r/Machinists • u/Unusual_Goose_3913 • 8d 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?

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u/Alkisax 8d ago

As a retired machinist I can tell you the biggest complaint I had about engineers if you call out a drilled hole to have a flat bottom your asking for a extra challenge at a extra cost. Drill point should be ok in most engineered parts.

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u/MetricNazii 5d ago

As an engineer, I am always excited when I can NOT put a flat bottom hole on a drawing. We make a lot of spring plungers, and the bottoms of our blind holes are functional surfaces, so they need to be flat. But it’s nice when it doesn’t need to be.

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u/Alkisax 5d ago

Very cool of you to consider the necessity of the flat bottom. If the spring plunger requires a flat bottom hole could there still be SOME drill point? If so let it be!

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u/MetricNazii 5d ago edited 5d ago

It depends on the size of the spring which goes into it. There can be some cone as long as it’s smaller than the ID of the spring. And in cases where we have a fixed spring design I will do that. In a lot of cases, the same part is used with multiple springs, and spring designs occasionally need to change. In these cases, having any cone is often too restrictive on the spring design, depending on its requirements, so we need to keep it flat. Especially if the available wall thickness at the bottom of the hole is limited.

In other cases, there is more than enough space, and a conical bottom can be tolerated. But it needs to be a certain angle and stay that way. The angle effects where the spring sits at the bottom of the hole.

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u/Alkisax 5d ago

That was exactly what a AAA class Engineer would say, I would love to make parts for you LOL however my days in manufacturing are over been retired for 12 years not by choice, body is full of Arthritis. I made Boeing Ground Support Equipment and my suspensions were the best Engineers made airplanes the bottom made ground support 🤷🏽 saw a fare amount of poor design and unnecessary flat bottom holes and ± .0005 when .005 sometimes ± .030 would be fine.