Precision

[mickyd]

Influence on perceived quality --- sorta like polished aluminum?:)

Perfect example!!:D 20 coats of finish.....another example. What difference does it make? "0" How does it make some feel? "100"

[robinson46176]

I don't think I missed that point, as the author seemed to ridicule his friend's effort to achieve a "glue-line rip" using a saw, something that is easily achieved with a decent saw blade like a Forrest WW II. Moreover, if someone's set-up on the table saw can't get a square edge for gluing, I'm not sure that his jointer's "good enough" set-up would achieve it either.

Also, the author says: "it's more fun to build a project than worry about thousands of an inch." He doesn't qualify that statement, but if you've ever cut mortise and tenons, dovetails, dowel joints, etc., you know that a good fit (down to a few thousands) is required if you want a quality joint.

Nevertheless, I'm for enjoying ones hobbies and if good enough makes someone happy, then that's fine with me. But, a magazine like Wood shouldn't fill space in its magazine with articles that seem to minimize precision.

Art in Western Penna

You must have read a different article than I did. I didn't pull that attitude out of it at all... I thought it was an excellent presentation of another view. One that I daresay includes a far larger number of hobby woodworkers than the "engineering approach" does. I'm not sure guys should be allowed to "machine" wood until they learn to whittle.
There is too much more to life other than being up-tight about everything.

[robinson46176]

Precision, what are we talking about?

There are really (at least) two discussions going on when ever this word is used here on the forum.

There is one school that seems to say precision can be taken too far because, after all, we are working with wood and over time wood changes size and shape. Close enough is the best we can strive for without getting ridiculous.

There is the other school that says precision is necessary and readily achievable if you are willing to spend some time up front. Safety is important, too. A safe shop is near impossible if your equipment is not properly aligned.

The miter tracks and the rip fence must be parallel to the blade. With these as your only objectives, alignment can be done with "close enough" as the standard. Close enough to not create an unsafe condition - no binding, no kickback.

However, once you are this close, it is very easy to get your Mark V dead on. I used to think that 1/16" was pretty darn close and 1/32" was getting a bit anal. Now accuracy to within .0315" is pretty darn close and can be achieved without being anal. Just pay close attention while doing your alignments using a square and straight edge and you are there.

This by the way is one place where you have to get a bit anal. If your square isn't square and your straight edge isn't straight., you don't have a chance.

Notice that I have not made mention of a caliper or a dial indicator. Why, because we have been discussing "close enough" applications.

If this is good enough for what you do in your shop, good. Strive no more for "precision". You are there by definition.

However, if you want accuracy to within 1/1000ths of an inch, you got some work to do. Just know that it can be achieved using your Shopsmith Mark V. I know because I have done it! But, you must get anal about a few things. A dial indicator helps.

Repeatability is another criteria but we hardly ever speak of repeatability. That is possible, too, with your Mark V. In my opinion, repeatability is more of a discipline than it is an adjustment to the equipment.

With precision and repeatability, you can do "fine wood working" on your Mark V.

There are forum members here who demonstrate that regularly. We have seen pictures of their fine works. Some of them like to argue that this "precision" is not necessary and they might be right but their work shows that it is achievable even if not necessary.

Pretty well stated Dusty. You should know that while I like to poke at you with a stick now and then I don't really consider your efforts at machine precision to be anal... A large part of your efforts were toward the absolute best accuracy that you can achieve but then you drop back to what you consider reasonable and practical for most woodworkers. Those goals are part of the hobby for you but you have never pushed everybody else to match your goals or go down your road other than to stress the safety factor of correct alignment.
As you say an improperly aligned machine can be very dangerous.
Some times we achieve the same things with different approaches. You may align with a dial indicator and I may align with a stick but our results may not be all that far apart. The biggest difference is that I know something is aligned OK, you know how far off it was to start with.

[fjimp]

I for one admire anyone able to craft an item that serves a purpose well. I especially admire a true artist. In fact much of what resides an tables or hangs on walls in my home come from the hands of craftsmen. In my mind a craftsman is one who can dream form and function and create it. Generally speaking those are the folks who create beauty. My father in law was such a man. He handcrafted for five of his six daughters their choice of a sewing or a dining room hutch. One daughter always felt her father was a cobbler and refused to have such items in her home. A couple of times in the 39 years we have been married humidity has frozen a drawer shut on my wife's sewing cabinet. I approach that cabinet very carefully as I have never managed to build anything approaching the form and function of that work of art. Yet each time I manage to get the drawer moving again. Last year our youngest daughter inherited a similar sewing cabinet from a deceased aunt. I was thrilled to note it held a place of honor in her home. Everyone who enters her living room is greeted by a functional form which is beautiful. Now I do build a number of items. Many have been used in our home for decades. One even resides in my oldest daughters home. I always wonder if she gets the toy chest I built for her out and polishes it up just for me to enjoy. Her kids laugh at that thought and remind me Mother would likely skin them alive if harm came to her prized possession.

I say all of this in the hope that each who aspires to perfection can also enjoy the hard work of those of us who will never reach that aspiration. I will confess that I decided long ago to not post pictures of my projects as I found most folks who post here are far more advanced in their talents than I am. Still I continue to build and enjoy each finished project as much as those who are far more talented than I. Let us make sawdust. Jim

[Gene Howe]

Earlier, I said I enjoyed getting as close as possible. Whether or not that is "precision" I don't know.

My use of dial indicators and digital calipers is limited to machine set ups and measuring non wood parts. i.e. measuring the width of dado stacks, insuring blade, miter slot and fence alignment, jointer bed adjustments, etc. I sorta enjoy those processes.

The majority of my wood "measurements" are accomplished with 1.2.3 blocks, bars of key stock and drill bit diameters. Seldom use a tape measure. I find that modified nesting/sliding curtain rods give me more consistent results for inside measurements than a tape. And I've devised several little adjustable "Story sticks" to gauge and transfer smaller measurements.

The point of this ramble is to suggest that precision in machine set up is important enough to use the finest measurement instruments. For quality work and, above all, for safety. However, the distance from the fence for a router cut can be just a 19/32 drill rod, the thickness of a board coming out of the planer can be easily gaged with an open end wrench and, the width of a carcase back to be set in a groove doesn't require any more than an old set of curtain rods.

[pennview]

There's no reason to get up-tight about woodworking as precision is not that difficult once you make it part of the game plan.

Here's a simple check to help ensure your table saw is cutting wood squarely, that is, that the blade is perpendicular to the table and also to the miter gauge.

Make yourself two pieces of wood that you've jointed and planed square. I made these a bit ago out of a piece of scrap 2x4 because those I have been using may not convey the process as well. They're about 1 1/4 square by 12 inches long. They should last quite a long time.

Simply take a cross-cut a shaving of about the width of the saw blade off one end of each piece that was labeled so that one can recall the orientation when they are cut. I simply write "up" on the surface facing up when crosscutting the wood, but in a attempt to make it clearer I also marked "down" on the face that is on the saw's table, and "fence" on the face that is against the fence. After cutting the two pieces, remove any wiskers with a piece of sandpaper and stand the two pieces up on the freshly cut ends with the two "down" surfaces facing one another. Use the jointer table or plainer table (as I did). The irregular surface on the Shopsmith 510 table may make it difficult to do the checking.

If the blade is perpendicular to the table, there should be no gap between the two pieces of wood. If there is a gap as in the first photo below, you need to adjust the saw accordingly. The first photo shows my saw cutting less than 90 degrees.

Similarly, if you put the two "fence" sides together you can check if the miter gauge is perpendicular to the saw blade. This is shown is the second photo.

The third photo shows the blade is perpendicular to the table after a slight adjustment.

It really takes longer to explain than to do it.

If you have any questions, I'll try to explain this process more clearly.


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[JPG]

Am I correct in understanding that face you are marking "Fence" is the face against the miter gauge?:)

P.S. Am, I also correct in understanding you pass the workpiece(s) to the left of the blade?

[pennview]

JPG40504 Am I correct in understanding that face you are marking "Fence" is the face against the miter gauge?

P.S. Am, I also correct in understanding you pass the workpiece(s) to the left of the blade?

Yes, the face against the miter gauge is marked "fence" and at the same time, "down" is written on the face that is facing the saw table. (I actually forgo marking fence and down on the pieces of wood I use, but thought it would be easier to explain. I simply mark the up side to keep track of the orientation of the wood. Those two pieces of wood to the right of the pine in the third photo are what I've been using lately.)

And, yes, I'm using the left miter slot on the table.

Art in Western Penna

[foxtrapper]

All precision is "close enough". At some point, you declare the accuracy and precision of the measurements to be suitable. I.e., "close enough".

While it would be entertaining to get by table aligned to the head with an accuracy of 1/10,000", that measure would be completely unrepeatable as soon as anything was moved. Be it the table or the head. So, worrying about 1/10,000 would be a total waste of time as that precision would exist for only that moment in time.

The need for accuracy and precision varies. The tolerances of a thread are far different than the tolerances of rough framing. Placing glass in a window pane require accuracy and precision "close enough" to ensure the glass sits in the pane well and stays in place. There is no need for measuring it in thousands. That would be downright silly. Getting it within 1/16" is "close enough".

Use an accuracy and precision suitable for the job. Nothing less, and nothing more.

[mindpilot]

I knew I had passed the point of no return when I had the magnifying glass out so I could see the 1/64ths marks on the ruler.