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Setting compound to a precise angle?

C

calgaryguy

Chris
I did some boring in some 1" bar (I think it was 1018) on my SM 9" Utilathe this weekend.

Center drilled, and then 4 drill bit steps from 3/16" to 1/2". I was aiming for a finished bore size of about .5250.

1) Set my compound to 90 so that the compound slide would be perpendicular to the chuck face (or so I thought, more on this later)
2) Mounted up my 3/8 boring bar in a toolholder
3) squared my QCTP to the chuck with a 1-2-3 block (which I've checked with a mic for dimensions)
4) and did some boring.

I quickly found out that my boring bar was not aligned to the bore - I was cutting as expected (.005 to .010 per pass)near the opening of the bore, but as I advanced the compound into the bore the tool would stop cutting/making contact after about 1.500" . Did a bunch of head scratching and tried a couple more test pieces, same result. Slept on it, and figured the place to start would be at the compound. On checking the compound this am I found that I was set to about 94-95deg and not 90 as I had thought I had set. The indicator marks on my cross slide for lining up to the degrees indicated on my compound are very worn and faint, plus my former SAIT machine has some readability damage on some parts of the compound degree dial due to what I assume was 'student love'.

So, my question is:

How can I accurately set my compound for a particular angle? Ie: what methods other than eyeballing the degree wheel on the compound to the reference marks on the cross slide?
 
Indicator on the toolpost reading off a reference of some kind would be my first suggestion for setting it to 90.

To make backplates I’ve used an indicator mounted to the toolpost to get the compound to the same angle as the taper on the spindle nose.

Maybe I’m missing something here but in this situation why are you using the compound and not the carriage to feed?
 
OK cool. Good to know.

My original question still stands however: What are the method(s?) for precisely setting a compound angle? Lets say I want to cut a new point on a dead center, or set my compound to '29.5deg' for threading?
 
Like Rauce said, indicator on the toolpost, indicating off a sine bar, or precision angle block

The 29.5 doesn't need to be super precise. It just needs to be less than 30
 
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