Design Suggestions

[[To...]]

Picture below is for a functional gage use in mfg process. Due to the length of the Datum A feature, position results at the other end can be quite unstable. Unlike a shaft with a bearing journal on each end, designated as A and B (A-B), I don't see creating a datum structure like that. Possibly changing datum A to the larger, longer diameter???

How would you change the dimensioning in order to make the inspection more repeatable yet still produce an accurate functional gage?

All 3 diameters are used but I don't know how much of the larger diameter is used. I assume a portion of the larger diameter is merely a handle.

pin gage.jpg

[[Ma...]]

Why can not be the longest cylinder as main base? Everything have M on itself and on A too.

[[Da...]]

Seeing that everything is on the same center line I would use the largest cylinder as datum -A- and then use run out for the small cylinder instead of position.

[[Ke...]]

I would not want to make any changes/suggestions (as the inspector) without knowing the exact function/application.

...based on just the info I have in front of me, I would consider making the second smallest diameter (between A & B) Datum C, and checking the position of the largest diameter to Position to A-C

[[To...]]

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Functional fit of firing pin hole on bolt action rifle

Screenshot 2022-12-06 145342.jpg

[[Ma...]]

Thx for sharing Tom.

The longest cylinder will have bigger tolerances due to usage and friction, so as Keith suggested - i would take middle one - crucial on this part will be the smallest cylinder, but all fitting will be upon middle one.

But we are talking about really tight tolerances right?

[[Ke...]]

Very cool.
Based on the application, I would lean toward this (attached)
It looks like only a small area of the smallest diameter (currently Datum A) is a functional area; so you may want to consider defining a target area to evaluate to New Datum A
For the largest diameter, it looks like the full length is used after the smallest diameter has fully engaged; so my preferred datums for evaluating that would be the A-C co-datums.

[[Ro...]]

Since all 3 diameters simultaneously fit at the same time on the same axis, I would use all 3 diameters as the alignment. A-B-C as co-datums for the primary.

[[Ri...]]

I've worked on fire arms in the past.
This is the typical measurement back then.

Hope this helps

Screenshot 2022-12-06 145342.jpg