huangyhg

hole diameter and call out question
we make some parts with a pattern of holes on a 28-3/4 inch "bolt circle), dimensioned as shown in the attached image.
there is no "tolerance block" in the drawing format/border.
what is a (the?) correct interpretation of the 1-1/16 inch hole size tolerance, and how close each hole must be to the 28-3/4 inch diameter.
thanks,
dan t
in a nutshell,
1. the size tolerance depends on the block tolerance for fractions (if there is one).
2. at mmc, the hole must be within +/-.005 of your bolt circle and +/-.005 of the specified angular orientation.
i'm sure that there are others here who will feel that this explanation is simplifying it too much and will expound on the correct interpretation for you.
good to know you got shoes to wear when you find the floor."fff"> - robert hunter

i think you are mixing apples and oranges. fractions and decimals should not be used together as you have. i am not sure what standard is being invoked, but it appears you have a need for more training in whatever standard is being applied.
you have indicated that there is not default tolerances in your in your drawing format. as there is no tolerance given for the diameter of the hole, there is not correct interpretation of the hole tolerance per ansi standards. since the mmc cannot be establised, the bonus tolerance should be assumed to be zero and all holes should be located within the .010 tolerance shown, plus any bonus tolerance from datum b.
peter stockhausen
senior design analyst (checker)
infotech aerospace services
yup, not established tolerances means there is no interpretation. i would ask the drawing's supplier for a written explanation. i would also ask that the drawing be converted to decimal dims only, and updated to establish tolerances.
matt lorono
cad engineer/ecn analyst
silicon valley, ca
there is not correct interpretation of the size tolerance - it's just plain missing.
you can make the holes as big or small as you like and technically you aren't wrong.
because of this i believe you mmc is down to 0 hole size on the -ve sice and is infinite on the plus side so your holes can be almost anywhere as they increase in size.
ask the customer or whoever for the hole tolerance. you may want to double check there is no reference to standard drill tolerances anywhere.
if you can't get information from your customer or whoever made the drawing and you have to make a guess, i'd suggest assuming typical drill tolerances for the holes. for dia 1.063 this would be +.012 -.001. however there is risk associated with this approach.
kenat,
call the engineer and ask him. this is something they should be able to answer. if not you have a bigger problem.
chris
"in this house, we obey the laws of thermodynamics." homer simpson
thanks for the input.
we are the customer .
this is a translation by an experienced pro-e contractor of a drawing dated 1963, of a part that evolved from parts first made in 1950.
the hole is described as a 1-1/16 inch drilled hole on those sacred parchments.
dan timberlake
tmoose, back then it may have been a mistake. or there may have been workmanship standards or similar in place relating to drilling hole sizes. my guess would be to use the typical drill tolerances i gave you.
kenat,
oh, and whatever you decide to do, make sure and update the drawing to include it.
kenat,
if you can furnish the parts that fit together utilizing the 1 1/16 dia holes, i could perhaps develop a scheme for dimensioning the part in conformance with y14.5.

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