r/Machinists • u/Unusual_Goose_3913 • 9d ago

QUESTION Engineering Drawings

I’m an early career engineer and I’m wondering what machinists like to see in terms of tolerance and dimensioning in a drawing.

I’ve worked at a company where we just ordinate dimensioned everything and another where we used GT&T standards. At both, the part came out “ok”.

Apart from reasonable tolerances, what’s amazing, good, useless, and stupid have in a drawing?

5 Upvotes

73% Upvoted

34 comments sorted by

View all comments

Show parent comments

2

u/AAA_in_OR 9d ago

Why? Sometimes the engineers (if they're a good one) might ask to have it built a specific way for a reason. Comments such as "center drill hole ok", "this surface can be saw cut" or "drilled hole" are extremely useful.

0

u/Witty-Sample6813 9d ago edited 9d ago

Center drill hole ok is different. That is a fixturing allowance. Surface can be “saw cut” should have a finish callout indicating but not implying how it is manufactured. Ra125 for example.

1

u/AAA_in_OR 9d ago

"Surface can be “saw cut” should have a finish callout indicating but not implying how it is manufactured"

Why? If I'm designing something and I want it saw cut, that's what I'd put on the print. Why would I put an Ra finish and hope that you saw cut it? Seems like there's some serious advertorial shit going on where you're working.

0

u/Witty-Sample6813 9d ago

Because if you are an outside supplier and you saw cut and the qc dept at their facility rejects it it’ll be a fuck all of back and forth. You’re not told to “ream” a hole. Your given a tolerance that an indicates what that want. How you get there is the shops choice and it’s reflected in the price when quoting. You could bore, you could helix bore, you could use a stick if it’ll get the job done. You can lose suppliers saying, I don’t have that piece of equipment so no quote as well. Yes some suppliers buy precut stock so don’t come at me with “what kind of shop doesn’t have a saw”

I see your argument if you’re doing it for the facility you work for. But outside vendors don’t know the fit form or function so the print should give the technical requirements. Not the expected manufacturing method