M4 Steel - Waterjet cut jimping before heat treat?

[Daniel Fairly Knives]

The title says it all, here's my plan of action and questions.

- get m4 steel sheet waterjet cut into knife blanks including .125" and .187" diameter jimping. Knife is 6" overall and 3/32" thick.

-light tumble to deburr if needed

- profile knives on horizontal grinder

- tumble to deburr and round jimping

- heat treat to 62+ RC

Do I need to worry about stress risers in the waterjet cut jimping?

 

[Contender Machine]

As long as you don’t have it cut to a sharp corner it should be fine. 1/8 and 3/16 diameters shouldn’t bother.

 

[Daniel Fairly Knives]

As long as you don’t have it cut to a sharp corner it should be fine. 1/8 and 3/16 diameters shouldn’t bother.

Thanks!

I'm worried about the tiny lines the waterjet leaves in the surface of the jimping. It isn't usually a big deal but being M4 and 200 knives to heat treat... plus a third party doing heat treat I worry.

 

[Daniel Fairly Knives]

6" overall "Box Cutter" in .100" CPM-M4

 

[FredyCro]

Thanks!

I'm worried about the tiny lines the waterjet leaves in the surface of the jimping. It isn't usually a big deal but being M4 and 200 knives to heat treat... plus a third party doing heat treat I worry.

What about cleaning it out with a diamond burr in the drill press or dremmel in a jigg post HT? Obviously an additional step, but might be worth it to put your mind at ease.

 

[weo]

What about cleaning it out with a diamond burr in the drill press

From someone who is responsible for maintaining shop tools in a Makerspace, I would not allow this in our shop.
In general, drill presses do not like lateral forces unless you're ok with developing runout of the bit.

 

[REK Knives]

You will need to clean up the jimping... It will be cut on a taper unless they have super expensive 5th axis that can avoid taper

 

[Pinoy Knife]

you still have to clean up the profile after waterjet cuts it out (including the jimping)
as mentioned it leaves a bevel from the cutting .....not much but it is still there ...
a couple strokes with a file on each could do it .....but that is not a fine finish ,and you will still have to clean it up after heat treat..
get the correct diameter file maybe a #2 &#6 cut ....but after heat treat you will need maybe a rubber abrasive to clean up the jimping...
i have had several things waterjet cut ,and while it saves time in cutting out shapes it does require clean up on each part made.... not much but time is time

 

[Contender Machine]

Yeah as mentioned you’ll want to clean up all profile surfaces before heat treat any way. If it’s in the budget it would be a lot nicer to have them wire edm cut or even just milled out on a cnc mill. The latter might be your cheapest option overall, depends on what your time is worth to you cleaning up all those profiles.

If the blanks were laser/waterjet cut a little oversize, except for the holes, it would be real easy on a cnc mill to run around the profile. Could possibly run 2 or 3 blanks at one time.

 

[Daniel Fairly Knives]

Thanks guys!

I'm still debating things but I might just go with no jimping just to keep it simple.

I have had jimping waterjet cut and it looks pretty clean after a good tumble. That was on a 5 axis machine and with a pretty involved tumbling process.

My future plan is to use cnc to clean up my waterjet cut profiles but I need to get these done.

I think the jimping won't be a heat treat issue, I was mostly curious because I have not used a lot of M4 and it is different stuff to heat treat for sure.