Sieg SC6 headstock bearing replacement

[pat_pending]

Hi,

I just finished replacing the headstock bearings on my Sieg SC6 lathe and I thought I'd share how I did it incase it helps anyone else out there. Sieg lathes are the classic 'Chinese mini-lathe' so may well sell under different names / colours worldwide (Grizzly I think in the US?). Anyway, if your lathe is made of Chinesium and looks like my lathe its probably the same machine and these instructions will be relevant.

First of all, I wish I had replaced the bearings a long time ago or when I got the machine. Putting in some premium brand bearings and grease has transformed the machine beyond recognition in terms of noise and vibration reduction. The sign that the old bearings 'had had it' however was that the machine started getting noisier, the casing much warmer and in the very end, turning the chuck by hand felt like the shaft was hexagonal i.e. it would be really lumpy to turn.

Replacement parts:

• Timken 32007X Metric Taper Roller Bearing 35x62x18mm
• SKF 60072RS1 Rubber Sealed Deep Groove Ball Bearing 35x62x14mm
• 1 x Z32 Major Brand Z-Section V-Belt
• 1 x SKF 60012Z Metal Shielded Deep Groove Ball Bearing 12x28x8mm
• Mobil Mobilux EP2 NLGI 2 Grease

The chaps at Arceurotrade, as per usual, were really helpful. It's great to have a company that cares about post-sales support when, I bought the machine 10 years + ago, they haven't sold that model for 3 years. Class.

The exploded parts diagram for most Sieg machines are available on their website here:

https://www.arceurotrade.co.uk/Catalogue/Machine-Spares/SC6-Lathe-Spares
So here's how I went about it.

Part 1 - Disassembly


Loosen off the belt tensioner and remove the belt.

Use two C spanners to remove the spindle locknuts.

Remove the pully, spacers, gears, key etc from the shaft and remove the idler gear beneath,

Using 3 M16 bolts and some shims to protect the late paintwork, gently tighten up to remove the spindle from the bearings.

Using a bit of scrap mild steel bar and metal round, tap out the rear bearing with a hammer.

Using a bit of tube that sits on the edge of the bearing inner, tap it out with a hammer.

Gile everything a really good scrub to remove old grease and any contaminants.

Give everything a good wash in some soapy water after the degreaser and dry well with compressed air/paper towels.

Give the bearing seats and surrounding areas a really good clean too.

 

[pat_pending]

Part 2 - Reassembly

Use a bearing separator to pull the front taper bearing outer off the shaft. I tried this with a rotary tool on the idler gear and trust me, one of these tools is worth the £25 outlay. I'm sure it will be used again for some obscure job at some point.

Take apart the idler gear by removing the circlip and pressing everything out with an arbor press.

Homemade puller from scrap bits used to seat the front bearing inner. Don't worry about pulling against the rollers, they are meant to withstand a lot of pressure so using them to pull the bearing into place is not an issue.

New inner race nicely seated.

Reverse the puller and do the same for the rear bearing. Try and get something that pulls on the outer and not the inner race/cage as if you're unlucky you'll destroy the bearing if you don't do this. In this case, there wasn't that much force required to sear the bearing here anyway so it would have been fine.

Back bearing now seated.

Use a pice of mild steel tubing that fits exactly against the bearing inner and bash the bearings into place. Since the tube material is softer than the bearing material and the fact its pressing on the inner you cant't damage anything here so don't be afraid to give it a good whack if it needs it! Alternatively a floor press or arbor press with enough clearance can be used here too.

 

[pat_pending]

Part 3 - reassembly continued

Pack the bearings full of grease.

Use the puller again but this time with the bar you used to tap in the bearing inner. DON'T FORGET TO PUT ALL THE OIL SEALS ON THE SHAFT OR YOU'LL HAVE TO DISASSEMBLE EVERYTHING ALL OVER AGAIN!!!. Tighten up till everything is nicely seated.

At this point, reassemble the back-end with the idler gear, spacers, key etc and tighten up the lock nuts with the c-spanner.

Part 4 - post-reassembly adjustments and checks

Bearing preload - I ran the spindle at a fair speed for 10 minutes or so while I was tidying up the workshop to let everything warm up. After this i stopped the machine and tightened the inner locknut so the backplate would spin for 1/4 turn or so when i gave it a flick. This ended up being about as tight as I could get the locknut by holding the backplate with greasy hands before they slipped (scientific). I'll probably have another look after everything has settled down.

Checking for runout. I used a dial gauge in the spindle taper as shown to check the runout. I was reading 0.007mm. Unfortunately I didn't do this on my new machine when I bought it 10 years ago so can't compare but from what I've read, this is probably as good as I can expect from a budget machine. I'm happy.

Checking tailstock alignment - After all the bashing ad fiddling, I thought it would be prudent to check/adjust the tailstock set-over. I did this by chucking up the longest piece of free-cutting steel I had and turning both ends between centres.

Any difference in reading I would adjust the tailstock setover by half the distance using a dial gauge. In the end I managed to get this to 0.003mm over about 50cm. V acceptable I think.

Conclusion

I am chuffed to bits with the result. The lathe is so quiet now and happily spins up to 2200RPM without things starting to fall off the shelves etc. Really great and wish I'd done the job much sooner. If your lathe is a bit noisy and getting noisier/warm, I totally recommend doing this bearing overhaul.

Hope some of this is helpful..

Thanks,

Patrick

 

[ajoeiam]

Part 3 - reassembly continued
snip

I am chuffed to bits with the result. The lathe is so quiet now and happily spins up to 2200RPM without things starting to fall off the shelves etc. Really great and wish I'd done the job much sooner. If your lathe is a bit noisy and getting noisier/warm, I totally recommend doing this bearing overhaul.

Hope some of this is helpful..

Thanks,

Patrick

I like your style mate!!!!!!!

 

[Farsider]

Thanks pat_pending,
I’ve just replaced the bearings on my c6.
Even though I have a c6 (and not a Sc6) your instructions and descriptions were spot on and made the job easier.

Definitely quietens the lathe.

Damaged bearing below.

 

[pat_pending]

Thanks pat_pending,
I’ve just replaced the bearings on my c6.
Even though I have a c6 (and not a Sc6) your instructions and descriptions were spot on and made the job easier.

Definitely quietens the lathe.

Damaged bearing below.
View attachment 131248

Hi Farsider. Glad it helped and thanks for letting me know.

Patrick

 

[azalin]

Hi,

Thanks. I just installed my new SKF taper bearings. They work really quiet and smooth. The difference is huge. I'm not sure if I overtightened the shaft just a bit. I can still rotate the spindle easily but not that free as it was with the old bearings.