This is my first entry here so be kind.
A friend and I were noting the way we each set the depth of the saw blade in relation to the material being cut. I claimed that the blade should be set so the bottom of the gullets of the teeth were level with the material being cut. That is on a table saw you could see the bottom of the gullet as the wood was cut and on a skill saw you could see them under the material. He claimed the saw should be set a shallow as possible so there was less risk of cutting a wayward finger. What do you think???
Edited 6/25/2004 2:30 pm ET by Sawdustbill
Replies
I need practice being kind on this forum, so I'll respond. Of all the times I have been cut on the tablesaw (sounds scary I know) its never been because the blade was too high or low. My official answer is that it depends on your experience and level of confidence.
The technical advantage to a high blade (1" vs 1/4" - not too high) is that the actual tooth path through the wood is shorter - which is less likely to burn, and less resistance on the saw. A high blade will also hold the wood against the table better.
A low blade will have a long tooth path, following the arc of the blade longer. The potential danger to a low blade, is the tendency to lift the work up off the table during a cut if not held down adequately.
I was watching my shop neighbor rip some short, narrow oak through my saw, and he used a push stick to run it the rest of the way through the table. He was too leary to reach over and hold down the exiting end, and I told him that was more dangerous than using the push stick. If the blade were set too low, the piece would have lifted up over the blade, then would get caught in the gap with uneven push stick pressure (the only control point) and could have been scary at best.
If your careful and have sharp blades, it doesn't really matter that much.
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
Hi Sawdustbill and welcome to the board. DrDichroic gave most of the answer. Let me add another factor. If the blade is sticking up MORE, it will give less tear-out when it exits the wood at the end of the cut. So, all things being equal, higher is better. Don't forget to use a splitter too. It is a great safety device that many of us ignore.
If you're ripping narrow strips, make a push-stick out of LEXAN (NOT plexiglass), so if the blade teeth hit the push-stick, the noise will scare the s*** out of you but it won't hurt the saw teeth.
** Plexi is too brittle and will shatter like glass where Lexan will cut, bend, growl and scare you but will not send pieces flying.
SawdustSteve (making fine splinters and sawdust since 1960)
I think DrDichroic explained it all very well; there are good reasons to elevate your blade an inch of so above the piece being cut.
However, until you reach an experience level with the saw in which you feel a high degree of confidence in various cutting operations, I would recommend you keep the blade low. Even if your push stick finds its way into the blade, there will be way less chance for catastrophe if the blade is only projecting over the work by the space of a tooth.
"the noise will scare the s*** out of you but it won't hurt the saw teeth." From accident reports read here at Knots, the saw teeth are the least of the worries when Plexi explodes -- those flying shards can do serious bodily harm!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
I generally run my blades with so the full tooth (carbide) just clears the board. No particular reason, really, but that just seems to work well for me.
Re: push sticks:
Invest in a pair of grip-tites and the steel plate for the rip fence. And don't forget to use a splitter! Grip tite kit includes a simple one.
Johnny
Thanks for the answers to this first question. I particularly like the expalnations on each opinion. Needless to say I will set my saw with these comment in mind.
I use the bottom of the gullet as a starting point,for two reasons: if the blade is set too low, like barely clearing the wood, it will heat up and that will shorten the life of the tool.....I think is the main reason the tool manufacturers recommend the bottom of the gullet. Also with the blade set a little high, it will tend to keep the material flat on the table.....the lower it is set, the more tendency to lift the material.
That's a starting point; I vary from there depending on the material being cut and the material. With some fragile materials, the blade needs to be a lot higher to get chip free cuts, like melamine blades for example....you can get radically different results by varying the blade height just a little bit. I don't usually worry much if I have to go higher, and I routinely run pushticks through the blade....I do get more anxious if I have to lower the blade though. cabinetmaker/college woodworking instructor. Cape Breton, N.S
He claimed the saw should be set a shallow as possible so there was less risk of cutting a wayward finger.
...............
Dear friend,
That criteria seems quite good. Just high enough to do the job safely is the aproach here.
The narrower the work piece, the more reason to show less teeth. Wider sheets seem to require teeth well-above the top of the material, specially since they don't ride quite flat on the table top.
Fortunately, since they are wider, and the pushing hands or implements are not close to the blade, its OK. So your friend's claim is quite sound.
Safety is #1 factor, would say.
-mbl-
Your hands shouldn't be going anywhere near the blade anyway.....if they aren't going anywhere near the blade, how does having the blade lower make it safer?.....and if the blade is lower, the tendency to flip the board up increases, and that isn't safe.cabinetmaker/college woodworking instructor. Cape Breton, N.S
Dear Adrian,
You know well that "our hands shouldn't be going anywhere near the blade anyway" is the desireable scenario.
The view is not complete if we disregard the possibility of the hands going near the blade in unplanned and unwanted circumstances, a.k.a. accidents.
So, in the unplanned, unwanted scenario in which the hands or a finger gets where it ought not be, by accident, or other cause, a less exposed blade would allow less damage than one more exposed.
The comment is not meant to undermine technical reasoning, but rather to mean that one reason for considering safety the #1 factor is that if it is not clear, we may well end-up paying more attention to where and how we set the blade-teeth than where and how we set our own hands.
Number 1 factor means that there are other factors, of course.
Best wishes.
-mbl-
Well, we're going in circles....I understand your point, and it's well taken...I certainly understand that 'accidents' happen....been there, done the first aid as the paramedics come in the back door, and debriefed a class of shell shocked students afterwards.....BUT....with blade guards, which should be on the saw certainly in all professional situations for 90% of operations, for hobbyists too IMO....and push sticks.....and an understanding of basic operations, 99.99999% of 'accidents' can be short circuited......which leads back to the question of blade height. And in my opinion, having the blade too low is at least as dangerous, probably more, than having the blade set a reasonable amount above the material.
I said "an understanding of basic operation"; obviously, that's critical. I teach some night classes in basic woodworking as well as during the day.....I really don't have the time to do it, but a big part of the reason i do is because, class after class, I have people come in who often have a fair number of machines in a home shop, and it quickly becomes clear that they don't have the foggiest idea of how to use them safely ....it's frightening. It's very common for students to come up to me and tell me some of the EXTREMELY unsafe things they have been doing. Last year, an aquaintance lost a good portion of at least one finger, doing something not very smart....did she or her husband ever take any basic training in safe operation? No.
Anyway, I respect your opinion....just stating my case.
Regards,
Adriancabinetmaker/college woodworking instructor. Cape Breton, N.S
Yes I was one of those unfortunate accidents. Fortunatley the damage did not cause loss of digits but it did take a few months to regain the use of my fingers. Lack of knowledge is one factor which caused my problem but the other factor was poor equipment or rather poorly set-up equipment. I have learned an am really more cautious than ever. Repetitive tasks also seem to pose a rick factor. Watching both hand can cause problems as well. My feather board I purchased for the saw to hold wood in place didn't fit the saw I have or this wouldn't have happened.
I still appreciate your help and wise answer. More safety information is always helpful.
Stll making sawdust
Sawdust Bill
Thanks for your comment Adrian.
Have been using the 1/2 tooth-shows guideline (and in narrow strips even almost nothing) and reasoned that raising the blade another 1/2 tooth or more would not make any improvements on cut quality, but could deter much on personal safety. Besides, it's an easy rule to follow.
Will add, also, that much chipping prevention or control can be handled by how fast we push the material.
Slower pushing leads to less chipping. For better chip prevention, too, as many have posted elsewhere, masking tape can be used, or scoring.
When cutting melamine, or formica sheets, usually those are wide enought pieces, and if the blade is raised prudently for chip control, and guards are in place, can't say it shouldn't be done, but would still say push them carefully and not too hard and fast, for safety and better cut control and results.
Slowing the push has some of the effect of raising the blade since the cutting path of each tooth is shortened horizontally.
Well-being to all.
-mbl-
For Freud blades we recommend 1/2 of the tooth above the material. The reasons given thus far for having more blade exposed do not hold water if the correct blade is used for the application. For instance, it has been observed that if the blade is high the tooth won't travel as far in the material. This is true but not necessarily desirable because the exit angle of the tooth is too extreme for most uses. For ripping you need few teeth and aggressive angles and using a blade with more teeth and a lower hook angle but raised very high will mimic this to a degree but will compromise safety. A well engineered blade that is application appropriate will have the correct cutting angles and tooth quantities without raising the blade to the stop. Also, the advice that a blade should be raised as high as the gullet comes from the misconception that the chip won't be ejected otherwise. This is incorrect because the chip is ejected below the material - not above. That advice does not come from any blade manufacturers that I know of. Blades for manmade material are sensitive to blade height and a little adjustment in blade height makes a big difference. However, the blade should be lowered to reduce bottom chipping and raised to reduce top chipping.
In summary, when in doubt ask the manufacturer to help determine the correct blade and the recommended height.
Freud, Inc.
Hey Charles,
In reference to another discussion between Forrest and FS Tool, I seem to recall that Forrest blades are sharpened with finer diamond than other brands (like 600 vs 400 or something like that), and I thought that was vanity due to the fact (I think) that that level of sharpness disappears shortly after running a few hundred feet or less of lumber through it, so to me its not worth the extra cost, especially when time is money, and shipping back to the manufacturer is a bit nuts . . .
Is this somewhere close to reality? I have about a dozen blades from FS Tool to Freud to Everlast to ####, and they've all been sharpened too many times to count, (yet still plenty of carbide), so after a while it just doesn't matter - MDF will dull anything fast. I know that C4 Carbide is better than C2, and american vs foreign carbides are superior, but none of that matters when you cut dirty wood, man-made composites or aluminum - its all gonna get dull anyway. I sharpen my own blades now with a 180 grit diamond (continuous bond) blade I aquired, and the blades are insane sharp after I'm done, so the grit game seems a bit too hyped.
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
Now that is hilarious - What I typed in above where the #### appears, is Matsush*ta, but with an "i" instead of a "*", to reference the Japanese saw blade I have, and the Knots auto censor kicked in. I wonder if I'll be banned now :)
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
I hate to hijack the thread but here's the long answer:
IME, the ultra-fine grit diamond grinding is, indeed, mostly for hype. You are correct that the initial edge will disappear almost immediately. As you are probably aware, carbide is made up of tungsten particles held together with a binder. Unlike steel which compacts and bends as it is used, carbide sheds tungsten particles. The smaller the grains of tungsten, the sharper the attainable adge. Also, for a given grain size, the sharper the edge, the less binder there is to hold the tungsten together and the quicker it sheds the edge. So micro-grains allow sharper edges to a degree beyond which no benefit is gained. I often hear of people that hone their carbide tooling before use with 1000+ grit diamond hones. I believe this is a great waste of time unless it is done every couple of feet.
In regards to carbide grades, C4 is extremely hard and will wear a long time in mdf, plywood, etc. when used on a blade with appropriate cutting angles. But it is more brittle than C2 or C3 and therefore isn't suited for applications that require more impact resistance such as rip blades with steep hook angles. We produce our own carbide in 7 grades of hardness from about C2 to beyond C4 and use the grade that is best suited to the application.Charles M
Freud America, Inc.
Absolutely excellent info - Thanks - JB
"The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)
http://www.pbase.com/dr_dichro http://www.johnblazydesigns.com
All of us have opinions, but it is good to hear from someone with solid expertise.
Thanks for weighing in.
Noted....and I will go back to a saw, and experiment......but in my practical experience (20 years of driving tablesaws), the blade usually needs to be higher to get the result I'm looking for: (generally speaking) at least the height of one tooth, often a little more, which often equates to the bottom of the gullet depending on the blade type.....very close in the case of say an 80T crosscut blade, more for a rip. What determines the height, is the result ....and that's exactly what I do, I vary the blade until I get the result I want, which may be very different from what a laboratory or a formula will tell you.
I don't know if you deal with CNC tooling at all, but the same thing happens there......chipload is very important (important in all tooling, but doesn't get discussed much), and we use formulas to determine what the appropriate feed rates, etc., are, to get the proper chipload.....but it is very common to adjust settings based on what you actually see when the tool starts cutting the material. There are a lot of variables at work.
I sincerely don't mean this to sound confrontational, but it's because I don't know what your background is: do you have a lot of experience actually using saw blades on tablesaws, etc? Have you stood at the same saw, and cut up units of material, and felt a blade go from sharp, to not so sharp, to dull?cabinetmaker/college woodworking instructor. Cape Breton, N.S
Adrian,
You don't sound confrontational at all.
"do you have a lot of experience actually using saw blades on tablesaws, etc? Have you stood at the same saw, and cut up units of material, and felt a blade go from sharp, to not so sharp, to dull?"
Yes, I have many years of experience testing blades and cutters and I concur with your assessment that all theoretical computations are subject to alteration in real use. The 1/2 tooth is meant a guideline, not a "set in stone" amount. Some variance is expected but going much beyond that is a sign of incorrect cutter choice unless the manufacturer designed the blade to perform that way. I only speak for Freud.Charles M
Freud America, Inc.
I am suprised by all the differing opinions on this subject. Every thing I have READ in FWW, respected books and instruction manuals says that the higher the blade the easier the cut is on the blade and motor, this is obvious. However, splintering and tear out on the bottom side are worse, especially on veneered material. Lowering the blade decreases the tearout because the arc of the teeth becomes more horazontal than vertical at the exit point, however burning becomes more of a problem if feed rates can't be kept high enough. My experience, especially with plywood, is that this is very true.
As far as safety. I dont see how the height of the blade changes any thing. If your finger touches the blade you're screwed reguardless. An inch higher or lower is irrevelant if I'm feeding stock into the blade and don't notice that my hand is in the cut path. I have an Uni-gaurd blade gaurd so I don't see that happening, unless I start drinking again! The only exception is narrow ripping with a Beismeyer or other tall fence, where there is little space between the fence and blade.
Mike
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