Cutting a boom with a chop saw?

[ProDave]

I have posted before our boom has a bend in it (it was like that when we bought the boat) We have now acquired a replacement second hand boom but it is too long and will need shortening. It sounds simple to cut an aluminium boom (having removed one of the end fittings) but we want it to be a neat cut.

The most obvious to me tool to use is my chop saw. It uses a 210mm diameter blade with a 30mm mounting hole. The finest blade I presently have is 48 teeth, that is a total of 48 teeth around it's circumference so 11mm tip to tip. But the blade says it is for hardwood, softwood, chipboard or other composite materials.

It is possible to buy a blade for this saw that is rated to cut metal but it costs about £60 and still only has a total of 48 teeth.

So what is likely to go wrong if I use this hardwood blade to make 1 cut in an aluminium boom? So I guess the question is, has anyone tried something like this?

I see plenty of joiners cutting aluminium window sills etc with these "wood" blades without issue.

 

[Daydream believer]

Best thing is to cut the boom plenty long enough to see what happens. If it starts to go tits up you can stop & will not have damaged the useable bit of boom. You could also cut the old boom as a trial first. Make sure that it is well restrained to stop it jumping about.
Then you know what is going to happen. With the right goggles & face mask You might get the odd tooth fly out but with a decent guard on the blade it should protect you. If not it will just sting a bit & be OK once the pain has gone.

 

[vyv_cox]

A hacksaw is the perfect tool. Use a fine blade, 24 tpi perhaps. Mark the cutting line all around the extrusion, then cut along it. Do not try to cut right through with a single cut. Keep rotating the boom, cut following the marked line.

 

[Blueboatman]

Practise a couple of times first. The boom needs to be pretty secure and wobble free . A proper bench with a ledge step or original workmate are ideal not some tippy diy thing !
All the energy has to go into the cutting not the vibrating

 

[Ian_Edwards]

Does your saw have tungsten carbide tips?
Is it new and sharp?
Providing it can be held firmly and you keep the boom at 90deg to the blade, it should work.
But if it was me, I'd use a hacksaw, as advised above. I think that there is less chance of making a mess of it.

 

[davidmh]

Just follow Vy Cox's advice, you will get a clean job an acurate job and be safe. Why does everyone think they must use a power tool for everything.
David MH

 

[andsarkit]

Measure down from the existing square end and put several marks around circumference of the boom. Use insulating tape to go round the boom on these marks. You can easily check if it looks good and then cut with a fine tooth hacksaw rotating it as you go. Clean up the cut with a file. I did this to the base of my mast to remove about 10mm of corrosion and it was very easy. When you refit the end plug use some non corrosive silicon to avoid any further corrosion. Also refix with self tapping screws rather than pop rivets as you may want to open it up again to rethread reefing lines.

 

[ProDave]

The reason I am considering the chop saw is I expected that to give a cleaner, straighter cut than a hacksaw as long as it is set up and clamped properly.

Good tip about cutting around gradually if using a hacksaw. I might try that first cutting it a bit longer than needed first to see if I can get a straight enough cut.

I usually use Duralac when joining parts like this.

 

[zoidberg]

Saving access to a proper eng workshop, this is the right tool. It needs a suitable blade.

The 'mitre box' vertical guides can be replicated easily and cheaply using a wooden or ( right size ) plastic mitre box.

 

[Poignard]

Saving access to a proper eng workshop, this is the right tool. It needs a suitable blade.

The 'mitre box' vertical guides can be replicated easily and cheaply using a wooden or ( right size ) plastic mitre box.

So happens I have one of those to sell. A high quality one with a long bed and I may even have a metal cutting blade for it.

 

[snowbird30ds]

Mark it all the way around and hack it close and finish to the line with a grinder with 60 grit pad or flap wheel, you have lots of control and get a good finish.
Run a file around the inside if cables run down or there will a sharp edge to cut into them.

 

[Sea Change]

I've cut a mast with a chop saw and it did a very good job. I was putting a 45⁰ angle on it so I needed precision. It felt a bit wrong but I'm not sure that it damaged the blade all that much. I just used whatever blade was already on the saw, it didn't owe me anything by that point.

 

[thinwater]

I'm with Vyv.

To mark an accurate 90 degree cut, wrap a sheet of paper around it such that the paper lies flat, and trace the edge. Common practice, they even makes wraps for this purpose. Welders use wraps on pipe for when it is not practical to take the pipe to a chop saw or band saw--for example, the other end is welded in place. They then might use a Porta-Band, torch, or angle grinder. But a hacksaw would be my choice if I did not have a metal-cutting devise handy. As Vyv said, work your way around. A good clamping system is important. Very accurate. Clean up the cut with a mill file if you seek perfection. In the days before power tools for everything, machinists did incredible things with a hacksaw and files.

 

[Chiara’s slave]

It’s hardly hard work with a hacksaw. The job will take 15 mins doing it carefully.

 

[Daydream believer]

. Why does everyone think they must use a power tool for everything.
David MH

Because it is quick easy accurate & neat. Saves a load of work effort.
But if one is incompetent with power tools, then better stick with a toy

 

[Rappey]

I cut my boom down with a hacksaw. Got a surprisingly neat cut all the way around

 

[wingcommander]

Regularly cut boiler flues sometimes vitrius enamel steel sometimes aluminium sometimes plastic around 4" diameter with good ole fashion hack saw . As Vic stated masking tape , draw your cut line and rotate .File to remove burs. A boom can't be much different.

 

[Poignard]

Sawblades for cutting metals have fine tooth pitch, for a reason.

The OP's chopsaw blade has a pitch of 11mm.

A fine tooth chopsaw blade will cost him £60, he says.

Is he likely to need to use it again? If not that's £60 wasted, and another useless item cluttering up the workshop.

For considerably less than £60 he could, if he doesn't already have one, buy a hacksaw frame and a blade with which he could easily make the cut; and be left with a tool he could use again and again for all kinds of jobs.

 

[DownWest]

I often cut ally sections. The blade is 210 diam with 64 tungsten teeth for alloy. But, they have a negative angle. It is not a chop saw, the blade raises from a slot in the table.
I had an 'interesting' experience with a sliding chop saw, the blade stuck in the work (wood) and the rear alloy bracket fractured, allowing the motor/blade to leap towards me....
Cutting a boom sounds better done by hand, or with a proper alloy blade. My two centimes.

 

[oldmanofthehills]

The reason I am considering the chop saw is I expected that to give a cleaner, straighter cut than a hacksaw as long as it is set up and clamped properly.

Good tip about cutting around gradually if using a hacksaw. I might try that first cutting it a bit longer than needed first to see if I can get a straight enough cut.

I usually use Duralac when joining parts like this.

A fine bladed chop saw will be ok. Ours goes through hidden wood screws fairly smartly (Frued blades). Does not improve the blade if it happens often but thats with steel screws. I doubt your chop saw will notice much difference between very hard woods and aluminium. Sand any undue roughness

A bespoke hacksaw set up would cost more than a new blade which you may not need anyway