Kreg screws

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Forum topic by David Freed posted 09-18-2016 06:57 PM 514 views 0 times favorited 7 replies Add to Favorites Watch
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David Freed

109 posts in 3091 days

09-18-2016 06:57 PM

I have searched Kregs web site, woodworking forums, and watched videos about using the right Kreg screws “size”. The problem is they all talk about fine & coarse thread and “length” not size. Length is easy; if it peaks out, go 1/4” shorter.

Does anyone have a guide on the right size for given situations?

-- David, Southern Indiana

7 replies so far

View Chuck Anstrom's profile

Chuck Anstrom

79 posts in 2447 days

#1 posted 09-18-2016 07:44 PM

From the Kreg website under “screw length.”

The line “material thickness” shows for 3/4” material, use a 1 1/4 long screw, for example.

Is this what you were looking for? All Kreg screws are the same diameter, #8, I think.

-- Chuck Anstrom - Virginia

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David Freed

109 posts in 3091 days

#2 posted 09-18-2016 08:46 PM

Thanks for the reply, but that chart is for length, not size. Just about every Kreg screw vendor offers #6, #7, and #8. Some offer larger sizes.

The Kreg 5 size screw assortment comes with the “most popular sizes”.
A – #6×1 fine thread pan head
B – #7×1 coarse thread pan head
C – #7×1 1/4 fine thread washer head
D – #8×1 1/4 coarse thread washer head
E – #8×2 1/2 coarse thread washer head

From my searching, I found that the pan head is for thin stock because it’s smaller, the washer head is for 3/4” and up for more holding power, the fine thread is for hardwood, and the coarse thread is for softwood and plywood.

Putting all this info together, I would guess that -
A is for 1/2” hardwood
B is for 1/2” soft/ply wood
C is for 3/4” hardwood
D is for 3/4” soft/ply wood
E – I don’t care; too long

I just thought maybe someone would have a recommended use chart for the sizes so I didn’t have to guess.

-- David, Southern Indiana

View rwe2156's profile


2126 posts in 904 days

#3 posted 09-19-2016 02:05 PM

You’re overthinking it. I’m no big user of pocket screws, but I would think thread, head and length are all that matters.

If you used a smaller screw you will need a different drill bit, right?

-- Everything is a prototype thats why its one of a kind!!

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Rick Dennington

5108 posts in 2617 days

#4 posted 09-19-2016 03:24 PM

^——-What he said….!! You’re trying too hard…Just go by the screw chart, and that’s all you need….Works every time..!!

-- At my age, an "all--nighter" is not having to get up and pee...!!!

View dhazelton's profile


2292 posts in 1720 days

#5 posted 09-19-2016 03:38 PM

You can see that the longer screws have coarse threads. There is only one size as far as diameter is concerned.

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David Freed

109 posts in 3091 days

#6 posted 09-20-2016 12:37 AM

The screw assortment clearly says it has #6, #7, and #8 sizes in it. I just checked them with my micrometer. The #6 and #7 fine thread were 7/64. The #7 and #8 coarse thread were 15/128. Different numbers with the same diameter and the same number with different diameters clearly shows the numbers don’t correspond with the size. Why would the manufacturer say they have 3 sizes when they obviously don’t?

Thanks for the replies. I am setting up a cabinet shop in my spare time, and I don’t have very much of it. I hope to get time to practice with the jig in a week or two.

-- David, Southern Indiana

View bbasiaga's profile


731 posts in 1418 days

#7 posted 09-20-2016 01:24 AM

The diameter of the screw mainly comes back to the tensile and shear strength it can handle. Also to be considered is how much wood is left for the screw head to clamp against. In most of the youtube jockey videos where they make pocket hole joints fail, what you see is that the screw pulls out of the wood. The screw does not break. So it would seem that the strength of even the smallest diameter screws is more than the wood it is clamping together.

Not sure what they are doing with their screw sizes. But it seems like if you use one the right length for the thickness of the material then they have already calibrated the proper diameter for you (by only offering a limited number of sizes).


-- Part of engineering is to know when to put your calculator down and pick up your tools.

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