# taper jig for long window jamb extensions?



## lynch (Aug 10, 2008)

Hi, everybody.
This is my 1st post here. I have been doing carpentry for over 30 years but I'm always looking for new ideas.

Has anyone ever come up with an idea for a taper jig that will work with longer pieces of window jamb stock, like 60" or more? I don't have a home shop (so no place to plan out a proper jig) and I use a piece of plywood and screw the jamb piece to plywood to get the taper I need. This does the job but leaves holes to fill and takes time to set up.

The reason I need to cut window jamb extensions on a taper is that my company has been using the Tyvek window wrap system and it leaves the window out a little bit farther on the bottom than the top, thus creating the need for a tapered jamb ext.

I have seen some good shop-built jigs on the web but they are mostly for table legs and furniture pieces.

I welcome any ideas and will share any I come up with.

TIA
lynch


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## grumpycarp (Feb 23, 2008)

If you have a jointer on site then I could provide for you a pretty simple method, providing that it is a CONSTANT taper. No jig required, just a little simple math. I'm a finish carp and will gladly share my method with you offline. IM me

BTW, how big are your jambs and how far out are they? My experience has been that it is about 1/4 give or take, due the two extra layers of bituthene.


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## joey (Sep 17, 2007)

As a trim carpenter and a cabinetmaker I have ran into this alot I use to just scribe the extension and either block plane it or cut it then block planing it smooth. both took alot of time. about three years ago I did a McManision that it seemed every window extension needed cut on a taper, so I made a jig using a 8' piece of MDF I cut four slots, but T track would work also. The slots was to adjust the fence. I put about four screw on hold down clamps on the fence to hold the extensions then I used my router with a 1/2" bearing bit to trim the extensions. this worked pretty quick after some adjustments. I would scribe the line on the extension, set it flush with straight edge of the MDF, adjust the fence to it, tighten it down with wing nuts then engage the hold downs. and route. I had deep extension so I didn't hit the hold downs it would be a problem on narrow cut, But It was my prototype if I build another I would use a T Track in the fence with the hold downs so they can be moved around to stay out of the routers way. hope this at lease sparks an idea

Joey
http://sleepydogwoodworking.blogspot.com/


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## lynch (Aug 10, 2008)

I use my router table as a jointer.
We almost exclusively use Anderson double-hung windows with 2×6 exterior walls so the ext. jambs are 2" on average with, as you say, a difference up to a 1/4", depending on who prepped the rough opening and installed the window.
IM you? Where? How? Dont do a lot of IM'ing. Don't they have private messaging here?
I would like to hear how you do those tapers with the jointer, though.
Thanks for the reply.
lynch


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## lynch (Aug 10, 2008)

Thanks for the idea, joey. One idea I had was using birch plywood for my base with either hold-down or toggle clamps. I would rip the PW to a width that would handle the jamb size plus leave room and clearance for the clamps. I would leave the table saw's fence at the same setting as my rip. I could then mark each end of my jamb stock and line the marks up with the ripped edge of the plywood base and clamp the jamb in place. Then I could just run the whole thing trough the saw and hopefully have my tapered jamb without screw holes. 
lynch


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## grumpycarp (Feb 23, 2008)

lynch, (and all)

For a while I was convinced I had "invented" this technique but last summer I ran across this video on pop woodworking and it demonstrates the technique of tapering on a jointer faster than I could type an explanation. Like a lot of folks out there I have "invented" my own techniques only to find out later that someone wrote about it a hundred or more years ago and they were merely passing along an age old technique then . . .

The tools might be 'lectrical now but the need and solution remain the same. I also use this technique to whip up clamping cauls on the job for various tasks. Just use push sticks and don't try to take too big a bite at any time. Instead of doing it in halves do it in quarters, eights etc. Also you should leave enough meat for a final light clean up pass. I'm actually surprised that Mr. Huey didn't get spectacular blowout while filming this video.

A couple of experiential observations on the technique:
1. Only works well on a jointer with a long infeed table. If the taper needs to be longer than the total you can rest on the infeed side it won't work as demonstrated. There are work arounds, such as using the jointer to hog off the material and then sneaking up on your target. This would probably be easier on the table saw but it is a free hand cut and is not recommended to anyone. The potential for kick back if done incorrectly is gianormous.

2. Make the pass(es) in the reverse of what is shown. This is essentially climb cutting on the jointer. You will be left with a cleaner cut as you are not lifting the grain of the wood.

best regards,

http://fw_woodworking.permissiontv.com/index.html?showid=115402


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## croessler (Jun 22, 2007)

Very cool vid… If a little scary….


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## grumpycarp (Feb 23, 2008)

I should have said in the above #2. comment to make the FINISHING PASSES in the reverse of what is shown. Otherwise proceed (if you dare) as shown.


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## oldworld124 (Mar 2, 2008)

Another and more portable way to do long tapers is with a long Tru-Grip type guide clamp. I have a set of the professional series in 2', 4', and 8'. They come in very handy on the job site or in the shop. 
To do a long taper I just put a small wedge or shim under the clamp ends to give them complete support. This way they won't slip out of place. You can then use a router, attached to a base that rests in the groove of the guide. You can also use a skill saw and follow the edge of the guide. Or both, saw first followed by a router to clean up the edge.


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