spec for machining tolerances 1

[loughnane]

I'm looking for a spec for standard machining tolerances for different processes.

I found ANSI b4.1, but it looks as though it is only dealing with cylindrical fits (even though I see other websites using it as a reference for positional tolerances).

So is ANSI B4.1 the best out there, or is there something better.


I should note that the only reason this came up is because I'm getting something machined that is larger (12x30x1.75") than what I usually get made. Typically I would just slap .005 everywhere, but I don't feel like that scales well when I have 2 holes 28" apart.

All help is good help.

Chris Loughnane - Product Design

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[saberblue]

Check the Machinist Handbook and the Machining Data Handbook

 

[KENAT]

There are many factors that affect this. Best is to talk to your vendor.

Similar questions come up every now and then, Ctopher & I have both pasted links to sites with useful information before now.

Someone will probably suggest looking at ISO2768, I'm not a fan of it but to get some idea of achievable tolerances may be of use.

12*30*1.75 inch isn't that big, if done in a single set up +-.005 should be readily achievable but...

Do you need it?

Specify the loosest tolerances you can get away with based on Function, then make sure those are within process capability.

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[KENAT]

thread404-278305

The little section in Machineries is "Machine Tool Accuracy" in the machining section. Page 1245 on in my 27th ed. I don't see anything about varying with size.

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[juergenwt]

I would go with ISO 2768.
Go here:

http://mdmetric.com/tech/DINISO1302extract.htm