Making a Jack miter.

[Brice Burrell]

Well, some of you may not know what a jack miter is, this picture pretty much shows it all. It is used when trim or molding needs to butt together and still have the part or all of the profiles continue around.

I was putting together a bid for a trim job that required jack miters, so I needed to make a few test pieces so I would know how long it would take to make a jack miter. I thought I'd take a few photos to share with you. First, here is a drawing of the trim detail for the widows on this job.

I saw Gary Katz did a write up about making Jack miter on his site a year or two ago, so I thought that would be a good place to start. Here is a link to his Jack Miter page, but sure to check it out. He made a jig from wood, but I didn't want to spend time on making a jig so I used the MFS. Like Gary, I started by altering a chamfering bit, I removed the bearing and flatten the tip of the bit with a grinder. I used a guide bushing to ride on the inside of the MFS.

I marked the edges and then the center of the intersection.

What will be the center trim leg, it gets the corners clipped off on the miter saw.

With some careful measuring you can set the MFS to a rough width. Set the bit the approximate depth. Measure the offset of guide bushing to bit. The offset times two, plus the width of the trim leg, this will give you a place to start. Now set the 2 angle stops the same distance from the edge of the MFS.

Clamp the MFS down with the stops on the work piece, then clamp the work to edge of the table.

With everything in place the next step is to set the depth of the router bit. Carefully rout out the work piece, I used the find adjuster to creep up on the exact depth.

Once the depth is set, slowly nibble away the martial.

The two pieces should look like this.

Here is the end result, it took less time than I thought it would to have this joint turn out perfectly.

This is the short version, the jack miter is the first project in my new "How To" section on my site. For the whole story, How to make a Jack Miter.

 

[greg mann]

Bravo, Brice. The MFS seems to be one of those tools that baffle many as to how it can be applied. This is a great illustration of creative application.

 

[woodrat]

Beautiful craftsmanship.  You have a great deal of talent.

I looked at your "simple door" project and was very impressed.  Do you think you might put up the plans for the router base?

Thanks, Jeff

 

[Brice Burrell]

 Greg, when I first got the MFS I had no real idea of how I would adapt it for carpentry use. I knew my dislike for wooden jigs would get the wheels turning in my head. Seems everytime I make a jig from wood it doesn't really work perfectly for long. The MFS can be setup square without any trouble, never warps and best of all, when you're done, take it apart and use it on the next project.

 I have another job for the MFS very soon, a small staircase. I called the fabricator I have used in the past for stairs and they are back way up, they said maybe 6 weeks. The job can't wait 6 weeks and I remember seeing a picture in the Festool catalog of someone using the MFS to make stair stringers. Well the next project for my MFS.

 

[Brice Burrell]

Beautiful craftsmanship.  You have a great deal of talent.

I looked at your "simple door" project and was very impressed.  Do you think you might put up the plans for the router base?

Thanks, Jeff

Jeff, the router base is the Festool OF-FH routing aid (part #492037). I'll have a review for it on my site sometime soon. It is well made but a little pricey. I suppose you could make your own.

  And thanks for the complement.

 

[Matthew Schenker]

Brice,
Man, that's cool!  Makes me want to find a project where I can use that technique!  (Am I the only one who sees a technique and then designs a project around it, rather than the other way around?)

Thank you very much for explaining it, and for fulfilling the desires of the photographically needy.
Matthew

 

[Brice Burrell]

.....(Am I the only one who sees a technique and then designs a project around it, rather than the other way around?)....

Matthew

Matthew you are not alone, I do that too.  ;D

 

[Eli]

Excellent work.

Anything scientific about how much material you removed from the tip of the chamfer bit, or you just went for making the tip flat?

 

[Brice Burrell]

Excellent work.

Anything scientific about how much material you removed from the tip of the chamfer bit, or you just went for making the tip flat?

  No, I just made it flat, that too was easier than I thought it was going to be.

 

[Bill in seattle]

I remove the bearing from many bits and use collets with templates or edge guides to prevent bearing burn.

I have found a simple technique to remove the bearing post after removing the bearing is to use a drill bit slightly larger than the post with a drill(like a c12). drill slowly until you reach the base and then remove a little more to allow for chip clearances so it won't burn your workpiece. this has never seemed to ever affect the balance of  the bit or create vibrations.

 

[woodshopdemos]

Very nice work. Great use of MFS. Much better joint method than I use for that. Thanks for posting.
  By the way, CMT makes a number of 90? Vee-groove bits that would work if you dont like the idea of removing the bearing and flattening the end. They have beaarings but above the bit but are also available without.

 

[Brice Burrell]

Very nice work. Great use of MFS.

Thanks.

By the way, CMT makes a number of 90? Vee-groove bits that would work if you dont like the idea of removing the bearing and flattening the end. They have beaarings but above the bit but are also available without.

  John, using a v bit was my first idea, but the small point (at the tip of the v) would mean it would be time consuming to make the bottom of the notch flat. To make this joint fit properly the bottom needs to be perfect.

 

[Dave Ronyak]

Great job, Brice!!  Excellent tutorial.  I have not "succumbed" to an MFS - yet, but I do have two of those jack mitre joints in my house, for a pair of double hung windows positioned outside of a larger "picture" window.  I have to remove all of this mahogany trim in order to add insulation to the steel I-beams behind and to the surrounding brick foundation wall.  I just hope I don't screw up the trim when removing it because I cannot locate any wood that decently matches it.  The vertical members forming my jack mitre joints are ~7" wide and made from ~9/16" thick stock.  The top member is one continuous board ~12 feet long.  Now I know two people to contact if I get stuck during this future project - you and  Matthew!

Dave R.

 

[polarsea1]

I looked at that and "beaded face frame" popped into my head. Who needs a Morso?

Thanks for posting, you really are a craftsman.

 

[Dave Rudy]

Thanks Brice.  Excellent as always.

 

[woodshopdemos]

Very nice work. Great use of MFS.

Thanks.

  John, using a v bit was my first idea, but the small point (at the tip of the v) would mean it would be time consuming to make the bottom of the notch flat. To make this joint fit properly the bottom needs to be perfect.

Brice,
   Youa re dead right.  I found one other bit in my CMT drawer and will try it...and get back to you.

I like your alteration of the chamfer bit, I am always a bit squeemish about making any changes to a mfrs high speed bits.

 

[Brice Burrell]

Brice,
   Youa re dead right.  I found one other bit in my CMT drawer and will try it...and get back to you.

Yes, please do.

I like your alteration of the chamfer bit, I am always a bit squeemish about making any changes to a mfrs high speed bits.

I was a little worried, I started the router at the lowest speed and slowly worked my way up.

Dave and polar, thanks.

 

[Dave Ronyak]

Many of you may want to "slam" me for writing this, but I have an old set of 1/4" shank Craftsman bits that have removable screw-in rub bearings on the bottom of the bits.  There are three different diameterr of  rub bearings. Included in the set are 45 degree chamfer, 1/2" H rabbet, 1/4" and 3/8" quarter round and ogee.  Most are HSS but at least one is carbide tipped.  By simply removing the rub bearing, you can do what Brice has taught.  I have frequently used them with an edge guide to enable me to go inward from the edge of a workpiece farther than the diameter of the bit.  I don't know if Sears still offers them.

Dave R.

 

[Eli]

may want to "slam" me for writing this

Why? Because they're 1/4" shank or because they're from Sears? I don't have a problem with either. I am afraid to use 1/4" shanks on Australian hardwood though.

 

[Brice Burrell]

may want to "slam" me for writing this

Why? Because they're 1/4" shank or because they're from Sears? I don't have a problem with either. I am afraid to use 1/4" shanks on Australian hardwood though.

  I've never had a problem with 1/4" bits, no broken bits or less than satisfactory results because the shank was 1/4". Most of my "day to day" routing I do with 1/4" shank bits, and often with cheapo bits. Last year at the depot they had a 25 bit 1/4" shank set (I think Vermont) for $15 (USD) on clearance, so I pick a set up. I wish I'd bought another set or two, I seem to use those bits all the time with good (not great) results. Don't get me wrong, I own a ton of 1/2" shank bits. And I'm not suggesting you only use 1/4" bits, I'm saying they have their place.