Micro Adjust the Rip Fence

[Nick]

"You [are] talking here about compound mistakes not adjusting to a thousand[th]s in the pursuit of accuracy."

That may be true for Woody's post, but mine brings them together nicely, don't you think?

"A difference of opinion is what makes a good horse race."
-- Mark Twain

With all good wishes,

[Ed in Tampa]

"Are we talking something the thickness of a piece of paper?"

No. About half the thickness of a piece of paper.

"...is all of this micro-adjusting really all that necessary?"

When making a finger joint, my 1/4" router bit cuts a groove .254" wide --.004 inches wider than 1/4". That means I have to make the tenons .246" wide for the joint to come out correctly. The sum of the width of the tenon and the width of the mortise must be equal to .500" for the joinery to come out evenly on 3-1/2"-wide adjoining boards. There should be seven full tenons and seven full grooves. If the tenons are also off by .004", then the finger joints will be off by over 1/32" by the time you've cut from one edge of the board to the other. Not much, but noticeable. If the adjoining boards are 6" wide, as the were in the CD/DVD holder that Drew made while he was doing the research for last week Sawdust Session, then the joinery will be off by over 3/32". Now you've got a problem. So, in answer to your question, "Is all this micro-adjusting neccessary?" -- yes, it is for this particular joint.

Can you set up the Shopsmith Router Table to make this particular joint without going digital? Yes, you can. By making several test cuts, you can zero in to the proper setup. The old "cut-and-try" method always works. It takes longer, sometimes a great deal longer, but it always works. I value my own time enough to invest in a digital calipers and a dial indicator to help me get to where I need to be without guesswork.

Does the wood move after you make the cut? Yes it does. But in this example, the adjoining parts move in unision presuming the wood is properly shop-dried. In any event, whether you are working with a dial indicator or cutting and trying, you should always assemble the joinery as soon as possible after cutting it. Waiting so long that the seasons change between joinery and assembly is just asking for trouble.

With all good wishes,

Nick
I agree we must have some degree of accuracy in our work. Without it we need a ton of wood putty. However cutting box joint (finger joint) I was taught to set my cutter up and make a first cut in the my jig. Then I was to make a stop that fit perfectly in the that slot. I was then taught to cut the stop in half. The first half was used in the slot to position my work and the second half was a spacer to determine where jig was to be positioned to the cutter. I then fixed the jig to my mitre and began cutting. If I didn't change the cutter, had made the piece to fit exactly in the cut out slot and used the other half to properly to set the position of the jig every thing worked. I didn't have to measure, I didn't have to tweak it I just had to make my cuts.
The cut off piece was always kept with the jig and was used to set the jig up each time and it was also the offset used to cut the first slot.

Again I'm not denying a certain degree of precision is needed in wood working I just question the idea of trying to measure down to thousandths. That is why I liked Dusty's idea it would allow you to tweak the whole setup to get as tight a fit as desired.

Hey if anyone ever watches the Router Workshop on PBS those guys produce some really tight box joints and they usually use a small ball peen hammer to tweak the adjustment.
Ed

[Nick]

I worked wood for twenty years believing as you do that measuring in thousandths was horse pucky. As I began metalworking to build airplanes, I became familiar -- and then friendly -- with machinsts' measuring equipment. I also learned some of the tricks that machinists have for achieving the accuracy they need. When I applied what I had learned to woodworking, I found that it saved time and frustration. Jim McCann, one of the finest craftsmen I know, went through exactly the same learning process and came to exactly the same conclusion when he was promoted to chief of manufacturing engineering at Shopsmith. He once pointed out to me that saying you can have too much accuracy is a woodworking myth-conception along the same lines as saying you can hone a chisel too sharp.

PS -- You might be interested to know that many machinsts use a small hammer to make tiny adjustments. But they usually measure afterwards to make sure their tapping achieved the desired results.

With all good wishes,

[charlese]

I worked wood for twenty years believing as you do that measuring in thousandths was horse pucky.

Jim McCann, one of the finest craftsmen I know, went through exactly the same learning process and came to exactly the same conclusion when he was promoted to chief of manufacturing engineering at Shopsmith.

Well, I guess I'm still in the horse pucky years. Who knows! In another decade I may be a convert~

Being a firm believer in set-up blocks and story sticks, maybe I've already converted myself, but I still don't give a "tinker's dam" (yes it's spelled corectly) about about which thousandths of an inch I'm working with. If it feels - looks and fits as if it is dead-on, I really don't care about the extremely small measurements.

Yep! I'll agree that box (finger) joints must be dead on to fit properly. If not exact, we might get by if the joint is only has a few tenons and mortises. But to have a box joint with multiple fingers - we must be dead-on. The argument here is; how do we get dead-on? By set-up blocks plus a tweak, or precise measurements. The answer to this question is - "A matter of choice". We must remember there have been countless woodworkers, who, through the ages, made wonderful furniture and joints without the aid of micrometers, dial indicators and the like. These craftsmen include even our own favorites - prior to the time they became "enlightened".

[Nick]

Chuck, Ed -- You guys may want to wander over to Thread #16678. Somebody has hijacked your avatars and is using them to wax enthusiastic about the Wixey Digital Angle Gauge.

With all good wishes,

[charlese]

Had to think about this a while! If I'm right, a touche! is in order. See! the conversion has already started! Is that how it sneaks up? angles before linear measurements?

Since I've logged a decade in being in the horse pucky camp, there is only 10 years to go. Hmmmm, Let's see. That'll make me 84 or 85.

At that age, I might have trouble reading thousandths on anything. Ah but there is a solution to poor eyesight! Use threads of 32/inch and quarter turns.

Question! How does one go about finding a thread by it's number? eg. #1668

[gregf]

Use the url
https://forum.shopsmith.com/viewtopic.php?t=1668

The find the specific thread in this case 1668.

Greg