Micro Table Saw
For years, I've been cutting PCB's freehand using a dremel tool and a cutting disc. It works well but the dust and less than perfect edges bothered me.
An option was a PCB guillotine but it costs a fortune and the resulting cut edge is still rough.
An idea that has been floating around in my head for quite a while now but did not have the time or motivation to build one: A micro table saw with a diamond cutting disc for cutting PCBs.
There are a lot of miniature table saws that you can buy but most use teethed saws which I think would not cut cleanly through FR4 (I haven't tried it so I don't know for sure) plus if it isn't carbide tipped, would be blunt in a few passes of the abrasive fiberglass PCB material so I decided to make one that used a diamond cutting disc. This was the result of an afternoon's work.
The "underchassis" of the table saw. An MDF base, two sealed bearings and steel shaft from torn down copier, chuck from some old burnt out AC powered Dremel knockoff and some alu brackets to hold the work surface.
Detail of the bearing pillow block machined from polycarbonate.
The heart of the table saw. This is a fairly old Dremel "chainsaver" used for resharpening chain saw chains. It runs on 12V and is powered off my renewable energy system in my workshop.
A grinding bit used as a convenient shaft for the flexible coupling.
Flexible coupling using a silicone tube.
Cutting disc spinning at about 15,000RPM.
The bottom side of the plexiglass work surface milled to clear the chuck, and holes milled to clear the blade and bearing.
The cutting disc protrudes exactly 2.5mm above the work surface so that dictates the maximum thickness of material that can be cut in one pass, the yellow-green material is 1.6mm thick FR4 PCB.
Test cutting various 1.6mm blank FR4 PCBs and the makeshift 'fence'.
I tried cutting 3.5mm thick plexiglass sheet. One pass isn't enough but it worked well when the piece was turned over and run a second time.
The complete micro table saw clamped on the work bench, work surface is 10 inches by 5 inches.
Rotary tool placed on top of a piece of alu extrusion simply held by gravity.
Later added a foam cap on the end to keep dust contained under the work surface.
The test cuts showed promising results. Now, I can make PCBs with nice edges and little waste. My next plan is to make a simple adjustable fence that can be clamped easily to the table. Stay tuned!
07 Sept 2012:
The alu extrusion wasn't all that effective as a motor mount so I made a new one from acrylic and M4 allthread.
The flexible coupling also had the habit of vibrating then jumping out so I added an aluminum sleeve to keep it centered.
Dremel in place on the motor mount.
View of the cutting disc.
Also added a spring under the motor to provide some forward pressure to prevent the motor moving backward.
08 Sept 2012:
I had an idea of how to make a chamfer using the micro table saw. Add a guide along the axis of the saw.
...and let the blade protrude just enough.
Then slide the workpiece along the guide and you get a nice chamfer.
Dust collected from cutting circuit boards and acrylic sheets.
20 Jan 2013:
The flexible coupling keeps on failing when I'm cutting material that requires a bit of torque from the motor so I made a hard coupling from polycarbonate.
First thing is to drill a hole on the side of the grinding bit that is used as a shaft.
Here are the parts needed for the coupling. A donor grinding bit used as a shaft, a short piece of paperclip wire, the polycarbonate coupling, the setscrew and a piece of silicone tubing as a cushion between the two shafts.
All together on the table saw. The short piece of paperclip wire is used as a pin to prevent the shaft turning in the coupling but allows some play.
A bit of heatshrink tubing holds the pin in place and prevents it from flying off and hitting someone in the eye while spinning at 15000RPM.
Here it is spinning with very little vibration.
The dust that has been collected since I've built this thing. I've used this table saw to cut PCBs, acrylic sheets up to 5mm and 1mm aluminum sheet (with lubrication).
With the new coupling, the spring under the motor holding the Dremel in place is no longer needed so was removed.
30 Aug 2013:
I had a batch of 50 PCBs made and I had 7 designs made into one panel so I had to cut them to separate the different designs. Here are a few pics using the micro table saw to cut them all apart.
Fiberglass dust everywhere (breathing filter recommended)
Aluminum angle bar is clamped to the table and used as a fence.
Rinsing in IPA to remove excess dust.
Different designs split up.
Here are a test build for the different designs.
19 Jul 2015:
The old micro table saw works well for FR4 PCBs but produce a ton of fine dust and clogs when cutting thick acrylic or Phenolic. So I made a new one.
This one is bigger and uses 50mm blades made by Proxxon for their micro table saw.
I chose this as they have carbide tipped and solid carbide blades. Perfect for cutting fiberglass without going blunt.
The table supports are slotted and the long bolts and wing nuts keep them in place after adjustment of desired blade height.
The table can be tilted up for access when changing to different blades for different materials.
Power jack on left, power switch on right.
The table saw is powered by a 16V laptop brick.
I feel it is a little underpowered so I might need to find a 24V brick.
A front view of the blade. It protrudes up to 12mm above the table.
Here it is retracted for shallow cuts.
I had the brass pulley and steel arbor turned from a lathe to fit my 8mm shaft.
The motor, larger pulley and belts came from an 80's bill counter that I tore apart.
The rear bearing does not support much weight but needs to be tightly fixed as it keeps the shaft from going in and out keeping the blade in the middle of the table slot. The spring keeps tension so that the shaft holds to the bearing tight.
The front bearing holds the blade and also supports the belt tension so it is simply press fitted to the aluminum frame.
A drop or two of loctite (which can't be seen as it seeped in) keeps it in place.
Blade spinning. This is dangerous!
From the front of the blade.
With the table in place.
I bought three blades to try out. 10T, 20T and 80T.
The space in the middle can be a convenient place to store the blades.
Test cuts. The thin slot on the left was cut by the 80T blade. It is very clean. The ones on the middle and right are cut by the 10T and 20T. There is not much difference between them.
The 80T blade cuts very nice on FR4 material. The edge appears polished and very smooth.
I also tried cutting acrylic but it is not as good. The 10T and 20T blades worked much better for it. With the 20T blade, I have cut up to 3/8 inch polycarbonate sheets. Although the saw stalls when the material is fed in too fast, it cuts fine going slow. Next on the list will be an adjustable sliding fence.
After playing with it for a while, I had to do some more mods. I mounted springs under the table. They push the table up when the bolts are loosened so it is easier to adjust blade height.
I also machined some polycarbonate blocks as a guide for the bolt heads. This prevents them spinning around when the wing nuts are tightened.
These were made using my micro mill.
With the table all the way up, the springs could be seen underneath.
The bolt heads can be seen here guided by the slot in the polycarbonate block.
There is still enough room to fit the extra blades!
As a side bonus, the mini table saw just fits on my trash bin. This makes a good dust collector and most falls into the bin with only a little going everywhere else.
Page created and copyright R.Quan © 02 Sept 2012.