Precision-drilling wood edge

[Mike Rocket J. Squirrel Elliot]

Crossposted alt.home.repair / rec.woodworking -- mainly because this is sort of a woodworking question, but the wood is part of my bathroom wall.

I have received a pair of barrel hinges from Rockler. I'm going to try to use them to hang the new medicine cabinet door on the cabinet I built into the wall. An earlier post described how the door fits flush against the face of the cabinet, and barrel hinges seem to be a good solution. So anyway.

I need to drill a 14mm diameter hole into the edge of the cabinet side to accept the hinges. The side is 3/4'' MDF. 14mm is 0.551'', which does not leave a lot of sidewall in 3/4'' material -- about 3/32'' per side. If the cabinet was NOT in the wall I would put the sides into my drill press so I'd have a fighting chance of getting the hole straight. But it is in the plaster wall and trying to do this job by eye and with a hand drill is not likely to succeed. (This is what happens when I don't plan ahead real well.)

What kind of hand drill-alignment gadgets are there that can help a fellow drill square, straight, and level?

If I can run a 14mm diameter, 15.5mm deep hole exactly down the middle of this 3/4'' -- TWICE! -- I will be a hero in my own home. My wife will think I am quite the he-man, my kids . . . well, they are teenagers. I might be able to raise a "whatever," out of them. But I'd be darn pleased.

[Chris Carruth]

You can make a drill guide out of 1" thick stock, with the holes made on the drill press. Use the hinge itself as a pattern to mark the holes. Once drilled, use doublesided tape to secure to the side walls and drill as needed. Remove and mount hinges.

[Mike Rocket J. Squirrel Elliot]

Hm. Lemme think about this. With a barrel hinge, there is ONE hole per hinge. In my case, the hole is 14mm diameter, and goes in 15.5mm deep. Right into the edge of the 3/4'' MDF cabinet wall.

Knowing me, if I taped a pre-drilled bit of stock against the wall, I'd probably tug the tape out of place when I shoved that 14mm brad-point drill down into it. But I could make a right-angled fixture and screw it onto the side of the MDF -- I could patch the screw holes later and paint over them.

I think you have answered my plea for help! Thank you!

-- Mike "Rocket J Squirrel" Elliott

71 Type 2: the Wonderbus 84 Westphalia: "Mellow Yellow (The Electrical Banana)" KG6RCR

[MG]

Could use a router with a 1"/4 or 1"/2 bit, whatever your router collet is, and plunge placing the router face against the wall. Once you got a pilot hole you have a chance. Whatever! MG

[Mike Rocket J. Squirrel Elliot]

Heh. Not a bad idea . . . except I reckon the 14mm brad-point bit I have on order is too long. I like it otherwise, esp. the idea of jamming a

14mm bit into MDF at 20,000 rpm. Yee haw!

[d.kessell]

Rocket J. notes: Turtles have a drag coefficient of .03 Can you imagine how slow they'd be with more drag?

Dan

[Morris Dovey]

Or you could use a C-Clamp to hold your right-angled fixture in place and not have screw holes to patch...

[Paul Kierstead]

Err, he never said put your 14mm bit in the router. Read.

[Mike Rocket J. Squirrel Elliot]

Turtles IN drag?

[Mike Rocket J. Squirrel Elliot]

Oh, right. I jumped to a conclusion. Use the router for the pilot hole. My bad.

[MG]

NO,NO The routher is to drill only a pilot hole. Then you can have a better feeling when you drill free hand. Perhaps you want to go with small increment in diameter. The router leaves you no choice on the bit diameter.

MG

[Mike Rocket J. Squirrel Elliot]

Um. Duh?

[Mike Rocket J. Squirrel Elliot]

Okay, now back to this excellent suggestion which I initially misunderstood.

To recap: I'll be mounting two 14mm barrel hinges into the edge of 3/4'' MDF. The body of the barrel hinge measures 0.558''. The mfgr specifies

14mm holes (0.5512) so this is a press-fit. A 35/64'' holes will be too tight, and the mfgr does not recommend oversized holes, so 9/16'' will be too loose, so 14mm it is. The hole is to be 15.5mm (.61'') deep.

I did a couple trial plunges with a 1/4'' straight router bit to get a pilot hole then followed that my largest twist-drill bit (1/2'') and it tore the sidewall, so a twist-drill bit is not the way to go. I have a

14mm brad-point bit coming from Lee Valley, but I reckon it will tear out the thin side wall, also.

I don't have a 14mm straight router bit, but a test-drive using a 3/4'' diameter bit real close to the edge did not result in sidewall tear-out.

I reckon I could do the whole job with a single plunge if I had a 14mm diameter straight router bit w/ 1/4'' shaft. Rockler doesn't seem to have this listed. Does such an animal exist?

[Morris Dovey]

Mike...

It isn't really needed. Some years back I built a fixture for routing board edges that allowed me to do anything to the edge of a 3/4" thick board that I could do a face.

I built two 15"-long wooden L-shaped brackets and set them on my bench like so:

| | | | ___| |___

Then at one end I glued a block (approx 3/4 x 3 x 3-1/2) between the two brackets and clamped it overnight.

Then (next day), I turned the fixture right side up, inserted the

1x12 whose end I wanted to rout between the two "jaws" and used a C-clamp to squeeze the open end, which secured the 1x12 in place in the fixture. I put the whole works in my bench vise, adjusted my router guide, and (supporting the router base on the fixture's "table" surface) did the necessary routing.

Next point: You can route any size hole you want provided that the cutting diameter is smaller than the diameter of the hole. You may need to drill/cut/sand a template to suit a bushing for your hole; but you can do it. I do that kind of drilling fairly regularly on my CNC machine - and will post a graphic of the tool path for drilling a 2" hole with a 1/4" bit on ABPW. It's a bit more setup work without the CNC; but exactly the same idea.

[Mike Rocket J. Squirrel Elliot]

I don't have any way to clamp the work piece. The edge I need to put the hole into is part of a medicine cabinet already in the bathroom wall. The top, bottom, and right/left sides of the cabinet are flush with the plaster wall. It is into one of these sides -- 3/4'' MDF -- that I need to put the hole into. Otherwise, believe me, I would clamp the piece on the bench and set up guides and stuff.

Hm. Okay, this is looking promising.

Let's say I want to route a 5/8ths diameter hole, 5/8ths deep, into the edge of this piece of in-wall 3/4'' MDF. I can clamp a fixture to the side of the cabinet by screwing it to the inside )a few screw holes, a little spackle . . . ) -- what would I make the bushing/guide out of so the router does not cut it, nor mess up the router bit? Some special straight router bit I can plunge with that has a guide wheel on the motor side?

[Morris Dovey]

The easiest way to get a reasonably precise hole would be to use a template guide bushing (see for examples) in conjunction with a hole template. The template needn't be anything more than a piece of plywood or hardboard with a circular through-hole for the guide bushing to bear against while outlining the hole you want. Cleaning out the interior of the hole is easy to do freehand.

I'd glue the hardboard template to the edge of a piece of 1" scrap so that I could clamp/screw the whole fixture to the board whose edge I want to route.

The only part that takes a bit of thought is working out the correct guide bushing/template hole size/bit size combination. If I'm thinking straight, the template hole diameter should be given by:

T = H + (G - C) where:

T Diameter of template hole H Diameter of desired edge hole G Outside diameter of guide bushing C Bit's cutting diameter

For a 5/8" hole you could use (for example) a 1/4" straight bit and a 1/2" template guide bushing. Then:

T = 5/8 + (1/2 - 1/4) = 5/8 + 1/4 = 7/8

Does that make sense or do I just need more coffee?

[Duane Bozarth]

Go back to the template idea...make one from either hardwood or a piece of angle if you have it (since you said you have a drill press, this should be easy). Go with a twist or Forstner bit (although if you make a pilot hole first, a twist drill bit should be ok). To minimize/eliminate the tearout, clamp a piece of hardwood or flat iron on each side...

Whether there is a 14 mm router bit I don't know, I've not researched metric sizes, but if it is actually a 14 mm hole required by the hinge, there has to be a corresponding tool...

I've used a lot of Soss hinges over the years, but at least when I was using them they were English measurements...

[Mike Rocket J. Squirrel Elliot]

I have only access to the side /inside/ the medicine cabinet. The other side is buried behind the plaster wall.

Well, I've a 14mm brad point bit coming from Lee Valley, but I expect it will tear out like a twist drill.

This barrel hinge comes from Rockler, I presume it is euro or Asian-sourced.

[Mike Rocket J. Squirrel Elliot]

I can see how that template guide bushing would make the job simple. It also seems to me that a piece of, say, copper tubing with an i.d. a bit larger than the 1/4'' router bit shaft, and an o.d. somewhat larger than the diameter of the router bit would make a suitable bushing to keep the bit from chewing away the template.

Exactly. Any means to hold that template flush against the edge of the MDF and immobile would work just peachy.

You said there wouldn't be any math.

[Bob]

Uh, how do you control the router to follow this path?

Bob