10" Long Forstner Bit Extender : Can they double up

[Clarence Martinn]

Looking at a 10 " Forstner Bit extender. It's from MLCS. Is it possible to add a 2nd Extender of the same length to that 1st Extender ? Want to use it for a 4 Inch Forstner Bit, to bore out the hole, on a Deep wood Vase.

[Tom M King]

I've done it with other brands of bit extenders. Just make sure the set screws get a really good bite. It might even be a good idea to sharpen the ends of them. As you might imagine, it's a real headache for one to come disconnected deep inside something.

[Bill Dufour]

Make sure the male end is hex not round or at least grind a set screw flat.
Bil lD

[John K Jordan]

Looking at a 10 " Forstner Bit extender. It's from MLCS. Is it possible to add a 2nd Extender of the same length to that 1st Extender ? Want to use it for a 4 Inch Forstner Bit, to bore out the hole, on a Deep wood Vase.

I've put extensions together several times for deep holes and to drill a hole through and otherwise inaccessible board. No big problems.

The longest was over 4' drilling 1" holes through several joists between floors to run romex to get power from a generator into the center of the house. (Drilling the holes the "normal" way would have required removing a lot of sheetrock.)

[Bill Dufour]

Now when I have to use a flexible drill or a stack of drill extensions to drill a hole for running wire inside a stud bay I have a trick to keep it centered in the bay. I shove in a foam swim noddle and run the drill through that.They are a nice outer diameter that just fits in a 3.5" space keeping the drill centered if you are carefull and do not go through the side.
Bil lD

[Larry Frank]

Can you do it...yes. But, it will be interesting if it survives. The description says it is for bits under 2.25" . The 4" but will really stress it and could deform.

[Clarence Martinn]

Since I have 38 inches between centers on the Sears Craftsman Lathe, and 40 inches between centers on my 2 other wood lathes, it would interesting to see if I could bore 37 to 38 inches with the 4 inch Forstner bit and several extensions !

[John K Jordan]

Since I have 38 inches between centers on the Sears Craftsman Lathe, and 40 inches between centers on my 2 other wood lathes, it would interesting to see if I could bore 37 to 38 inches with the 4 inch Forstner bit and several extensions !

Seems like it would be challenging to keep the hole straight with the flex from several thin extensions. Maybe manufacture a stout large-diameter extension from a 1/2" or 1" steel bar and drive it with an industrial drill or a floor model drill press? Also, I used to use a radial arm saw as a horizontal drill to drill deep holes in end grain.

A gun drill is made for drilling long, straight holes but I haven't seen one 4" in diameter. (Maybe a cannon drill? :)) When using a drilling deep holes with a forstner bit I always direct a strong stream of compressed air in the back of the how while drilling to clear chips and keep the bit cooler. I like to use carbide bits for drilling on the lathe.

Maybe drill a smaller hole and use a captive deep hollowing rig to get the right diameter?

JKJ

[Larry Frank]

Fat fingered and posted duplicate.

[Larry Frank]

Drilling end grain with 4" diameter will take a lot of horsepower.

Have you tried drilling that size with no extension?

You may want to check the shank size of the 4" bit and make certain it will fit the extension . Large sized Forstner bits have larger shanks.

My prediction is that you will break the extensions as that drill is way over the specs for the extensions. Be careful!