*Small taper pin turning*
I need to turn a few replacement taper pins, 1 in 20 taper by about
3mm (thick end) and 20mm long. Easy enough to turn with the compound slide set over. The problem is I haven't a clue how to set the angle accurately enough
- I just cannot set it to two decimal places of accuracy! I haven't got a sine bar (and doubt if I would know how to use it anyway!) Thought I could turn a larger diameter piece (having calculated the small and large diameters at a fixed length) but can forsee problems accuratley measuring the 'small' end becouse of the taper.
Don't know if I'm missing the obvious - anyone got any pointers please? Its only a one-off job so don't really want to have to spend too much time. I only want a couple & assume I'd have to buy a 100 or something readmade ones?
A method that I saw used many years ago to copy a taper was as follows:-
1) Ensure that the tailstock and lathe chucks are truly in alignment
2) Chuck a piece of bar a bit larger than the taper pin and longer than the jaws of the tailstock chuck. Turn the outside true
3) With a sharp drill a fraction larger than the small end of the taper pin make a shallow depression in the end of the bar ? the idea is to produce a bowl for the pin to locate in
4) Part off the machined length of bar
5) With a sharp drill a fraction larger than the large end of the taper pin make a shallow depression in the material left in the chuck
6) Hold the first piece you made in the tailstock chuck
7) Grip the taper pin between the tailstock and lathe chucks
8) Mount a dti in the toolpost at centre height
9) Adjust the topslide angle so that the dti registers zero along the lenth of the pin
10) Turn your taper pin
This method does need one good taper pin to work from and a dti that does not apply too much pressure to the pin as it is only resting in shallow locations.