Splitting Wood (Pocket Hole)

[Chap]

Using this as a guide:
http://sawdustalley.co.uk/How-to/shaker-table/index.php
I'm building a coffee table.

The problem i have, is when screwing the stretcher to the leg using the top pocket hole, it's making the leg split at the top.

(I'm using el chepo Wickes planed softwood)

Can anyone explane why this is happening, and why it happens to my work and not mateys from Sawdust Alley!

Thanks
Nathan

 

[JohnD]

(not that I'm much good at woody stuff) but, are you drilling a pilot hole for the screws which is big enough for the shank to pass, so that only the thread bites into the wood?

(I know that in softwood you can make it a bit tighter than that, but you get my drift?) there must be a table somewhere of drill sizes to screw sizes in soft, hard and oily woods.

 

[Jasonb]

Are you using proper pocket hole screws, countersunk screws will split the wood.

It is more likely to be your cheap wickes "whitewood", go to a decent timber supplier and get their best quality PAR softwood which will be a redwood and much denser and resinous.

Jason

 

[big-all]

could be poor quality timber 'to near to the edge 'screws to big for the job.and as johnb says drill a pilot hole[especialy near the end or edge]

in general a pilot should be the same size as the solid bit within the thread
a number 6 for example would be a 3mm pilot

also if your using old fashioned slotted or brass screws the thread tapers from one end to the other so could cause splitting

what size screws you using and how close to the edge/end are they!!!!!

 

[Tozzy]

Don't forget to change to small drill bit and create a little 'cup' for the screw head to sit snug in, if you're using countersunk screws of course.

 

[Chap]

Thanks for the replys fellas!

Right then, to make myself clearer..
It's not the part with the pocket hole in that's splitting (stretcher), it's the part this is screwed to (leg). No pilot holes in the leg

I got the pocket hole kit from Rutlands, so this came with some screws (self-tapping pan head, which are the ones i used), step drill and stop, square-drive screwdriver bit.

The screws measure 4mm across the thread, 1-1/4" long, and have the self-tapping start.

The fixing is about 10mm from the edge (I'm getting the impression this is the main culprit)


Looks like i'm after better quality wood then, and think harder about the placement of the screws?!

 

[JohnD]

No pilot holes in the leg

That's what you need.

 

[Chap]

Godamit. That wasn't in the instructions. Doh!

 

[big-all]

ok try this

take your legs

open up the splits feed in wood glue

quickly clamp to hold the split together
drill out the pilot
flood the hole with more glue
fully assemble the components leave fully clamped till glue is dry

if your drilling within 10mm of the edge this isnt a problem in its self but the angle will bring the point progressivly nearer to the edge

 

[Jasonb]

You shouldn't need a pilot in the leg as the Pocket screws have a self drilling point not a self tapping one unless rutlands have sold you some cheap alternative. I always use the Kreg screws with the flanges head

Jason

 

[Chap]

You shouldn't need a pilot in the leg as the Pocket screws have a self drilling point

Agreed, but the wood thinks otherwise!

Thanks for the fix idea big-all, that should help for this problem.


Next time i think i'm gonna get some Redwood, and have a play with some small offcuts before i start the project.. see what the pocket hole can and can't do.

So the Kreg screws are recomended?


Thanks for all the help

 

[Jasonb]

Just drove a 1 1/4" coarse thread Kreg pocket screw into an offcut of 32x32 unsorted redwood 10mm from the end and no splitting. And I drove it all the way in not just as far as it would go if in a pocket hole.

Jason

 

[hermes]

I reckon that if you drill a pilot hole into the leg then you could probably use ordinary twinthread woodscrews without splitting. Ideally the pilot hole should equal the diameter of the shank of the screw (not including the thread).

 

[Chap]

Just drove a 1 1/4" coarse thread Kreg pocket screw into an offcut of 32x32 unsorted redwood 10mm from the end and no splitting. And I drove it all the way in not just as far as it would go if in a pocket hole.

Noted.
Better quality wood for next time then.