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I have a 10” Craftsman radial arm saw that serves most of my shop cutting needs. However, occasionally I need to cut through material that is just a bit thicker than what can fit under the blade. While in most cases rotating the material and making multiple cuts works, there are some cases where this isn’t possible (say, the material is only flat on one side). In these cases, could I mount a 12” blade on the saw to get a deeper cut depth? Obviously the existing blade guard wouldn’t cover the larger blade and a naked rotating blade would be extremely dangerous, but assuming I made a special guard specifically for the oversized blade, are there other considerations (safety or otherwise) that would prevent this arrangement from working?

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    TL;DR: No. Longer answer: No, do not do this.
    – jdv
    Sep 21 at 18:07
  • I'm glad you're coming around to the notion that this is a terrible idea. Want one more reason? The arbor size doesn't match. (10"=5/8" arbor; 12"=1" arbor.) Sep 22 at 3:34
  • I don't know much, but I have some pretty deep suspicions that, in a situation where the wood don't fit into the space where the saw can cut it, you're probably using the wrong tool for the job....
    – gnicko
    Sep 27 at 21:22
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The bigger blade will have more mass than the motor is designed to spin. This could cause issues for the motor, potentially burning it out. This is part of the reason that dado blade sets come in 8" size designed for use in a 10" table saw - you're adding multiple blades where only one normally goes, so by making the blade smaller, you're reducing mass, making it easier for the motor to spin.

If you're cutting a softwood like pine, you'd might be OK, but harder woods that the saw may struggle to cut in the first place would definitely be out.

Note: I say might be OK, because I don't know for certain. I would use extreme caution* if I were to attempt this.


*Note that "extreme caution" means I'd mention it to my wife and she would beat me senseless if I attempted it. ;)
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    TBH I would be hope that extreme caution here should be read as don't try it. Obviously the motor or gearing is at risk as you say, but let's say it does fit and seems to work fine I worry about the arbor. After a given time it seems inevitable a user will have become accustomed to using the larger blade without apparent harm to the saw ("It's never caused a problem before...." kind of thing) and therefore won't be a hyper-vigilant as they were early on.... the potential consequences if it breaks somewhere down the road don't bear thinking about <shudder>
    – Graphus
    Sep 21 at 18:04
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    Seeing as the wood I need to cut includes some really hard white oak, I’ll be putting this down as a bad idea not to be entertained again. Sep 21 at 19:07
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    It's not the mass - a 12" blade is cutting 20% further away from the rotation axis, so it experiences 20% more cutting torque for the same blade speed and depth of cut. This is where the extra load will come from.
    – J...
    Sep 22 at 17:50
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Obviously this is questionably safe, even if you can actually fit a 12" blade to your 10" radial-arm saw.

While in most cases rotating the material and making multiple cuts works, there are some cases where this isn’t possible (say, the material is only flat on one side).

There's a very simple and safe solution that should work for any situation you might face: complete the cut using a hand saw.

Any situation in which you can cut through a decent portion of the thickness, or better yet cut around an item one side at a time leaving just a central stub of wood, you're well positioned to finish the cut by hand as the kerf formed by a circular blade makes a very good channel for the panel saw to follow without error.

If you don't currently own a panel saw, modern ones are very inexpensive and because of the impulse-hardened teeth they stay sharp for a very long time so they're great value. Additionally such a saw has numerous other potential uses in a modern woodworking shop.

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  • Not sure why I didn’t think of finishing the cut with a hand saw. I’ve got a fairly decent variety of them, so finding the right one for the job should be simple enough. There are advantages to inheriting a whole bunch of tools from a master woodworker, even if not all of them have been maintained since he died forty or so years ago. Sep 21 at 19:03
  • Fascinating -- when I hear "panel saw" I think of the electric circular saw on a sliding carriage that the lumber yard (or a large enough woodshop) uses to cut sheet goods to order. I'd never heard it used to refer to a type of hand saw. Sep 22 at 17:15
  • @TimSparkles, understandable confusion on this point given two completely different saws regrettably share the exact same name. For those of us who use it to generically describe a hand saw that isn't a backsaw or frame saw we can console ourselves that they did have the name first :-) Unfortunately there's further confusion possible as in some naming conventions it refers to smaller/shorter hand saws (~20", but no larger), and in other still it refers to saws of this size but exclusively those filed for crosscut.
    – Graphus
    Sep 23 at 0:37
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Really no, it's a deadly proposition.

When these blades turn, the centrifugal force tries to tear them apart, so they have a maximum RPM rating which is usually written on the side. Larger diameter means lower RPM. However if you mount the larger blade on your saw, it will spin at the rpm of the motor designed for the smaller one, which means it will spin faster than intended. Best case, the carbide teeth hit the wood at a faster speed than intended, so they could get damaged. Worst case, the blade splits from centrifugal force, and since you removed the guard, you end up with a chunk of circular saw blade embedded in your face.

It would be a good excuse to get a bandsaw though.

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  • This is probably the most accurate and succinct answer to the Q
    – jdv
    Sep 22 at 21:57
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    Exceeding the maximum rated RPM seems to be a non-issue. 12" blades appear to be built for the same range of speeds, and sometimes slightly higher (e.g. 4000rpm when the saw might only go up to 3400-3500.... assuming it could even spin the blade up to that speed with the extra load, which seems unlikely.
    – Graphus
    Sep 23 at 0:55
  • BTW not having a guard fitted would be a bad day all round, but even with a factory-style guard fitted there's every likelihood it wouldn't provide sufficient protection in the event a saw blade came apart, just as the guards on grinders sometimes do not when a wheel explodes (even on solid old grinders where the guards aren't made of tinfoil).
    – Graphus
    Sep 23 at 0:56

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