band saw and FR4

[ahbushnell]

I plan to do a small amount of cutting of FR4 with a band saw.  Suggestions on a blade?  I was thinking one with 14 teeth? 

Thanks
Andy

[kosine]

For thin material more teeth per inch is usually better, but 14 should be fine. A lower TPI blade might result in chipping, but you can place the FR4 on top of a piece of scrap material (e.g. wood) which will help.

I've never had a problem cutting it on my bandsaw which is normally fitted with a 1/4" 14TPI blade.

[ahbushnell]

Thanks!!!

[Gary350z]

I have seen many internet posts that say that cutting FR4 with a bandsaw will destroy the bandsaw blade very quickly, but I have never tried it myself.

Here's a link to cutting FR4:
https://www.eevblog.com/forum/beginners/cutting-protoboards-or-pcbs-to-size/

Here's a good video:
https://youtu.be/uBkPX_QhRI0

[kosine]

What really kills blades is heat. Anything softer than hardened steel will cut fine, and anything harder won't cut at all.

Commonist mistakes are a poorly set up bandsaw (too much tension on the blade or guide anvils biting too tightly), and trying to cut too fast. That heats up the teeth and dulls the edge - which just produces more friction and it's downhill from there.

Even cutting wood will wear out blades if you let them get too hot. (This is why high speed steels were invented in the 1800s. They can resist the high temperatures generated by faster cutting without going blunt, but they're not totally immune.)

FR4 might produce some mildly abrasive fibre dust, but even if you're cutting it all day long it's still more likely to be localised heating of the teeth tips that wears out the blade. (I've actually worn out blades cutting corrugated cardboard, though it was quite thick stuff. Material really doesn't seem to make much difference compared to the overheating effect.)

[james_s]

FR4 is made of glass, it is vulnerable to abrasion but glass is pretty hard stuff and even if you keep the blade cool it dulls in a real hurry. As long as you only cut it occasionally this may not be a problem, but I would use a cheap blade. Personally I trim FR4 with a hacksaw blade using a piece of aluminum in a vice as a guide. I can make quite a few cuts but even doing slowly by hand it dulls the blade pretty quick.

[langwadt]

tilesaw/angle grinder with a diamond blade cuts fr4 like butter with crispy sharp edges, but it is dusty

[ahbushnell]

FR4 is made of glass, it is vulnerable to abrasion but glass is pretty hard stuff and even if you keep the blade cool it dulls in a real hurry. As long as you only cut it occasionally this may not be a problem, but I would use a cheap blade. Personally I trim FR4 with a hacksaw blade using a piece of aluminum in a vice as a guide. I can make quite a few cuts but even doing slowly by hand it dulls the blade pretty quick.

I was just looking on line for blades and they sell blades for cutting FR4 type materials.  It has a carbide abrasive. 

But I'm not going to cut FR4 very often so I'll go slow and replace a blade now and then (I hope)

Thanks for all the suggestions.

[T3sl4co1l]

Use TPI consistent with material thickness (2-3 teeth in the cut).

FR4 is abrasive and will dull the teeth.  If you aren't making a habit of it, and don't mind slower cutting on your normal fare, or scheduling a resharpening sooner, you'll be fine.  If you are making a habit of it, consider a carbide tipped or abrasive (carbide or diamond grit) blade.  Simple as that.

Once worked at a shop that ripped 1" thick G10 (the ME's version of FR4) on a regular basis, using an abrasive cutoff wheel in an ordinary table saw.  Did a fine job, just don't let it cock sideways and bind up, the smoke is much more noxious than with wood.

Tim

[KL27x]

I have done it. It doesn't matter speed, the blade will be trashed fast. Cutting FR4 throws crazy sparks even on the low speed on my bandsaw. 18 inches of 64 mil FR4 per 100" 6Tpi blade. After even 6" you will notice the dullness if u use the blade for anything else. After 18", you can't even cut FR4 straight or without burning. More tpiwouod be better but it won't last.

Carbide or abrasive discs work well. Routers, circ saws, angle grinder. You can get carbide blades for 20" bandsaws, but at that price point you won't be cutting anything but expensive stock with it. Those blades are like three hundred bucks.

[T3sl4co1l]

Sparks? 

I'm not sure how you screwed that up, or what FPM that was up to.

AFAIK, even the "low" speed of intended-for-wood bandsaws is still really high for harder materials?  That might've been it.

Tim

[KL27x]

Yeah, when someone says "bandsaw" without qualificaiton, I assume the wood kind. That's what I assume the OP is using. I have the rare wood bandsaw that has a low speed drive pulley/wheel, something like half the regular speed.

Not talking a shower of sparks, mind. You can see frequent sparks, like cutting some kinds of laminate wood flooring, which will also kill a bandsaw blade quite fast; I'm not sure what's in the laminate flooring, but it's not good for blades. Of all the thing I have cut on the bandsaw, FR-4 was one of the worst ideas/results and most sparks. Let's put it that way. The first foot was super fast and clean, and 6 tpi way too few teeth to be optimal, of course. So it will work fine, yeah, for small amounts. Cutting sheet steel on a wood bandsaw also throws sparks.

actually worn out blades cutting corrugated cardboard

Cardboard is made with wood cellulose and clay. I believe it's the abrasive bits in the clay that dull the blade, not so much the heat. This doesn't deter me from cutting cardboard on the bandsaw. The FR-4 is another level. Even if the blades were free, it would be a hassle just changing them.

I cut brass rods and sheet aluminum on the bandsaw with regular wood blade, no problem. I have a metal cutting bandsaw, now, too. But by the time anyone owns a metal cutting bandsaw, they probably have at least one or two better tools for cutting FR-4 without burning time and money.


** After reading kosine's posts more carefully, now I wonder if he's using a metal or wood bandsaw. If wood, I wonder if the tpi makes that much difference. Or "trying to cut too fast" was part of my problem. I figured just let the board feed at the rate it wants, and that going too slow would be more abrasion per distance of cut. But Kosine maybe has more relevant experience with this than I.  At least I can add that chipping out was not a significant issue, IMO, even at 6 tpi.

[james_s]

Yeah, when someone says "bandsaw" without qualificaiton, I assume the wood kind. That's what I assume the OP is using. I have the rare wood bandsaw that has a low speed drive pulley/wheel, something like half the regular speed.

Funny, I tend to assume the opposite. Good friends of mine run a machine shop though all the big tools I have regular access to are intended primarily for cutting metal. I haven't seen a wood bandsaw since wood shop in jr. high school.

[KL27x]

Yeah, if you're talking a metal shop with only one band saw, they probably call it the band saw.

What I have noticed in shopping/buying, not as a tradesman, is the metal kind always has an extra modifier in front of "band saw."  Metal cutting, vertical/horizontal, portable/deep-cut. Sometime they would use two, like metal cutting vertical bandsaw, but even by saying "vertical" the metal cutting is implicit. So "vertical band saw" is a metal cutting bandsaw.

The wood kind are invariably just "band saw" and are always vertical AFAIC.

I wonder if this is the same in other countries.

Outside of Jeremy Fielding's home-made induction motor band saw, I don't know of any other that will run at both wood and metal speeds/torques. Distinguishing them would get a little more complicated if those became avaliable.

For OP's question, it doesn't really matter, I suppose. If he just wants to know what tpi is best, it is probably the same, either way.  But if he has access to a metal cutting band saw, I bet he's also got an angle grinder or 2, if not a chop saw.

Personally, I've used a wet tile saw with diamond blade. This is not bad, but the kerf is pretty large, and it is messy. A router table is a very good and very cheap way to cut and do complex shaping of FR-4. You don't need much power, at all. The smallest/weakest trim router is way more power than you need. Carbide V groove bits will score/cut with minimal kerf, but it may take multiple passes to keep the cut smooth. Carbide endmills will do the bulk of complex inner and outer shapes very quickly.

I would think a dremel tool with an extra large diamond disc would work great, if you had the motivation to build a jig for it to make it safe and precise.

[janoc]

I don't know for bandsaws but I am using the tiny Proxxon KS230 circular saw with a diamond blade (NO 28 012).

https://www.proxxon.com/en/micromot/27006.php

That blade cuts through FR4 like through butter, despite the tiny and weak motor that saw has. Don't use the HSS blade despite it supposedly being suitable for PC cards - it just doesn't work at all for this.

Just the dust is no fun - do wear a respirator and a vacuum cleaner sucking the dust away while cutting is a must.

[KL27x]

That blade cuts through FR4 like through butter

Yeah, that's the kind of blade I figure would be perfect. You can buy 50mm diamond disc to fit a dremel tool. That should be large enough to have unlimited throat depth on PCB thicknesses, in the right jig. Of course, buying the Proxxon saw would be easier.

[Pinkus]

Please do yourself a favour: do not cut FR4 with a saw or a dremel. These tiny glass needles will fill the air and stay in your lung forever (similar to asbest). Very unhealthy!!

[ahbushnell]

Please do yourself a favour: do not cut FR4 with a saw or a dremel. These tiny glass needles will fill the air and stay in your lung forever (similar to asbest). Very unhealthy!!

Dust Mask?

[janoc]

That blade cuts through FR4 like through butter

Yeah, that's the kind of blade I figure would be perfect. You can buy 50mm diamond disc to fit a dremel tool. That should be large enough to have unlimited throat depth on PCB thicknesses, in the right jig. Of course, buying the Proxxon saw would be easier.

I would hesitate to use a Dremel for this, even with some jig - these diamond coated discs are very fragile (it is basically a ceramic abrasive disc like for a grinder, not metal like a normal saw blade) and even a tiny misalignment will make it shatter, spewing high speed shrapnel all over the place.

Please do yourself a favour: do not cut FR4 with a saw or a dremel. These tiny glass needles will fill the air and stay in your lung forever (similar to asbest). Very unhealthy!!

That's why one should use a vacuum cleaner to suck the dust away (the Proxxon saw has a provision for this) and a respirator (dust mask may not be sufficient but better than nothing).

OTOH, unless you are cutting a lot of this material and are exposed to the dust constantly, I wouldn't worry too much - cutting a small board every once in a while is fine if you take the precautions above. You probably breathe in more fine particulates from the smog outside.

Probably the best way to cut FR4 is a metal guillotine but those are both expensive and take a lot of space.

[BradC]

I use a diamond tile wet saw. It's a big blade, so the kerf is large but no dust. Just a sloppy paste left over to dispose of.

[Pinkus]

Please do yourself a favour: do not cut FR4 with a saw or a dremel. These tiny glass needles will fill the air and stay in your lung forever (similar to asbest). Very unhealthy!!

Dust Mask?

A dusk mask will not be of a real help. These dangerous fine glass fibers will be in the air for hours. Though they will settle over time, but swirl up again with every draught ... day for day, month for month. A vacuum cleaner won't help a lot as their filters are usually not fine enough to hold the glass fibers.
Using a wet saw / wet PCB may be an acceptable solution.

[janoc]

Here is a safety sheet for FR4 prepreg:
http://www.isola-group.com/wp-content/uploads/IS300MD-PREPREG-Final-Dec-18-2014-.pdf

Also this one:
http://www.ifa.hawaii.edu/instr-shop/SDS/G10.pdf

Basically - ventilation, dust collection, if sufficiently low levels of dust cannot be achieved then a respirator should be worn. Also wetting the material/dust helps. FR4 dust is apparently not classified as known carcinogen (unlike asbestos!) but prolonged excessive exposure can cause lung disease (as any fine dust, likely similar to silicosis).

However, the above applies to an industrial setting, i.e. to workers who are cutting these things all day long. If you cut a small board every once in a while and use common sense and basic precautions you are most likely going to be fine.

[KL27x]

I would hesitate to use a Dremel for this... and even a tiny misalignment will make it shatter, spewing high speed shrapnel all over the place.

Thanks. That probably comes with the territory with cutting well on the edge and have a tiny kerf.

even with some jig

Depends what "jig" means to you. To me, it could be every bit as rigid as a KS230. For the cost of a couple hours and some plywood, glue, screws, and pins. I use a  cheap dremel as an abrasive chop saw, and I preferentially use only the thinnest Dremel cutoff discs, the kind that sometimes disintegrate in your hands like a Pringle while you are putitng them on the mandrel. In a proper jig, these discs will cut steel rods/screws/bolts as fast as anything, with minimal noise and kerf/dust, and once you have the disc on, breakage is not a problem. You'd never guess how many #10 machine screws you could cut on a single disc.

[janoc]

even with some jig

Depends what "jig" means to you. To me, it could be every bit as rigid as a KS230. For the cost of a couple hours and some plywood, glue, screws, and pins. I use a  cheap dremel as an abrasive chop saw, and I preferentially use only the thinnest Dremel cutoff discs, the kind that sometimes disintegrate in your hands like a Pringle while you are putitng them on the mandrel. In a proper jig, these discs will cut steel rods/screws/bolts as fast as anything, with minimal noise and kerf/dust, and once you have the disc on, breakage is not a problem. You'd never guess how many #10 machine screws you could cut on a single disc.

OK, if you build a proper rigid table where you make sure there is no side load on the cutting disc then it will probably work fine.

That is really not what I would imagine as a "jig" when "Dremel" is mentioned in the same sentence, though - I thought you were talking about some contraption where people clamp the Dremel in a vise and use the Mini Saw attachment (https://www.amazon.co.uk/Dremel-26150670JA-Mini-Saw-Attachment/dp/B0002SMNWS) or the cutting disc on a mandrel as a poor man's circular saw. That would be really dangerous.

[KL27x]

This is not me. I think the construction is atrocious. But it's kind of impressive that someone has done this so badly and yet it works (for at least long enough to film it).   

[janoc]

That is exactly the kind of contraption that will embed pieces of diamond coated shrapnel in your face if you try to use it with such disc. It works with normal (metal) cutting wheels because those flex but with the abrasive wheel that's asking for a trip to a hospital unless there is a ruler/guide to slide the material along (and thus avoid side loading the disc).

[KL27x]

It works with normal (metal) cutting wheels because those flex but with the abrasive wheel

I'm not sure what you mean by normal metal cutting wheels. I have only used a diamond disc, a few time. It must have been a different kind, because the metal-cutting abrasive discs (like the one in this vid) are way more fragile and don't like to be bent at all.  It looks like there are different types of diamond, though, made for side grinding or edge cutting.

The lapidiary/tile saws have diamond embedded in mild steel and are tough as a truck. The Proxxon diamond saw blade sounds interesting the way you described it.

The camera view of the guy cutting in the vid is something every Dremel user will quickly learn to not do, yeah! This is the reason I can't be comfortable with a table saw. Years of using Dremel tools and cutting discs makes me uneasy looking at a spinning saw blade edge on. I have a blade guard on my micro chop saw jig, even. 

[janoc]

Aah no, I mean this type of cutting wheel:

https://www.gntools.co.uk/6pc-hss-steel-saw-cutting-disc-wheel-set-fits-dremel--mini-drills-cut-off-discs-248-p.asp

That is what the guy in the video has there. That's certainly not diamond coated, just a normal HSS steel.

EDIT: I have rewatched the video and you are right, he is using what looks like a regular carbide abrasive disc. That is really dangerous, that thing can shatter with little provocation if he doesn't guide the material perfectly straight and pinches the wheel.

The Proxxon saw blade won't shatter completely (it is mild steel core, not just ceramics) but the diamond coated abrasive part can break off into pieces. Not looking straight at the blade and using a blade cover/guard along with pair of safety glasses is a very good idea regardless of the saw/blade you are using anyway - even my tiny table saw managed to kick a piece of wood back at me when I wasn't careful already.

[sleemanj]

Unless you are cutting a lot of PCBs, and I mean a lot, I wouldn't bother with any saw, a saw sounds like a cool idea sure, but it's messy, noisy, and troublesome.

Just use a carbide tipped laminate/tile cutting scribe/knife...



available from hardware stores.  Use a pair of rulers clamped down to form a slot-guide over the PCB where you want to cut, scribe it 3 or 4 times, flip the PCB and do the other side, now it will snap just like a DIY v-score.

Here is my cutting jig (hook knife is what I used to use before I had the carbide tipped cutter)...

[janoc]

That works (as does scoring with an utility knife and breaking it). OTOH, if you need to create a cutout and don't have a router, that's difficult with a knife. Saw is easier for that.