Jacking Screws

[John Neel]

I had to replace the jambs on an outside door. As the new jambs were tight, it became apparent that they would have to be very close to the wood behind the jambs. In fact it would need to be as tight as possible and I would need no shims. So, I decided to use screws rather than nail the jambs into position. There was either brick or an ibeam behind the wood was screwing the jambs to [ There are three layers looking from the doorway 1. door jamb 2. a 3/4" board, 3. brick or i-beam.] The screws thus needed to be less than 1 1/2 " or they would jack that wood away from the brick or the ibeam. I used 1 1/4" screws.

My real worry was that the screws would jack the jamb away from the wood behind the jamb and that would make the opening too narrow for the door. The screws I used would have left about 1/4" of thread in the jamb and I was concerned that would jack the jamb away from the wood, again narrowing the doorway. So I decided to file off the the last two threads of each screw. I did that, pre-drilled and countersunk the screws. It worked very well; everything is as tight as it needs to be, the door fits perfectly, one of my better projects.

So, the question is: Did I do well to file off those last two threads and prevent jacking or was I just being my occasionally compulsive self and wasting my time? Would the screws have just pulled through the last 1/4" of the jamb and pulled the jamb tight? Did I somehow reduce the effectiveness of the screw? [ Will my house fall down? :) ]

John Neel

[Jason White]

If you use minimal-expanding canned foam around the perimeter of the jamb, you're effectively gluing the door in place. You won't have to worry about the strength of the screws after that -- they don't really provide a lot of structural strength anyway. Mostly, they just hold things in place until you apply the foam.

Jason


I had to replace the jambs on an outside door. As the new jambs were tight, it became apparent that they would have to be very close to the wood behind the jambs. In fact it would need to be as tight as possible and I would need no shims. So, I decided to use screws rather than nail the jambs into position. There was either brick or an ibeam behind the wood was screwing the jambs to [ There are three layers looking from the doorway 1. door jamb 2. a 3/4" board, 3. brick or i-beam.] The screws thus needed to be less than 1 1/2 " or they would jack that wood away from the brick or the ibeam. I used 1 1/4" screws.

My real worry was that the screws would jack the jamb away from the wood behind the jamb and that would make the opening too narrow for the door. The screws I used would have left about 1/4" of thread in the jamb and I was concerned that would jack the jamb away from the wood, again narrowing the doorway. So I decided to file off the the last two threads of each screw. I did that, pre-drilled and countersunk the screws. It worked very well; everything is as tight as it needs to be, the door fits perfectly, one of my better projects.

So, the question is: Did I do well to file off those last two threads and prevent jacking or was I just being my occasionally compulsive self and wasting my time? Would the screws have just pulled through the last 1/4" of the jamb and pulled the jamb tight? Did I somehow reduce the effectiveness of the screw? [ Will my house fall down? :) ]

John Neel

[Robert Reece]

Why didn't you just drill a clearance hole in the jamb? That's what I do when I want to avoid jacking - I drill the pilot hole, then expand the pilot hole to a clearance hole in the top piece. Seems a lot faster than filing threads off.

[John Neel]

I confess, I drilled that too. But the wood is soft and I could see the screw head pulling through if I drilled so much that the threads didn't touch.

[Rob Wright]

I bought an assortment of the pro-max optimized thread length screws from Mcfeely's because I had a similar issue when hanging a door that was a little too tight and the first few standard screws from the BORG I drove did jack the material:

http://www.mcfeelys.com/product/0813-FPL/8-x-1-38quot-ProMax-Steel-Dry-Lube-Flat-Head-Screws

[John Neel]

Thank you, Rob. That makes me think that maybe a few minutes filing off threads was worthwhile given that I didn't have your selection of screws. Filing was faster than a trip to another hardware store in any case. When I go searching at different stores, they usually carry the same assortment of screws.