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 Post subject: Countersink drill bit size
 Posted: Mon Oct 23, 2017 4:31 pm Post Number: #1 Post
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Hi there,

I'm looking for a cone cutter/countersign drill meant for making the top part of the thumb hole wider than the middle and bottom. What size drill bit should I be using? Drilling the top bit bigger with a different size standard drill bit doesn't work well for me, so I'm looking at the cone cutters instead.


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 Post subject: Re: Countersink drill bit size
 Posted: Mon Oct 23, 2017 8:32 pm Post Number: #2 Post
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Have you considered a bevel sander. It should do the job.


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 Post subject: Re: Countersink drill bit size
 Posted: Thu Oct 26, 2017 2:39 pm Post Number: #3 Post
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Not really, due to the fact the top of my thumb is really narrow and the base is quite thick. The bevel sander would take a rather long time.


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 Post subject: Re: Countersink drill bit size
 Posted: Thu Oct 26, 2017 3:38 pm Post Number: #4 Post
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A large diameter countersink could work, but might be grabby. Find one with 6 or 8 flutes and it might help. I use a tapered step drill in a cordless for quickly removing bevels prior to plugging.

I use a lot of bevel and my own preference is a 3 sided bevel knife + hand (or power) sanding. You can remove a lot of material quickly with a sharp knife and there is very little sanding. Rasp or riffler will also work.

Machinist swivel headed deburring tools do a nice job of knocking an edge off. Easy to control and work well in plastic, but not for aggressive material removal.

Although I've never tried this, you might hog off a bunch of material quickly with a laminate trimmer and a bearing guided round over or chamfer bit.

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 Post subject: Re: Countersink drill bit size
 Posted: Fri Oct 27, 2017 6:40 am Post Number: #5 Post
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I am not a fan of using a bevel that is equal on all sides of the hole. I want to modify the edges on all sides according to my thumb shape which is not a cone by all means. :lol:

I have found myself using normal scissors the most. Those cheap ~3" long ones similar than most have in their bowling bag for cutting tape etc. It is very easy and accurate to scrape material off from the edge of the hole by using only one side of the scissors. Plus I have one always with me so i can modify the bevelling when I am on the lane. Sometimes I use the tip of the all-around knife to take more material out but this requires some practice to use without taking too much material off.

I have also one 10$ very small chinese dremel copy that is variable speed. Then I have a dremel-kind of milling bit on it. Easy to take a lot of surface off fast and accurate. I also have dremel but this is a lot smaller and uses lower rpm's. It actually says nail drill or something on it.

Finally I use bevel sander to smoothen all edges out. Or if I am on a trip, I sand the edges with a strip of smooth sandpaper. I have used the bevel knife which is a good tool, but I have found myself using these DIY-methods more.

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 Post subject: Re: Countersink drill bit size
 Posted: Fri Oct 27, 2017 1:12 pm Post Number: #6 Post
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Peeku wrote:
Not really, due to the fact the top of my thumb is really narrow and the base is quite thick. The bevel sander would take a rather long time.


Given if you just want a bevel at the top of the hole the info given so far is okay.

But to me what it sounds like what your wanting (or need) is a tapered thumb hole, since you say your thumb is narrow at the tip and gets wider at the base.

You should measure your thumb in 3 places (Base, Middle and tip). Then drill the appropriate size and depth hole for each segment then smooth the transition's with a bevel sander.

Attachment:
taper.gif


You might also take a look at this wiki article:

How and Why To Use a Two-Stage, or "Stair-step" Bevel
http://wiki.bowlingchat.net/wiki/index.php?title=Two_Stage_Bevel


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 Post subject: Re: Countersink drill bit size
 Posted: Thu Nov 02, 2017 8:34 pm Post Number: #7 Post
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I have several full-size cone-shaped grinding bits of various diameters for this purpose.
I use them on a hand drill rather than on the mill.

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