LumberJocks

Alaska Jim's Comments of the Day #9: Heading home tomorrow. Thoughts on digital devices.

  • Advertise with us
Blog entry by Jim Bertelson posted 01-20-2010 08:11 PM 841 reads 0 times favorited 16 comments Add to Favorites Watch
« Part 8: Maui - Day 8 - More photos and phun Part 9 of Alaska Jim's Comments of the Day series Part 10: Emergency router purchase - Bosch 1617 EVSPK - first impressions, and a surprise! »

Heading Home
We are going back to Alaska tomorrow. I am totally relaxed, and ready to go home. Itching to get in the shop. Never did get my router ordered, but that is not critical to make my sled.

Digital Devices
Upon reading a review, and commenting, on a digital angle gauge, I started a longer post, but decided it belonged in my blog. The topic of how to measure comes up periodically, but the advent of digital measuring devices adds a new dimension to the discussion. Anybody who has done woodwork for long probably develops his own techniques for measurements.

I am slowly accumlating an array of digital devices. All my devices are made by Wixey:

Wixey Saw Fence Digital Readout
Wixey Angle Gauge
Wixey Digital Caliper
Wixey Digital Protractor

The saw fence readout works well and has been in use a few months, very useful for duplicating cuts, or frequent resetting of the fence in increments.
The digital caliper is in heavy use, and I find it indispensible, and easier to use than an analog caliper, which I also own.
The angle gauge, as noted above, works well, but is not in heavy use.
The protractor has not been put to use yet.
I may buy a height gauge.

Accuracy and Precision
Here is a nice discussion of Accuracy and Precision
It seems easier to me to just read off a number from a device, than measure something as 3/32 and a little, or about 5/64. The mind has to work harder, and the memory process is then subject to errors. Any time I can use a digital device instead of analog with the same work, I do it. To be honest, I am not sure digital devices give me more usable accuracy, but it is easier to be precise. Stated more scientifically, I can get very close to the actual measurement with an analog device such as a ruler, meaning I can be reasonably accurate. Let’s face it, accuracy to the nearest 1/64 is almost always close enough for woodwork. But the digital device allows me to reproduce that measurement over and over, which is the definition of precision. Anytime something is easier to read, easier to remember, and can be reset on the same device or transferred to another device accurately, you increase precision.

I would suspect the most important thing is reproducibility, i.e. precsion. We frequently just need to be consistent to make good looking, nicely fitting furniture and other objects. Using stop blocks, story sticks, cutting everything with the same measurement at once, cutting on the same side of your pencil mark, etc, is more important than a digital device.

Pencil Marks
Pencil marks are always a source of error, and I remember years ago of falling into the trap of basing measurements on previous measurements recorded as pencil marks, and slowly accumulating significant errors. Now, I never base another pencil mark on a previous pencil mark.

I note that Incra is selling a set of marking rulers, Amazon link
I have a similar ruler made by General that sets on my measurement device tote. However, Incra has upped the ante with a T ruler and bend ruler using the same principle. They have small slots cut in them that exactly fit a 0.5mm mechanical pencil lead. That allows you to be very accurate, because you eliminate parallax errors, pencil width errors, etc. This should increase precision, because you make the exact same pencil mark elsewhere. But your measurement has to be a precise fraction down to 1/32 of an inch.

-- Jim, Anchorage Alaska



16 comments so far

View stefang's profile

stefang

13528 posts in 2054 days


#1 posted 01-20-2010 09:19 PM

Precision is an interesting theme Jim. What little precision I am able to muster up is the result of the many mistakes I have made over the years.

There are so many ways to approach the subject. For example, I often find that the actual dimensions aren’t as important as consistency ( I think you already said that). By using a marking gauge you can pretty much guarantee consistent marking in from an edge for example without measuring. If you are making aprons for a table with mortise tenon joints you can put the boards besides each other to see that the shoulder lines are all at the same place because if you measured your shoulder line from the end of the board and the board was just a little longer than the others it could throw the whole table out of square and prevent the the tenons from gluing up properly.

My point here is that we need to practice quality and measurement control as we step through our projects. There have been many many complaints about poor QC by manufacturers, but I wonder how well we practice it ourselves. I too own digital angle devices and calipers, but it would be very interesting to have a wide discussion on how different people ensure accuracy in their work and also the methods they use to mark and cut.

-- Mike, an American living in Norway.

View lew's profile

lew

10127 posts in 2475 days


#2 posted 01-20-2010 09:22 PM

Good information, Jim.

My biggest concern about the digital devices, available at “reasonable” prices, is their accuracy. I just purchased a Wixey digital “protractor” and rite out of the box, it is off by about .1 degree. I wonder how accurate some of the other devices are and how well they will retain their calibration.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View Dick, & Barb Cain's profile

Dick, & Barb Cain

8693 posts in 3019 days


#3 posted 01-20-2010 09:39 PM

Time sure flies while on vacation.

This reminds me of a house that my Dad helped build with some friends.

The guy that was the owner, had his brother cut all of the floor joists.

After laying out all of the joists, they realized that the rear of the building was 6 inches narrower than the front.

He used the last board he had cut, as a pattern for the next one, making each one shorter.

Those two brother were still friends, even after that big BOO BOO.

Whenever I drive past that house, I have to laugh about it.

I’ll bet the people who live there now, haven’t even noticed. <(:O}#

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN. http://www.woodcarvingillustrated.com/gallery/member.php?uid=3627&protype=1

View David Craig's profile

David Craig

2135 posts in 1829 days


#4 posted 01-20-2010 09:40 PM

Interesting topic, Jim, and one that has been a focal point for me this year. (BTW, glad you enjoyed your holiday. Nice when the holiday ends just right with an itch to go back rather than a pleading to stay longer :)

While the focal point seems to be on the digital, I have been making some changes and trying to utilize more precise measuring systems. I picked up a set of digital calipers and found them more useful than I thought I would have ever imagined a year ago. Also, the brass setup bars that are milled to exact thicknesses has been a time saver as well as an item that has drastically improved my accuracy. I had plastic squares when I first started and picked up a metal 6 inch and cleaned up a rusted old Stanley square from the early 20th century. It was not pitted on the blade and am much happier with the accuracy. I also added a miter layout gauge that is absolutely wonderful in the shop. It is L shaped and allows me to mark the cut line across the face of the board and down the edge for both 45 and 90 degree cuts. I can’t tell you how much that helped.

Not sure if anyone has checked them out, but you might want to go to the woodpeckers website. They have some beautiful marking devices (storyboards, t-squares, saw gauges, etc.) They are American made, ingeniously milled, and have nice slots for better accuracy when using mechanical pencils which, by the way, I have switched to from my old carpenter’s pencil (quantum leap there in accuracy).

Sorry Jim, not trying to take over your post :) Obviously this is a topic I can get excited about.

David

-- There is little that is simple when it comes to making a simple box.

View SteveMI's profile

SteveMI

867 posts in 2014 days


#5 posted 01-20-2010 10:39 PM

Jim,

Your paragraph with “most important thing is reproducibility, i.e. precsion” is the rule I live by and your examples are my norm. If all the relating parts of a build are the same, then the build is going to look good. Maybe the leg length tolerance cause the table height to be a 1/16” off, but it stands without a wobble, the aprons length aren’t to the original design tolerance length, but the top is square with flush tenons at the legs… If I know I am going to make several of the same and can’t make them all at once, I live by story boards and permanent stop fixtures.

On the other hand, I also have a wixey digital angle gage and several digital calipers.

I bought a used TS and the prior owner set it up fantastically. The tape readout on the fence is perfect to the face of blade.

My next digital device or trick to learn is how to repeatedly reset the blade height of the TS. After cutting a tenon I never seem to be able to cut the waste from sides the first time. Either shy or heavy by enough to frustrate me.

Steve.

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#6 posted 01-20-2010 11:19 PM

All
Went out fast walking for over an hour on the beach, the sand was hard packed and it was perfect for fast walking. Normally I don’t walk fast on the beach, but I had developed a blister on my foot, so it has been the beach for the last two days. Have to hit the tides just right to have good walking. Very nice out there today.

Mike
The habit of using a stop block for multiple cuts is one of the first things I did to increase precision in my projects many years ago. The radial arm saw fence with ruler and 10” stop block are the best illustration of how I put that principal to work. For those of you have haven’t seen that post, I implemented the concept there many years ago, and recently improved upon that implementation RAS Stop Block. Simultaneously I improved my accuracy with the fence ruler and its method of maintaining alignment. I still intend to make the alignment more robust, and make the fence digital.

But you bring to mind an important subtopic, with your discussion of joints. Products became affordable, and more complex, with the advent of interchangeable parts (see Wikipedia entry). It is interesting that the first use of interchangeable parts was a clock with a wooden mechanism. Interchangeable parts require both accuracy and precision.

I don’t think people doing hand work have that foremost in their minds, but it is none the less, sometimes quite important. Bascially you need the apron boards on the table, that you used as an example, to be to some extent, interchangeable, unless the design has asymmetric elements in it. As you point out, even the strength of the table will be dependendent on your measurements. So unless we are making a number of identical items for sale, or gifts, we develop a unique set of steps we don’t actually intend to ever repeat. Yet to some extent, we have to perform as though we are making interchangeable parts, at least for items that need durability, strength, and require symmetry. With one time hand made items, precision would seem more important than accuracy, as you pointed out.

lew
I would think that the protractor, which I think is specified accurate to 0.1deg is defective if it is that way out of the box. That is a calibration error, and I would probably return it. So far my Wixey stuff has been accurate, and if it wasn’t, I would return it. That is their purpose, accuracy.

I recently developed a simple little block to be placed in my miter slot on my saw, that would give an exact cut size with the fence backed up to it. With that I could quickly zero the saw fence digital readout with confidence. That is the whole purpose of the digital devices,accuracy, and if you can’t change the zero, then it has to be perfect out of the box.

Dick
Time flies, but you know, I am used to being active, and much of the time, vacation is down time for a recharge. So there comes a time that I am ready to go home.

The story about that house is too funny. But that is the equivalent of accumulating errors, measuring from a previous pencil mark, which I did many years ago. In the case of the joists, just measuring from the same one, over and over, would have been a much more correctable way to do it. Personally, I cross check by remeasuring after making the second item, to check for that exact error. Isn’t the reason experience is valuable, is that the experienced person has made more mistakes? (-:

David Craig
I too find that the digital calipers is the most used measuring device I have, although I have many squares, tape measures, rulers, etc, not one of them gets that amount of use. I use a small try square essentially as a marking gauge a lot. And the brass setup bars are on my list. I need to make a trip to the Woodpecker’s Web site, I have heard good things.

The little things like mechanical pencils, squares that are in good condition, rulers with marking slots, a good calipers, easily calibrated fences, all go to make better projects. And make the experience more enjoyable and less frustrating.

All
There is a lot of equipment in the average shop just designed to make things flat, square (perpendicular), accurate and precise. Simple measuring, of distance and angles, with a pencil and ruler or protractor, is one of the least accurate, and least precise things we do, and should receive a lot of attention….......I try to find a way to eliminate that method every time I can.

-- Jim, Anchorage Alaska

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#7 posted 01-20-2010 11:28 PM

Steve
Great example of the table that doesn’t wobble, again underlining that precision is more important than accuracy. I do everything I can do in a project to rely on precision rather than accuracy. Sometimes, the old trick of cutting that critical piece a little too big and bringing it to a perfect fit with plane, chisel, or sander makes the difference. The last little thing I did, making the box for my oven thermometer, I cut the sliding plastic top too long on purpose, and made it a perfect fit with the belt sander, since it was a unique part, and dependent on everything else. I didn’t rely upon accuracy, in other words I purposefully cut it too big, and then hand fit it. Accuracy is much more difficult, and much less reliable than the methods we use for precision.

Yup, my next digital device is a height measuring device, as well.

-- Jim, Anchorage Alaska

View richgreer's profile

richgreer

4524 posts in 1794 days


#8 posted 01-21-2010 12:35 AM

I confess – I am becoming addicted to digital measuring devices. I’ve been using digital calipers for some time. A few months ago, I purchased a digital height gauge and, as of today, I have the Wixey digital saw fence guide. To date, I have never been concerned about accuracy. I just remember to re-calibrate them regularly (virtually, every time I use them).

Recently I thought I needed a kerfmaker. Naw – with the accuracy of a digital caliper and my digital saw fence guide, who needs a kerf maker. What I do need is the ability to micro adjust my fence. I should have that resolved by the end of the day with a little improvising of my own.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1835 days


#9 posted 01-21-2010 12:51 AM

it´s someway sad that the time flyes so quick when you have great time in injoyeble company of fammily and good freinds so before you know it the end has come and seems that it was only yesterday that it startet

Dr. you seems to bee under an heavy attack from the dreadful disease of zealouslyworkaholiceager and the only cure is to step in a corner with the face inwards and sit down until the attack gets over

Ordred by Dr. von fiddle

you ain´t home yet and then already start aut with a great blog like this hmmm I have to read it a cople
more times before I can say anything my little funny thing that some call a brain isn´t on the top thise days

enjoy the rest of the day

Dennis

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#10 posted 01-21-2010 01:17 AM

Rich
I am definitely addicted. Back about 30 years ago, about 1980, I needed a light meter for my simple darkroom, to calibrate exposures. Remember you youngsters out there, once upon a time there was film….and dark rooms, and computers were primitive beasts, although I had two Commodore Pets at the time. My next computer, 3 years later, was an IBM XT with its 10 megabyte hard drive…....wow. I obtained a photovoltaic cell from whatever was the equivalent of Radio Shack in Fairbanks, Alaska, where I lived,and mounted it in some clear plastic, and used it to drive my hand held Fluke VOM to give me a number, from which I made a graph of exposure values for the paper I was using. Much cheaper than the analog devices out at the time, and actually more accurate. Moral of story…..still addicted to digital.

......and re kerfs, as noted in my blog on my infamous oven thermometer box, I made the kerf with my TS for the sliding plastic lid. Pretty easy to do with digital fence and all.

To make sure of your calibration, if you didn’t see my post, can’t remember where, about calibrating the Wixey Saw Fence Guide, try this:

Make a block of hard wood a few inches long that closely fits your miter groove on the right side of the blade, and projects above the surface of the table a half inch or so. Then back your fence up to the block, set it, and then cut a piece of wood. Measure it with your calipers and mark that number on the block. If memory serves me right, then if your Wixey fence guide is less than the size of the piece of wood, then move the fence negative the amount of error, and zero the Wixey. And move the fence positive the error amount if the Wixey says your cut was bigger than it was. This works better than butting the fence up to the blade, too much blade flex. I gives you a very definite number to adjust. And works for that blade. If you are using multiple blades, then make a block for each and label the block. Fool proof…....I think.

-- Jim, Anchorage Alaska

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#11 posted 01-21-2010 01:23 AM

Dennis
Actually, I am ready to go home. I have three whole days before I have to go back to work, and I hope to get in some shop time. Sounds like your virus is getting better. And I understand about the brain, sometimes it just refuses to be in charge, and sometimes it refuses to take orders!

Oh, and rethinking that darkroom story, I actually used a Heathkit digital VOM that I built from a kit, because it had red numerals and I could see it in the dark better….............

-- Jim, Anchorage Alaska

View Dennisgrosen's profile

Dennisgrosen

10850 posts in 1835 days


#12 posted 01-21-2010 01:37 AM

I know what you meening I still make some of the old fasion ind a darkroom and if I have to make pictures
for the web I have to borrow swambo´s digital

Jim I have to say goodnight it´s over midnight here and there is only 6 aurs to sleep before
work

see you

View NBeener's profile

NBeener

4806 posts in 1894 days


#13 posted 01-21-2010 02:05 AM

Steve wrote: “My next digital device or trick to learn is how to repeatedly reset the blade height of the TS. After cutting a tenon I never seem to be able to cut the waste from sides the first time. Either shy or heavy by enough to frustrate me.”

Had a similar problem with most of the tenons I cut for my current project. Talked with Big Brother (no … literally!). He suggested that I should use a miter fence clamp-down mechanism of some kind (he said that there are better things than to use a featherboard, in this application—things that apply more down force). He suggested that the couple of thousandths that remained on my tenons—usually in the form of ridges—were probably a result of slight warp or deflection away from the table or my ZCI, or that uneven and inconsistent downward pressure from my fingertips could yield an inconsistent result.

Made sense. I’ll also be shopping for a decent depth gauge for the router table and TS.

Jim: Agree. Great topic. I’m still so ‘nervous’ doing these projects that I have to remind myself to back away from the trees, and take a look at the forest. That’s a bit of an analog (no pun intended) to accuracy vs. precision. There ARE errors in some of these plans. I have to remind myself to sanity-check the numbers as I go along.

For the furniture endeavors in my life, I also switched from a 2B pencil to a 4H, occasionally invoking a utility knife. With MY eyes, I’m not sure I could find my line, if I used a ‘proper’ marking knife, but … for now … I see the improvements that the thinner marks yield.

I also bought a $15, 500 watt halogen work light You know … one of these:

When laying out marks for joinery, I find that there’s virtually no such thing as too much light, and that the mix of the yellowish output with my existing phalanx [“I’ll take ‘Obscure Military Terminology’ for $200, Alex] of fluorescents makes it easier for me to get better accuracy.

Glad you enjoyed your Aloha time. Thanks for taking us all along, and not sticking us with the dinner bill!

Hurry home. I feel a “7cm, fully-effaced, and crowning” coming on. That kid isn’t getting born without you ;-)

-- -- Neil

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#14 posted 01-21-2010 02:07 AM

Dennis
Good night, or if you see this tomorrow….........good morning (-:

Rich
I have a Vega fence, and it has a micro adjust, although some times I can just tap the fence right in to position. I would like to hear about your micro adjust solution. Sounds interesting.

-- Jim, Anchorage Alaska

View Jim Bertelson's profile

Jim Bertelson

3681 posts in 1884 days


#15 posted 01-21-2010 03:01 AM

Neil
Here I am reclining on the lanai, absorbed in my latest book, a novel evoking an atmosphere more akin to the great Russian novels, with nuances of romance, ethical and moral quandries…......Barcelona in the 40’s and 50’s, the hero near my age, translation from the Spanish, “The Shadow of the Wind” by Carlos Ruiz Zafon. Caressed, cradled in my hands, a seductive new medium, my Kindle DX, clothed in its fine leather case, lending its suave appearance and attire, to the alluring ambience of the author’s heady atmosphere. The sparkling scene of wind blown palms, white caps marching down the bay, the water and sky dominating the spectrum with brilliant blue, glass of wine in hand…...quietly enjoying the fine life….........

...........and the computer dings….again. This time it is….....inevitably…...........Neil….........

Great picture of the lamp….....I own one of those….....I’m enthralled. Literary images….....literary??!? of the bulging….......er…........er…....well…...........birth about to happen, transporting me to the antiseptic, crisp wonderland of the labor and delivery ward…............swell. You may wait in apprehension and foreboding for your birthday present from my imaginative….....perhaps better described as….....diabolical…..and devious mind….........

Where were we…........

......ah, depth gages…....let me know what you discover. I will make a perusal of the available mechanisms and Steve and I will avail you of our collective, piercing, and most critical wisdom, and we pursue parallel courses. Tell us after your purchase, so we may render your decision questionable, if not inadequate, and ignorant.

Thanks for the comment Neil…............................(-:

-- Jim, Anchorage Alaska

showing 1 through 15 of 16 comments

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase