How to consistently measure these features without a cmm

Karl_Kunkle · May 15, 2017

I am trying to figure out how to consistently measure the 112 degree angle and 2.020 dimension.

My tolerance on the angle is +/- .5 degrees. tolerance on the 2.020 boss is +.003, -0.000

I do not have access to a cmm at the moment.

Thanks,

tay2daizzo8 · May 15, 2017

comparator and repo rubber? or you can figure out the drop for the 112 as long as you hold diameters...as for the 2.02..without making a monstrosity of a home made plug gage you can set up an indicator and a vblock

CalG · May 15, 2017

an accurately made sheet metal template combined with some feeler strips would go a long way.

litlerob1 · May 15, 2017

I'm wondering what the manufacturers print looks like, and how those dimensions are toleranced. I have seen worse so don't get me wrong, but calling an angular tangency point out with that tight a tolerance is stupid, even if you had access to a CMM. Not that being stupid gets you out of the pickle right?

Here's a question; how is your customer going to inspect this part? If they have a CMM use it to do a First Article Inspection and hold the other diameters close, and run with it.

R

Illinoyance · May 15, 2017

Use a linear slide to move the part under a dial indicator. Indicator drop divided by the distance moved is the tangent of the angle measured from the horizontal plane. add 90 to get the angle in question.

plastikdreams · May 15, 2017

I'd make a pin gage for the 2.02 one side 2.0205 the other side 2.0175.

For the angle make an angled cradle for the part and use and the indicator holder of your choice.

Make both from aluminum, cheap and easy to machine.

tay2daizzo8 · May 15, 2017

plastikdreams said:
I'd make a pin gage for the 2.02 one side 2.0205 the other side 2.0175.

just remember no edge break allowed when doing this

plastikdreams · May 15, 2017

tay2daizzo8 said:
just remember no edge break allowed when doing this

Yep, personally I'd make it from 7075 just for the added strength.

litlerob1 · May 16, 2017

plastikdreams said:
I'd make a pin gage for the 2.02 one side 2.0205 the other side 2.0175.

For the angle make an angled cradle for the part and use and the indicator holder of your choice.

Make both from aluminum, cheap and easy to machine.

the pin gage isn't going to fly in mine or any QC department, as was pointed out the interference of a pin and a mating angle is too loose. Not only could there be zero edge break on the pin there could also be no allowance for a radius at that tangency. And then what if the pin rocks-too small, if it moves on the flat-too big? that doesn't do anything except tell the inspector NOGO/GO, that isn't a measurement, it doesn't help the person doing the manufacturing. I used to work with a guy like that in quality, basically useless to tell the person building the part good or no good and that's all.

Not sure what you mean by "cradle".

R

Yan_b · May 16, 2017

Maybe go no go disk with guide step into the hole and then measure the height to the top, I assume the part is round.

plastikdreams · May 16, 2017

litlerob1 said:
the pin gage isn't going to fly in mine or any QC department, as was pointed out the interference of a pin and a mating angle is too loose. Not only could there be zero edge break on the pin there could also be no allowance for a radius at that tangency. And then what if the pin rocks-too small, if it moves on the flat-too big? that doesn't do anything except tell the inspector NOGO/GO, that isn't a measurement, it doesn't help the person doing the manufacturing. I used to work with a guy like that in quality, basically useless to tell the person building the part good or no good and that's all.

Not sure what you mean by "cradle".

R

After I posted I though well it'll work for the oversize but not the under but I got caught up with stuff at work and forgot lol...

As for the cradle, it would hold the part at 60° and allow the indicator to be swept from tangent to tangent, based on the shape being round of course.

I just woke up so gimme a break

CarbideBob · May 17, 2017

A reasonably straight B-port with glass scales, a ball probe and a cheap CAD program make for a low buck CMM.

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How to consistently measure these features without a cmm

Karl_Kunkle

Aluminum

tay2daizzo8

Hot Rolled

CalG

Diamond

litlerob1

Diamond

Illinoyance

Stainless

plastikdreams

Diamond

tay2daizzo8

Hot Rolled

plastikdreams

Diamond

litlerob1

Diamond

Yan_b

Aluminum

plastikdreams

Diamond

CarbideBob

Diamond

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