calculation for a sine bar

[old martParticipant @oldmart]

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.

[SillyOldDufferModerator @sillyoldduffer]

Posted by JasonB on 11/06/2020 13:11:59:

Posted by SillyOldDuffer on 11/06/2020 10:55:05:

Not found a definitive 'R8' yet! It's not in my copy of Machinery's Handbook (20th Edn), which led me to assume R8 was just ANSI Standard Steep Machine Taper, 3½" to the foot, or 16.2602°. Not so!

It's in the one I have as 16deg 51'

First item under "collets"

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

[Gary WoodingParticipant @garywooding25363]

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.

[old martParticipant @oldmart]

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

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