[Jason3]

You're a champ! I like your retaining ring plan better than the others too now - the picture was what I had envisaged from your description but somehow seeing it made it clear. That should work well. It also helped me come up with a way to retain the bearings from the inside while still using the same size bearings at both ends of the spindle, so I can use the bearings I have, QDB and DB as we talked about. I will do a drawing and get you to take a look.

I went and found my bearing specs ok, but I couldn't find how much to derate it by as a quad set - the specified speed for (I assume) 1 bearing was 16,000 rpm with grease... I think you're right - I should be ok at 3000 rpm. I'd like a bit more headroom, but don't actually know what I'll need, so I'll shoot for perhaps a bit higher and watch the temp. I was intending to use a T5 belt and aluminium pulleys - would that be an option for you, to get your revs a bit higher (if you need higher, that is...)?

About the Inpro seals - thank you, I hadn't really considered that I could use bigger than the bearing size. Doh. Should be no trouble to get some affordably!

Glad to hear your ballscrew spec - that's similar to what I wanted to use. I have been playing with a crazy idea to use a big 40 mm dia x 12 mm pitch C3 ground NSK I bought by mistake and use it to add rigidity to a big single rail setup. No doubt I'll get laughed off the site for that

Best regards,

Jason

I forgot to ask - what would you say is a reasonable wall thickness for the spindle wall? I could keep it around 9 - 10 mm easily enough now, and still get a 40 mm + bore...

[mackeym]

9-10mm spindle wall thickness should be fine. If you have any kind of FEA program (or know some equations), you could model the stresses and deflection.

For superprecision medium preload NSK bearings, speed deratings are as follows: DB 0.65, QDB 0.60

About T5 timing belts and pulleys, if you know of any that will fit onto a ~95mm shaft, I would consider them. I don't know that any standard ones size exist.

For inpro seals, a little larger than needed is fine for grease lubrication. If oil is used, then you have to make sure the oil level is low enough so it doesn't leak.

[Jason3]

I don't have any FEA software, but I will see if I can find something online. I had a look at my manual lathe - the spindle wall on it looks to be about 5 mm thick at the back to 10 mm thick at the chuck end, with a 38 mm bore. Since it's a decent size lathe I think it confirms I'm on the right track at least.

Thank you for the bearing information, that is good news - .60 for the QDB setup still leaves me with a lot of headroom over my intended max RPM with grease. Good point about the oil/inpro seal - another good reason to stick with grease!

I had intended to use aluminium T5 or T10 pulley stock from www.sdp-si.com - that way I can make my pulleys any width I like. I checked and they do have stock up to 158 mm OD in the T5 size, and up to 227 mm in T10. The larger sizes do get quite expensive, I don't know how it compares to the PolyChain GT2 pulleys you had lined up, but I saw that 112 mm OD stock is just under $80 per 160 mm length, which I thought wasn't too bad. I have a local supplier for the belts, they'll supply any width/length I specify overnight...

[tootalew]

For the life of me, I cannot find the following information. I too am using a surface plate for a lathe base. I am drilling for the inserts with a 5/8" core bit. This leaves the holes about .635" in diameter. What diameter should my inserts be? Maybe a better way to ask it is, how much space do I want between the granite and insert? I thought I read somewhere .050" but now when I need it, I cannot find it. Assuming at this point that .050 is the number, would I make the insert .100" smaller than the hole?

[mackeym]

Yeah, this was discussed a little in this thread and the clearance 0.05" was brought up. The only "official" clearances i've found are on the redhead epoxy website. For their epoxy they recommend 1/16" oversize hole for inserts with diameters ranging from 1/4" to 1/2". (0.031" clearance). Coincidentally, this is what i've also used and I think it's a good amount of clearance.

[Cartierusm]

Interesting build. Do you have a link to your website, the one in this thread is dead. Thanks.