Sieg SC8 and its spindle mount

OK. I think I finally figured out what was bothering me about this lathe.
It must have went into my sub-conscious when I was looking at the owners manual.

The left side spindle bearing is a ball bearing rather than a roller bearing like the right side bearing. To make things worse, the left side bearing registers against a circlip, instead of a machined in boss. The bearings themselves seem to be inside of grease shields with no provision for oiling. I imagine it is still possible to pump some grease past the seals though. Since the cost of machining a deep groove and using a machined circlip is higher than the cost of a second roller bearing, I seriously doubt that Sieg has engineered this set-up properly. I suspect it is just a stamped circlip (50% chance it is in backwards), and a cheap roller bearing designed for minimal linear load.

I can't help but think that Sieg is just making a larger mini-lathe, rather than a smaller tool-room lathe.

/sigh.
This means the choices for 10x30ish lathes are PM (you can get on a list and maybe get a lathe in 4 months), Bolton (cringe), Shop Fox (double cringe), Wholesale Tool (900lb lathe! may as well get a real lathe), or some clapped out Southbend that is 2x what it is worth.
I think I will go with the Bolton and pay a lot more than for the PM, but at least they answer the phone and can send me a lathe this week - one in the hand is better than two in the bush. The Bolton seems to be the exact same lathe as the PM with out the VS and other goodies.

Gah, just got a text from my ex-wife. She sent me a picture of the field from her seat at the OSU/Oregon game. :banghead:
Going to go vomit.

Thank you all again
 
I'm not sure what the deal is? That bearing is almost entirely there just to prop up that end of the spindle and keep things straight, the one next to the chuck is what bears all the cutting load. As long as the right hand side bearing is preloaded properly, it's a non-issue what the left one is. You could make it out of a piece of sintered bronze and it would work just as well, only it'd be a pain to keep oiled.

As for greasing the bearings, if they come as cartridges and are sealed, then they don't need periodic greasing. The grease is supposed to last the life of the bearing.

I can think of many other reasons not to buy a lathe, but what type of left hand bearing it has isn't one of them. Hell, my old lathe doesn't even have bearings in the conventional sense, they're just 2 tapered holes in the headstock casting. Still works fine though, within and sometimes beyond the limits of the machine.
 
I'm not sure what the deal is? That bearing is almost entirely there just to prop up that end of the spindle and keep things straight, the one next to the chuck is what bears all the cutting load. As long as the right hand side bearing is preloaded properly, it's a non-issue what the left one is. You could make it out of a piece of sintered bronze and it would work just as well, only it'd be a pain to keep oiled.

As for greasing the bearings, if they come as cartridges and are sealed, then they don't need periodic greasing. The grease is supposed to last the life of the bearing.

I can think of many other reasons not to buy a lathe, but what type of left hand bearing it has isn't one of them. Hell, my old lathe doesn't even have bearings in the conventional sense, they're just 2 tapered holes in the headstock casting. Still works fine though, within and sometimes beyond the limits of the machine.

Sadly, this is not really true. The rear bearing is under a lot more thrust than you give it credit for. Not only does it have to hold the preload for the front bearing, it gets pounded a bit each time the tool takes pressure off the work. This would never be an issue on a mini-lathe where the work is only a few ounces and the tool pressure is always very light. I do agree that it would be fine if proper preload on the front bearing could be maintained, but it can't. Not only will the rear ball bearing be over loaded, a stamped circlip is not meant for this type of application and will lose preload (not to mention the circlip can pop out of the groove if installed backward).

Just to be sure, I googled up the part numbers since they use standard item numbers for the bearings. Both bearings are just plain old fork lift bearings, and the circlip is just a plain old stamped part for a square shoulder. My very ancient Walker-Turner lathe uses a similar set up (it uses a machined circlip on the outer race of the bearing rather than in the soft cast iron), and I have ruined more than one work piece over the years when the bearing lost its pre-load. I am pretty sure this is caused by thermal cycling since a roller bearing can not be loaded sufficiently,

As for sintered bronze, it is only in very recent years that bearings have replaced bronze in precision machines, and they are still used in watchmakers and jewelers lathes. They run extremely smooth, are as close to being immune to vibration as a bearing can get, nearly immune to grit if properly designed, and last indefinitely if kept oiled. There is a good reason for why stuff that turns 100,000+ rpm use bronze (or air) bearings. I would not trust a Chinese factory to make or install this type of bearing though.

Now here is the funny part. I have almost talked myself into buying this lathe now. Class 5 bearings are reasonably cheap and it does not look difficult to replace the bearings and use a machined circlip.
For $2,000 this really is a lot of machine. It turns a bit too fast at 100rpm (still better than most other machines), but the feed rate is pretty decent for a small machine at .0016. I like the threading options. It is a bit light at 386lbs, but that can be fixed with some judicious use of concrete and that old slab of granite in my backyard.

Thanks for arguing with me. It got me thinking about a solution rather than focusing on the problem.
-Josh
 
Josh with regard to minimum speed, remember this Lathe is derived from the C8 which changes speeds with pulleys which means there is ample room in the headstock to change the pulley on the motor with one with multiple steps. This way you can reduce the speed further. Downside is speed controller reports speed from the motor not spindle so it will not reflect true spindle speed but that is not a big issue.

Sent from my GT-I9505 using Tapatalk
 
Well, I went ahead and ordered this lathe.

I still have some misgivings about it, but I have a lot more about the other lathes in this size.
My biggest concern is about support, LMS and DroPros are just pointing their fingers at each other saying "the other guys sell this stuff."

The lathe will ship this Monday. I will try to carefully document the unpacking and cleaning, take pictures, and measurements of various things, then do a full review.

I would love to know if I can squeeze a BXA size QCTP onto it for instance. I know the AXA fits, but it would be nice to get the extra mass and larger size tooling on the machine. My gut tells me that a BXA will fit, but I would still be limited to 1/2" tooling.

Look for the review in 2 - 3 weeks. I expect it will be very long so will take a while to write.

-Josh
 
I have an axa on mine. If feels right in that the toolpost almost covers the end of the carriage (ie it's footprint is about the same size as the original 4 way post). I am not sure how much bigger a bxa will be.

It's it a problem that you are limited to 1/2 tooling? On this size lathe you really don't need to go much bigger as you probably are not going to be doing such heavy cuts anyway. For hss going bigger just means more cost and more time at the grinder sharpening the tool.

On my SC8 I am pretty much using 10mm tools and getting good results.

Sent from my SM-P605 using Tapatalk
 
BXA is most likely too large for this size lathe. To be sure you'll need to check compound slide to spindle center line height. You'll need at least 1-1/8"+ height for BXA using 5/8" tools. I was going to purchase a PM1127VF & BXA was too large for it.

BXA is generally better suited for 12x-14x lathes. AXA generally covers 9x-12x lathes. Using a BXA without the ability to use 5/8" shank tools really has no benefit over a AXA. You'll just be paying more for the tool post & holders. I have a BXA on my 12x, while most of my tools are 5/8" I also use 1/2" & 3/8" tools which are more than adequate for an 11x lathe. My 12x using 5/8" tools sit at the bottom of the tool post so I doubt a BXA is good for the SC8.
 
I will try to measure compound to centre line height tonight if you want.

New versions come with a threaded home in the compound and not the bose as described in the minilathe.com review.

Sent from my GT-I9505 using Tapatalk
 
Thanks for the replies.
I had planned on using 1/2" or even smaller tooling. I was just hoping for some more mass, and the ability to use taller cut-off blades and longer boring bars. I know I will be parting some 2" steel and boring some holes ~ 2 1/2" deep in cast iron and bronze.

I will just go with the AXA then, it will be good for 99% of anything I will do. I can make up a dedicated post that replaces the compound if it turns out to be a problem.

Winter has closed in here, I'm hoping for one of our random Ohio temp swings to melt everything. My driveway is ~150' feet long and is rough before it is covered in snow/ice. DroPros told me they will drop it in the street, and will not take the truck onto my property. I have a crane modeled after an engine hoist that uses 12" tires for moving boulders around my yard. I haven't used in it several years, hopefully it still works.

-Josh
 
Ok measured and carriage to center height is 1"


Sent from my GT-I9505 using Tapatalk
 
Back
Top