My Journey To The Perfect Drag Knife

[walter67]

Hi Folks

Just thought I would do a post on my trial and errors of making a drag knife
I know this subject has been covered many times before on a lot of media
platforms. but this one is quite unique especially if you are contemplating making your own..

I was interested in buying one from Donek tools but after looking at there dimensions
I would have struggled to fit to my 6040, cnc due to limited Z clearance and shaft size.

My only option was to make my own, knowing the internet is full of variations of the donek drag knife. But alas all the plans I came across were very similar in size.

So to work I went, I dug out a old unused Stanley blade from my tool box and set about getting the correct measurements using my vernier, I used Vectric aspire
to create the profiles and went ahead and made one..

Here's the result, But this is also where the hard fought journey began, more to follow..

[walter67]

So following on from my last post, whilst using the Drag knife to cut out some cardboard box templates I noticed the blade was starting to dull, so time to order
some new ones.

Once they arrived I tried fitting one, but to my surprise the Stanley blade would not fit
I paired up both my old blade & the new one only to notice that the Stanley logo and the dimensions had changed, I then got in touch with Stanley tools and asked if they had made any alterations to there blades, and they confirmed they had. Gutted!

This meant I would need to get out the Dremmel to modify the insert, I was not confident in doing this for making it totally unusable, so I decided I would
buy some more aluminium stock and make a new one plus I could make a 2nd
but smaller profile drag knife for more intricate cuts..

Now here's the mad thing, I was looking for a pen to write down my new dimensions
and picked up a sharpie from my draw only to find it had dried out, I then had another
rummage and found another one but noticed this was double ended, a thin and fat tip
a either end, then all of a sudden I had a light bulb moment, then after many countless
failed attempts at making prototypes this is the result…


Here`s Link to Showing the Drag Knife in action (https://www.youtube.com/watch?v=LvIUWtHxcdE&t=)

[Leadhead]

Very interesting. Would you consider sharing the files for it?

[Rye]

Wouldn't mind one for my machine, but it's got me thinking. Would a blade like this be more suitable:

24303

You'd probably be able to get rid of the blade clamp and fit it directly into the barrel.

[walter67]

Very interesting. Would you consider sharing the files for it?

Hi Leadhead

I will at some point release the files, but at the moment I'm in no rush

[walter67]

Wouldn't mind one for my machine, but it's got me thinking. Would a blade like this be more suitable:

24303

You'd probably be able to get rid of the blade clamp and fit it directly into the barrel.


Hi Rye

I did look into using those type of blades before I took the plunge, but after
reading how these drag knifes work, it's all about the offsets, the blade you have pointed out would be perfect for fine detail cut outs, but cutting thicker material
the blade would perform better if it was more angled, i.e. a bit like trying to cut
a thick cake with the knife at 90 degrees instead of 45 sorry for my analogy.

I have also edited my last post with a link to a Youtube video so you can see it
working

[cropwell]

I had a foil cutter, https://www.sorotec.de/shop/Mini-Foil-knife-Vario.html, which I destroyed by trying to cut the wrong material, so I remade it yesterday.

2434324344

I have yet to try it out, but the principle is simple. the 7x3x2 bearing is clamped by the knurled collar and the 6x3x2 bearing floats in the shaft with the spring applying the cutting pressure, adjusted by the grub screw. The neodymium magnet holds the cutter in.

The only problem with the one from Sorotec was that it was all pressed together and not dismantle-able or repairable.

My thoughts were to use a swivel knife and mount it with a cut down handle in an 8mm collet, but there is too much slop in the thing to be of any use, and it would only cut a minimum of 5mm radius corners as the blade offset was too much.

I like the Donatek clone idea, and I am considering how it could be done with a Swann Morton scalpel blade (cos they are sharp buggers ! and cheap).

[walter67]

Hi

I was asked if would share the Drag Knife plans

here you go..

[Leadhead]

Many thanks for the files. Much appreciated.