I want a New Tool - linear dado

[atgcpaul]

Festool to the rescue!

https://youtu.be/9POXLMRpbI0

Or you can hack one together like this guy:

https://youtu.be/Hw9epcbJJNc

[LCHIEN]

Thanks Loring. I am in the debate stage at the moment of trying this with a 6 inch stackable dado or the wobble type. I don't need both but sure hate to buy one and then find the other would do better.

Amazon has a 7 inch wobble type here for $38.10: https://www.amazon.com/gp/product/B0...SJ8XZPQC&psc=1

Plenty of craftsman wobble dadoes 7" with 16 or 24 carbide teeth. On ebay for $20-25 after shipping.

l have a Vermont American 6" stack non carbide. From a long time back.

[leehljp]

I have a Metabo 7 1/2 inch circular saw; I took the guard off and checked; a six inch diameter 3/4 dado seems very doable. I am in the process of making two parts -
1. a back side washer to hold the blade outward by about 1/16" inch from the housing. I will determine that when I am close to finishing.
2. a 5/8" shaft extension for the wider dado blade. The exact length is not yet known either. I have several 5/8" shafts (3/4" long) with a 1/4" hole for the bolt, but I will have to drill one or two out (on the lathe) for a perfect fit with the arbor bolt.

The reason I can't figure out the shaft length and backside washer thickness - is that I can't get everything in there and the calipers too. It is all guesstimation at this point. But it is close.

It looks very doable, just a few weeks away, maybe over Christmas and I will have some time. Hopefully the week of Christmas I can get a day in to play with it. I do have longer bolts than the original. These are 8mm hex head bolts.

I will make a sled guide for running it across a board and clamp it (guide) down. All I will have to do is align the sled with the marks on the board.

THE ADVANTAGE of this set up over a router is that a router guide is always set to a particular size bit. Change the router bit from 3/4" to 1/2" and suddenly your alignment is off and a different guide is needed. I also discovered that bases of routers are not 100% equal on one side from the other and that alters the layout. Not much, but by a millimeter or two. I hate that. I have 3 different guides (2 purchased and 1 made) for doing router dados and it takes fidgeting to get it right. One change of a router, or a bit, or the orientation of a router and alignment is off!

SO, for this Metabo saw, Build a sled guide similar to a track saw or more like a sawboard. The motor housing is on the left side, make the guide for the left side alignment and it will always be accurate even if I change from a 3/4" to 1/2" to 1/4". Perfect dado alignment without having to fidget and figure. Set the guide on the line, clamp and saw; move to the next. AND NO more board tilting trying to cut a dado on the end of a 7ft board with the table saw, and no more misalignments due to changing router bits or routers.

[LCHIEN]

Aren't you going to need a long shank left handed arbor bolt?

That'll be fun to find.

[leehljp]

Aren't you going to need a long shank left handed arbor bolt?

That'll be fun to find.

It is not a problem for me. Most circular saws where the motor is on the left side of the handle (and the blade is on the right side of the handle) use right handed threads, as does mine of course. Since the blade cuts up and the motor is on the left side, right handed threads are the ones to use. If one has a rare left handed circular saw with the motor on the right side, I think those use left handed threads.

The right handed threads / left handed threads are determined by the direction of the blade in conjunction to its location on either the right side or left side of the motor. I "think" this is the way it is, but could be wrong. I read something about this a loooong time ago before the internet, so the internet might change this and prove my memory old or botched.

THEREFORE for me, I can find various 8mm right-handed bolts easily of various lengths.

However, it would not have been a problem anyway. I have an friend who does machining and tooling. He used to be a teacher but he found out last year that he could make more money machining with less hassle. Anyway, He came by my office today to pick up a Christmas present for his mom (who used to work for me) and we got to talking about his "new" job. I asked him if I needed a left handed thread 8mm bolt, could he make one? He said sure I can. That was just after I read your comment this afternoon at work, (but knew that the threads on mine were right handed). We spent an hour talking, and now for the parts I need to make this circular saw into a dado circular saw, I can get it machined. He was very interested in my saw, and now I may have some help.