Forstner Bit Extenders

Featuring No-Slip Hex Shanks! (10" ONLY)

See Options Below

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10" Forstner Bit Extenders #301-0107:

For use with drilling diameters over 3/4". Features hex shank for maximum drill chuck grip, eliminating bit spin-out.

Fits both hex and round shank Forstner bits.


5" Forstner Bit Extender #301-9270:

With round steel shank, for 3/8" Forstner Bits (under 2-1/4" cutting diameter). Twin locking set screws hold the bit.

Forstner Bit Speed Recommendations

Bit Diameter Max RPM in Soft Woods Max RPM in Hard Woods
1/4" to 3/8" 2400 700
1/2" to 5/8" 2400 500
3/4" to 1" 1500 500
1-1/8" to 1-1/4" 1000 250
1-3/8" to 2" 500 250
2-1/8" + 250 250

Forstner Bit Maintenance

  • Do not run your bits too fast, causing them to overheat.
  • Forstner Bits are made for nice, clean, precise holes and have limited uses in hand-drills. Ideally, these bits should be used in a drill press
  • The best way to keep your Forstner Bits clean and in good operating order is accomplished by a good drilling technique. As you bore into a piece or material, pull the bit back up to the top rim of the hole to evacuate the chips created by the rim of the bit, just the chippers. Forstner bits do not have flutes on them to remove the chips so it is necessary to do this approximately every 20 seconds of drill time.

Sharpening Suggestions

  • Most Forstner Bits come ready to use but honing the chipper will improve their cutting action and longevity.
  • Hone only the flat portion of the chipper using a diamond hone or sharpening stone. Start by using a 1000 Grit and working your way up to a 4000 Grit.
  • The rim of the bit can be sharpened using a round stone or diamond hone.
  • Remember not to change original cutting angle on your bit and keep the chippers slightly lower than the rim so that the rim cuts the edges of any fibers before the chippers remove any material.

Product Options

Description Item # Price    Qty
10" Forstner Bit Extension - 3/8" Shank 301-0107 $12.99
5" Forstner Bit Extender - 3/8" Shank 301-9270 $8.99
Backordered until 7/1/2021. Reserve Now!

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