Your cart is empty.
Your cart is empty.Drilling with forstner bits to achieve a flat bottom hole or to start a deep hole turning project like on a larger vase or vessel is essentially impossible with a standard length forstner bit. To remedy this issue we have developed a heavy duty steel extension that allows you to secure a 3/8 inch shank forstner bit into the end collet. The forstner bit extension gives you additional 5-5/8 inches of reach to bore deeper into your projects. This will help you create larger diameter starter holes or help when you need to drill in just a little further than the standard bit length will allow. The extension can be used with forstner bits on drill presses, lathes with a drill chuck installed (drill chuck not included) or with a power drill. One of the most common uses for the forstner bit extension is for woodturners who need to bore out starter holes on larger vessels. However, the extension works exceptionally well for projects like salt shakers, pepper mills or even wood turned beverage mugs. Contractors use the extension when they need to bore deep holes for running cables or wires and they also use it for joining larger timbers. The forstner bit extender is made from solid, heavy duty machined steel. It is designed to be used with forstner bits only. The collet inside diameter is 3/8 inch. This tolerance is very tight and designed to accept forstner bits with shank sizes of 3/8 inch or slightly smaller. Please note that some forstner bit manufacturers produce bits that say 3/8 inch shank size when in fact they are not. If you measure your bit shank and it is 3/8 inch, your bit should fit once the set screws are loosened. The collet outside diameter is 25/32 inch without the set screws protruding outward. The reason this is important is that as we mentioned earlier, some bits may have slightly different shank sizes. This means the set screws may protrude outwardly from the collet. The minimum size hole this extension will allow you to drill is 13/16".
RJM
Reviewed in the United States on February 20, 2025
Woodworking.
Sergei T
Reviewed in Canada on February 10, 2025
After several attempts to purchase and returns of an extension for the forstner bit that I could use on my wood lathe, this one works well with Steelex D2856 1-9/16-Inch Forstner Bit. The problem was that previously purchased extensions were way out of specs. Fun fact: an american made IRWIN drill bit was also way out of specs.... Anyways I guess this is the world we live in: there is so much unusable products on the market. We have nobody to blame: this is our, customers fault.
Stephen white
Reviewed in Canada on July 1, 2024
Makes the 3.5 inch long Forster bits usable on the lath for turning cases and pitchers
AARON P.
Reviewed in the United States on May 7, 2024
This is a great extension. I tested its balance with my drill press set on its highest speed. It spun perfectly and balanced. I connected a 1/4" forstner bit, and it drilled a great hole with accuracy. This extension will get plenty of use with my woodworking and forstner bits.
N T Davidson
Reviewed in the United Kingdom on May 20, 2024
I was very pleased with this extension but and was able to use it with a forstner bit to bore out an end grain vase to a depth of about 9inches. The only caveat is to beware of the diameter in the boss with the locking grub screws as this sets the minimum diameter that can be bored out and I couldn't use my 2x smallest bits. It should be obvious, but you have to keep withdrawing the lathe tailstock to clear the shavings from the hole.
Brindy
Reviewed in the United States on December 25, 2024
On those infrequent occasions when you need more length, this is the tool. It’s a great quality and fit very well. It’s very true and spins without wobble.
Max Wax
Reviewed in Australia on November 16, 2023
I use it primarily for drilling deep holes in wood turning projects.
Michael
Reviewed in the United Arab Emirates on October 22, 2023
Need to drill a deeper hole that the length of your Forstner bit allows? Get this. Finish is pretty good, all my bits fitted snugly - nice extension, no issues, very pleased with this purchase.
Carfunkle
Reviewed in the United States on April 14, 2023
When purchased, I worried that two set screws would not hold the significant torque created in using Forstner bits. I had thoughts of grinding small flats on the neck of the bits, under the screws but figured I would try it as advertised first. My first need of it was in the drilling of a 2" hole. Rather than drill it in steps, I sharpened my 2" bit, reduced my lathe speed to about 275 rpm and drilled the hole I needed with no slippage, stopping to clear the swarf about every half inch . Color me happy.
D.J
Reviewed in the United States on March 28, 2022
This is sold “linked” with some forstner bits. Just realize that it is obviously useless to extend a bit with diameter less than the linking head on this extension tool. To repeat, This is ONLY useful to extend a larger diameter bit. Im not sure what size the linking head is but it will NOT extend a bit 1/2” in diameter because the head cannot extend into that small of a space so it is useless for that purpose. I wanted to drill 1/2” hole into a 4x6 with a 4” bit with a drill press. Bought this to get that extra 2 inches and didnt realize the extension head wouldnt go into that small of a hole so totally useless. Kept because it is otherwise a fine tool at a good price. Just use your noggin unlike me🤪
DonaldJOH
Reviewed in the United States on April 30, 2022
The extension is sturdy and holds the Forstner bits securely. The first time I used it I did lose one of the set screws in a pile of shavings, but found it with a magnet. Since then I have made sure both set screws are tightly in place. With the 5.6” this adds and the 2.25” of the forstner bits I can drill holes almost 8” deep. Since I rarely have to drill more than 6” it works well.
Bufflochip
Reviewed in the United States on June 14, 2020
The extender is well machined but does not fit all 3/8" bit stems. If you have an existing bit that has any scratches or burrs on it, these will need to be filed or ground off. There is no tolerance. Some bits fit very nicely but others will need to be ground. Seems like there is not an exact standard for the shaft on bits. Out of the 10 I had, at least half required grinding, a few fit perfectly and some a little loose.
Mike P
Reviewed in the United States on April 26, 2019
I have a grizzly 31 piece set and I wasn't sure which extender would work. Grizzly customer support told me they didn't even have anything but it existed online somewhere. Pretty helpful.I took a chance on this and it works really well.This thing is very sturdy and a lot bigger than I expected. Has two fairly standard screws built in along with a little hex key. I recommend duct-taping a few small magnets (or a long skinny one) to the shaft to hold the key so it doesn't get lost. At standard forstner bit speeds its not going to create wobble or fly off.If using hex shanks you will want to rotate them so that the screws when tightened will be flush with the hex face. In other words don't tighten down on the sharp edge of the hex shank obviously. I was a bit worried the screws wouldn't go in far enough to properly secure a hex-shank, but this was not an issue at all.Once secured, I had no trouble drilling 7 inches in.
Recommended Products
$124.99
$ 60 .99 $60.99