oversized drill bits

H

Hesparus

Joined
Oct 31, 2004
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I've been using 1/4" thong hole tubing on some of my knives lately, purchased from a couple of different knifemaking supply companies. The problem is that the tubing is slightly too big for the holes drilled by my 1/4" drill bits. I've been taking a little bit off of the outside of the tubing with my grinder, but it's a pain in the ass to do and it's never as accurate as I'd like it to be. Is there anyone who makes drill bits that are oversized by a couple of thousandths or another way I could solve this problem?
The same goes for the corby bolts and step drill bit I bought from texasknife.

Thanks,
Chris
 
Buy yourself a set of letter and number drills to go with your fractional set and you can pretty much get the size you need.I'm not sure if harbor freight carries them or not. Check out your local Grainger store.
 
I agree, try an F at .257 for oversize on .250

Try measuring each thing, the nominal sizes are meaningless vs the actual measurement



See the chart on this thread

http://www.bladeforums.com/forums/s...looking-for-some-drill-bits-question-on-sizes


You can get a drill at any of those sizes, fractional inch, letters, numbers, metric,

Enco, macmaster call, MSC any of those types of suppliers will have it.


If that dosent' do it.
You can also get a reamer in dowel pin decimal inch sizes
basically every graduation of .001"
 
I've measured both the thong tubing and the corby bolts and they come out at 0.250". With the same drill bit, the tubing will often go through the hole in the tang but not the hole in the scale material (which I drill with the same bit).

- Chris
 
Yep, an F should do it. Works for me anyway. I was initially worried that the difference would be noticeable on the scales, but it's a perfect fit in my case.

IMAG1537_zpsa3c4f6ab.jpg
 
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F for 1/4" and #30 for a 1/8th. these are the two most common sizes I use. they fit perfect.
 
You can order oversized drills from mcmaster in half thou increments if I remember right, if you'd like to tune it in farther than moving up to the f size.

A trick with sanding the od is to Chuck the piece up in a power drill and spin it while you sand. If you do it in longer sections, use a fine grit belt over a flat platen or wheel (so the belt surface is flat/parallel to the wheel axis), and check with calipers a lot, you should be ok. Take a light touch, pay a lot of attention to angle, and watch finish change on the od for clues to your angle. If you use a light touch you can get pretty darn straight and true doing this (a lot closer than the seven thou difference with an f drill)

The reverse method to the above is chuck the tube up in the drill press and spin it in strips of sandpaper. Just be careful not to wrap the sandpaper up, or your fingers. This is probably better depending on how lucky you are doing weird stuff like above.

Either way should take a few minutes and solve your problem until you get the drill issue figured.
 
I like a .251 reamer to open up (and make round) a 1/4" drilled hole. If it's still a little too snug a match stick squashed into one of the reamer flutes will make it cut a tad bigger too.
 
I'm a dummy when it comes to this drill bit stuff, but if you weren't having any luck with the grinder, you could maybe chuck the tubing in the drill press, and dress the outside of the tube with some abrasives or a file in a pinch.
 
Nathan the Machinist said:
I like a .251 reamer to open up (and make round) a 1/4" drilled hole. If it's still a little too snug a match stick squashed into one of the reamer flutes will make it cut a tad bigger too.
Click to expand...

Maybe I subconsciously neglected to mention reamers because I'm embarrassed that I'm supposedly a professional machinist but barely own any?

Either way, this is the ultimate option. Bonus points for half thou increments from .249" to .252" :D
 
Thanks for the advice, everyone! I'm leaning towards the reamer. If I wanted to limit the number of these that I buy, what size do you recommend I start with?

- Chris

ETA: also, would the tapered end of a reamer prevent me from using these on holes for corby bolts?
 
Strigamort said:
Yep, an F should do it. Works for me anyway. I was initially worried that the difference would be noticeable on the scales, but it's a perfect fit in my case.
Click to expand...


It depends on the individual, but a hairsbreadth for me is in the .002 or .003" range

It makes the difference between fit and not, but it's hard to see.
 
Hesparus said:
With the same drill bit, the tubing will often go through the hole in the tang but not the hole in the scale material (which I drill with the same bit).
Click to expand...

Especially with wooden scales, the hole will tend to close up a little bit when you back the drill out. Just enough to irritate you...
 
Harbor Freight sells adjustable reamers, but I have no idea if they're functional or not.
 
I use 1/4" thong hole tubing in my knives. The tubing I'm using right now actually measures at .252" on my calipers. I use a 9/32 bit through the tang for ease of assembly during glue up and a 6.5 mm bit for the handle material. It works great for this particular tubing.

Keep in mind that pins and tubing will always vary a couple thousandths between suppliers. I like to buy them BEFORE deciding what bits to use. I measure them with calipers and go with the next size up in decimal/wire/letter/metric for handle material. I've been buying all of my bits from ENCO lately. They frequently run special email promos (if your signed up) that give you free shipping on your order.

Here's a link I use for a quick reference when trying to decide which bit would work best. http://www.csgnetwork.com/drillsizeconvert.html
 
12345678910 said:
It depends on the individual, but a hairsbreadth for me is in the .002 or .003" range

It makes the difference between fit and not, but it's hard to see.
Click to expand...

Ah, yeah I imagine the run out on my cheap press would hamper my quest for ultimate f&f. :(

So far none of my customers (they being me :D ) have complained. ;)
 
For a 1/4 oversize hole use a 6.40 metric bit which is 2 thousands larger and for a 3/16 hole use a 4.80 metric bit. I also keep a small box with numbered machinist drills that are the next size up for 1/8, 5/32, 3/16, and 7/32. I keep each drill in a tiny plastic bag with the size marked with a Sharpie pen. Lastly I use a Dremel bit that looks like a chainsaw sharpening stone and lightly circle the tang hole until the pin material slides through. The scales need to be slightly snug though. I hope this helps you. Larry Lehman
 
This is what I use....

3/32" use no. 41
1/8' use no. 30
5/32" use 4mm
1/4" use 6.4mm

(5/32" is 3.96875mm. 1/4" is 6.35mm.)

The metric bits can be ordered at any most any industrial tool supply such as MSC or Enco.

Craig

Edited to add: Sorry Larry. Just saw your post above. Didn't mean to repeat anyone.
 
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