Looking for Forstner Bit Extension

Flute Maker

Mike
User
I am looking for a Forstner Bit Extension about 16” long at least. My Forstner bit is 3/8” in diameter….round not hex shape.... I just need to go inside of one of my flutes and sort of clean up the end of a plug in there. It would take a light touch just to remove
a small amount….It’s more of a cosmetic thing for me…not needed to make the flute play….I just know it’s not like I want it to be! Lol…..Thanks in advance!!!!

*** I have a Porter Cable set from 1/4” to 1 3/8”…. All are 3/8” on the chuck end.
I want to use the extension with this set of bits…( I may have use for the other sizes in the future)Sorry for not being clear but I didn’t say I was drilling a 3/8” hole….I’m just using Forstner bits with 3/8” shaft on drill end …. My fault!!!!
 

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Mike Davis

Mike
Corporate Member
If your Forstner has a 1/4 inch shaft and the extension has 1/8” wall thickness the total diameter is going to be 1/2” which is bigger than the 3/8“ bit.
 

Henry W

Henry
Corporate Member
I expect you may need to purchase a long twist bit - as I agree with Mike that the math does not work for a 3/8" bit/hole. If you need a Forstner bit (i.e. flat bottom hole), there may be one out there that long, but I have never seen one. Seems like you are into a custom bit here? Could a long 'custom' flat scraper (lathe tool) work? (rotated slowly in the hole).
Or if you need a flat bottom, get a long twist bit and grind the end flat.

Hope that helps.
 

Flute Maker

Mike
User
I expect you may need to purchase a long twist bit - as I agree with Mike that the math does not work for a 3/8" bit/hole. If you need a Forstner bit (i.e. flat bottom hole), there may be one out there that long, but I have never seen one. Seems like you are into a custom bit here? Could a long 'custom' flat scraper (lathe tool) work? (rotated slowly in the hole).
Or if you need a flat bottom, get a long twist bit and grind the end flat.

Hope that helps.
I
It probably would ….. I can’t see end of it though…I have one similar but it is hex shape and the 3/8” wont fit
Dont want to use a lathe tool
 

Flute Maker

Mike
User
I expect you may need to purchase a long twist bit - as I agree with Mike that the math does not work for a 3/8" bit/hole. If you need a Forstner bit (i.e. flat bottom hole), there may be one out there that long, but I have never seen one. Seems like you are into a custom bit here? Could a long 'custom' flat scraper (lathe tool) work? (rotated slowly in the hole).
Or if you need a flat bottom, get a long twist bit and grind the end flat.

Hope that helps.
I’m wanting an extension to put a Forstner bit into to make it longer…Not a Forstner bit that long….I’m sure or I would think there would be an extension for them…hmmmm maybe not…

Thanks again!
 

cliff56

cliff
Corporate Member
Have seen twist bits that size in the elec depth at lowes, they do have bit extensions don't remember shat size.
 

bowman

Board of Directors, Webmaster
Neal
Staff member
Corporate Member
Find an 'installers bit'. These are usually between 12-48", then see if you can regrind the point off of the blade tip. As mentioned before, the extension connection will be larger than the 3/8" bit you are drilling.
 

Flute Maker

Mike
User
Find an 'installers bit'. These are usually between 12-48", then see if you can regrind the point off of the blade tip. As mentioned before, the extension connection will be larger than the 3/8" bit you are drilling.
The Forstner bit set all have a 3/8” shaft…. 1/4” to 1 3/8”….. The connection where the Forstner bit goes into the extension won’t go into the flute if I can get an extension long enough plus the bit size I’ll probably use will be 7/8” which will not be hogging out any depth at all…….just cleaning up a 1/16” on a plug in a cylinder or flute . It’s just 15” up in the flute…
 
Last edited:

bob vaughan

Bob Vaughan
Senior User
Anyone moderately familiar with a metal lathe could make what you want out of a 14" piece of 5/8" diameter CR steel. One end gets bored, reamed 3/8" and then cross drilled and tapped for a setscrew and the other end gets turned down to 3/8" (or whatever).
 

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