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Fixed-width dado / slot cutting blades for table saw?

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Forum topic by William Shelley posted 10-19-2017 08:17 PM 539 views 0 times favorited 18 replies Add to Favorites Watch
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William Shelley

465 posts in 1281 days


10-19-2017 08:17 PM

I don’t currently own a dado stack, but I was curious as to whether anyone made 8” or 10” table saw blades with wider carbide teeth, they could be sized to fit common thicknesses of plywood, for example. I’m aware that there are several moulding heads available with a 5/8” arbor bore designed to fit on table saws, but that’s not what I’m asking about.

Lets say I want to cut a lot of 1/4” dados for (some project). My options are to make the cut in three passes using a normal table saw blade and moving the fence, or to buy a stacked dado set and fiddle with shims until I get exactly 1/4”, or ideally I’d love to have a blade with carbide teeth machined to exactly 1/4” and I just put that blade on the saw and go to town.

-- Woodworking from an engineer's perspective


18 replies so far

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bndawgs

28 posts in 394 days


#1 posted 10-19-2017 08:50 PM

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bndawgs

28 posts in 394 days


#2 posted 10-19-2017 08:51 PM

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William Shelley

465 posts in 1281 days


#3 posted 10-19-2017 08:59 PM

Ah, great. I guess my mistake was not searching for “box joint blade” or similar… Thanks!

-- Woodworking from an engineer's perspective

View ArtMann's profile

ArtMann

645 posts in 627 days


#4 posted 10-19-2017 09:10 PM

My dado stack (Freud) will accurately cut dadoes and grooves in increments of 1/8 inch to within a few thousandths of an inch without any shims. The shims are used when the dado or groove needs to be some odd dimension like 11/16. If you want to cut some odd width, like 5/16 or 11/32 then a dado blade with shims is the only way to do it.

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William Shelley

465 posts in 1281 days


#5 posted 10-19-2017 09:16 PM

Since I’d be looking at about $100 for a blade that will only do one or two sizes, I guess it really doesn’t make financial sense vs buying a dado stack.

I’ve used a dado cutter in other people’s shops but never had to set it up myself. Are they really that easy? I get frustrated with tedious tasks pretty easily so I’m willing to pay more to avoid them.

I was considering the Freud SD608 unit, the “Dial-A-Width” dado stack. At $250, it’s definitely not inexpensive. But maybe it’s worth it for me. The fixed-width box joint cutters linked to, though, require even less setup (aka none), which I like.

-- Woodworking from an engineer's perspective

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soapmaker

48 posts in 1492 days


#6 posted 10-19-2017 09:20 PM

Can’t speak on the availability but there are versions in 1/2” and 9/16” and 3/16” that we use at work so they do exist. But don’t assume absolute consistency on plywood sizes. It is also a lot of mass so certain blade braking systems advise against using even solid body stack sets.

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ArtMann

645 posts in 627 days


#7 posted 10-19-2017 10:43 PM

Hold on a minute William. I may have led you wrong. The dado blades with which I am familiar will leave a tiny slit at the square corners of the cut. It is hard to describe what I mean but you should look up the description of the set you are thinking about. These are there for a purpose when cutting dadoes but may detract from the joint if you are doing box joints where the joint is a featured detail. You need to check this out before spending money.

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William Shelley

465 posts in 1281 days


#8 posted 10-20-2017 03:36 PM



Hold on a minute William. I may have led you wrong. The dado blades with which I am familiar will leave a tiny slit at the square corners of the cut. It is hard to describe what I mean but you should look up the description of the set you are thinking about. These are there for a purpose when cutting dadoes but may detract from the joint if you are doing box joints where the joint is a featured detail. You need to check this out before spending money.

- ArtMann

Is this because the blades on the outside of the dado stack have alternating top bevel (ATB) teeth?

-- Woodworking from an engineer's perspective

View Loren's profile

Loren

9549 posts in 3459 days


#9 posted 10-20-2017 05:00 PM

http://www.bladesllc.com/KC-sc-tablesaw-cutters.html

I think they may have been more widely available
in the past. They may still be sold in Europe
where stack dados aren’t permitted. I have seen
used ones on ebay.

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the_other_ken

28 posts in 2787 days


#10 posted 10-20-2017 06:01 PM

Not change the subject, but where do you find plywood that is exactly 1/4” thick. The last stuff that I bought was on 3/16” thick and my dado blade only does 1/4” and wider. I need to used a flat top rip blade and do two passes moving the blade over 11/16” for the second pass. It’s not that much work if you do the first cut on all the boards and them move the fence and do the second cut on all the boards.

For thicker plywood, you can get a dado set with a 3/32” wide insert so you can do 15/32” or 23/32” to fit the thicker plywood with no fiddling.

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William Shelley

465 posts in 1281 days


#11 posted 10-20-2017 07:13 PM



Not change the subject, but where do you find plywood that is exactly 1/4” thick. The last stuff that I bought was on 3/16” thick and my dado blade only does 1/4” and wider. I need to used a flat top rip blade and do two passes moving the blade over 11/16” for the second pass. It s not that much work if you do the first cut on all the boards and them move the fence and do the second cut on all the boards.

For thicker plywood, you can get a dado set with a 3/32” wide insert so you can do 15/32” or 23/32” to fit the thicker plywood with no fiddling.

- theotherken

There’s a lot of variation in US plywood thickness even for the same type and grade from different vendors, or even different lots.

I think baltic birch should be quite a bit more consistent though. Same, hopefully, with ApplePly. Part of what you’re paying extra for is the higher quality of the product e.g. no visible knots, minimal footballs, and consistent thickness and panel sizes.

My 1/2” router bit set from Yonico came with straight cutters for making dados with a router to accept the common 1/32-undersize plywood thicknesses, but I haven’t used them yet.

-- Woodworking from an engineer's perspective

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Svdharma

6 posts in 32 days


#12 posted 10-20-2017 07:45 PM

Baltic birch tends to be pretty consistent but often the edges of the sheet are a few thou thinner than the rest. They have a dado set in the shared shop I work in. First time using it I set it up as per the manual, made one test cut, measured the cut with a pair of calipers, made one shim adjustment, and the second cut was dead nuts. If you use a pair of calipers and make the stack ~0.003” wider than the board that fits into it it’ll take about 5 minutes to set up.

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ArtMann

645 posts in 627 days


#13 posted 10-20-2017 07:45 PM


Is this because the blades on the outside of the dado stack have alternating top bevel (ATB) teeth?
- William Shelley

No. The teeth are flat ground except for one tiny point. These are there to prevent dado cuts from blowing out as the blade exits a through dado. Here is a diagram I found. The red arrow on the left shows the tiny slit. It may be inconsequential but I wanted you to know it is there. I only noticed it when I used a wide stack to cut tenons using multiple passes. You can see little lines on the cheeks of the tenon.

View splintergroup's profile

splintergroup

1627 posts in 1034 days


#14 posted 10-20-2017 07:48 PM

I use the Freud box joint blade set for most all my dado needs. I bought a set a few years back for around $60, but I see they now go for around $80 on Amazon.

You get two slot sizes, 3/8” and 1/4”, my blades create slots that are 0.003” over nominal. Using one blade gives a 0.208 inch slot.

The best feature in my mind is the perfectly smooth/flat bottom groves, no “bat ears” and crossgrain cuts are excellent (do use a backer board).

I usually will just take multiple passes to sneak up on a slot that is greater then the width of the blade, but If I am going to cut wide dados or long slots in a large board, I’ll revert back to the dado stack.

View knotscott's profile

knotscott

7751 posts in 3187 days


#15 posted 10-20-2017 07:50 PM


Hold on a minute William. I may have led you wrong. The dado blades with which I am familiar will leave a tiny slit at the square corners of the cut. It is hard to describe what I mean but you should look up the description of the set you are thinking about. These are there for a purpose when cutting dadoes but may detract from the joint if you are doing box joints where the joint is a featured detail. You need to check this out before spending money.

- ArtMann

Is this because the blades on the outside of the dado stack have alternating top bevel (ATB) teeth?

- William Shelley

Yes…exactly. The better sets keep them barely noticeable, but they do exist to some degree. Without the ATB teeth, the dado sets would be much more prone to tearout on ply and other cross grain cuts.

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

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