Making a Poor-Man's Taper Attachment
Tooling for my Taig lathe
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To make my taper attachment, I first built a pair of bars that could clamp to the lathe bed. I used 1/2" square aluminum bars, with clamp shoes made from 3/4" extruded aluminum channel that was a snug fit on the bars. The shoe that rides on the rear of the lathe bed is fixed permanently to the bar by a press-fit pin and a screw. That clamp is held parallel to the bar by a 1/8" spacer.
The front clamp is free to pivot on its mounting pin, but it has a captive nut (a swage nut) driven into it that mates with a cap screw through a hole in the bar. To mount the clamp bar on the lathe bed, the rear shoe is engaged, then the front shoe it pivoted into position before the mounting screw is inserted and tightened.
After the bars were completed, I mounted both of them on the lathe and scribed
a reference line on the bar tops parallel to the lathe bed.
To cut a taper, I clamp the two mounting bars to the lathe bed as far apart as I can and then use C-clamps to clamp the ruler from my combination square to the bars. To set the angle, I measure the distance between the bars and then multiply this by the tangent of the desired angle. One end of the ruler is set on my scribed reference line. The other end is offset from the scribed line by the tangent times the distance between the bars.
I made a follower for the carriage out of two pieces of hot-rolled steel bar. The bottom piece fits in the T-slot, while the top piece clamps down over it. At the far end, a 1/4" steel pin through both bars rides against the ruler. To set up for turning a taper, I do the following:
The photo shows the 15°taper I was cutting, immediately after the final cutting pass. I'm cutting fairly hard steel, so I'm using a brazed carbide cutter. All of the swarf from the final pass is balanced on the cutter in this photo — it's a mixture of cutting oil and very fine gritty bits of steel because I made the final pass very slowly in order to get a nice finish to mate with the lathe spindle taper.
This setup has worked very well. So far, the primary use I've had for it is to turn 15° tapers on tooling that fits the lathe's spindle taper, but I've used it three times: