Drawing a saw blade - help!

Many thanks to Gary for his comprehensive description of how to kerf teeth on a hole saw with Fusion360. My next job is to replicate it in SolidEdge. (Almost certain the method will work, but I'm finding SE harder to drive than Fusion.)

Made progress on the third problem which is getting a pattern repeated cut to follow a wavy line projected on to a cylinder. This example punches a series of holes up, down and around a cylinder, and in principle it should work with teeth profiles:

Huub's suggestion of FreeCAD's Curves Workbench is on my To Do list, and I agree with him that planning with a spreadsheet is a good idea. The teeth don't line up in my attempts because I winged the dimensions rather than doing the sums.

I've already had a go at Howard's suggestion but - so far - not found a way in SolidEdge of bending a straight strip with teeth into a circle. I'm going to try again this morning. Feels like something the tool should be able to do.

Thanks to all

Dave

Re Howard's suggestion - drawing the teeth on a straight strip and then rolling it into a circle. Turns out to be possible with SolidEdge Sheet-metal but not as I expected!

The trick is to:

1. Draw a circle with a break in it.
2. Extrude the circle with 'Flange Extend' to create a cylinder (with break)
3. Unbend the cylinder (a button) , producing the flat strip needed to make it
4. Add teeth to the flat strip
5. Rebend to put the flat strip back into circular form. (another button)

Image shows the Rebend action just before confirmation:

Dunno what's going on today, people keep me ringing up and banging on the door. Feels like family, friends and Postie have organised themselves to cause maximum disruption.

Dave

That was my first suggestion too, to draw it flat and roll it up like they are made.

Can rolling it up include the set of the teeth?

Seems not! So close and yet so far...

Back to the drawing board!

Dave

This was an interesting study. I tried an approach using expressions so the user could pick the TPI and diameter and the geometry would auto gen. I had 16 TPI in this one, which is pretty tight. Another design consideration was the outside diameter measured from the outboard cutting edges didn't necessarily match the pitch, so the pitch was adjusted slightly to meet the O.D.

Another thing is that I don't know how Alibre handles arc lengths. It doesn't do radians. I did manage to create geometry but was unsuccessful in automating all of the inputs.

In retrospect, as someone else mentioned, it would be better to force the TPI and the diameter together, so when the steel is rolled and welded, the teeth will be offset at the weld.

Nice! My mind is mathematically weak and I hadn't thought of expressions.

Now the idea has been demonstrated, this might be the best way to do it. Kerfed teeth on a curve are a general problem like gears. They're drawn with a macro or built-in program doing the maths, rather than the operator tracing curves manually.

Dave

Alibre does do radians - but it will display in your chosen preferred angular unit.

Alibre works internally with radians, like many computer systems do - so an arc length is simply given by

arc length = radius * angle

Alibre's equation editor is VERY FUSSY about variable typing, which can lead to some unexpected problems if you are not aware of them.

This page may be helpful - it's on an old system, so could vanish (I can provide it as a PDF if needed).

Awesome. Thanks for the tips. I'm still pretty new with Alibre.