>I'm trying to build a large bowl lathe utilizing a piece of hardware I found. Spindle diameter at present is 2".
I have a machinist friend who will put threads and a shoulder on it for me but I cant decide what size spindle and threads I should go with.
My jet mini uses 1"8tpi and I would be able to use my talon on it, however I'm not sure that would be strong enough. I thought that I would eventually want to get a stronghold or similar chuck to use on it, and I want to maximize strength, without having to go with a custom adapter.
>I would make it at least 1 1/4 in. and bite the bullet and buy an adapter down to a 1 x 8 if you needed to. If you thread it 1x8, you will not be able to beef it back up. It will always be only as strong as the weakest link...that being 1 x 8.
>I built my lathe and spindel. I threaded it 1 1/2 8 TPI because I allready had some chucks and faceplates. 1 1/4 will be better because of the limited selection of chucks for 1 1/2 8.
>well I agree up to a certain point with the previous message but I have a spindle 1-8, and had no trouble turning any size yet in 20+years your main trouble is the bearings (get the best you can even if they are expensive they will pay in the long run check my page and see for your self
>Probably 1 1/4/"x 8. After 1" x 8, 1 1/4 x 8 is probably the most popular spindle size out there. A bit beefier than 1 x8, but still easy to find faceplates, chucks and other threaded acessories.
>You have a spindle and bearings that are capable of swinging a 6' to 8' diameter piece of wood. Why do you want to limit its use by using the same threads as a lathe that swings 12" to 24". You could make the thread on the spindle the largest possible, a 1-1/2" X8, and then make or buy an adapter to drop down to a smaller thread for the chuck and accessories. That way you would always have the capacity for the larger diameter if you ever wanted to use it.
>John, a lot of responses, but only one approach really makes sense. I built a big lathe in my early years, and had a 2-7/16" shaft made. I used 1-1/4"-8TPI because I thought it would be the best alternative. I soon after bought a Vicmarc VL300 short bed, because the big lathe just didn't perform as well for my chosen focus, that of hollow vessels and bowls. This lathe I ordered with the same thread so I could quickly swap from one to the other. This makes a lot of sense in a production shop, and actually in any shop. I still have two lathes which have 1"-8TPI threads, so I also have adaptors for the two thread sizes, and use them as needed. I also have five chucks, so it makes changing around a little easier, I suppose.
It takes a special customer to buy a bowl in excess of 24" in diameter, in my experience. They really need a BIG family to use such a bowl. Otherwise it becomes a piece of furniture.
I use the big lathe for wall hangings, and long, large spindle work, and to rough out large pieces. It will take a cowboy hat blank and turn it quick, and resist the walking around that even the Vic will experience with a large, out of balance blank. Of course, it weighs in at somewhere around a ton and a half or so.
Getting back to your question, I'd make the thread as large as possible, and buy adaptors for the chucks and get faceplates to fit. That way you haven't limited yourself to a smaller spindle, and you can take advantage of the additional strength. This may give you added confidence in your equipment, but seriously, I haven't had the slightest doubt about the capability of the inch and a quarter I used, and have obviously had no indication of any untoward stress on a spindle.
Now that I've talked my way around the subject, you can read between the lines enough to find that if I was going to do it again, I'd go bigger, but I feel I went big enough, too, so use your best judgement. One inch is too small, though, I fear. Best of luck, and keep us informed of your progress. Email me with any questions.
>One thought is to make them whatever size the threads are on say the Super Nova without an insert. Then you can always buy and adapter if one is needed.
>This option I think appeals to me the best, 1.5"8tpi, leaves enough shoulder for registration and I'll have 2 faceplates made at the same time. An adapter will come later when the funds for the chuck and such become available.
Thanks to all who answered me, I really appreciate the input.
Should a really large bowl come down the pike, I'll be sure and snap a few pics of it spinning.
