GRK screws - actual length

[semenza]

I thought it would be good to post some info on the actual lengths of GRK screws , due to the recent thread on them and other brands.  I was using some yesterday and remembered discovering that not all of the metric conversions are accurate.

The metric lengths all seem to be accurate to .5mm, but the imperial lenghths listed in the GRK data are not all converted accurately.  EX- 20mm screws are listed as 3/4" when 13/16" is closer.  Most of them are close enough and in many applications will not matter. But a couple are bound to cause trouble if someone is not aware.

The first number set is what GRK lists them as, the second are actual measurements that I took with an Incra rule.+/- .5mm. These are for R4s but the comparisons hold true for other types that I have as well.

#4x3/4" , 20mm      =      13/16"

#4x1"  , 25mm          =      31/32"

#6x1 1/4", 30mm      =      1  3/16"

#6x 1 3/8", 35          =      correct

#6x 1  1/2", 40mm    =    1  9/16"

#8x 1  3/4", 45mm    =      correct

#8x 2"  , 50mm          =    1  31/32"

#8x 2  1/2", 60mm    =    2  3/8"

#8x 2  3/4", 70mm    =      Correct

#10x 3  1/2", 90mm    =    3  17/32"

#10x 4  3/4", 120mm  =    4  23/32"

Seth

 

[leakyroof]

As always Seth, thanks for taking the time to list all of this and the time it took to measure it all up. I think the phrase, 'in the ballpark', might apply here... [embarassed]  Esp. the stated 2 1/2" screw that's really 2 3/8" as you measured it. At least for many projects, you won't pop though something since the screw is SHORTER than spec if you were in a hurry and didn't closely measure it before driving it home.. [tongue]

 

[semenza]

This situation came up today.  I was using Kreg mini ( micro?) pocket holes with 1/2" plywood (this plywood was nearly a true 1/2" about 1/64" under). This would normally use #6 x 3/4" screws.  I used the GRK #6 x 3/4" Pan head and they came through about  1.5mm.  [doh]  You would think after starting this thread I would have checked , but I figured there must be a little lee way built into the jig.  [doh] Again.

The actual GRK length is 20mm. It made a difference  in this situation for sure.  I switched to 5/8" and all was fine. I think 5/8" might be better  for this anyway since the actual 3/4" would be pretty darn close to poking through.

Seth

 

[ericbuggeln]

A really nice screw besides that, thanks Seth. Eric