ANSI working drawing callout for a non-PEM "Lanced type M3 thread"

[CADALL]

My client has a 1.5mm thick aluminum sheet metal part that needs to have a call out with a "lanced" type M3 thread instead of using a PEM. Can someone tell me how to ANSI properly call out this Lanced M3 thread hole on my sheet metal working drawing?

http://www.illustrativedesigns.com

Product Designer of Contract

 

[MikeHalloran]

"Lance" usually refers to breaking out and bending a rectangular tab.

You probably want to specify "Pierce and Extrude", in which you might specify the minor diameter to be formed, show and reference the OD of the formed boss on the back side, and perhaps specify a minimum extrusion length for the boss. ... but that last is problematic because the boss 'end' surface is typically torn and very rough, since it is a fracture surface. You would get the specified minor diameter from the tables for an M3 "Express Tap", or thread forming tap, because you don't have enough metal available to be throwing it away by cutting a thread.

You will probably have to work with your fabricator and his tooling supplier to get a spec that he can actually meet.



Mike Halloran
Pembroke Pines, FL, USA

 

[MintJulep]

Is he possibly asking for a flowdrill operation?

http://www.flowdrill.com/english/introduction.htm

 

[MikeHalloran]

Flowdrill has to leave the part in -0 temper, probably not desirable.

Pierce/extrude and express tap is done cold, so no loss of temper.



Mike Halloran
Pembroke Pines, FL, USA

 

[TVP]

I am not aware of an ANSI standard scheme for dimensioning extruded holes. The method I am familiar with is described in the following documents:

http://www.a-sp.org/database/pdf/CarsAsdm/Chapter3/section3-04.pdf

http://www.bossard.com/index.cfm?app_action=file_open&app_fileID=94&app_source=orderdb_file

http://www.taptite.net/pdfs/documents/TAPTITEII-CONTI-reminc.pdf