Bolster Pins that don't show

[BossDog]

In this laughably crude drawing we'll try and figure out how to make your bolster pins not show. Like just about everything in knife making there are lots of ways to do things. If some one has any suggestions, comments, jump in!

Use the same material. Mixing 416ss bolster material with some other kind of stainless is guaranteed to have the pins show.

Use a tapered pin reamers

These create a cone shaped hole and not the typical vertical hole left by a regular reamer or drill bit.

You don't ream with this all the way. Just partially. If you need to, grind off the extra length at the tip of the reamer. You want a partial cone shaped hole.

In normal piening (peening?), most of the force from the hammer blows are vertical and depend on the pin to expand enough and blend into the metal surrounding it.
When you grind it down after piening, much of the actual blended material is ground off near the very tops of the holes.

Piening into a cone shaped hole has the force of the hammer blows smearing the metal into the sides of the cone shaped hole. This action has the pin blend into the sides of the cone. When you grind the bolster to shape after piening here, the metal is blended all the way to the bottom of the cone.


A couple other things.
Clean the holes free from dykem, oil, cutting fluid.
Sand the oxidation off the pin material. All stainless has a surface coating of oxidation -- that is what makes is stainless.
Polish the face and ball of the hammer. It will move metal easier instead of tearing it when piening.
Use the flat side of the hammer for most of your piening. It seems you should use the ball side but the flat side works better - with just a little practice.
I use a 3lb maul when I am done piening and smack it like crazy a couple times for good measure.

I now use a pin press: http://mickleyknives.com/html/page_29_pin_press.html
It's MUCH easier and I get much better results more often. cool 1

I now only get pins that show 1 out 6 or 7 knives. If I have pins or rings showing, I grind the bolster off and start over. :bud:

anyone else?

 

[Sean Cochran]

Tracy,
This really helps me alot. Since I have started building folders one of the hardest things i have found to do is hide the pivot pin. I cant just beat the crap out of it like I do on straight knife. After the holiday Im going to order a few things from you, this will now be on the list.


Sean

 

[Self Made Knives]

Boss, this an old thread I found with the search, but I wonder if you could give a little update on the pin press? I looked at the WIP on your website, even tried to use the email link on that website, but it says "undeliverable". Anyway, I've got a hydraulic press that I had years before knife making that I can use. Just wonder if you still prefer pressing pins vs. peening. Any advice on the dies? Thanks.

 

[BossDog]

My pin press is at home and I work on knives at the shop now so I tend to hand hammer them. This is one at a time and not all that often lately. I'll dig it out and bring it in for pictures.


The thing is to get the pins to blend. This takes about 5 minutes a pin - maybe.

1. make sure it is exactly the same metal. 303ss and 416ss will not work for example. A smaller pin is easier to blend. 5/32 or 3/32" pin size are the most popular. I used to use 1/8" and then switched to 5/32" - which is much easier. On a small knife, use the 3/32" pin size. The bolster will not come off, even with 3/32". You can smash/grind/drill it off but you can't make it come loose with even hard use otherwise. Bigger is not better in this case.
2. clean the oxidation off the pin by a light surface sanding to bright metal - even if looks bright to begin with
3. taper ream the hole and clean it of any oils/dirt. The taper is important. It helps the metal blend/smear to cover the hole. If it is a straight up/down hole (not using a taper reamer), it is harder to hide the outline.
4. the pin sticks out on both sides about the diameter of the pin, maybe 2x the diameter but no more. you want just enough extra to pound into and fill the tapered hole
5. polish the face of your hammer so it is slick and smooth. this helps the metal flow a little better
6. tap,tap, tap all around the pin- (both sides) at a 45degree using the flat, not ball side of the hammer. Keep flipping it back and forth for even attention to both sides. Don't let the pin slide in the hole by backing it up properly. If the pin moves when you are seating it, the metal won't blend together. The goal is to expand the pin and fuse the two pieces together. If the pin moves, it won't fuse together and you end up with an outline ring.
7. check for gaps between the bolster and tang, you may have to squeeze them together with a vise or large pliers. Sometimes they move. (most of the time they move)
8. tap, tap, tap, hammer, hammer, whack, wack, whack for good measure to drive it all home
9. grind off the excess and sand smooth and buff
10. if a pin shows, man up, grind off the whole mess and do it again. I've lost count of the times I had to start over.

 

[Self Made Knives]

Tracy, the reason I was asking was more if you thought you got better results with the press or peening. I just peened my first bolsters on for the kith knife and they hid just fine. I pretty much followed what you described and it wasn't too bad. My only issue was one errant whack kind of missed the pin and put a dent close the front edge of the bolster. Scared me, but it was ok this time. Seems like the press would be a less stressful method, as long as it gets good results.

 

[Moustacheknifeco]

Is stainless harder to get the pins to hide than in brass? I do it slightly different, but I am working brass, so I was wondering if that is why it seems to go so well.

I thought the pin press was a neat idea though.

 

[jkf96a]

Yes, I find stainless harder to hide pins than in brass. As far as Tracy's advice regarding grinding them off and starting over if you've got a pin showing, I have had some luck rescuing these with less drastic measures. Use the ball side of your hammer, and a small hammer at that, and deliver a zillion light taps ON the pin ring. You are basically forcing the gap closed. You have to grind it down to final finish again, and it sometimes takes a couple of tries, but it beats the heck out of starting over from scratch.

 

[BossDog]

Tracy, the reason I was asking was more if you thought you got better results with the press or peening. I just peened my first bolsters on for the kith knife and they hid just fine. I pretty much followed what you described and it wasn't too bad. My only issue was one errant whack kind of missed the pin and put a dent close the front edge of the bolster. Scared me, but it was ok this time. Seems like the press would be a less stressful method, as long as it gets good results.

I think if the press is lined up just right, it's faster. If it slips a little, it isn't. Like everything in knifemaking, it gets better and faster with practice.