Keeping top flat with PH screws

[Jon Wilson]

I'm building an entry bench using 2x4s. I am jointing 3 sides and am having a dickens of a time keeping the shelf and top flat using the PH screws.

I emailed Kreg for suggestions and haven't heard anything back from them.

I'm about ready to give up on the PH method and order up some clamps that fit the project. This is the largest project I've tackled so far and don't have clamps big enough just yet.

Any suggestions on keeping things flat?

Thanks!

[Prashun Patel]

Clamps will beat them into submission, but the twist you're experience is likely from the squirrelly nature of 2x4 construction lumber. Have you let those guys acclimate for a good long while before milling? That can help settle them down a little. Sadly, one NEVER has enough clamps. Welcome to the club. When I started, I had some luck with ebay F-style clamps. They come in lengths up to 48" and while they have some flex, and you usually get a lemon or two, they can serve the purpose and are always serviceable as backups for tricky/huge glueups.

[glenn bradley]

I think I am hearing that the material is not milled square and / or does not set flat of it own prior to glue, clamps or screws, yes? I have never been a fan of trying to force material to my will as the stubborn ol' stuff generally wins. Screws can certainly be used in place of clamps for 'some things'. These 'things' should only require that they need to be held in place, not forced into place (although you can get away with murder using plywood and melamine but, I digress :)).

A screws ability to hold something is only as good as the screws grip is strong. Soft wood can result in threads stripping or heads pulling through under the best of circumstances. Do you have any band clamps in your truck or car trunk? These or rope with a tourniquet can be used inventively. I for one hear a resounding call to "get more clamps, get more clamps, get more clamps" but, that is just in my head along with the other voices :rolleyes:).

Are there any Creekers nearby who could loan you some clamps for a day or two? You and I are about as far apart as we can get without getting wet (I'm in SoCal) or I'd lend you some of mine :). Anybody care to help Jon out?

[Jon Wilson]

In short...

They have sat in my shop for several months.
Once milled they fit nicely and lay square.

I guess I didnt explain very well; when I begin to screw the top in place I get a bow (bottom to top). So there's a cup on the bottom.

I ordered a few clamps today, they should be here Thursday. I'm going to forget the PH screws and go with a glue up. Since I posted the first entry I have tried 2 more times and each time I get the bowing.

I give up!

[Phil Thien]

Pocket holes are great, but you have to clamp the snot out of the parts before you screw them together, otherwise driving the screws in will cause the parts to shift around.

[Pat Barry]

Whats the bench look like Jon, not understanding the shelf and top aspects you refer to. Also, are you using the coarse thread pocket screws for your project?

[Jon Wilson]

similar to this but scaled down, and yes, I'm using the coarse threads. That's all they had at the big blue store.

[Rick Potter]

I have no idea if it would help, but Kreg does make a larger insert for your jig which takes larger screws for 2x's.

Rick Potter

[johnny means]

Buy a few extra 2x4s and use them on edge. This will make cupping less of an issue.

[glenn bradley]

when I begin to screw the top in place I get a bow (bottom to top). So there's a cup on the bottom.

So what the boards are being pulled down onto is a bit too low? Could some shims be placed between the mating surfaces and out of sight. This could prevent the boards from being pulled down farther than they should; or am I still not getting it ;-).

[Jon Wilson]

Got a response from Kreg. Seems some of you nailed it! (No pun intended)

Quite simply, the answer is to clamp the crap out of the boards to keep them flat!

I was using a couple clamps but not enough of them, apparently.

And after all of this I'm going to end up doing a glue up for the top, but at least I know for any future endeavors
and I was able to get an answer straight from Kreg and pass on the information for anyone else that may need it.

Thanks for all the input, if nothing else I have figured out that I want the Master PH setup,
I have the HD now and clamping the jig for each set of PHs is a PITA!