drilling deep 3/4" holes

[Bob]

I want to drill several 3/4" holes for bench dogs in a laminated workbench top (prior to assembly) that will be 3 inches thick. My preferred approach would be my drill press with a 3/4" Forstner bit. The bits I have will barely hand 2 1/2" depth. I need suggestions for the deeper hole. Right now, I'm looking at buying a good old fashioned Brace and bit. I'm sure some will suggest drilling part way, than flipping over and drilling from the other side. I don't feel that's a very precise operation, but if you have a technique to do it, I am all ears.

Bob

[Bob]

Right after posting this message, I discovered Forstner bit extensions. They are expensive ($29 each). Does anyone have any experience with these? I am little skeptical of the two allen screws used to hold the Forstner bit in place in the extension.

Bob

[Leon]

I was going to suggest the extension but I think I would try the drill from both sides approach.

If you use a forsner bit in a drill press you can insure a 90 degree hole relative to the surface. Try using a small regular drill bit that will go all they way through. Let that hole be your index point to start both top and bottom holes. Test on a scrap..

Or Go as deep as you can with the forstner bit and finish the last half inch with a new and decent quality spade bit. Those bits tend to be long enough and when the point starts to come through the bottom, finish from the bottom side to reduce tear out.

[Robert Bonomi]

Well, I just got the new MLCS catalog. In it is an 'extender' for Forstner bits. gives another 3" of shaft length. Crowbar not needed for the wallet, they're all of $8.95 qty 1, ($6.95 ea, for 2 or more) item # 9270.

[Mike in Mystic]

I recently made a bench and did the same thing - 3/4" dog holes. I used the following drill guide:

's a bit pricey, but it was the only option for me to get the holes in the middle part of my bench (I made 4 rows of dog holes to use with the Veritas twin-screw vise). It worked extremely well. I used it in conjunction with a 3/4" auger bit after starting the holes with a 3/4" forstner bit. It wasn't really that tough.

Mike

[jo4hn]

I have one. Used it to drill 1" holes into a laminate of oak, walnut, and purple heart. Worked fine. Not sure about the allen screws in a hard use environment though. mahalo, jo4hn

[nospambob]

[Rkola]

I used a 3/4" Auger bit (fairly inexpensive at Lowes) in a 1/2" Hand held drill. Worked great, but requires pretty firm control, since the bit is so aggressive. (Bench top was about 3" thick, laminated MDF) The lead screw tends to help drive a pretty straight hole, and chip out on the bottom was minimal. Once again - this is a VERY aggressive bit, so slow drilling speed is needed, along with a frim grip on the drill!

Ron

[JMartin957]

Check out the Forstner bits from Connecticut Valley Manufacturing (CONVALCO). The original manufacturer. Expensive, but better. Also longer.

John Martin

[mac davis]

I'm sure that you'll get more knowledgeable answers, but I ended up using an Irwin 3/4" spade bit on my bench..

My neighborhood mentor said that forstner bits were for drilling shallow, flat bottom holes... and I was drilling hole through 3 1/2 of plywood and particle board, which I'd rather not use my good bits for..

also, my forstner bits are very short (aka cheap) and the spade bits come in several sizes, up to about 18"... I bought 3 because I knew I'd chew them up drilling all those holes... needed 2..

Mac

[Bob]

Well, I've gotten several good answers, including yours. So I ambled down to my favorite woodworking store to have a look at all the offerings and talk it over them, as well. I am assembling the benchtop in sections, so a drill press is a viable driver and certainly my preferred approach for accuracy. They had an option that I did not see mentioned here. Its a 3/4" precision brad point drill bit with 1/2" shank. It will drill to a depth of

6 1/2". I decided to give it a go. It was $18.00. I'll let you guys know how it works out.

Bob

[Wilson]

I have some Woodeater bits from HD or L. They have a powerful leadscrew and a cutting face much like an wuger bit. I'd start with the Forstner or brad point and then use the Woodeater. They cut well and pull themselves along. Actually, they pull so well you usually can't back up, so go all the way in one cut and then take ite shank out of the chuck. I used them for the holes fo relectric wire and pipes in my house. The only trouble is that hitting a nail costs $6!

Wilson

[Phisherman]

A drill guide with your corded hand drill and a spade bit. Clamp the drill guide to the bench. Every inch or so, clean out the hole with a shop vac hose. A new spade bit is inexpensive and sharp.

[Dick Durbin]

That's what I did. You might be surprised at how easy and satisfying it is. The one I used belonged to my father.

Dick Durbin

[Bob]

Excellent suggestion, John. It looks like they could handle a 4" deep cut.

Bob

[Lawrence Wasserman]

You should be able to put an extension on a 3/4" Forstner without much trouble. Or, you could drill to your maximum depth with the forstner and finish up with a spade bit.

-- Larry Wasserman Baltimore, Maryland [e-mail]

[Spoefish]

Actually a drill press can be pretty handy for this - I did the dog holes on a 2' x 6' x 2 3/4" maple top I picked up a while back. Pondered on how to get it up onto my dril press table, then realized that I could work on the floor instead. Put a 2 x 6 under each end of the bench top (clamped to the top) so it would clear the base of the drill press (I used a nice old Delta Homecraft benchtop I have, but could have done the same with my floor mounted drill press - in either case you will have to take the table off, and lower the head down close to the floor). I used a 3/4" brad point drill and got nice clean holes (I did back them up with a board to prevent tear out when the drill came through). Just kept sliding the bench top along and getting each hole centered - the weight of the top kept it from moving once I started drilling. If you could not drill deep enough, the hole you have started will serve as a guide to finishing it with a brace and auger bit - again, you will need to back up the hole to prevent tear out. In any case bringing the drill press to the work this way provided a good solution - not too obvious to me at first, but once the light went on, I think there are other places where it will be helpful.

Stephen

[bugbear]

I'd create the 2 1/2 holes with your forstener, the continue with a 3/4" auger in a brace. The brace and auger should be obtinable "for cheap" at any flea market or yard sale. Make sure the auger is in good shape.

The "normal" trick for high quality work with a brace auger is to drill until the lead screw comes out on the far side, and then re-enter the lead into this hole from the other side.

In this way the "face" is cut cleanly but the nickers at the edge of the auger, eliminating tearing or splitting.

BugBear

[Bob]

That sounds like a good approach, except I can't figure out how to lower the head on my Jet Floor model drill press. I don't think its possible on many drill presses. My benchtop is assembled in pieces so I don't have to get the whole thing up on the drill press. My plan is to set it on the table with side supporting stands (Probably my Rockler roller bearing stands). I was please to hear that someone had used the brad point drill bit. I just bought one.

Bob

[Bob]

I never thought about buying one at a flea market. In fact I've never shopped there before. We have a huge flea market in my area. I think I'll head there this weekend and see what I can find.

Bob