Do any of you use a granite plate offline to check parts? If so, do any of you have a thread insert pattern on it? I am about to by one and am trying to decide what would be the most helpful hole patter to have. I was thinking about staggering some 3/8-16 inserts along one short edge about 3 inches in. 3ft*6ft*12inch granite.
We do frequently use the surface plate to check parts. Neither of our surface plates have threaded inserts, instead we have v-blocks, knees and plates to bolt parts to when needed.
We do plate layout OFF of the CMM all day long to check stuff that doesn't need the CMM/will be quicker off of the CMM.
If you're referring to using the granite TABLE that the CMM has...remember...that IS NOT a surface plate..it is just an expensive rock that has not been calibrated to any spec nor is it certified to be square to the CMM itself.
Our CMMs all have aluminum plates with 1/4-20 holes spaced 0.5in from one another and we use it for fixturing/part location purposes.
We do plate layout OFF of the CMM all day long to check stuff that doesn't need the CMM/will be quicker off of the CMM.
If you're referring to using the granite TABLE that the CMM has...remember...that IS NOT a surface plate..it is just an expensive rock that has not been calibrated to any spec nor is it certified to be square to the CMM itself.
Our CMMs all have aluminum plates with 1/4-20 holes spaced 0.5in from one another and we use it for fixturing/part location purposes.
I have been a Machinist for nearly 30 years...of course I do not mean the CMM table...lol
I am purchasing a new granite for right outside my office. I have a Mitutoyo Digital Height Gage that is pretty cool and sometimes I need to fixture parts to the granite itself ( as a datum simulator). You can order granite plates with several different types of hold down options. True Stone, a Starrett company offers this. I was curious if any of you have customized your granite to better facilitate light work holding. I have a dovetail in the granite i am replacing. It was this way 26 years ago when I hired in. Problem is that it chips out.
Didn't mean to disrespect! That said you'd be surprised how many people think that rock is a calibrated part of the plate, beep off of it, use it for measurements, and wonder why they're numbers look all messed up =)
not on any new machines, for sure, but WAY back in the day, before there were table maps and so forth, the tables had to be 'flat' or the machine could never be used accurately under any conditions. They used to be flat, within the specs of the machine, but that was back when they gave a +/- tolerance (only) for the machine, like my Validator (almost 40 years old).
I used to work at a company where I was horrified to hear someone from a different plant tell me that they get their CMM tables lapped and re-certified every year .
Then I realized they used this style of CMM, where the granite is not part of the main structure.
Then it made sense.
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