Doctor's knife WIP

[ashwinearl]

Using a rough rider as a hard pattern.

[C-WADE7]

Keep us updated on the progress. Are you doing a single blade or adding the spatula blade as well?

[ashwinearl]

Hi,
I am doing double blade with spatula. This will be my first attempt at a dual " blade"

[Reverand]

I enjoy seeing this work in progress!

[ashwinearl]

This pictures shows one blade and two springs on a "Ruple guage". The goal of this step is to set the initial clocking. Clocking refers to the backspring positions in the open, half-stop, and closed positions.

The ultimate goal is that the spring is in the same place (fully flush with the liners/scales), when the blade is in those three positions.

The reason I have two springs glued together is I want this to be a two-'blade' knife with a cutting blade and spatula. Ideally, I would also have had the two blades glued together and do this initial clocking together. However, the spatula blade's kick is a little different than the regular blade, so opted to do them separately but still keep the springs together at this point.

When in the Ruple guage, the spring is not under tension, other than what I apply with my thumb. So it is not a good idea to try and achieve full flushness here as things change when under the tension seen in the liners.

So my goal here will be to use the open position as my reference for 0.000" and shoot for +0.005" at half stop, and +.015" at closed. I'm already closer than that on the closed position. Regardless the key is to be high in the mid/closed position at this point. If I was low, I have some chance to recover by taking more out of the backsquare. But you can only go to that well so few times.

Next steps:
-Initial clocking of the spatula
-rough cut liners
-set tension in the liners, aim for higher than final desired tension
-place blades under tension in liners an grind off the back flush (this ends up reducing some spring tension)
-then goto "Kennedy jig" where clocking adjustment are resumed but with spring under tension

[ashwinearl]

Here it is in liners. Trashed two sets of liners to get here.
Also video of walk/talk action. It is on the lighter side maybe 4ish. It's going to be smallish knife.
https://youtube.com/shorts/XOZfo_kJKZ4?feature=share

Next steps:
-Put into Kennedy Jig and set clocking under tension, blade and spatula one at a time
-rough grind blade, thin out tip of spatula
-long pull on blade, nail nick on spatula
-decide on whether to do bolsters, or shadow pattern

[C-WADE7]

Moving along nicely. Thanks for progress update.

[ashwinearl]

Here, I am setting clocking with the spring under tension in a device called a Kennedy Jig. I set the tension when I drilled the liners, and then use the liners to set the pins in this jig. It is a lot of tedious back and forth to the grinder (in horizontal position) to get the positions to near 0 referenced from the open position.

I really should keep them a hair high and finish in the final liners, as things can still change some.

Next is grinding the blade and thinning out the spatula. I'll sand both to 200-400 and save the rest to 600 or 800 satin till closer to the end.

[bestgear]

I’m really enjoying both your explanations and images - I’ve already learned so much, thank you.

[ashwinearl]

Grinding the blade today. My process is to measure the thickness, subtract 0.020 and divide by two. I then set my height guage to scribe two parallel lines at that height. The goal is to grind bevels with that thickness. I over shoot and then during the hand sanding process get it to the edge. If I can have this as the goal thickness by then end of the process I'll be thinner and at good spot for final edge.

I use a jig to grind in 45degree bevels to the scribe line, then I goto hand grinding with a file guide. This is very challenging for me. I've tried jigs but keep coming back to just by hand for better control. But it is nerveracking and easy to mess up. I'll start with a 60 degree ceramic, then to 120 degree ceramic, then 220 j belt (softer edges to get into plunge better). Then 400.

I stop here usually and move to hand sanding. I'll use stones first then switch to sandpaper. I need to to the swedge too. Another very challenging step that I have not figured out a good approach yet. lately, I have been angling my platen and trying to hold the blade 90 degree to the ground as opposed to trying to angle the blade.

[ashwinearl]

Rough cut swedge, tapered the spatula blade (harder then I thought), torch tempered back the spatula blade to give it some more springiness.

Now onto Gesswein die grinding stones to change the vertical scratch lines from the belt to horizontal inline with the blade. This next step is pure elbow grease. I'll switch from stones to sandpaper at about 400 grit. I'll go up to 400 now then 600 or 800 towards the end.

[ashwinearl]

I added long pull to the blade using dremel wheel, and nail nick using 3" wheel angled. I admit, nail nicks are a weakness. I have a plan to obtain a mill, which will also open up milled relief liners. There are other ways with stones, chain saw sharpening wheels. Regardless, this is one of the hardest parts of slipjoint making, but also a functional aspect that makes a knife a joy or not to use.

I used Gesswein stones to get the sanding lines parallel with the blade length, then to 600 grit sand paper. I'll tape the blades now and do more finish work later.

In putting the knife together, I think I was not consistent where each liner was going. The middle liner or now too low. So I need to make a decision to keep it as is, redo the middle liner, or redo all the liners. redoing all the liners has more chance of success then redoing just one. These are already the third set. But that is knifemaking in a nutshell.

Redoing the liners would also give me another chance to increase the pull strength and have opportunity to reduce it later.

[ashwinearl]

I redid the liners and decided to add bolsters at front and butt. I use a 220V harbor freight spot welder for this step. I've tried silver solder but never had luck with that approach. Some tricks here are shaping the tips to help keep from blowing out the back.

Bolsters are 416 Stainless. I've surface ground them and squared up one edge on my disc grinder. To align the right and left I use my file guide in a several step approach. I use a drop of glue to hold first bolster in place. This has been problematic in the past if the glue spreads out too thin across the whole surface. The tiny gap between the liner and bolster won't let the spot welder work its magic.

I tack the bolster in 3-4 spots, then drill through the pivot hole in the liner. Then I put as many welds as I can onto the bolster. Redrill just incase the piece work hardened and made the hole smaller. Then place it between some AL plates to cool. It is really hot at this point. I then place the two liners together in my file jig. Using the carbide edge against the first bolster. I use a glue a piece of liner against the file guide. Take the two liners apart, and reput the file guide against the piece I just glued down. Once tightened down, I snap the glued piece off and use the the file guide to place the 2nd bolster. Again dab of glue to just hold it in place. The welding, if it works, burns off the glue.

The top bolster is place square to the liner, but the bottom bolster is angled slightly. This is actually slightly easier when it comes to placing the covers. It's a slow handsanding approach to get them to fit right, and the little bit of angle helps wedge the scale in. I've actually had less problems with two bolsters compared to just front bolster when it comes to the scales coming off during the remainder of the making. I use epoxy and then pins to peen them at the very end. But heat from the shaping, or dropping them often pops them off during build.

Later, I have to remember to anneal the bolsters by heating them to red with a torch and letting them cool slowly. This is to avoid showing the spots when I shape and sand the bolsters to final finish.

I repeat this process for front and rear bolsters. Next comes putting it all back together and grinding the back flush with the springs. Then back to sizing up the front and then to covers.

[ashwinearl]

front bolsters tapered, covers fitted, gluing

Next step, drill pivot pin, and small holes for peening covers to liners, flush covers to liners, shield install

[ashwinearl]

Sorry to disappoint, but I am throwing the towel in on this one. I over ground the spine, which leads to low spring tension and blowing through the pivot hole on the scale. I seem prone to this mistake on straight back spines. The tell tale sign early one, was low spring tension that got lower and lower. Even w/o this issue, this specific knife fought me the whole way.

Regardless, it was great practice on multiple fronts. 2 blades, grinding small delicate blade, grinding taper on spatula, performing additional spring temper on the spacula blade to give it some flex, using cratex to jewel the liners. Practicing with my engraver.

Frustrating mostly because of making this same mistake in the past.

I will revisit this pattern as I cut two sets out when I started. But I might focus on a more basic knife next.

Thanks for following along.

[edge213]

Looks like it was going to be a beauty.

[Quick Steel]

ashwinearl, Your clear descriptions and fine photos made for an absolutely fascinating presentation. Inspite of the temporary setback, very well done sir!