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Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Alex T., Jan 14, 2020.
This is good to know, thank you.
UPDATE, as promised
Mini tutorial on how I do it, not for the super new knifemaker, a bit of advanced stuff here.
What you need:
- Disk grinder, 9" minimum
- Sandpaper sheet (no silicon carbide, to brittle at this speed, use AO) start at 320
- a good spray adhesive, I use the 3m with 77 written on it, cheaper than the feather adhesive
- surface plate. For my part, I am a bit masochist and decided to scrape one huge marble plate, took me ages lol
- Welding magnet
- 1-2-3 block
Before we start, I taper all my tangs, so that's why I can't juste buy precision ground stock and slap a handle on it.
I tried some things yesterday, mainly using more the disk grinder and less hand lapping, it takes to much time to my liking, I can easily waste an entire day lapping one hardened stainless tang. So since I do not have higher grit of psa disk higher than 150, I decided to use... sandpaper with 3m spray adhesive. The big plus of using sandpaper sheets is that you can esily change them, they are cheap and the most important, they are thinner than a psa disk so they will be flatter on the disk itself. One thing before continuing, you need to clean that disk thoroughly before putting the sandpaper, or else every f****** gummy residu will act like a bump. After what felt like an eternity of scraping the damn psa residue, I finally started with 320 grit AO paper. You don't really care that the paper is brittle, you are just removing tiny amount of material. I have a 12" disk but since sheets are 9 x 11, I cut it to a 9 ". You need to put your tang/bolster/whatever you want flat BEFORE you turn on the grinder or else you will never be parallele. So push a bit hard, this way the grinder can't start turning (or use a foot pedal switch, wich I recommend). Once both your hands are on the magnet after starting the grinder, give some room to the disk to gain speed and then repush you tang on the disk, it is very important to have steady hands and to not move at all, the tiniest movement will make a not flat surface, you really need to be able to be steady and know "the feel" when your hands wants to move and prevent this (this is why it is not for beginners, you need that muscle memory IMO). I previously grinded with a 150 grit psa disk, then put dykem and then went with a 320 grit AO paper:
as you can see, the psa disk did not grind flat at all (the blue parts), even if I used the same technique than the 320 paper.
Now continue a bit with this method until everything disapear and check on a flat surface of reference (I use a machinist 1-2-3 block, those are also very, very, very, very useful)
As you can see, there are no gap at all, this part of the tang is dead flat (at least to the eye) but just to be sure, lets check on the surface plate
I lapped for exactly 11 seconds, you can see that the disk grinder did indeed get this very flat except of two parts, and thats because I stopped grinding before reaching them for the sake of this tutorial. What took me hours to get a flat tang now takes me about 1 hour.
Now here is the final result on another knife I have finished with this method
You can see there are no gap at all
Thank you guys and girls, if you have questions on the process I used, just ask
Absolutely nailed it....like a professional technical writer. Damn.....
thought I would share this, I was visiting my friend Tim Wright yesterday and helping with some photographs,
here is his belt knife with bolsters and while there is a line/seam, it's pretty hard to see.
Yeah I made myself to the idea that it would be near impossible to get that perfect seamless. I think what you you are showing is the max attainable by hand, wich is still very good. I still work on getting the flattest surface I can... Wish I had the money to get a surface grinder, I lose so much time to get everything flat lol.
Maybe I'm going slightly o.t., but I couldn't help looking with interest at the splendid round connection made between wood scales and bolsters. Is it possible to know the technique used?
Think I got the trick to get that seamless fit... and that's actually pretty obvious when you think of it. I still have to do another one to validate my theory tho... Here I am at 1000 grit after buffing. Wish I could send a video but they are always "too large" for here...
That is an impressive joint. I am willing to bet the round are was milled or ground that way after being soldered? Near impossible to support such thin cross section by itself...
U can contact Tim on Instagram
He would love to answer any questions
I have sent some messages to Tim, he is a very helpful and competent person. Grazie!
You can upload to YouTube and link to the video.
Some thoughts here....
For fixed blades several things will help.
Use 416 if possible, 300 series stainless has a yellow color to it because of the high nickel content. 416 is the same color as the blade.
Mo flatter mo better.
Don’t taper, countersink or bevel the holes in the bolsters, straight is best.
Use the flat(ish) hammer face and not the ball peen when hammering the pins. Use pins that are oversized in length equal to the diameter on each side. 1/8 inch pin should stick out 1/8 inch on each side. Work the pins down from each side equally to draw the bolsters in tight.
Bolsters should be slightly wider than the blade. After pinning the bolsters, pins should be almost even with the surface at this point, place the knife edge up or spine up in a sturdy vice and gently upset the bolsters where the seem and the tang meet with a small slightly rounded punch.
Finish and voila.
edit: Tim Wright has been making flawless knives for a very long time
I have to respectfully disagree with this statement. I have used 416, 304 and 303, but mostly 304. Only 303 has that ugly tint. The only reason I see to use 416 is that it is easier to work with, but needs proper HT to be at its best corrosion resistance. 304 needs no heat treat and is not that much of a pain to grind when you just accept that it sucks to work with lol.
You can disagree, respectfully disagree, or adamantly disagree, I don’t care.
Look up 302,303, and 304 and the only difference is small amounts of carbon or sulfur.
I realize that you gave birth to this thread and want to protect your baby.
Go to a chrome plating shop in your area and ask them if nickel has a yellow tint to it.
Your own photos show the yellow tint that I’m talking about.
Steel is grey, chrome is blue, nickel is yellow, pure iron is brown, copper is red, silver is white, we are talking hints of color here.
Of course you are free to use whatever you want.
This thread is my baby? I am just seeking help to get a seamless fit between bolsters and tang, I have nothing to protect. If I have this question, there are probably dozens of other people that have the same question, they want to be better craftsman who are also struggling with bolsters and who want to do more than just slap two scales on a knife and call it done. I want to be a better knifemaker and you have brought helpful tips in your previous post that will surely help new guys like me.
But the fact that I disagree with you about if 304 does have or not a yellow tint is in my opinon a matter of taste and I don't think it is related to getting a seamless fit between bolsters and tang. So lets put aside our taste difference and instead focus on what this thread is about: getting seamless fit between bolster and tang.
Edit: put our taste difference aside
@Alex T. while it's true that this thread is about - "getting seamless fit between bolster and tang."
There are other things to be learned here. Looks like you are doing pretty good work and trying to get better.
@DevinT and Tim Wright have about a combined 90 years experience between them.
So when they say or suggest something, I think it's certainly worth consideration.
I spoke to Tim on the phone about this and he offered the following -
He clearly prefers hardened 416 and has several reasons why he won't use 304
They very first thing he mentioned was the color concern...
304 has a yellowish cast with 8% nickel, the 416 color is better and he wants the bolster steel to match the blade.
It's soft and he prefers a harder bolster, hardened bolsters polish nicer and age better.
You can harden 416 and it machines better in it's hardened state of about 43 RC
304 isn't free machining, and doesn't respond well on a surface grinder.
Consider giving 416 hardened a try in your work, you may find it yields a better finished product.
@HSC /// thank you for clarifying the 304/416 thing. Like I said, I thank @DevinT for sharing these tips, they are useful. I also thank you for calling Tim wright and share it on here as to why he prefers 416. I would really like to work more with 416 (did about 2 knives with it). But with my current situation, I will stick with 304 since I do not have the proper equipment to HT 416. Buying 416, wich already cost more than 304 and send it to HT would become cost prohibitve. I would also have to buy it from the US (they don't have the size I use in Canada), the cost becomes ridiculously high for just a couple of 3/8 x 1.5 x 24 flatbar.
Where do you guys get the 416? I only know of jantz.