J & K Grip screw dimensions... Help!

mbliss57 · #1 01-12-2021, 07:16 PM

There was a thread fairly recently that I cannot find. It had grip screw lengths and diameter and thread data.

I am looking for grip screws for diamond centered J frame stocks and non diamond centers K frame magnas.
Does anyone have these dimensions?

Better yet would be a chart of all the N, K and J frame screws for target and magnas, pre and post diamond center... but that may be a "bridge too far' ( one of my favorite movies)

I posted in WTB for the screws them selves but I can get custom screws made if I has the correct dimensions.

Thanks all.. Mike

Hondo44 · #2 01-13-2021, 10:54 AM

I/J frame grip screw 3x48:

As usual with S&W changes, there's no exact date or even a year in the case of stock screws when the change happened, only a transition period.
And no correlation with diamond grip change to no diamonds.

The small pre war 3-48 NF screw continued well after the war, transitioned to the 5-44 NF late 1970's - early 1980s. This appears to correspond to the change to the flat brass escutcheons.
Also the small screw generally corresponds to Blue washers and the large screw to the SS washers; the washer change transition is from from blue steel 1967 to 1980, to SS 1970 to about 1982, depending on the gun model.

The top screw in photo is 3x48: pre war I frames and post war for both the I frames thru 1961, and J frames thru the late 1970s.

The larger and longer bottom screw is 5x44: J frame from early 1980s on.
It's slightly longer because that's also when the right side escutcheon was no longer counter bored.

Photo courtesy of Terry C

N/K screw 5x44:

There was a screw "specification" change of March 4, 1942: a specification change in the standardization of tolerances for screw thread diameter.
For example: Side plate screw changes from old S&W 'smaller minimum diameter' tolerance of .121” - .122” x 44 to the larger minimum standardized tolerance of the National Fine (N.F.) 5 - 44 screw diameter. A 5 - 44 screw is nominally 1/8", which is .125”. The threads per inch did not change. The change refers specifically to the K & N frame 5x44 NF grip screws but also applies to the same size side plate screws on all frame sizes in this discussion.

The variation appears to apply to the pre and post war bug screw or upper side plate screw which is a 3-48 and diameter tolerance of .095" to .105". However, my Triple Lock and 1950 Target 44 bug screws are the same at .097" x 48.

Therefore, there CAN BE a difference in ‘fit’ between 'pre-change' and 'post-change' screws because the diameter CAN measure differently.

It all depends on how the tolerances "stack up". I have tested this.

Post-change screws may work in pre-change guns, some may be overly tight or some may not work at all. Also worn threads in old guns may give the impression that post-change screws do "work just fine". But very often what we find is buggered and/or twisted off screws.

More typically pre-change screws will work (and sometimes very loosely) in post-change guns because the pre-change screw tolerances allowed for smaller diameter screws to be within acceptable tolerance. Stripped screw holes in post-change guns are perfect examples and can be the result of this.

So although one may "get lucky" on occasion, I always recommend pre war (pre-change) screws in pre war guns and post war (post-change) screws in post war guns.

mbliss57 · #3 01-13-2021, 11:58 AM

Thanks Jim this is very helpful.

Hondo44 · #4 01-13-2021, 01:29 PM

Glad to share Mike,

I recall the thread you mentioned and the above was my response I believe. But my memory expires after about 24 hours!