How to slow down RPM of miter saw?

default <default@defaulter.net> wrote: 

> Yes it will reduce the "power" since power is RPM versus torque.  You 
> will reduce the RPM to something less than half with less power (all 
> things being equal) but the motor will still behave like an AC/DC 
> motor and draw more current and produce more torque as the load tries 
> to slow it down 

Thanks. Was wondering about that, too. 

If the motor stalls, it wont cut very well, either. And then there is
the fact that fuses/breakers tend to blow... 

Gearing between the motor and the blade makes no difference since the 
specifications are for the motor. If the troll wants people to be
specific, it should at least pay attention to the given information... 


-- 
Jasen Betts <jasen xnet.co.nz> wrote in news:m5ddup$egh$1 gonzo.reversiblemaps.ath.cx:

> Path: eternal-september.org!mx02.eternal-september.org!feeder.eternal-september.org!news.glorb.com!news.astraweb.com!border5.newsrouter.astraweb.com!not-for-mail
> From: Jasen Betts <jasen xnet.co.nz>
> Newsgroups: sci.electronics.basics
> Subject: Re: How to slow down RPM of miter saw?
> Date: 29 Nov 2014 21:31:05 GMT
> Organization: JJ's own news server
> Message-ID: <m5ddup$egh$1 gonzo.reversiblemaps.ath.cx>
> References: <m5d282$si5$1 dont-email.me> <5e9k7a1rui0p9a3emnmctbbk98fpamt6dq 4ax.com>
> X-Face: ?)Aw4rXwN5u0~$nqKj`xPz>xHCwgi^q+^?Ri*+R(&uv2=E1Q0Zk(>h!~o2ID 6{uf8s;a +M[5[U[QT7xFN%^gR"=tuJw%TXXR'Fp~W;(T"1(739R%m0Yyyv*gkGoPA.$b,D.w:z+<'"=-lVT?6 {T?=R^:W5g|E2#EhjKCa+nt":4b}dU7GYB*HBxn&Td$ f%.kl^:7X8rQWd[NTc"P"u6nkisze/Q;8 "9Z{peQF,w)7UjV$c|RO/mQW/NMgWfr5*$-Z%u46"/00mx-,\R'fLPe.)^
> User-Agent: slrn/pre1.0.0-18 (Linux)
> Lines: 41
> NNTP-Posting-Host: 515d4d94.news.astraweb.com
> X-Trace: DXC=e8j6PfB8`m]eIcSKiG^o_UL?0kYOcDh Z8S]EBhDhDYWI3M1Q7=KWaTl9B_G1R=S=W]YVTRZ:Ha`WT2B9638eA]V]c1WZ_ml=IXB^6Pi<mFYA[
> Xref: mx02.eternal-september.org sci.electronics.basics:44164
> 
> On 2014-11-29, default <default defaulter.net> wrote:
>> On Sat, 29 Nov 2014 18:11:14 +0000 (UTC), John Doe
>><always.look message.header> wrote:
>>
>>>The motor runs on standard USA 120 V 60 Hz, 14 A, at 5500 RPM. 
>>>
>>>What's the easiest way to slow down the RPM? 
>>>
>>>What about simply adding a diode in series on the power cord? 
>>>
>>>Any advice, references, and links would be appreciated. 
>>>
>>>Thanks.
>>
>> If the rotor is AC/DC (most inexpensive power tools like drills,
>> circular saws, and miter saws) a diode is an excellent choice to just
>> drop some voltage and slow it down.
>>
>> Since the thing can probably pull a few amps you want high current
>> diode; 20+ amps would be my guess and whatever line voltage you run
>> at.
> 
> starting (stall) current could be 100A or more.
> 
>> AC/DC motors are easily distinguished because they make lots more
>> noise than induction motors.  AND you are saying that you have 5500
>> RPM?  That is too fast to be an induction motor on 50 or 60 cycles.
> 
> Pretty-much all types of circular saws have some sort of gearchain or 
> belt drive between the motor and the blade, the blade rarely runs at
> the same speed as the motor. One reason for this is to offset the bulk
> of the motor from the plane of the blade axle, allowing deeper cuts
> with a given size of blade. So, blade speed is not indicative of motor
> speed. 
> 
> 
> 
> 
> -- 
> umop apisdn
> 
> 
> 

On 11/29/2014 3:02 PM, John Doe wrote:
> Have you ever even used a miter saw?
>
> More often the design of a common inexpensive tool takes into
> consideration the cheapness of its parts. A more expensive tool might
> run at a faster or slower RPM and be designed to do the same thing, only
> better. Safety doesn't necessarily have anything to do with lowering the
> RPM. If you want to go on a crusade for miter saw safety, you should
> talk about wearing eye protection and keeping your hands away from the
> cut. In fact, I am using it for aluminum. Obviously that's not what it's
> designed for but that happens to be what many of us, including
> professional metalworkers, use miter saws for.
>
> Miter saws are not for people who are overly concerned about safety.
> They are inherently hazardous. It also isn't for people who have no
> basis for their understanding of safety. I've come across people who
> don't really know what they're talking about that say you should use
> gloves "in the name of safety", but that actually increases the risk.
>
> I'm trying to solve a problem that has to do with a potential hazard.
> And it requires a lower RPM.
>
> I think there is a safety consideration with lowering the RPM, but the
> reply author probably doesn't even know what that might be. If the idea
> were to increase the RPM, then there would be an obvious possible
> concern for safety that any Joe might recognize.
>
> I just bought a cheap abrasive cutoff disc made by a well-known
> manufacturer that's supposed to cut metal. The thing doesn't cut
> aluminum and therefore trying to do so is a safety hazard.
>
> Using a miter saw is not for the meek.
>
>
> Tom Biasi <tombiasi@optonline.net> wrote in news:Lxoew.792810$1s.710374@fx05.iad:
>
>> On 11/29/2014 1:11 PM, John Doe wrote:
>>> The motor runs on standard USA 120 V 60 Hz, 14 A, at 5500 RPM.
>>>
>>> What's the easiest way to slow down the RPM?
>>>
>>> What about simply adding a diode in series on the power cord?
>>>
>>> Any advice, references, and links would be appreciated.
>>>
>>> Thanks.
>>>
>> The saw is designed to run at a certain RPM and blade size. Changing
>> either is not recommended.
>> I know I didn't answer your question. My response was in the name of safety.
>
I won't even begin to address such a nasty rant against someone who only 
pointed out some basic safety concerns.
Yes I have used a miter saw. They are not inherently dangerous if the 
safety instructions are followed.

In article <m5d282$si5$1@dont-email.me>, always.look@message.header 
says...
> 
> The motor runs on standard USA 120 V 60 Hz, 14 A, at 5500 RPM. 
> 
> What's the easiest way to slow down the RPM? 
> 
> What about simply adding a diode in series on the power cord? 
> 
> Any advice, references, and links would be appreciated. 
> 
> Thanks.

 Only if it's a universal motor, and you want to do it at the 
motor lead connections, in case you have something else in the saw
that expects AC.

 14 amps isn't a small amount so the selected diode will be a stud
type of some heat mountable type.

Jamie

In article <m5dg4b$etn$1@dont-email.me>, always.look@message.header 
says...
> 
> I don't know about New Zealand, but in United States English the 
> expression "slow down" does not mean "stop". And in fact I am not asking 
> for a specific RPM, therefore that specification is not needed, as the 
> helpful replies already indicate. 
> 
> As for "voiding the warranty". I can void a warranty before even touching 
> a product...


 You could always use a variac.

Jamie

"Maynard A. Philbrook Jr." <jamie_ka1lpa@charter.net> wrote: 

> always.look@message.header says... 

>> What about simply adding a diode in series on the power cord? 
> 
> Only if it's a universal motor, and you want to do it at the motor
> lead connections, in case you have something else in the saw that
> expects AC. 

I will check that. 





-- 

Thanks to the replies. 

 John Doe wrote:

> The motor runs on standard USA 120 V 60 Hz, 14 A, at 5500 RPM. 
> 
> What's the easiest way to slow down the RPM? 


 ** Does it really pull 14 amps ?

 A standard triac light dimmer will do the trick -  but it must use a 16amp triac at least.  

Or a nice, big Variac. 



> What about simply adding a diode in series on the power cord? 


 ** Crude and will only drops the speed a small amount.



...  Phil 

DROK AC 110V 3000W SCR

<http://www.amazon.com/DROK-Electronic-controller-Governor-
Thermostat/dp/B00BXUCWQG/ref=cm_cr_pr_product_top>

Will that work? Will it increase the current when the load increases? 

One comment said that it chops the AC signal amplitude and that it's
hard on motors. Is that a concern about increased current when the load
is too much? 

If it works, 20 bucks is very attractive. 

-- 






> The motor runs on standard USA 120 V 60 Hz, 14 A, at 5500 RPM. 
> 
> What's the easiest way to slow down the RPM? 

<http://www.amazon.com/DROK-Electronic-controller-Governor-Thermostat/dp/B00BXUCWQG/ref=cm_cr_pr_product_top>

I jumped through here to tell you, it is improper to reduce the RPM in this=
 case. what you need is the proper blade. In most cases a bandsaw will do w=
hat you eant better, again, with the right blade. however sionce you posted=
 it I am going to assume you have a eason to use the chop saw, which is wha=
t some of us call lower end miter saws. (or maybe you are cuting a compound=
 angle, whatever reason)

A miter saw is NOT a lathe where you calculate cutting speed in SFM. the fi=
rst thing you need is a many toothed carbide tipped blade. What's more, whe=
n you cut, you FEED it, donot babyu it or the aluminum will clog up the bla=
de teeth.=20

Keep the RPM up and the feed slow, very slow. If you need to cut really fas=
t, there are blades made for that.=20

With a half decent carbide tipped blade I can cut muffler pipes and shit, b=
umpers, all kinds of things. The problem is that it is so easy to overload =
the blade and fuck it all up. AND LOWERING THE RPMS WIL NOT REDUCE THE CHAN=
CES OF THIS.=20

And the LAST thing you want is for that blade to stall in aluminum. and the=
re is almost no way without a servo circuit, to make sure it does not stall=
 under an underpower condition, which you must create to lower the RPMs. If=
 youy REALLY have to lower the RPMs, do it with gears. That is my advice. L=
owering the motor RPMs electronically is a bad move, a wrong move, and will=
 make a mess.=20

Of course some will try it anyway, if you do, just make sure you are ready =
for that torque and shit when the thing stalls.