Rabbeting Exterior Doors for Compression-Bulb Weatherstripping

Advice on how to cut clean slots for weatherstripping in door jambs. May 5, 2007

Question
I am currently building a few custom exterior doors. I am wondering how everyone else creates the rabbet for compression bulb weatherstrip. Do you glue the rabbetted stop to the jamb, or does someone make a router bit to plow it into a solid jamb with the stop machined in?

Forum Responses
(Architectural Woodworking Forum)
From contributor A:
Use a good sawblade and cut the rabbet and the slot for weatherstrip. With a sharp blade there really isn't much sanding.

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From contributor G:
I take the rabbet for the door to go in out of the jamb with a 2.24" wide rabbetting head on my shaper. With a slow feed rate it takes a 2" x .5" rabbet out in one pass, even in the hardwoods (no sanding at all). Then I use a router bit from Resource Conservation Technology, 4103661146. It has the bearing beneath the cutter and a minimal nut on top so you can get to the 1/2" stop. You have to call them, as they never used to have a web site. I used to put the slot in just before I screwed the frame together as the shoulders of the slot would blow out easily when I was making the joints if I slotted first.

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From contributor J:
This only works if one of your table saws has the right width blade to create a slot that the strip fits properly. Mill your jambs complete with the rabbet. Finish by setting the table saw blade height to the depth of cut needed when feeding the stock through on edge with the rabbet edge down on the table, and the back of the jamb against the rip fence. This works with right or left tilting saws - just set the fence on the side towards which the blade tilts.

The trick is to tilt the saw about three degrees so the blade won't mar your rabbet face. Some fence adjustment will place the kerf right where you need it. I got this by looking at factory jambs. The insulation bead goes in fine, with no ill effect from the angled slot.

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From contributor C:
Jamie said “I am currently building a few custom exterior doors.” That is the challenge for the custom millwork/door shop. Exterior door jobs are usually small quantities and many times only one unit. We’ve tried all the methods listed above and a few more. It has been a process of ongoing improvement and irritation to produce a small quantity of jambs efficiently with little cleanup required. Lately the rage in modern architecture is thick 1 ½” rebated interior door jambs without casings. The jamb becomes the trim and has to be furniture quality with the corners sometimes mitered. At least with an interior job you have more quantity to work with.

Our butt hinged exterior doors are usually 2 ¼” thick requiring a 2 ½” X 9/16” rebate. The present method is to cut the end rebate with a sliding table shaper. The long rebate is cut with a 250mm diameter Garniga rebate cutter with chamfering insert knives easing the top surface edge and a 3mm insert groover making the gasket groove. We still have to do the lower edge ease in another pass or by hand. The material is fed face up flat on the table with the cutter on top. We have a 13 HP shaper and would recommend at least 10 HP for a cutter like this. We have molder knives for this also but the end cut after is a problem setup. The shaper is faster for small quantities.

For smaller shapers, using a rebate cutter with the jamb on edge works better than saw or dado cuts. It’s a little harder to match to the top rebate with this method. The feeder has to be tilted and you still have to put the gasket groove in with another step. A 10” saw blade in a shaper is easier than the table saw or router for the groove. Tilted a little as contributor J describes or held up .5mm. I would be interested how shops totally machining exterior doors on CNC routers approach this problem.