quarter inch hole not big enuff for a quarter inch pin

M

manassas dragon

Joined
Dec 3, 2009
Messages
158
experts,do you use an oversize bit to drill a slightly oversize hole so the pin will go thru it? i've been taking a rattail file to enlarge the hole but there has to be a better way.
 
If the pin is actually .250" (never take that for granted - we all know what assume stands for ;) ), yes you need a slightly bigger drill bit. The other way is to turn the pin down slightly, but buying the next size bit is much smarter. Size F is great for 1/4" pins/bolts, 17/64" also works. Size G is between those two.

Here's a table comparing drill sizes.
 
Also realize that a pin is rounder than the hole a drill bit makes. Even high quality bits will still drill a slightly oblong hole.

What you need is a chucking reamer. When I drill for a 1/4" pin I use a slightly undersized bit for the "pilot" hole say 15/64" or even 7/32" and then follow with my 1/4" reamer. This will give you a circular hole that will tightly fit your 1/4" pins. But as always, it's a good idea to check how big your pins ACTUALLY are, hence why calipers are so useful.

http://usaknifemaker.com/drills-taps-saw-blades-c-98/tap-reamer-counter-sink-bores-c-98-32/chucking-reamer-hss-1-4.html

HSS reamers are fine if you are just doing handle material, cobalt/carbide are more expensive and are really only needed if you will be reaming steel or titanium.

Happy drilling!
 
Woah, I had no idea there were so many fine graduations between the 64ths!
I take a rod of my pin material and gently sand it down until it fits. Usually I use a 220g slack belt. Then I hand-sand it lengthwise a few strokes to put the scratch pattern inline with the insertion force. A light scratch pattern should also help hold epoxy. This only takes a few minutes.
 
Since I buy my drill bits locally at a little home improvement store I'm stuck with 64th increments. I usually use 17/64ths for 1/4 and 9/64ths for 1/8th pinstock. They are a little loose but not much and it gives you a little room to make sure the handles and blade are lined up perfectly. One thing that I have been considering is that I could epoxy everything up and then peen the pins while the epoxy is wet. I haven't tried that though.
 
Victor Machinery Exchange out of Brooklyn NY has most any size undersize drill bit and ream combination. If the round stock you are getting is not as advertized buy from someone else; 1/4 inch should be 1/4 inch.
 
I asked this same question after strapping 3 solid carbide 1/4" bits drilling through 1/4" holes after H/T. Daniel Fairly told me to use an F and I haven't looked back.
 
I have had the same problem. I just buy drill bits from McMaster-Carr. They deliver, fast, and not too pricey. Good drill bits are cheap and as advertized. I like to buy boxes of 1/8" copper nails and clip the heads off for pin stock. They are not perfectly-sized but about 3 thou under. There is some variability from nail to nail, a thousandth or two. But, it is a cheap source of good pins. Get 4 or 5 drill bits of the size you need from McMaster-Carr and you will be set. I buy so many because I sometimes am too lazy to do a spheroidizing anneal on my W2 and carbides wear the drills out fast.

calipers and a plan are all you need to make this problem go away. Plus, copper peens so wonderfully to fill the hole and chamfer.

good topic,
kc
 
Just a side note;
There is no reason the hole for the pins needs to be all that snug. I drill pin holes 25% oversize. This allows for mis-alignment of the front and back holes, as well as the pin stock size. A 1/4" pin in a .315 hole only has .03" clearance ( much less than 1mm). The epoxy will secure it solid.
 
I run the drill up and down through the hole a few times to clear it. Then take the pin and use a piece of 320 grit to hand polish off any irregularities from the pin before inserting into the hole.
 
In a pinch you can take a thin rag such as bed sheeting and fold it then place over the hole and re-drill the hole this will act similar to a boring head, on a much smaller scale and give you a very slightly larger hole.

images
 
Karl B. Andersen said:
You are surrounded by Fastenals. They'll have every drill bit you'll ever need.
Click to expand...
I've almost given up on advising people to check the suppliers like Fastenal, Grainger, MSC, Enco, etc. As you say, there's at least one of those in an hour's drive of almost anywhere.

So many people love Harbor Freight, but so few want to spend a couple dollars more on professional tools. :confused: And yeah, when it comes to drill bits, a few extra bucks goes a long way.
 
Our local Ace hardware store carries the # bits (you'll want a #30 for all your 1/8 inch pins) and a few of the letter drills including the F. So check around locally, they are there.
 
K&G also sells bits that are a few thousanths oversize for this purpose.
 
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