calculation for a sine bar

We were taught that "Some People Have, Curly Brown Hair, 'Til Painted Black" as a similar aide memoire.

One of the few bits of school maths that I can still recall, (DON'T ask about calculus! )

Howard

Hello Old Mart,

George Thomas, debunked the oft quoted "Tool must be exactly on center height, if cutting a taper". He showed by calculation and practice that the tool could be significantly off center before it became apparent in the taper.

See his book Model Engineering Workshop Manual, Tee Publishing.

Andrew.

It's in the one I have as 16deg 51' 

First item under "collets"

Edited By JasonB on 11/06/2020 13:13:40

I seem to recall information for all the common collet/arbor tapers are in ARC's catalogue. I have several homemade R8 arbors all turned to this information and checked to "Blue" in the Bridgeport spindle. Easier to get right on an R8 than a morse because the R8 is so much shorter.

I wonder if George Thomas ever tried to produce a standard 60 degree taper on the end of a centre with the tool height off centre. Anyone with a brain cell would be able to understand what the outcome would be.

My 20Edn Machinery's has nothing at all about Collets as far as I can see. Goes from 'Cold form tapping' to 'Coloring metals'. Maybe I've been had!

Good section on Sine-Bars though including a Table giving height straight from degrees and minutes.

Also mentions only negative tolerances are allowed when cutting tapers. Makes sense; a slightly too sharp taper will still go deep into the socket, whilst a slightly too fat taper would soon jam and do damage if forced.

Dave

It's also 16° 51' or 16.85°in my 30th edition of Machinery's Handbook, which is 3.6344" to the foot. The half angle of 8.425° would need a packing amount of 0.7326" for a 5" sine-bar.

An extract from Smart & browns instructions for their model A toolroom lathe: