Setting up a long bar for between centres turning

Just a couple of ideas, I've got a slightly bigger lathe . - make a center drill holder from a morse-taper blank ( or old drill) to suit the tailstock. Drill a hole same size as the drill and stick the drill in the tailstock holder with super glue. This will give more room . I would fabricate the headstock first then mount on the cross-slide for boring, assuming there is room. Drill and tap the cross-slide .

As Brian Wood suggested a few posts below mine, if at all possible then do finish bore them in the complete headstock assembly - this would be very much better for alignment. My suggestion was intended as a bodge to work around your machinery... If it will fit, perhaps the most promising route would be a between centres boring bar on the lathe, as suggested by mechman48 and Gordon W above. If it won't fit, and you can't bore in the mill either, you may have to try the solution you describe above unless you farm it out.

A few other thoughts:

• What sort of bearings were you going to use? For metalworking lathes you'd probably favour angular contact ball bearings, so that you can preload them against each other to take out all play, with a nut on the spindle. These are the fussy ones for alignment but provide a rigid spindle which resists both end and side loads. 'Normal' deep groove ball bearings are a lot cheaper, a (very little) less fussy but aren't really designed to cope with large end loads or preload. 62x30 size deep groove bearings might well be big enough to cope fine with woodworking type end loads - I don't really know.
• How will you locate the bearings axially? One set at least needs to be fixed so that the spindle can't move along its length. Were you going to leave a shoulder at the end of one of the finished bores, add a bolt-on plate to hold them in, or e.g. add a groove for a circlip?
• You mention you're making up the headstock from four plates (front back and sides presumably). If you add a lid and base (two more plates) it'll make the whole thing immensely more rigid.
• I think you said the plates are 20mm thick steel. Just machining the edges to clean them up might be a bit 'epic' on a CMD 10: one of these presumably? I've not used one but it looks a very light machine for that sort of job. Maybe take a test run before you commit to the design?
• Bearing in mind this is a wood lathe, I can't help thinking that a design using pillow block bearings would make life an awful lot easier. They're not ideal in some ways (not specifically designed to cope with end thrust, nor of immense precision) but if you were planning on using 'normal' deep groove ball bearings anyway they'll be no worse (that's what they are, basically, in a self-aligning housing), and woodworking loads might well be within the capacity of say 35mm ID pillow block bearings (go as big as you can, given your 40mm spindle stock). And they self-align... so just need bolting to something solid. Plus they are remarkably cheap e.g. here.

Hello Iain,

Just trying to hold 12 inches of material upright and then begin boring a hole down from above with a lightweight mill really is asking for trouble. The tooling alone in the boring head will only reach maybe 2 inches at most and the instablity of the whole set up is against you right from the start.

I do have other equipment to tackle some of this project for you, leaving you with the things you can manage.

I would also strongly advise against using your spindle and bearings as an assembly guide for the headstock box, you might not notice a slight misalignment as you bolt up but the bearings will and side loading of that sort will lead to rapid failure even if it turns at all when built.

Send me a PM for my address, email etc and we can take that further if you wish.

Include your email while you are doing so.

Brian

Hmm.

Much food for thought. It turns out there is space for the centre drill so that is one less worry.

Although the initial intent is a wood lathe, I'm quite keen to see if I can get something which will tackle metal too - that needs a bed and stuff which is beyond my ability to think about at the moment!

The diagram isn't complete. There are a couple of bolt on plates which will act as stops.

I've had some reasonable success with milling a nastier bigger piece of steel on the mill, though I broke it in the process! I learned a lot from that.

As mentioned earlier I'm doing this as a learning exercise and if I end taking it to bits and rebuilding it with Pillow bearings or need 2 or 3 goes to get the spindle right, I'm cool.

So I do plan on stretching myself and kit in the sure knowledge that I will cock some things up well and truly!

All your advice is much appreciated, though and improves my chances of getting something working no end!

Iain

Iain, a thread on the spindle nose, and the MT could / should be left until the headstock is finished and attached to the lathe bed.

Be looking through some of my old books, I have 3 from the 1920s / 30s "The Amateur Mechanic & Work" Hand Book, "The simple Lathe and it's Accessories", "Small Lathes, Making and Using", and "Metal Turning Made Easy". In the second book there is enough info, drawings etc to build a 2.5" back geared lathe, including how to make the patterns for the bed. About the only thing I'd change would be to enlarge the spindle diameter from 1/2" to 1", and use angular contact bearings, I think the original spindle run in the cast iron of the headstock casting, this would be fabricated as you are planning to do. This was the only way a lot of the early Model Engineers could get a lathe, and much good work was done on them.

Ian S C