Fiberglass/PCB on Bridgeport


I’d like to cut down (about a half inch of each side) a blade connector on a PCB, and I’d like to do so accurately as possible.

Is there an issue cutting Fiberglass on the Bridgeport or Sherline Mills providing I clean up after myself and wear a mask? I only need to remove maybe a square inch of material, so it’s not like it would be a large dust volume issue.

For those who are curious, I need to make the bottom PSU match the top PSU:

@TBJK @nicksilva


Should be ok. Clean up well and make sure people around you are aware and have a mask if needed


I haven’t milled much fiberglass, what would you recommend? Just a P95?

Also, I’ll look up the correct feeds and speeds, but I’m at a loss for what I should use as lubricant (not sure I can use anything but IPA on the PCB, and that is probably dangerous) or if I can even use a standard HSS end-mill.


I would consider a dremel with a cut off disk rather than the mill. Mark and trim, then sand if needed.

I say that because little mistakes on the mill could tend to turn into big mistakes fairly rapidly with something as brittle as PCB material.

Just a though.


That was the fall-back plan if the Bridgeport was forbidden. I need to make 4 of them, so I’d like some repeatability and I have the worst luck with dremels.

I know what you mean about little mistakes on the bridgeport. Planning to clamp firmly and not do anything rash.


When we routed PCBs at my last job it was done dry with uncoated carbide. We had a fancy HEPA vacuum that encircled the bit but we went through a lot more material than you’re talking about.

I’d also recommend rinsing your arms off in cold water when you’re done, the dust can settle everywhere and make you itch for a day or more.


Regular high speed steel should work. The fiberglass is quite abrasive and will wear the tool quickly but since you’re only doing a couple it will be fine. I don’t think you’ll need a lubricant although ideally air assist would be helpful .
You might also try rigging the small vacuum hose to one of the flexible arms to get it right up to the tool


That sounds like something worth trying. Thanks for all the advice everyone.


You’ll want the smallest cutter you find, four or three flute. Biggest problem is Bridgeport turn about an order of magnitude slower than a Dremel warped up or a PCB Mill (which is basically a small router in the 20K-30K rpm range). A four flute cutter will act more like a two- going twice as fast in this type of material. (Note: this is a guess on my part, I’d Go the Dremel route then clean up edge with abrasive wheel on Dremel. Max spindle speed on Bridgeport is less than 3,000 rpm.

Now if you could get it into Haas … you’d have much higher RPM!

You may get a very rough edge with tears/delaminating the FG and the foil on the FG. It WILL cut it, not sure how satisfactory it will be. It’ll cook the metal fine. No lubricate should be needed


Visual inspection tends to suggest that this isn’t going to produce the result you desire. Those connectors are incompatible for a reason.


The difference is the physical width and current carrying capability of the PSU. I’ve checked the pinout, and there’s forums posts of people claiming they’ve done it successfully with my exact backplane (and replacing the PSU I currently have).

The PSU is capable of an extra 300W, and it needs the extra copper. Since I don’t draw that extra power, and I don’t plan on it, I should be fine.


This is where a miniature table saw would come in handy. :slight_smile: