New Machine Build- Radial arm chop saw - bad idea?

[roombacurious]

I like making my own tools and machines and I'm thinking to make a saw to cut sheet steel as well as thicker material like tubing, rods and similar.
The idea is to combine the setup of a radial tile cutter (like this

http://www.amazon.co.uk/Einhell-TPR2002-Radial-Tile-Cutter/dp/B000X8I5RO

http://www.amazon.co.uk/Einhell-TPR2002-Radial-Tile-Cutter/dp/B000X8I5RO

) with a beefy motor and a chop saw (dry) blade.
The material will be solidly clamped down and the saw will slice through it. The benefit is that you combine the speed and power of a chop saw with the increased capacity of a radial arm saw, plus you can make straight cuts with minimal effort.

Can anyone think of reasons why this could be a stupid or even dangerous idea? I'm worried I'm missing something here as I don't see any such saws on the market...

[HuFlungDung]

I don't know about cutting steel of any significant thickness.

The potential danger, as I see it, is that a radial arm saw wants to 'climb mill' which is good, so far as the blade goes, but is tough on the machine if it is anything less than super rigid (which a radial arm saw is not).

The other factor is that the operator must then control the tendency of the saw to climb (towards himself) and at the same time, to permit it to do exactly that.

Perhaps you could alleviate this problem by ensuring that you bury the blade deep into the cut, almost to the arbor. This puts the down cutting force more nearly perpendicular to the table.

Clamping the work is a good idea, almost an imperative. Some kind of a feed mechanism to control the progress of the saw would be nice, even an acme screw with a some kind of inexpensive servo drive (like a mill feed).

[Geof]

I think you are considering a very high risk idea; especially with a 'beefy' motor.

Hu mentions the risk of the saw trying to climb the work towards you, but I think there is an added risk.

Have you used a big radial arm saw on wood and had it climb toward you and stall the motor? Things happen very fast but generally the motor does stall and the breaker pops.

While this is happening the blade is safely buried in a block of wood. The risk that I perceive with metal is that the blade will not bury in something soft and stall but will start fragmenting teeth off like shrapnel.

Maybe I am being too cautious but I am not game to do the experiment and find out.

[WeCheat]

Welcome to the site!! I had a setup like you are talking about a few years back. It used a 8in metal saw (looked like a 7 ½ circular saw) but it has a clutch setup in it so if the blade gets stuck it wont kick back. It work ok but I found it to be a pain because it was not as versatile as I thought it would be. I found my self taking the saw off a lot and just using a ripping fence to cut plate steal (mostly ¼ to 3/8 thick) and tubing. If I had to cut a lot of tubing/angel iron I used a jig to do that. If you decide to it make be sure your saw has some type of kick back protection. The two poster above know there stuff and bring a lot of experience to the site, if done right it will work if done wrong it will bite you bad.
Greg

[roombacurious]

Thanks for all your posts, certainly food for thought here...

What I failed to clarify is that I'm not planning to use a toothed blade but an abrasive 12" one. I was also thinking to use an induction motor (around 2,900 rpm in the UK) though not quite sure on the HP yet.

I'm sure an abrasive blade can stall and explode if pushed and I was planning to make it fully shielded to avoid the shrapnel scenario. Also the saw would travel from left to right rather than being pulled towards the operator which I find a really bad idea.

I guess an easy way to make this setup safer would be to use a smaller motor, around 1 HP or so. On the other hand this will probably make cuts painfully slow and increase the likelihood of stalling.

It's starting to make more sense now why there aren't many such saws around!

[Geof]

Originally Posted by roombacurious ....What I failed to clarify is that I'm not planning to use a toothed blade but an abrasive 12" one..... ... Also the saw would travel from left to right rather than being pulled towards the operator which I find a really bad idea....

That does change the picture.

Unless you have extremely weird shaped arms you must be planning on some sort of feed drive to advance the blade.

Figure out some way of reliably clamping the stock down and feed the blade into it so it is up-cutting.

[Oldmanandhistoy]

Hi,

Interesting idea but scares me to death !

Having had many years experience with a radial arm saw (timber only) I would have to say there is no way I would use one on steel without power feed. Having said that I would have thought it would be a PITA (time wise) to do manually?

Please keep us posted with your progress.

Good luck,
John

Geof

Would it be absolutely necessary to up-cut with an abrasive wheel; if it is I can't get my head around why? The way I see it is if you up-cut and clamp from above you are basically just turning all the forces upside down and still down cutting (all be it upside down) but now into clamps which will not be as ridged as the table. Surly the largest force on the material would be best sent through the table rather than into clamps?

Originally Posted by Geof Figure out some way of reliably clamping the stock down and feed the blade into it so it is up-cutting.

IMHO this machine would be better using down cutting (conventional method on a radial arm) WITH a power feed and a clamping method.

Also with a power feed the danger of snatching should be eliminated using a toothed saw.

Just my opinion please feel free to

[Andre' B]

Have you looked at the Morse metal devil saws?
http://www.metaldevil.com/evolution.html
http://www.mkmorse.com/

YouTube - SIERRA CIRCULAR - METAL DEVIL

YouTube - SIERRA CIRCULAR - METAL DEVIL

I would think if you put one in a heavy duty panel saw you would have what you are looking for. I would think a horizontal panel saw may be better, I do not think it would take much to build one.
http://sawsystems.net/
I also think it may be a good idea to let the saw float so that its shoe plate rides on the material being cut.

[Geof]

Originally Posted by Oldmanandhistoy ....Interesting idea but scares me to deaf ! Geof Would it be absolutely necessary to up-cut with an abrasive wheel; if it is I can't get my head around why? The way I see it is if you up-cut and clamp from above you are basically just turning all the forces upside down and still down cutting (all be it upside down) but now into clamps which will not be as ridged as the table. Surly the largest force on the material would be best sent through the table rather than into clamps?...

You are correct, without good ear protection it does scare you to deaf.

The reason I suggest upcut is simply that I think it will be easier to make sturdy clamps than it will be to make a zero backlash feed mechanism. Any backlash here will let the blade climb into the cut and either stall the motor or break the blade.

[HuFlungDung]

With regard to using toothed blades in steel, I read somewhere that expected blade life in 1/4" steel on these dry metal cutters was 260 inches of cut. To me, that is expensive cutting.

The chips from steel cutting with a high speed saw are definitely something to be scared of. They'll be all over the place in a 10 foot radius.

And to grind kerf with abrasive cutoff wheels....well, that is just disgusting to any machinist I hate the noise and the dust cloud doesn't seem to make it any more palatable

[cam1]

The cold cut saws and blades were primarily to cut light hollow ferrous and non-ferrous shapes (EMT and angles) on the construction site. They are an alternative to abrasive saws which are a fire hazard, and create nsaty burrs. The cold saws cur almost burr free. If you let the saw blade do the cutting they will last a long long time on the thin non-ferrous materials.

regards

[Oldmanandhistoy]

Originally Posted by Oldmanandhistoy IMHO this machine would be better using down cutting (conventional method on a radial arm) WITH a power feed and a clamping method. Also with a power feed the danger of snatching should be eliminated using a toothed saw. Just my opinion please feel free to

Deaf

I withdraw my above opinion as I had not taking into account the angle the blade would engage the material and agree that up cutting is a better option.
But I still think if the machine was rigid enough and the backlash was minimal you would get away with it.

John