METRIC TAP ON INCH DRAWING

May 19, 2006 3 Replies
J

For the following examples, where INCHES is the default dimensions for a drawing, which METRIC TAP call-out is correct according to ANSI/ISO standards, or your company practice?



You'll have to pretend that @ is the proper diameter symbol, and -> is the depth symbol...



A) inch dims with metric thread


2X @ .276 -> .827 M8x1.0 - 6H -> .630

B) metric dims with metric thread (with brackets designating mm)


2X @ [7] -> [21] M8x1.0 - 6H -> [16]

C) dual dimensions


2X @ .276[7] -> .827[21] M8x1.0 - 6H -> .630[16]

D) none of the above ;-)



Any advice would be appreciated.



Thanks,


-JOSH



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F

I just do "A". Just show the metric tap with the depth and drill in inch. All you are doing is calling out the spec for a tool, and that tool just so happens to be called M8x1.0 instead of 5/16-18 UNC.

(Just a side comment: unless there is a need to control the thread beyond what is normal, don't bother calling out the drill size and depth; just callout the tap and its depth. Let the vendor work out what's best for them. In theory, this will save you a little $ ->

fewer specifications = less cost.)

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R

Josh,

I do "A", but I delete the tap drill data and change the units to fractional. This is what my manufacturing guys like. So, it says "M8x1.25 - 6H -> 5/8".

When manufacturing's happy, everyone's happy.

Reaper.

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F

Well, CAM guys might disagree with that fractional statement. :)

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