Over the past couple of years lurking on this forum it seems that many new builders are intimidated at the prospect of building their own flat bits without a CNC machine to do it for them. If anyone can make suggestions for tags to add to this to make searching easier in the future, I’d appreciate it.
If a picture is worth a thousand words - here’s a boxed set of War and Peace. It’s simple, and a low level of skill will yield a result that will be difficult to tell from the real thing, and it won’t take all day to do. The time stamps on these photos tell me this example took a little over 30 minutes, and I had done nothing in the way of preparation before hand.
Tools you will need:
- access to a 3d printer
- a drill
- a trim router (the one you are going to use as a spindle will be fine.
- a pattern bit for the router.
Optional tools that will make the job easier -
- some kind of saw, a jig saw would be great for the internal cutouts.
- a glue gun
Some knowledge of CAD is going to be essential at some point of the build process. At the time I built my first plates I was floundering trying to open that .dxf file and scale it on paper, so that was the first problem I had to solve.
The simplest and most accurate way to do this is to print a 3d template rather than relying on the vagaries of paper. Open the DXF file in your 3d software and extrude the plates to a depth of about 4mm.
I like to cut chunks out of the plate that won’t be needed to save a bit of plastic when I print templates - you only need the perimeters and all the holes located. To confuse things a little more, the plate pictured is not the standard plate, but one that’s been modified for the Makita 700 router, however it does serve to illustrate the process.
- Print the Plate at the most efficient speed you can consistent with accuracy - extrude to at least 4mm to allow enough space for the bearing of the router bit you will use later.
This is printed with .4mm nozzle 10% infill, .3mm layer height Prusa Slicer “Draft” mode.
- Grab the board you are going to use, take a nice fat sharpie and trace around the bits you want to cut out. Neatness doesn’t matter and as long as you don’t move the template while you’re doing it you’ll be OK.
- If you have a saw, cut out the rough dimensions of the plate. Leave at least some of that sharpie line for later. If you don’t have a saw, you can use your router/trimmer to do the job but clamp a straight edge as a guide and take a couple of passes for the thicker plates.
- If you don’t have a jig saw you can chew out the inside bits by connecting a series of drill holes. This is not the neatest way of going about it, but it works. Again you can freehand this cut with your trimmer router, but that takes a little practice so take care.
- I used a jigsaw - just a cheapie that I’ve owned for forty years or maybe more - you really don’t need to worry about being fancy here either.
- If you have a glue-gun, a couple of squirts will be sufficient to hold the template to the plate. Or you can use double sided tape, “the masking tape and superglue trick”, or even just run a couple of screws through the holes that you are going to drill out later. If you do that, remember you don’t want to catch the router on them so you might have to move them a couple of times during the process.
- Once it’s stuck together it should look like this, with all of the sharpie lines visible.
- Now, about a week ago so that you’ll have it now, go to your favourite el-cheapo vendor and buy a 6mm or 1/4" bearing flush trim router bit. This one was complete rubbish, cost less than $5.00 including postage and only has to last a few minutes, which it has done many times over.
- Lock the bit in your router and adjust it so that the bearing rides on the template and the bit covers all of the area you want to cut. Lock the router in position firmly - if the bit moves while you are using it the result can sometimes not match your expectations.
CLAMP OR SCREW EVERY THING DOWN BEFORE FIRING UP THE ROUTER.
Run the router around the template carefully. Don’t try to cut too deeply if you have left large margins, just be patient and take a bit at a time. If you get greedy, If you try to cut the lot in one hit, there’s a risk that you’ll slow up the cut, the bearing will warm up and your PLA template will react accordingly.
- Now take your drill and carefully, using the template as a guide, drill the holes. I’ve made all the holes in the pattern 4.1mm and I’ve used a 5/32" drill bit because I’ve owned my l bit set since before Australia went entirely metric and it’s a lot cheaper to replace individual bits when they break than to buy another set, even if that was in 1974!
Just be careful not to get too excited and heat the drill bit - a hot drill bit in a PLA template is not conducive to accurate drilling! If you have a drill press - this would be a good job for it.
- Use a knife or a scraper to separate the parts.
FINALLY - Sand the edges very lightly to remove any furry bits. (I’ve used 240 grit on a timber scrap). Don’t over-do it , if it takes more than a few seconds you’ve been at it too long.
If all has gone well, you’ll have a “temporary” set of plates that will look as though you’ve bought them.
Thanks for hanging out for so long, I hope that’s helped!