Moderators: Random Orbital Bob, nev, CHJ, Noel, Charley

 Reply
By andythorntonjoinery
#1261064
Just bought a krek K4 jig and was wondering if you have to use their specific screws? I will probably use theirs anyhow but was wondering if anyone knows of alternatives. I looked online for buying in bulk and only place I have found is amazon who do boxes of 3000 for about £80 shipped in from USA taking about a fortnight to deliver.
Any advice welcome!
By Fergal
#1261069
I have the UJK pocket hole jig from Axminster. I have tried using pan head wood screws instead of the proper ones, but it didn't work very well. The pocket screws from Axminster are not too expensive and do work well. They should also work on your Kreg jig, although it would be worth checking first.

https://www.axminster.co.uk/ujk-technol ... d-ax885008
User avatar
By nev
#1261098
I'm sure we used to use Trend pocket hole screws (square drive) with the kreg Jigs in a previous life.
https://www.swanseatimber.co.uk/fixings ... 13828.html
User avatar
By Steve Maskery
#1261192
Yes, both work well, it's just that you need a Robertson 2 bit for the Kreg, whilst the UJK ones use a PH2 (might be a PZ2, can't remember, something "normal", though).
Last edited by Steve Maskery on 09 Jan 2019, 21:19, edited 1 time in total.
User avatar
By Eric The Viking
#1261193
The ones with the square socket are officially Robertson (headed) screws. It's a Canadian design and very good indeed. You can get them (as Kreg pocket hole screws) cheaply from Amazon, also the drivers with a standard hex shank to fit in a power drill or driver. Get the LONG version of the bits as shorter ones won't fit well inside cabinets (you can't get the electric tool's chuck into the corner at the right angle!).

There are (at least) two different thread forms that Kreg sell. The coarser one is intended for softwood and presumably anything with a more open grain, and the finer one for hardwoods. I have tried the finer thread in softwood and it doesn't grip as well, so now I carry both sorts. I don't think they are expensive considering how good they are.

To answer your first question, in my opinion the flanged head makes a big difference, as it spreads the clamping force of the screw across a wider area (and don't forget this is basically pulling in end-grain).

I don't use my Kreg kit much but I'm really grateful to have it when I need it.

E.

PS: I think the coarser pitch is also intended for chipboard, but I think the pocket hole system joints (anybody's, not just Kreg's) are too weak for that.
Last edited by Eric The Viking on 09 Jan 2019, 21:17, edited 1 time in total.
User avatar
By Steve Maskery
#1261196
Eric The Viking wrote:Get the LONG version of the bits as shorter ones won't fit well inside cabinets


+1
Or at least a medium-length one, as a normal bit-holder won't fit in the holes very well.
By Distinterior
#1261204
Steve Maskery wrote:Yes, both work well, it's just that you need a Robertson 2 bit for the Kreg, whilst the UJK ones use a PH2 (might be a PZ2, can't remember, something "normal", though).


T20 Torx heads from UJK I think Steve.....
At least the last box I had from them were..... This thread has reminded me to order some more as I'm down to my last few!
User avatar
By Steve Maskery
#1261208
Distinterior wrote:
Steve Maskery wrote:Yes, both work well, it's just that you need a Robertson 2 bit for the Kreg, whilst the UJK ones use a PH2 (might be a PZ2, can't remember, something "normal", though).


T20 Torx heads from UJK I think Steve.....
At least the last box I had from them were..... This thread has reminded me to order some more as I'm down to my last few!


Really? Oh, OK. I wonder what I've got then. I'll have a look tomorrow.
By sunnybob
#1261218
I'm somewhat amazed. I've thought about getting a pocket hole jig but had no idea I had to have special screws.
Why?
:?: :?:
User avatar
By Eric The Viking
#1261223
It has been discussed at length on here, and there are several points of view.

I think you would be sensible to use the suggested screws, for maximum joint strength and much less risk of joint damage. There are others on here who even swear by ornery countersunk jobbies.

It's almost a [shsssh!]sharpening[/] debate.

If I dare sum up:
  • The joint is pulled together almost, but not quite, at the correct angle by the screw(s). Even in a correctly-made PHJ there are forces trying to move the joint out of alignment when the piece is finished. almost, but not quite means that there are, admittedly small, forces at right angles to the "hold it tight" one. If not well controlled these can cause misalignment, gapping, or even joint failure. This is why you should clamp the joint tight before driving the screws. Aside: I have tried not doing this when in a rush to make something that doesn't matter (e.g. a clamping frame): it didn't end well.
  • Glue may be used, but at the end of the day, it's an end-grain-to-face-grain joint with very little glue area. It is a fundamentally weak joint, relying on the material strength much more than most other jointing systems.
  • The head of the screw is basically going through end grain and pulls on it along its shearing/splitting axis, to hold the joint together. The thread end of the screw might be better, as it's into face grain, but that depends on the thickness of that component. The thickness limits the screw depth*.
  • Any countersunk screw head in this context acts as a wedge, trying to split the thin and weak end grain between the pocket hole itself and the mating part of the joint.

If you are not stressing the joint, for example just using PHJ to hold a face frame together or onto a strong carcase, the above probably doesn't matter. On the other hand, if you are using pocket hole joinery close to its realistic maximums for joint strength, and/or there are reasons why the joint might be stressed in use (note that PHJ often uses no glue at all, relying on the screws alone), I'd say using the right screws can be critical.

As I said in an earlier post, the reason for the flange is to get as big a bearing area onto the end grain as possible, and to not cause a wedge with the associated splitting forces.

OK, tin hat on head, heading for the bunker now... (hammer)

E. (who likes pocket hole joinery and uses it, despite its limitations)

*Kreg chose screws with an axial cut down the point, so they can get closer to the visible surface of the face-grain material without blowing out the other side -- useful when using the system in chipboard, etc. It's another good reason for using their screws - you can get the maximum screw depth possible when doing carcases.
By novocaine
#1261224
when I use pocket holes (not all that often but sometimes they are useful) I use normal screws with a washer on the back. I've got a massive box of dirt cheap washers that lives in my screw boxes. fairly sure it is cheaper than the kreg screws but really it's so I don't have to order in something special and hold them in stock for the rare occasion I do use them.