2x20 Shank tips

[baylorbear]

Does anyone use shank type tips? I normally use a 2x20 2mm ruby tip. I need to to setup a 2x20 2mm ruby shank tip and measure a sharp edge. Do you calibrate them the same or do you have to set up the calibration differently.

I really do not know the benefits, if there are any for using such a tip.


I hope this is an appropriate thread for the PCDMIS forum. Thanks.

[Paul Sarrach]

When you Qual it you need to check the Shank Qual box. The biggest thing to watch out for is you vectors when you are taking that sharp edge point. And try to stay just above the equator, the closer to it the better. Try to use a Rmeas point it will so save you many headaches and give you better repeatablity. Anything I miss?

[Perry Fisher]

I have used them but reading posts concerning shank tips the experts here (Matt) highly recommend staying away from them, especially if you have a tight tolerance. Have you tried using a ball stylus and edge points to control the depth of hits being taken? You should be able to pickup a sharp edge in this manner.

If you have no choice but a shank probe check the shank qualification area and set the offset to the same value as the depth you plan to use measuring your sharp edge.

(edited before the GP catch me again today)

[baylorbear]

Tight Tolerance

I currently use a 2mm ruby stylus and I use edge points. My supervisor had a question about some edge points being off. I think it was due to flashing but what do I know. He suggested using a shank tip. I thought I would humor him by checking into it. My tolerance is .5mm it was .35mm. Thanks for the help.

[Paul Sarrach]

[quote=Perry Fisher]I have used them but reading posts concerning shank tips the experts here (Matt) highly recommend staying away from them, especially if you have a tight tolerance.

If used correctly the are a great tool. And some jobs they are the only tool that can be used.

[Perry Fisher]

Just to humor him use a shank probe, and shank qual offset about middle way of the straight portion of the stylus. Then run your program with depth at each end of the straight portion and look at the difference in results. I had to do that to satisfy my own curiousity.

[baylorbear]

[QUOTE=Paul Sarrach]

I have used them but reading posts concerning shank tips the experts here (Matt) highly recommend staying away from them, especially if you have a tight tolerance.

If used correctly the are a great tool. And some jobs they are the only tool that can be used.

What are the scenerios for using a shank tip versus a ball type? I have used right angle and star probes also. I am going to try the shank and see what I get.

[bw_bob]

I've used shank probes on several occasions and found no problems. We have plates with angled edges for one example.

[jjewell]

Greg,

Hey there! Who is this knucklehead thats insisting on the shank probe, some old school dude I bet.

Try it if you like, couldn't even begin to tell you how to calibrate one, NEVER HAD A NEED !

Like Perry mentioned and as you know edge pts work, but soemtimes it won't because of wierd geometry. If you surface is not perpendicular with your edge this can be an issue. You can just put a surface pt near the edge then use another surface point using the other for "relative measurement.

Good talking with ya !

Cheers,

[Paul Sarrach]

I have used them, if you have not, how can you have an opion? In the plastic world there is that need. I have done tests to prove out results, using optical comparitor, vision system ( which in this case would be a perfect tool to use) and hieght gage. when you are dealing with a edge that comes to a sharp point you have to use a shank, they make them because there useless and should not be used. You have to be careful about the vectors, where it hits, they are great for 2d dimensions. Matt never said never use them.

[baylorbear]

Hey Jim,

I really don't think the points in question are a problem. I am the coordinator but we have a supervisor type that has been in Quality a hundred years now. I don't think he was here when you guys were. The problem is the parts do not match the cad. The parts have a chamfer and I have set up the points to hit correctly. I use edge points in this case. I have changed edge points to surface points before and used relative measured points. I could see using a shank probe if I change the vectors to come in 0,1,0 and hit the sides. I talked to a few guys for direction on how to calibrate the tips and there use. I thought I would give it a try so I could add it to my repertoire.

[craiger_ny]

Used to use them a lot when I did sheetmetal. Don't let these guys scare you use it there are some legit applications for them that you will be thankfull you had it. However, listen to the folks that warn you about tight tolerances they are right. If you are in the ±0.005 tolerance range then you are well within the capability of a shank probe in 99.9% of the cases you will want to use it. Worst thing that will happen is you will get something out and have to verify your readings using another method. If you are not the type to do that then you probably shouldn't be running a CMM. Give the shank a shot and when in doubt, lay it out.

[Matthew D. Hoedeman]

Matt's rules for shank probes:

1) Pcdmis has no way of knowing if you are using the shank or not, it ALWAYS assumes you are using the ball of the tip, and you have no way of telling it anything different.

2) You can use the shank, but why bother calibrating it? The shank diameter and the tip diameter are the same (or the dang well should be). If the tip is 100% square to what you are checking (edge point and surface, which it needs to be for accurate readings) then using the depth will give you the right results, the shank probe only gives you more 'depth' to use than a ball probe since the diameter of the ball carries up the shaft.

3) If your shaft is not 100% perpendicual and sqaure to what you are measuring, then the deeper you go beyond the tangent of the ball, the farther off your reading will be. 5 degrees off angle and 2mm beyond the tangent of the ball, your reading will be wrong by 0.174mm. It is real simple to get the amount of error using a cad system, however, you can do it with a calculator as well.

4) What is your tolerance and how close to it's limit will you accept your parts? If you limit your acceptance to a certain percentage of the actual tolerance band, you can use off-angle shafts to check the part. However, any reading within the amount of error you ARE inducing by using an off-angle shaft to the tolerance limit should be rejected (let's see the ******** accept this one!). If you are just 5 degrees off and going 2mm deeper than the tangent AND you have a tolerance of +/-1.0mm for what you are checking, then ANY point falling outside of +/-0.826 is OUT OF TOLERANCE. You, as the operator, MUST account for the amount of error YOU are inducing into the measurement of the feature and must accept or reject accordingly.


So far, I have not had to do any plastic's, but I have used shank probes, but only for one thing (and I don't even use them for that, anymore) and that was digitizing the profile of a flat blank. We used to use the ceramic probes for this, but they break easily. However, dig out your mic's and check the diameter of an extension (not a cartridge extension) and check it 10 or 20 times around the diameter. I have some that are within 0.0002" all around so I built a 'custom' probe and used the diameter of the extension for the size of it. I do not calibrate it since I only use it for a flat, 2-D profile. After it is digitized, I (yes, ME, MYSELF and I) have to turn the scan data into cad data for creation of dies and it gets altered up to 0.012" (personal limit) to make real, true geometery (lines and circles, NO SPLINES). With tolerance of +/-1.5 to +/-2.0 on these, these 'limits' are more than acceptable for me. So, it will depend on WHAT you are doing, HOW you are doing it, TOLERANCE and your knowledge of what amount of error YOU are putting into the process.

[Rick Coleman]

Agree with that

That is about the only way I use a cylindrical probe. A simple 2D, flat blank scan to either establish the profile for the wire guys or to verify the die being correct to our last developed part.

[jmgreen]

Most of what has been said here is valid. Matt has some good points. I used to use shafts all the time but rarely use them now. I have yet to try them in PCDMIS. I would think you do need to qualify it however. The best advice I can give is make sure the shank is perpendicular to the edge. As Matt pointed out you can get some real strange readings otherwise.