Thread: Two colar test piece

With most of today taken up with home schooling I am lacking a bit of motivation to do anything in the shed but still wanted to achieve "something".

So I snuck out between breakfast and school starting and knocked together a 2 colar test piece.

For a while I've noticed my lathe has been cutting an unacceptable taper but mostly got way with ignoring it.

So this morning I leveled it using a Starret 98 to rough it in and then use a more sensitive (0.02mm/m) level to get it closer.

The test piece is made from the shaft of a treadmill roller, approx. 35mm diameter and slightly harder than ms, maybe 1045 or something

I cut that down to approx. 300mm long.

I then took a piece of 45mm aluminium and bored it to a press fit on the shaft and parted it in two pieces.

Put the shaft in the freezer and the al on the stove.

Slide both al rings on and about 250mm apart.

I then took a piece HSS and sharpened and hone a cutting edge.

I checked the test bar in the 3 jaw and turned the al rings down until they were both concentric. I set the compound to approx 6 degrees (from parallel) and proceeded to take very light cuts (approx 0.01mm DOC)

and measure the diameter of both discs.

First test cut revealed a difference of 0.016mm in 250, larger at the TS. Not as bad as I thought but still room for improvement!

I stuffed around with leveling feet adjustment and after about an hour I got it to within 0.005mm in 250.

I'm calling that plenty good enough for me.

That two colar test bar is something very simple that I should have done years ago.

If I centre drill each end then I can also use it between centres to align the TS.

Very happy with that.

Cheers,

Simon








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Good job Simon. Glad to hear your Lathe is more accurate now.