I have no problem cutting aluminum. The problem I have is better discussed in an appropriate USENET group. I would suggest that you cruise on over to the metalworking group to discuss your theories. It's a big group with lots of participants. But hardly anyone on USENET appreciates unformatted Google Groups posts... jurb6006@gmail.com wrote in news:e8b36fa1-96a4-43f9-b69c-203513237d14@googlegroups.com:> 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 what 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 what 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 first thing you need is a many toothed carbide tipped blade. What's more, when you cut, you FEED it, donot babyu it or the aluminum will clog up the blade teeth. > > Keep the RPM up and the feed slow, very slow. If you need to cut really fast, there are blades made for that. > > With a half decent carbide tipped blade I can cut muffler pipes and shit, bumpers, 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 CHANCES OF THIS. > > And the LAST thing you want is for that blade to stall in aluminum. and there 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. Lowering the motor RPMs electronically is a bad move, a wrong move, and will make a mess. > > 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. >
How to slow down RPM of miter saw?
Started by ●November 29, 2014
Reply by ●November 30, 20142014-11-30
Reply by ●November 30, 20142014-11-30
> assume you have a reason to use the chop saw, which is what some of us > call lower end miter sawsI call it a "wood whacker".
Reply by ●November 30, 20142014-11-30
John Doe wrote:> 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?** Possibly it might do.> Will it increase the current when the load increases?** Doing that requires back emf sensing as found on SCR speed controllers for drills, food mixers etc. These are very good at maintaining full torque down to a few hundred rpms but are not made for large motors. The above unit appears to be triac based (since it can de used as a dimmer) as are nearly all speed controls fitted into mains powers hand drills. The sort speed control YOU are asking for is specialised, designed expressly for high powered AC motors (like routers) with back emf sensing and includes a soft start feature - like the one on this page: http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/speed_control.html The 20Amp model looks worth a try. .... Phil> > 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?
Reply by ●December 1, 20142014-12-01
On 29 Nov 2014 21:31:05 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:>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.One hopes that it wouldn't be expected to run stalled for very long, and the inrush/peak current of diodes is much higher than steady state - since we see the same thing on linear power supplies with large electrolytic capacitors. 1N4XXX series of diodes are good for 1 amp and can carry a surge current of 30 amps.> >> 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.You might be correct with table saws where they use an induction motor and keep a small sheave at the blade for that reason, but AC/DC motors used in bench top table saws, hand held circular saws, miter chop saws, etc. are direct drive (blade goes on the motor shaft - and frequently the field and windings are offset a bit so the motor shaft is not concentric with the housing, but of course, still concentric with the field iron)
Reply by ●December 1, 20142014-12-01
On the subject of safety... Here you have a major retailer Lowe's hardware showing a guy wearing gloves while using a miter saw... http://www.lowes.com/ Hover your pointer over "Ideas and How-tos". In fact, as the vast majority of professionals will tell you, wearing gloves while using such a power tool is a bad thing. Stuff unnecessarily amputated... https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=200651750 At approximately 11:30 a.m. on July 8, 2010, Employee #1 was operating a CTD model M25R chop saw (powered miter box type saw) and cutting aluminum I beams. She was wearing gloves when the saw blade caught the gloves and pulled her fingers into the blade. The blade amputated her left thumb, and index, middle and ring finger at the distal interphalangeal joint. Additionally, the company had rules about not wearing gloves while operating the chop saw. After the accident, she was transported to a medical center where she received treatment and was hospitalized.
Reply by ●December 1, 20142014-12-01
On Sat, 29 Nov 2014 19:18:57 +0000, Baron <baron@linuxmaniac.net> wrote:>John Doe prodded the keyboard > >> 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. > >This would depend upon the type of motor ! If we assume a universal >motor then a thyristor or triac phase controler that can handle the >maximum current plus 100% could be used. An induction motor would >need a variac (variable transformer) or one of the electronic devices >used specifically for this purpose. But I would doubt that what you >have uses an induction motor.Every power miter saw I have seen in the last 25 years had a universal motor. They also have a circuit that dynamically brakes the motor when the trigger is released. I wonder if that circuit would have any negative effect on certain speed controllers. Probably not. In any case universal motors have poor speed regulation. And lowering the voltage or current significantly my make the speed regulation really bad. As I recall from reading about it this is partly because the brushes are located in the best place for the least amount of sparking and changing the voltage or current will change this location. Eric
Reply by ●December 1, 20142014-12-01
etpm@whidbey.com wrote:> Baron <baron@linuxmaniac.net> wrote: >> John Doe prodded the keyboard >> >>> 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.>> This would depend upon the type of motor ! If we assume a universal >> motor then a thyristor or triac phase controler that can handle the >> maximum current plus 100% could be used. An induction motor would >> need a variac (variable transformer) or one of the electronic devices >> used specifically for this purpose. But I would doubt that what you >> have uses an induction motor.> Every power miter saw I have seen in the last 25 years had a universal > motor. They also have a circuit that dynamically brakes the motor when > the trigger is released. I wonder if that circuit would have any > negative effect on certain speed controllers. Probably not. In any > case universal motors have poor speed regulation. And lowering the > voltage or current significantly my make the speed regulation really > bad. As I recall from reading about it this is partly because the > brushes are located in the best place for the least amount of sparking > and changing the voltage or current will change this location.I'm probably going to try the diode method first. There are some ultracheap 1000 V 10 amp diodes available. I might put some of them in parallel. I doubt that has the same problem. And then it can be used for any other appropriate brushed universal motor device.
Reply by ●December 1, 20142014-12-01
John Doe prodded the keyboard> etpm@whidbey.com wrote: > >> Baron <baron@linuxmaniac.net> wrote: >>> John Doe prodded the keyboard >>> >>>> 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. > >>> This would depend upon the type of motor ! If we assume a >>> universal motor then a thyristor or triac phase controler that can >>> handle the >>> maximum current plus 100% could be used. An induction motor would >>> need a variac (variable transformer) or one of the electronic >>> devices >>> used specifically for this purpose. But I would doubt that what >>> you have uses an induction motor. > >> Every power miter saw I have seen in the last 25 years had a >> universal motor. They also have a circuit that dynamically brakes >> the motor when the trigger is released. I wonder if that circuit >> would have any negative effect on certain speed controllers. >> Probably not. In any case universal motors have poor speed >> regulation. And lowering the voltage or current significantly my >> make the speed regulation really bad. As I recall from reading >> about it this is partly because the brushes are located in the best >> place for the least amount of sparking and changing the voltage or >> current will change this location. > > I'm probably going to try the diode method first. There are some > ultracheap 1000 V 10 amp diodes available. I might put some of them > in parallel. I doubt that has the same problem. And then it can be > used for any other appropriate brushed universal motor device.I suspect that it will not achive the desired effect ! Recall that a universal motor will happily run on ac or dc, the motor brush gear simply chops up a dc supply to create an alternating field. -- Best Regards: Baron.
Reply by ●December 1, 20142014-12-01
Baron <baron@linuxmaniac.net> wrote in news:m5ik9q$rf5$1@dont-email.me:> John Doe prodded the keyboard > >> etpm@whidbey.com wrote: >> >>> Baron <baron@linuxmaniac.net> wrote: >>>> John Doe prodded the keyboard >>>> >>>>> 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. >> >>>> This would depend upon the type of motor ! If we assume a >>>> universal motor then a thyristor or triac phase controler that can >>>> handle the maximum current plus 100% could be used. An induction >>>> motor would need a variac (variable transformer) or one of the >>>> electronic devices used specifically for this purpose. But I would >>>> doubt that what you have uses an induction motor. >> >>> Every power miter saw I have seen in the last 25 years had a >>> universal motor. They also have a circuit that dynamically brakes >>> the motor when the trigger is released. I wonder if that circuit >>> would have any negative effect on certain speed controllers. >>> Probably not. In any case universal motors have poor speed >>> regulation. And lowering the voltage or current significantly my >>> make the speed regulation really bad. As I recall from reading about >>> it this is partly because the brushes are located in the best place >>> for the least amount of sparking and changing the voltage or current >>> will change this location. >> >> I'm probably going to try the diode method first. There are some >> ultracheap 1000 V 10 amp diodes available. I might put some of them >> in parallel. I doubt that has the same problem. And then it can be >> used for any other appropriate brushed universal motor device. > > I suspect that it will not achive the desired effect !What effect do you suspect it will have?! --> Recall that a universal motor will happily run on ac or dc, the motor > brush gear simply chops up a dc supply to create an alternating field. >
Reply by ●December 1, 20142014-12-01
John Doe prodded the keyboard>> I suspect that it will not achive the desired effect ! > > What effect do you suspect it will have?!Never having actually placed a diode in series with a universal motor, not a lot. I belive that the motor current will increase to try and compensate for the drop in speed due to the load. The motor will try to maintain its speed. It is however an interesting experiment and I would be interested in your findings. -- Best Regards: Baron.
