Best endmills for PCB machining

Don Foreman has designed a printed circuit board for me. To give the rest of the folks in the NG a glimpse, we're building a gear hobbing control so that any HSM with a bridgy and an indexing head can hob their own gears. Don's doing the hard work - he's the brains, I'm doing the easy work.

Anyway, this is my first run cutting traces and drilling holes in a PCB. What endmills and drills last the best in this abrasive material? Also, my CNC is only good for 6000 RPM, how fast can I feed? As the pins on the ICs are on 0.100" centers, I'm looking at 1/32 endmills. Is this the right size EM?

Karl

Reply to
Karl Townsend
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It's been a while since I etched any of my own circuit boards (there are prototype houses that do much better work than I can and do it much faster)

Are you actually cutting the traces with your mill or just using it to drill the holes? Most printed circuits are made by chemically etching away a copper laminate layer rather than milling..

If you're drilling holes for IC pins, I'd say 1/32" is a bit on the large side. The IC pins are 0.022" on 0.100" centers, so (assuming plated through holes on the board) you'd want about a #72 or 73 drill. If you're installing sockets for the ICs then use the size of the socket pin plus about 5 thou.

If you make the holes much bigger than needed you run the risk of overshooting the pad (which is usually 0.050 round, square or oval) and when you go to assemble the device the larger holes lets the ICs just fall out when you flip the board over to solder the little buggers in place. A little bit of an interference fit keeps them in position nicely.

Carla

Reply to
Carla Fong

Carla J&L sells something called a router - it looks like a small end mill with diamond shaped patern up the sides - supose to be for cutting abrasive materials like PCBs I have only seen them in 1/16 dia - would like to get some in 1/32 or less - any leads, hints, suggestions?

thanx Dale

Reply to
dalecue

Karl,

I have tried do> Don Foreman has designed a printed circuit board for me. To give the rest of

Reply to
Glenn Ashmore

These are designed for CNC-routing the *edges* of the board to a defined contour. They have a kind of spade tip so you can plunge with them; they are not like an end mill.

Here's one source (it won't be the cheapest) with them down to 1/32 and 0.8mm.

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Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

For routing, I've been using diamond-coated 2-flute endmills from McMaster, 4083A15, page 2310 for a 1/8" square end. They cut FR-4 like butter at 3000 rpm and leave a beautiful edge. A little pricy at $27.45 ea, but worth it for me.

I have no idea what their long term life expectancy is in this application as I only use them to cut out prototypes and test fixtures.

As to drilling holes, I've picked up a large selection of genuine PCB drills and I use them.

Reply to
Jim Stewart

Na, the point here is too say "I did it myself". Don offered to do it for free and I still want to try it. Of course, I have a CNC machine to do the work and my son in Cad/Cam college to write the program.

Looks like I'd better find some PCB drills.

Karl

Reply to
Karl Townsend

Karl,

Try Micro-Mark for PCB drills. They are carbide. On line at:

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Bernd

P.S. A long time ago I used to do my own boards. Still have the $6,000.00 software. It's a bit out dated but still works.

Reply to
Bernd

Hi Karl,

Try

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They are solid carbide (D style) designed for mechanical pcb etching.

Only $4 each and I imagine much tougher than the wispy little carbide twist drills I break so easily. His promotional material claims they are suitable for cutting ~.010 valleys between traces.

Have not tried them, but the price is right...

I guess he also sells an inexpensive high speed spindle purpose built for them.

I have no affilliation with the site.

regards, StaticsJason

Reply to
Statics

Endmills are often 10, 15 mill solid carbide.

I'll try to remember to get the web site for more info on this. We use a 10K RPM three phase motor for a router ourselves. We don't run at 10k for most stuff.

The glass fiber in FR4 or the older G-10 is death to non-carbide.

Martin

Reply to
Eastburn

Here is one of the better if not the best pcb routers on the market. Multiple layer type. Many other things - have parts to sell.

I use one at work for pcbs. It is an old model, but functions and supported today.

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Nice people as well - spent a few days up there in class.

Martin

Reply to
Eastburn

Try a Hobby shop for small drills.

Ask a dentist if he can spare a few used mill ends.

Reply to
RetroTeckh

I have done PCB trace cutting with .032" endmills and .030" endmills. I use solid carbide 4 flute. The first machine I used only went to 2500 rpm and I cut at about 4 in/min. The depth of the cut was about .015" More recently I used a better machine that went to 4200 rpm and cut at 6 in/min. I don't know how fast you can actually cut because I didn't want to break a tool to find out. I can tell you that if you forget to crank up the spindle to

4200, like I did once, and leave it at 1000 rpm it will break the tool. For the holes I spotted them with the end mill then went back a drilled them on a miniature drill press. I used HSS drills because I didn't have any carbide and didn't have too many holes to drill. The end mills and drills are available from places like J&L Industrial
Reply to
zephyr

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