Zero Clearance Insert - What did I do wrong?

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Forum topic by JerryL posted 05-18-2007 06:14 PM 2202 views 0 times favorited 10 replies Add to Favorites Watch
View JerryL's profile


45 posts in 4223 days

05-18-2007 06:14 PM

Topic tags/keywords: dado zero clearance clarence

Here’s the story. I’ve been watching the Woodworking Online videos. The one on dadoes was kind of fun. They suggested making zero clearance inserts for various sized dado stacks. Here’s what I did:

Clearance Clarence:

Sorry for the blurry pic.

Here's the back:

I made this out of some dimensional oak that was fit with my stationary sander and some tape on one end to get the friction fit nice and tight.

I clamped the insert into the saw and began to raise the blade. I did this very slowly. What ended up happening is that the dado stack burned through the insert rather than cutting through it. I ended up with this:

Lots of gunk on the teeth and a missing tooth on a chipper! To be honest I had just used this stack to cut some lap joints on some scrap 2x4s for a tool cart so I don't know if that operation broke the tooth or if it was the burn through the insert.

So, what did I do wrong? I think I might have gone too slow on the blade height. Would I have been better off going a little faster in order to try and get chips and not burn? And, is that blade shot or can I clean off the teeth and just move on? I'm pretty sure I don't want to use the broken chipper but I'm still on the fence about that one.

The dado stack is less than a week old. It's a Grizzly 8" that was just replaced by Grizzly becuase of other broken teeth after I had a plastic push stick contact the blade - yes it was a stupid mistake/accident on my part that taught me a lot. The thing is, at $50 it seems like a bargen, and I really, really want this setup to work. The cuts could be smoother but I'm willing to live with it if the thing would just stay together.


-- Jerry L.

10 replies so far

View USCJeff's profile


1064 posts in 4244 days

#1 posted 05-18-2007 10:01 PM

I’m a little suprised by this. There are plenty of Grizzly bashers that will put the blame on quality. Maybe I’m lucky, in that I have never had an issue with them. It’s possible the lap joint operation hurt the blade, but it shouldn’t. DO NOT use the broken chipper. If a tooth came off, you have to assume another one is likely. Spinning blade and flying carbide is not a good thing. The burn is probably a result of not raising the blade fast enough. I generally raise the blade quickly, but smoothly. I put a backer board on the insert so that the quick rise doesn’t chip out. Another point, I would suggest using plywood or another stable material so that the wood does not move with the seasons. A loose insert due to the fibers contracting could be dangerous.

-- Jeff, South Carolina

View mot's profile


4918 posts in 4212 days

#2 posted 05-18-2007 10:22 PM

The only thing that would make it burn like that is if you have the cutters pointed the wrong way, or chippers in backwards. There is no reason it didn’t just cut through it because the blade just thinks it’s cutting a dado. It doesnt care that the blade is moving through the piece instead of the piece through the blade. Speed shouldn’t have mattered at all as it just hogs out the material at whatever speed you go through it.

-- You can discover more about a person in an hour of play than in a year of conversation. (Plato)

View USCJeff's profile


1064 posts in 4244 days

#3 posted 05-19-2007 05:47 AM

I should clarify based on Mot’s post. The speed shouldn’t matter as long as the parts are sharp and aren’t left in the same spot too long. If you raise it very slow, the wood that is parallel to the cut could be getting rub instead of cut. This could cause burn marks.

-- Jeff, South Carolina

View woodspar's profile


710 posts in 4275 days

#4 posted 05-19-2007 05:58 AM

Yeah, I had a slot cutter in my router table worked fine. I put a different slot cutter (different brand) into fixed base router and started practicing cutting biscuit slots. Burn mark. Again, burn mark. Was that smoke? What’s wrong with this brand? Again, burn mark, smoke. Cheap junk! Slow it down? speed it up? burns. DOH! slot cutter in backwards! PILOT ERROR! Turn it around – gee it works great!

I don’t know – It looks like all of the teeth are going the right way in your photos. But Tom is right, the blade should come right up through the wood – you should not have to baby it.

What HP is the motor? Is the saw on a dedicated electrical circuit – Are you browning out the saw?

Are you sure that the arbor nut is tight enough?

Anyway, good luck.

-- John

View Dollarbill's profile


91 posts in 4313 days

#5 posted 05-19-2007 05:05 PM

I agree with Mot.

I started off with a Delta daddo blade ($89) and then I broke down and bought a Forrest ($259). The cut is great and I feel safer bucause I know that the Forrest is super quality and probably less likley to throw off a tooth.


$259 + $89 = more than $259 (I will learn some day).

-- Make Dust

View oscorner's profile


4563 posts in 4486 days

#6 posted 05-20-2007 04:47 AM

I never had a burning problem when making my zero clearance inserts. The main thing is to clamp a stiff board across the insert before trying to cut through, this way the insert doesn’t bow and cause problems when the blade starts putting pressure from underneath.

-- Jesus is Lord!

View JerryL's profile


45 posts in 4223 days

#7 posted 05-21-2007 04:31 AM


Thanks for the info. I didn’t abandon this thread, I’ve just been very buisy. I checked the blade and everything was pointing the right way. The sides of the insert didn’t have any burn marks so I’m convinced that I just didn’t raise the blade fast enough. Other dado cuts I’ve made on plywood, oak lumber, etc. had no burn at all. I will be emailing Grizzly about the broken tooth. I expect them to replace the dado set. I’ll update this thread with any progress.

I do think I’ll try to make a 1/2” insert just before I se d the blade back to see if it’s the speed. An yes, I had the insert clamped in using a 2×4.

-- Jerry L.

View USCJeff's profile


1064 posts in 4244 days

#8 posted 05-21-2007 05:57 AM

Couple things:

First, I saw that Grizzly had their dado sets on sale for summer. The pricing looked attractive as always! I’ve used a straight bit in a router for my dado’s as a result of not wanting to spend a lot on a decent dado set.

Second, I don’t want to change the topic of the thread, but I do have a related question about zero clearance inserts. How does everyone keep their insert snug in the saw’s opening? I’m worried that the back of my saw blade could potentially flip the insert at me if enough lateral pressure is forced on the blade due to binding or something. Commercial inserts have a variety of set screws or springs to secure them. Is this a valid concern? I’m thinkng double sided tape. What do you all think?

-- Jeff, South Carolina

View BillHoyer's profile


5 posts in 4202 days

#9 posted 05-21-2007 06:32 AM

A little tape on the edge of your insert would work fine. Must keep the tape hidden and under both the insert and table surface; plus the insert’s entire surface must remain exactly at the surface level of your table top. You must not have any edges of the insert or table top show any exposed edges, or wood will be caught on the edge and you’d set yourself up for a kickback.

P.S. If you’ve got an insert for a dado, you are likely going to have more than one dado insert, because of the varity of dado width’s, plus the depth of your cut. I make my inserts out of oak (or some other hardwood). Inserts are quick to make-up, so don’t purchase them. Also, you might consider making wooden inserts for your band saw and router table.

Cheers, Bill

-- Bill, Oregon

View JerryL's profile


45 posts in 4223 days

#10 posted 05-23-2007 04:12 PM

Just a quick update…

I emailed Grizzly and they are replacing the dado set. I expect to have the replacement by next week.

-- Jerry L.

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