Help with knife modeling


Hi all. I’m trying to sketchup a knife. So far I have the shape of the knife cut out and the thickness right but I can’t figure out how to make the bevel on it. I have tried a combination of the simple tools I know how to use but none of them come out right. Its a scandi grind so from the line running down the side of the knife its just a straight simple bevel to the edge of the blade. any help would be much appreciated. AutoSave_knife.skp (662.3 KB)


Search on the FollowMe tool.


I would use Fredo’s Curviloft to create the hollow ground bevel. I can’t demonstrate at the moment but I will later if someone else doesn’t beat me to it.


Something to fix on the knife is that the top faces and the faces inside the holes are showing the back not the front. Select those and right-click/Reverse Faces.


This was easier to do than it is to describe but let’s see how it goes.

The first step was to make a component of your knife geometry. Then I made a copy of the component and scaled the copy up by a factor of 1000. This will help to prevent possible issues with short edges and holes.

I drew the curve profile for the hollow grind at the tip and at the shank end. They’re shown highlighted above. I use Bezier curve drawn with Fredo’s BZ-Spline extension. I also erased the top face and the unneeded edges.

The curve along the knife edge and the one at the top of the bevel got weld with TIG-Weld from Sketchucation. Then the four curves were selected and I started Fredo’s Curviloft.

You’ll have to play with the settings to see what works best for you. The resulting surface will be a group. Explode it.

I pushed the bottom face of the knife up to make it half the thickness of the original blank. In the next steps the remaining geometry will get copied, flipped along the blue direction and joined to the original.

After the two halves are moved together, the large copy of the component is closed. (Exit edit mode) Then the large copy can be deleted and Zoom Extents will return you to the original.

Filling in a curved shape (Knife Bevel)

I’ve come to this thread with a similar need, ie, to draw a knife edge on an arc. I read DaveR’s post and went to find Fredo’s BZ-Spline tool in the Extension Warehouse but did not find it.

Is that tool not available for 2017 Make, or is it in one of the tool sets of Fredo’s?


Not all extensions come from the EW. BZ_Spline is available from Sketchucation. And it works just fine in SketchUp Make.


Thank you, Dave!

I downloaded the plug-in from SketchUcation (hadn’t been there for awhile) now I find I’ve forgotten how to install a plug-in.

Senior moments are useful only when hiding Easter eggs.


Didn’t you install the Sketchucation Extension Store awhile back? You could use it to automatically install BZ_Spline and other tools.

Since you’ve downloaded it, go to window>Extension Manager and click on Install Extension. Navigate to where you saved it and open it. Make sure you’ve also got the current version of LibFredo6 installed.


Thanks, again, Dave!

I was able to get the plug-ins and install them. I haven’t used SketchUp much lately and then only for simple drawings. This cutter edge is the first new thing I’ve encountered.

Now to follow your steps and see if I can learn how to use the tools.



OK, after a few hours of frustration I seem to be incapable of learning how to use Fredo’s BZ-Spline tool.

Is there a tutorial or thread or wiki somewhere that I can read to help me understand what I should be doing?



Maybe if you start here and especially with the tutorial PDF offered there.


Thanks, again, Dave!

I think I must be using the wrong tool for the job. The BZ-Spline tool draws curves that are co-planar. What I want is to draw a curve that will taper down to a center line. I’m attaching my drawing (with the model scaled up by a factor of 500 as you suggested.

This is a model of a cutting blade that is an arc with a fixed chord length and altitude above the chord. It is, in effect, a knife bevel of higher angle than a knife blade would normally have. The difficulty I’m having is in defining points where the taper begins and ends around the perimeter of the arc. Points in the plane of the blade blank stock are labeled in the drawing. If you assume points centered on the thickness of the blade stock plate below each labeled point, you will see that I want the blade to taper from Points a & b to points c & d respectively and from Point e to a point on the center line of the blade stock forming arcs where the taper begins and where the knife edge is created.

I hope this is an adequate description of what I’m trying to do and that the drawing file will help explain my goal. The object is defined as a component.

I really appreciate your help with this and your patience with me.

Kindling Splitter.skp (188.8 KB)


Probably not.

It can but it can also make curves in 3D. It depend on the how you place the control points.

So you are drawing a blade with a double bevel sort of like I did with the knife, above. You only need to draw one half of it then.

I’m not following all your points and “point D” isn’t attached to anything on the model.

Do you have an image of the blade you are working from? Do you have dimensions.

FWIW, I wouldn’t use a scale factor of 500. If you look back, 1000.