Alder - Course or Fine Thread Screws???

[Stanley C. Pearse]

I am in the process of joining two pieces of Alder together.  Should I use course or fine thread pocket hole screws?

Thanks.

[Jay Boutwell]

Stanley I would use fine thread.  Although many will perfer the course thead.  My choice would be fine thread as the thread pitch on the course screw is too agressive for what I wish.  I seldom use the course thread on anything and again it is a matter of preference.  In all furniture I build out of alder such as the previous 12 drawer chest as well as the one under construction are all alder, I have yet to strip out a fine thread screw.  My personal feelings about stripping out screws is that if you are stripping out screws you are tightening them too tight in the first place.  

[Stanley C. Pearse]

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[Jay Boutwell]

I understand that this happens.  Everyone knows how fragile and fussy melamine is.

I have built a good amount of melamine cabinets in my time and although most use the course thread I seldom do.  The reason being that in failed joints I have found that often in joints where a course thread is used the particle core of the melamine gets pulled and cracked from the course thread pitch.

The way I  solved my problem was to use a fine thread and use glue on the thread of the screw.  The glue acts as a lubricant when the screw is driven in and then becomes an adhesive once the glue dries.   Just for the fun of it put together several joints using both a dry screw and a glue covered screw.  Drove in the screws and let the glued screw cure and then stressed the joint until it broke free.  I found that the core attached itself to screw and even up on the un-hreaded shank of the screw.  In breaking apart the none glued screw joints I found the shank to be clear and the thread only had a few particles of the core in the threads.  The particles were easily removed yet the core in the glued screw was considerable tougher to remove.

This is my reasoning for choosing the fine thread screw.  In theory if the course thread screw pulls and tears melamine core apart then it would stand to reason that it would in soft woods as well.  However one must realize that the insertion of a screw requires the thread to cut its thread and depending on several things its sucess will depend on the material quality and the manner it is inserted into the material.  Too fast and it will tear its way and if tightened too tight will pull and strip out the thread.  This is what happens requardless of the thread type.

  If I recall correctly when Kreg Tools introduced the pocket hole jig  there was only a few selections of screws to select from and they were all fine thread.   It was not until recent years that this changed and a wide selection of screws became available.  I guess I cut my teeth on the fine thread, learned their tricks and their limits of use and so far have experienced very little trouble with them.

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[John Schaben]

Blow out, I wouldn't think would have much to do with the thread pitch, at least not with Alder, MDF or Melamine (particle board) maybe. I'd say it was to close to the edge. What size stock are you using? Picture?

Stanley C. Pearse said:

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[Jay Boutwell]

I'll throw out another thought.  You can take a fine thread screw and set it at the edge of a piece of soft wood and drive it into the wood with out a problem however with the same piece of wood you would have a hard time doing the same thing with a course thread.  It will most likely split it because of the pressure caused by the rapid thread pitch.  So in this case I don't know what the "blow out" means.  Is it the threads that have blown out or is it the force of the inserting screw that split out the material.  Just a thought.

John Schaben said:

Blow out, I wouldn't think would have much to do with the thread pitch, at least not with Alder, MDF or Melamine (particle board) maybe. I'd say it was to close to the edge. What size stock are you using? Picture?

Stanley C. Pearse said:

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[Stanley C. Pearse]

John...the stock is 3/4" thick.

[John Schaben]

Hi Jay - I just reread the thread and blowing out the "recieving" board does indicate thread pitch after thinking about it. I've had more issues blowing out the pocket side of soft wood, usually to close to an edge or when I need the pocket on the edge of the board instead of the face.

Jay Boutwell said:

I'll throw out another thought.  You can take a fine thread screw and set it at the edge of a piece of soft wood and drive it into the wood with out a problem however with the same piece of wood you would have a hard time doing the same thing with a course thread.  It will most likely split it because of the pressure caused by the rapid thread pitch.  So in this case I don't know what the "blow out" means.  Is it the threads that have blown out or is it the force of the inserting screw that split out the material.  Just a thought.

John Schaben said:

Blow out, I wouldn't think would have much to do with the thread pitch, at least not with Alder, MDF or Melamine (particle board) maybe. I'd say it was to close to the edge. What size stock are you using? Picture?

Stanley C. Pearse said:

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[Jay Boutwell]

Good Morning John,  I guess in trying to figure out what causes blow outs and failures with screws we must consider many factors such as the manner of the screw insertion such as pressure down on the driver, the speed of the screw's rpm and also the condition of the screw's thread.  Of most importance is the condition of the wood as their composition differs from piece to piece. The hardness and moisture content of the wood as well as the grain structure will all make a difference in the resistance to the enterance of a screw thread. 

As you and I both are well aware of how easy it is for  human error in how well we prepared the pocket hole will also determine the final determination of how successful the screw joint will be.  An error of one or more of the above can lead to a failure.

I am speaking only from my own experience as to what method works for me.  I like you stated have experienced the same things with blow outs and splits and often it is caused by what you have stated in your posts.  I  arrived at my solution by using the fine thread finding that I have far less problems.  I'm sure that there is use for a course threads in pocket screw technology, as many use it.   I just have not needed a course thread very often.   I'm not disagreeing with you as you have very valid points. 

Since we are inserting a screw into uncertain wood fibers we are all bound to be surprised at the results at times.  We just have to adjust to it and figure out a remendy to fix the problem.   Have a Great Day.

John Schaben said:

Hi Jay - I just reread the thread and blowing out the "recieving" board does indicate thread pitch after thinking about it. I've had more issues blowing out the pocket side of soft wood, usually to close to an edge or when I need the pocket on the edge of the board instead of the face.

Jay Boutwell said:

I'll throw out another thought.  You can take a fine thread screw and set it at the edge of a piece of soft wood and drive it into the wood with out a problem however with the same piece of wood you would have a hard time doing the same thing with a course thread.  It will most likely split it because of the pressure caused by the rapid thread pitch.  So in this case I don't know what the "blow out" means.  Is it the threads that have blown out or is it the force of the inserting screw that split out the material.  Just a thought.

John Schaben said:

Blow out, I wouldn't think would have much to do with the thread pitch, at least not with Alder, MDF or Melamine (particle board) maybe. I'd say it was to close to the edge. What size stock are you using? Picture?

Stanley C. Pearse said:

Thanks Jay...the reason I asked is because when I joined two pieces together I blew out the piece I was joining to. Did not know if it was because I was affixing a screw to close to the edge of the board or if it was thread type (course) that I was using.  Hence the question.

[Rick]

Jay, I like this idea. 

Just a little carpenter's glue on the thread before inserting into the pocket hole?

Jay Boutwell said:

The way I  solved my problem was to use a fine thread and use glue on the thread of the screw.  The glue acts as a lubricant when the screw is driven in and then becomes an adhesive once the glue dries.