Router bit for cutting dovetail slots

[Dale Critchlow]

I am repairing the hangers of several pieces of artwork which are mounted on 1/2 inch MDF. They are hung to the wall using a dry wall screw which fits into a dovetail slot in the MDF. The dovetail is about 25 degrees (for each side). The diameter at the bottom of the dovetail slot is 2/8 inch. It is about 1/4 inch deep.

I have not be able to find such a router bit on the internet.

Any suggestions would be greatly appreciated.

Thanks,

Dale

[Mike Henderson]

Pictures would help.

Mike

[Myk Rian]

The closest you'll find is 22.5º, and it won't be a dovetail bit.
Are you discussing a French cleat?
A drywall screw isn't very strong for holding things. They break easily.

[Dale Critchlow]

The slot is has a dovetail shape. It looks like it was made by plunging a 3/8" dovetail bit about 1/4" deep and then moving the bit sideways to make a slot. I measured the angle and it was about 25 degrees. It could be 22.5 degrees.

The artwork was mounted on 1/2" MDF by a company in Canada. Apparently, you provide the artwork and they mount it. It looks very nice but since they used MDF it is not very strong. The dry wall screw is not the weakest link. One side of the dovetail slot broke off so it won't hold the screw head. I was trying to fix it by making another slot. The lady who asked me to fix it has a large number of these which are hung in a retirement community.

Perhaps, I can find another approach to fixing it.

Thanks,

Dale

[Tom M King]

It's not a dovetail bit. I'll see if I can find one. I can't remember what they are called, but there is one for this specific purpose.

[Tom M King]

Found it. Keyhole cutter. http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_keyhl.html#T-slot_cutter_Anchor

[Earl McLain]

I'd agree with Tom, sounds like a keyhole bit that has been wallowed out by the drywall screw to the point of breaking. I'd think that MDF would have trouble holding its own weight in that application--especially if the environment is humid part of the year.
earl

[Dale Critchlow]

Thanks Tom. I will give it a try. I agree with Earl that MDF is too weak for this applicatioin. It works OK until someone trys top take the picture off the wall by pulling out at the bottom which breaks the MDF at the edge of the slot. To do it correctly, you have to slide it sideways to the entry hole. This is not obvious.

I may try to repair it by gluing a 1/8" thick strip of maple along the edge of the present slot.

Dale

[Phil Barrett]

That sounds like a goofy way to hang pictures.

I'd ditch the keyhole approach and just put standard hanger wire in. You might need to put some anchor plates on the sides. Proven, simple and no more "oops yanked it off the wall" damage.

Or, just mount a french cleat at the back of the work.

[Ellen Benkin]

French cleats are easy and hold an amazing amount of weight.

[Jim Becker]

You really need two bits for this...the first is a straight bit that you use to bore a hole to proper depth that is just large enough to fit the "dovetail" bit you'll cut your slot with. The dovetail bit is then used by inserting it into that hole and then moving it laterally to create the slot. Dovetail bits come in different angles to best handle hardwood vs softwood. I believe the angles are steeper for softwood bits (I could have that backwards) and those would be the best for this operation, but not required. An alternative bit would be a tee-slot bit used the same way.

Personally, I use traditional eye and wire mounting for picture frames...easier to balance and level than a slot over a screw, IMHO, but for bunches of small picture frames, less practical.

[Dale Critchlow]

Hi Ellen: I agree French cleats work well. I use them often. I have been considering converting these frames to FCs.

Jim: I measure the angle of the present slots. Ther are about 25 degrees on each side. The question is where to buy the such a bit.

Thanks,

Dale

[glenn bradley]

I use a keyhole bit often on solid wood picture frames. I share your concern about MDF and this application.

310053

[Lee Schierer]

Found it. Keyhole cutter. http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_keyhl.html#T-slot_cutter_Anchor

Here's another keyhole bit.
(http://www.routerbitworld.com/Key-Hole-Bits-s/254.htm)

[John TenEyck]

I would route out a something several inches square and glue in a piece of hardwood into the back side of the MDF, then put the keyhole slot in that.

John