bolt circles

[HIRAH]

so here it is for you inspection gurus.
say i have a call out for a 5.00" +/-.01 diameter bolt circle with 4 equal spaced .500 thru holes.
let's say the part has a 1.00" diameter thru bore.
say the program is correct, optimal tooling etc... the holes are good in relation to the bolt circle.
there is no true position callout for the holes to anything.
is it correct or just accepted/common practice that the true position of the bolt circle to the id would then be taken from the tolerance of the bolt circle?
so the holes would have to be +/-.005 from their position?

just looking for clarification on which is correct. this is why i always try to specify exactly what i need for tolerances called out clearly.
thanks, Ron

[Bluesman]

Originally Posted by HIRAH so here it is for you inspection gurus. say i have a call out for a 5.00" +/-.01 diameter bolt circle with 4 equal spaced .500 thru holes. let's say the part has a 1.00" diameter thru bore. say the program is correct, optimal tooling etc... the holes are good in relation to the bolt circle. there is no true position callout for the holes to anything. is it correct or just accepted/common practice that the true position of the bolt circle to the id would then be taken from the tolerance of the bolt circle? so the holes would have to be +/-.005 from their position? just looking for clarification on which is correct. this is why i always try to specify exactly what i need for tolerances called out clearly. thanks, Ron

OK here is what you do, Make the BCD to w/in +/- .005 then put the BCD about .500In off center of the 1" bore then let the guy that designed the part tell you whats wrong with it based on his drawing. (Hey it will get a few laughs from the toolroom anyway)
For the most part if not using TP on a BCD. Then you would most normally just draw it with the X Y loc for the holes. So for the most part you have a print that is not complete and I would ask the guy that drew it what he wants. You really can not have a tolerance on a BCD if the BCD is loc to a bore. What you need is lets say 5.000 BCD TP to -A- .010. That is my best guess.

Bluesman

Bluesman