how to find cutting diameter of boring tool

[autobot]

if youre using a conventional single cutting edge boring tool, how do you determine the cutting diameter before making a cut? Or do you drill a hole, go low by eyeballing the radius setup, then bore, then measure, then adjust, bore again then measure etc?

[keebler303]

I bore, measure, adjust.

You can get pretty close by putting a gauge block or something in the vise and touching off one side, rotate the bar 180 degrees and touch off the other side. The difference in the two readings will be the diameter of the bore plus the gauge block. I don't trust that to be accurate though so I just bore it to where I know its undersize and then measure and adjust.

Matt

[RICHARD ZASTROW]

I'd do like Matt said. If you can measure the location of the tool bit tip, it won't compensate for cutting pressure/deflection. I like to "sneak up" on the finish dimension.

Dick Z

[DareBee]

Cut and measure.
Good to be a sneaky Dick too.

[UUU]

Cut and measure. Although it can be tough to accurately measure a small hole.

For a really close fit, make a stepped rod first with diameters leading up to your required dimension, then try it between cuts.

[JWH]

Something to consider if you are doing more than one part. If you creep up on your final diameter with light cuts on the first part and then your second part takes a heavier cut removing all the material in one pass your bore diameter may not be the same size as the first part. I always check the dimeter of the second part before removing it from the vise or fixture in case the boring tool needs adjusted.

Jim

[fizzissist]

If you absolutely positively MUST know where you are with your boring bar....
(who doesn't take a cut, measure, take a final cut anyway????)

Use your edge finder and locate an edge of something. Put your boring head with the boring bar into the spindle, and position the centerline of the spindle away from the edge equal to the radius of the desired hole. Adjust the boring head so that the tool's edge is safely away from the edge (towards the centerline) and bring the head down so the tool's edge is below the top surface of the something's edge.

Slowly rotate the tool back and forth while slowly dialing the tool outward until the cutting edge barely scrapes (this is where you're favorite flavor of Dykem is useful, or a piece of paper) the surface of the something. When it does, the tool is adjusted to give you the desired diameter.

One little caveat....... It's adjusted correctly, but that doesn't necessarily mean it'll CUT that exact diameter. Just means it will in theory.

[fizzissist]

Another very novel approach, if you're boring a critical must-not-scrap-it part..... test bore a dummy part first.

Say..... why didn't I think of that!?!