Making a Jack miter.

[Eli]

I only had 1/4" in the US. I've never had one break, but I read one account of a cheaper import 1/4" bit tearing off the shank and going for a trip around someone's shop and decided reading about it was good enough for me, I didn't need the excitement.

 

[Forrest Anderson]

In areas where the OFK 700 Laminate Trimmer is on sale (sorry, but it's one of these annoying NAINA things!)...

...Festool produce a selection of cutters for this machine. One of them goes by the designation "HW 45 deg D 24/10 S8 OFK 700" and has order No 491669:

It has a 45 angle, a flat bottom, and has a collet dia of 8mm.

The OFK 700 is a router designed for trimming/rounding/chamfering edges, and can be used horizontally as well as vertically, but I can't think of any reason why this bit couldn't be used in a standard router.

Currently Toolsave in the UK is offering such a bit on eBay, and although they don't advertise as being able to ship outside the UK, I wouldn't be surprised if they were happy to do so.

Mind you, filing or grinding the point off a normal chamfer router bit would probably be cheaper!

Forrest

 

[Brice Burrell]

Forrest, as always, you come up with great info, thanks. That bit looks like the perfect fit for this job.

 

[clampman1]

Brice,

Excellent article and excellent pictures as well. I'm glad to see that you took the time to spread the word about the jack miter.

That is a technique that actually is pretty alive and well in CT, at least. When I was full time trimming and had a good sized crew, six of the guys on my crew were fast at jack mitering, simply because we did so much of it.

In fact, the last trim I did personally was a 3/4 circular turret with about 12 windows overlooking Long Island Sound. Each mull was jack mitered into the head casing around the room. There was no other way to do that job and have it look right, and besides, it was the easiest and fastest way to do it.

On some jobs with large window walls, if you can get to the framer in time you can have him frame between windows with 2x4's in 2x6 walls, then run your mulls behind the casing, and your horizontals behind the mulls. Only the casing is proud of the rock, giving the entire window wall the appearance of one window.

For the fellow removing the mahogony casing, even if it were done before pocket screws and biscuits, the casing and mulls may well be backed with scrap glued to both the casing and mulls. So, you might want to work  both at the same time.

Brice,

You can do the same thing that you did with the chamfer bit with lower angled chamfer bits, then use them in a router table to make delicate little raised panels for things like small, raised panel pilasters and the like. With the bearing removed and a cutting edge on the bottom, you can cut the flat on the panel so it will go into your stile and rail dados. These are best done on a router table of course using a couple of those handled things that look like a grouting tool.

Good thread. Long live the jack miter.

Regards,
Jimc

 

[Dave Ronyak]

Thanks, JMC.  I'll certainly be cautious when removing that mahogany trim. 

Dave R.

 

[Grasshopper]

I was looking at this old thread.

Looks very good. Any idea where the pictures went?

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.

 

[justinh]

Here's an article by Katz on the subject.

http://www.garymkatz.com/TrimTechniques/jack_miter_jig.html

Since it's publication Kreg has come out with router bits specifically for the application as part of their beaded face frame system.  If your moulding detail works with the sizes they offer it saves the time of modifying a chamfer bit.

Another way of doing the quirk detail that Gary shows is to cut the miter with a handsaw with a guide and then trim off the bead with a stopped cut in the table saw.  The back of the casing and the over cut from the round blade is hidden. It requires a more organized work flow to keep from moving the fence for right and left hand jacks.  Having done it both ways but I find The handsaw/table saw method a bit faster.

 

[Brice Burrell]

I was looking at this old thread.

Looks very good. Any idea where the pictures went?

Here's a PDF copy of this article from my old website.  The pdf includes all the same text and the pictures that are missing here.

 

[Grasshopper]

Thank you!

I was looking at this old thread.

Looks very good. Any idea where the pictures went?

Here's a PDF copy of this article from my old website.  The pdf includes all the same text and the pictures that are missing here.