Thread: Lathe questions

I bought a big old Asian lathe (actually my 50th birthday gift from my wife, but I did the choosing and getting) that had some of the gear train missing, most significantly the 127-tooth gear that enables metric thread cutting on an imperial machine. It's been impossible to find the right gears, and I got a quote of around $1300 from a gear-cutting mob to manufacture the 4 gears to complete the set (tell 'em they're dreaming...). I plan to cut the gears myself, after some online research I've found that this can be done in the lathe with some fairly complicated setting up. I posted some questions about casting gear blanks in an online metalwork forum, and a bloke in the U.S. has very kindly undertaken to cast them for me in his backyard foundry. Just hope I don't stuff the blanks with my first attempts at cutting gears.
The common / popular models of lathes, particularly the American machines, seem to be reasonably easy to find parts for, but with the more obscure machines you're pretty much on your own. My crossfeed screw is badly worn, I've had to make a replacement myself, next step is to make the crossfeed nut to suit. Fortunately, a lathe is a great tool for making lathe parts.

Originally Posted by Blknight.aus

Id suggest if you can find a gear cutting jig thats of appropriate size that you look at your lathe as tho its a horizontal drill mill with a somewhat oversized chuck piece...

Dave, I'd be interested to know more about the 'gear cutting jig' you refer to, apart from expensive dividing heads, I've only seen shop-made setups in my web searching, and even then it's nearly all woodwork stuff for clock making.

One off gear cutting by a hobbyist is easiest done with a horizontal or universal milling machine. No need to cast blanks. Machine them from heavy plate or bar. If you don't have one or can't borrow time on a milling machine, 'phone around the TAFE colleges to find if one still has a hobby or certificate course in metal machining.

Tool height and cutting speeds are important.
For external turning make sure your tool is not too high as it may be contacting the work piece slightly below the cutting edge!
Also make sure your revs are pretty close to giving you the correct cutting speed for the diameter of your work and the type of material it is made from!
Chatter should be minimal or non existant if all those can be achieved, however a rubber band cut from a car tube and stretched over the workpiece can help. My lathe runs a bit too fast for maching 11" brake drums, so a lacky band stretched around the outside does the trick.
Good luck and as others have said, wear safety glasses and keep your fingers away from that swarf, it has no mercy!



Cheers, Mick.

Originally Posted by POD

I bought a big old Asian lathe (actually my 50th birthday gift from my wife, but I did the choosing and getting) that had some of the gear train missing, most significantly the 127-tooth gear that enables metric thread cutting on an imperial machine. It's been impossible to find the right gears, and I got a quote of around $1300 from a gear-cutting mob to manufacture the 4 gears to complete the set (tell 'em they're dreaming...). I plan to cut the gears myself, after some online research I've found that this can be done in the lathe with some fairly complicated setting up. I posted some questions about casting gear blanks in an online metalwork forum, and a bloke in the U.S. has very kindly undertaken to cast them for me in his backyard foundry. Just hope I don't stuff the blanks with my first attempts at cutting gears.
The common / popular models of lathes, particularly the American machines, seem to be reasonably easy to find parts for, but with the more obscure machines you're pretty much on your own. My crossfeed screw is badly worn, I've had to make a replacement myself, next step is to make the crossfeed nut to suit. Fortunately, a lathe is a great tool for making lathe parts.

It is not uncommon when inspecting old lathes offered for sale to find some of the change gears missing particularly the 127 tooth gear. Many shops never worked in metric particularly screw cutting. If the lathe is still in the shop go have a look in the tool store. Usual practice is for the commonly used gears to be in the chip tray or on the headstock and the seldom used ones left in the store. I have known it when liquidation auctions are scheduled and the shop is cleaned out and packed up for sale for all extraneous unidentified pieces to be thrown out or put on a pallet for sale as a mixed lot of supplies. The missing gears can sometimes be found in the scrap or in a mixed lot. Sometimes the full set of gears are hidden so one of the staff or a mate can buy the lathe cheaply. I have seen this at a TAFE College auction.

The lathe is a Nuttall, similar to the one in the pics. Interesting to read Brian's comments, I will need to look around the workshop if I am able for the missing bits.

Jeff

Originally Posted by Brian Hjelm

It is not uncommon when inspecting old lathes offered for sale to find some of the change gears missing particularly the 127 tooth gear. Many shops never worked in metric particularly screw cutting. If the lathe is still in the shop go have a look in the tool store. Usual practice is for the commonly used gears to be in the chip tray or on the headstock and the seldom used ones left in the store. I have known it when liquidation auctions are scheduled and the shop is cleaned out and packed up for sale for all extraneous unidentified pieces to be thrown out or put on a pallet for sale as a mixed lot of supplies. The missing gears can sometimes be found in the scrap or in a mixed lot. Sometimes the full set of gears are hidden so one of the staff or a mate can buy the lathe cheaply. I have seen this at a TAFE College auction.

Thanks Brian, I made extensive efforts to locate the missing gears, plus travelling steady; I made a trip from Bermagui (where we were holidaying) to Sydney to the factory that originally had the machine, after talking with the foreman who reckoned the parts might be on a pallet somewhere. Drove home empty-handed and very disappointed. I've since fabricated a travelling steady (follow rest), making the missing gears myself seemed the only option left.
It was suggested to me to use plate or bar stock to cut blanks from, but these gears are 1" thick and the 127-tooth gear is 10.75" in diameter, I wasn't able to source suitable stock.

Sorry Jeff for the semi-hijack. I've seen parts for Nuttal lathes occasionally on eBay. Hopefully the workshop has your parts out the back somewhere, I was unlucky in that the company had moved premises a few years prior, and chucked everything out in the move.

Old flywheels make useful stock .Holden red motor is about 11" and thick enough just bolt in appropriate centre They are not SG iron but as good as the old flatbed lathes used for change wheels

AM