Tapering pin holes

[OLDE CUTLER]

I have done a few conversions of shell handled knives such as the Kamp King, to conventional brass liners with nickle silver bolsters. When making the new bolsters, it is necessary to taper the pivot pin holes before riveting the pins to have a place for the displaced pin to expand into and lock the ends securely. I have done this in the past by using the drill bit required for the correct pin size in the cordless drill and with the bolster clamped to a wood block, I just wobble the drill in a small circle to make the outer diameter of the pin hole somewhat larger that the main portion. However I am not entirely satisfied with this as it is difficult to make it uniform from hole to hole. I know what you are saying, "why don't you just get a tapered 3/32" reamer from Jantz?" Well that is probably what I will do the next time I order. Sometimes though a 3/32" will not work as some pins are smaller than that. I found a diagram in the knife repair book by Adrian Harris that shows the hole countersunk at what appears to be 45 degrees.

I was digging around in my Dremel tool box and came up with a couple of other bits that I had forgotten about. One is a mini countersink tool with a sharp angle and the other has a more gradual taper. They are both 1/8" shank and I would turn them by hand with a pin vise. Is a gradual taper better that a steeper one for this?

[muskrat man]

In my experience the steeper taper is more difficult to get a seamless invisible pin job on. Factory holes seem to be more gradually tapered which is what I do.

[jerryd6818]

A countersink works but another choice to consider is a broach. They come in various sizes and taper all the way to the tip.

[orvet]

In my experience the steeper taper is more difficult to get a seamless invisible pin job on. Factory holes seem to be more gradually tapered which is what I do.

I agree with Kaleb 110%!
Where I do use a wider and therefore shallower taper is on the back side of the liners. It's necessary to make an indentation there, provided one does not already exist, so that there is enough of the pin on the inside of the liner to keep the handle pin from pulling out when the knife flexes or is dropped. If the handle pin is close to the blade pivot the tang of the blade usually passes over the top of the rivet. If the rivet is not recessed down in the liner, it can definitely cause the blade to bind every time it goes over the liner. It really kind of kills the walk and talk of the blade.

These are the tapered reamers I use for pivot pin holes.

This is the reamer I use 90% of the time to put taper in the pivot pin hole. The two reamers are the same, I just modified the end of the old-style chuck used with a brace and bit. I think this reamer was originally made to work in a hand turned brace. I modified the end so I could clamp it in this handle and it works great for 90% of the pivot pin holes I need to add taper in.

I have a few other reamers, the top one here is a broach that JerryD sent me. TYVM Jerry! I have a couple other broaches Jerry sent me for even smaller holes which I encounter once in a while, usually on a very small knives.
The bottom reamer is one I use occasionally, it works well to add taper to a 1/8" hole.

If I had to rely on only one reamer for pivot pin holes it would be the one in the upper picture. I found that top reamer several years ago on eBay, (I got a couple in case one breaks). My personal preference is not to use powered reamers because they will often tend to pull themselves into the hole, especially if there's any twist to the cutting-edge, and this can result in cutting the whole deeper, and perhaps even larger in diameter than you can use.
I think in one of Wayne Goddard's books he has a picture of a device he made using a conical Dremel bit so that he could taper pin holes by hand without using power tools. He used a wider hole because in general he made fixed blade knives and was wanting to provide a recess to peen the pin into. I have a couple of the wider reamers I use to recess a rivet into a handle. If anyone's interested I'll take pictures of those in post them.
But I never use the wider reamers for pivot pin holes because it is very difficult to get a good invisible pin in the bolster as Kaleb mentioned.

[btrwtr]

I've never bothered to taper a pin hole. Using a slacker to keep the blades from binding and peening the pin into the square shouldered bolster hole has always worked well enough for me. I make sure the drilled bolster hole is clean and dry. I have at times lightly scored the inside of the drilled hole with a rotary file to make the fit more secure. I believe the action of peening and swelling the pin end itself tends to create a taper in the hole. I normally have good success at completely hiding the pin and getting a tight and snappy fit on the blades.

[OLDE CUTLER]

Thanks for all the comments and advice. I am learning from the best!

[orvet]

I believe the action of peening and swelling the pin end itself tends to create a taper in the hole. I normally have good success at completely hiding the pin and getting a tight and snappy fit on the blades.

I see the logic behind what you're saying Wayne, it's just that it never seems to work for me that way if I forget to taper a pivot pin hole. Seems like every time I forget to taper a hole I end up with a sunken pin, where the pin pulls into the bolster. This seems to be a problem especially with steel bolsters.
Have you encountered this problem, and if so how do you address it?

[btrwtr]

I believe the action of peening and swelling the pin end itself tends to create a taper in the hole. I normally have good success at completely hiding the pin and getting a tight and snappy fit on the blades.

I see the logic behind what you're saying Wayne, it's just that it never seems to work for me that way if I forget to taper a pivot pin hole. Seems like every time I forget to taper a hole I end up with a sunken pin, where the pin pulls into the bolster. This seems to be a problem especially with steel bolsters.
Have you encountered this problem, and if so how do you address it?

Steel can be much harder to work with for sure. When peening a bolster pin I usually end up going in incremental steps. I try to leave the cut and sanded flat pin head at what I think is the proper length above bolster before I start peening. Using a feeler gauge type slacker I peen the pin on both sides, remove more of the pin by sanding, peen, sand, peen, sand in succession. Of coarse checking the blades for snap and binding as this is done. I will often change to a thinner slacker as I do this and the number of times I do this is all by feel more or less. The trick, as I see it, is to swell the pin at the ends forcing it to expand as much as possible to the point of actually pushing the pin hole wider as you peen. Leave the pin to short to begin with and you won't get enough expansion. Leave it too long and you may end up actually bending the pin and ruining the effort. I've learned most all of what I do by trial and error. I'm sure there are many ways to skin this cat but this is what seems to work well for me.

[Reverand]

The first (and only) time I made a bolster for a knife, I didn't ream the holes. I thought I could peen it and swell the pin enough to stay.
The pin sunk in and the blade started wobbling when I sharpened the knife. I had to punch the pin out, ream the holes, and peen in a new pin. I used a tapered Dremel bit, but after seeing what you guys use, I will be switching to a hand-powered reamer.
Still, I am now a believer in tapered pin holes!

[OLDE CUTLER]

In my experience the steeper taper is more difficult to get a seamless invisible pin job on. Factory holes seem to be more gradually tapered which is what I do.

I agree with Kaleb 110%!
Where I do use a wider and therefore shallower taper is on the back side of the liners. It's necessary to make an indentation there, provided one does not already exist, so that there is enough of the pin on the inside of the liner to keep the handle pin from pulling out when the knife flexes or is dropped. If the handle pin is close to the blade pivot the tang of the blade usually passes over the top of the rivet. If the rivet is not recessed down in the liner, it can definitely cause the blade to bind every time it goes over the liner. It really kind of kills the walk and talk of the blade.

These are the tapered reamers I use for pivot pin holes.

This is the reamer I use 90% of the time to put taper in the pivot pin hole. The two reamers are the same, I just modified the end of the old-style chuck used with a brace and bit. I think this reamer was originally made to work in a hand turned brace. I modified the end so I could clamp it in this handle and it works great for 90% of the pivot pin holes I need to add taper in.
Tapered Reamers a.jpg


I have a few other reamers, the top one here is a broach that JerryD sent me. TYVM Jerry! I have a couple other broaches Jerry sent me for even smaller holes which I encounter once in a while, usually on a very small knives.
The bottom reamer is one I use occasionally, it works well to add taper to a 1/8" hole.
Tapered Reamers b.jpg


If I had to rely on only one reamer for pivot pin holes it would be the one in the upper picture. I found that top reamer several years ago on eBay, (I got a couple in case one breaks). My personal preference is not to use powered reamers because they will often tend to pull themselves into the hole, especially if there's any twist to the cutting-edge, and this can result in cutting the whole deeper, and perhaps even larger in diameter than you can use.
I think in one of Wayne Goddard's books he has a picture of a device he made using a conical Dremel bit so that he could taper pin holes by hand without using power tools. He used a wider hole because in general he made fixed blade knives and was wanting to provide a recess to peen the pin into. I have a couple of the wider reamers I use to recess a rivet into a handle. If anyone's interested I'll take pictures of those in post them.
But I never use the wider reamers for pivot pin holes because it is very difficult to get a good invisible pin in the bolster as Kaleb mentioned.

I am going to try this rig, which is a Dremel tapered reamer chucked into a home made pin vise (old drill chuck, bolt with the head cut off, and a wooden file handle). The reamer has a tendency to pull itself into the hole because of the twist on it as you mentioned, so caution will have to be used. I wonder if it would be better to chuck it into the drill press, clamp the bolster down, set the depth stop, and turn the drill press by hand while lowering the bit?

[orvet]

I am going to try this rig, which is a Dremel tapered reamer chucked into a home made pin vise (old drill chuck, bolt with the head cut off, and a wooden file handle). The reamer has a tendency to pull itself into the hole because of the twist on it as you mentioned, so caution will have to be used. I wonder if it would be better to chuck it into the drill press, clamp the bolster down, set the depth stop, and turn the drill press by hand while lowering the bit?

I think that will be fine, just make sure you don't let it bite into the bolster and start threading in. That could easily happen with a drill press, which is why I never use powered reamers for something like this. Even if the knife were in a vise and that reamer caught in the bolsters started to thread itself, I think it could even pull the bolster off the knife, especially an old knife with a loose bolster.
I know it takes a lot longer to do things by hand, however adding power makes things happen much faster, usually faster than I can react!