Inline Bores

[strohtm]

I'm updating a 50 year old part/drawing and making a few changes. As I make the new drawing I would like to get it closer to today's standards.

I always struggle with the concept of inline holes and the best way to tolerence them.

This part has 2 bores that are to be held to .0005" dia. The bores are inline and 9 7/8" apart.
I've used a positional tolerance on the bottom hole and a total runout for the upper hole relative to the bottom hole. I've left the limit dimension to drive the form or the holes.

A single shaft will go between the holes and the lower portion of the part will contain gears to drive the shaft.

I've been doing machine drawings for 25 years but GD&T is fairly new to me. I've only used it on a dozen or so complex parts.

Will this get me what I'm looking for? Have I properly applies the correct symbols?

 

[strohtm]

second veiw of part

 

[ctopher]

Try looking at projected tolerance?

Chris
SolidWorks 10 SP4.0
ctopher's home
SolidWorks Legion

 

[PeterStock]

I give the large hole a true position (coaxial in this case) tolerance of .0000 at MMC to D at MMC.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

http://www.infotechpr.net

 

[pmarc]

General question - which GD&T standard are you trying to follow, ASME Y14.5 or ISO? I believe ASME, but I am asking just to have it clear.

Here is another method that can be used:
Please take a look at fig. 5-53 of Y14.5M-1994 standard. Personally I like this one (especially when location of holes relative to datum reference frame is not so important as their coaxiality), but a lot of GD&T users freak out when they see positional tolerance without any datum reference frame, so this might look weird and incorrect at first glance.

 

[axym]

I agree with pmarc's suggestion. If one hole is made the datum feature and the other is toleranced relative to it, then the requirement is quite restrictive. Any angular misalignment gets multiplied, because of the distance between the holes. If it is really the holes' mutual coaxiality that is important, then the Fig. 5-53 method works very well.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[strohtm]

Thank you for the reply. I'll have to find the figure you are talking about.

I have a the following text book.
Geometric Dimensioning and Tolerancing
Application, Analysis & Measurement
per ASME T14.5-2009
James D Meadows
ASME Press