Need help with Kreg pocket hole jig 320

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Forum topic by je_an posted 07-29-2021 04:25 AM 299 views 0 times favorited 6 replies Add to Favorites Watch
View je_an's profile


5 posts in 125 days

07-29-2021 04:25 AM


I am trying to use this jig for the first time and I am little confused by the thickness measurements. I have 1 1/2” thick wood, but on Kreg’s little measuring device, it goes beyond 1 1/2” line. The markings on the Kreg’s measuring device doesn’t correspond to the true measurements.

Why is the thickness on the Kreg’s measuring device different from the true measurement? How should I be using the thickness measurement? Should I be setting the drill bit stop and the guide to more than 1 1/2” even though the wood is truly 1 1/2”?

The instruction that comes with the box doesn’t really explain this. Other sites and videos that talks about this jig does not say anything about it.

Thank you so much!

6 replies so far

View Rich's profile


7369 posts in 1805 days

#1 posted 07-29-2021 05:02 AM

It’s not a ruler. It’s showing you which zone your piece falls into. They’re telling you to use the 1 1/2” setting, not that your piece is less than 1 1/2”.

The solution is simple; drill one and see what happens. That’s clearly not expensive hardwood, so just give it a go. There’s no better way to understand the jig than to work with it.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View SMP's profile


4728 posts in 1121 days

#2 posted 07-29-2021 05:04 AM

thats a range, not a line. note that there are 2 lines around each fraction? whatever that range is, thats what you set the stop collar on the drill to.

edit: look on page 6 for clarification

View LittleBlackDuck's profile


7924 posts in 2037 days

#3 posted 07-29-2021 01:10 PM

Have you considered that maybe your tape measure is wrong…

Just kidding and welcome to LJ…

The two gents above are correct, if they agreed that the tape measure is wrong… just kidding again… the marking are just indicators as they said.

Nevertheless, I reckon that Rich guy has a dodgy set of calipers.

PS. You don’t need to buy a metal detector to tell there’s a staple in your timber.

-- If your first cut is too short... Take the second cut from the longer end... LBD

View je_an's profile


5 posts in 125 days

#4 posted 07-29-2021 03:09 PM

Thank you so much everyone.
Yeah, I have tried drilling a test piece and there was no visible pilot hole on the other side. Couldn’t tell if the hole was good or not.
Thanks again!

View WoodenDreams's profile


1412 posts in 1127 days

#5 posted 07-29-2021 07:42 PM

Your manual should show a diagram cut out of the complete drill hole. If you drill through and see a hole from the pocket drill bit, you may have drilled too far, providing less strength to the joint when tightened down with a screw.

This might help. Scroll down to the middle of this site, to the section “What makes a pocket-hole strong”. Notice the diagrams (drill, drive, done)

View je_an's profile


5 posts in 125 days

#6 posted 07-30-2021 05:48 AM

Got it. Thank you!

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