Counter Bore Problem

L6steel

L6steel

Joined
Sep 23, 1999
Messages
5,855
I use 2-56 button head screws to hold the bolsters on folders. I bought some counter bores supposedly for a size 2 screw head but when I started putting the bolsters on the screw heads wouldn't go in the holes. I ended up wallering the holes out a little and finally got the screws to fit but it was a p.i.b. for sure. I got the screws from Halpern and the bores from MSC.
Do you guys use metric counter bores for button heads? What size counter bore do I need for a #2 button head? Thanks!
 
I have a counterbore for 2-56 that works for socket head, but is too small for button head. I guess we have to measure head diameters, and shop around.
 
The problem is not the counter bore but the way they make the screw heads....they are formed...and thus squished to shape, and are not round......therefore...they dont like to go in a round hole as somewhere it is wider than your hole tolerance.....you can: use a slightly larger drill and grind it into a counter bore or : put your screws in a little chuck and stick them on your grinder with a dull 400 grit belt and make them round.......dont have any other ideas, sorry.
 
I have done what Tom Mayo says: put them in a small chuck and spin the head smaller on the grinder. Very carfully. Use a caliper to measure each one.
 
If you want a flat bottom for the 11/64 take another 11/64 and grind it to almost flat. You can then use this to level out the bottom of the screw hole. This will work on metal as well as other materials. Frank.
 
On the pricey side, you can get CBs with interchangable pilots. This way you use the appropriate pilot dia for your hole, and a larger size for your fastener. They are available from your favorite Industrial Supplier.

Another option is to regrind a larger CB. I frequently grind the pilot dia smaller for a tighter fit on the full body of the bolt. Maybe get a #4 or #6 CB and regrind the pilot for a #2 clearance hole.

No resources for regrinding...? Check with a local tool sharpening guy,..... the guys that resharpen saw blades, drill bits, endmills...etc.

Hope this give you some ideas.

Sincerely,
Rob
 
Mike
Yes Counter bores are a big problem.

A suggestion would be to call Mick Koval.

Have a drill made that is the right size with the ctr bore as the big size (step drill)
This way you are drilling the hole and crt bore all in one shot and the two holes will stay concentric with (and on size) each other after drilling.
Mick has these made up for a pretty fair price .

This will save you time and parts !
 
DDR strikes again!!

That bit of info actually made the most sense of any tip I have heard in a long while. Using a fabricated step drill is a great idea. One hole, no guessing, and exactly the same every time. I guess the KISS theory really works.

Thanks:)
 
Now I can use that box of slotted button heads. :cool: ideas. Thanks to all.
 
I've also turned down screw heads on my lathe!

You just need to get (or make) a standoff to hold the screw. A "C" style cutter usually works best. No more "wobbly" fits with uneven gaps! Just set it up and run a batch! :D

(My apologies to the "lathe challenged.":p)
 
First of all ask yourself this. Do I like that big ole button head takin' up all that space on my purty bolster? Personally I'd rather see bolster catch my attn. more than the screw keeping it there. Bigger ain't always better, you'll get more TPI out of a 1-72 or even a 0-80. Just my opinion. As to how I cured my counterbore blues, I calipered the screw head, got a # drill just a couple thousands over, screw machine length, just barely grind off the point,meaning don't grind away any more than the size of your clearence hole, stay under that. Now take a 62 degree single flute counter sink(less chatter) and counter sink your hole no more than the size of your # drill. What this does is a counter sink centers itself in the hole, thus when you come down with the # drill it centers itself in the counter sink. Oh, the reason you grind off the point is so that at the bottom of the counterbore remains relatively flat and not so much of a point, leaves more meat.
 
Yikes, 1-72 or 0-80 screws scare me!! So far I'm using one torx driver per folder I make cause I twist the splines on em, and thats with a 2-56. I really don't try to over tighten them, I just snug them down.I would probably twist the head off 1-72's and the 0-80's look so tiny I don't see how you can put he driver in the head of them. :) I'm fixn to order some 2-56 socket head srews and will give them a try. Thanks guys!!!!
 
You must log in or register to reply here.
Back
Top