wood splits

[douglas E. Cooper]

I have used the Kreg jig for a few years but lately when attaching a face frame to a cabinet, I am having the side of the cabinet crack when screwing the two pieces together.  This is usually when I am using hardwood (red oak).  I am dealing with 3/4 thick material and using the Kreg screws for hardwoods.  any ideas on what I might be doing differently?  I cannot seem to figure this one out.

thanks 

[KregCS]

Douglas, 

I was curious if you are using fine threaded screws when you are joining your materials.  If not this could cause your material to split.  If this is not the case it could be in the dryness of the wood itself.  If it is really dry it will be more prone to cracking.  The easiest way to diminish the chance of this happening is by driving the screw in some and then backing it out and then driving it back in.  This allows for the screws threads to clean themselves out and drive easier. Another option would be to use some soap or beeswax on the threads of the screw to allow it to be driven easier.  If you have any other questions please let us know. 

[Ken Darga]

Doug,

I've had cracking happen to me, near the ends, in hard and soft wood,

when the screw is 1/2-1" from the end of the workpiece.

When the screw enters the wood, the screw can sometimes cause the wood to split/separate, right at the growth ring in the wood. 

Peruse the end of your workpiece, and see if that's what happened to yours.

[Jay Boutwell]

Hi Doug, You are saying that you are having the sides of the cabinet split when you are driving in the screws,  If I understand this correctly are you saying that the cabinet sides are splitting or do you mean the face frame is splitting.  If the cabinet sides is what is splitting what is the cabinet side made out of?  Hardwood or plywood made of hardwood? 

A photo would help explain this.  If you can supply a photo or two of the problem I may be able to help you.   If it is plywood then the splitting is the delamination of the plies and is becoming more common in the current day plywood and especially the plywood from big box stores of whom usually stock foreign plywood and even some of the United States labeled plywood is actually made on foreign soil.     I see that suggestions are made telling you to use wax soap, and thread in and out.  Although this might help some but normally will only make your screw to wood bond weaker and especially if it is plywood.   The threading in and out will cut a new thread groove each time and repeated times will ream out the hole.   If this is plywood and labeled red oak it only means that the veneer is made of red oak and the core is softer wood and therefore using a course thread kreg screw is the better option.  You must however use care when the course thread reaches the red oak solid hardwood as the aggressive thread with often cause screw breakage and sometimes the splitting of the plywood as it aggressiveness will introduce some sudden inward pressure that will over drive the screw and most of todays plywood will not tolerate it.   Please post some photos and I will see if I can determine the cause.

[Jay Boutwell]

It normally will and a screw will split more often than a nail.  The reason being is the shank of the nail get is holding power from friction and it is friction that resists the driving in of a nail.  A screw is a helical type of resistance and the twisting of the screw to drive it in will result in much more force that driving in a nail.  The drier the wood the more brittle as the lignin is compromised by age and dryness of the wood fibers. The closer to the end the more often and the more severe is the cracking.  There is less resistance in the wood fibers near the end as not only the lesser of the amount of wood to resist that driving and or twisting but the ends of lumber is pretty much wide open for the release of the moisture in the wood. and therefore drier that the wood further up the piece.    Wood with moisture is more limber than dry wood and will be less resistant to cracking.

Red oak was mentioned in this post and it happened to be the biggest offender as the cells are more open than other species of wood.  There is no denying of wood quality or grade as the woods that grew in a wetter environment will be a cheaper grade than

those grown in a dry or colder climate and the growth rings will show this graphically.  The close grain wood will be more dense than the more open grain wood and will also resist splitting and cracking as well.   Other factors in Nature also determines the final grade of the lumber and include such things as disease and fungus but also things knows as wind shake and or ring shake where the trees is damaged internally while growing by winds that twist and or shake the growing tree.  it might happen once or many times before the tree is harvested and some of these are not seen or detected by the mills that process the wood.  Then the other factor is the man made flaws such as processing and kiln drying.  

Doug,

I've had cracking happen to me, near the ends, in hard and soft wood,

when the screw is 1/2-1" from the end of the workpiece.

When the screw enters the wood, the screw can sometimes cause the wood to split/separate, right at the growth ring in the wood. 

Peruse the end of your workpiece, and see if that's what happened to yours.