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What is the point of crosscut blades?

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Forum topic by Carloz posted 10-30-2017 11:25 PM 474 views 0 times favorited 10 replies Add to Favorites Watch
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Carloz

976 posts in 429 days


10-30-2017 11:25 PM

This is concerning only hardwood crosscutting, not plywood, laminate etc.
I do not see any difference in quality when crosscutting boards with 60 teeth crosscut blade versus 24 teeth rip blade, Moreover a general purpose 40 teethe blade. But my blades are sharp. So why do I need one ?


10 replies so far

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Rick_M

10630 posts in 2217 days


#1 posted 10-30-2017 11:32 PM

If you are happy with what you have, then you don’t need it.
But to answer the main question (lest I get called out for not doing so), it’s for better quality crosscuts, especially in chip prone woods or sheet goods.

-- http://thewoodknack.blogspot.com/

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MrUnix

6002 posts in 2036 days


#2 posted 10-30-2017 11:41 PM

From Freud:

• The number of teeth cutting the wood simultaneously must be between 3 or 4 for ripping and ideally 5 to 7 for crosscutting. With less than 3 teeth cutting the sawblade begins to vibrate leading to an uneven cut. If you want to cut work pieces with increased thicknesses (T-fig.21), but wish to maintain the same diameter saw blade, then use a blade with less teeth. If instead you want to cut work pieces with a reduced thickness, but also maintain the same diameter saw blade, then use a blade with more teeth.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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Rich

1981 posts in 427 days


#3 posted 10-31-2017 01:27 AM


From Freud:

Cheers,
Brad

- MrUnix

I’d never seen those formulas. A couple of thoughts come to mind. In formula a, they’re using sqrt(2) times the thickness to determine the length of the cut inside the board. That means they’re assuming a 45º angle of cut. Raising or lowering the blade affects that. I’m sure it’s a good approximation though. If course, it’s the formula for ripping — to calculate crosscut pitch, the denominator would be 5 or 6.

In formula c, what the heck is S?

-- No matter how much you push the envelope, it'll still be stationery.

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bondogaposis

4478 posts in 2188 days


#4 posted 10-31-2017 01:41 AM

I do not see any difference in quality when crosscutting boards with 60 teeth crosscut blade versus 24 teeth rip blade

If you can’t see the difference, then I guess you don’t need a crosscut blade. I sure can, but then I use an 80 tooth crosscut, the advantage for me is that I don’t have to sand end grain, it is good to go right from the saw.

-- Bondo Gaposis

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William Shelley

479 posts in 1307 days


#5 posted 10-31-2017 01:45 AM

I noticed a huge difference in cut quality once I got the blade aligned to the miter slots better. I used a dial indicator to help me get the blade parallel to within 0.001”. Crosscuts with a sled or miter gauge are now glass-smooth.

-- Woodworking from an engineer's perspective

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MrUnix

6002 posts in 2036 days


#6 posted 10-31-2017 02:04 AM

In formula c, what the heck is S?
- Rich

I believe that is a typo… should be a “T” (thickness of workpiece).
In any event, the formulas are from another discussion and can be ignored. The graphic was included because it contained Fig. 21, which was referenced in the text, and the rest of the stuff just came along with it.

Original article is here: Correct Use of a Saw Blade from Freud

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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TheFridge

8309 posts in 1323 days


#7 posted 10-31-2017 02:31 AM

It’s a scam by the saw blade manufacturers. I’m glad you figured it out. I’m gonna go put a 2tpi scroll saw blade in and play around.

-- Shooting down the walls of heartache. Bang bang. I am. The warrior.

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Rich

1981 posts in 427 days


#8 posted 10-31-2017 03:57 AM

In my experience, a good quality blade with 40T and up will do nice crosscuts. I keep an 80T blade on my miter saw because I obviously don’t ever rip on that saw. On my table saw, I switch between a 50T combination blade for 90% of my cuts and a 28T blade for ripping thick stock and wood that’s prone to burning. For the crosscuts I do on my sled, the 50T does just fine. I never bother to put an 80T blade on for that.

-- No matter how much you push the envelope, it'll still be stationery.

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woodbutcherbynight

3645 posts in 2246 days


#9 posted 10-31-2017 04:10 AM

I follow about the same as Rich. If you want more of a visual run a scrapper across a freshly cut piece. Then look at it with light shining across the edge.

-- Live to tell the stories, they sound better that way.

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knotscott

7787 posts in 3213 days


#10 posted 10-31-2017 10:30 AM

There are several variables in play with grind types, blade parameters, wood type, wood thickness, technique, etc. You didn’t mention what brand/model your 60T crosscut blade is, but they’re not all the same. Also, some wood is far more prone to tear out than others, and benefits more from having a blade optimized for low tear out. Grading the cut is also subjective….what looks fine to you might be less acceptable to someone else.

What happens during the cut really boils down to physics. A flat top grind blade simply rips a larger splinter of wood away from the board at one time than does a steep Hi-ATB grind blade that scores the wood as it enters the cut before the bulk of the tooth reaches it, resulting in finer pieces, less tear out, etc. A crosscut blade also tends to have more teeth than a rip blade, which also tends to equate to a smoother cut.

There are times when the benefits of a good crosscut blade makes a notable difference, and times when it’s less critical and less obvious to me, but there’s no way I’m approaching an expensive piece of veneered plywood or a brittle exotic wood with an FTG grind rip blade for a critical visible cross grain cut.

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

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