need help with counter bore

A

AJH_Knives

Well-Known Member
hey guys, i want to sink my pivot screw into the handle material a little bit. i am using a 3/16" pivot and my pivot screw head is .290" where can i find a counter bore that will work for me?
 
AJH_Knives said:
where can i find a counter bore that will work for me?
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You can't. You can have one custom made for around $100 from tool companies like Harvey Tool or you may be able to find a skilled tool grinder in your area that can re-purpose something like a twist drill to meet your needs. The other option, which I use frequently, is to use a 3/16" dowel pin to align your handle scale to the spindle on a mill, clamp the scale securely, and then counterbore with the appropriate size endmill. I do not recommend trying this with a drill press as the runout is too great and the counterbore will be sloppy.

Bob
 
First thing first.... Enjoyed meeting Bob at the show!

I'll come at this from another angle.....use the closest undersized counterbore you have (one that is slightly small then the screw head you want to use).... THEN.....put a folder pivot in a drill (like a cordless drill), the screw into the pivot, then flip on your belt grinder and "turn" the head of the screw down to fit the counterbored hole. :) I've done that more times then I could count. :)
 
I've got a mill, albeit not the greatest or most rigid, but I've had bad luck with plunging a mill down for a pivot pocket. It almost always makes the hole slightly egg shaped. Not a lot, but enough I can see it. Out of frustration I've even put bolster and handle material in a 4 jaw chuck on the lathe and made the pockets.
 
If you use an endmill it needs to be a centercutting variety or it won't plunge cut well at all. I don't know if that was your issue Anthony, but I thought I'd throw it out there just in case.
 
EdCaffreyMS said:
First thing first.... Enjoyed meeting Bob at the show!

I'll come at this from another angle.....use the closest undersized counterbore you have (one that is slightly small then the screw head you want to use).... THEN.....put a folder pivot in a drill (like a cordless drill), the screw into the pivot, then flip on your belt grinder and "turn" the head of the screw down to fit the counterbored hole. :) I've done that more times then I could count. :)
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More excellent advice! Really enjoyed talking to you Ed. I was a little disappointed when Karen and Jerry stole me away from your table but, I did step aside and write down all the great advice you gave me. It will be put to good use.

Bob
 
I'm running into the same issue with some Timascus I'm using to make a frame lock. Don't have a mill and have the 3/16 pivot from AKS. Been trying to find someone near me who has a mill I can use or just get a counter bore and do what Ed suggested. Bob, let us know and see how it goes with your counter boring.
 
Are you guys trying to counter bore the pivot barrel itself into the backside of your bolsters or scales? I guess I'm not understanding the issue. I have counterbores for several sizes of pivot screws and I've never had any issues.
 
I think the OP and I are talking about the same thing, here's a pic of one I'm working on. Some of these pivots are metric I guess, on this one I didn't have an endmill close enough to this size. Trying to get a pocket milled in the bolster/handle material so the pivot sits flush is what we're talking about. I think?
bolster recess.jpg
 
Self Made Knives said:
I think the OP and I are talking about the same thing, here's a pic of one I'm working on. Some of these pivots are metric I guess, on this one I didn't have an endmill close enough to this size. Trying to get a pocket milled in the bolster/handle material so the pivot sits flush is what we're talking about. I think?
View attachment 55291
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That is correct. I'm also referring to this as well. Pivot pin is 3/16 diameter where the blade fits, and the pivot pin(collar?) is 3/8 or .375" where it needs to be recessed in the titanium handle material
 
You can buy the exact size counterbore (or a few thousandths larger usually) as your screw head from Enco. They have interchangeable pilots. Buy a pilot with a smaller diameter than your pivot screw shaft. For example: My pivot screws measure .305" in diameter. That seats pretty nicely in a 5/16" diameter counterbore hole which is .312". The diameter of the screw shaft on the pivot is .135". That's about a #29 drill which is .136"

Now you're probably not going to find a #29 pilot for your 5/16" counterbore. BUT you can easily find from Enco a 1/8" pilot, which we all know is .125".

So, I buy a 5/16" counter bore with an 1/8" pilot and a #29 drill from Enco. Now, I can locate my pivot hole and drill it first with an 1/8" bit. Next I run my 5/16" counterbore with 1/8" pilot in the hole to counter bore my screw head pocket to the desired depth. After that's done, then I can go back and open up the 1/8" hole in the middle of my screw head pocket with the #29 drill and now the screw shaft goes in no problem and the head fits in the perfect counterbore pocket all nicely centered. Done deal, easy as that.
 
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