Cutting FR4

[Speakerguy]

I want to take advantage of Advanced Circuits $33 special. They charge 33ea for 4 board min, boards can be 60sq in. If you panelize your design for multiple PCB's on one board they add a $50 charge. That is fine by me, but I don't know a good way to cut FR4 apart. I've seen boards at work that come in with V-scores where you just snap the boards apart. But what is the best way to cut up a piece of FR4 that is really several boards on one substrate? Can it be scored deep with a utility knife and snapped? Saws?

Any help is appreciated.

 

[dknguyen]

At school we have this thing that looks like a giant paper cutter, except instead of the blade on a lever pinned at one end and a handle at the other, it's like an angled guiottine fixed by vertical guides on both sides and the lever pushes down on the "blade". It has an edge but not a blade (you couldn't cut you finger on it even if you wanted to). What it seems to do is just push down past the edge of the cutting platform and shears the PCB against the edge of the cutting platform to cut it clean off.

 

[Speakerguy]

Thanks dknguyen, the word "shear" helped out a lot. The make things called PCB shears. Harbor Freight has a cheap shear for $125 and T-Tech makes a model called OA-Shear that is >$500. Assuming this is what I'm really looking for (a shear), I think I'll try the harbor freight one first.

Here is the Harbor Freight one:

https://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90757

ETA:

Actually, these look like they might be a better deal:
**broken link removed**

 

[dknguyen]

THe second one costs more doesn't it? It costs more numerically...and then it's in British Pounds! Doesn't look as sturdy either.

 

[Speakerguy]

Pounds, eh? Hadn't noticed that.

The first one isn't specifically for PCB's, while all the PCB-specific ones I am finding look like the two in the second link.

 

[jpanhalt]

Shears will certainly work well. The HF one has come up a number of times on this forum, but there seems to be a lack of real user experience with it. I tried a Boston 2612 (steel insert blade on plastic support) paper cutter with 1/16" boards, but the blade dulled very quickly. An older cutter with the cast/forged steel(?) blade might work better.

As you know, FR4 is very abrasive to the blades. One shop I was with would not allow FR4 to be cut on any of its good shears -- those were heavy duty industrial, not hobby shears.

Cutting boards remains my least liked part of any project. I cut the board to rough shape with whatever saw blade I am tired of using, then use a belt/disk sander to final dimension. John

 

[ronsimpson]

I cut PCBs with two sheet metal shears. One is a big brother to the Harbor Freight one and the other is a corner notcher that is made to cur right angles but works if the boards are less than 6 inches. FR4 is more abrasive than metal but it is not like you do this thousands of times.

About Harbor Freight & Tool King, They have the same tools as the lumber yard and sears but at ½ the price. The name on the tool is different but it is the same. Even the manual is the same with the same address. My cousin works in a metal fabrication shop, told me those China tools will ware out in two years. He uses the tools 16 hours a day 5 days a week. I use the mill about once a month. That works out to about two lifetimes for me.

 

[Dean Huster]

I used to use a shear made by Kepro (the PCB fab company) for just that purpose. They want about $500 for theirs. In addition, I made a strip of LEDs to lay on the table beneath the blade so you could see the shadow of the cutting edge through an etched PCB for very accurate cuts.

Too much of the Harbor Freight stock is junk. I didn't get even one use out of a carpet knee kicker stretcher before it fell into a million pieces. Their digital multimeters are cheap, but danged dangerous. They have no safety category rating and only a fool would use them in high-energy circuits, i.e., anywhere near 480v industrial wiring. I have a hard time believing that a professional could get decent use out of any HF tools with the possible exception of big hammers.

Dean

 

[3v0]

Shears will certainly work well. The HF one has come up a number of times on this forum, but there seems to be a lack of real user experience with it.

I posted this earlier but it seems to have vaporized. I have a Harbor Freight 8" MINI SHEAR/BRAKE ITEM 90757-6VGA.

It seems to be a copy of a Swiss machine made by Profiform (200 or 320 model) and a similar machine is sold by MicroMark.

It does a very good job. It is heavy and seems well built. Plan to spend a bit of time setting it up. This site https://www.prc68.com/I/8MSB.shtml has some helpful info on it.

Question: I have forgotten how to upload an image and then include the pic in the text of the post.

 

[jpanhalt]

Everything looks good about the HF shear. My concern is simply the quality of the steel in the blades. It would be really slick if one could adapt a carbide blade, like are used for scrapers, to the HF shear. I was thinking of something like a rabbit cut in the original blade and using an industrial adhesive to attach the carbide.

Unfortunately, my local HF stores don't stock that shear, so I can't actually see one without buying it.

3V0: Are the HF blades 90° or acute beveled (i.e., can they be flipped to get 2 cutting edges)?

John

 

[3v0]

3V0: Are the HF blades 90° or acute beveled (i.e., can they be flipped to get 2 cutting edges)?

John

You can flip them 4 times for 4 fresh edges. I still have mine on the first edge but have no idea about how many cuts I have made.

The unit is also a brake but I have not taken the time to learn to use it. The manual for the Swiss unit mentions punches.

 

[k7elp60]

I have one of those shears, the one on this forum that is from Harbor freight.
I purchased mine from Northern tool about 3 years ago. It may be slightly different but all the pictures posted sure look the same. I use it to cut my home made PCB's. Most of them are fiberglass .062 thickness. It has served me well during the past 3 years. The bigest problem I have is holding small boards to get a straight cut.

 

[jpanhalt]

Thanks for the user reports. I guess I am in the market for one of those HF shears and will stick with the steel blades.

The lack of hold-downs is a disadvantage, but I suspect one could put a guide along one edge to make it a bit easier to hold the board.
John

 

[3v0]

Thanks for the user reports. I guess I am in the market for one of those HF shears and will stick with the steel blades.

The lack of hold-downs is a disadvantage, but I suspect one could put a guide along one edge to make it a bit easier to hold the board.
John

There sort of is one already. If you butt the edge of the board up against one side or the other it will cut at 90 degrees. The down side is that you only have about an inch to act as a guide. It works for me.

 

[Shax]

I use a small electric tile cutter with a diamond blade... Water cooled and therefore has no dangerous abrasive dust in the air..
Works great for splitting the sheets of small pcb's that I get made..


**broken link removed**

Mine cost GB£29.99 about 8 years ago... Must have cut about a mile of FR4, and countless tiles too!

 

[picbits]

I use a small electric tile cutter with a diamond blade... Water cooled and therefore has no dangerous abrasive dust in the air..
Works great for splitting the sheets of small pcb's that I get made..


**broken link removed**

Mine cost GB£29.99 about 8 years ago... Must have cut about a mile of FR4, and countless tiles too!

I'll second that for a nice easy way of cutting PCB in quantity.

I don't use mine with water - too messy but it cuts through FR4 and other composite without breaking a sweat.

Not too accurate but as good as a cheapo bandsaw with a skinny blade at a lot less cost per cut.

 

[bigal_scorpio]

Tile cutters are PCB cutting heaven!

I agree with Shax, I have been using my (Wickes) tile cutter for years now, and it still cuts cleanly and thats after its original use for the tiling jobs I bought it for!

I think it cost me £20 about 8 years ago.

Al

 

[positronicle]

I've got one like this, and couldn't be any happier with it. It's really amazing what that thing will cut.

**broken link removed**

 

[jpanhalt]

I have seen that style too. Do you have any problem with the board trying to twist or scoot out from the blade, as the shearing action is at quite an angle compared to the guillotine cutters? John

 

[positronicle]

I have seen that style too. Do you have any problem with the board trying to twist or scoot out from the blade, as the shearing action is at quite an angle compared to the guillotine cutters? John

I've not had any issues with twisting(left or right), at all. Just like scissors, it naturally wants to cut a very straight line. The left hand side of your work will surely want to kick up, however. That is why you should always make sure that the "hold down" is adjusted flush down on your material, before you begin your cut. In order to protect more delicate surfaces I added a piece of thin foam(peel off sticky on one side type) to the "business" surface of the holdown. I took a picture of it, but it didn't turn out real clear. Hopefully you can see what I am referring to.

**broken link removed**