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  1. #1
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    Table saw question - blade height

    So--

    I've been doing a lot of reading about using table saws. One thing that seems to give an incredible mixed bag of answers is with regards to setting the correct blade height for through cuts.

    I have generally always raised by blade to the maximum height. As near as I can tell this minimizes the risk of kickback because the forces on the wood at the point of cutting are maximized downward. If you set the blade just high enough to go through the work, you are maximizing the rearward forces.

    Additionally, max height seems best for equipment maintenance. the contact surface between the cutting surface and the blade are minimized. Cooler blade, less force required to feed the work, better safety.


    So... what are the arguments for setting the exact height on a through cut? I've seen it said, but I've never seen it explained.



    PLEASE NOTE

    BEFORE I GET ANY MORE OBNOXIOUS REPLIES... THIS QUESTION IS POSED DUE TO EXPOSURE TO CONFLICTING INFORMATION AND IS BY NO MEANS AN AVOCATION OF EITHER METHOD BY ME (I AM NO EXPERT).

    FOR INSTANCE http://www.waterfront-woods.com/Arti...w/tablesaw.htm

    or

    http://en.wikipedia.org/wiki/Table_saw#Blade_height

    I SIMPLY WANT A SANE DISCUSSION ABOUT THE MERITS OF EITHER METHOD. PLEASE REFRAIN FROM EXTRANEOUS OR PERSONALLY DIRECTED COMMENTARY... IT IS NOT LIKE IT ISN'T AN OPEN QUESTION.

    THANKS


    Additional discussion...

    low blade height can lead to burned wood. In this link a blade manufacturer recommended a higher blade height be set.

    http://www.toolcrib.com/blog/2008/07...-burning-wood/

    Yet more...

    http://1manstand.com/tablesawtips.html

    "16 Contrary to conventional wisdom, setting your saw blade height low (e.g. just greater than the thickness of the work piece) may be more dangerous than having it set too high. A low blade height increases the force of kickback because the teeth in contact with the work piece are pushing straight back instead of down. Low blade height also increases drag and heat buildup because more teeth are in contact with the work piece and each tooth cuts a longer path through the wood. Too high a height isn't good either, increasing the risk of a body part contacting the blade. A reasonable compromise is about 1-1.5" of blade showing above the work piece.
    If you are a beginner, or you don't feel comfortable around the saw blade, or you are using heavier clothes (never use loose fitting clothes around any moving equipment), you can adjust the blade height to slightly above the surface of the material being cut unless operations dictate otherwise (corner cuts). You will minimize injuries in the unfortunate event you do have an accident."



    The more I look the more I seem to be seeing that Min is least desirbable, Max is better but can have problems, and 1-1.5" is best.


    And from Jim Tolpin.

    "A circular blade runs cooler and with less feed pressure when set high, because the teeth are at a smaller angle of attack relative to the wood, but the increased tooth exposure is more hazardous. My rule of thumb (and I still have both) is to set carbide teeth just high enough to clear the top of the wood. At the most, to reduce splintering, I'll raise the blade until the gullets between the teeth are fully exposed."

    p. 77 Table Saw Magic 2nd ed.

    Thanks for everyone's input.

  2. #2
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    RE: Table saw question - blade height

    I generally try to put the blade about 1/4" higher than my work. Having that huge amount of exposed blade is scary.

  3. #3
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    RE: Table saw question - blade height

    >I have generally always raised by blade to the maximum
    >height. As near as I can tell this minimizes the risk of
    >kickback because the forces on the wood at the point of
    >cutting are maximized downward. If you set the blade just
    >high enough to go through the work, you are maximizing the
    >rearward forces.

    I don't buy into this one, myself. Kickback rarely has anything to do with the front of the blade. It's almost ALWAYS caused by stock riding up the back and onto the top. There are other reasons that raising the blade all the way CAN be good, though. A "more vertical" attack can sometimes reduce tearout, for example.

    >Additionally, max height seems best for equipment
    >maintenance. the contact surface between the cutting
    >surface and the blade are minimized. Cooler blade, less
    >force required to feed the work, better safety.

    I have heard the "blade runs cooler" explanation in the past and I'm still not sure it's much help. I'm sure it's true, i just don't think it's worthy of the credit many folks give it. As far as less force to feed the work, maybe - but if you're unhappy with the force it takes, maybe yer blade needs sharpening or cleaning? As for safety, i soundly disagree - more blade exposure is not safer than less. I don't know how much more dangerous it is. If you only have it 1/8" above your work and your hand smacks down on it - how deep's that cut gonna be? If it's 2" over the work - where's your hand?

    >So... what are the arguments for setting the exact height on
    >a through cut? I've seen it said, but I've never seen it
    >explained.

    Me? My blade is usually JUST high enough to make the cut, maybe a little more - about 1/8-1/4" over the surface. Unless it's flimsy stuff, this works most of the time. Flimsy stuff tends to ride up the front of the blade so I'll raise it up a bit more to kind of help keep it under more control. I also have a nice big healthy pushblock for these cases, too. If I find I have a blade that can't hack the wear-n-tear that lowering the blade might add to the operation, I find a better blade.

  4. #4
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    RE: Table saw question - blade height

    I do the same as I was told by a pretty sharp guy to do that. Some though, keep the blade very high. I have no idea why and have never asked.

    I guess you can get stuck in your ways kinda quickly sometimes.

    "Red"

  5. #5
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    RE: Table saw question - blade height

    +1 to what Jason said. The only time I raise the blade significantly over the work is to try to minimize tearout.

  6. #6

    RE: Table saw question - blade height

    As near as I can tell this minimizes the risk of kickback because the forces on the wood at the point of cutting are maximized downward.


    While that may sound logical, it's BS. If you wanna minimize kickback of your TS, use a splitter with kickback paws.

    Now, to test this blade height "theory" about helping to reduce kickback....

    Go crank the blade on your TS all the way up, loosely push a piece of wood into the blade and purposely cause a kickback situation and see what happens (I advice your to wear armor, or duck out of the way)

    Now raise the blade just high enough to do the cut, and follow the directions above and see what happens. (Again, wear armor of duck out of the way.)

    I hope you don't do these things, cause that would be just plain silly, I'm just trying to make a point.

    The splitter and kickback paws are what help to prevent serious kickbacks, that and proper technique. It doesn't matter what height that blade is set.

    Here is my logic, the less blade sticking out from the wood is less blade that can rip me a new @$$hole.

    I keep the blade just high enough to expose the teeth of the blade.

    I see it like this... if only a 1/4" or less of that blade is exposed, the chances are it'll only be a 1/4" deep cut if something happens, I can handle that. But if there is 1 or 2 inches of blade exposed, chances are I'll be missing a few fingers maybe even a hand is something happens.

    In my experiences, 100% of my kickbacks are cause by not using the splitter/paws or improper technique.

    Because of my stupidity, I've gotten my finger in the blade once.

    So, because of my stupidity, I expose as little as possible of the blade.



    "you needn't troll the experts ..just come straight to the source" - Limey aka:Robert Bolton

    [link:www.mgsawmill.com|M&G Sawmill]. Makers of the finest sawdust in Texas.
    Oh, did I mention we have hardwood as well?

    http://www.mgsawmill.com/images/flag.gif http://www.mgsawmill.com/images/texas.gif

  7. #7
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    RE: Table saw question - blade height

    I was taught and keep my blade just high enough so that the gullets are exposed above the work, typically 1/4"-3/8".

    Two practical arguments against raising the blade higher than minimal clearance quickly come to mind.

    1. More exposed blade is more opportunity to cut something soft, 3/8" exposed blade height can mangle or sever a finger, 1 1/2" can sever a hand or cut through all of the important stuff in your wrist.

    2. Kick-back usually begins at the rear edge of the spinning blade. With the blade set low kick-back aims at the altitude of your groin or hip, with the blade set high the kick-back stock tends to come at your face. DAMHIKT

    The argument for better cooling is generally bogus, the blade is experiencing cooling below the table as well as above. Raising the blade so that an arc chord length of 8" is engaged in wood offers less blade surface area to free air cooling than lowering it to engage a arc chord length of 5".


    Measure once... cut twice.

  8. #8
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    RE: Table saw question - blade height

    >
    >I don't buy into this one, myself. Kickback rarely has
    >anything to do with the front of the blade. It's almost
    >ALWAYS caused by stock riding up the back and onto the top.
    >There are other reasons that raising the blade all the way
    >CAN be good, though. A "more vertical" attack can sometimes
    >reduce tearout, for example.
    >

    Correct... so the higher the blade, the more the front of the blade keeps the work on the table... and if the work does ride up... the forces are more to the ceiling than to the operator.

    >
    >I have heard the "blade runs cooler" explanation in the past
    >and I'm still not sure it's much help. I'm sure it's true, i
    >just don't think it's worthy of the credit many folks give
    >it. As far as less force to feed the work, maybe - but if
    >you're unhappy with the force it takes, maybe yer blade
    >needs sharpening or cleaning? As for safety, i soundly
    >disagree - more blade exposure is not safer than less. I
    >don't know how much more dangerous it is. If you only have
    >it 1/8" above your work and your hand smacks down on it -
    >how deep's that cut gonna be? If it's 2" over the work -
    >where's your hand?
    >

    A bigger issue than the blade runs cooler is that takes less force to feed the work. As you allude, that's what makes sharp knife safe is that you don't get yourself in a position where you're trying to force it. Blade is brand new. I definitely physically feel less resitance when the blade is higher.

    As far as the argument about smacking my hand down on a 2" of blade. On a through cut I have the guard down.

    >
    >Me? My blade is usually JUST high enough to make the cut,
    >maybe a little more - about 1/8-1/4" over the surface.
    >Unless it's flimsy stuff, this works most of the time.
    >Flimsy stuff tends to ride up the front of the blade so I'll
    >raise it up a bit more to kind of help keep it under more
    >control. I also have a nice big healthy pushblock for these
    >cases, too. If I find I have a blade that can't hack the
    >wear-n-tear that lowering the blade might add to the
    >operation, I find a better blade.

    I appreciate the response. Still, wear and tear is wear and tear. Even the best blades need to be sharpened eventually.

    As I said... I've seen both views suggested, and was seeking more input... so thanks.


  9. #9
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    RE: Table saw question - blade height

    I understand you had an accident... There is no need to be rude with the headbonking thing or suggesting idiot experiments. I was exposed to conflicting information and I came here seeking discussion in good faith.

    I know you had an incident but don't be a jerk.


    Who doesn't use a blade guard on through cuts BTW?

  10. #10
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    RE: Table saw question - blade height

    I'm of the school that keeps barely enough (only about 1/8") blade peeking out over the top of the work to complete the cut. That leaves less blade actually embedded within the work than a full-height blade.

    The blade stays COOLER with VERY LITTLE tooth exposed above the workpiece... because there's more blade exposed under the table saw's top to radiate that heat away.

    If I screw up somehow, some way, I stand to lose a slice of skin across my palm (or wherever) an eighth of an inch deep, not all the way through.

    While it may take slightly more pressure to feed the work that way, it IS easier on the edges of my carbides... so they last longer between sharpenings. I don't like the pounding effect of slamming those carbides downwards into the top surface of the wood. I much prefer for the "anti-kickback" teeth to actually limit my feed rate, just like they're designed to do. They don't do that if the blade is full-height... you can get a full-gullet bite if the blade's raised too far.

    The quality of the cut is superior if the blade is raised barely above the top surface of the workpiece. Each tooth wipes the cut edge, cleaning it. If the blade's raised too high, all ya get is the upward sweep at the back & the downward sweep at the front.

    Part of that comes from doing some machine-shop work. I'd shudder to go slamming a HSS milling cutter through a steel plate like that - much much more comforting to let it nibble its way along like it does in ordinary shops.

    I'd nearly as soon climb cut on the table saw (don't!) as raise the blade significantly above the workpiece.

    -- Tim --

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