How to test for concentricity of a taper 30 toolholder

[4GSR]

Wouldn't it be a lot simpler to chuck up a piece of drill rod say 1/2" diameter, make sure it's running true. Then, take your collet holder with a 1/2" collet and clamp it on the piece of drill rod in the lathe and check runout of the arbor this way?

 

[fvdbergh]

Wouldn't it be a lot simpler to chuck up a piece of drill rod say 1/2" diameter, make sure it's running true. Then, take your collet holder with a 1/2" collet and clamp it on the piece of drill rod in the lathe and check runout of the arbor this way?

I like this idea.

While you have the collet holder clamped on the dialed-in 1/2" rod, you could set your compound to the taper angle by directly indicating the collet holder's taper. You can then check the runout at the two ends of the taper to see if the collet holder has any angular runout.

You would have to repeat this test with a different diameter ground bar, and a different ER40 collet, because it could be that your collet holder is fine, but your collet has some radial and/or angular runout.

You could also perform these tests directly on your mill, but you would have to adjust the tram of the mill using Rollie's dad's method to ensure that the z-axis of your mill is parallel to the spindle axis of rotation --- check both "tram" and "nod" directions. The nice thing about the runout you see on the collet holder is that it improves the accuracy of Rollie's dad's method

-F

 

[jakes_66]

Wouldn't it be a lot simpler to chuck up a piece of drill rod say 1/2" diameter, make sure it's running true. Then, take your collet holder with a 1/2" collet and clamp it on the piece of drill rod in the lathe and check runout of the arbor this way?

I agree with this method. Definitely use the 4 jaw chuck and dial that drill rod in until it's dead-nuts perfect. Snug your collet and holder on the drill rod and you can get an indicator reading on each end of the taper.

Mark any high spots with a Sharpie and disassemble, rotate the collet 90 degrees (relative to the holder), repeat and see if the high spot 'follows it'. If the high spot stays put, then you'll know the runout is in the holder. If the high spot rotates 90 degrees, the runout is in the collet.