LumberJocks

All Replies on Tablesaw Blade 101

  • Advertise with us
View Mean_Dean's profile

Tablesaw Blade 101

by Mean_Dean
posted 12-24-2009 10:56 PM


16 replies so far

View SnowyRiver's profile

SnowyRiver

51450 posts in 2225 days


#1 posted 12-24-2009 11:11 PM

If you put a straight edge from the center of the hole and out to the tooth tip, the angle of the cutting tooth in relation to the straight edge is the hook angle.

If there is a space there it is positive hook angle and if the tooth is partially behind the straight edge it is negative hook angle.

You would use a positive hook angle say 5 to 10 deg. for a table saw where you push the wood through the blade.

You would use a negative 6 deg. hook angle for a sliding mitre box or radial arm saw where the wood is held stationary and the blade is pulled through. With a positive hook angle in this application, the blade would try to climb through the wood on its own and the operator would have to actually hold the sliding arm from going too fast. This is very dangerous, having to slow down the moving blade, so a negative hook angle is a must.

-- Wayne - Plymouth MN

View Dusty56's profile

Dusty56

11684 posts in 2432 days


#2 posted 12-25-2009 02:57 AM

Well said , Snowy : ) Happy Holidays !

-- I'm absolutely positive that I couldn't be more uncertain!

View Rick  Dennington's profile

Rick Dennington

3592 posts in 1939 days


#3 posted 12-25-2009 04:52 AM

Wayne…........... you da’ man…you sounded just like a professor I had in college…positive, precise,and to the point. I like a person with all the right answers. I learned a little bit myself…....... lol lol. Thanks, Prof.

MERRY CHRISTMAS, Wayne, to you and yours.

-- " I started with nothing, and I've still got most of it left".......

View ajosephg's profile

ajosephg

1860 posts in 2305 days


#4 posted 12-25-2009 05:28 AM

Rockler’s site has “Expert” Advice, one of which is Saw Blades 101

“Hook angle affects blade operation in important ways. A blade with high positive hook angle (+20 degrees is a high hook angle) will have a very aggressive cut and a fast feed rate. A low or negative hook angle will slow the feed rate and will also inhibit the blade’s tendency to “climb” the material being cut. A blade for ripping lumber on a table saw will generally have a high hook angle, where an aggressive, fast cut is usually what you want. Radial arms saws and sliding compound miter saws, on the other hand, require a blade with a very low or negative hook angle, to inhibit overly fast feed rate, binding, and the blade’s tendency to try to “climb” the material.”

-- Joe

View Dusty56's profile

Dusty56

11684 posts in 2432 days


#5 posted 12-25-2009 05:35 AM

Joe , I believe that Snowy just said that…LOL..thanks for the link though : )

-- I'm absolutely positive that I couldn't be more uncertain!

View ajosephg's profile

ajosephg

1860 posts in 2305 days


#6 posted 12-25-2009 06:12 AM

Dusty – You’re right – I was going to add a statement that the Rockler site reinforces Snowy’s statement, but accidently hit the “Enter” button before I got to it.

-- Joe

View DaleM's profile

DaleM

923 posts in 2128 days


#7 posted 12-25-2009 06:46 AM

Which way are you talking about cutting on a sliding miter saw? The only way you can have a climb cut is if you start the cut with the saw pushed all the way in, then pull it towards you, which is the exact opposite of the way I use the saw. I may be wrong, but I thought the point of the negative hook angle was so the hooked teeth wouldn’t grab the wood and lift it off the table surface, which I’ve had happen before with a positive angle, nothing to do with a climbing cut. With a negative angle, when you are pushing, not pulling, the saw towards the wood, the saw will not have the tendency to lift the wood from the saw table.

-- Dale Manning, Carthage, NY

View bunkie's profile

bunkie

411 posts in 1891 days


#8 posted 12-25-2009 03:36 PM

In a table saw, the hook angle and blade height affect tearout on the bottom side of the workpiece. The angle at which the tooth exits the wood makes for either a chopping cut (more likely to tear out with a larger angle) or a shearing cut (less likely to tear out with a shallower angle). Negative hook angles make for shallower angles and less tearout. This is why the better dado blades (such as the Forrest) have highly negative (10 degrees or so) hook angles because a cross-cut dado is perfect storm with respect to tearout.

-- Altruism is, ultimately, self-serving

View knotscott's profile

knotscott

5601 posts in 2120 days


#9 posted 12-25-2009 10:55 PM

Always a tradeoff. Steeper hook angle makes a faster more aggressive cut with higher tearout tendencies, while a negative hook has less tearout, requires more feedpressure, and thus can have a bit more tendency to burn. A low to negative hook is recommended for SCMS and a RAS.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View Mean_Dean's profile

Mean_Dean

1778 posts in 1892 days


#10 posted 12-27-2009 09:01 PM

Ok, this is great information!

So, I use a blade with a positive hook angle on the tablesaw, and one with a negative hook angle on the miter saw.

Next subject: Thin kerf or full kerf blade? Seems to me that the woodworking magazine’s recommendations have been skewing toward thin kerf.

-- Dean

View knotscott's profile

knotscott

5601 posts in 2120 days


#11 posted 12-27-2009 11:02 PM

It’s not necessary to use a negative hook on a straight miter saw, but is highly recommended for a sliding miter saw or a RAS.

Like many things, kerf width is a matter of choice, with pros and cons each way. Your saw and what you cut most should really be considerations in that decision though.

From my blog on blades:
”...Which kerf width to choose can be as easy as following manufacturer’s recommendations of using thin kerf blades for saws under 3hp (ie: most compact, jobsite, contractor, or hybrid saws fall in the 1hp to 2hp range), and full kerf blades for saws with motors 3hp and up (ie: industrial cabinet saws), but that’s where the simplicity ends and the debates begin. As with many choices, it’ll boil down to a matter of preference and your particular situation, but I’ll try to explain the logic of both philosophies. To some folks, it’s just a matter of the math being simpler with a 1/8” blade than a 3/32” blade. It can also be a matter of not knowing any better, or what was available on sale at the time of purchase. Both kerf widths will work with most saws, but note that changing kerf width can skew the zero reference on the measuring tape of a left tilt saw, so you’ll need to address that if you change kerf widths. Even though the width differences appear very small, a full kerf blade is typically 33% thicker than it’s TK counterpart. A wider kerf blade makes a wider cut, thus taking more wood and requiring more power to make the cut at the same speed…a similar principle to a lawn mower’s width of cut. There will also be a proportionately higher amount of sawdust with a full kerf blade, more wood consumed in the process, and even somewhat higher noise levels. Wood savings can be a consideration, though a minor one for most hobbyists. That consideration may become more significant if you handle a lot of expensive wood. You’re likely to encounter situations where a full kerf blade bogs a smaller saw more easily than a TK would, most notably in thicker materials. Slowing down the feed rate can help compensate somewhat for the additional power requirements, but slower cutting means more of a tendency to burn the wood, and less ability to cut efficiently in thick materials. Your splitter or riving knife width should also be part of the consideration. Choosing a blade that’s thinner than the splitter blade can cause the board to stop mid cut if the board binds on the splitter.

Full kerf blades tend to be more stable than their TK counterparts due to the increased steel thickness and body mass…there’s not much argument about the logic of the physics involved, but that’s far from saying that most TK’s are unstable…they’re not. There’s a fair amount of sentiment about the stability difference between the kerf widths that I believe stems from earlier versions and poor examples of thin kerf blades, or possibly using them in situations where a full kerf blade would have clearly been a better choice. Modern alloys are vastly stronger than those from even a few years ago, and modern blade design technology has improved in leaps and bounds. Modern computer aided designs, computerized equipment, and complex laser cut slots can combine to offer some extremely good thin kerf blades that will rival the cut quality and performance of the best full kerf blades in a home-shop type setting. While it’s true that TK blades in general are more prone to flexing than full kerf blades, that doesn’t mean that they’re likely to encounter those issues. After using and testing dozens of TK blades on a fair number of saws, I have yet to encounter a severe deflection or vibration issue during a routine cut with a TK blade that was caused by the blade itself. A saw with acceptable arbor runout and vibration levels should be able to spin a TK blade with similar precision as a full kerf blade. Issues with TK blades are most likely to occur if a problem already exists within the saw, such as high levels of runout, in which case the TK blade will indeed amplify that problem. Wood that deviates badly from flat and straight, or thick wood with very stiff grain patterns, such as mesquite, are also more likely to cause some blade flexing, but I’ll emphasize that “more” likely doesn’t mean “likely”. It typically requires substantial lateral pressure to cause a blade to deflect. For most common hobby uses, a good TK blade is more than adequate, and offers some significant advantages in reduced motor strain and lower feed pressure. Commercial environments and high volume hobby environments pose a different set of challenges such as complications from large quantities, heat, and power feeders, etc. Commercial saws are almost always equipped with ample motors to spin a full kerf blade without strain and are suggested for those applications. Now that I own a 3hp cabinet saw, there’s less incentive for me to buy thin kerf blades, but when I was primarily using 1-1/2 to 2hp contractor or hybrid saws, the TK’s were a very welcome commodity. With a good 24 tooth TK ripper there was nothing my smaller saws couldn’t handle with relative ease. While the same saws would cut the same wood with a good 24 tooth full kerf blade, the difference in motor strain, bogging, and feed rate was easily noticeable. The lower feed pressure is analogous to waxing your saw’s table top to reduce friction. It’s not just about cutting speed, it’s about ease of feeding and increased control, which is safer. With flat straight stock, cut quality is roughly equivalent between a high quality TK blade and a comparable high quality full kerf blade…it’s difficult to discern the differences in cut quality, which is additional evidence of the equality between the two kerf widths. A good TK blade can extend the life of a smaller motor by posing less strain. Ultimately the decision is yours to make, and should take into account what you cut most and what saw you have.

Many blade manufacturers recommend the use of blade stabilizers, dampeners, or stiffeners with their blades. Especially with thin kerf blades, but many make the same recommendation for full kerf blades too. From a technical perspective, it’s more right than wrong to make that recommendation. Not much harm in the recommendation, and there’s some possible benefit for both buyer and seller, so why not? First off, be aware that you give up some cutting height capacity with a disk installed. The larger the diameter of the stiffener, the less height capacity that’s available. Secondly, my experience has been that there’s no noticeable difference with or without them when using good blades on a good saw. A high quality modern blade mounted on a properly running table saw while cutting flat straight stock shouldn’t need stabilizers. I’ve read far more responses on internet forums that agreed with my view than opposed it, but as always, there are some exceptions. I vote to save your money and take your spouse (or “significant other”) or lunch with the money saved. If it turns out that you’ve got a runout problem with your blade, then by all means, get yourself a stabilizer to help, but note that it’s usually a $20 band-aid for another problem, and not a cure….”

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View Mean_Dean's profile

Mean_Dean

1778 posts in 1892 days


#12 posted 12-30-2009 03:42 AM

Knotscott, great information! Seems like you’ve really researched the subject!

Ok, next subject: For general purpose sawing, is a combination blade good enough, or should one get both a dedicated rip blade and dedicated crosscut blade?

-- Dean

View Mean_Dean's profile

Mean_Dean

1778 posts in 1892 days


#13 posted 01-02-2010 08:18 PM

Ok, seems like interest in this topic has waned.

Thanks everyone for your input—I learned a lot! Happy sawing, and Happy New Year!

-- Dean

View knotscott's profile

knotscott

5601 posts in 2120 days


#14 posted 01-02-2010 09:09 PM

_”Ok, next subject: For general purpose sawing, is a combination blade good enough, or should one get both a dedicated rip blade and dedicated crosscut blade?”

Also from my blog on blades:

Whether to choose separate task specific blades or one good general purpose/combo blade is a matter of preference, with merit to each philosophy. A decent purebred 60-80 tooth crosscut blade will certainly make “cleaner” crosscuts than a 30, 40 or 50 tooth general purpose blade of comparable quality. Inversely, a 24 tooth bulk ripper will certainly be more efficient at ripping thick material than the general purpose (GP) style blade. The key to “better” depends on how you define that term. Better performance in one aspect of cutting doesn’t necessarily mean it’s a better choice overall. There’s never a “free lunch”. Every design parameter has pros and cans, and any blade that excels in any specific region, will certainly have weaknesses in another. Consider both sides of the equation before making a decision. Taking the approach of using task specific blades requires owning at least two blades that each excel in a limited operating region, and are typically unacceptable for tasks outside of their intended scope. They also require blade changes for each different task for optimum results. Two task-specific blades (typically a 24T ripper and a 60T or 80T crosscutter) will generally stay sharp longer than a single general purpose blade because they share the work load, but will cost more upfront and will also cost more to re-sharpen when the time comes. A general purpose blade will neither rip as efficiently as a true rip blade nor crosscut as cleanly as a dedicated crosscut blade, but you may find that it’s more than acceptable at doing both tasks for most situations. A valid argument in favor of using one high quality general purpose blade is that the GP blade leaves a cleaner edge than the rip blade, crosscuts faster than a crosscut blade, and does so with the convenience and cost of using one blade. Most good general purpose blades will leave a glue ready edge, which is often as good as it needs to be. If you happen to do a lot of specialty cutting of fine veneered plywoods, veneers, melamine, MDF, plastics, etc., a blade made specifically for these materials is definitely recommended. If you tend to rip very thick dense materials regularly, then a dedicated ripping blade is a wise choice for you right from the start. Sooner a later a decent general purpose blade will be useful, so it’s always a reasonable starting point IMO, even if you pursue separates later.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View Mean_Dean's profile

Mean_Dean

1778 posts in 1892 days


#15 posted 01-03-2010 01:24 AM

Thanks again, Scott!

So, sounds like a general purpose blade, 40-50 TPI is going to be the best for most jobs, with a dedicated rip blade the blade to use when doing heavy duty ripping.

-- Dean

View knotscott's profile

knotscott

5601 posts in 2120 days


#16 posted 01-03-2010 04:05 AM

You’re welcome…yep, a good quality GP blade should do fine the vast majority of the time. A bulk ripper is always handy to have around. What saw do you have?

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase