Laser or Water?

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Killean

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Forgive me if this question has been around for a while - I am a new boy here:

I have designed a one piece, skeleton, seatbelt cutter which will be made with 2.5 or 3mm AEB-L.
It is 200mm long and widest extremities 50mm; the blade is 10mm
The blade is a pronounced hook. Plain and 33% serrated, probably single bevel - CNC milled.
They will be sharpened almost every time used, so hardness & edge hold is less important than ease of sharpening (by hand).
These cutters will be mass produced and cost effectiveness is critical. We are not making a 10,000$ masterpiece or a 500$ collectable.

And to the question:
We had intended to have the blanks laser cut (all prototypes have been so far), but now I am told they must be waterjet cut. Is watercut desirable or essential? Or a red herring?

We need an answer quickly please. Can anyone give me a definitive answer?

Many thanks,

Killean
 
Welcome Killean ... fill out your profile so we know a bit about you and where you live.

Waterjet would be needed because there is no HAZ (Heat Affected Zone). Laser creates HAZ, which is a hard area that needs to be ground away. The edge of a water Jet cut is not hardened and ready to grind/shape/sharpen.
 
It would help to know what kind of operations are to going to be done to it after being cut, and also if any holes will be laser cut and then opened up later? The HAZE on the edges of a hole that has to be reamed later can be a real pain and really wear out bits quickly. Will the edges amd serrations be cut after heat treat? How was your experience working with the prototypes?

Eric
 
I am not a knife maker, but I have gathered that the processes are:
Cut the blank > polish the blank > heat treatment > bevel grind > edge & serration > coating. All the holes are holes, just that
What did they all do before water cutting?!
I cannot find a way to add an image from my PC - very frustrating.
To get an idea of what we do go to www.barringtoninternational.co.uk and look for ligature cutters. All of them are make by others; I need my own design and I want, very much, to avoid continuing to buy from the Far East or indeed the EU!
As for me .. .. .. ex-military of many generations, British Army & Navy sword collector starting at 1800. I have also inherited four Samurai pieces, one being 15C - no water cutting then.
 
ea42 said:
It would help to know what kind of operations are to going to be done to it after being cut, and also if any holes will be laser cut and then opened up later? The HAZE on the edges of a hole that has to be reamed later can be a real pain and really wear out bits quickly. Will the edges amd serrations be cut after heat treat? How was your experience working with the prototypes?

Eric
Click to expand...
None of the prototypes were hardened, we were interested only in the shape, feel and ability to cut (even just once). I wish that I could post an image.
 
What about adding extra material to the edge.....

Laser cut everything, then have a separate operation to skim/grind the edge (only) then continue with machining?
It should only be a few passes to clean up heat affect
 
Waterjet has the potential to leave a much nicer cut finish/quality. Have both quoted and see which is cheaper for you. Waterjet tends to be slower but when getting into knife type steels is can be cheaper than a laser sometimes. It really just depends a lot on what kind of laser or waterjet is being used that will determine the cost. Either method could work but a laser may require more steps afterward to finish it (as others here have explained).
 
Just to clarify the OIP's needs:
These will NOT be hardened, the blanks will only receive sharpening. minimal steps in processing are high priority, they are not repeat use items, the simplest production at the lowest cost is the desired target.

As I answered, water jet would be the best way to accomplish this.
 
Keep in mind thought waterjet will have a taper to the cut unless they have 5th axis...
 
Stacy E. Apelt - Bladesmith said:
Just to clarify the OIP's needs:
These will NOT be hardened, the blanks will only receive sharpening. minimal steps in processing are high priority, they are not repeat use items, the simplest production at the lowest cost is the desired target.

As I answered, water jet would be the best way to accomplish this.
Click to expand...
Post #5 says heat treatment.
I take that as hardening???
 
Crag the Brewer said:
What about adding extra material to the edge.....

Laser cut everything, then have a separate operation to skim/grind the edge (only) then continue with machining?
It should only be a few passes to clean up heat affect
Click to expand...
That is what I had envisaged. I will speak to the CNC milling folk. Thank you.
 
Killean said:
That is what I had envisaged. I will speak to the CNC milling folk. Thank you.
Click to expand...

idk what your piece looks like, but they are only needing to remove the heat affected zone..... not many thousandths.
also, I'm assuming they are running coolant, heavy duty fixtures, and carbide tooling?

shouldn't be a big deal.
machine shops mill laser cut parts all the time

*They should be able to tell you what their specific concerns are.
 
People cut and drilled by hand/machine before water jet/laser. Drills and saws have been around a long time!

Water jet holes are undersized and may have an angle to them as well (tapered holes) unless its a dynamic head or 5th axis or whatever they use.

You can use a photo hosting site like imgur and use the BBC code to post the pics...
 
Killean said:
I am not a knife maker, but I have gathered that the processes are:
Cut the blank > polish the blank > heat treatment > bevel grind > edge & serration > coating. All the holes are holes, just that
What did they all do before water cutting?!
I cannot find a way to add an image from my PC - very frustrating.
To get an idea of what we do go to www.barringtoninternational.co.uk and look for ligature cutters. All of them are make by others; I need my own design and I want, very much, to avoid continuing to buy from the Far East or indeed the EU!
As for me .. .. .. ex-military of many generations, British Army & Navy sword collector starting at 1800. I have also inherited four Samurai pieces, one being 15C - no water cutting then.
Click to expand...

With those processes in that order I don't think it really matters either way as to what cutting method is used. As has been said you may get a bit of an angle from water jet cutting but I've seen the same from laser so that's something you might want to bring up with whoever you choose to do the cutting. If holes aren't going to be addressed after cutting there's no need to worry about haze there either. Grinding and edging are done after heat treat so that nullifies the haze as well. You may need an extra polishing step after heat treatment.

Before water jet and laser cutting high production parts were (and still are) blanked out of sheet steel cookie cutter style.

Eric
 
In post #5, I not sure if the final units will be hardened or he was describing what he had found online about making knives? Either way, I still think waterjet would be the best method,
 
Stacy E. Apelt - Bladesmith said:
In post #5, I not sure if the final units will be hardened or he was describing what he had found online about making knives? Either way, I still think waterjet would be the best method,
Click to expand...
Yes, they will be hardened - I thought all knives are hardened. There is a tortuous discussion about hardening before or after grinding. Milling after hardening vs blade deformation and cracking if hardened after being sharpened. Knives have been made for a very long time and I don't understand why there is no definitive answer. I even bought Dr Larrin Thomas's book "Knife Engineering" - 440 pages and I was beginning to lose the will to live!

As for laser vs water; I give up - we are going to do both and see what the difference is.
 
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