Lathe Speed

[Jim Frye]

None of my books touch on this subject, and I'm newish to turning. What is a suggested maximum rpm for a 12" diameter workpiece?

[twistsol]

I can't answer your question directly, but my Shopsmith speed chart shows a max speed of 850 rpm for anything over 6". They conveniently stick the chart directly to the headstock above the speed control. I think the slow range should be slower for larger items, but 700 RPM is as low as it goes without a speed changer or upgrading to the DVR motor for $2500

[Jim Frye]

Thanks. My lathe has electronic speed control ranging from 500 to 2500 rpm. I'm hoping 500 rpm will be slow enough for a glued up blank.

[LCHIEN]

RPM max = 9000/Dia in inches. (rule of thumb)

Tangential speed = RPM x Pi x Dia (Physics)

Tangential speed (inches per minute) (max) = 9000 x Pi "

Tangential speed max (inches per second) = 150 x Pi ~= 500 inches per second.

[Jim Frye]

Thanks. The calculation seems to be fairly common now that I took time to Google the quetion. Nice to have confirmation.

[leehljp]

I got this from someone on this forum several years ago.

50

I needed it because we had a few new pen turners who had been long time bowl turners and they kept insisting that we never needed to turn more than 700-750 rpm. it was hard convincing some of them that 2500 rpm on a 3/4" diameter was slower cutting speed than 700 rpm on a 12- 14 inch bowl.