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Discussion Starter #1
I want to make a 3/8 inch box joint jig for the table saw. I got out the Freud SD208S dado stack, and set it up for a 3/8 inch dado. According to the chart that came with the dado stack, the setup requires two blades and one chipper. Simple, huh?

I made two test cuts in a 3/4 x 3/4 inch piece of scrapwood for test fitting the box joint pin. I measured the resulting dados carefully with calipers, then rechecked the measurements with a Starrett blade from a combination square.

The two dados (notches) are both 23/64 inch wide.

I expected 24/64 = 3/8 inch. Yeah, the dados are 1/64 inch too narrow. Normally I would not care about 1/64 inch, but with box joints, they add up. On a 3 inch box with 8 fingers, it would add up to be 1/8 inch short. That's enough to bother me.

The simple question is:
-> What next?

Here are more questions:

Box Joint Jig Questions:
* Would you live with the 1/64 error for the ease and convenience of assembling the dado stack?
* Would you shim it to a perfect 3/8 inch instead, remembering that you must shim it every time? (I can write down the shim requirements on the jig as a reminder.)

Freud SD208S Dado Stack Questions:
* Is that normal for a Freud SD208S "8 inch Pro Dado Set"?
* Is it a metric vs. Imperial issue?
* Would you call Freud to ask about it or complain?
* Would you invoke Freud's lifetime warranty for such a petty issue?

Other Questions:
* Would you make additional test cuts with different woods to make sure it is consistent?
* Am I missing something obvious?
* Is there something else I should be doing?
* Do I have unreasonable expectations? After all, this is wood we are talking about. (It's okay. Don't hold back.)

-> Any help, advice or previous experiences would be appreciated. Thanks!


Footnote:
The dado measurements remain unchanged (within 1/128 inch) outside, inside the garage, and inside the house, taken yesterday and again this morning. To the best of my knowledge, there has been no wood movement.
 

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Did you do any investigation to determine why the blade setup was not giving the correct cut width. That is where I would start.


You say that you got out the stack. I assume that means that you have used the set before. Have you ever had a problem before?


I am guessing that the problem is most likely in your chipper. Did you measure the chipper?


Does your set include more than 1 size chipper?


You need to concentrate on how to solve the problem of why the dado set does cut the notch correctly. Not trying to come up with some kludge to make it work.



George
 

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I have an older Freud SD308 “safety dado” set, and the finished cuts never match the chart included with the set to my satisfaction. I have a set of brass shims which I always assume I’ll have to use to get the cut I want.

I also have their box joint cutter set, which makes very accurate cuts.
 

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where's my table saw?
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All dado sets needs shims .... or not.

All the dado sets I've owned or have seen on You Tube require adjusting the cut width with shims. You may get lucky on a particular width that does not require a shim or two. Shims are a pain in the neck and if you get them down in a thread that will throw off the width and damaged them when you tighten the arbor nut.




An accurate jig is just as important as the width of the dado set:
 

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OK guys.

In a dado setup it is the thickness of the bade disks that determine the width of the cut and not the width of the teeth.

My advice is to go to a hobby store and buy a sheet of brass, 0.015 thick. Cut it with scissors and put it in the dado stack. Then you'll get your perfect ¾ dado.
 

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Discussion Starter #9
(Quotes below) George
GeorgeC: Did you do any investigation to determine why the blade setup was not giving the correct cut width. That is where I would start.

TA: Okay, it makes sense to me.

My current hypothesis is that the Freud dado set is actually metric, and the printed configurations are not correct. The configurations make sense if you think of materials like Baltic Birch, which is labeled in Imperial units, but is actually slightly smaller.

GeorgeC: You say that you got out the stack. I assume that means that you have used the set before. Have you ever had a problem before?

TA: No, but I have not tried using it in a precisely measured way like this before. Before yesterday, I would choose a rough dado stack size, then make two or more passes to cut the shoulders, then the middle if necessary to "cut to fit." Another use was to cut rabbets, burying the blade in an auxiliary fence. On occasion, I simply trusted the configuration chart and somehow made it work, probably by cutting or planing other parts to fit without worrying about it.

GeorgeC: I am guessing that the problem is most likely in your chipper. Did you measure the chipper?

TA: Yes. I measured the chipper and the other blade parts for you, using a digital caliper with 1/128th resolution. Here are my measurements:

Chipper body = 1/8 inch
Outer Blade body = 3/32 inch
Carbide tip extension outside the blade body = 1/64 inch (this was difficult to measure)

If the measurements are correct, the dado stack should be:
= (2 x 3/32) + (2 x 1/64) + 1/8
= 6/32 + 1/32 + 4/32
= 11/32
= 22/64

To remind you, my measurement of the actual dado slot was 23/64, which I think is within measurement tolerances. Both measurements are short of 3/8 inch.

GeorgeC: Does your set include more than 1 size chipper?

No. All three chippers are 1/8 inch.

GeorgeC: You need to concentrate on how to solve the problem of why the dado set does cut the notch correctly. Not trying to come up with some kludge to make it work.

You're right. That's why I posted the question, but your ideas helped me determine that the configuration chart included with the dado set is not accurate. If I am correct, then shame on Freud.

I made a box joint jig before and it worked fine, but it used a standard kerf 1/8 inch blade. That's too many fingers for the trays and other things I want to build now.
 

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Discussion Starter #10 (Edited)
The Freud SD208S dado set includes shims. They are labeled in metric, with rough Imperial conversions in decimal, which makes it even more challenging to determine what you need for correctly sized dados. I made a chart and will post it below.

Freud includes five 0.1 mm shims, and one each of 0.2, 0.3, and 0.5 mm shims.

If you read the included configuration chart, shims should not be necessary for "standard" Imperial dimensions, but as I said above, the chart is wrong and misleading.

After doing the math, I needed a 0.4 mm shim, which is not included, so I added a 0.1 mm shim and a 0.3 mm shim.

-> The test cuts yielded a perfect 3/8 inch that I wanted.

I learned a lot, but shame on Freud for wasting my time. It isn't that the set is metric, it is that their charts are wrong, plain and simple. I wonder how much expensive wood has been wasted because people trusted the chart without testing cuts first?

P.S. Thank you to all for your helpful comments and valuable lessons!
 

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Discussion Starter #11
As promised, here is the shim chart that I made.

The decimal inches stamped on the shims were not very useful to me. I wanted fractions, so I computed them. Please forgive the excessive precision; it was a quick copy/paste from the calculator. I do not expect anyone else to like it, want it, or need it, but it helps me.

Key:
mm (stamped on shim) = ~ inches (stamped on shim) = inch ("exact") = ~ closest fraction (fraction in decimal)

Freud Shims:
0.1 mm = ~ 0.004 in = 0.0039370079 = ~ 1/256 (0.00390625)
0.2 mm = ~ 0.008 in = 0.0078740157 = ~ 1/128 (0.0078125)
0.3 mm = ~ 0.012 in = 0.0118110236 = ~ 3/256 (0.01171875)
~ 1/85 (0.0117647059)
0.4 mm = ~ (N/A) in = 0.0157480315 = ~ 1/64 (0.015625)
0.5 mm = ~ 0.020 in = 0.0196850394 = ~ 1/51 (0.0196078431)

Freud does not include a 0.4 mm shim in the set, but I needed the measurement. Use 0.1 mm and 0.3 mm shims in your dado stack to get 0.4 mm.
 

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where's my table saw?
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Not really .......

OK guys.

In a dado setup it is the thickness of the bade disks that determine the width of the cut and not the width of the teeth.

My advice is to go to a hobby store and buy a sheet of brass, 0.015 thick. Cut it with scissors and put it in the dado stack. Then you'll get your perfect ¾ dado.

The width of a stacked dado is determined by two things, the number of chippers and the set of the teeth in the outer blades. the outer blades are marked right and left or inside and outside and must go on properly oriented. The chippers are stacked in "rough" order and shims are used to fine tune the width of the cut. I done that more times than I care to remember and I hated it every time. Magnetic shims are relatively a new addition to the dado set market and would be a great time saving accessory. I own several "dial a width" wobble type dado blades and they are not the easiest to set up either, but no loose parts and pieces to deal with. They are known to leave tiny bat wing looking gaps in the corners, not the best looking when the dados are visible. I wasn't aware that there is a small dado set designed for circular saws and picked up a set off Ebay. I have yet to try them out, with their HSS blades and chippers.



Of course I have tried the router against a straight edge guide and found out that any variation from a snug registration will leave a divot in one edge .... Getting the proper width dado with a router will require a two pass run or an exact width router bit for the newer Metric plywood VS older fractional size stuff. I've also used the venerable RAS for shelf width dados but of course the width is limited to the travel of the carriage on the arm.



I'm still looking for the easiest, fastest and best way ........ :nerd2:
 

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Discussion Starter #13
This is a follow-up. I wrote this letter to Freud Tools and got a response in June, but didn't think to post it until now:

"ATTN: [REDACTED], Engineer - Freud saw blades
SUBJECT: Freud SD208S 8" Pro Dado Set Configuration Chart

Dear [REDACTED] and Freud Tools,

First and foremost, I would like to express my pleasure with the outstanding quality of the various Freud woodworking cutting tools that I own, including router bits, table saw blades, and the Freud SD208S 8 inch Pro Dado Set. They are great, well-designed products, and a joy to use in the woodworking shop.

-> The reason I am writing to you is to complain about the inaccurate configuration chart that is included with the SD208S dado set.

I was making a 3/8 inch box joint jig for my table saw and discovered that the cuts were actually 23/64 inch, not 24/64 inch. A difference of 1/64 inch may seem small, but for the 3 inch tray I plan to build, it adds up to 1/8 inch = 3.175 mm, a significant error. On a six inch box joint, the error would be 1/4 inch = 6.35 mm !!

I wasted a lot of time and some nice wood before I figured out that the root of the problem is Freud's configuration chart. I suspect that Freud's European manufacturing uses metric measurements. I have no issue with that, as long as the configuration chart is accurate. Once I did the calculations and added 0.1 mm and 0.3 mm shims, I got an accurate 3/8 inch cut to the required precision.

Shame on Freud for wasting the better part of my day to diagnose and deal with this issue. Since then, I have found reviews on Amazon and comments on internet woodworking forums from others who encountered the same problems. Freud sells the SD208S as a "Pro" dado stack, but fails to give the woodworking pros the information they need to use the dado stack correctly and accurately. Perhaps Freud is too embarrassed to admit that shims are required to achieve accurate US standard measurement cuts with its dado stack. I would rather have accurate charts than better marketing.

I was also unhappy that Freud did not bother to provide US standard fractional measurements on its shims. Freud prints the metric value in mm and the rough equivalent in decimal inches, which is not very useful for most US woodworkers. It took extra time for me to do the math and determine the fractional inch equivalents for Freud's shims.

-> What I would like from Freud:
(1) Please publish a TRUE AND ACCURATE CHART for my SD208S dado stack for the common US standard fractional measurements that Freud lists on its current chart.
(2) In addition to mm and decimal inches, please print US standard FRACTIONAL measurements on Freud's shims.

I do not ask Freud to change its manufacturing or tooling. All I ask for is an improvement in the printed materials and printing on the shims, to make correct them and make them useful.

Thank you in advance for reading this long message and allowing me to express my frustration. For every person like me who takes the time to write, there must be many silent customers who are equally unhappy.

Sincerely yours,

[Tool Agnostic's name redacted]"


Here is the reply:

"Hello [Tool Agnostic's name redacted],

First of all, thank you for your feedback - we always appreciate any input we can get from our end users, and we absolutely utilize such feedback in continuing to improve and ensure the quality of our products. Second, I apologize for the delayed response to your feedback, as I have been out of the office.

Regarding your inquiry, I certainly understand your position. It would be ideal to utilize the chart as a "set" assumption that requires no interpretation to achieve the desired result. The problem with our current chart is that we need to add the caveat that all stack arrangement should be verified with a test cut. This is somewhat implied by the fact that we say "nominal" width in describing the chart (as opposed to 'actual'). The reason for this is that there are far too many variables that factor into the final dado width that you will achieve after setup. The alignment of the tool, the runout on the arbor of the machine, the composition and quality of the wood, etc. will all factor in to the end result. For reasons such as these, there is only a certain level of precision that can be assumed from the stock setup chart that is provided with any dado set, regardless of the precision of that set.

Regarding your requests, I agree that we could modify the chart to be more clear that the listed dado widths are to be verified and adjusted, as necessary, to account for any variables that exist outside of the dado stack, itself. Further, I also agree with the assertion that standard units also be printed in the shims. I will propose such changes and see what we can do.

As you said, I'm sure there are other people that have had similar experiences. Thanks again for taking the time to provide your feedback.

Best regards,


[REDACTED]
Freud America, Inc. & Diablo
[contact information redacted]"
 

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What are you making? There are not many instances where the absolute width of the joints is that critical.

I usually let the pin layout determine the width of the drawer or whatever I'm making. This spares you from the nit picking hole you are getting into.

I suggest you watch William Ng's video. Think about your project and how it can be sized to the joint layout.

Once you get the width of the registration pin sized to the dado you're off and running.

P.S. There is nothing wrong with that dado set. I used one for 20 years.
 

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Discussion Starter #15
What are you making? There are not many instances where the absolute width of the joints is that critical.

I usually let the pin layout determine the width of the drawer or whatever I'm making. This spares you from the nit picking hole you are getting into.

I suggest you watch William Ng's video. Think about your project and how it can be sized to the joint layout.

Once you get the width of the registration pin sized to the dado you're off and running.

P.S. There is nothing wrong with that dado set. I used one for 20 years.
Responding:
Those are valid points. The issue does not affect how well the dado stack cuts.

I have seen William Ng's video. It is brilliant, and I recommend it to others.

With respect, I think you are making excuses for Freud. Their dado stack manufacturing is done to a very high level of accuracy and precision. They know exactly what they make and they know exactly how it measures.

Perhaps I am being picky, but I still say that it is shameful that Freud delivers an inaccurate chart, and they know that it is inaccurate. They are misrepresenting to US consumers that it is easy to achieve accurate dados in standard unit measurements. It isn't, and they don't bother to help those consumers by posting an accurate chart, shims-and-all, on their website.

This is not the same as buying a 2x4 and we all know that it is not really 2 inches x 4 inches. It is not the same as imported plywood thickness specs, although I am harder pressed to explain why it isn't.

The Freud dado stack is a precision, PROFESSIONAL tool for woodworkers, and accuracy counts. Freud measures their other cutting tools with a high level of accuracy, such as their router bits.

-> Why can't they do the same with their dado stacks, instead of telling open lies to hide the issue from US consumers?
 

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What I know about this, other's opinions may vary:

Dado sets come with shims for a reason, nine times out of ten they are set to the thickness of the material inserted into them, not to a fraction of an inch.

Anyone that does not make a test cut after any set up only has themselves to blame if things do not work out right.

Charts are only a guide to get you "close enough".
 

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Tool-Thanks for your post, very informative to me.

I don't have much experience with Dados because until recently my table saw wasn't capable of using a Dado stack. I do find it strange that the blades and chippers are marked in fraction inches but the shims are marked in metric.

The first time I tried to do a 1/2 inch dado, I set up the stack, used my digital caliper to measure the stack, made a test cut in some scrap. All measured 1/2 inch.

I then started making cuts in the wood I intended to use for the project. After a couple of cuts I thought I should measure. To my surprise, these cuts were less than 1/2 inch. My only guess is that the difference was because the test cut was done in a different species of wood and the fibers reacted differently.

Moral of the story to me was to test cut on the same wood being used for the project.
 

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TA: Just for grins I measured my Ridge Dado set. The numbers are:
Chipper body = 1/8 inch
Outer Blade body = 7/64 inch
Carbide tip extension outside the blade body = 1/64 inch

Thus it adds up to 1/8" for the outer blades, the only difference being the outer blade body on mine is 1/64" thicker than your Freud. This image shows how I measured the extra 1/64 tooth overhang on the outside of the outer blade. I did not drop these in the saw and make a cut (sawstop, yadda yadda) but will if it's of any use to you. I do not have a 3/8" box joint jig, but I do have a 5/16" jig and use the two outer and one 1/16" chipper with no shims, and it measures out at 5/16".
 

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Egg Spurt
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Not to jump at the obvious, but are your TS washers nice and clean? I was having problems galore until I watched a video several years back that suggest that I hone them nice shiny every now and then so I did and the problems disappeared right away. Turns out that both had micro amounts of buildup of rust(?) and a tiny bit of blade finishing on them which knocked things out of alignment just ever so slightly, but slightly enough to drive me batty. It was definitely causing problems with the dado stack.. Whenever anything goes out of alignment in the slightest that's usually the first thing I check.
 

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Discussion Starter #20
Not to jump at the obvious, but are your TS washers nice and clean? I was having problems galore until I watched a video several years back that suggest that I hone them nice shiny every now and then so I did and the problems disappeared right away. Turns out that both had micro amounts of buildup of rust(?) and a tiny bit of blade finishing on them which knocked things out of alignment just ever so slightly, but slightly enough to drive me batty. It was definitely causing problems with the dado stack.. Whenever anything goes out of alignment in the slightest that's usually the first thing I check.
Thanks for the suggestion. I clean my blades reasonably often. I don't usually clean the washers and nut, but whenever I change blades, I give them a careful feel for sawdust, buildup, nicks, and other irregularities. I will check and clean them more carefully going forward. Good idea.

Whatever issues I may have with the washers and nut, none of them can cause a cut to be narrower than the nominal cutting width of a stable table saw with a stable blade. If there is any instability or buildup, then the cut is at best the same or else rougher/wider.

The problem I encountered with the Freud dado stack was that actual cuts were narrower than the chart indicated. In my opinion, Freud didn't want people to notice that "easy" stack combinations did not result in "round number" standard fractional inch widths.

If you want to give Freud the benefit of the doubt, then you can argue that they wanted to match up with metric measurements that are sold in standard units, like Baltic Birch plywood thicknesses.
 
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