Measuring a Plane with a Disc Probe

[#2#]

Hopefully someone has done this before and can give me a quick answer.

I have something similar to an internal snap ring groove. I need to measure the distance from one side of the groove to the centerline of the part.

The way I have my part set up the plane would have a vector of 1,0,0 and the centerline 0,1,0. I would need to take hits in the X direction with the head rotated to A90B-90.

I can get the beast to take the hits but how do I calibrate the probe for taking these hits?

See attached. I am trying to measure the .397 dimension.

Anyone?

[JamesMannes]

Only thing I think of is to use a star probe. I don't think you can get valid data from the disk for such stuff. Anyone else?

[#2#]

Only thing I think of is to use a star probe. I don't think you can get valid data from the disk for such stuff. Anyone else?

No can do b/c of the diameters involved. I don't have a star that small. If I had a smaller tip (1 or 1.5 mm) I could take multiple vector points at multiple head angles and construct a plane. For this location anyway. There is another one of these that is about 2 inches down inside a bore.

[#2#]

What about the probes like this? How do you calibrate the "pin" for taking hits?

[craiger_ny]

Pin is for reference. It does not get calibrated.

[cmmguy]

because of the size of the entry diameter, I think that you will need to measure this with "traditional" methods. Drop indicator depth gage with a foot locater to measure the depth of the groove to the face. Then from the face the centerline(maybe you can use the cmm for this).

[MrComment]

I could be wrong but I dont think you can get pcdmis to calibrate a disc probe on the flat area.

However of the top of my head one bad idea I have is you could try to use the uncompensated probe hit data from your hits to first construct a parallel plane to the .397 surface. You could then offset that plane a assumed "disc" or sphere thickness which you can measure yourself ahead of time.

I dont like this idea because your going to have to assume that the flat of the disc is always going to take each hit exactly normal to the spring groove flat. Otherwise as im sure you already know your going to get some cosine error depending how normal your part is to your probe angle.

Just a though.

[#2#]

because of the size of the entry diameter, I think that you will need to measure this with "traditional" methods. Drop indicator depth gage with a foot locater to measure the depth of the groove to the face. Then from the face the centerline(maybe you can use the cmm for this).

D@mmit man, I don't want to do none of that math sh*t!

Ok, why the h3ll didn't I think of that!? Forest for the trees I guess.

Thanks.

[cmmguy]

D@mmit man, I don't want to do none of that math sh*t!

Ok, why the h3ll didn't I think of that!? Forest for the trees I guess.

Thanks.

If you have enough of these to do, you could include the math in your CMM program and just prompt for the measurement from the hand gage. Or use a keyboard wedge and put the readings right into PCMIS prompt window.


I guess that you could also make a probe that has a tip(.75mm) at about a 15 degree angle - would that reach in and touch that face? Do that "relative" measurement that we discussed yesterday.

[JamesMannes]

No can do b/c of the diameters involved. I don't have a star that small. If I had a smaller tip (1 or 1.5 mm) I could take multiple vector points at multiple head angles and construct a plane. For this location anyway. There is another one of these that is about 2 inches down inside a bore.

Sorry wasn't paying attention to the sizes involved. Duh

[Matthew D. Hoedeman]

Hey, do you have a small fish-hook probe, we all know you have some, you would have to do a manual calibration on it, but it might work for you.

[#2#]

Hey, do you have a small fish-hook probe, we all know you have some, you would have to do a manual calibration on it, but it might work for you.

Nope, smallest probe I have (fish-hook or otherwise) is 2mm. Not quite small enough to land on the ledge.

[Matthew D. Hoedeman]

Nope, smallest probe I have (fish-hook or otherwise) is 2mm. Not quite small enough to land on the ledge.

Well, MAKE ONE, I know you can, you've done it before and the smaller the probe, the easier it is to make one!

Seriously, you may want to make one using a 1mm ball, just to ahve on hand for this kind of thing.

[#2#]

Well, MAKE ONE, I know you can, you've done it before and the smaller the probe, the easier it is to make one!

Seriously, you may want to make one using a 1mm ball, just to ahve on hand for this kind of thing.

I'll have to order one and bend it. Good tip tip. Couldn't you auto cal it as long as you limit the cal. angle to avoid the shank?

[John Riggins]

Can you access that hole from the non-chamfer side?

mabe put a gage pin in the chamfer side and it will stop against the surface you need to probe????