I need to take a .25" ID preformed cork grip and open it up to around .40" so I can get my reamer in it and I also need to drill out a butt cap. I assume that I don't want to remove it all in one shot. How much cork would you advise removing at a time with a drill bit?

Thanks,
Joe

The flex coat reverse cutting spade bits will do the job better than just about anything else. They feature a pilot tube that keeps the bit centered in the standard 1/4 inch bore.

You can do with it the method you suggest but I wouldn't attempt to enlarge the bore by more than about 1/8 inch per pass using a regular twist drill bit.

.............................

Joe

I know its time consuming but to play safe I would start with the17/64 drill and then use the next size drill until I reach the hole size needed. By removing the minimum amount of material the drill bit will tend to keep centered in the hole. Doing this will be the safest way to keep the hole in the cork straight and concentric with the OD especially if you are drilling by hand.

If the grip is longer than the drill bit you can drill from both ends and meet in the middle, by removing the minimum amount of material each pass helps keep the hole straight and concentric.

Good luck

John

Joe,
Rather than using a drill bit, use a circular file, and run the drill backward to avoid having the spiral of the file screw the file into the cork and split the cork.

Rather, run the drill backward and force the circular file into the cork, filing out the cork for a dead smooth hole with no ripping or chopping of the cork.

If the file is smaller than your needed hole, you can just use the file in a rotary motion to enlarge the hole as needed.

A picture of the files that I have cleaned up for use as needed to ream out cork pieces and grips. Note the sharpened end of the files, as well as the turned down ends on the file.

To turn down the ends of the file, I run the file through the chuck on my lathe, and then use a grinder on the file as the lathe is spinning the file to change the angled handle that is normally part of a circular file to fit the chuck on my portable drills.

I find that I have better control, by using a variable speed drill held in my hand running backward to ream out the cork. Normally, I keep the drill running at a rather slow speed. It usually does not require a high speed to get the cork reamed as needed with the circular files running backward.

[www.rodbuilding.org]

If I need to make a hole in a blind end butt cap, I will do as posted above with a pilot drill bit and often will drill the hole with the drill bit running backward to avoid tearing up the cork.

For some cases, I will grind the end of a drill bit completely flat, and then put a very mild reverse cutting tip on the drill bit and run the bit backward. The drill bit will still cut, but with the bit running backward, will not pull itself into the cork and possibly rip up the cork.

Be safe

I drill out holes in cork all the time Just find the bit that fits the hole then go only one size larger on each pass Take it slow

Bill - willierods.com

Insert a piece of arrow shaft or some similar sort of tubing into the cork and drill the cork out with a suitable size butterfly bit. The tubing will be pushed through the cork while maintaining center, the same way those expensive pilot bits do. Lynn

The reverse spade bitts are the way to go. I suggest you go to HomeDepot and get the Irwen 16" spades and make them your self.

Dennis J. Danku
(Sayreville,NJ)

What size shaft do the Irwin bits have? Are they small enough to fit the 1/4" hole?