No [ - C - ] datum on engine bracket?
No [ - C - ] datum on engine bracket?
(OP)
Every hole or slot is toleranced to [-A-],[-B-]. [-B-] is a slot. [-A-] is a plane perp to the slot. How do I align the part for layout purposes? The part is 8 times longer then the [-B-] slot.





RE: No [ - C - ] datum on engine bracket?
It would be better if the hole was in a positional tolerances in MMC and the slot was also in MMC. Now you could use a checking fixture (functional gauge) where there would be a pin the shape of the datum B slot but in a MMC size and theoretically oriented to the hole. Place the part over the datum B pin and one will see a certain slop. The positional checking pin for will be placed in the hole to confirm its location.
Dave D.
www.qmsi.ca
RE: No [ - C - ] datum on engine bracket?
Appreciate the function gage info. I do have MMC. For capability studies of machined hole positions I plan to set it up on the CMM RFS for the variable readings. Maybe if the [-B-] slot locater had 2 spheres with a spring in between forcing them apart, but I just don't think I'll pass an under 10% R&R with that.
Thanks Again,
Gary
RE: No [ - C - ] datum on engine bracket?
As far as the 10% R & R value on critical characteristis, one must remember it is a percentage of the process and not the tolerance per MSA 3rd edition. The way it is set up on the B slot, I am pretty sure that you will not make it. You probably will be lucky to get under 30% and most likely 30 - 50%.
Good luck on that one!
Dave D.
www.qmsi.ca
RE: No [ - C - ] datum on engine bracket?
I finally figured out how to do this. I have enclosed a web site reflecting capability studies on positional tolerances and how it just doesn't work out. This is a part of a presentation that I made to an ASQ group in one of their dinner meetings.
See if it makes any sense to you. I hope that this will help you.
http://www.qmsi.ca/capabilityindex.html
Dave D.
www.qmsi.ca