Tips on trimming window jambs with hand planer?

[peter berglin]

All 4 sides of the window jambs need to have about an 1/8 of an inch taken off. I have a small stanley standard block plane and then i have a jointer plane around 18".

Which one(s) should I use? Order?
How do I handle corners where you are going with grain and against grain in order to avoid tear out?

Tom silva from this old house said that putting a slight bevel in the jambs as you plane improves results. What direction is this bevel?
Higher on glass side down to Lower on Drywall side
or
Lower on glass side up to Higher on drywall side?

Any help / suggestions would be greatly appreciated

ty

[Jonathan McCullough]

It's hard to know how to advise without seeing the thing. I'd recommend you pick up a copy of "Working Windows" by Terry Meany.

[Jim Koepke]

Howdy Peter,

Welcome to the creek.

Sometimes a picture helps with this kind of question.

My experience with doing window frames is limited. One thing that may help with your problem is to consider which way you want the water to flow if this is a window for a house.

To avoid tear out on end grain the plane can be worked from the outside toward the center of the piece. Other times it helps to put a slight chamfer along the edge you are planing toward.

On the bottom of the outside of a window jamb I put a grove about a half an inch in from the edge to prevent water from creeping or being blown up the sill.

Maybe someone who knows more will answer.

jim

[Jeff Burks]

I'm going to assume you are asking about real wood jambs.. and seeing how I am a carpenter....

You really don't need to bevel a window jamb. The bevel is used for the same reason machine cut casing is often relief cut on the back side. It ensures that small lumps and bumps don't interfere with a tight casing-to-jamb fit. In fact some casing is also beveled on the underside of the edge that gets nailed to the jamb. A lot of the big window factories ship extension jambs with beveled edges. If you are going to bevel a jamb it is much better to do it before you install it. The amount should not be more than 1° or 2° out of square. EDIT: In your terms the bevel would be "Higher on glass side down to Lower on Drywall side". The improved result is tight contact between jamb and casing. That is essential for stain grade work, and limits need for wide caulking beads in painted work.

The sole of a metal plane can leave smudge marks on the drywall or painted surface so try not to allow the plane sole to extend beyond the area that will be covered by the casing. Don't use a jointer plane for this kind of operation, a block plane is far more suitable. The jointer plane will not let you follow the contour of a crowned stud wall. It will also wreck the wall surface and leave you with silly putty for arms. Talk about a work out!

Clean and wax the bottom of the plane before you begin. Skew the block plane about 30° out of parallel with the jamb (nose points into the window, tail hangs out over the drywall) and let the tail end of the plane ride on the drywall for the last few passes. Push the plane with your right hand while gripping the plane with your left hand. Left hand thumb is on top, and fingers below (behind the mouth) riding on the jamb to act as a fence. It's much better to practice turning the corners in a continuous cut (like driving around the city block) then it is to make through cuts and risk mashing your fingers or spelching the adjacent jamb member as you exit your cut. A super sharp cutter will usually negate the grain direction change at the jamb intersections. If you are having trouble with tearout then turn the corner with the plane at the intersection and only cut about 1/8" onto the adjacent jamb member. Stop the cut and come in from the other side doing the same thing when you reach the corner.

If you have a lot of material to take off on other jambs (1/4" or more), then it might be a good idea to plane or chisel a trench at the corners of the jamb so that you can use an aggressive through cut with your (scrub) plane while minimizing the risk of spelching until you get close to the final surface.

Keep in mind that drywall gypsum is very abrasive. If you dig into the drywall with the cutter it will dull very quickly. Same goes for getting gypsum dust in the mouth of the plane while you are working. If the jamb is primed/painted, or made from engineered material then you will be getting a lot of practice on the sharpening stones. Sometimes there is nothing you can do about it when the job has to get done. For this reason I prefer to carry extra cutters in my tool kit for this kind of site work. Always keep them razor sharp and ready for work. Bring the box of tools to be sharpened home a couple times a month where you can put a new edge on them in a more controlled environment.

[Bruce Haugen]

"Higher on glass side down to Lower on Drywall side"

Try this: lay a piece of trim on the window jamb and look where the gap is. Plane off whatever is keeping that trim from contacting the jamb. It's the part closest to the drywall. It used to be that window jambs were delivered with that slight chamfer on them. Door jambs, too.

I'd do it with a block plane, since it's a whole lot easier to maneuver with the window in place.

[Paul Incognito]

I'm assuming you're talking about interior extension jambs. If not, disregard these instructions and clarify your question.
Are they attached to the window? If not, I find it's easier to take them to the table saw and rip them to the width you need. You can leave them about 1/16" wide and bevel them about 5 degrees towards the sheetrock. The idea is to have the casing lie flat on the sr, and the bevel covers any imperfections.
If they are attached, take your block plane and lay it on the edge of the extension jamb, on an angle so it's riding on the sr. This will give you the bevel you need.
Either way you do it, be careful not to take too much off, or you'll have gaps between the casing and ext jamb. If you're painting you don't need to be as careful, you can caulk any gaps. If you're staining and end up with gaps you're sol.
Another way I do this is to assemble the casing on the floor. Cut it to length, glue the corners and pin them with brads. Be careful to not glue/nail the casing to the floor. Let the glue set up 15-30 minutes, then pick up the assembled casing and attach it to the extension jambs with brads. Put some shims between the sr and the casing so that nailing it won't open the miters and attach it to the studs with 2" nails. Caulk the joint.
It probably took longer to read this than it will take to do the work.
Hope this helps,
PI

[peter berglin]

I really appreciate all your responses, I found them helpful. Sorry forgot to mention interior and I will be painting/caulking so it should be easier.

Great community here.

[Larry Edgerton]

I'm going to assume you are asking about real wood jambs.. and seeing how I am a carpenter....

You really don't need to bevel a window jamb. The bevel is used for the same reason machine cut casing is often relief cut on the back side. It ensures that small lumps and bumps don't interfere with a tight casing-to-jamb fit. In fact some casing is also beveled on the underside of the edge that gets nailed to the jamb. A lot of the big window factories ship extension jambs with beveled edges. If you are going to bevel a jamb it is much better to do it before you install it. The amount should not be more than 1° or 2° out of square. EDIT: In your terms the bevel would be "Higher on glass side down to Lower on Drywall side". The improved result is tight contact between jamb and casing. That is essential for stain grade work, and limits need for wide caulking beads in painted work.

The sole of a metal plane can leave smudge marks on the drywall or painted surface so try not to allow the plane sole to extend beyond the area that will be covered by the casing. Don't use a jointer plane for this kind of operation, a block plane is far more suitable. The jointer plane will not let you follow the contour of a crowned stud wall. It will also wreck the wall surface and leave you with silly putty for arms. Talk about a work out!

Clean and wax the bottom of the plane before you begin. Skew the block plane about 30° out of parallel with the jamb (nose points into the window, tail hangs out over the drywall) and let the tail end of the plane ride on the drywall for the last few passes. Push the plane with your right hand while gripping the plane with your left hand. Left hand thumb is on top, and fingers below (behind the mouth) riding on the jamb to act as a fence. It's much better to practice turning the corners in a continuous cut (like driving around the city block) then it is to make through cuts and risk mashing your fingers or spelching the adjacent jamb member as you exit your cut. A super sharp cutter will usually negate the grain direction change at the jamb intersections. If you are having trouble with tearout then turn the corner with the plane at the intersection and only cut about 1/8" onto the adjacent jamb member. Stop the cut and come in from the other side doing the same thing when you reach the corner.

If you have a lot of material to take off on other jambs (1/4" or more), then it might be a good idea to plane or chisel a trench at the corners of the jamb so that you can use an aggressive through cut with your (scrub) plane while minimizing the risk of spelching until you get close to the final surface.

Keep in mind that drywall gypsum is very abrasive. If you dig into the drywall with the cutter it will dull very quickly. Same goes for getting gypsum dust in the mouth of the plane while you are working. If the jamb is primed/painted, or made from engineered material then you will be getting a lot of practice on the sharpening stones. Sometimes there is nothing you can do about it when the job has to get done. For this reason I prefer to carry extra cutters in my tool kit for this kind of site work. Always keep them razor sharp and ready for work. Bring the box of tools to be sharpened home a couple times a month where you can put a new edge on them in a more controlled environment.

Been doing this for over 30 years and I would say this is a perfect response!

The only thing I would add is that drywall is a corrosive, and also will attract moisture, so at the end of the day take your blow gun and blow all of the plane parts clean, individually. If you don't take it apart to clean it drywall dust will be between the parts and rust will start where it can't be seen. I use Top-coat on mine every day when doing this operation.