Thread: Cutting aluminium sheet in rip saw mode

Originally Posted by rocketwiz

I see this done by people using proper table saws but not entirely sure if this is safe to do using a workcentre in rip mode rather than crosscut (as I can deal with larger pieces this way).
I plan to use a crosscut sled to minimise the amount of metal falling into the saw slot and hook up dust extraction to the saw itself but is the risk of metal chips finding their way into the saw simply too high?

I can't say about the metal finding it's way into the saw.
However, I do know that to do this safely the saw should be fitted with a negative raked toothed blade.
Woodworking blades have positively raked teeth and will pull the aluminium into the blade which can over stress the teeth and send TC tips flying around the shed. This has happened to me a few years ago and I was very lucky not to be injured.
If you decide to proceed with a woodwork blade you should use a high tooth count blade and feed the material slowly.
It also helps to rub the path you are going to cut and the saw blade with hard wax. As well as reducing friction it helps prevent the Al galling on the teeth tips.

BTW if you decide to buy a negative raked blade they are very useful for cutting plastics and other materials so you won't be wasting your money.

What thickness material are you cutting?

Thanks Bobl

I plan to cut up to 3mm sheet (5005 so fairly "soft") to make custom cases for electronics (I can never find the right size premade cases to fit). Bought an 80 tooth bosch multi material blade which should do the job (5 deg negative rake) before I realised I should probably get advice on metal fragments finding their way into the saw, seeing as the saw is upside down!

And, as you say, despite the cost of the blade I should be able to also cut acrylic sheet and melamine sheet (great for all the ikea mods I have planned!)

If you already have the circ saw and a dedicated blade to use, you could make a circ saw straight edge guide to guide the saw, and do the job with the saw right way up. Guide is a wide strip of flat MDF or similar with a similar strip with a dead straight edge glued and screwed to it, offset back from the edge of the first layer by more than the width of the circ saw base plate. First cut through with the saw trims the edge of the guide to give zero clearance between blade and guide, from then on mark your cut on the sheet, clamp the guide down to the sheet at the marks and run the saw down to cut. Can be made easily to any length provided you can get material that long. Lay the sheet on a sheet of poly foam or some of the $20 for 4 foam rubber intrlocking camping floor tiles as a sacrificial surface to accomodate blade penetratition and keep tip clear of floor or workbench.

Be cautious about using dusty, hot metal chips can set them on fire if they have ever been been exposed to wooddust, possibly after you have given up for the day and gone to bed. The chips tend to get dust to smolder without an obvious smoke trail, then the process builds up over time tile a fire breaks out. Also be very cautious about using a conventional vacuum cleaner as the exhaust air (and metal chips if there are any) pass over bare motor components to cool them and metal around those motors is not good either. The chips can cut/burn through the filters to get to the motor, so the motor is not guaranteed to be isolated from them.

Thanks for the advice - I'll do that for cutting main pieces and use the rip sled for smaller cuts and I'll be sure to clean up sawdust as much as possible before cutting metal which I normally do anyway - the stuff sure does get into every crevice of the triton.

My experience with generating many kg of ally swarf with a table saw and DC with plastic collection bags as follows.

The ally flakes coming direct off the saw blade landing on skin are indeed hot and razor sharp - full face shield and all round skin protection recommended. However the swarf is so thin that it only packs a small amount of heat, the volume of air is so high, and ally is such a good conductor of heat, that the ally swarf is rapidly cooled down in the air stream before it gets to the collection bags. if there had been any sort of heat problem the plastic bag would have melted well before the wood dust caught fire. I did eventually end up with holes in the plastic bags but not from heat - see below.

However, if a fire risk worries you, a temporary chip catcher made out of an empty metal container immediately after the saw and before the dust extractor will get around this problem. This is basically what metal dust collectors use.

The main reason I would recommend using a chip collector is because the swarf gets tangles up in filters and it is impossible to get out. If you have to cut a lot of ally it becomes even more necessary to use a catcher as the swirling swarf will eventually wear holes in plastic collection bags and filters and even PVC ducting.