I’m forwarding this message from another forum (with the original poster’s permission). Some of us are wondering whether this is a deliberate design “feature” meant to respond to undersized plywoods?
Without further ado . . .
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I just got my new FREUD SD206 Stacked Dado set from Amazon.com. And being an Engineer, the first thing I did was to perform an “Incoming Inspection”. Checked the Chippers to see if they were to spec (they were). Then I checked the two outside 10 tooth blades to see if they were also to spec. Somehow, I was under the impression that they were supposed to be .125″ thick, but they weren’t!
SO I did the next thing engineers do and that was to start running calculations. They were .134 thick each, but when you figure that there are two of them and only the Tooth thickness to the outside matters. I did some MORE calculations! Across the Carbide tooth is .134, the body of the blade is .100 thick, therefore the total thickness of the two blades is equal to .034 (thickness of the teeth, minus the blade body thickness) plus .200 (two saw body thicknesses), which equals .234. That’s approximately .016 shy of a full 1/4″!
Is it normal to add a shim to achieve the full 1/4″ thickness or did I miss something? Just curious, since this is my first Stackable Dado Set.
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Any ideas?
Replies
Six millimeters is .2362", remarkably close to your correspondent's .234". If most 1/4" plywood nowdays is actually 6mm, I think it makes sense to sell a dado set that is 6mm without shims and requires a shim to cut 1/4" grooves. All the alternatives seem to be more hassle or more money or both.
Norm,
Ditto Uncle Dunc's comments. I spent several hours yesterday with my new Systi dado system...got it perfect to cut dados in the 3/4 oak ply...only one in four did the cut actually fit perfectly the rest had to be sanded. This was all top grade ply too...
Personally, I do not like using the shims (after one days experience). They are hard to put on and take off and, at one point, I noticed the inside blade was loose and could not be moved without taking the whole thing apart again. From now on I'll shim the fense with sheets of paper and run it twice.
BG,
I cut a lot of dados in 3/4" and 1/2" ply, and have a tip that may speed things up in stacking the chippers.
Stack the blade for 3/4", make a test cut, then as you take'em off, mark the chippers with a permanent black marker, "3/4 ply."
Do the same for the 1/2". Most will be the same, so mark them for both.
You don't have to mark the inside and outside blades, as you will be using these all of the time.
Your cut will change anytime you have the blade reshaprened, so indicate on one of the outside blades what shims you use.
Norm, an interesting quote, and I just wonder if it matters very much what the dado blade stacks up to at its thinnest setting, 6mm or 1/4". I suppose people must be aiming for full housings, dados and grooves much of the time to accept the full thickness of plywood, MDF, etc., which in my work is a rarity.
Normal practice for me is to run something like a 6mm, 12 mm or 15mm router bit to form the housing, etc., the housing width depending on the needs of the job, followed by creating a shoulder on the end of the shelf to suit. It's generally a stronger joint because of the interlocking returns, the additional gluing surface, and the shoulder line can be used to hide any slight gap in the joint on the money side.
It's the work of just a few minutes to work a shoulder on the end of a squared and wide piece of ply/MDF, etc., with a router, a small cutter and a side fence followed by ripping the wide piece into suitable shelf widths. I follow a similar routine for working housings or dado's-- rout them in a wide piece, and cut it to width later. Any slight tightness of the tongue due to variations in board thickness can be fixed with a couple of strokes from a shoulder plane.
A dado blade could surely be used in a similar manner by setting it up to cut an approximate, let's say, 1/2" dado or groove, and working a tongue on the end of the 3/4" shelf? I know that in the time it takes my shopmate to fiddle with shims and the like getting his dado blade just so, I've already cut two or three cabinets worth of carcass sides, tops, bottoms, and all the shelves, ha, ha. Slainte.
Sgian,
Don't make fun of your Shopmate that way..yes, he's slow..but doing good work...and using less glue because he dosen't have those shoulders to paint up. ha ha
BG, by the time he gets to 10 or 15 cabinets, he's about caught up with where I'm already at-- and outside mass production, who makes more cabinets than that in one go?
Never yet found a use for a dodo (sic) blade where I couldn't do the job just as well, or better, or safer, or faster, by other means. Slainte.Some stuff I've made.
Norm,
Your math assumes that the teeth are cebtered on the plate. Have you actually made a test cut and measures the width?
TDF
Thanks for the comments, guys.
--Tom, it wasn't my math, but the person who's message I was quoting; I'll pass your response on. Thanks.
". . .and only the stump or fishy part of him remained."
Green Gables: A Contemplative Companion to Fujino Township
Norm, an engineer from Freud hangs out on some other forums. I'll send him a note and suggest he stop over here to take a look at this post.
But, I would suggest the poster measure the distance between the outside of the two blade tips when the two outside blades are assembled. The tips are not necessarily centered on the rim of the outside blades.
The problem with his calculations is that he assumed that the tips are centered on the blade plate. This is not the case. To accurately measure the tooth offset would be difficult. The 2 outside blades will stack to cut a 1/4" dado (.250" +/- a couple of thousandths).
Charles M
Freud, Inc.
Thanks for the "from the mouth-of-the-horse" clarification, Charles; yours was the reply I was most hoping to get.
And thanks to everyone else for all your discussion; it's what makes this forum so great!
". . .and only the stump or fishy part of him remained."
Green Gables: A Contemplative Companion to Fujino Township
Charles,
This may be a dumb question for you (the Boss), but how do we cut a dado or groove slightly less than .250 for 1/4" plywood (which is around .220) with your stacked dado set?
You don't, you take the simple route and just run it on two passes with your normal 1/8" kerf crosscut blade. The first pass is 1/8" and the second is whatever else you need.
The stacked dado sets that are available today (at least the ones that I am aware of) all start at 1/4". One that would go down to 5.5mm for plywood would be an instant success.
Charles M
Freud, Inc.
How about a 1/8" kerf blade together with a thin kerf blade with the same number of teeth? They should both have enough set on them that you could put some shims between them and still not leave a ridge in the middle of the dado. Of course they'd have to be exactly the same diameter too, and that might not always be the case.
Well, that's what I've been doing. I just stack two 7 1/4 skil saw blades and it works out great.
Hi Norm
Take a look at Freud 's catalogue a lot of their shaper cutters and router bit dimensions are odd eg 29/64 most are made in Italy and I think they are conversions from metric.Anyone else out their noticed this?
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