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Using a single (outer) dado blade

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Forum topic by Wood_Scraps posted 10-22-2021 05:45 AM 748 views 0 times favorited 41 replies Add to Favorites Watch
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Wood_Scraps

203 posts in 303 days


10-22-2021 05:45 AM

Topic tags/keywords: custom insert dado blade 3d printing zero clearance

Title pretty much says it all. I’m not interested in concerns over cut quality. Simply whether there are any safety risks in using only one of the outer blades from a dado set.

To answer your, why the heck would you even want to do that question, here’s the deal. I designed a throat plate that accepts interchangeable MDF inserts. Which allows you to use one single primary plate for all your ZCI insert needs. 90 degrees, bevels, dados, this plate will accommodate them all.

The only “issue” is making the initial zero clearance cuts in each new interchangeable insert. I’d assume anyone who’s made an MDF insert knows that this is something you need to solution for. Which often means just tossing a blade from your handheld circular saw on your table saw.

The only issue is that for those of us who use full kerf blades, a circular saw blade isn’t going to cut a wide enough kerf for that initial clearance. Hence my interest in using a dado blade for this purpose. As my set’s outer blades are the standard 1/8” kerf.

Full disclosure, I did try this. Even though the manual said not to run a single blade. I wore my standard PPE and threw on my level 4 plate carrier for good measure. Nothing bad happened. Shocking, right? I’m just wondering if someone can speak to an actual risk that I’m not understanding.

On a somewhat related note, has anyone ever run their dado set with their saw beveled at 45 degrees? My interest in this is also tied to making these inserts. As cutting the 45 degree inserts requires quite a bit more work to get enough clearance for me to be able to throw my 10” blade on.

And, on a final note. If someone knows of a non-dado full kerf blade in the 6 – 8 inch diameter range. I’m all ears. As, even if I can use the dado blade, it may result in that particular outer blade wearing much faster than the rest of the stack.

If anyone’s interested, the picture is a few of my inserts that I’ve 3d printed for reference.


41 replies so far

View sunnybob's profile

sunnybob

55 posts in 50 days


#1 posted 10-22-2021 07:37 AM

A guess on the safety issue is if you had a single blade on while using a full width throat plate. The side gap could catch the wood and throw it at you.

I have often made zero clearance inserts by just putting a blank piece of wood in the table and very slowly raising the blade through it, while having a large heavy scrap piece held down on top to stop it lifting and flying.

View Fred Hargis's profile

Fred Hargis

7296 posts in 3778 days


#2 posted 10-22-2021 10:32 AM

What you did is not unheard of, and if the insert was secured (fence parked on the edge to hold it down) I think it was safe. I remember sometime in the past tilting my dado blade, but I don’t remember why or what i did for an insert.

-- Our village hasn't lost it's idiot, he was elected to congress.

View bigblockyeti's profile

bigblockyeti

7749 posts in 3005 days


#3 posted 10-22-2021 10:40 AM

I typically use a full 10” blade, usually the exact one I’m trying to cut a new zero clearance insert for. It’s proven safe so far but probably doesn’t look like it.

-- "Lack of effort will result in failure with amazing predictability" - Me

View Robert's profile

Robert

4786 posts in 2765 days


#4 posted 10-22-2021 11:47 AM

Explain what the “issue” is with MDF please. I have the Colliflower plate in my saw with changeable MDF inserts there’s no issue.

I can’t remember ever running a dado at an angle, but that doesn’t mean much

-- Everything is a prototype thats why its one of a kind!!

View tvrgeek's profile

tvrgeek

2299 posts in 2934 days


#5 posted 10-22-2021 12:11 PM

Don’t see any safety reason against it. Many do. Just clamp it down. ( Wedge under fence, big weight)

I used a router table to do the clearance cut on my last batch.
Like many saws, my blade full down is only about 1/8 from the table surface, so can’t use a full blade for the cut.

View tvrgeek's profile

tvrgeek

2299 posts in 2934 days


#6 posted 10-22-2021 12:11 PM

Don’t see any safety reason against it. Many do. Just clamp it down. ( Wedge under fence, big weight)

I used a router table to do the clearance cut on my last batch.
Like many saws, my blade full down is only about 1/8 from the table surface, so can’t use a full blade for the cut.

View HokieKen's profile

HokieKen

19862 posts in 2423 days


#7 posted 10-22-2021 12:23 PM

I do the same as Yeti does – put the 10” blade in, use a batten to hold the insert in place so it won’t lift out, and raise the blade slowly to make the kerf.

Based on your question, I assume your MDF inserts are too thick and you can’t lower the blade far enough to clear? If that’s the case, I have two possible suggestions:
  1. Lower the blade all the way and put the front of the insert in the table holding the back up. Slowly lower the back end of the insert onto the running blade and into place. Then you can raise the blade the rest of the way.
  2. Use a router to cut a groove where the blade will be so that the thickness left for the kerf is only as wide as necessary to clear your fully retracted blade.

All that aside though, to answer your question directly, I see no issue (safety or otherwise) in using one of your dado blades by itself. I’ve done so to make finger joints several times with no problems.

Also wanted to say that I like your design :-) I have been meaning to make myself an Aluminum insert that accepts sacrificial inserts like yours for quite a while now. Last time I made inserts from MDF I made a batch of 5 and I recently used the last one so I’ll probably force myself to do it in the not-too-distant future :-) Curious though why you didn’t make the printed portion solid around the outside and just put the mdf in the center? Seems like it would be more stable that way. At least in the design in my mind.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View jkm312's profile

jkm312

113 posts in 687 days


#8 posted 10-22-2021 12:24 PM

Dado blades at a 45 degree angle

If you are talking about running a single outer blade at an angle for a ZCI cut out I don’t see it as any different than what you did at a straight 90. Just go slow and easy.

If you are thinking of running a dado stack at an angle, then most likely you will get a lot of deflection in the blades/chippers on the outside of the arbor in a deep cut. If you loose your clearance, instant disaster. For me, I would not do that.

Back in the day when beveled contrasting formica edged counters were in style, I built a jig to hold the router and straight bit to cut that groove in the counter top edge.

View controlfreak's profile

controlfreak

3055 posts in 886 days


#9 posted 10-22-2021 01:03 PM

A Dado stack at 45 Deg. sounds as wrong as it likely is. I would never attempt this.

View Wood_Scraps's profile

Wood_Scraps

203 posts in 303 days


#10 posted 10-22-2021 03:21 PM



Explain what the “issue” is with MDF please. I have the Colliflower plate in my saw with changeable MDF inserts there’s no issue.

I can’t remember ever running a dado at an angle, but that doesn’t mean much

- Robert

As some others have stated, my saw Delta 725 T2 only lowers a standard 10” blade around 1/8” (maybe even less) below the table. So, with a fresh MDF insert, there isn’t enough clearance to seat the throat plate. Hence why I have to throw a smaller blade on the saw to make my initial zero clearance cut.

I guess that every saw is going to be different. So, while I know it’s somewhat of a common “challenge”, it’s definitely possible others have never run into this when making their own inserts.

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Wood_Scraps

203 posts in 303 days


#11 posted 10-22-2021 03:24 PM



Don t see any safety reason against it. Many do. Just clamp it down. ( Wedge under fence, big weight)

I used a router table to do the clearance cut on my last batch.
Like many saws, my blade full down is only about 1/8 from the table surface, so can t use a full blade for the cut.

- tvrgeek

That’s what I was thinking. So long as you do everything else to secure the plate when making the cut, I couldn’t think of any danger in using a single dado blade. It’s just that the manual says not to. Couldn’t rationalize why though, other than legal CYA. I mean, in a practical sense, the outer blades are just normal blades.

I would probably use a router as well, but still need to build out my router table. So I have to find a different solution in the interim,

View Wood_Scraps's profile

Wood_Scraps

203 posts in 303 days


#12 posted 10-22-2021 03:33 PM



I do the same as Yeti does – put the 10” blade in, use a batten to hold the insert in place so it won t lift out, and raise the blade slowly to make the kerf.

Based on your question, I assume your MDF inserts are too thick and you can t lower the blade far enough to clear? If that s the case, I have two possible suggestions:
  1. Lower the blade all the way and put the front of the insert in the table holding the back up. Slowly lower the back end of the insert onto the running blade and into place. Then you can raise the blade the rest of the way.
  2. Use a router to cut a groove where the blade will be so that the thickness left for the kerf is only as wide as necessary to clear your fully retracted blade.

All that aside though, to answer your question directly, I see no issue (safety or otherwise) in using one of your dado blades by itself. I ve done so to make finger joints several times with no problems.

Also wanted to say that I like your design :-) I have been meaning to make myself an Aluminum insert that accepts sacrificial inserts like yours for quite a while now. Last time I made inserts from MDF I made a batch of 5 and I recently used the last one so I ll probably force myself to do it in the not-too-distant future :-) Curious though why you didn t make the printed portion solid around the outside and just put the mdf in the center? Seems like it would be more stable that way. At least in the design in my mind.

- HokieKen

Yep, you’re correct. There is basically zero room to accommodate a plate of any thickness that doesn’t already have the kerf clearance cut.

This thing was really fun to design. Had to teach myself CAD, which was pretty frustrating at first. But now I’m pretty comfortable with it and have designed all sorts of add-ons for my saw. I probably could have found a way to make the whole perimeter of it solid. And, it actually is connected in the front at the base of the plate. T

he main reason it’s open at the front is because it makes it super easy to change out the inserts. While also allowing for really solid retention. The plate is actually pretty rigid. A design with MDF only in the center would have been much more complex. Or at least for my current CAD skill set.

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Wood_Scraps

203 posts in 303 days


#13 posted 10-22-2021 03:39 PM



Dado blades at a 45 degree angle

If you are talking about running a single outer blade at an angle for a ZCI cut out I don t see it as any different than what you did at a straight 90. Just go slow and easy.

If you are thinking of running a dado stack at an angle, then most likely you will get a lot of deflection in the blades/chippers on the outside of the arbor in a deep cut. If you loose your clearance, instant disaster. For me, I would not do that.

Back in the day when beveled contrasting formica edged counters were in style, I built a jig to hold the router and straight bit to cut that groove in the counter top edge.

- jkm312

Yeah. I ran a single dado blade at 45. But to create enough clearance for my 10” blade, I need to remove more material than just the one cut at 45 with the smaller blade. What I did for now was decrease the bevel angle from 45 to 15 degrees, in 5 degree increments. Only doing a full through cut on the initial 45 degree.

It works well. Just is time consuming. Because I don’t adjust the bevel as the saw is spinning (didn’t seem like a good idea). So I make my first cut. Stop the saw. Adjust it 5 degrees. Make the next cut. Rinse, repeat.

I am thinking a router jig would be the better option. But I wanted to figure out how to do it with just the TS. As I’ll be selling some of these and want for buyers to be able to make additional inserts without the need for other tools.

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Wood_Scraps

203 posts in 303 days


#14 posted 10-22-2021 03:39 PM



A Dado stack at 45 Deg. sounds as wrong as it likely is. I would never attempt this.

- controlfreak

I agree. But figured why not ask while I was at it :)

View LeeRoyMan's profile

LeeRoyMan

2251 posts in 1011 days


#15 posted 10-23-2021 03:25 AM

A Dado stack at 45 Deg. sounds as wrong as it likely is. I would never attempt this.

- controlfreak

I agree. But figured why not ask while I was at it :)

- Wood_Scraps


In my opinion, (which doesn’t mean much),
I have, and didn’t find it any different.
Obviously it’s removing more material so you have to use it as for what it is.

As far as using only the outer blade, It doesn’t know it’s all by itself.
I’ll show you my solution to your problem, but it will have to be Sunday, if I remember.

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