Circular saw question

[yuyu]

I own a makita circular saw and it cuts very well and fast. was however wondering if theres there a reason why circular saws are not made with variable speed? It would be much more controllable i guess.

[Phil-in-MI]

Just a guess on my part:

Portable tools need lightweight motors. The type of motor traditionally used in circular saws is synchronized to the frequency of the prime AC power. The only way to change the speed is to change the frequency from 60 Hz to say 40 Hz. These are cheap, loud, and powerful motors for the weight. Great for the construction industry.

Modern batter power motors, modern motors that adjust speed by power voltage and other factors (like not all who purchase circular saw are in the construction trade or homeowner building a wooden deck,) maybe there might be room in the market place for a high end saw with variable speed control. Maybe even a circular saw that can be fitted into an accessory stand to convert it into a cheap table saw. Sell the accessory stand for $72.97 and the BORGs will sell lots of them. (Hey this is just a joke. Lighten up.)

I suspect the blade makers just might have some input into speed of the blades with respect to teeth design.

Phil

[Charlie M. 1958]

Hmmm... maybe that circular saw needs a VFD (variable frequency drive) like the ones used in industrial applications. Wow, this saw is starting to get pretty expensive now.

[beecrofter]

change blade parameters instead

[Joe Brophy]

VFD's are (albeit slowly) dropping in price, plus some of the newer designs are starting to show up on the used market.

I think the continuing development of economical, highly integrated, solid state high power devices in addition to be competitive innovations in vfd designs that use fewer components overall are the factors currently driving the prices lower. regards, Joe

If/when the Chinese/India industries move into this market it will have a huge effect in driving down prices, like in the MiG - tig- plasma cutter markets. already.

[Stephen M]

I question that assumption. I don't believe slower RPM would give you greater control. If you want the saw to cut slowly, push less. I would immagine that really slow rpm would give you kickback rather than control.

Drills need variable RPM because they have variable diameter cutters (various sized bits) as well as RPM-controlled self-feeding applications (driving screws and auger bits come to mind).

Circular saws are (for the most part) fixed diameter and manually "fed".

-Steve

[Leon]

No, circle saw blades cut best at specific speeds, typically the speed that your saw runs at. I wonder however what control you want to improve?

[Father Haskell]

Vary speed by varying the blade or the feed rate. Twice as many teeth = effectively twice the speed. Same with pushing the saw through the board half as fast.

[Leon]

A blade has an optimal cutting RPM. Feed in general rate does not change that.

[John]

You are describing an induction motor (synchronized to the frequency of the prime AC), which delivers less power for its weight. Table saws with belt drive typically use induction motors because weight is not an issue and there is less maintenance (no brushes to replace).

Most portable power tools use some variation of what is usually called a "universal" motor, which has brushes and a commutator. These motors have a much better power-to-weight ratio than the induction motor. The "universal" designation comes from the fact that many variations can be run on AC or DC (not a major concern today, but was in the past

- DAGS on "death dealing AC" for some history)

John

[Father Haskell]

Right. But it does give you a surface twice as smooth with half the resistance, as if you had used a blade with twice as many teeth.

[Chris Friesen]

You sure about that? I had always understood that tooth profiles were designed with a specific amount of "bite" in mind, and that blade speed and feed rate needed to be controlled together to get the best cut.

Thus, regular 10" blades are designed to work on standard saws at "regular" feed rates. If you want to feed the stock faster (for production use, say) then you need to use fewer teeth or a faster rotation in order to clear the chips faster. However, if you feed too slowly you can burn the stock due to the teeth spending too much time in contact with the wood.

Chris

[Leon]

Correct, however that does not = more control.

[Leon]

Blades are designed to cut best at a specific RPM. Best cutting does not always = smooth. Generally a slower feed rate produces a smoohter cut but may also introduce a burned cut.

Thus, regular 10" blades are designed to work on standard saws at "regular" feed rates. If you want to feed the stock faster (for production use, say) then you need to use fewer teeth or a faster rotation in order to clear the chips faster. However, if you feed too slowly you can burn the stock due to the teeth spending too much time in contact with the wood.

For optimum cutting with increased production you normally see a saw with a larger diameter blade with more teeth than one of smaller diameter.

[Mike Marlow]

Maybe variable speed would work - at least in some conditions, but I could see where stalls would be a huge problem for a saw. You can stall a variable speed drill motor pretty easily, and a saw suffers some rougher work than a drill does.

[bridgerfafc]

if you need more control, use a guide or push the saw slower. slowing the motor RPM won't help.

[yuyu]

slowing the rpm allow a slower feed without burning. just thought the variable speed might be a good thing to have in a circular saw.

[Father Haskell]

Control doesn't come from blade speed. Control comes with practice.

[Leon]

OK, perhaps you have missed the OP question. He wanted to know if he could use a speed control to slow the motor down for more control. The correct answer would be NO you cannot use a speed controller to slow down a circle saw motor.

Feeding slower could give more control if feed rate is the problem. He did not mention what kind of control problem he was having. There could be many control problems that feed rate would not correct. Perhaps he is looking for a soft start feature for better start up control. It is any ones guess.

[Greg Kimnach]

one of the best additions to my shop was the festool ts55eq. expensive, but worth it.

take a look at:

(non-hyphenated american)