Thread: Face plate runout

Originally Posted by RayG

Hi rod,
radial run-out is measured along the radius..

Regards
Ray

Thanks Ray, so radial runout is half of TIR? Is that right?

Originally Posted by Stustoys

What makes you think that?

Thats why you face the faceplate on the machine it will be used on. Now you'll want a good cross slide etc etc. But even if the cross silde is shocking and the flate plate doesnt end up "flat". it should still have zero axial runout.

Stuart

I agree on the axial bit Stuart.

Would the reworked face plate actually be flat ?

My understanding is that the centre will cut slightly deeper than the perimeter, as lathe cross slides are set up to do that. I seem to remember CBA Melbourne mentioning this is a measure to prevent mating facing surfaces from "rocking".

I can't see any benefit of measuring on the outside of the spindle flange as the OP stated. That isn't a mating or locating surface.

The radial measurement of the spindle flange should be taken on the stepped section that keys into the rear of the chuck etc if it's a bolt up type.

The critical factor would be, how well does the faceplate locate on that "peg".

Rob

Originally Posted by rodweb

Thanks Ray, so radial runout is half of TIR? Is that right?

No.... you don't divide by 2 ( at least I don't think so ) you are rotating the part around the center point, so you're measuring the distance from center to minumum radius and center to maximum radius that you will read on an indicator, and the radial runout is the difference in radius of two circles that fully enclose the surface being measured... just directly subtract max and min readings is all you need to do. ( I could possible find a reference somewhere )

Regards
Ray

Here you go...

radial_runout.jpg

Hope that makes it a bit clearer.. just subtract the minimum from the maximum.

Regards
Ray

Originally Posted by nearnexus

Would the reworked face plate actually be flat ?

My understanding is that the centre will cut slightly deeper than the perimeter, as lathe cross slides are set up to do that. I seem to remember CBA Melbourne mentioning this is a measure to prevent mating facing surfaces from "rocking".

I didnt say flat, I said "zero axial runout".
A dead center should have zero axial runout.
Now concave the lathe is cutting is another issue...it shouldnt be much, but I cant recall the number off the top of my head.

Stuart

Originally Posted by Stustoys

Now concave the lathe is cutting is another issue...it shouldnt be much, but I cant recall the number off the top of my head.

Stuart

Up to 0.02mm per 300mm diameter (Schlesinger, 7E)

Originally Posted by Michael G

Up to 0.02mm per 300mm diameter (Schlesinger, 7E)

Thanks
About a thou a ft..1 in 12000.... thats not alot.

Now if our lathe is indeed cutting concave. Do we want a face plate that is parrallel to the cutter(well half of it anyway) or do we want to scrape it flat?

Stuart

Hi Stuart,

Wrong question, the question should be what do you do if you want to turn something flat to better than 0.02 in 300? forget the faceplate....

Regards
Ray

Hi Ray,

Originally Posted by RayG

Wrong question, the question should be what do you do if you want to turn something flat to better than 0.02 in 300? forget the faceplate....

There comes a time when you just have to move to the grinder or reach for the blue

Of course you could start by scraping the cross slide.............. doesnt take long

Stuart

Originally Posted by Stustoys

Of course you could start by scraping the cross slide.............. doesnt take long

Stuart

No not long at all......just as long as you don't buy a new mill to distract you half way through the job..

My Mars's faceplate has a cast in radius at the front edge. It is not even all the way round and it drives me nuts looking at it spin. I faced it ages ago, it still runs without runout every time i use it. Its not like it changes a little bit every time i put it on (threaded nose)

Cheers,
Ew

I can understand what PC said about the edge or periphery of the FP. it's neither here or there if it's not running true (radially) but boy it's distracting. After you have dialled in a piece of work, it's nice to see everything rotate with little or no noticable movement (yea I know, it only happens with round stuff but you know what I mean) but then your eye catches the wobble on the edge of the FP and for a second I think the workpiece has moved or something!

Cheers,

Simon