metal specific jig saw or something better

[Seapig]

I spent 6 hours yesterday fashioning some backing plates using a multi-tool. I know that anything called a multi-tool means it doesn't do anything well, which I proved yesterday.


So the question:
Is there some sort of metal specific jig saw (not just jig saw blades) that one can use for cutting shapes in metal while on board. The standard jig saws that I am familiar with bounce all over, even the high end ones. Maybe something with a very short throw and short blades might work but I cannot find anything similar on the internet.


Is there some completely different technology that I am not aware of?


Thanks in advance for any thoughts you might have.

[rwidman]

You should be able to use a standard jig saw. If the saw is bouncing around, you probably need to use a finer blade (more teeth per inch). Be sure you're using blades meant for cutting metal.

A band saw with a metal cutting blade would be better if you can fit your work on it. There are also power hacksaws for straight work.

[jimbunyard]

What kind of metal are you cutting?

If your 'high end' jig saw has an 'orbital' cutting mode. turn it off, or to its lowest setting.

If you're cutting aluminum, sometimes a medium coarse wood blade works better than a coarse 'metal cutting' blade, but they wear out faster.

How many plates are you making? A circular saw is much much faster.

If you're cutting steel, they have new circular saw blades that work very well indeed, but have to be run at much slower speeds.

[Reefmagnet]

A 4" angle grinder with a thin metal cutting disk is the way to go. Leave the jigsaw for the wood jobs.

[Rod B]

If you are just cutting straight cuts a fine toothed blade in a hacksaw will work. The material, stainless steel or bronze perhaps, needs to clamped securely to something solid, failure to do this will result in problems (and the need for bandaids often).
If you want to use a jigsaw it needs to be variable speed, run slowly with plenty of force used to keep the base in contact with the material. The blade needs to be made specifically for metal cutting and fine enough for 3 teeth to be in contact with cut edge of the material being cut. Light oil or even WD40 can be used as a lube. Set the orbital action to zero and off you go. Clamping is even more important if using a power tool.
This applies to straight and large, 2"+, radius cuts, drills and hole saws need to used for smaller radii.
Material secured, very firm grip on tool, correct blade, slow speed, no orbital action and lubricant. Best of luck.

Sent from my SM-G960U using Cruisers Sailing Forum mobile app

[Anders]

Get an angle grinder with cutting and grinding discs.

[Jammer]

Originally Posted by Seapig

Is there some sort of metal specific jig saw (not just jig saw blades) that one can use for cutting shapes in metal while on board.

It depends what you're trying to cut and how you're trying to cut it; asking for something for "cutting shapes in metal" is like asking for a knife to "cut shapes in food."


Stainless steel is particularly difficult to cut.


There are tubing cutters for cutting tubing. They come in different sizes. For thick-walled tubing you need a good one.


There are hacksaws, which are inexpensive, easy to store, and suitable for cutoff work. With good technique, reasonable precision can be achieved. They will not cut curves. Multiple cuts in thicker stock will make your arm tired and take time.


There are handheld bandsaws, which are expensive, but which can cut tubing and angle iron to length very quickly.


Though you've been frustrated by them, there are metal cutting blades for sabre saws (jigsaws) and I find that they work well for certain purposes, notably for curved cuts and cutouts in flat stock. You need a good saw, you need to use it properly, use the correct blade for the material, and hold the stock in place securely while cutting.


There are metal cutting blades for circular saws, and there are circular saws designed specifically for cutting metal. They are useful for relatively thick sheet stock, over about 16 gauge or so, that is too thick for shears.


And speaking of those, you can use shears, punches, and nibblers in steel up to about 16 gauge and aluminum up a little thicker.


You can cut with an angle grinder and there are situations where it makes sense to do that, but they are loud, imprecise, and throw sparks. They are useful for demolition and other situations where dirty metal is being cut that would quickly damage a proper blade. There are cutoff saws that have larger, thinner blades than angle grinders that are also suitable.


Then there's flame cutting. Propylene (similar to MAPP which is no longer manufactured) is compact, and with oxygen cuts well. There are smaller torches and regulators starting at jewelry size and going up from there. While not as precise as a saw, with skill clean cuts can be achieved and it's a fast way to cut that doesn't require electricity.


On the more precise and smaller end of things there are die grinders and the little Dremel tools and their imitators that you can use for cutting and shaping. They have their place. I'd much rather have a die grinder than an angle grinder on a boat.

[TrentePieds]

Quote: "Is there some completely different technology that I am not aware of?"

Probably :-)!

If you have only a few pieces to do, say half a dozen, and they are relatively small, say a few inches each way, do as it was done in days of yore, afore all things had to be "power this and power that".

The cutting speed of an electric jigsaw is far too high, so forget about that tool. If you want a saw, then use an Armstrong's patent hacksaw. Old, old rule is that the tooth count of the blade should be such that a minimum of three teeth is always "at work".

The work piece has to be clamped solidly either to the worktable or in a vise. If it's stainless steel you are cutting, use plenty of lubricant, such as WD40 or even plain water. The objective is to prevent the cutting surface from heating up, because if it does, the material "work hardens" to the point where you cannot cut it. Cutting PRESSURE should be HIGH, cutting SPEED should be LOW. If I remember right, the "standard" cutting speed for SS is 800 feet a minute. Mild steel is 1,200 FPM. You can work the math for yourself to see how many strokes of the saw you should do in a minute. "The back stroke" doesn't count. In fact you should lift the teeth of the blade off the work on the back stroke. Nothing to it - jus takes practise :-)!
The "keeper" pieces should be cut slightly oversize, say a millimeter or 1/16", and then finished to size with a file.

If the work piece is clamped horizontally to a table, tilt the saw so the maximum number of teeth possible engages the work at any given time.

As others have said, you can use a cutting disk in a grinder, but be aware that tiny, tiny bits of cutting swarf will be thrown everywhere and that it may do damage. Do NOT get it in your eyes or even your nose!

As an aside: In my day, a new apprentice in a machine shop was given a chunka steel, stood by the vise and told off to make a "1-2-3 block", a block 1" thick, 2" wide and 3" long. With hand tools, hacksaw and file, block to be perfectly flat in all planes and each side perfectly square with its neighbours. Apprentices were never permitted near the machine tools till they had made a perfectly "good" 1-2-3 block.

You won't have to be that good for your job, I don't think, but there is a moral to that story. It is: "Don't sneeze at the hand tools!" It is, inter alia, that you shouldn't be messing with a jigsaw till you've become good at using a hand saw :-)

All the best to you.

TrentePieds

[Cheechako]

Hard to answer without more info. How thick? What metal? What shape? (Straight cuts or curves?)
A Band saw us often the best metal cutting saw. The length of the blade avoids heat build up.

[waterman46]

Agree with all the above but you might get some good info on the DIY forums also.

Half of the challenge is to be able to hold the workpiece so firmly that your saw cannot make it vibrate or shift. Match the blade pitch to the thickness of the metal - thinner metal requires finer tooth pitch. Finally, the saw must be held so firmly against the work that it cannot bounce away, even the tiniest bit.

Angle grinder with cutting blade sounds dangerous to me.

For large metal jobs with straight cuts or slight bends, and thick metal including pipes, I use a variable speed reciprocating saw (sometimes called a "Sawz-All"). Cuts 10x faster than a hacksaw but hard to start the cut accurately. For the more precision jobs I use a jigsaw. In each case, the real problem is more often how to hold the workpiece firmly and still allow the saw to cut where needed.


Looking back at some of the thick SS pieces, long cuts I made with hacksaw, I can't believe I had that much energy and patience. Back then I had more time than money.

[Manateeman]

You can find special discs for Stainless Steel which will fit a 4-1/2” grinder. Try a welding supply store. The thin ones can break easily so be careful till you get the hang of it. Not cheap but they save time.
Aluminum. Small squirt bottle of alcohol. Stop and go...keep the blade cool, the work firmly supported. Sawsall the heavy stuff. Fine tooth bi-metal blades.
I use a fine carbide blade on my slide saw. Remember a tooth can fly off with the speed of a bullet so always remember you are cutting metal.
If it looks risky, think of another set up, seek advice etc.
Happy trails to you.
The manatee crew.

[Cadence]

Originally Posted by rwidman

You should be able to use a standard jig saw. If the saw is bouncing around, you probably need to use a finer blade (more teeth per inch). Be sure you're using blades meant for cutting metal.

A band saw with a metal cutting blade would be better if you can fit your work on it. There are also power hacksaws for straight work.

Or a torch.

[thinwater]

Originally Posted by Reefmagnet

A 4" angle grinder with a thin metal cutting disk is the way to go. Leave the jigsaw for the wood jobs.

This. Right after drill and finish sander, it is the next most vital power tool for working wood and fiberglass. The multitool is farther down the list.

As others noted, sanding and grinding are other functions. Very useful. With practice, folks learn to be surgical with these. Yes, eye protection is VITAL.


---
My favorite tool for cutting moderate thickness steel, aluminum, and SS for backing plates is a band saw, and most commonly a Port-a-Band. But this is not a standard DIY tool. But darn handy. For example, 3 days ago my parents (95 years!) asked me to cut up my steel childhood swing set. It took 20 minutes of easy work to cut it into a LOT of 3-foot pieces and carry them to the trash bins.

[alaskanviking]

a friend showed me this contraption which is gods gift to boaters without a shop. Milwaukee portable band saw with a SWAB portable stand. there are other brands that fit and even harbor freight has a portable band saw now. but its the stand/mount that transform these tools into something very useful and impressive. makes a nice portable bandsaw. the Milwaukee has a speed control to go from the slow metal cutting speeds to a faster speed that is useable for wood. i make all my backing plates and custom size bolts with this, and finish them with a portable 4" belt/disk sander. i have found both tools are essential for boat work

i prefer a corded bandsaw. they make a battery powered version but cutting G-10 and metal is an endurance task, so i believed it would just suck too much power. i used Milwaukee's battery powered grinder and it sucked them dry maybe 20-30 min of work. they have bigger batteries now so maybe. next make sure you get the wider mouth model. it lets you use it with bigger material, ie thru hulls ect. SWAB has a couple different versions of the stand, i got their latest and picked up the foot pedal and the accurate miter guide. i use the foot pedal a lot but haven't really used the guide. for bolts and thru hulls i use a metal "x" block. the part fits in between the arms and raises them up enough to get a straight cut. i would use the miter guide for this but the block i had wasn't long enough, so something i have to make a jig or something later.

Milwaukee has a slow speed M18 battery skillsaw made specifically for metal, i dont know about the other brands. i really want one.

Your jigsaw WILL work, if you do it right

for cutting metal: no one told me about this until i stumbled onto it later. its apparently not common knowledge as i have seen a lot of maintenance and service personnel go full tilt with their tools while cutting metal.

for metal you have to slow the speed way down, slow the speed way down, provide constant pressure, and a little bit of cutting fluid or oil. will eat through it like butter, even stainless. look up correct metal cutting speeds in google to help guide you. stainless with a drill its a few hundred RPM, similar for bandsaw and jig saw speeds. a grinder is full speed but its using an abrasive to do the work. if you go full tilt with a saw or drill it heats up the blades and bits until it loses its temper and gets soft. stainless is particularly painful because it hardens when it gets hot like that.

when i use hand drills and jig saws i keep them about 1/4 to 1/2 throttle and do my best to keep the speed down. on a drill you can switch to the slow speed/torque setting but you still have to throttle down. you have to put a lot of pressure on a drill also, the more pressure the better. drill press is better here for that reason. some times ill surge the throttle a little in those slow speeds. this isn't necessarily easy as it feels counterintuitive. if you don't do this the blade and bit get red hot and don't work anymore. if i am working with thicker metal or stainless, ill stop every so often and let it cool, give it a little oil. i went through a ton of blades and bits before i figured this out. now i can do everything with just one blade or bit. surprisingly you don't even need the expensive hard metal bits and blades. you just need simple carbon steel and carbide, even with titanium. however if your going slow and keeping things cool the better bits help

each metal has a different speed range, but they all want high pressure. you should see constant curls of metal from the bit or a uniform size of larger chips from the saw blade. when that changes the blade/bit is getting hot, you need to change pressure, or the blade/bit is getting dull. if the blade/bit gets cherry red its more than done, they're useless at that point.

For cutting G-10: its surprisingly similar to cutting metal. slow speed and constant pressure. G-10 and fiberglass is an abrasive, which really heat up and dulls your tools fast if you try to go full tilt. for a saw its easy to see when its getting dull because it has a really cool looking chip/particle, which get smaller and smaller when it dulls, until its dust. things heat up really bad when its dull also. i use water in a squirt bottle as a cutting fluid as i don't want to contaminate things with oils when i epoxy it later. tapping threads is fairly easy and fast however. i just chucked the tap into the drill or drill press and ran it through. kept it on the low speed switch of the drill and generally went full speed. its not in there long enough to get hot i guess. you want the tapp that cuts threads not the type that forms threads. regarding the saw, i cut some stuff with the jigsaw and finished with the band saw. going full tilt i didn't get half way before the jigsaw blade was red hot and most of the teeth had come off. going slow i used one blade for all of the remaining cuts, and its still good. 11 5/8" or 1" G-10 backing plates, a few 3/8". a major note about safety, its tempting to keep using the band saw after it gets dull, you have to supply more and more pressure to cut, which you need a lot aof pressure anyway. just change the blade! i cut the F out of my thumb in 2019 working late and trying to finish the last G-10 plate. put to much pressure and when it pushed through so did part of my thumb, its still partially numb. changing the blade isn't necessarily difficult but you have to pull it from the stand so its inconvenient. i since found that keeping an eye on the particle/chip size was the best indicator of when to change the blade.

my friend got one of those battery powered metal circular saws and used it to cut the outer skin of the deck and other fiberglass work. the slow speed is really good with fiberglass.

as i write this, now that i think of it it probably is similar for plexiglass which always melted around my jigsaw blade, and id have to make two cuts in the same place. i may go play with plexiglass/lexan again now.

Hope this helps,

[alaskanviking]

i misspoke, its called a v-block. they use them for machining primarily. i would never had know about them if my friend hadn't showed me.

you don't need the little clamp, we didn't use one. you mark the thruhull or bolt where you want to cut and put it in the v-block with the mark at the edge. then you put the edge of the block against the blade and cut through the bolt or thruhull. this keeps the cut edge straight and perpendicular to the blade.

then we cleaned up the cut and beveled the edge of the threads slightly on the disk/belt sander. didn't even have to clean up the threads with a wire wheel afterward. i had stumbled onto a surplus sale of bronze bolts but they were 2" or 2.5". i had to cut each of them this way to match where ever they where being installed. it was a lot cheaper than buying different length bolts. we also cut a few stainless bolts for the mast that we couldn't get the correct length bolt for.

the stand makes a really nice boat sized band saw. after i got to the east coast and had to install the last couple of thru hulls the bandsaw and stand and belt sander were one of the first tools i got. for all the little fabrication projects on a boat this set up works good for G-10, Fiberglass, carbon plate, stainless, carbon steel, Bronze and aluminum. its not the best speed for wood and you have to get different TPI blades but i have used it as a wood bandsaw to accurately cut teak with it. probably will do some of my mitered frames and teak trim pieces with it.

the saw comes off of the stand so you can bring it somewhere to cut metal that way. say cutting SS shrouds in an emergency ect.