grease leaking out of the housing?

The bearings are available from ArcEurotrade part number 30206...Although admittedly I didnt buy mine from there...Any reputable bearing supplier should be able to provide them, but it pays to shop around..There's a big difference in price and quality...The bearings Arc supply are quality items, as are brands like SKF or FAG.

As for grease loss, none should come out of the housing unless they have been overpacked

I added what I thought to be the appropriate amount to provide sufficient lube for the bearings then added a little more...just a little no more than that...Quantity wise I'd say around a teaspoon full  for each bearing and that's being generous...

[iafilius]

<snip>

As the spacers were made of plastic, in true Madmodder spirit, new ones just had to be made from metal 


<snip>

Hi John,
bit late to respond to this thread, but just got my Super C3.
preparing to upgrade to tapered barings myself, and having no second lathe this topic got my interest.
I've machined a nylon spacer as a first run on the lathe, which is now 27mm in diameter on the inside, and 40mm in diameter on the outside (which i could measure without disassemble the lathe) . Depth .. i hope long/deep enough, as i don't know the depth yet.
Does anyone know the exact dimensions of the old spacer? and key-depth/with? in order to prepare the spacer as a preparation on front?

But the real reason i respond to this thread, is that i think a metal spacer isn't the best idea to my opinion. I think it is better to have some more elastic spacer, which is able absorb temperature triggered variations, and acts like a spring for manual adjustments as well. Even more when it gets too hot it may act like a fuse.

So i really think some "soft" plastic is better then all metal spacers in this case. I can't particular recommend nylon for this, as the nylon was some kind of a task to machine, and to hold in the chuck.
What do you think of this thought?

Arjan Filius

[John Rudd]

Arjan,
I'll post up the dimensions of the orig spacer......

Not sure I agree with the plastic spacer you suggest and the reasoning....properly adjusted the bearings should be fine....if the temperature rises as you suggest, this would affect the bearing preload using a plastic/non-metallic spacer more than the alloy ones I used.....(plastic softening?)

I'm no metallurgists, so let's discuss.....always willing to learn and exchange views

[iafilius]

Hi John,

if you want to share the original spacer dimensions, yes please

In the meantime I'm waiting on my 4" (100mm) spindle, to have all components ready for an upgrade (bearings + spindle).
Bearings are already waiting.

About the plastic or some softer/elastic material or hard metal spacers, I'm not a metallurgist as well, and don't kno what  the barings itself can absorb or give back when needed, it seems logical to me, but the temperature size variations might be compensated by the tapered bearing, which has hollow cones and i read. Maybe you need absolute stiffness for a lathe, and therefore no soft plastic.

Thank in advance for the dimensions.

Arjan

[John Rudd]

Ohhhhhh.......

Finally got round to it....
The thickness of the spacer is 11.08mm.....That is the original spacer thickness....
Apologies for the belated reply....

[Meldonmech]

Hi John

                            Well modded, should make a big difference
                                   
                                                                                                    Cheers David

[iafilius]

Ohhhhhh.......

Finally got round to it....
The thickness of the spacer is 11.08mm.....That is the original spacer thickness....
Apologies for the belated reply....

John and others. Ut took some while for me to get the right materials (bearing puller stuff), and now with my spindle detached, thinking on the subject shielding the tapered bearing.
The dust cap will keep the worst out probably, but like a seal more.
It seems the dust cover is build to hold a seal. I ordered 48x3 , 48x3,5 and 48x4 (mm) nbr o-rings to see if i can get it sealed and fit. If that works i consider to create a new spacer with a diamer of 48 too, to be able to use the same construction. That spacer needs to be shortened or re-created anyway.
What do you think?

Regards,

Arjan

[steampunkpete]

My default choice for grease would be a moly-grease. What did you use john?

With regard to the bearings: For almost all applications that use two bearings (ball or taper) the rule is that one inner or one outer must have axial float. In the case of ball-races this is to prevent axial loading which the bearings are not intended to withstand. For taper bearings it is to permit the pre-load to be set (as has been rightly stated in this topic already). There are some odd exceptions to this rule for certain applications. When the Triumph Bonneville was made by the Meriden Cooperative, they redesigned the rear-wheel to take a disc brake. The wheel hub was re-designed with two ball races and no float anywhere. As a consequence the life of the rear-wheel bearings was less than 3000 miles. It was a pig's ear design with no easy remedy.

I have seen a mini lathe webpage dealing with a bearing change that suggests a 38mm x 4mm O-ring for an additional seal on the spindle. I have the bearings and O-rings ready to go and have acquired the purpose designed LMS extractor kit. The job will, however, have to wait until I've re-vamped the garage.

[John Rudd]

My default choice for grease would be a moly-grease. What did you use john?

I used moly grease when I did the brg change on my m/l........

[iafilius]

I have seen a mini lathe webpage dealing with a bearing change that suggests a 38mm x 4mm O-ring for an additional seal on the spindle. I have the bearings and O-rings ready to go and have acquired the purpose designed LMS extractor kit. The job will, however, have to wait until I've re-vamped the garage.

About the seal, i read that 38x4 seal page as well, i guessed there was made a typo or a different lathe. See my photo's without seals. I ordered some 48 nbr seals to try out, and will make a bigger spacer (black on photo) with diameter 48 too if seems work ok.

A general good thing to do is to remove the remarks on the spacer rings, to prevent uneven pressure on bearings (see photo).

Regards,

Arjan

[steampunkpete]

  And I thought I was ready to go! 

I now have 48mm x 4mm seals on order from ebay (where else?)

[Manxmodder]

Try Simply Bearings,I use them for bearings and seals......OZ.

Link: http://simplybearings.co.uk/shop/Products-Oil+Seals+and+Lubricants/c4747_4750/index.html

[Marco]

Sorry for digging this up, but i was having a go at this till i realized that it won´t work properly with the bearings press fitted. Long story short i already press fitted the front bearing...would it be OK to just polish the journal of the rear bearing? would i still be able to adjust them properly?