Fastener Grades.

So I was trying to figure out what M3 fasteners to order at Mr Metric, and fell into the standard state of confusion when offered too many choices I didn't understand.  So, here's the relative price breakdown of a standard piece (or close; I didn't bother to confirm that the M8 piece I randomly selected was available in all the materials).  Sorted by price, with the different sizes marked with ***.  All the items reference standard DIN439B.

Note that Mr Metric has a huge price break at 101 pieces, so be sure and pick that number and not 100.


class              size     type                         price
-----              ----     ----                         -----
STEEL CLASS 4 ZINC M8X1.25  Jam Nut Steel 4 Zinc         .04
STEEL CLASS 8 ZINC M10X1.25 Jam Nut Steel 8 Zinc         .05 ***
STEEL CLASS 8      M7X1.0   Jam Nut Steel 8              .05 ***
BRASS              M10X1.5  Jam Nut Brass                .15 ***
STAINLESS STEEL A2 M8X1.25  Jam Nut Stainless Steel A2   .15
STAINLESS STEEL A4 M8X1.25  Jam Nut Stainless Steel A4   .21 

Metric Fasteners, Great Price!

Much thanks to coworker Drew who told me about Mr. Metric, which has great prices on (as you might have guessed) metric parts.  They've even got M2 sizes.  Various grades, etc.  $6 flat rate shipping, and free shipping over $50.  Example price: M3x8 stainless steel socket head screw (pictured), $.06 each in quantities of 101.

Update:  I don't recommend KOVA fasteners from India, no matter how many times they leave spam in the comments below!  Update: and Udehra too! Update: three times, Udehra stop it!  And Indian Cutting Tools!

Imperial Screw Sizing

So I was trying to make a mount for my new Sony cam which has pre-drilled M2 (2mm) mounting holes. Just the wrong size for a 4-40 standoff!!!

Here's the formula for Unified threads -- those are the ones with a #1 - #10 at the front.

    major thread diameter = 0.060'' + (0.013" * N)

The second number (i.e. 40) is the number of threads/inch.

So a #4-40 has a major diameter of 0.112", or 2.8448mm.