Each bar I have is big enough for two knives, but I cannot simply halve them – there is nearly 10 cm overlap towards the tips. That way I get longer knives whilst wasting less material. I have made a new paper template and here you can see how I laid it on the bar. To draw the outline I covered the whole bar in blue color using very thick (1 cm) marker. A much cheaper and more readily available option to machinist’s blue. You can also see that I have lost my drawing needle somewhere in the 10 square meters of my shop so I have made a new one from an old shuttle bobbin. I hope I won’t lose it too.
When doing this I have wanted to test an idea how to improve my process already, so I have made another template which allowed me to mark not only the two holes for pins, but also a hole at the center of the finger groove. Unfortunately I did not make a picture of that.
But here you can perhaps see why the third hole. After marking the hole positions with a center punch, I proceeded to the drill. But instead of a normal drill bit, I have spanned in it a step drill which allows me to drill holes from 4 to 22 mm. So I drilled 6 mm holes for pins and an 18 mm hole where the finger groove is. That way I do not need to mess around with some improvised way to grind a nice tight radius that I need. This is a big time and hassle saving in itself.
This is also first significant change in design to the prototype that I have given to my mother. She did not exactly complain, but she commented that a deeper finger groove would be more comfortable. So I am making the groove deeper and therefore the handle inevitably skinnier in this part.
I have marked and drilled both halves, then I cut the bar diagonally with an angle grinder. Using an angle grinder I have also cut excess metal on both knives since I live by the rule – if you can cut it, do not grind it. After that I have tried another time-saving measure that I have thought up in my idle time – I have connected both knives with screws through the pin holes. With that I proceeded to the belt grinder to grind the outline of the blades.
It worked very well and I had outlined two knives very quickly, in fact these three steps took a lot less time than I expected – just one hour overall. And I even see big time-saving potentials here:
- For drilling I could make a template for guiding 6 mm drill bit instead of punching the holes for each blade separately. So for next run I will first fish around in my scrap pile if I find a scrap piece of the right shape and size. Then I can stack and drill more pieces in one go. I will lose some time by stacking, but save time drawing and punching. Also next time I will first drill all stacked pieces with a 6 mm drill bit for the finger groove as well. That means changing the bit once, but I think it will be more than made up by the time saved from drawing and punching.
- I can probably stack at least two, maybe even five, pieces before cutting all the excess with the angle grinder. Five pieces would be 9 mm thick, and an angle grinder should be able to grind through that without big trouble and without too much reduction in speed. And I will waste less time per blade by repositioning the piece in the vice for each cut.
- Ditto for the belt grinder. A new 40 grit belt should be able to grind five pieces at once with only marginal reduction in speed. That would also improve reproducibility.
So I am putting this in the “low hanging fruit” basket, since the 30 minutes per blade is significant 10% of my goal time and I estimate I can cut that easily down to half or maybe even less.
Marcus Ranum says
Please tell me you used that machinist’s clamp for more than a base to drill on. “Helicoptering” knife blades in drill presses is the #1 preferred way dor knifemakers to lose a finger. Even if the blade is not sharp, a square edge with a tiny burr can peel a hand to the bone.
I have personally seen that twice; maybe there is a reason I freak at the sight of uncontrolled bleeding.
I know about helicoptering, but I used the clamp as just a base even so and it never happened to me with the step-drill bit. Anyroad, this steel bar is so long, that if it got snatched up by the drill bit, it would hit the drill pres’s column and stop there. And its lenght also provided nice and long lever to hold it firmly.
It did happen to me a few times, but not very often, and in my experience the risks of helicoptering are highest when drilling either too big hole in one go (like 10 mm) or drilling thin and soft material (like aluminium), or when making an existing hole bigger by too small increment (like 0,5-1 mm). When drilling a hole in steel with increments 2 mm it never happened to me.
But it happened to me that a piece of aluminium got snatched and dragged up on the drill bit with the machinists clamp.
Whats harder than to find a needle in a haystack? A needle in a metalstack. D:
I really enjoy your series on knifemaking. Take care!
These knives are looking great, and I like the idea about shaping two at once.
I used to have a drill press (a teeny one) and occasionally would have a very small piece (about the size of my thumbnail) of sterling silver helicopter on me. My solution was to get rid of the drill press and make holes a different way: I now punch them instead of drill them. But I doubt that solution would work on something as hard as steel!