Andy (Felker/Target Tile Saws) has posted this in the Pro Hangout. In order to have it handy for reference, I\'ve copied it and placed it here. It\'s an excellent article.
J.B.
The purpose of this post is to provide as much pertinent information as I can about electric motors and tile saws so that anyone contemplating a purchase can make an informed decision. Motor types that might typically be found in tile saws are permanent magnet (DC), universal (AC/DC) and AC (Single Phase). Most of what I discuss here is slanted towards the larger tile saws with 1.5hp and up motors, though everything would also apply to the smaller less powerful motors used on portable tile saws.
For our purposes we should consider a few things when looking at a motor. Horsepower is the most sited factor but it is only one of several that should be considered. A motor’s Service Factor, Code, and Duty, also play important roles in how that horsepower will be applied to the material being cut on the tile saw.
The first thing to remember is that horsepower ratings can be deceiving, very deceiving.
All 1hp or 1.5hp motors are not equal and will not cut tile with the same efficiency or speed. Just thinking about the different physical sizes of motors you have seen that are rated the same horsepower will tell you how this can be true. To truly begin to understand what the horsepower rating means you have to understand how that number is assigned and what factors are considered in assigning it.
Horsepower is Torque x speed / 5250, torque is in lb-ft, and speed is rpm’s. The important thing to note here is that the rated horsepower is calculated at one specific motor speed. (And also pulling a certain assigned amperage, which we will discuss later.) When the motor is working, as in cutting through a tile, the motor speed will likely be different each time, which means the actual horsepower will be different. That is all I am going to say about that because I read it in a book and we don’t have to fully understand it to make a buying decision. If everything is equal, there wouldn’t be much else to say and comparisons of motors would be easy, but, everything isn’t equal so we need to know more.
On the serial number plate of the motor, besides horsepower there are several other factors listed that affect performance significantly. The first we will discuss is called Rating. On tile saw motors you may see ratings listed as Saw Duty, Intermittent or Int with a number after it, such as Int 30, or continuous or cont.
In order for a saw to be rated Continuous Duty, it must be able to pull the rated horsepower all day, every day, without overheating or shutting down. This is the best situation to have, in my opinion. Though you will not cut tile all day everyday, you could, and you won’t put your saw through anything it cannot handle.
To be rated Intermittent Duty a motor must be able to supply the rated horsepower for 5 minutes, 15 minutes, 30 minutes or 60 minutes straight without overheating or shutting down. The minutes will be noted after the intermittent rating, such as “Intermittent 30”. This is still a good option because, cutting tile, you should not put your saw through anything that it couldn’t handle.
The Saw Duty rating, means almost nothing. To be saw duty rated for a certain horsepower, a motor needs to hit that horsepower rating for just a very short time period. An example would be a common table saw used to cut through a 2X4 stud. It does not have to be able to maintain it without overheating or shutting down at all. It just has to hit that horsepower for that second. With these motors it is hard to tell what you are getting. They are usually lower cost, lighter duty motors. They may or may not perform well in tile applications, but there really isn’t a good way to know for sure except for trial and error.
One way to play games with horsepower ratings is to rate a motor as saw duty or intermittent duty with a higher horsepower than could be used for continuous duty. How a motor is rated is up to the manufacturer or OEM of the saw. A motor that might be rated as ¾ hp continuous duty may also be able to be rated 1hp Intermittent 15, or 1.5hp Saw duty. This is legal and in many cases is left up to the OEM to decide how the motor should be rated on their application. A manufacturer may choose to rate a higher horsepower and use a different duty rating in order to advertise the higher horsepower.
Another trick is to rate a motor at high horsepower using a high amperage draw that is not readily available when using the saw. When a motor is rated, the horsepower is given on the serial # plate and the amps that the motor uses to achieve that horsepower are given also. I have seen a small motor saw duty rated at 2.5hp, listing the amps as 30. It would pull 2.5hp, but did it by drawing 30 amps on a 110 circuit. Of course, you cannot easily find a 30 amp circuit breaker on a 110 circuit, so, when the saw was used and put under load, and tried to draw 30 amps to provide 2.5hp, it blew breakers. Now, the manufacturer told the truth. If you could find a way to provide the 30 amps you could get the 2.5hp, you just would not be finding the 30 amp circuit to use in normal everyday tile cutting locations. And even if you could find a 30 amp circuit, all wiring, including any extension cords, would have to sized for 30 amps, which would be 10 gauge or larger. Try to look for a motor with amperage listed under 15 so that it will run on common circuits. Certainly, amp draw should be under 20 amps. Anything higher than this will be hard to run in everyday applications without tripping breakers.
When cutting tile, torque is also important. Some granites and porcelains can be pretty tough to cut, and the higher the torque a motor is able to produce the faster the cut may be made. Motors sold in America have a rating listed under “Code” on the serial number plate that helps to determine the amount of start-up torque a motor has. A letter designates it. The later a letter appears in the alphabet, the higher the torque of the motor. On larger 1.5hp saws, a rating of “J” or better works well. It is possible to have a tile saw with a higher horsepower motor, but lower start-up torque code, which will not cut tile as effectively as the lower horsepower saw with better start-up torque. This is possible because under load the motor with the lower start-up torque will not be able to maintain rpm’s as well and will lose cutting power.
Another rating to check is the Service Factor. The service factor is listed as a number that designates how well a motor can handle being overloaded on a continuous basis. A motor that has a service factor of 1.15 should perform when 15% overloaded without overheating or damaging the motor. When no service factor is listed, the service factor is assumed to be 1.0. However a 1.5 hp with a 1.15 service factor is actually a 1.725 hp motor (1.5 X 1.15). It is good to have that reserve capability in an application like tile sawing.
These are not all the design factors involved or listed on a motor, but they are the most important in tile saw applications, at least in my experience covering over 20 years in the business. (Ouch, that’s way too many!) If you have any questions or comments feel free to make them. My whole purpose here is to pass on information that I have found useful to tile contractors in the past. The better informed you are the happier you will be with your purchase. Much of this information is overlooked when making a buying decision because it is not readily available to the user. Now, hopefully, it is.
Our friend Andy Lundberg seems to get a lot of questions concering the sharpening of wet saw blades, so he has put together this little article explaining the whys and hows. Andy's forum username is Andy L.
Tips for sharpening tile blades.
A tile blade does not really cut, it grinds. It grinds because there are many faceted diamonds exposed on the surface of the diamond blade grinding away at the material. The idea is that, as the diamonds slowly become “dull” or their facets become rounded and therefore don’t grind well, the material surrounding the diamond also wears away and lets the dull diamond fall out and a new diamond that is lurking below it will become “exposed” and start to cut in its place.
If you have a good match between blade and material this will happen as it should and your diamond blade will stay sharp and cut well. If, however you are cutting a very hard material with a blade that is not suited for that purpose your blade may become dull and need sharpening. A dull blade is one where most of the exposed diamonds no longer have sharp faceted surfaces, but have become rounded off. Instead of grinding away the material they kind of “roll over” it, almost like the worlds hardest ball bearings. This is not good, as anyone who has experienced it can attest. BUT there is a way around this, the blade can be sharpened.
To sharpen a blade the metal powder, or matrix , surrounding the dull diamond has to be worn away so that the dull diamond can fall out and a new sharp diamond can be exposed. This is not so hard to do. The trick is to get a pretty abrasive material, like a soft brick, or concrete block or even a grinding stone made to sharpen blades, (if you want to spend that extra money). Then cut the water back to maybe half way if you have it all the way open. This insures that you’ll have a nice pasty, abrasive slurry when you cut. The more abrasive this slurry the quicker to sharpen the blade. Now remember, to sharpen the blade you are going to wear away this dull layer of diamonds. If you could wear away a layer of diamonds in just a few cuts you wouldn’t be very happy with your diamond manufacturer because blades would wear out so fast, so be patient. It’s not possible to say how many cuts it will take. This depends on how dull the blades is to start with, how abrasive the material you cut is, how much water you use and how “hard” the blade is. (This means how hard the powder surrounding the diamonds is and that effects how quickly it can be worn away). BUT, if your are patient the blade will sharpen, guaranteed. And it will be as good or better than new when you are done. If you ontinue cutting a material that is too hard for the blade, ie, is not abrasive enough to wear away the powder around the diamonds, it will eventually get dull again, but, you know what to do then, don’t you? If you are constantly sharpening your blade, you need to get another, softer bonded blade to cut that hard material. If you are only cutting a limited amount of the hard stuff then maybe its worth it to you just to sharpen as needed.
At any rate, the good thing about diamond blades is , when you sharpen them they perform like new again, and you can sharpen them as much as you like till they are worn out. I hope this helps you and keeps some potentially good blades from being discarded just because they are dull.
Happy cutting!
Andy Lundberg, Product Manager
Felker and Target Saws
Good article from Andyl....I just wanted to mention,that if you can't find a brick or block or sharpening stone...a scrap peice of cement board does wonders too...maybe that's why they call it WOnderboard?
Edit by Mike2:
Another member (Boggyboy) reports having good luck using a "brick" of deck mud made from leftover mortar after building a shower pan.
If I have some around, ceramic wall tile which is relatively soft works good.
For drilling smaller holes in porcelain as well as a number of other hard materials like granite, most all carbide bits commonly available in hardware and building supply stores seldom work.
Porcelain tile speciality bits like those from PTC work very well and can be ordered through our On-line store.
edit: Link to Contractors Direct at the bottom of the page and labeled "Tile Tool Store"
These bits will drill all porcelain PEI grade 5 tile, ceramic, granite, marble, and other hard to penetrate materials. Typically 10 to 15 seconds is all it will take in grade 5 porcelain.
Water should always be used to cool the tip/cutting edges of these bits. Spray bottles, dams around the holes using putty, cookie dough/silly putty?? , or even a wet sponge/towel squeezed over the cutting area are various means to accomplish this. (Do not use oil based puttys like plumbers putty on natural stone as it could leave a very hard to remove stain).
Optimum drill speed is 900 RPM. If using a rotary hammer drill, no hammer action should be used.
Here are two of the many threads posted on the Forum on drilling tile where you may pick up some other good tips.
An finally, here is a picher of a hole drilled by da Mudmeister himself, John Bridge, through a hard bodied porcelain tile using a PTC bit. Nice and clean, eh?
P.S. And finally, YouTube videos of PTC bits in action.
Cutting tiles diagonally with a small saw (Felker TM-75)
We frequently get questions from members on how to go about cutting 12” and 13” tiles diagonally using a small saw like my personal favorite, the Felker TM-75.
This thread with lots of pichers (that’s how the Texan’s round here spelt pictures BTW ) is intended to address those question and perhaps even provide some usefull tips to those who have done this before but have not quite mastered the technique. There are indeed other ways of doing this but I will present this method for purposes of this article. Keeping the techniques easy to describe and straight forward is the goal here.
Step 1 - Marking the tile(s)
If you plan to use 1/8” or wider spacing, perfect alignment won't happen if you simply cut the tile in half (see footnote, bottom of thread). Assuming you want to bring the full points on whole tiles flush with the cut edge on adjacent half tiles, you must account for the grout spacing when cutting tile’s diagonally. I won’t go into the mathematics and what Pythagoras had to say about all this, just trust me. Or ask one of the kids, they will tell you all about it.
In this case I plan to use 3/16” spacing so I’ll take one of those spacers, center it over the points and make a mark, 3/16” wide on both sides of the spacer, at each end.
Next, draw two connecting lines all the way down the tile using a straight edge. Or better yet take some tape, place it about ¾ of the way down and make your marks on the tape alone.
At this point you should have two marks at the opposing ends of the tile and two on the tape. You will be cutting along these marks.
Step 2 - Alignment of the tile for cutting
There are a number of ways to do this but personally I think the following method is easiest to demonstrate. You need a measuring device, in this case a sliding square. Place the heel of the square against the end of the cart fence and slide the straight end out until it “kisses” the blade, then lock into place. You now know exactly where the cut will be as measured from the right hand side of the cart.
Place the marked tile on the cart and align it such that the blade meets the inside of the right-hand mark at the tile’s point, while at the same time the mark on the tape is aligned to the sliding square.
Now you are ready to turn the saw on and cut. Options however at this point include clamping the tile to the cart or placing the miter guide on the fence (if there is room) just to add some stability. As you build experience cutting tiles this way you may not need to do any of these “extras” but to begin with, you might give them a try.
Step 3 – Cutting the tile
Power on the saw, hold the tile to the cart fence with both hands push it through until the blade reaches the mark on the tape. Turn the saw off, slide the cart back and take a deep breath. Congratulations, the hard part is over.
Rotate the tile 180 deg. and again align the inside of the mark with the blade
while at the same time aligning the previously cut line to the square.
Power on the saw, hold the tile to the back cart fence with both hands and complete the cut.
Now we need to trim the other half (left side) of the tile. If you used tape for your marks it most likely came off so apply a new piece and mark again using the straight edge.
Align the marks as in the previous steps
Power on the saw, cut to tape mark and power it down.
This time to finish the cut you do not need to flip the tile over. Simply push it forward completely onto the cart, align the blade into the cut and the mark on the end with the sliding square,
power the saw back on and complete the cut.
Step 4 – Finish the edges and set
One last housekeeping chore is to dress down those sharp cut edges. There are many ways to accomplish this: hand stones in the 80 grit range, 80 + grit sandpaper using either hand or power tools, or go for it with a wet polisher and an 80 grit + diamond pad.
Once that is complete, put it altogether and you are good to go.
P.S.: Cutting 16” tiles diagonally
Another member asked if it was possible to cut 16” tiles diagonally on a TM-75 saw. Let’s see……….
Mark your tiles as before except this time I will demonstrate making just one cut (no spacing allowance taken) right down the middle.
With 16” tiles it’s easier if you use the sliding square from the left side of the cart. This time I will use a previously cut scrap piece to center the square with the middle of the blade.
Line up the marked tile, centering one tip to the blade, while at the same time centering the pencil mark on the tape to the square.
Power on the saw and while holding the tile with both hands to the cart fence, push it through to the mark.
Power off the saw, flip the tile around and repeat the alignment process.
Finish the final cut.
Dress down the sharp cut edges and you are good to go.
I find it almost as easy to cut 16” tiles diagonally on this particular saw as it is 12 and 13-inch tiles.
P.S. #2 - Cutting 18 inch or larger tiles.
Lately there have been a number of questions as to if the TM-75 can cut an 18" tile in half. For straight cuts the short answer is No. But it's a qualified No.
There is 8" of clearance between the blade and the upright motor support post.
Thus, only an 8" cut off a large tile can be made. Two cuts would be necessary to cut an 18" tile in half, but then of course you only end up with one useable half.
For cutting 18" tile diagonally in half, the answer is Yes. That can be done. However proper alignment gets a little tricky with 18" plus tiles because the entire top of the back fence is covered. An alignment device other than a sliding square must be used. One capable of reaching underneath the tile to rest against the end of the cart fence.
I have made one of those measuring devices but I think I will declare all that real tricky cutting business outside the scope and intent of this article. Keeping it easy and straight forward is the goal here. And I think once you actually try some of these techniques you will find they are indeed easy to master.
P.S. #3 - And finally, the blade
Every tile in this article is very hard porcelain and was cut using the MK 225 Hot Dog blade.
Footnotes:
Since writing the original article I have received a number of requests to further explain the difference between simply cutting the tiles in half (one cut) versus removing the space allowance from the center which requires two marks and two cuts. What would the tiles look like with and without this spacing allowance removed you have asked.
I think by far the easiest way to explain all this is by simply posting a side-by-side picture comparison. The left hand column below depicts tiles simply cut in half, one cut right down the middle with no allowance removed for spacing. The corresponding tile to the right has been double cut with the spacing allowance removed. Actual examples shown (as marked) are for 3/16”, ¼”, 3/8” and ½” spacing.
The choice is yours to make:
If you find the point-to-cut-edge alignment depicted on the left more appealing then you only need one cut, right down the diagonal middle of the tile.
Here then is the difference in mechanics - Only one mark on the tile is necessary and this mark is then aligned to the center of the saw blade. Adjust the sliding square so that it lines up with the center of the blade as opposed to “kissing” the side of the blade as previously discussed. Alternatively one could partially cut into a scrap piece of tile and then align the sliding square to the center of this scrap cut.
After completing the single cut you are finished except for the dressing down step to remove the sharp sawn edges
I think we all know what happens to our blades. We cut certain materials and the more we cut them, the "duller" the blade gets. Porcelain is the 1st thing that comes to mind. Some hard granites can also have you pulling hair as the cut speeds drops. But why is this happening when we aren't having these problems with soft-body tiles or limestone etc?
The blades we use are designed to cut a specific hardness group. The metal matrix which holds the diamonds is designed to wear appropriately for this or that hardness group. Most of our blades are an alloy of steel/nickel/(assorted other metals). A blade suited specifically for marble/limestone will have a brass/other alloy. Without getting into complexities of why these alloys are chosen, the reason is simple. The material being cut is what keeps diamonds exposed by wearing away at the matrix, so that as exposed diamonds are worn-down, fresh diamonds are being exposed to replace them. I think we all know this, but for the sake of posterity let me drone on...
What happens when we use a blade designed for cutting one hardness group on a different hardness group? "Glazing" is the generally used term for using a blade designed for a softer group on a harder group, and visa-versa; harder on softer. But why? Using a "hard" blade on soft makes sense; the softer material can't remove the hard matrix. On the reverse; "softer" blade cutting harder material, you would think the harder material would also work better for removing matrix. Now we get to the 2nd difference between diamond blades: specific diamond hardness. We have all been led to believe that diamonds are the hardest substance at a 10 on the Mohr scale. Nothing else is as hard. What isn't as common knowledge is that there are levels of hardness at 10: 10, 10.1, 10.2, 10.3....... Generally the hardest diamonds are reserved for the gemstone industry. How do you polish a diamond? With harder diamond grit of course!
So another factor in a blade designed for cutting the hardest materials is the specific hardness of the diamonds set in the matrix. All diamonds are dulled as cutting takes place. the cutting surface becomes rounded, diminishing the "cut" activity as a harder material is forced through a softer material. In this state, the blade encounters a resistance to spinning, as the slot it is cutting begins to bind on the blade. The exposed diamond becomes almost flush with the matrix. Why? because the material being cut has reduced to a fine "sawdust" where it was once being gouged out in larger particles. Let's store that concept for now.....
Entering the world of the glazed blade, let's look for a minute at another abrasion function, for that truly is the way a diamond saw "cuts": by abrasion. A very necessary function of stonework is abrasion. Sandpaper, grindstones. A grindstone is kind of like a really thick sandpaper in a way. They too have glazing problems. The abrasive has become dull. It is developing a residue build-up you can see on the grindstone, keeping the abrasive from contacting the material being abraded. Net affect from continued attempt at grinding leads to lots of heat being generated but almost zero "cutting" being accomplished. So we must dress the stone, which below I show the tool used and a close-up of what does the dressing.
A stone dresser is held against the grindstone loosely, taken away to stop the spurs from spinning, re-applied over and over, across the face of the stone. If you have never used one of these, you would be amazed at how fast they work, and how much material they are taking off the stone. But why? the spurs/discs are just a hardened steel, much softer than the stone. Actually, if you held one of the spurs against the stone without it spinning, you will watch the spur be reduced to nothing in no time. Light bulb time: the spinning is the key, as is the spur design. That, when combined with the different rates of speed between the stone and the spurs creates the dressing action: the spurs impact the grindstone quickly and depart the grindstone, creating a gouging of the grindstone as small chunks are knocked-off. The stone may be harder than the steel, but it is also more brittle to impact. This is easily evidenced by dropping a piece of glass (harder) and a lead ball (softer), glass breaks and the lovely properties of metal only makes them dent.
So why don't they have a neat little dresser for diamond blades like the grindstone dresser? Well they do, but it doesn't look like it. A Diamond Blade Dressing Block works with the same principle as the grindstone dresser but a different format.
When a diamond blade cuts a slot (or saw kerf), the space between the blade and the slot walls is very limited. A diamond blade dressing block is made-up of loosely adhered particles of a very visible size; very close to the size of the sand in our fat or deck mud. Light bulb time again
All that leads up to what the headstone guy told me back in 1988 when we were opening a stone fabrication shop. I'm going to paraphrase here:
'The best thing to use to de-glaze your blades is to mix-up some of you tile guys' deck mud and make a brick out of it. If you can use sand made from crushed rock all the better, but regular beach sand works too. Then you run the blade through it over and over, slower at 1st and faster and faster until you are forcing the cut as fast as you can make it cut.'
What happens is that the loosely held sand particles get knocked loose rather than being cut (abraded), and get caught in the saw kerf, rolling between the kerf walls and the blade gouging out the matrix and they go until expelled. The matrix is quickly worn away, the dull diamonds fall out, and nice fresh, sharp diamonds become exposed without being dulled by the cutting process. Alacazam; dressed blade cuts like brand new.
Thank you headstone guy. I guess something was learned in what he told me he was 5th generation Italian Stone Worker handed-down trade secrets. WE SALUTE YOU
Now you can go out and buy yourself an actual Diamond Blade Dressing Block. They are ideal. But why not just use what is readily available, costs nothing, and works (pretty much) just as good as the expensive dressing block? If you don't have any dried chunks of deck mud, fat mud or stucco slag work ALMOST as good. And it's all better than any kind of brick, but cinder block is next in line for a workable blade dresser...
And at last, 
Congratulations, the hard part is over.
