Cutting mitered edges

Software / Firmware EstlCAM
1

So a friend’s neighbor wanted to know if I could replicate a birdhouse. The one he has was made by somebody and has an octagonal shape, with an octagonal peaked roof. The pieces of which are fit together tightly.

It is old, and is falling apart. The owner is an elderly Norwegian gentleman, who is … difficult to understand, and seems.to have difficulty understanding what I’m asking. Anyway, it seems that something just like the original is what he wants.

Of course the mitered edges are easy enough on the table saw, though the 8 roof pieces are a bit harder to get the exact angles. I suspect that the original might have been made with arbitrary triangles of less than 22.5° and then joined using the kerf of a saw. If I’m going to use the CNC though, I want something repeatable. More like I want to be able to produce more than one of rhe things.

Mostly though I’m considering this as a project where maybe I can learn some new things.

So one possibility of course is maybe to 3D print the roof sections. Coat it with something UV resistant and call it done. It’s a bit big to 3D print entirely, but pretty sure the 300mm bed would let me print it in pieces, but of course that doesn’t get the wood stain finish that the current one has… it would let me have a nice “shingle” texture, so maybe acceptable? Hard to say…

Anyway, similar problems have come up with other ideas that I have had, and I would like to know if there is a way to get mitered edges in the CAM. A 3D cut shouldn’t be required, so I would hope I don’t need to base the cut off of an .STL file, which would spend a lot of time cutting air… so far that is all that I know how to use Estlcam to do this, and I haven’t actually ever done it.

I do also have Fusion360, though I have never actually used it for CAM. The parts will most likely be drawn in Fusion360. Might be time to learn to use a postprocessor for it.

Any ideas on how to get this effect? I have ball nose end mills available. I don’t mind some “stair steps” on the final finish, either.

2

What not just use a miter bit?
Altough you’d need to buy the correct angle one

If you want to cut thé beveled edge on the CNC with a straight bit, this will involve a 3d cut
Maybe a good time to move to fusion360?
First hogging out the bulk of material with adaptative cleaning , then a finish parallel pass

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Another way I’d go about it would be to cut some jig, maintaining the workpiece at the right length and angle, and then use the table or miter saw

2 Likes
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Of course that would be great… but the actual angle is going to be a weird one, unless of course I can set the roof pitch based on a somewhat standardised angle, but I think I should bet on no such luck.

I haven’t even looked at the F360 options. I started using the V1 machines 3 years ago using FreeCAD and Estlcam. I switched CAD to Fusion360 at some point, but still use Estlcam. I suppose I may want to look at it. I think these angles are going to be fairly steep, I was thinking I could probably even just make sketches at intervals down the slope, but figured there must be a better way than that…

4

Here’s what the operations look like in fusion for the above example

Adaptative cleaning

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And then the finishing pass

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Parting the stock with a contour to finish

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As you can see in the lower right corner, the machining time is pretty long :confused:

5

Estlcam can do that slope as well. I am not sure if you can ask it to ignore the big flat side or not. The actual sloped miters would be short.

In the end, it will need some tweaking to touch it up though, probably. It is worth trying.

If you want to just start with the a test of the octogon house, make one board that is 8" long and then cut it on the table saw afterward into 8 pieces. Then check the dry fit. That should be a pretty quick test. 3/8" thick or 1/2"?

Do you have any pictures of the bird house?

6

You could always use one of these to find you mitre angle and use a mitre saw.

81SBqvvQV1L.AC_UF1000,1000_QL80
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Or, if you’re set in using the CNC, get one of these.

shopping
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Tilt the work instead of trying to get it smooth in CAM. The vice worked pretty well for when I made some knife blank jigs for my brother-in-law.

2 Likes
7

I was thinking about using wedges to tilt the work too
The nice thing is you could CNC-cut some triangles out if plywood to act as wedges/supports and get them exactly the angle you need

Getting the length of the piece right would requière some maths and a good calibration though

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Can you edit tabs in Estlcam?

There’s a trick in Kiri:Moto to achieve this - just make tabs the full width and height of the cuts you want to ignore.

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I know it’s kind of cheating but could you miter cut the end of your sheet then put into Cnc and do the triangle shapes?
Perhaps you could 3D print a peek supper that gets glued on the inside like a reverse crown.
Or add the Norwegian flag ontop to help tie the apex of all the triangle pieces

10

Put a little blue tarp over the whole thing and call it a hurricane roof…