In imperial units the 2.5mm screw would be a 3/32 inch diameter screw with 32 threads per inch and 3/16" long. Metric equivalent is M2.5x0.45 4.5mm long ___________________________________________________________________________= __ Cris Wilson Information Resource Consultant College of Architecture, Arts, and Humanities Clemson University 864-656-6081 ________________________________________ From: piclist-bounces@mit.edu [piclist-bounces@mit.edu] On Behalf Of Oli Gl= aser [oli.glaser@talktalk.net] Sent: Thursday, December 01, 2011 12:18 AM To: Microcontroller discussion list - Public. Subject: [EE] Obscure screw size Hi all, I have a Hammond 1551R box into which fits a small PCB. The recommended shape of the PCB is given in the datasheet: (http://www.hammondmfg.com/pdf/1551R.pdf) I have received the PCB and it fits perfectly, but the Hammond box only came with the 2 screw for the lid and none for the PCB mount holes. The sizes specified are 2.5mm for the PCB hole diameter, but the screws are given as 32 x 3/16" self tapping. So the question is - what does this translate to in metric sizes? I get the 3/16" is probably the length, but what does 32 stand for? Is it for a 1/32" thread? I have trawled through pages and pages of all the many different "standards" - Whitworth, BAS, UTS, etc but I can't fit 32 into anything that seems to fit properly. The UTS (Hammond are US so I assumed this would be the most likely) is specified as X-Y where X is the diameter and Y is the thread turns per inch. 1/32 would give a diameter of 0.8mm and 3/16 means nothing in terms of turns per inch. Even if you swap them round it doesn't make sense. Whilst linking to the above datasheet I noticed it's actually different from the one I have, and gives #2 x 3/16" instead of the aforementioned 32 x 3/16". This makes more sense as #2 equates to 2.18mm diameter shank, but I'm still unsure as to the thread (not that it matters too much as it's self tapping, but I'd like to know anyway) I'm going to order some number 2 screws, but can anyone help me to confirm exactly what the numbers mean for future reference? -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .