Setting lathe top slide angle accurately.

Thanks everyone for your help. I have decided to make some "wedges" for the commonly used angles (like 29 1/2 deg) that don't need extreme precision & use Joe Piezinski's method for more accurate jobs. His method doesn't need a long travel DTI & I have a DRO on the cross slide. He also has a good video on milling angles on wedges. A good result all round, thanks again.

Geoff, do you have a sine bar ? If so when making your wedges it will pay to make lots of common angles. Keep them small and then they can be used in the vice on the mill for setting workpieces. I have most angles from 1/4 degree up to 45 degree. Made up over the years I find them very useful.

A brief caution regarding printing a drawing: Check that the printer actually produces the same scale in both directions. Most are near, but not all are bang on. And do not rely on paper or card being really stable in moist or dry conditions. They can shrink or stretch more one way than the other.

Not really a problem unless you are after accuracy - but sometimes, we all are.

Seasonable Yuletide wossnames

Tim

I don't use the any method consistently.

If I have a sample taper to match I mount the sample in the lathe and sweep the taper with a dial test indicator. O adjust the angle of the top slide until the indicator reads the same at both ends of the taper.

If I have no sample to go by I use a sine bar. I have a 2.5" sine bar that can be locked in position. Once set with gauge blocks I can remove the blocks and take the sine bar to the lathe. One leg of the sine bar is magnetic so I can stick it to the tailstock spindle or to the face if the chuck.

If I am cutting long tapers by setting over the tailstock I check diameters at both ends of the work and adjust the tailstock accordingly.

If I am setting the top slide for threading I use the graduations on the cross slide. I set the angle about 1/2 deg. less than half the flank angle of the thread.

What Tim said. I fell foul of this when scanning some drawings from tracing paper, printing them and then offering them up under the original trace to discover they were the same width but shrunk top to bottom (on portrait mode with A4).

Whilst we are on this theme lets touch on the difficulty of measuring a tapered part. I usually calculate a couple of steps and produce known distance in from the end and diameter to suit using a sharp tool. It is then simple to just blend to the witness.

When using a machined face on the side of the topslide,just check that the face is parallel to the top slide vee slides before setting up any angles.