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Posted: Tue Jan 27, 2009 1:11 pm
by reible
Let me add to what Chuck has said, if you go to page 19 of the current PTWFE and look at table 2-1 it lists under Heavy Ripping of Hardwood that the saw be set to "O" (2800 RPM). So this should be normal operations for shopsmith owners, well at least those that believe what shopsmith has to say about it anyway.
If you don't own the book you really need to. If you own the book you need to open it and do some reading. Gee how many times have I said that???
Ed
charlese wrote:Bob- I'll bet you get some burning of sawn edges when using speed R. I've found that on my machine speed O is the best for both ripping and crosscutting. Your machine may not be exactly the same as mine because of belt and adjustments.
At this speed I think it is important to use a rip blade (fewer teeth) for ripping and a crosscut blade (a whole bunch of teeth) for cross cutting.
Using this speed, I've only had burns on a rip when the board gets hung up a bit and slows or stops during cutting. Don't ever have a burn on cross cuts.
Posted: Tue Jan 27, 2009 2:13 pm
by 8iowa
As has been correctly stated above, using a thin kerf 24T rip blade will greatly enhance your ability to rip heavy stock.
For heavy ripping operations I often go as low as "M" or "N" on the speed dial. By reducing the feed rate you will be operating at optimum torque and cutting HP. It may take 30 seconds to rip a board, as opposed to 15 seconds on a more powerful saw, but you can accomplish the task just as well.
Table saw manufacturers certainly consider any saw that will operate on a 120V 15 amp circuit as "underpowered". The ability of the Shopsmith to cut at lower speeds/higher torque sets the Shopsmith apart from the rest of the single speed table saws in this class.
Yeah...........we've all heard how the Shopsmith's weakest mode is in table saw, and the tilting table aspect is constantly thrown in our face. However, as I have pointed out, there are some advantages to the Shopsmith as a saw.
As a footnote: since rdewinter mentioned ripping thick stock, I'll mention that I often freehand rip a straight line on 8 foot rough cut boards that do not have a true edge. I do it on the bandsaw using a wide blade, and supporting the board on the infeed and outfeed sides with ball bearing roller stands. I'm surprised at how straight a cut I can make, certainly good enough to place against the fence in order to rip the other side in conventional saw mode fashion.
Posted: Tue Jan 27, 2009 2:49 pm
by Ed in Tampa
8iowa wrote:A/C induction motors are rated a certain HP at a maximum continuous temperature rise. This is done in a dynomometer lab with thermocouples in a lot of places on the motor. This does not result in haphazard ratings from one manufacturer to the next, because the HP, frame size, and temperature rise (55 degrees C) of induction motors is standardized by the National Electrical Manufacturer's Association (NEMA). One of the characteristics of single phase and three phase induction motors is that the speed torque curve is very flat. Thus the motor can be overloaded, almost to the point of breakdown, without very much drop in speed. Thus a 1 HP motor can withstand brief overloads of say 1 1/3 HP, but of course would eventually burn up with this overload in continuous operation. Perhaps this is where the "developed HP" term comes from, but this term is not used by NEMA. Some motors, built with higher temperature insulation are rated 1.15 service factor, and this would be so indicated on the nameplate. Induction motors are wound around a certain even number of poles, which gives the motor a set speed at 60HZ, ie: 3600 rpm - 2 pole, 1800 rpm - 4 pole, 900 rpm - 6 pole, ect. The actual full load speed will slightly less due to slippage between the field and the rotor, thus nameplate full load speeds are usually around 3450 rpm - 2 pole, 1750 rpm - 4 pole, 870 rpm - 6 pole.
A great many universal type electrical motors and now being used to power stationary power tools. This of course is a cheaper power source than a NEMA induction motor. Universal motors can be made to operate on A/C or direct current. They have brushes and commutators and operate at very high speeds, 10,000 to 20,000 rpm being very common. There are no standards, NEMA or otherwise for universal motors. They are electrically less efficient than induction motors and characteristically they have a much higher noise level. They also have a much shorter life span. Since HP is basically a formula involving speed and torque, universal motors get their HP essentially from speed rather than torque. Quite often now-a-days, universal motors are rated in amps, a rating whose only useful purpose is to help you ascertain if your circuit is adequate. For the user, the actual HP would be largely a guess
8Iowa
What you said is basically correct but fact is most woodworking tool manufactures don't used NEMA rated motors. Most in fact are sparsely labeled motors from over seas. The only real concern they have is frame size and what hype they can use in their ads. The main concern of most non industrial tool manufactures is obtaining the UL sticker which limits their input amperage by voltage.
Nonetheless the fact is two motors turning basically the same speed drawing basically the same amperage produce nearly the horsepower, certainly not the differences some manufacture claims of 2 and 3 horse power.
I agree while amperage is a fairly nebulous term the fact remains you don't get something for nothing. Wiser men than me have decided that 745.69982 watts of electrical energy eguals one horsepower of mechanical energy and proven science tells us 745.6992 units of energy measured in watts
absolutely/B] can not/will not produce more than 745.69982 watts of energy output. Also knowing that friction causes some input energy to be lost in heat the productive or useful output must always be less than input. No exceptions!
Now if people want to play games and make believe they have discovered perpetual motion or magically multiplication of power by listing ridiculous horsepower claims fine. But the fact is they MUST use terms like developed or realized horsepower and that should alert everyone that they are playing games.
Again the government has jumped on more than one manufacture over this very issue. New truth in labeling laws that are being enacted and class action suits have made most horsepower ratings without an additional adjective a thing of the past for consumer products.
Posted: Tue Jan 27, 2009 3:10 pm
by Ed in Tampa
8iowa wrote:...Table saw manufacturers certainly consider any saw that will operate on a 120V 15 amp circuit as "underpowered"...
Uh??? Nearly every table saw manufacture doing business in this country sells a multiple models of table saws with those exact specifications. In fact if they have UL approval they must be within those specs.
I know many many commerical cabinet and wood speciality shops that their only saw is 120v 15 amps or less.
I'm willing to say nearly every house built in this country was constructed from wood cut using a saw that ran on 120 volts and used 15 amps or less.
Some how people over time have confused 3 and 5 horse power saws which were originally produced for production line work as the rudimentary or basic need in woodshops. Poppycock!!!!
What is commonly called a cabinet saw, (Unisaw, Powermatic and etc) was first produced to be used in manufacture setting that utilized power feeders and 24/7 operations. Today they are found in home workshops not because they are needed but because we basically have more money than brains.
Posted: Tue Jan 27, 2009 3:21 pm
by JPG
Ed...8Iowa...AMEN!!!!! If it doesn't PUT OUT The HP claimed 24/7, it ain't TRUE HP! Reminds me of the the audio amplifier 'power output' claims of years gone by. "Instantaneous peak power" A ridiculous term which merely allowed one to double the actual output power capability. Power is only meaningful over time in which actual work is done. Very GOOD responses by the way!:)