Dado Blade

[beeg]

Hey Chuck, if ya ran that board through again. Would it take care of the minor slope?

[charlese]

Hey Chuck, if ya ran that board through again. Would it take care of the minor slope?

Yeah, Bob! I had also had that question in mind as we went out to eat lunch. Then thought - although the wood could be reversed and re-cut, the effort required to set up getting the dado within the same lines wouldn't be worth the trouble.

So I went to the shop again, camera and caliper in hand to see what kind of inaccuracy these three dados would present.

Measured depth of one shoulder of the 1/2" dado was 0.481" - the other shoulder measured 0.478". a difference of .003".

Question - is this significant? so found some 1/2" scrap, some 3/4" scrap and some 1/4" scrap and shoved them into the respective dados. Here's what they looked like -

[ATTACH]4636[/ATTACH]

As I had suspected the .003" slope didn't matter at all.

The photo is a little funky. I did not notice that little defect in the 1/2" piece of wood until I saw it in the photo.

The 1/2" pine sits a little proud of the dadoed piece and the shiny spot we see is a dent in the end corner of the pine. A real close look will show a small hairline opening near the right bottom of the 1/2" dado. Also the lower right hand corner of the 1/4" dado should show a small gap right at that corner. (The depth difference there is 0.0015" corner to corner.) But someone would have to inspect these dados individually to find the hairline openings.

The point of all this exercise is to point out that even some wobble dado blades work well enough for the great majority of woodwork. At many times the cost of a wobble, I personally can't justify a stacked beauty. Maybe wobbles just aren't suitable for many woodworkers, but if one is a bit strapped for cash, --- wobbles work good enough.

Minor rant!
This is fitting with a few of my earlier posts, where I have been critical of trying to cut wood to the nearest thousandths of an inch. It just doesn't pay! Close (and exact) is good - but insisting on the nearest thousandths is not necessary.

[dusty]

Yeah, Bob! I had also had that question in mind as we went out to eat lunch. Then thought - although the wood could be reversed and re-cut, the effort required to set up getting the dado within the same lines wouldn't be worth the trouble.

So I went to the shop again, camera and caliper in hand to see what kind of inaccuracy these three dados would present.

Measured depth of one shoulder of the 1/2" dado was 0.481" - the other shoulder measured 0.478". a difference of .003".

Question - is this significant? so found some 1/2" scrap, some 3/4" scrap and some 1/4" scrap and shoved them into the respective dados. Here's what they looked like -

[ATTACH]4636[/ATTACH]

As I had suspected the .003" slope didn't matter at all.

The photo is a little funky. I did not notice that little defect in the 1/2" piece of wood until I saw it in the photo.

The 1/2" pine sits a little proud of the dadoed piece and the shiny spot we see is a dent in the end corner of the pine. A real close look will show a small hairline opening near the right bottom of the 1/2" dado. Also the lower right hand corner of the 1/4" dado should show a small gap right at that corner. (The depth difference there is 0.0015" corner to corner.) But someone would have to inspect these dados individually to find the hairline openings.

The point of all this exercise is to point out that even some wobble dado blades work well enough for the great majority of woodwork. At many times the cost of a wobble, I personally can't justify a stacked beauty. Maybe wobbles just aren't suitable for many woodworkers, but if one is a bit strapped for cash, --- wobbles work good enough.

Minor rant!
This is fitting with a few of my earlier posts, where I have been critical of trying to cut wood to the nearest thousandths of an inch. It just doesn't pay! Close (and exact) is good - but insisting on the nearest thousandths is not necessary.

Who are those nuts, anyway? Just name them and we'll give them a hard time.

BTW, those dados all look pretty darn good. They look to me like those typically done by a "craftsman"!

[shydragon]

I have the Freud SD208, it cut OK, but not good enough. I think maybe one of the cutters has a slightly larger diameter. Anyway, I was at Rocklers when they opened and they had a special sale on a 6" Oldham stacked dado set. Supposedly, $139.95 normal, but a special memorial weekend price of $29.95 with only 25 in stock. They were going fast, so I thought, "what the heck, I'll bite.

I'm working on a telephone stand and I had a few more dados to cut. I set it up and away I went. I was really impressed. They really came out nice. I wonder at that price, how long they will stay sharp?

[JPG]

As a result of all this discussion extolling the 'flatness of wobble blade produced 'bottoms' I went to the source of my scorn and re-examined it to try and determine why I had previously obtained much less desirable results.

[ATTACH]4642[/ATTACH]

This is the culprit! 1960's example of SS's 'finest'.

[ATTACH]4643[/ATTACH]

This shows the adjustment scale on the wedge shaped washers. An identical pair is on the back side. At the position shown, the blade does not wobble, and produces a 5/32" groove. The scale runs through the alphabet from A to Z. These washers are adjusted with a 1/8" SQUARE key inserted into a gear which causes the washers to rotate relative to each other thus changing the 'wobble'. Focus is terrible, Sorry!

[ATTACH]4644[/ATTACH]

Here is the result obtained with the washers set to the MAXIMUM setting "Z". It produces a 15/16" wide groove, with a noticeable 'round bottom'. It also has a difference in depth of about 1/32". It is this difference in the depth at the sides that created my displeasure. The curved bottom is not so much the problem as the difference in the side depths. A board inserted into the cut would NOT set firmly at a square angle since the side depths were different.

[ATTACH]4645[/ATTACH]

This shows the results obtained at various settings of the blade. ALL have the lopsided depth problem. Closer examination of the blade revealed the source of the problem. The outer edge of the blade varies by >>>1/32"<<<! The blade is NOT round!!! This is a serious defect IMHO!

Final conclusion(s): My disdain of wobble blades was based on my limited experience with ONE DEFECTIVE blade. I am delighted to have discovered that better results ARE obtained with a PROPERLY ground/sharpened blade. The inconsistent radius of MY blade was the ORIGINAL sharpening done when originally manufactured. It would appear that its problem CAN be fixed by PROPER sharpening. That is NOT something I WILL do. TOO many teeth, and I have a chipper dado blade now.

So for me at least some good has come from this thread. Thanks to Charlese for showing me/us all that wobble blades CAN produce excellent results and causing me to re-examine why mine sucked!

[a1gutterman]

I have the Freud SD208, it cut OK, but not good enough. I think maybe one of the cutters has a slightly larger diameter. Anyway, I was at Rocklers when they opened and they had a special sale on a 6" Oldham stacked dado set. Supposedly, $139.95 normal, but a special memorial weekend price of $29.95 with only 25 in stock. They were going fast, so I thought, "what the heck, I'll bite.

I'm working on a telephone stand and I had a few more dados to cut. I set it up and away I went. I was really impressed. They really came out nice. I wonder at that price, how long they will stay sharp?

I have always liked Oldham saw blades and their router bits (Viper brand)]B[/B]lack and Decker bought Oldham out, they discontinued producing the Viper brand of router bits. B&D also own Porter Cable, and so far I can still buy PC router bits.

[charlese]

Looking at the photo of JPG's Magna blade it became quite clear to me that my wobble is not a Magna. Mine has only 16 teeth and looks exactly like the picture of the "Vermont American" wobble dado referenced earlier in post #19 - - - http://www.amazon.com/Vermont-American- ... 83&sr=8-17 (Although the picture on that thread shows 24 teeth, the text says 16 teeth.)

The Magna blade shown has steel teeth that all appear to have the same set (swedge). Since the blade is not perfectly circular, it's my guess the portions of the circumference that tilt the farthest have a larger radius so they will form a flatter bottom to the dado. Guess that didn't work too well.

The blade I have has carbide tipped teeth that are filed with varying tips according to their placement. If you look at the 1st and 2nd photos in post #29 you will see black marks below the carbide on the out part of the wobble. (This was caused when I had the blade set at 1/4" diam. inside the regular sawblade insert - and missed the center.) (Note that on one side of the blade the marks are on the opposite side of the circumference from the marks on the other side)

The tooth in the center of those marks sticks out the farthest in a dado. It's tip is filed with more inward slope than the others. The slope becomes less as until there is a flat tooth and then, on the next couple teeth, the slope changes to be high toward the opposite side of the blade.

I don't know who made the wobbles for Shopsmith when I bought mine, but my 2006 catalog shows the same one I bought. I noticed Dusty's wobble has fewer teeth than mine.

Also, This is the second wobble I have owned, I left the first one in Montana when we moved. It was exactly the same as the one I bought from Shopsmith. I think I bought that one at an Ace Hardware.

[dlbristol]

Nothing at all to add, but just reading through this thread was an education. I have both types and I now know better how to use both. Thanks

I am waiting for the day when my craftsmanship is good enough to reveal a defect in one of the tools!!!

[JPG]

. . .

The Magna blade shown has steel teeth that all appear to have the same set (swedge). Since the blade is not perfectly circular, it's my guess the portions of the circumference that tilt the farthest have a larger radius so they will form a flatter bottom to the dado. Guess that didn't work too well.

. . .

I thought so too, but the larger radius 'teeth' are NOT located so as to do that. The sloped washers are located to the blade by 4 holes around the center hole. This provides 4 positions to attach them. The increasing wobble when setting the washers does not(CANNOT) align with the largest radius. I have tried all 4 positions (and 4 other not proper(the washers do not correlate side to side)positions).

The varying tip geometry obviously gives excellent results as you have shown.

A comment re chipper type blades. The outer corners of the groove should be excellent, but the center portion may not be. After all it is chipping, not cutting in that area.

Changed 'slopped' to 'sloped'!

[osx-addict]

Anyway, I was at Rocklers when they opened and they had a special sale on a 6" Oldham stacked dado set. Supposedly, $139.95 normal, but a special memorial weekend price of $29.95 with only 25 in stock. They were going fast, so I thought, "what the heck, I'll bite.

Darned! I wonder if they were doing that at all of the stores? I drove past our local Rockler (Torrance) and they had a bunch of stuff setup in the parking lot but I didn't have time to stop and visit.. I'm guessing you were in the Portland store since there's only 1 Rockler in Oregon -- I've been to it twice -- nice store...