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View Full Version : GM thread standard?



dan s
05-25-2008, 06:58 PM
I have to make some custom 6.3mm x 1 bolts since i can't find them anywhere, so i started wondering why GM had their own treading standard.

anyone know ?

ptjw7uk
05-25-2008, 07:10 PM
GM like lots of other company's made their own sizes so if you bought from them you were 'sucked' in. As Kodak made their own size film and virtually gave the cameras away for almost nothing as the only film you could buy was from them.
These days it would be easier to make your own in house thread as cnc threading machines are quite cheap these days. I suppose the purist could always argue that GM want to keep the quality control in their hands but I reckon they just want the money!!
Peter

dan s
05-25-2008, 07:31 PM
now see the funny part is that the bolts aren't for a gm product, they're for a Chinese made dust collector that I'm converting from single stage to two stage. :eek:

ptjw7uk
05-25-2008, 07:42 PM
All the funnier in that it shows that the chinese are just copying everything verbatum!!
Peter

wierdscience
05-25-2008, 10:20 PM
GM does plenty of stupid fastners just like everyone else in th automotive biz.

Latest from them are odd sized metrics 7,9,11,13 mm thread diameters.

fasto
05-25-2008, 11:05 PM
You probably won't believe this but 6.3mm x 1mm is a standard metric size. I have one from a tap & die set sold at Sears back in the 70's!

Rich Carlstedt
05-26-2008, 12:08 AM
Think 1/4-24 fellows

Rich

bob ward
05-26-2008, 01:16 AM
Or a 1/4" BSF at 26 TPI is even closer to 1mm pitch which is 25.4 TPI. Unlikely for a GM thread though unless its prewar Vauxhall.

dan s
05-26-2008, 03:14 AM
You probably won't believe this but 6.3mm x 1mm is a standard metric size. I have one from a tap & die set sold at Sears back in the 70's!


actually, thats how I made the bolts tonight. I cut some long 1/4 -20 bolts to length, and then broke out the sears die and went to town.

Paul Alciatore
05-26-2008, 03:54 AM
Here's a clue. 6.35mm = 0.250". And a 1mm pitch is very close to 25TPI. Someone just translated the 1/4" English size to metric with a metric pitch. Probably lets them make "metric" serews with 1/4" stock.