Pivot Pin problems

SVanderkolff

SVanderkolff

Joined
Oct 31, 2002
Messages
979
Okay, I thought I would try, once more, to make my first folder. I took apart a little CRKT that I had to see how it was made. I figured it had to be about the simplest folder around. 1 blade, 1 back, a pivot pin, a stop pin, and a detent ball. Should be simple. So I surface ground a couple of pieces of 440C, removed any burrs that were generated in cutting them, and clamped them together. Measured for the exact location of the pivot pin and marked it on the steel with the dykem. The pivot pin measured .1225 so I spent a fair bit of time squaring up my mill and inserted a 1/8 or .125 end mill into it. Squared up the steel in the mill and drilled the hole. When I inserted the pivot pin in the hole though, it was really sloppy . I am pretty sure this needs to be a very close fit. So I measured the hole that my .125 endmill made and lo and behold it was .130. SO I now have a .130 hole and a .1225 pin. Not going to work. So I got to thinking, what do I have around the shop that might fit better in the hole. I have lots of 1/8 pin stock so I measured that. It all turned out to be .1225.

So my question is, what do I use to make a hole that will give me a tight fit on a .1225 pivot pin, and why did my .125 endmill give me a .130 hole? And how do I fix it?

Thanks for the help
Steve
 
If it was me I would go up to 9/64 = .1408 and as for as why did it drill .130 there
are several things, warped bit, burr on the bit ,not chucked true dunno. Good luck !


Glenn Dykes
Louisiana
 
There was a whole discussion about the perfect hole a bit back. But, I have a numbered drill set. I uses some stock to drill and test different bits until I got a good fit for my round stock. I used round spring stock for my pin material and after I got a tight fit I lapped the hole with a bit of polishing compound and a piece of the pin stock. It worked for me on the 4 folders I have done. Maybe not as perfect as some who used a reamer. Now that your hole is big you could get a bit larger stock. Good luck. The satisfaction from making a good folder is great.
 
Get a larger pivot pin to fix this one mess up.

Don't drill precision holes with an endmill.

Drill under size with a drill bit and ream to size.
 
I will simply toss this one back in the scrap bin. Going to try a #31 drill and a 1/8 reamer on the next one.
Steve
 
Also drill bits are not created equal. I always drill a scrap piece first for a test. If you use number drills and go undersize you can easily ream it for a perfect fit.

Holes are the hardest thing to do. Its almost impossible to drill a hole straight down too because the bit wants to flex. Hint, buy short drill bits.

I dont have any but they make a combination drill and ream in one bit. Pretty handy I bet.
 
Steve for a 1/8" pivot I drill the hole w/ a .120 diameter and then ream to .125. One pass thru w/ the reamer as it cuts on each pass. I use liners, so I make the liners, drill two location pin holes and ream them. I put the pins in the two liners together then drill and ream the pivot hole thru both liners while they are pinned.
 
I'd call Daryl at Knifekits or someone else and get a pivot barrel with a bushing and redrill for the bushing in the same hole probably. You might be able to find a 7/32 bushing that will allow you to try again and then insert a 3/16 or 5/32 barrel or whatever size it comes with in the bushing that way.

STR
 
"Center cutting" end mills don't really like to be plunged. So they wobble and make oversized holes. Even in a big mill.

When plunging in a work piece, I always plunge away from the finished part and then feed over to the part, otherwise you get a gouge from the plunge.

If you would have predrilled the hole to just under and then chased it with the .125 EM, you'd have got a good hole.

If not, you have a lot of runout in your spindle/tool holder.
 
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