# Taper setting dial for my SB9A



## burgermeister (Dec 21, 2014)

I've always had trouble cutting tapers with my SB tapering attachment.  Given the accuracy required, the scale on the tapering jig is rather useless.  Eventually I stared using a dial indicator set to a small machined flat to at least get a decent measurement of what I was setting up, which worked pretty well, but still didn't seem ideal - and I had to divide the taper/foot by 4, thus loosing some accuracy.

  So a few weeks ago I rigged up a 1/4-40 screw with a 1.25" dial.  The dial is clamped to the screw with a setscrew, so I can zero it.  There is enough space to go to a 2JT taper (0.9"/foot) for external tapers, and around 0.7/foot for internal tapers.  Not something I specifically shot for, just the way it turned out.  The main body is attached to the top portion of the tapering jig with a single #8 allen bolt.  The plate on top takes care of vertical locating, anti-rotation, and the scribe mark for reading the dial.  The contact point for the screw is exactly 6" from the pivot of the taper attachment.  The dial is graduated from 0 - 100.  So with the 40tpi thread, I just dial the taper in inches/foot on the dial, no need to divide by 2 (for the not terribly useful scale on the taper attachment) or 4 (for a dial indicator set 6" from the center pivot)..

The dial works like a charm.  I zeroed it by running the lathe carriage along the tapering jig with an indicator, and once zeroed it seems to be quite repeatable.  All tapers I've cut with it seem to come out perfect, no fiddling needed.  Resolution of the dial is about .001"/foot.

I need to figure out a better way to stamp numbers though ...


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## Andre (Dec 21, 2014)

Very nice idea! I believe OD grinders have something similar (albeit much more precise) adjustment for their tables. I will have to do something similar on my taper attachment, thanks for sharing )


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## Smithdoor (Dec 22, 2014)

Looks great 
Better than a brass hammer

Dave



burgermeister said:


> I've always had trouble cutting tapers with my SB tapering attachment.  Given the accuracy required, the scale on the tapering jig is rather useless.  Eventually I stared using a dial indicator set to a small machined flat to at least get a decent measurement of what I was setting up, which worked pretty well, but still didn't seem ideal - and I had to divide the taper/foot by 4, thus loosing some accuracy.
> 
> So a few weeks ago I rigged up a 1/4-40 screw with a 1.25" dial.  The dial is clamped to the screw with a setscrew, so I can zero it.  There is enough space to go to a 2JT taper (0.9"/foot) for external tapers, and around 0.7/foot for internal tapers.  Not something I specifically shot for, just the way it turned out.  The main body is attached to the top portion of the tapering jig with a single #8 allen bolt.  The plate on top takes care of vertical locating, anti-rotation, and the scribe mark for reading the dial.  The contact point for the screw is exactly 6" from the pivot of the taper attachment.  The dial is graduated from 0 - 100.  So with the 40tpi thread, I just dial the taper in inches/foot on the dial, no need to divide by 2 (for the not terribly useful scale on the taper attachment) or 4 (for a dial indicator set 6" from the center pivot)..
> 
> ...


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## tertiaryjim (Dec 24, 2014)

A great idea and nicely done.
I've had to spent a lot of time getting the taper correct to match spindles and dowels.
This would have been much faster.

Haven't seen a factory taper attachment on an engine lathe that has a precise scale or adjustment.
Always had to set it and make a test cut, then measure and maybe blue check when close.
If a person had a set of angle blocs, they might set one against the taper slide or gibs and indicate from the ways to get really close.
At least that could be a good start.


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