# Routing Tenons on Curved Slats



## markristow (May 30, 2011)

Hi Guys, I am trying to build a curved bench. The struggle I am having is trying to cut the shoulders on the tenons accurately using machines. The problem is the slats are curved and hence everyone has a different radius. I try as far as possible to have a square piece of wood to cut the tenon on before I cut the curves, but this is not always possible and is a waste of wood. I have seen jigs that allow you to mount your wood vertically and then cut the tenon with a router, but they use a straight fence as a reference and to secure the piece, which is not possible with a curved piece. Any suggestions as I need to make many of these slats.


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## Phil P (Jul 25, 2010)

Hi Mark

As you say you'd normally cut the tenons _before_ bandsawing the curve, a task which I assume would require at least 5 jigs, one for each radius. One thing which strikes me is that in many ways this would be an ideal task for a Domino (or for that matter a slot mortiser), but man are those Festools expensive. So, have you considered making up a jig to hold all 5 pieces in their finished positions and then routing the tenons _en bloc_ with a hand-held router, one side at at time, flipping the pieces end to end to cut the other side of the tenon? In saying that I'm assuming the then ends are identical, are they? That still leaves the ends of the tenons to be sorted out (ro malke the narrow end shoulders), but I assume that you'd be able to use your bandsaw or a jigsaw to handle that part of the operation - marking those out would require a simple rebated marking block IMHO

Regards

Phil


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## mdowning (Oct 12, 2012)

Phil P said:


> Hi Mark
> 
> As you say you'd normally cut the tenons _before_ bandsawing the curve, a task which I assume would require at least 5 jigs, one for each radius. One thing which strikes me is that in many ways this would be an ideal task for a Domino (or for that matter a slot mortiser), but man are those Festools expensive. So, have you considered making up a jig to hold all 5 pieces in their finished positions and then routing the tenons _en bloc_ with a hand-held router, one side at at time, flipping the pieces end to end to cut the other side of the tenon? In saying that I'm assuming the then ends are identical, are they? That still leaves the ends of the tenons to be sorted out (ro malke the narrow end shoulders), but I assume that you'd be able to use your bandsaw or a jigsaw to handle that part of the operation - marking those out would require a simple rebated marking block IMHO
> 
> ...


Hi Mark
Would it be easier to use loose tenons in this situation?

Cheers

Michael


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## MasterSplinter1 (Jan 27, 2013)

I havent dont it before but loking at the piece cant you mount it vertical like you said. There is still a flat area where the edge board meets. let that ride on the table.


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## billg71 (Mar 25, 2011)

If the parts are bandsawn you can save the off cuts and use them to register the piece against a fence or miter gauge.

HTH,
Bill


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## markristow (May 30, 2011)

Thanks for your input. I cut a few pieces from one piece of 230mm wide wood, so the off cuts don't have a straight edge. The tenons in the photos were cut with the band saw. The reason for the gaps is the error in transfering the shoulder line around the wood, as I need to see it on all sides to cut carefully. I have been considering mounting the slats vertically in a jig using clamps and only one shoulder line to get the correct angle, this will solve the problem of transfering the lines all around, which takes a bit of time. The jig will then have a horizontal table with a hole which my guide bushing will follow to route the tenon out. Problem is if my guide is not held tightly to the perimeter of the hole, then my tenon will not be accurate. By cutting into the end grain will there be some sort of torque pulling the router to the centre and causing the problems?


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## billg71 (Mar 25, 2011)

markristow said:


> ******* I have been considering mounting the slats vertically in a jig using clamps and only one shoulder line to get the correct angle, this will solve the problem of transfering the lines all around, which takes a bit of time. The jig will then have a horizontal table with a hole which my guide bushing will follow to route the tenon out. _Problem is if my guide is not held tightly to the perimeter of the hole, then my tenon will not be accurate._ By cutting into the end grain will there be some sort of torque pulling the router to the centre and causing the problems?


Right idea, a T-jig with a platform,, cut from the square end of the piece.

To get around the problem of control, make the hole in the top of the jig big enough for the whole workpiece and a generous clearance for the bit, notch the upright and use a long rabbeting bit to reference the tenon off the face of the workpiece. That way you can stage cuts by depth and not have to risk spoiling the work if you don't keep a bushing hard against the template. The short shoulder on the inside of the radius won't be as deep as on the outside because of the way the bearing rides but that shouldn't make much difference and you can either trim to match or adjust your mortices.

Check out Pat Warner's(Quillman here on the forum) _The Router Book_ on pages 134-135 for a quick description and a photo. Or his _Fast, Easy and Accurate Router Jigs_, Chapter 9 is devoted to constructing and using the jig.

HTH,
Bill


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## markristow (May 30, 2011)

Hi Guys

This is the jig I made. It holds the piece in a vertical orientation with the fixed clamp. I use a second clamp once everything is in place to secure the wood. The piece is level with the top of the table and hence the depth of my tenon is governed by the depth of cut of my router. I have since ordered a 16mm x 50mm depth bit as I will only be using this jig in the future to make tenons. To start I mark the tenon on the face only as the depth will be set by my router. If I am making more than one tenon of the same size I only have to mark one and set the jig up. I then set the fences using a gauge to the marks. The gauge is dependent on the size of the bit you are using and the diameter of your router base. Once you have made the gauge it is easy to set the jig up. To cut the tenon I keep the router base firmly against the fences and do a full 360 degree cut. It takes about 15 sec to do a cut. I can cut a 20mm depth in one cut. For the curved pieces it is quite easy as the end of the tenon is set level with the top of the jig, regardless of the shape of the piece. The router rides on the tenon face and on the top of the jig, so it is well balanced. The only problem I have is the dust is very fibre like and tends to collect very tightly in the cutting area. I will try sort this out by connecting a vacuum cleaner to the router. Thanks for all your input.


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## Cherryville Chuck (Sep 28, 2010)

Mark, if the ends of your boards are cut at the correct angle then all you have to do is set the end down flat on your router table and clamp it to a board that will slide along the top of your fence. That will hold it in the correct position while you rout one side of the tenon. You'll have to be careful when you flip the piece to the opposite face to make sure the end is still flat on the table.


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## Taco (Mar 5, 2013)

Charles, you can keep beating yourself in the head but two people have given you the answer. A loose tenon is the way to solve this. With a $30 beadlock I could done all the tenons in less time than you've taken to type these posts. 

Not trying to be harsh, just saying.


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## Cherryville Chuck (Sep 28, 2010)

Taco said:


> Charles, you can keep beating yourself in the head but two people have given you the answer. A loose tenon is the way to solve this. With a $30 beadlock I could done all the tenons in less time than you've taken to type these posts.
> 
> Not trying to be harsh, just saying.


Whatever method Mark chose to do them, they are probably done by now as that was 2 weeks ago.


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