Workflow to draw a compound grind on a knife edge?

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ErnestoA
Posts: 2
Joined: Sat Oct 21, 2017 2:34 am

Workflow to draw a compound grind on a knife edge?

Postby ErnestoA » Thu Aug 16, 2018 10:40 pm

I've been playing with FreeCAD for three years now but mainly using LibreCad. It's time to get serious about 3D so I spent the last few days trying to figure out how to get dxf's from LibreCad to display properly in FreeCad. I've reached "good enough for who it's for" levels in that department but while working on my first project, I hit a snag that I just can't find a way around. I need to model a compound knife grind and can't find an explanation or tutorial and I can't even imagine the workflow other than attempting to draw it in wireframe and skin it somehow.

Can anyone recommend a tutorial or explain the process to draw the edge of a knife like this?

Example knife:
crazyknife.jpg
example knife
crazyknife.jpg (288.68 KiB) Viewed 162 times
https://2rdrtx4bt29lo91s31mjhkji-wpengi ... IND-06.jpg

I'm very sorry if this is a dumb question. I'm using the newest version of FreeCAD. Any help is greatly appreciated.
Attachments
knife.fcstd
progress so far
(262.74 KiB) Downloaded 4 times
Bance
Posts: 126
Joined: Wed Feb 11, 2015 3:00 pm

Re: Workflow to draw a compound grind on a knife edge?

Postby Bance » Fri Aug 17, 2018 5:32 pm

You can do it using subtractive sweep in part design.....

Included rather rough example.

HTH Steve.
knife.jpeg
knife.jpeg (31.67 KiB) Viewed 146 times
Attachments
knifebance.fcstd
(53.83 KiB) Downloaded 2 times
oldmachine
Posts: 223
Joined: Wed May 31, 2017 11:49 pm

Re: Workflow to draw a compound grind on a knife edge?

Postby oldmachine » Fri Aug 17, 2018 6:13 pm

I designed knives for BenchMade (worlds best knives).

The edge is simply a shape that follows a path.

The shape depends on type/use of knife (and the equipment you have for grinding).

Here’s a screenshot off the net with typical shapes.

Create your path and shape cross-section and sweep it.
Attachments
Screen Shot 2018-08-17 at 11.07.12 AM.png
Screen Shot 2018-08-17 at 11.07.12 AM.png (303.8 KiB) Viewed 140 times
MAC OSX Sierra
3D Parts & Links (made using FreeCad and Solidworks): https://www.thingiverse.com/Still_Breathing/designs
Android App & Links: https://play.google.com/store/apps/deta ... .bestknots
ErnestoA
Posts: 2
Joined: Sat Oct 21, 2017 2:34 am

Re: Workflow to draw a compound grind on a knife edge?

Postby ErnestoA » Fri Aug 17, 2018 10:09 pm

Thanks for the replies. Now I can search for "Sweep" and see if I can figure anything out.

This knife is a little tricky because it has different grinds to compliment the different edges of the blade, and they need to smoothly transition from one to the other. I'm not sure this is even possible in freecad. The seeming inability to create free form asymmetrical shapes has been the main factor in me putting off learning FreeCAD for so long.
TheMarkster
Posts: 411
Joined: Thu Apr 05, 2018 1:53 am

Re: Workflow to draw a compound grind on a knife edge?

Postby TheMarkster » Sat Aug 18, 2018 3:58 am

A starting point [groan smilie here] maybe.
Attachments
knife-blank.FCStd
(38.92 KiB) Downloaded 4 times