Tabs in next project

I want to make something that fits together with tabs and glue. I saw another member made a stand up desk and I like the idea. I whipped this up in sketchup:

Untitled

I have a question. I am guessing that the holes for the tabs should be made using the pocket operation in makercam. I am not sure why you cant just use the regular profile operation. Maybe someone will explain that.

More importantly what is the step over %? I left it at the standard 40%, but do not see reference to it in the help files.

Lastly, on the tabs is everyone just using and hand saw or similar to cut the radius that is left on the tab at the end of the cut operation? I a,m using a 1/4" bit. I also have a 1/8" bit and am wondering if the radius would be so slight with the 1/8" that is would not require removing the radius.

Thanks,

Mark Shelton

The pocket operation will chew away all the material (convert it to dust). A profile operation will leave whatever uncut material in the center, however, it might fly around inside the cutting area after you make the last past (assuming you don’t leave a ‘tab’ in place to hold it attached to the work piece.) Depending upon the size of the holes you are trying to make and size of router bit, a profile might eat up all the wood anyway.

I’ve never changed it, I think 40% step over means that as the router bit makes passes to cutout a profile, it “recuts” 40% of the old pass. Imagine taking a marker and going back and forth on a sheet a paper and every new line, you cover about 40% of the old line to make sure there’s no gaps…

I’ve not personally done a piece like this, but I think some people incorporate what’s called a “dogbone” into their cuts. Some CAM programs can put them in for you automatically.

images

If you sand off the edges of the pieces that fit in the hole, then you probably could get it to fit. i don’t think it will fit otherwise.

3 Likes

Using a dogbone or otherwise removing the inside radius from your slot will likely be necessary. Even at 1/6" radius a sharp corner is likely to not fit at best or splinter out at worst if no accommodation is made for the disparity between the radius slot and sharp cornered tab. With a 1/8" diameter bit, a 45 degree dogbone will likely be barely noticeable. Here is a good explanation of Dogbones

2 Likes

Thanks for the replies. I think I’ll use a hacksaw this time.

1 Like

no matter how small a bit you use, it will leave a radius that you will need to
clean up

there are three approaches to this

  1. square off the cut (like you are thinking)

  2. round off the edges of the tabs (rasp/file/sandpaper/roundover bit depending
    on the radius(

  3. dogbones (in the corner of the pockets, run the bit diagonally out just a
    little bit, .15 x bit diameter so a rectangle looks like a cartoon dog’s bone to
    leave room for the corner)

actually, I think stepover of 40% means that you move 40% of the bit diameter
each pass, so a 60% overlap

1 Like

correct…

Hello. Just to help me understand please. I’m using makercam for pocket operations, if I want less passes (faster overall cut time / less overlapping cuts), then I put in a higher percentage, is that right. Thanks! I just started using pocket operations and it’s added another layer of complexity to my designs.

Sounds like it based upon @dlang’s definition. 100% would result in no overlap.

I have a Sketchup addin that creates dogbones for you but i’m not sure if Makercam is going to cut it like I’m expecting.
Would you:

  1. Create the dogbone and then run a pocket operation
  2. Keep the rectangle and then run drill operations on the corner circles?
  3. Create diagonal path operations at each corner

1)image 2) image 3)image

Have you tried it in makercam? Technically, the pocket operation should work. If it doesn’t, perhaps “oversize” the dogbone diameter just a hair and maybe that will work.

second this. May as well give it a chance. Also, be sure that, as drawn, the dogbone areas are large enough to allow your router bit to enter into them. This is why @madgrizzle suggested oversizing the dogbone diameters (to something slightly larger than your bit diameter) as that would ensure that the CAM program would have the bit enter into the dogbone and not exclude it as being too small an area for the bit to cut.

2 Likes