Sieg SC4 Headstock bearing replacement

I wonder if anyone here has experience of replacing the headstock bearing/s in the SC4 lathe. Mine has had little use and very low runout when I bouught it, but it has become gruesome. I have not been able to find a dimensioned engineering drawing of this lathe. Before I start dismantelling it and measuring for replacement bearing/s, perhaps someone here could give me some advice. A ling to a proper drawing of the lathe would be expecially helpful.

Gareth.

This manual includes bearing designation in the parts list - that should allow you to purchase direct replacements, or even alternative style for same envelope. **LINK**

Not sure of this machine but could it possibly have taper bearings that just need adjusting ?

I find it strange that it has had little use but runout has become gruesome.

How are you checkiing the runout ?

I would check the chuck and its monting / locating register before pulling it to bits

For Chinese machines i usually check on the Grizzly machinery website as they seem to have the best manuals , you just have to look for a machine that looks the same as yours and download the manual .

Ian.

Edited By XD 351 on 04/08/2016 20:02:09

Gareth,

I think you will find that a fully dimensioned engineering drawing is intellectual property and will not be kicking about.

David has sent you a good link above to get started.

However as regards noise it may not be all bearings. This machine was originally designed to be sold with a rear mounted milling spindle and the traverse feed was arranged so the bed could be used as a power feed under the milling cutter without the chuck rotating.

If you study the input drive the belt connects to a countershaft under the spindle. Power is then taken from a pair of 1.75 mod gears of 32 teeth each, from countershaft to spindle.

These run in the open, inside the head with a dab of grease on them and this could be part of your noise.

Personally if I owned one of these I'd look to putting the drive direct onto the end of the spindle and only use the feed as and when needed to cut the noise down.

The Arc Eurotrade website in the section titled "Articles" has a good article on changing the bearings on a Seig lathe. If you have it apart it would be worth converting from the standard ball bearings to the far superior tapered rollers, which IIRC is covered in the article. Ketan at Arc seems to be the fount of all wisdom on these machines. He does post on here at times so perhaps may have more to offer you.

Going by David's link it has 32007 taper bearings, first thing to do would be as XD said and check they are adjusted correctly

The early C4 had a taper roller at the front and a deep grooved ball at the rear 32007 and 6202, but from Axminsters manual it looks like the SC4 has a taper at the rear now, 32007 and 30206.

It would pay to see if the double nuts at the rear of the spindle require adjusting.

Thank you to all who have helped me with this runout problem. To asnwer XD351's question, I measured the runout using a plunge-type dial indicator mouted on a Noga arm with the indicator tip touching the flange to which the chucks are attached. Currently, runnout is about 0.27mm.

I have a ground parallel bar with an MT3 taper and I'll try measuring that next, but I'm not hopeful. I strip-down is in order, is guess.

-- Gareth

Gareth,

Put a long bar in a chuck and see if there is any movement in a DTI on the chuck body when you pull the bar back and forth. If yes, you just need to apply more load to the bearings using the adjusters at the back of the headstock.

Neil

Re the "horrible" runout of my Sieg SC4 lathe. It seems my methodology may have been the problem all along . As I mentioned earlier, I measured the runout by using a plunge-type dial indicator on the flange on which chucks are mounted. When I removed the chuck and measured a precision ground test bar terminated with an MT3 taper, and later directly within the mouth of the MT3 opening in the headstock, using a no-name lever-type dial indicator showing 0.01mm per division, I could get no discernible reading at all. With a bejewelled Swiss Baty lever-type indicator reading 0.002mm (2um) per division there was a discernible flicker of the needle of less than one division, so I can confidently say that the runout is probably <0.002mm.

Glad to hear a happy ending, Gareth.

N.B. this is not ChineseLathe-knocking, but ... To meet the cost/benefit demands of the market, I suppose it is inevitable that the run-out of the chuck mounting flange might be considered relatively unimportant.

If the taper is running true, the rest can be easitly improved as-and-when you feel the need.

MichaelG.

Gareth from your first post it sounds like the lathe didn't have the run out it now has at some point but does now ???

There is a slight possibility that you pressed the front bearing home when you put the test bar in. Neil's waggle about test would be a good idea.

One sign of very loose bearings is the lathe recuting more than would be expected from the bar bending when winding the tool back to the start. Say 2 3/4" of 1" dia ms bar is a decent test for that with a cut depth of a mm or more with no centre in. To give the lathe a fair chance it's best to run it at a high speed for 10mins or more before trying it. Sometimes the recuting is only really noticeable at the very end of the bar and if slight can just be that the bearings have worn slightly oval. The degree of cut is usually significantly more if the bearings are loose. Facing the end of the bar can also be messy usually improved with the right shape of tool by facing centre out as the cut will be deeper which help keep things in place when their is play.

I just measured the length of bar I had sticking out of a mini lathe chuck when I tested it. It passed but i suspect that it might benefit from a truly tiny degree of tightening so I will leave them alone.

Don't what ever you do try and true up the chuck flange unless you are 1000% sure everything else is ok.

John

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Edited By Ajohnw on 23/08/2016 13:34:01