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Shortening Prehung Doors

vbjohnc | Posted in Construction Techniques on February 25, 2003 07:35am

Anyone have any great tips for shortening the molded MDO prehung doors you get at Home Depot or Lowes? I need to bring down  80″ doors about 2 inches for a basement install. It needs to accomodate a suspended ceiling.

I’ve thought about cutting the jambs at the bottom and just taking a circular saw to the door. Haven’t thought about how to back support it yet so that I don’t chip the door surface.

Would appreciate any help!

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Replies

  1. User avater
    JeffBuck | Feb 25, 2003 07:55am | #1

    first..check and see how much ya can take off the bottom alone.

    You'll get close to a full inch from the jamb legs alone..so I'd guess from here you'll be ok.

    Cutting the door method....

    pick the show side and put that face down.

    mark the cut. measure the saw base edge to blade edge to find where to put the straight edge. Clamp it.....(or as we say round these parts....Jed'it....)

    Now.....here's the trick part...

    set the circular saw to 1/2 tooth depth...about 1/8th inch.

    set the saw way across the far side of the door....hold on with both hands...the safety police will saw this is dangerous...and lift the blade guard up and out of the way...

    Get the pic...you're about to score thru the door...making the cut backwards...drawing the saw towards yourself....which....can be dangerous.

    Slowly..steadliy......safely.....pull towards ya and make the score cut.

    Now..the beauty of it all.....don't touch the straight edge...

    Just set the saw to full depth..and puch the cut thru the door..along the straight edge..as ya would do normally.

    With a nice sharp many toothed blade......good quality too.....you now have a nice clean cut...no splintering. Sometimes...with a door I'm worried might split at the egde....I'll buzz the near edge with the short blade a coupla inches first..then run back towards and thru that cut.

    Very quick work..especially if U have more than one door to cut.

    I've done this thru everything from hollow care to MDF to solid mahogany and such.

    Has worked well for me ever since I stole the idea from somewhere.

    Jeff

    Buck Construction   Pittsburgh,PA

     Fine Carpentery.....While U Waite                  

    1. nino | Feb 25, 2003 08:16am | #2

      Whoa there a minute! Why risk yourself running a circular saw backwards? What I do when I cut doors is I make a mark where the cut should be. I then clamp a straight edge along the mark and score along the straight edge with a sharp utility knife. I then reposition the straight edge so that the blade cuts just below the score line all the way through the door. A little light sanding to relieve the edge and you're done, all safe and sound.

      1. designbing | Feb 25, 2003 06:47pm | #3

        While the razor knife works, I just took some scrape 3/8" plywood and ran it though my table saw paralell to one factory edge.  Now with two pieces; one approx 3x48 and the other 10x48, I screwed the narrow piece on top of the wide piece and ran my circular saw down the length.  Now I just mark the door where I want the cuts to be clamp my "shoot board" on top and cut.

        Bing

        1. MikeSmith | Feb 26, 2003 04:17am | #10

          we always use a "shooter board" too, we make ours out of 1/4" luan... each guy has his own , since no two saw bases are the same....

          save the door bottom and glue the old plug back into the door ..  a two inch cut will usually take the plug with itMike Smith Rhode Island : Design / Build / Repair / Restore

      2. User avater
        JeffBuck | Feb 26, 2003 01:49am | #7

        why risk?

        well........because there's lots more dangerous out there than a circular saw set at 1/2 tooth being pulled towards ya with both hands!

        As a matter a fact.....the real reason behind both hands is to keep it nice and tight against the fence...

        if a saw set at 1/2 tooth is scary to ya when it's slowly pulled backwards.....I'd find a new line of work. ......especially if ya have a truck load of doors sitting there waiting to be cut down.

        Jeff

        Buck Construction   Pittsburgh,PA

         Fine Carpentery.....While U Waite                  

        1. Snort | Feb 26, 2003 02:12am | #8

          We cut plywood veenered doors all the time to clear carpet or tile. When I have a "truckload of doors" I don't want to have to cut them all twice.

          Just clamp a zero clearance shooting board on the door, run a sharp utility knife along the guide, and also down the edge of a square on the side of the door the saw will exit. Eliminates blowout. One pass is all it takes. Bevel the edges with a sanding stick, and on to the next door...don't know if you need to cut down the jambs or not, anyway, that's another chapter...

          PS if you end up cuttin into the hollow part of a hollow core door bottom, it's not real hard to fill it in. EliphIno!

          1. User avater
            Qtrmeg | Feb 26, 2003 02:19am | #9

            Yep, didn't wanna get too technical, it is just a cutting doors thing...

    2. don26299 | Apr 22, 2003 06:33am | #20

      Hey Jeff,

      I just tried your great trick last week cutting down a door. (This is the one where you set the circular saw 1/8 below the shooting board and bring the saw toward you (stiff arm like). I went back to the archives to find this and just want to thank you for the tip. It worked great! At that depth and with a Marathon blade I saw no more danger than cutting anything with a circular saw. Thanks!

      Fonzie

      1. User avater
        JeffBuck | Apr 23, 2003 01:37am | #22

        every now and again I have a good idea....

        even if I stole it somewhere along the ways.

        Jeff

        best door trick yet is the stabila door jamber set....with the 7' mag level.

        those little magnets really speed up a one man team. fills the whole jamb to spot any bows too. I use it more than my 4'er anymore. laying tile..setting cabs....

        Buck Construction   Pittsburgh,PA

         Fine Carpentery.....While U Waite                  

        1. don26299 | Apr 23, 2003 06:33am | #23

          Ok Jeff, what are you talking about with magnets and jambs? I haven't been reading my tool catalogs lately. Is that a sign of getting old?

          Fonzie

          1. User avater
            JeffBuck | Apr 24, 2003 03:03am | #24

            Tool crib has it....

            woodworkers wharehouse keeps a few in stock too.

            It's the Stabila door hanging set...think they call it the Jamber Set....something like that.

            it's a slightly less the 7'er and a 32" level set.

            They have them with and with out magnets.

            The magnets are speced so they'll "usually" grab enough of a standard prehungs hinge leaves that'll it'll stick there as you set the door.

            I forget what it cost.....remember it was a bit pricy....but I highly recommend it.

            Maybe try a search at amazon and look thru the Stabila stuff.

            I got the case with it too..and that had a slot that fit the 4'er I already had.

            Now I carry all 3 levels thru the site in one long bright yellow case....homeowners ask if it's either a telescope or a bazooka.

            One guy had the best idea....said it looked like I was going fly fishing in his basement.

            JeffBuck Construction   Pittsburgh,PA

             Fine Carpentery.....While U Waite                  

          2. CAGIV | Apr 24, 2003 03:07am | #25

            At the local lumber yard, jamb set 159.99 kansasView ImageGo Jayhawks..............Next Year and daaa. Blues View Image

          3. don26299 | Apr 24, 2003 05:05am | #26

            Thanks Jeff, I'll check it out.

          4. MisterT | Apr 24, 2003 05:09am | #27

            Jeff,

            I did not realize that the magnets would be of any help on a wood jamb!

            well golly gee sargent carter.

            I learned something today, I'm going to bed!

            Mr T

            Do not try this at home!

            I am an Experienced Professional!

          5. User avater
            jonblakemore | Apr 24, 2003 07:46am | #28

            I realized that right after I bought my 78" level w/o magnets...

            Anybody want to buy an almost new Stabila? 

            Jon Blakemore

          6. CAGIV | Apr 24, 2003 08:20am | #29

            sure I'll buy um lol, I almost buy a set everytime I am in the store, but for some reason the impulse leaves me when the thought of parting with 160 bucks comes to mind.

            oh well one day I'll go through with it.

            View ImageGo Jayhawks..............Next Year and daaa. Blues View Image

          7. User avater
            IMERC | Apr 24, 2003 09:40am | #30

            OUCH!

    3. CAGIV | Apr 22, 2003 06:45am | #21

      damn skippy idea.View ImageGo Jayhawks..............Next Year and daaa. Blues View Image

  2. User avater
    Qtrmeg | Feb 25, 2003 06:50pm | #4

    I would order the doors from a millwork supplier and have them within days. 6-6 doors are more or less off the rack, but they will setup any size you want.

    You can cut them assembled. Door down, cut the bottom of the jamb/casing. Flip the door assembly over cut the jamb/casing, and finish with a handsaw. Now open then door and support it's outside edge, and score the door just above your finish cut, as Nino said.  Clamp a straight edge and finish cut the door. Sand a bit, voila.

    Be sure to use a sidewinder. ;-)



    Edited 2/25/2003 10:52:47 AM ET by Qtrmeg

    1. Steve1 | Feb 25, 2003 07:00pm | #5

      i have cut many doors down both in height and width, one job sticks out, 42 prehung solid core prefinished ok veneer fronts. had to cut both width(about 1/4 inch and height (about  1 inch) to fit already installed steel door frames.

      The width i cut the hinge side and re mortised, the height off the bottom.

      For a perfect cut, i used a straight edge, brand new top quality blade(Freud) in a well tuned skill saw(not skill actually)

      The long cut was easy with the grain, height cut i prescoredwithe saw set at the thickness of the veneer or less then re cut all the way through.  Everyone came out perfectly.

      1. Redfly | Feb 25, 2003 07:41pm | #6

        As a favor for an old client, I once cut down all their beautiful oak doors after a thicker carpet was installed.  We were just getting ready to leave for a vacation, so I was really in a hurry.  Oak doors & hurry don't really mix very well, and I was on the last of 12 doors, just finishing the cut when I realized I had cut the TOP.  Yikes!  I carefully retrieved the cut-off, glued and clamped it back on, touched up the stain and hey, good as new.  Fortunately, I had used a very fine blade and the doors were quarter-sawn oak, so there was virtually no splintering and I was able to make my vacation.  I did offer to replace the door, but since they could not even tell the door had been mis-cut, they graciously declined.

        As for cutting lots of doors, my technique is to put several strips of blue 3M tape along the bottom edge wide enough to cover the shoe of the saw, and then, using a straightedge and sharp utility knife, I score the cut line and peel off the lower section of tape, which gives a nice sharp line to follow with the saw.  The tape also seems to help keep the wood from splintering as well as protecting the surface of the door.  I freehand the cut, using the tape edge as a guide.  I stop the cut about 1/2" from the opposite side and move the saw to that edge to complete the cut - this prevents the wood from splintering out as the blade exits the cut.  I've cut hundreds of doors using this method and, other than the above-mentioned incident, have never had a problem. 

  3. migraine | Feb 26, 2003 04:46am | #11

    You guys are scaring me!!  I've cut/hung too many doors and haven't lost one yet! (door or finger).  Let me try to articulate this as best as possible:

    Make Jig:  cut your self a piece of 1/4" ply wood 6"x36"-40", cut another strip to 3/8" thick x1 1/2" wide x 36"-40" long.  glue and/or nail that thin strip to one long edge of the plywood.  when the gue has dried, run the out side edge of the saw guide on top of the 1/4" plywodod and against the 3/8" thick piece of wood.  Now run your saw up the plywood and you wil wind up cutting off some of the 1/4" plywood.  This then tells you exactly where your saw will be cutting when you clamp this jig to the door

    Make you door where you need to cut it off and clamp this jig to those marks.  take a utility knife and run the knife edge dowm the lenght of the edge where the saw will be cutting.  This knife line will keep the top edge of the door from chipping(hopefully) and the other side will be perfect.  You can try to hold the razor knife at an angle so that this scored edge will be slightly in from the saw cut line

    This works on masonite doors to oak to mahogany and you will be amazed how handy this jig will come in later.  If you still can't figyre this out, email me [email protected] and I will try to draw a picture, scan it, and then email it to you

  4. skipj | Feb 26, 2003 05:10am | #12

    VB,

    If your concern is chipping the door surface, I recommend the following:

    1. Good panel blade.

    2. Comfortable straight edge set up. (Everybody seems different on this.)

    3. Lay down blue tape and cut through it.

    It works for me, which is more than some of my guys can say.

    skipj

    1. vbjohnc | Feb 26, 2003 09:15am | #13

      Thanks all. So everyone recommends cutting it at the bottom? So if I need two inches, not an inch on top and an inch on the bottom? I'm concerned about the door handle being on the same height as the rest of the doors.

      Realize that if I cut on top that I need to re-dado the jambs.

      1. calvin | Feb 26, 2003 03:17pm | #14

        VB, if you go that route, by the slabs and hang to your own jambs.  You save nothing if you are going to recut the hinge and latch.  __________________________________________

        Remodeling Contractor just outside the Glass City.

        http://www.quittintime.com/

      2. mike4244 | Feb 26, 2003 07:57pm | #15

        Cut the 2" from the bottom using Jeff Buck's method, and mine. Clamp straight edge , set blade for 1/8" and pull the saw backwards. This scores the door, then raise the saw base for full cut and push as usual. Replace door bottom with a new piece of wood.Glue up both sides of new piece , install and clamp.Put a screw about 1/4" deep in each side of new piece so you can adjust the wood flush with the skin.After clamping you remove screws.If you skip this last step you will be sorry, I was on the first door I cut down. I pushed the wood in to far and struggled to get it flush.

        This method of scoring and cutting works for veneered, laminate and solid wood doors.No tape, no knife, works perfect every time.I have cut at least 2000 doors this way for the last 41 years.

        1. User avater
          JeffBuck | Feb 26, 2003 11:27pm | #16

          so yer the guy I stole that idea from....

          JeffBuck Construction   Pittsburgh,PA

           Fine Carpentery.....While U Waite                  

          1. User avater
            RichBeckman | Feb 27, 2003 12:10am | #17

            "so yer the guy I stole that idea from...."

            Buck may be an occasional thief, but at least he's an honest one!

            Rich Beckman

            Another day, another tool.

          2. User avater
            JeffBuck | Feb 27, 2003 01:37am | #18

            Hey Rich...

            "How much....."

            ahh.......you know the rest......

            JeffBuck Construction   Pittsburgh,PA

             Fine Carpentery.....While U Waite                  

          3. mike4244 | Feb 28, 2003 06:19am | #19

            Jeff, back in the seventies I had a job where 250 or so plastic laminate doors were to be hung. About half of these doors had to be cut for height. The frames were set correctly, then terrazzo floors were installed instead of vinyl tile. This change mean't  a lot of extra work for us. After cutting the first door down with a router, I knew there had to be a better way.Hence, this method came to mind.

            Mike

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