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Locking miter on large format work piece

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Forum topic by EightPaws posted 03-31-2017 05:12 PM 1047 views 0 times favorited 11 replies Add to Favorites Watch
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EightPaws

5 posts in 262 days


03-31-2017 05:12 PM

Topic tags/keywords: locking miter free hand freehand walnut door

Hi Folks,
We are building a door and facing with 3/4” x 5” walnut planks running horizontally. The door is 42” wide by 84” tall and 3” thick. The design calls for the walnut to wrap around the face to sides and be grain matched as much as possible. We would like to use a locking miter but would have to use a field mounted fence (not a router table or jointer) to cut the long (84”) miter locks on the door. Can you share your experience in setting up something like this to help us get it right?
Thanks Steve


11 replies so far

View Rich's profile

Rich

1987 posts in 430 days


#1 posted 03-31-2017 05:47 PM

I’m having a hard time picturing what you are building. Can you provide more info? Also, why can’t you run the lock miter cut on the router table?

-- No matter how much you push the envelope, it'll still be stationery.

View dschlic1's profile

dschlic1

395 posts in 1810 days


#2 posted 03-31-2017 06:21 PM

So as I understand it, the 3/4” x 5” boards will be 42” long? So when they are glued up, your miter will be in the end grain of the boards? Will the door be hollow? If so you might be able to glue up the two sides and then cut the lock miter on the edges with a router table.

The lock miter bit needs exact positioning in both the vertical and horizontal directions. You might be able to make some kind of a special fence for a hand held router, however most locked miter bits are too large of diameter for hand held routers.

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EightPaws

5 posts in 262 days


#3 posted 03-31-2017 06:24 PM

Hey Rich,
The door will be constructed with steel studs and acoustic foam insulation to minimize sound transfer. The door will use Krownlab hardware and will be a custom walnut “barn door”

The walnut is locally harvested and milled 3/4” (thick) by 5” wide planks. The planks will be fastened to the metal studs. The issue we are seeking advice on is how to cut the locking miter along the vertical edges where the walnut changes direction from the 42” face to the 3” edge.

Istead of trying to cut each of the ~17 walnut boards perfectly and installing them precisely, we are thinking about fastening the boards first, leaving them long, then cut in place and Miter. We can easily clamp a temporary fence to cut all boards to the right width (~42”), but we are wondering if anyone has also used this type of fence to guide a router when cutting a locking miter.
Thanks and appreciate the advice.

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EightPaws

5 posts in 262 days


#4 posted 03-31-2017 07:20 PM

Thanks DSCHLIC1,
These will be 42” long and the miter will be on the edge grain. Have a Dewalt 2 hp router w 1/2” collect that can take the 1-3/4” diameter locking miter bit.

I’d like to cut the miter once all boards have been fastened (glue and screw through tongues of TnG walnut into steel studs). Thinking about cutting the miter, I believe I am better off managing the router across the large workpiece with a temporary fence even if I need to take several passes. Otherwise I have the unwieldy task of moving a large workpiece (42”x84”) across a router table. Hope I am thinking about this correctly.

View Rich's profile

Rich

1987 posts in 430 days


#5 posted 03-31-2017 07:37 PM

I’m not sure I can offer much help. I understand what your plan is. I’m just having a hard time wrapping my head around doing a lock miter cut on end grain and without the stability of a table and sturdy fence.

Lock miters are very unforgiving. If you’ve used them much, you know what I mean. If you have a fence for your router, you can do some test cuts to get it, and the bit depth set for a good joint. The trick is going to be the cut where the board is usually vertical against the fence. You’re not going to have a full height fence, like on a router table, so keeping the router flat on the board edge is going to be difficult.

I think it would be helpful to come up with some sort of jig that you can affix to the door edge to allow the router to have a wider bed to ride on than just the 3/4” board edge. Not sure if that makes sense.

-- No matter how much you push the envelope, it'll still be stationery.

View bonesbr549's profile

bonesbr549

1445 posts in 2907 days


#6 posted 03-31-2017 07:45 PM

So if i get u right you not doing a solid 3” door but want to creat the appearance? And the concern is a locking miter being milled over 84”.

I’d be concerned about not applying equal pressure through the entire cut resulting in inconsistent cuts. Thats been the biggest drawback of that joint IMO.

However a big router table (infeed/outfeed) and possibly adding a powerfeed, should deal with that.

Post some pics of that, sounds dang impressive. I’d love to see the door opening :) Cheers

-- Sooner or later Liberals run out of other people's money.

View EightPaws's profile

EightPaws

5 posts in 262 days


#7 posted 03-31-2017 07:49 PM

Great advice Rich,
I may have inadvertently steered you wrong—sorry bout that. The locking miter will be on the 3/4” end grain but the router should be riding on the face of door. The door will lie flat (42”x84” side horizontal) during the routing process kinda like a large, flat table. Once the milling is complete, the door will be stood up and this surface will be the vertical door face. Apologies for my poor description.

View HerbC's profile

HerbC

1688 posts in 2700 days


#8 posted 04-01-2017 01:41 AM

The cuts to make this joint require the large diameter of the bit (which is on the inboard end of the bit) to cut the inside of the board. One cut is made with the board flat on the table and the other cut is made with the board vertical against the fence. If you have mounted the boards to the metal framing you will not be able to orient the router properly to make the cut even is the router is not mounted in the table…

You will probably be able to make it work by using a router sled on the router table with hold down clamps to route the end of the individual planks.

Good luck. The lock miter joint/bit can be very useful but can also be a royal pain in the * to set up and execute properly.

Be Careful!

Herb

-- Herb, Florida - Here's why I close most messages with "Be Careful!" http://lumberjocks.com/HerbC/blog/17090

View jerryminer's profile

jerryminer

812 posts in 1282 days


#9 posted 04-01-2017 07:27 AM

Sounds nearly impossible with a hand-held router. Lock miter on both front and back faces? I can’t imagine how you can get a router bit in the space, oriented the right way, to make these cuts. Maybe I don’t have it pictured in my head right.

For the level of precision you would need to get all those 5” pieces to come out clean, I would be talking to someone with a CNC, and milling the boards individually, precisely identical.

-- Jerry, making sawdust professionally since 1976

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jerryminer

812 posts in 1282 days


#10 posted 04-01-2017 08:20 AM

Just for giggles, I did a SketchUp drawing of what the set-up for a router might look like. In the last drawing, there may not be enough room to get the bit past the “top side” mitered edge.

-- Jerry, making sawdust professionally since 1976

View EightPaws's profile

EightPaws

5 posts in 262 days


#11 posted 04-01-2017 01:45 PM

Gosh you guys are really great. Thanks for pointing out my misunderstanding about milling from the surface of the door—seems obvious once Herb and Jerry pointed it out.

Jerry, I gotta tell you that you are one creative guy. Very much appreciate your sketch up showing how complicated this “little project” has become.

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