Knife - using one of those new fangled waterjet thingymajigs.

[tim_n]

So, I've volunteered myself to make knifes. Well, teach others to. So need to work out how to do it myself.

I've done some tracing on some knife blanks and I think I like this one.

I'm cutting it out on our "Wazer" which is a hobbyist waterjet cutter. Much more bushcrafty than an angle grinder because we're just using water and sand to cut with. Well, gem stone. The cost of the cut is £7.50, but I can check this works before getting a bunch cut on a laser.

 

[Nice65]

Cool project. Assuming you’re teaching individuals or a group, will you be using a grinder or hand files?

 

[tim_n]

we have all the things - I run https://eehack.space and we've just built a belt grinder specifically for the purpose!

 

[mikehill]

What a great facility !

 

[C_Claycomb]

Hi Tim. Good luck.
The back end bottom of your handle profile looks a little strange, too much outside radius on the butt to bottom junction, then a weird sharp internal angle where there should be an inner radius, then a bit wobbly through to mid handle. Even if the plan is to hand grind to final shape and fit just 6mm thick flat scales, I think you will save time and effort in the long run if you can clean up the profile.

Since I like sculpted handles, I would recommend sawing and filing a template from 3mm acrylic or better yet, polycarbonate, then sticking some model board scales to it with masking tape and double sided. Shape the handle to match the tang. If it all works, you can remove the scales, trace the template, scan it, and spline trace the scan into your cutting software. This process will show up if the tang shape compliments and works with the 3D handle shape.

 

[Pattree]

I know nothing about knife making or design and I know you’ve done your risk assessment but:
Is the blade longer than the UK legal for public use? Would a slightly shorter shape, more typical of those seen here, be more appropriate for a public workshop?

I occasionally do public workshops making plastic flutes. You’d think they’d be harmless enough but my public liability insurance provider made me jump through all sorts of hoops.

Just thoughts.
pee ess: I have big hands and may well have misinterpreted the scale of your profile.

Very best of luck with your project.

 

[mikehill]

As it’s a fixed blade I wouldn’t think the length would matter

 

[C_Claycomb]

As it’s a fixed blade I wouldn’t think the length would matter

Yup, it is not a "non-locking folding knife", so length is an irrelevance.

 

[Nice65]

we have all the things - I run https://eehack.space and we've just built a belt grinder specifically for the purpose!

Superb resource. I like ‘Flattening plate - don‘t store stuff on it’.

And,

• Machinist precision tools from the apollo rocket builds (yes the 1960's ones)

 

[pieinthesky]

If you are buying your steel in strip form it might be easier to grind the profile by hand - Cut it rough with a disk and hog the rest with a coarse belt - If you are using sheet and/or doing loads, it makes sense to water jet.

But I fully understand if you just want to play with your water jet - I want one.

It is well worth making a model first as Chris suggests - I use plasticine for the scales and experiment until happy with the shape.

Can you explain the figures on the drawing? Is it 33 minutes and 5kg abrasive for 1 blade?

 

[C_Claycomb]

Wow! Didn’t notice the consumption figures! I wonder how that changes if one has several layers stacked together.

With jet of beam cutting one can get creative with under-scale skeletonizing for weight reduction. Not just a bunch of round holes, but profiled holes that follow the outer shape, closer near the butt where you don’t need strength and leave more meat near the blade. This is something that is very time consuming to do by hand.

 

[pieinthesky]

Can you stack with water jet?

 

[Mesquite]

Can you stack with water jet?

You can but it doesn't help to reduce cutting time or abrasive material used per blank much as the water jet has twice or however many layers it has much metal to cut through.

The other thing is the jet isn't fine it's entire length like a laser. It's a very fine cone so the bottom blanks would end up slightly smaller than the ones on top.

 

[C_Claycomb]

Can you stack with water jet?

I think you can, but the layers must be in close contact, which is not usually possible if you have big sheets of material. The time and abrasive quantity on the picture seemed so high that I wondered if there might be some capacity for a second blank on top.

We have had generator stators water jet cut in half, and the problems arise when there is either a void, or you ask the jet to cut down where materials of different hardnesses meet. Voids allow the get to spread a bit, and like a river, the jet will lean towards the path of least resistance if there are different materials.

I knew about the cone effect, the pro shops get around it with a tilting head, but don't know how feed/speed relate to material or thickness.

Tang skeletonisation by https://carothersknives.com/

Random Thought Thread

These long swords are a challenge. This is .125" thick kydex

www.bladeforums.com

 

[tim_n]

I know you all like to live vicariously, so here's a timelapse video

which'll answer some questions.

And some pics.

This particular one I scaled down so I could fit a larger blade underneath and this was a trial. This was about £5 of cutting costs. Skeletonizing would pretty easy with this method if you can design.

Thanks for the tips on design. I scanned my blank in from a knife and edited it myself. I am not a designer.

If you want the SVG message me and I'll send it over.

If you want to pop by and cut something on the wazer you're more than welcome to if you're in the area and I'm free. I can't really cut stuff unless you post me the material and the cost is £15ph plus postage

RE: quantities of garnet yes that's correct, it's approximately 5kg of garnet and 33 minute cut. We cannot reuse the garnet. It's why it's £15ph to use. I get the alluvial garnet from a specialist supplier. It has to be dry which is one reason we can't reuse it. This machine is a hobbyist machine, whilst costing about £12k and costs £15ph to run (that's a raw cost and covers the bed and cutting head which are consumables as well as the garnet). It's in line with getting a commercial one off cut from someone who does laser cuts. But there's no lead time so if you screw up, you can just cut again if you have the material. Our local laser places can be 6 weeks backed up, so this really is just for rapid prototyping. Once I know what I want we have a guy who will get the stuff cut on his 24kw laser when the boss isn't looking.

 

[tim_n]

Bit more work on the blade. I cut up some dyed curly birch and then using a disc sander, belt grinder and some manual sanding got it handled to the point I'm relatively happy. Needs more sanding. It's not great, but it's a nice first knife. Now I just need to handle the ones from Dave.

 

[Mesquite]

Nice work Tim, that's a lovely bit of birch

 

[Kepis]

That's a cracker and that Birch is stunning, looks like it will be a proper user.

 

[SoldierPalmer]

The handle looks great. A bit of advice on the blade. Hand sand the blade to the desired finish before putting the handle on. Once the handle is on it makes it really difficult to go back to it. Also when hand sanding have the scratches all going one direction this gives it a smarter finish. A quick search on YouTube will give you a good demonstration.

 

[gg012]

Bit more work on the blade. I cut up some dyed curly birch and then using a disc sander, belt grinder and some manual sanding got it handled to the point I'm relatively happy. Needs more sanding. It's not great, but it's a nice first knife. Now I just need to handle the ones from Dave.

Tidy work there. Well done