How do I increase a 3/8" hole to 1/2"

[Brian Penning]

Only way I can think of is to get a metal plate drilled with a ½" hole and center it over the 3/8" hole.
How to center the plate I haven't figured out yet.
Suggestions?
TIA

[Chris Parks]

Plug the hole with a dowel and drill it to 1/2".

[Curt Harms]

If so, drill a 1/2" hole in a piece of scrap, plywood or whatever. Center that hole over the 3/8" hole, secure the scrap piece with double stick tape or brads or screws, the 1/2" hole will keep the forstner bit centered and drill the 3/8" hole out. I hope that makes sense.

Curt

[Tom Veatch]

Think of the 3/8" hole as a pilot hole and drill it out with a 1/2" bit.

[Joe Mioux]

Why can't you just stick your drill or drill press chucked up with a 1/2inch bit against the 3/8 inch and drill a larger hole?

[Brian Penning]

Sorry, didn't explain that it's a large piece that can't fit onto a drill press.
And when I use the 3/8" hole as a pilot hole the handdrill just runs amok.

[Doug Shepard]

You could try something like this to locate the 1/2" hole if centering needs to be really exact. Take a piece of scrap wood and drill a 1/2" hole halfway through it with a forstner. Switch to a 3/8" and drill the rest of the way through. Doing this on a DP with the scrap clamped down would work best but the spur point from the first hole would locate the second one if you have to do it with a handheld. Then stik a 3/8 dowel into your existing project hole and slip the scrap plate onto the dowel with the 1/2" side up. Clamp the plate to it, pull the dowel, and use the 1/2" counterbore to drill the rest of the way through the plate and into the project.

[Anthony Whitesell]

You didn't mention two things in your original message. 1-hand drill, no drill press, and 2- using forstner bit.

Based on that I would drill the 3/8" hole out with a 1/2" twist bit but not to full depth. Then chuck the 1/2" forstner bit and finish the hole. This will allow you to use the outside diameter as the guide for the forstner bit instead of the center spar.

[Gordon Harner]

If you can use a hole saw there is an oops arbor. The arboe will take two different size saws one the hole size and a second one with the correct bigger size. I don't know if the Borgs sell them but they're available mailorder.

[Kevin Godshall]

I recommend plugging it and redrilling it. Don't ruin the piece by making a small mistake a huge one.

[scott spencer]

Step bit?

83039

[John Thompson]

As Chris and Kevin has mentioned, plug it with 3/8 dowel.. find true center and re-drill. I have been most of the other routes and you won't be dead on without having the drill tip define center.

If it is utility hole that is not necessary to spot "right on".. then just drill a 1/2" hole in a piece of scrap.. center it best as possible and clamp it. Then drill as the scrap hole will serve as a template to hold the bit verical...

Sarge.

[Steve knight]

myself the best tool is a reamer. 1/2" is a bit of a jump but a chucking reamer will follow the hole and it does not grab or chew up the hole.

[Terry Sparks]

You didn't mention two things in your original message. 1-hand drill, no drill press, and 2- using forstner bit.



I'm just wondering why you need to use a forstner bit, are you not wanting to drill completly through the material?

If so, I would think the only way to solve the problem is to plug the existing hole and redrill, as has been mentioned. If you are drilling through the material, get yourself a hole saw kit and double up a 3/8" bit and a 1/2' bit and use the 3/8" bit as your guide through the existing hole while the 1/2" bit cuts the bigger hole.

[Dick Bringhurst]

Plug it and redrill with either a twist or brad point or forstner bit. Lot less messing around. Actually with a twist bit you don't have to plug it. Dick B.

[Bill Huber]

Now if I had ever done something like that, drill the wrong size hole I would have plugged it and started over.

I have heard that it works very well.....:D

[Brian Penning]

Sorry, better explanation: is I'm matching a piece with several mating dowel locations in which some require a new larger dowel. I was hoping the smaller diameter hole could somehow be used as a guide to drill the larger hole. Being mismatched by even 3 or 4 thou could cause problems. I can only use a hand drill.

[jim gossage]

take a piece of scrap about 1 1/2" thick and drill a 1/2" hole into it about 3/4" deep with a brad point bit. take a 3/8" brad point bit, and using the brad point hole from the last bit as your center, drill through the scrap. the 3/8" hole at the bottom will allow you to center over the original hole with a 3/8" dowel, and then clamp the scrap down. then, using the 1/2" hole as a pilot, finish drilling through the scrap and down into your piece. if it has to be perfectly straight, you'll need a small drill piece to drill the scrap. if you can't find a drill press, i'd be happy to mail you said scrap.

[Dick Bringhurst]

Brian, Are there dowels already in the "locations" and if so are they glued in now? Dick b.

[Brian Penning]

Brian, Are there dowels already in the "locations" and if so are they glued in now? Dick b.

No, this is an old antique loveseat that I'm repairing. Been able to get most of the old dowels out and now the 3/8 holes are too big.
This "thing" is completely apart now including the arm and leg connections.

http://i47.photobucket.com/albums/f193/Bri68/Miscilaneous/IMG_3249.jpg?t=1204461507

[Dick Bringhurst]

Wow. I was going to suggest using "dowel points" but they may not be able to give you the accuracy tolerances you need if the holes are even slightly over size. Dick B.

[Greg Hines, MD]

You might try using a plunge router, clamped in place, to drill out the smaller holes. I have done that on a couple of different projects, and it works well.

Doc

[norm brownstein]

glue a 3/8 dowel into the hole, than redrill with 1/2 bit.

[Wayne Cannon]

(1) Plug it and re-drill with a 1/2" bit
(2) Drill a 1/2" hole in a separate, relatively-thick, block of hard wood; clamp it over your 3/8" hole; and use it to guide your 1/2" bit (i.e., if you don't trust using the 3/8" hole as a pilot hole for your 1/2" bit).

The following work using hole saws, but I haven't seen a hole saw smaller than 5/8" to 3/4" with a separate mandrel.

(3) Mount a 3/8" hole saw inside a 1/2" hole saw and let the 3/8" saw serve as a guide while cutting the 1/2" hole (though I've never seen a 3/8" hole saws).
(4) Install a 1/4" shank 3/8" drill bit in the hole saw mandrel with a 1/2" hole saw. Let the 3/8" pilot bit guide the 1/2" hole saw (requires one of the models of hole saws that allow you to provide your own pilot bit -- many have a dedicated mandrel and pilot bit).
(5) Slip a 3/8" bushing (wood, nylon, brass, etc.) over the pilot bit of a 1/2" hole saw. The bushing will keep the hole saw centered in the 3/8" hole.

[Lee Schierer]

Wow, a lot of complex answers. How about just drilling it bigger one drill size at a time. Fractional drills increase in size by 1/64" increments so you shold be able to use the 3/8" hole as a guide and increase the drill by 1/64 increments. The small size change should easily follow the pilot hole without wandering since you are only shaving 1/128" off each side. You will need to change drill bits 8 times to get to 1/2".

[jacques nolin]

Only way I can think of is to get a metal plate drilled with a ½" hole and center it over the 3/8" hole.
How to center the plate I haven't figured out yet.
Suggestions?
TIA
drill a 3/8 hole in a metal plate center it on the hole with the bit shank then drill the 1/2 hole hope it helps

[Ben Grunow]

I would make/add a 1/8" bushing to the other holes to allow them to accept a 3/8" dowel.





This is a joke in case you didnt get it.