Fillet Edge issue

Hey there,
I try to model this knife. I think i made the surfaces to complicated and now i dont find a way to fillet the edges… What mistake did i make?

No fillet.3dm (1.5 MB)

which radius do you want for that edge in question.
there is the rule to start with the biggest radius.
and do the same radi (radiuses ?) in the same step.

other challenge you re facing is, that the top still has a edge of around 2 degree.
(edge-continuety - i think a rhino v7 command)
and exactly this kink is touching the edge in question.

if filletEdge fails - there is _filletSrf to build single “like roling ball” surfaces.
than you can trim an join everything…

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Hello- your top curve has this at that location:

Should that all be one smooth continuous curve or should that short bit be a straight line segment, or? I think smooth would make your life easier if that fits with the design.


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Hey, yes it should be one flowing curve…
I try to connect these two parts… but I dont know any further… tried blendSrf etc. but Im not that far into surfaces yet…
No fillet.2.3dm (1.0 MB)
I use Rhino6

I have solved the top… I blendSrf between the both top surfaces with thangency. I think that solved the problem…
I created the side surfaces with surface from edge curves…
And now this is the problem.

I cannot do another BlendSrf between the sides, because the top surfaces wouldnt connect then…
As you can see the line(extenddynamic) shows that the surface doesn’t “flow” with the other one…
Is there any better way to model this? Have I maybe overcomplicated it?
No fillet.2.3dm (1.0 MB)
I use Rhino 6

Greetings and thanks!

Hi Paul - is the idea to fillet these for some machining need, or documentation or for rendering or? At any rate, in case it helps, here are some starting curves that are a little cleaner - it might make that fiddly stuff a little more tractable to used simpler inputs from the start, as long as the design intent can be met, of course.

KnifeCurves.3dm (33.1 KB)


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check out this video for some ideas.

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I model it only as practice from my kitchen knife.

I think this is one problem, although I created only one curve for the top … The moment I " destroyed" it was probably when I split the two parts and cut a section out. This I lofted together which made it probably flat…

Thanks for the advice!
I’ll try to model it further for practice.

It definitely shows me, that doing a tutorial and following along is quite simpler than modeling all on your own. But it’s fun nonetheless :slight_smile:

Whoa man! I gotta try this! This is already amazing jus watching it :heart_eyes:

Thanks Kyle!

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it’s just A way… it might not be the RIGHT way.

but I’m a fan of anything that gets the job done.

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I tried to build it from the start…
apparently, I make mistakes^^
I really tried to keep the construction as simple as possible, but this corner is a hard one…

Should I maybe take another way of modeling here?

Also, how would you model a knife blade. The previous version was an extrusion with a really small surface at the bottom. The new one is a Loft between two curves, creating this really sharp edge.
But is this really a good way? I feel this might be not the best solution there is…

here is the file (V6)
knife_new.3dm (1.9 MB)

Thanks again for the great support!


Hi paul - I guess there are some design decisions to make as far as the blade goes but I’d say it would make sense, probably, for a realistic thing, to make the blade as a flat piece and then cut into it with whatever shape makes sense - I guess the exception might be a full hollow or full flat grind, which seems to be what you are shooting for

Sweep1, the messy bit gets trimmed off by the top edge:


I need help with this…
I cannot wrap my head around it, how I can model the part where the grip runs into the blade…
Any way I try to model doesnt work and gets complicated when I try to fillet the edges…
I dont know any further…
I attached some pictures of the real knife.

Thanks again for the great support!

Hi Paul-

I may have missed it, but have you tried modeling everything as 1 form and then using tools to Boolean / split the handle and create the blade shapes?

Yes, I tried this way too…

After several attempts and your great suggestions, I came to this result.
knife.3dm (1.5 MB)

I didnt get the knife-grip part to taper.
The edge cannot be filleted without problems because of the two surfaces…

I did the blade with Sweep1 like @pascal suggested and that worked pretty fine. I extended it a bit to cut out the rounded edges of the grip part, which worked really well, except the surface is a bit complicated…

If you have any suggestions Id be glad to hear them!

So far thank you for the awesome help guys!

Edit: Rendering


Hi Paul-

FWIW I just tried quickly modeling the merge of the blade and handle, and using booleans and a variable radius it seems to work OK. I’m going to try that blade geometry next :slight_smile:

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Ok - for this, I took my previous geometry, drew straight polylines from the top, extruded, capped, booleaned from the blade, then filleted the tall inside corners, then filleted the edge along the top & down the sides.

Kind of sloppy but it’s just a sketch - sometimes if it doesn’t boolean properly it seems the edges aren’t meeting up on the blade parts. It might be better to model the whole tang separately, then subtract that shape from the handle. I did it in pieces and because I wasn’t really measuring anything, a few things didn’t line up correctly.

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