Ampacity of 18 gauge wire

For four feet that should be OK. (I'm not at all an electrician.) Heck run a double strand if you are worried about it.

George H.

I have to assume when you saw 4ft that when we do the calculation we need to use 8 ft, because the current flows through both the hot and neutral wire. 18 gauge copper wire has 6.385 ohms of resistance per 1000 ft. If you divide 8ft by 1000ft you get 125. So if we divide 6.385 ohms by 125 we get 0.05108 ohms. Voltage drop is current times ohms. 10amps x 0.051 = 0.51 volts. Then from your 120Vac line the ft cord will drop to 119.49 Volts. I don't consider that a problem, but note, the manufacturer did! What did they use 16 guage? If you consider a 50ft 18 gauge extension cord, that would cause a

6.385v drop leaving you 113.15v, (you can subtract 0.51 for you 4ft cord) starting to have some concern, but it will work unless you put a heavy load on the saw. If you put a very heavy load on the saw and draw 20 amps, now you are down to 106.2v. Now start thinking about your home, is there 50 ft of 14gauge wire from the breaker box to the outlet. That add another 0.25 ohms in the circuit, that will add another 2.5v drop at 10 amps and 5v drop if you draw 20 amps. Adding all those together and using your 10 amp number, 0.051 + 0.6385 + 0.25 = 0.9395 ohms, you're losing about 1v per amp. I hope that gives you some insight.

In this situation, it's mostly a matter of heat. Smaller wires get hotter. And wires in a cable with insulation around them get hotter than wires in open air.

In your case, the saw will hardly ever be drawing its full rated load of

10A = that will happen only when you're really pushing it through thick wood. Also, its use will be intermittent, giving the wire the chance to cool between cuts.

So, 18ga is too small for your saw, but you'll probably be OK.

I wouldn't if I were doing it. But like a lot of things it all depends on circumstances. (the context)

If you are regularly pulling 10 amps that wire will be getting warm. Going to rip some longish wood, for instance? or jam/twist the blade?

It also depends on wire insulation and how resistant it is to melting or cold flowing if it is pinched while warm.

Copper wire resistance goes up with heat too.

You can never be too safe, and it ain't a lot of money.... You will probably get away with it, but is that a design goal?

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This is a false economy. You can get a 6 ft 16 gauge extension cord, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card . My opinion is that for this small amount of money, it is not worth riski ng your life by being a cheapskate.

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ed for 13A, from Lowe's for US$1.78 plus tax and interest on your credit ca rd. My opinion is that for this small amount of money, it is not worth ris king your life by being a cheapskate.

Not being a cheapskate. Just frugal.

Using 18 gauge wire on a circular saw is not recommended. It should be on a 15 amp circuit at least. That would mean 14 gauge wire if hard wired. If you are using an extension cord I would not go smaller than 16 ga.

Then it isn't a matter of design, but one of philosophy.

There is satisfaction in knowing you did the best job you could. The way I use my woodworking tools, I don't skimp on how they are maintained. I've built stacking wood cases for the hand operated saws, sanders, grinders, etc.. A lot of effort up-front, but it is nice to have the wrenches and change-out parts in one place with the tool, and there's less chance of damage.

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rated for 13A, from Lowe's for US$1.78 plus tax and interest on your credit card. My opinion is that for this small amount of money, it is not worth risking your life by being a cheapskate.

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My microwave went out. I salvaged the cord. It was at least 14 gauge.

Andy

Are you going to make an extension cord out of it?

Just wondering if using too small a fuse can choke the current? Even though they're only an inch long? Say I am running my portable welder which draws 12A and is fitted with a

13A fuse, via an extension lead which is fitted with only a 10A fuse, will the smaller fuse choke the current the welder is trying to draw? IIRC, the smaller fuse would probably not blow for many minutes, so one could be totally unaware that it's unable to supply enough current for the welder and giving rise to poor quality welds.

Fuses have relatively low resistance so if the amp and volt rating are correct the small amount of resistance a fuse adds will be negligible. A long wire run, with too small a gauge would probably have a greater effect.

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ular saw)

, rated for 13A, from Lowe's for US$1.78 plus tax and interest on your cred it card. My opinion is that for this small amount of money, it is not wort h risking your life by being a cheapskate.

16 ga.

Yes, I did.