Thread: Metal cutting blade for Kapex 120

Well with more research they were available in the States for a while, but were discontinued, most likely people were connecting the dust extraction while cutting steel into a full bag of saw dust.. i'd laugh, but its most likely true.

Anyhow, i noticed that you can get a Festool steel blade for the T75 plunge saw, but this is only 210mm high, compared to 260mm if i recall for the Kapex.

Same sized 30mm bore, i'm thinking the 50mm blade Difference should be ok, i can throw a piece of 112x19 DAR pine on top of the Kapex and Stand to protect it and stop any scratching on the aluminium.

anyone see any flaws before i waste money?

It's just for cutting 2mm thick steel SHS for my workshop benches.



https://adelaidetools.com.au/accesso...-0mm-bore.html

http://www.festool.com.au/epages/too...roducts/487271

This one is 240mm high, rang Festool to see if they did have a metal blade that would work, but of course they do not recommend it, can't see the safety difference between a TS75 saw and the blade in a Kapex.

The Kapex steel blade is available from Festool Aust for $176.

http://www.festool.com.au/epages/too...roducts/487271

Central Saws in Bendigo do one at 235 mm which they could rebore to 30 mm.

Dart MetalSonic Saw Blades Multi Material Cut | Central Saws

You will also need the spark arrestor for your vac if you also use it for wood.

that blade from Festool isn't for the Kapex, its for the AP85, but i think it would work, they have told me, not to do it

Festool no longer do a spark arrestor for the CT36, looks like they stoped making them.

i might ring around and see if any of my mates want too go half in a cut off saw, then i can leave it at there place once i'm done with it. will be cheaper than a blade

Those higher speed blades and cut off saws are horrible noisy things that spray hot metal dust/swarf all over the place. If you need to cut steel rod/tube etc I would shoot for a small bandsaw. It's slow but you can leave it cutting and go do something else while it's cutting

If it's just a one-off job, maybe it's worth finding a local fabrication shop to cut it all for you?

That is an option, but i don't trust anyone else cutting or measuring, yes i have control issues

And i agree with you bob, the bandsaws are better, but a bit more than i want to spend

I've found a 355mm cut off saw that's not that much more than the blade, so ill grab that instead, i can use for fitting out my shop and then i'll just give it to my father in law, then its out of the shop once i'm done with it, and if i need it i can borrow it.

that might be a win win solution

A tip I picked up recently for getting the lowest amount of heat buildup with cutoff saws is to go really hard, to the point of nearly stalling. I was shown this on a machining course for cutting 50*8mm HSS knife steel and there was no blueing at all, you could just about touch the cut surface straight off the blade.

I know some people get a bit precious with how they use tools and machinery, but I firmly believe in making the tools work like they were built for.

I've been down this path myself trying to find a metal cut off blade for my kapex all to no avail - I ended up having to do the same thing you mentioned and got a cut off saw!

Originally Posted by elanjacobs

A tip I picked up recently for getting the lowest amount of heat buildup with cutoff saws is to go really hard, to the point of nearly stalling. I was shown this on a machining course for cutting 50*8mm HSS knife steel and there was no blueing at all, you could just about touch the cut surface straight off the blade.

I agree that being too delicate around machinery can be counterproductive. Where I see this often is with chainsaws, these things are designed to operate on full throttle and it make little sense to feather the motor while cutting under normal conditions. If the chain saw motor maxes out at 13500 rpm there's tendency for newbies to want to retain the max revs but the optimum cutting speed is achieved somewhere above the max torque, nominally say 7000 rpm. The way this is achieved is to run full throttle and the get to optimum cutting speed by varying the pressure on the saw. This is how these saws are designed to operate.

However I'm not sure that electrical motors are built to operate near the stall point of the motor. The point at which an electrical motor stalls is where the rpm has dropped well off the max torque curve so its cutting speed will be less than optimum. It is also drawing way more current than it needs to so is operating very inefficiently and this will overheat the motor.

How long a machine can stand to operate like this is probably related to the build quality of the saw itself.

We had a bloke at the mens shed that insisted on doing this repeatedly on a Ryobi cut off saw that had been used without a problem for a couple of years. At one stage he was cutting 1/2" thick strap into full width cut pieces. A group of us watched from well back and wondered how long he could keep this up. After about a dozen cuts there was loud clunk and some smoke. When we opened the guts of the machine up we found that one of the brushes had disintegrated and torn the part of the commutator away from the rotor while other one had blown a 5c size hole in the other side of the commutator. Who knows - maybe this was going to happen anyway?

What I think you may be saying is these saws can be pushed harder than most users think but I don't think cutting speed will be anywhere near optimised near the stall point.

On my thin kerf cutting wheel mini table saw I have a lot more control than any cut off wheels in an angle grinder or cut off saw. Especially when cutting small pieces of steel I can feel there is actually sweet spot in the pressure needed for optimum cutting speed. iIt also seems to be the same pressure that produces the least wear on the wheel.

Originally Posted by BobL

However I'm not sure that electrical motors are built to operate near the stall point of the motor. The point at which an electrical motor stalls is where the rpm has dropped well off the max torque curve so its cutting speed will be less than optimum. It is also drawing way more current than it needs to so is operating very inefficiently and this will overheat the motor.

I thought electric motors had max torque at ~0 rpm and it dropped off from there?
Fair point about it not being healthy for it long-term

Originally Posted by elanjacobs

I thought electric motors had max torque at ~0 rpm and it dropped off from there?

Yes that's correct .

Instead of torque curve in my previous post I should have been referring to the a power curve since that is what more closely relates to work done.
An electrical motor does have max torque at zero RPM but as it's not turning its not doing any work.
At max RPM it las little torque but enough ROM to do useful work.
As a load is applied the RPMs drop - if the load is high enough the RPMs drop to nothing where no work is done.

The HP and efficiency (HP/electrical power input) versus RPM curve for an electric motor looks something like this.
It's nominally a 1490 RPM motor that reaches its rated 1.3HP output when under load it drops to about 1425 RPM.
This RPM is also close to its maximum efficiency.
If pushed beyond this RPM, the efficiency drops and even though the torque increases the RPMs drop even faster so the HP will start to drop off.
A little beyond this point the efficiency drops rapidly, RPMs really drop off (stall) and repeated often enough will harm the motor.

1kWDPmotorHPVRPM.jpg

I have measure lots of these curves on motors. Given my limited data collection method is difficult to catch all the data near the stall point but I have a few that kick right over and less than a second later the motor stalls. As you can imagine I don't want to be doing this too often

I Have a metal cutting blade for the kapex ill have a look at what brand it is and post a picture

Cheers

Bryan

Here it is

Cheers
Bryan the blade is 254mm and still cuts all the way through

Cheers

Bryan

Originally Posted by Bryan1982

Here it is

Cheers
Bryan the blade is 254mm and still cuts all the way through

Cheers

Bryan

Cheers Bryan,

That was exactly what i was after, i was going down to pick up a cutoff saw today, as we were rained out yesterday.

But i'll just order this as even though i can get a cut off saw for around the same price, i can guarantee the angles won't be as accurate as the Kapex.

looks like my father in law misses out on a cut off saw