How to get flat bottomed dados with a BT3?

[Nil]

All,

I'm using a BT3000 and an Oshlun 8-inch set of dado blades (http://www.amazon.com/Oshlun-SDS-084...5929709&sr=8-1). For some reason I don't get a flat bottomed dado. I'm using the two outside blades (oriented correctly) and two chippers in between them. I can see a significant (~1/2 mm) difference in height between the depth of cut between each of the 4 blades. What am I doing wrong? Thanks.

[LCHIEN]

All,

I'm using a BT3000 and an Oshlun 8-inch set of dado blades (http://www.amazon.com/Oshlun-SDS-084...5929709&sr=8-1). For some reason I don't get a flat bottomed dado. I'm using the two outside blades (oriented correctly) and two chippers in between them. I can see a significant (~1/2 mm) difference in height between the depth of cut between each of the 4 blades. What am I doing wrong? Thanks.

more than likely you have some of the plates sitting on the threaded part of the arbor.

With the 8" dado, you can't put them on without leaving the 1/4" spacer on the arbor. You can take all the spacers off with a 6" dado.
Since the threaded part of the arbor is a bit smaller than the straight part opf the arbor the blades sit about .020 low and cut deeper.

The solution is to get 6" dados if you want to cut full width or use the 8" dado only up to about 5/8" wide.

All about this in my FaQ (see sig line)

[Nil]

Ah, yes, you're correct I did have to put part of the blade on the threaded part. I *assumed* that the threaded part was the same diameter as the rest of the rod. Thanks!

[LCHIEN]

of course, all that presumes you have a quality dado set with all the chippers and outer blades being perfectly matched in diameter... if those are off nothing can make a flatt bottomed dado short of those flat bottom clean out router bits with bearings.

Anyway i think 1/2mm is approx .020 so that's probably the threads.

[Mr__Bill]

Wrap the threaded part that the blade sits on with Teflon tape until you get a snug fit. That may solve the problem.


Bill

[LCHIEN]

Wrap the threaded part that the blade sits on with Teflon tape until you get a snug fit. That may solve the problem.


Bill

you have to be careful how you wrap it so you don't build up the straight part and don't keep the nut from threading on fully and spinning the stack.

And BTW, the OP must have had problems putting/fitting the outer blade washer on... did'ya leave it off? Did you feel comfortable doing that? I didn't.

[dbhost]

FWIW, you are using the wrong dado stack on that saw. The manual calls for a 6" dado like the Oshlun SDS-0630

[eezlock]

flat bottomed dados on a BT3?

I don't have that brand of dado blade, but do have a set from Horrible Freight
that works well on my Bt3100 and I don''t use any teflon tape on mine. I don't think using teflon tape is the answer... never heard of such a thing being used on a saw arbor for any reason! I think you should check and make sure that the arbor washers are not interfering with the dado set before trying this type of "solution". Make sure you are installing the dado set as per the instructions that came with it, before using the teflon tape method, I feel that you may be setting yourself up for future problems or a mishap!

[phi1l]

I don't think using teflon tape is the answer...

Of course not!!! Everyone knows you should use duck tape

[Mr__Bill]

Of course not!!! Everyone knows you should use duck tape

Oh, what was I thinking, of course!


Bill
beer, duck tape and WD40; proof that there is a god...

[cabinetman]

You might find using a router and a straight bit (AKA mortising bit) will give more predictable dadoes, with very flat clean bottoms.
.

[SARGE..g-47]

I sold a dado set about 5 years ago for the very reason listed here. I got a flat bottom with one after making a pass or two down the gullet with a medium shoulder plane. A router with straight bit and a 20 minute to build T square jig elminates the fuss. If I have 1/4" or 3/8" dadoes to cut.. one pass with a Frued Box Joint cutter set leaves flat bottoms and extremely smooth sides as the teeth are flat ground on those two blades.

[dbhost]

You might find using a router and a straight bit (AKA mortising bit) will give more predictable dadoes, with very flat clean bottoms.
.

That has NOT been my experience... I tend to end up with edge guides moving in the middle of a dado using the router method...

[cabinetman]

That has NOT been my experience... I tend to end up with edge guides moving in the middle of a dado using the router method...

What you use, and how you set it up may be the problem. You can make a jig like this easily.
.

[WoodTherapist]

Nice jig, cabinetman!