Sometimes I need to widen holes on my project boards to push a wire through to the back side, insulation and all, and I just use a Dremel tool with a 1/16th inch bit. On FR1 boards this works 100% of the time. On FR4 boards, I seem to break it every 20th hole or so, a really unacceptable rate. I run the Dremel at the highest speed, 35K RPM, and use a Black & Decker "bullet" black oxide bit. Got the bits at Walmart, are they OK or crap? Should I try it slower or do you have a suggestion for bits? Or is using a Dremel just a bad idea here completely? Maybe I can't hold it steady enough and it ends up biting when I remove it if I have some angular movement in my wrist other than the exact angle it went in? But I like doing it with a Dremel, it's very convenient. Any ideas?
Two ideas...
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I have had good luck using a brace + drill bit to put holes in "brittle" plastics...
Brace (tool) - Wikipedia -
I suspect a tapered cutter would work much better than a drill bit.
Black oxide drill bits are pretty much on the bottom rung of the drill bit ladder; they coat them with black oxide because the cheap steel needs rust prevention and/or they don't want you to notice how poorly polished they are. You really want to look for bits that have a clean, polished finish (cobalt steel) but buying from retail stores you really never know what you're going to get. 35K RPM is also much too fast; I'd go for about half that speed.
It's pretty difficult to make a recommendation here. Small diameter bits are very sensitive to runout (wobble) in the tool spinning them and Dremel tools aren't very good when it comes to runout. You might have some luck poking around on eBay, but be sure to avoid carbide bits as they are much too brittle to use with a handheld tool.
This answer on EE.SE may have some useful info.
Hi JoeN,
I use a Dremel too, but free-hand find I soon brake tungston bits, my friend gave my stocks of FR4 double sided board, but most of the time I'm happier with the cheap SRBP stuff, as I can use a normal HSS bit which last longer, but not it's much good with the good stuff.
Regards
Mel.
RogerRowland:
This answer on EE.SE may have some useful info.
Thanks to everyone. The above info was a very good find. They seem to all be saying what I said - FR4 is a bitch, lateral forces are the killer. I like the idea of the Dremel workstation. I will have to try one of those and look around for carbide bits for it and see if they work out better. Also, slower speed.
Carbide bits are a must imo for fr4.
Virtually impossinle to use by hand as they snap very easy.
For slots i often use the thin dremel cut off wheel which seems a bit more forgiving
Widening holes with a carbide drill is a no no. Even in a clamped machine.
Second drill tries to centre in smaller hole and runout snaps it.
Have to drill correct size first time.
You have probably discovered that high quality tool steel bits dont last long with fr4
Boardburner2:
Have to drill correct size first time.
Well, that is just not a possibility with pre-drilled prototyping boards. Maybe I keep using the cheap bits. They seem to work OK at slower speeds now and maybe will work even better with a press. I don't mind if they wear down somewhat fast - the bits are two for $1.50 at Walmart. I just would prefer if they stop breaking so often. I am a hobbyist that makes a few holes on a few boards, this isn't a manufacturing operation where I have to drill hundreds of holes on thousands of boards. This last board I widened about 20 holes in it.
Yes , i do the same, iv just had to learn to put up with a high level of breakages.
Populated boards are impossible to mount flat on a drill base anyway.
I find a proper drill vice to be very useful for this as they only need a few mm of board edge to grip well.
Useful for soldering too
Boardburner2:
Carbide bits are a must imo for fr4.
Seconded - best not to try to drill free-hand you want a small drill-press for this
size of drill in brittle carbide.
Boardburner2:
Populated boards are impossible to mount flat on a drill base anyway.
Clamp the edges of the board in a drill-press-vice or equivalent jig - the
sort with lots of handy V-grooves.
The effects of quill wobble and excessive downward force are the killers here.
Place the drill in the chuck way past the drill shank, even so the flutes are gripped in the fingers.
Less will be left exposed and unsupported (and able to wobble and bend and apt to snap.)
Get just enough to clear the board and a bit more and what more that you may need to see what you're doing.
Hi,
Yes I can agree with that, you only need 5mm. less wobble, less chance of breakage! Carbide drills are good for FR4, in fact I don't think you can use much else, unless it's one drill per board. Yes I too have thought about a drill press, and the Dremel looks good, but I think I can work quicker free hand, and sort the odd miss up later.
Regards
Mel.
As an aside, i use boards these days which are a sandwich of Fr4 over an srbp core.
Much easier to drill and with the properties of fr 4 on surface
http://www.megauk.com/pcb_laminates.php
Scroll down fpc 16
Boardburner2:
As an aside, i use boards these days which are a sandwich of Fr4 over an srbp core.Much easier to drill and with the properties of fr 4 on surface
http://www.megauk.com/pcb_laminates.php
Scroll down fpc 16
You are kind of hard-core compared to me. I either buy "pad per hole" prototyping boards or just have the thing made. I don't make the PCBs myself. The whole issue goes away if I have a PCB manufactured. There is no issue with FR1, they are easy to drill. FR4 is the killer. For example, the pad per hole boards I typically use are:
FR1:
http://www.taydaelectronics.com/prototyping-board-142x74mm.html
(good quality, easy to drill)
FR4:
http://www.ebay.com/itm/40pcs-Double-side-Protoboard-Circuit-Prototype-DIY-PCB-Board-2x8-3x7-4x6-5x7CM-/111278031424
http://www.veroboard.com/5x10-5000d-epoxy-fiber-pitch-01-254mm-p-41.html
http://www.ebay.com/itm/Prototype-PCB-Universal-Printed-Circuit-Board-Breadboard-Protoboard-10x16cm-/310830807081
(excellent quality, hard to drill though)
In all cases, when trying to mill FR4, rather than drill, make a very light cut each time. Never try to make the whole cut on a single pass. The burr or end mill will try to deflect sideways and will eventually break.
Paul
JoeN:
You are kind of hard-core compared to me. I either buy "pad per hole" prototyping boards or just have the thing made. I don't make the PCBs myself. The whole issue goes away if I have a PCB manufactured. There is no issue with FR1, they are easy to drill. FR4 is the killer. For example, the pad per hole boards I typically use are:FR1:
http://www.taydaelectronics.com/prototyping-board-142x74mm.html
(good quality, easy to drill)
FR4:
http://www.ebay.com/itm/40pcs-Double-side-Protoboard-Circuit-Prototype-DIY-PCB-Board-2x8-3x7-4x6-5x7CM-/111278031424
http://www.veroboard.com/5x10-5000d-epoxy-fiber-pitch-01-254mm-p-41.html
http://www.ebay.com/itm/Prototype-PCB-Universal-Printed-Circuit-Board-Breadboard-Protoboard-10x16cm-/310830807081(excellent quality, hard to drill though)
No arguments there, i only build these days if it has to be a pcb and i cant wait for china.
Makeing the boards is very time consuming.