View Full Version : dados,finger joints
02-15-2001, 08:28 AM
can some1 tellme how can i put 2blades in my circular saw-bench , what i need to buy to adapt it to make finger joints
02-15-2001, 09:39 AM
You can't safely double blade a saw. They'll interfere and you'll break teeth. Blades are typically hollow ground where the arbor is thinner than the tips. If you try and mount two you'll have serious problems.
You can buy a dado blade set that is designed for this use. However most bench saws aren't capable of mounting them. This is because the motors aren't powerful enough to swing the larger (thicker) heavier cutters. You may find that the arbor is too short to mount a Dado set. This is how the manufacturers prevent you from using them.
You can get a jig that allows you to cut finger joints with just a standard blade. Here is a good one: http://www.netexperts.cc/~lambertm/Wood/lynnjig.html
02-15-2001, 11:43 AM
Mark!...you're a tablesaw salesman! hehehe...
Now don't get offended....I'm just kiddin...I thought it was funny that the the first 2 replies I read from you basically suggested that the saw was the culprit due to it's size. :)
BTW...I attached my old Ultra fence to the other end of the TS-III carriage and attached my router auxiliary fence...now I don't have to shift anything except the base unit to switch from tablesaw to router...works great...but I may need to order a couple more of those fence supports that slide along the top of the rails...the second fence is kinda heavy and makes the whole unit not wanna slide too well.
02-16-2001, 12:39 AM
How about a picture of the setup?
02-16-2001, 10:35 AM
How I did it:
I didn't have the arbor problem, however what I did was to make an extension fence for my miter. 6" high and about 24" across and mounted it to the miter.
I layed out a pin for indexing precisely 1/4" from the blade. This was a brass 1/4 x 20 screw with the head off that threaded into the phenolic fence. Using the unthreaded shank of the screw as the pin.
By butting the panel for the toy boxes agianst this pin on end and cutting the first finger and then moving the piece to where the slot indexed over the pin and cutting the next slot.
I kept stepping the panel acrossed the fence in this fashion until the whole side or end panel was fingered.
Then checked it against the mateing corner to be sure I got it right and stepped the mating piece.
When all the sides were fingered and grooved, they fit very tighly together.
If one was to want say 1/2" fingers, another threaded hole for a 1/2" cut off bolt could be used by removeing the fence, flipping it end for end and laying out a sister to the 1/4", but layed out for the intended 1/2" pattern.
The boxes I made this way came out beautiful and strong enough for the intended children to play in and to use as a hope chest or blanket box when these Grand Daughters are all grown up.
Each so far has been a one off individual chest, simular but different, just like them.
I found this method to produce tight and beautiful box joints.
Simple, precise, and accurate as the only thing moving was the actual panels being stepped across the fence/pin with the 2 outer dado blades set up on the arbor.
And I agree that using 2 saw blades could be dangerous. One might use the pin method discribed with a wide kerf blade and a pin of the same width as the kerf to produce a finer box joint where a dado blade cannot be used.
But care in handeling and assembly would be in order as the fingers would be inherantly smaller.
I hope this gives some of you another idea to utillize what you have to work with.
Work safe and have fun in your shops!
02-17-2001, 01:43 AM
DC hose is blocking view of fence on the left...I loosen 2 knobs and the router fence slides off...works good.
02-17-2001, 09:07 AM
Wow! That's an ... interesting ... configuration!
Looks like it works just fine too.
Question, why did you do it that way instead of just mounting the bridge to the right of the router table? Clearence?
You see the end of the fence is wayyyyy out there...
02-17-2001, 09:13 AM
Problem I've encountered with 'pin' jigs like you describe is that unless you can get the pin just right, you wind up with cumulative error as you march across the width of the board. This compounds as the boards get wider.
The Incra can step and repeat without cumulative errors and also allows you to do other width fingers without multiple jigs.
Ditto for "Lynns Box Joint Jig" - http://www.netexperts.cc/~lambertm/Wood/lynnjig.html
This jig uses a lead screw to step the workpiece. There is essentially zero cumulative error in the screw and you can micro adjust as you index to make the joint tighter or looser. Finally it doesn't require a dado blade set for it's operation.
02-17-2001, 04:01 PM
Well, shucks MM, I recon I just did the best I could do for me.
The whole she-bang worked fine at the time, and there weren't no "Cumulative" error.
Either I got lucky or God graced me with some skill. I donno, my friend, but at the time I thought a forum was where they hosted boxing matches. Just my ignorance, I guess.
NOW I have lots of reference from lots of experiance from a lot of friends on this forum.
And I highly value the input! I may not follow exactly, but I sure do appreciate the input.
Sure gives me Ideas! and the ways others found to do and be where I'd like to be.
I just got my router table done this mornin' and all is square and plumbed.
Oh, I got the springs out of the PC 7539 as well, piece of cake when I followed the lead. Damn those springs are long boogers!
I can see where the fine adjusting will be a lernt process. But I have time to figure that away. Too bad PC doesn't think along the lines of the craftsmen who actually use the tools.
I reckon that it's another one of those "paper bridges" fellers who figure and fix can't cross.
We might make some colledge feller look bad 'cause he didn't lernt no common sence.
Not that education is a bad thing! It helps do what Mom and Pop couldn't kick into the kids' head, for whatever reason.
I got lucky, Dad had a strong leg and a good ethic about work. And enough love to allow me some mistakes and still forgive me.
Anyhow, I do appreciate your input and the pictures are cool!
A picture is worth a thousand words.
I'm more of a man of a few thousand words, myself. Did you happen to notice that? With a rye sence of humor mixed in.
02-17-2001, 08:52 PM
Hey, not throwing stones!
Just said that pin jigs tend to have cumulative errors. Little .005" position error gets multiplied at each notch. After 20 (10" with ¼" fingers) you're out .1" and that's more than enough to show. Not saying your method is wrong. Works good — usually. But any slop in fixture gets transferred DIRECTLY into joint.
Lead screw based jigs have a couple of advantages and disadvantages. #1 disadvantage is slower to cut & more cuts with "standard" blade. But lead screw jig also allows fine tuning joint from "hammer tight" to "hinge loose". Also doesn't require $80 dado blade set. For folx on a tight budget this is a saving.
02-17-2001, 10:19 PM
Oh, heck no Mark, I wasn't offended. Please never think that.
I was just trying to point out a way that worked for me.
I personally wouldn't want to turn a screw to make a box joint, so I devised a different method out of my own ignorance of any better way.
Remember I'm a tinkerer at heart. I have almost as much fun farting around as the actual project at hand. It's the mental and skill challenge, I always win, too.
Often, I can spend hours building a jig just to do what takes minutes to complete.
But then I have the jig to fall back on later. For simular or to repeat a piece, like molding. And often a scrap to set it up from the last run.
I spent all day to day finishing my revamp of my TS/router/disk sander. If I don't stop soon the whole shootin' match is going to sink into the concrete. But it all works great for me.
I'll have the page up soon, but just stopped by since this page was open and I hadn't gotten kick off by EL. I'm amazed.
02-18-2001, 10:16 AM
yea...that's it. No room at all, plus in a production shop every little bit of time saved helps...I can cut em, plane em, and then joint em without switching any equipment around...
02-18-2001, 10:38 AM
The way the Incra grows, I though I'd have to knock a little 6"x4" hole in the wall for cutting wide stuff! :)
02-19-2001, 01:12 AM
Did you ever try a quarter square piece of aluminum stock for the pin in the jig?
02-19-2001, 08:13 AM
It isn't the pins size that's at issue. It's the pin's position relative to the kerf that has to be TIGHT. That's one of the advantages of the 'lead screw' jigs vs the 'pin' jigs. You can dial the lead screw jig to whatever degree of precision (fit) that you want.
You want TIGHTER, just go a hair past (5 min) your mark on the first index (but don't accumulate) This will give you 1/16" / 12 or about .005" too narrow a gap and a correspondingly wide tooth for a .010" interference fit (get out your hammer!) Conversely stopping 5 min shy of your mark will give you a .010" gap between the teeth and you'll have a "hinge" fit.
Because of the nature of the handle, it's pretty easy to consistently stop dead on the mark and make a "perfect" joint - one that you can put together and take apart by hand but that holds together on it's own.
02-21-2001, 01:58 PM
Just the other day, I was at Lowes. It appears that Delta is making a 1/2 " adjustable dado blade. I believe they are making it for their bench saw. It costs about $30.
02-24-2001, 11:24 AM
hi, i ,m trying to understand but with a pic would be easy
can i have a picture if u can?
02-24-2001, 11:02 PM
There's a pic posted up higher in the thread of the lead screw type. Do you need a pic of the pin type?
Wow! I built a Lynn 'leadscrew' Jig this weekend, and was so impressed I built two more for woodworking relatives! I am relatively new to this, and spent the last week trying to make box ends with a chisel and a handsaw. Thanks for the advice!
02-25-2001, 08:50 PM
Great little gadget, eh? It's amazing how precise it is for something that you can just slap together.