Dado blade inaccuracy

[Jill Barnes]

I have a Freud S208 dado stacked blade set. Every slot I cut to nominal settings using the recommended blades and chippers are too narrow by 0.35 - 0.55mm, right across the range of slots.

eg a 1/4" slot cut with the two outside blades only, is 0.35mm too narrow. Similarly, the 1/2" slot cut with the two outside blades and two 1/8" chippers is 0.5mm too narrow.

Is this the norm for Freud dado sets, or do I have a manufacturing error?

regards,
Jill

[Tony Bilello]

Are you putting the 'bat ears' on the outside? Normally the sides with all of the Freud logo and stuff goes on the outside of the stack.

[glenn bradley]

If your outer plates are oriented correctly, I would exchange the set. As a number, the error seems small but we all know what an error of nearly 1/64" means on a dado fit ;-) The included shims are great for fine tuning but I would want to use them for that purpose. Using them for every standard width cut would be a pain. Then again, not very many cuts are "standard". My regular practice on dados that don't fall on a size that my stack does with just plates is to use a stack narrower than my desired dado and make two passes. I find this easier than fiddling with shims but that's just me. If my saw would accept the SD608, I surely would have gotten that and been done with it. Freud has a pretty outstanding record for customer service if you need help with your stack.

[Eric Roberge]

Do you have shims?

[Jamie Buxton]

I don't know your particular model, but it is not uncommon for stacked dado sets to be somewhat narrower than the nominal dimensions. The idea is that you can shim the set to make it wider, but there's no way to make it narrower. You can buy shim sets for dado blades from most blade vendors.

[Ken Fitzgerald]

I'm not so sure that's a bad thing. I'll explain why.

My Freud set came with a set of shims.

Wood today and especially plywood isn't the advertised width.

3/4" plywood doesn't measure 3/4". If your dado blade cut a true 3/4" every joint would be too large and your joints would be loose.

My Freud set cuts less than the nominal width but I have a set of shims I can use to make it the actual width of the material I'm trying to join.

[Roger Jensen]

I gave up on what the dado width was 'supposed' to be. I take it as a given some amount of shimming will be required.

One thing I found, since the shims vary in width I numbered them and keep notes on what shims I used for each batch of plywood. I usually forget one dado cut I need (ok, probably more than one), then have to setup again. If I have my notes I can go right to the correct width.

Roger

[Frank Drew]

Adding a shim or two when making up your stack can in no sense be called difficult or particularly time consuming; I'd consider it just part of doing business with dado sets. It's a good idea to keep permanent note of which blades/chippers/shims add up to which thicknesses, for future reference.

[Jill Barnes]

it is not uncommon for stacked dado sets to be somewhat narrower than the nominal dimensions. The idea is that you can shim the set to make it wider, but there's no way to make it narrower.

This makes sense. Looks like I have to get used to shimming, even though I still feel this is not as it should be for nominal sizes.

A set of shims came with it ( metric), and I have also bought a set of the Veritas plastic shims ( Imperial).

Actually, I find the shims to be very time consuming, as they tend to get stuck in the threads of the arbor shaft, and sometimes they do not fit tightly against the cutters. Also they are difficult to remove as they are such a tight fit on the arbor. Just getting a grip on them is a bit of an art :(

thanks for your comments,

regards,
Jill

[Dave Cav]

Actually, I find the shims to be very time consuming, as they tend to get stuck in the threads of the arbor shaft, and sometimes they do not fit tightly against the cutters. Also they are difficult to remove as they are such a tight fit on the arbor. Just getting a grip on them is a bit of an art :(

thanks for your comments,

regards,
Jill

Try cutting a slot in each shim the width of the arbor hole; you can then insert/remove them with a forceps or hemostat without taking the stack apart.

[Tom Esh]

...Actually, I find the shims to be very time consuming...

I rarely use them. For just a few pieces I find it much easier to make one pass a bit narrow, adjust the fence, then make a 2nd pass to final width.

[Alan Schwabacher]

I've got a little table for my set, so I just measure what I want to fit with calipers, read off which chippers I want for that size, and the difference will be the shims. For this you don't want fractions. Use decimal english or metric units and it's pretty straightforward. My Dewalt set is right on in terms of units. so I can use the table from the manual. But it was just as easy with my old dado set that did not match any sort of units, once I had made the table. (That set did not cut as nicely though.)

Magnetic shims are very nice for not falling into the threads. If you know which shims you want while assembling the stack, you just stick the shim to the blade or chipper as you put it together. I got my magnetic shims from Grizzly. You may need a thinner shim to get an exact fit sometimes.

[Don Morris]

Yes shims are a PITA, but as others have indicated, it's the cost of doing good woodworking. It seems the faster you go the behinder you get. Or to put it another way: excellence takes time.

[Ken Fitzgerald]

This makes sense. Looks like I have to get used to shimming, even though I still feel this is not as it should be for nominal sizes.


regards,
Jill

Jill,

The blade manufacturers are trying to accomodate the consumer. It's the wood manufacturers that alter the thickness of the wood.

The blade manufacturers used to make the blades to the nominal size. Then the wood manufacturers changed the thickeness of the wood. The blade manufacturers got complaints and thus they accomodated the consumer by making the blades thinner and offering the use of shims.

Wood is also dynamic. If wood is processed wet and then stored in a much dryer size for a period of time, it's moisture content can decrease and thus the nominal blade size would be ineffective.

[Eric Roberge]

What's this "takes time" thing? Is everyone running a production shop:confused:

It's woodworking folks. Take your time, use the shims and smell the sawdust. Be one with your tool...:)

I found that the older I get the more patience I have.:cool:

[Bruce Wrenn]

An easy way to determine what shims to use is to make up dado set, slightly over sized. Run a test dado, then put piece of wood into oversize dado, and see what shims will fill out the dado. Subtract these from dado set before installing it back on the saw. Usually get it in one try, unless I made dado too narrow.

[Salem Ganzhorn]

I have the same dado set. It is the first one I ever used so I am in no way experienced. But just last night I needed a 3/4" dado and using the recommended set of chippers was almost spot on .750-.751.

That being said the instructions are odd. They say to turn every other chipper 90 degrees. Well this didn't look right to me. When adding the third one it would end up contacting the first. So I spaced them out evenly.

[Alan Schaffter]

This thread is nearly identical to one about the Forrest Dado King. The answer in that case is likely the same here. One poster even contacted Forrest who said their dado set is purposely manufactured under size.

As others have said, don't expect trimmers and chippers to add up to the exact size you want without shims. You may also note you can stack a dado using shims on Monday and it will be 3/4", on Friday you can use the same combination of trimmers, chippers and shims, but torque the arbor nut a little more and it may only cut a .741 dado. The key with dados- set, test, set, test.

[Frank Drew]

Actually, I find the shims to be very time consuming, as they tend to get stuck in the threads of the arbor shaft, and sometimes they do not fit tightly against the cutters. Also they are difficult to remove as they are such a tight fit on the arbor.

Jill, shims are for spacing so don't have to fight the arbor tightly; a U-shaped cutout as Dave suggests would work fine, as would oversized holes.