Cutting Super Accurate Dados! I will pass on the Festool way...

[Dev Emch]

O.K. So I messed up. Normally one uses the same setup to cut all items that need that particular cut. But this time, I goofed up and had to break down a setup and then go back to where I left off. The culprit was a precise dado in a side and back panel. So how to reset the setup to be super perfect. Here is an approach that worked super fast and super accurate.

The dado is meant to recieve a slab of 3/4 in baltic birch which is some form of metric thickness. Forget about buying a router bit for this stuff! Instead, I took my trusty porter cable 690 equiped with a MICRO FENCE and installed a 3/8 in two flute spiral cutting bit. The exact dado is something on the order of 0.710 in and is located 4.750 in on the bottom side up from the edge. In other words, the edge location is 4.750 + 0.710/2 or 5.105 in up from the reference edge to the aproximate centerline of the dado.

So begin by locating the micrometer leadscrew on the Micro Fence to midpoint. Eyballing is fine. I like to eyeball and then set the dial to zero. Lock it down. Then undo the rapid movement and set the router to cut apromimately the midline of the dado. Accuracy here is eyeball close enough. Lock down the rapid movement screws. Set the router depth to the dado depth. Complete your first cut.

Now using a caliper, measure the upper and lower cheeks of the first cut and write these numbers down. The lower cut is position dependent on being at 4.750 in so take the lower cheek cut number and subtract the 4.750 number from it. Dialing the micrometer clockwise pulls the router to you and dialing the micrometer counter clockwise pushes the router away from you. Dial in the amount you just calculated minus say 5 or 10 thou clockwise and take a tiny cut. Take a measure and verify your where you need to be. Use the 5 to 10 thou wiggle room to adjust as needed. Compete your lower cut. Then dial the micrometer counter-clockwise the exact thickness of your material and and complete the upper cheek cut.

This sounds like a lot of work but really isnt. You just need to familarize yourself with the concepts and then you see that its easy. This approach will cut spot on router cuts accurate to within a hair's thickness. What makes this approach so darn simple is the excellent design and workmanship of the micro fence. I have two micro fences setup for porter cable routers and given a choice between a brand new festool router and my porter cable with a micro fence, you couldnt give the festool! I think there are now adapters available but they seem clumsy to me. The micro fence, configuration A, is the original design and it simply fits the base of the porter cable router. No clunky adapter hardware or base modifications needed etc. Once you have used the micro fence with a router, you will be so spoiled you wondered how you lived without one. Now in order to really adapt a festool 1400 to a festool guide rail, you really need to get the micro fence circle cutting jig. In this jig are adapters and the famous micro fence micrometer that allow you to interface the festool 1400 to the guide rail with that famous micro fence accuracy eand ease.

So I am one really happy Micro Fence customer! Its great to see such a simple and accurate and well made tool being made these days!

[Steve Clardy]

I have a micro fence. Adapted to a 7310, and 690.
Nice fence!

[Mike Cutler]

Dev.

The MicroFence is a sweet little product. I had to make my own adapters for the PC8529 since they wern't available at the time.
I actually just bought a PC892 off the closeout table at the local 'Borg specifically for use with the MicroFence.
It's a nice little accessory, and you should see Bill Hylton use it. The man is a whiz with a router.

[Hoa Dinh]

Since Dev mentioned F, I can't but mentioning E

No, no, I don't want to start another fight. I just want to mention another way to make accurate dados with the SRK since many of the members own it already (or are considering it).

The method was outlined in the next-to-last post of this thread.

Have fun.

[Dev Emch]

Since Dev mentioned F, I can't but mentioning E

No, no, I don't want to start another fight. I just want to mention another way to make accurate dados with the SRK since many of the members own it already (or are considering it).

The method was outlined in the next-to-last post of this thread.

Have fun.

The key to using the Micro Fence is its Machinist Micrometer. It also makes horizontal adjustments unique in the router world as Micro Fence is darn pround of a little slip of paper the US government awarded them. Its called US Patent #5,299,609. Now using a guide fence with a router is not unique. Using a calibrated leadscrew to measure sub thousandths of an inch is also not unique as machinists have had mikes for better than 100 years. What is unique is combining the two to move that router guide fence and that is the gist of the patent. All a micro fence is is a horizontal micrometer for a router. I know of no other way to control horizontal movement of the router with this level of precision and simplicity and not wind up in a civil proceeding with Micro Fence.

[Dave Tinley]

.
Dial in the amount you just calculated minus say 5 or 10 thou clockwise and take a tiny cut. Take a measure and verify your where you need to be. Use the 5 to 10 thou wiggle room to adjust as needed. Compete your lower cut. Then dial the micrometer counter-clockwise the exact thickness of your material and and complete the upper cheek cut.

!

Jeez, I have a hammer that will make that same adjustment

Glad that $399.00 was a good investment-

Dave

[Burt Waddell]

Dev,

First let me give the micro fence a lot of credit. For many applications it is still the best on the market.

For applications such as this one, the EZ SRK offers the quickest and easiest way to do the job. FIrst you can set limit stops to set the specific limits of the cut and then you can set the repeaters for specific location on the board. Couldn't be easier or faster than the EZ Matrix way.

Burt

[Doug Shepard]

Was that a gauntlet I heard being thrown down??

Dont have any of the Festool or EZ stuff (yet) but I'll second your vote for the Microfence guide. It's maybe the best made tool I've ever bought and almost makes routing fun. Their circle jig and 3-axis plunge base are right up there in the same league.

[Frank Pellow]

...
The dado is meant to recieve a slab of 3/4 in baltic birch which is some form of metric thickness. Forget about buying a router bit for this stuff!
...

Dev, the thinkness of nominal 3/4 inch baltic birsh is 18 mm and Lee Valley sells an 18mm straight bit the works perfectly.

[Dev Emch]

Dev,

First let me give the micro fence a lot of credit. For many applications it is still the best on the market.

For applications such as this one, the EZ SRK offers the quickest and easiest way to do the job. FIrst you can set limit stops to set the specific limits of the cut and then you can set the repeaters for specific location on the board. Couldn't be easier or faster than the EZ Matrix way.

Burt

With all do respect, NO_ BLOODY_WAY! I posted this thread with a unique problem description and this approach nailed me within TWO THOUSANDTHS of the original dado blade cut dados on the other pieces! TWO THOUSANDTHS! I dont care if the SRK is made of gold, if you can quickly and REPEATABLY reproduce that level of accuracy WITHOUT using a calibrated lead screw, my hat is off. If you do use a calibrated lead screw, then your in violation of a patent. Its that simple.

This thread was posted not as a advertisement to an EZ product but rather as an application note of how a micrometer adjustable router can make things easy given the unfortunate breakdown of the original saw setup.

This is one of those applications where the micro fence is the only game in town. I did not have the time to bump and jump a zillion test cuts making a pile of firewood. After all, I have to get done and move on. If that dado was off by say 1/64 in, then I would have to get out the no mar, lead shot plastic attitude adjuster by snap on to get the bottom base to fit.

Furthermore, all of this work is referenced off of the bottom edge and front edge. Those are my calibrated datums. The back edge and top edge must run parallel to these. By introducing a guide system, your assuming that guide system is spot on perfect and that there is no human error in setting it up. Would you cut a hundred identical items by measuring and cutting measuring and cutting measuring and cutting? No! Even if you had a million dollar NIST certified measuring rule, you still have the human element introducing a RANGE of errors to either side of your estasblished width. The skin on your forefinger can feel this! You would set up a cutting system with stop blocks. Be that a RAS, table saw or bear skins and knives. This is how you can quickly cut a number of identical items. Break down your setup and your going to have a tough time to accruately re-establish that setup. That is what happened here. BUT, a micrometer positioning system can be used to inch you up to the original setup! And that patent protected micro fence had the problem solved in less than 5 minutes.

[Dev Emch]

Dev, the thinkness of nominal 3/4 inch baltic birsh is 18 mm and Lee Valley sells an 18mm straight bit the works perfectly.

1). After cutting truckloads of this stuff, I can tell you that 18 mm is just that.. NOMININAL. Your results may vary as they say. And it does. The actually thickness wonders a bit.

2). I have notes after my truckloads of cutting this stuff telling me which chippers and which shims I need to start with and what the various dado will be width wise. No problem there.

3). The problem lies in the fact that three dados have to line up to make me happy with two right angle corners. And slop can result in shadow lines on the inside of the case. I want my joints tight as a bug in the rug. So if you cut all three dados at the same time using the same reference edge, life it good and it pops together. But if you cut one at a different time using a different setup, guess what!!!!!!! ITS HAMMER TIME! And one side may need to go low a bit to allow for a fit thus resulting in an open joint line on one exposed side. Again, not good!

So this very straight forward tool presented a solution that took less than five minutes to setup and about 20 seconds to final cut and nailed me within TWO TOUSANDTHS of an inch straight out ot the box! No test cuts doing what I did. Besides, I had no spare stock to perform valid test cuts on anyway. Mind you, your fighting two battles here! Not just the width of the dado but also its relative position to the other two dados.

[Jim Dailey]

Dev,

Nice informative post.

But am I understanding you correctly.... you are using your PC with the Micro fence with adapter to mate your PC690 with the Festool rail. I have been thinking about adapting a PC router to the Festool rails as opposed to spending the coin of a Festool 1400.

Thanks, jim

[Dev Emch]

Dev,

Nice informative post.

But am I understanding you correctly.... you are using your PC with the Micro fence with adapter to mate your PC690 with the Festool rail. I have been thinking about adapting a PC router to the Festool rails as opposed to spending the coin of a Festool 1400.

Thanks, jim

No. I am using a PC router model 690 with a configuration A Micro Fence. No special adapters needed.

To answer your question. I wanted to buy a Festool router and Festool fence until I learned that it was not needed. So I saved some coin. But what I did learn was interesting and useful. First of all, the 1400 does not cleanly integrate with all festool family members. To get the 1400 to fit the rail system, you need to buy a special plastic filled adapter. Plastic filled items are a way of making things. At one time, nylon filled was also popular. For our purpose, its plastic. Instead, I found out that by using a special adapter plate on the router along with parts from the Micro Fence Circle cutting Jig, you can hook up your Festool 1400 router to mate with the Festool and other rails. In so doing, you need to use the Micro Fence Micrometer attachment in the process. This now gives you micrometer accurate adjustment capability along with the use of the guide rail. I see no reason why the plate and shoe cannot be used with other routers. In fact, several routers are supported. I would have adapted my older porter cable routers to use the festool rails if those rails actually proved useful for what I do. There are a million ways to skin a cat. But there is only one way to use a micrometer to control horizontal movement of the router head relative to its fence and its patented by Micro Fence. I have had excellent results with it and as a machinist, I am quite familar with the use of the micrometer positioning dial. It really makes life easier and gives you control down to the mere thousandths if needed.

[Chris Barton]

Jeez, I have a hammer that will make that same adjustment

Glad that $399.00 was a good investment-

Dave

While I don't use the hammer route, I have found that a fence and guide bushing and a strait bit of virtually any diameter will acomplish this. Draw lines for slip fit of dado width, cut one side of dado with fence and router, realign router bit with other side of proposed dado, set fence, cut and you'er done.

[John Lucas]

Dev,
Thanks for a very informative thread. I am one that has and uses the MicroFence with the Festool router and the MF makes it a breeze for accuracy.

Here is the how to section on it: www.woodshopdemos.com/l-m&t-6.htm