Measurement thoughts

[Ken S]

Mike raises an interesting thought about the difficulty of seeing precise measurements.  I ran into the same situation when I was learning how to mount photographic prints and cut the openings in over mats. When people inspect a matted print closely, any miss measurement becomes very apparent.

My solution was not to measure.  By that I mean not to use a rule with a scale any more than necessary.  Story sticks are a very good step in the right direction, but only a step.

In the machinist/toolmaker world, gage blocks are a common tool with uncommon accuracy. They are often called Jo blocks, Swede blocks, or Hoke blocks ( they were invented by Johansen and Hoke.) Johansen made the first very expensive blocks in Sweden.  Hoke devised a was to mass produce them in the US.

Woodworkers don't need this laboratory precision.  The use of an open end wrench for "measuring" the diameter of round tenons turned on a lathe works very well and very consistently.  (Mike, borrowing your term, "Braille" measuring.)

Tormek uses the same concept with the three tool projection slots in the TTS-100.  The same tool allows setting the USB distance consistently with no measuring.  I have long thought regular chisel sharpening would benefit from this approach.

"gage blocks" do not have to expensive.  Hardware stores carry steel blocks for motor shaft key ways.  They are very inexpensive and more than accurate enough for woodworking.  A half inch today or next year with no measuring.

Once a combination square or set of calipers is set, the dimension will remain consistent.

This post could be a lot longer.  I think everyone gets the basic idea.

Ken

ps Lee Valley sells a very nice, inexpensive (at least for those of us who line in North America) desk light with a built in large magnifying glass.  I would think such a lamp would also be available in Norway.  We certainly don't have a monopoly on older eyes in this part of the planet!

[Rob]

Jeff already recommends the use of gauge blocks in usb distance from wheel setting for repeatable configuration with different tools ie to preserve the bevel angle.

I picked up his theme and cut my own using a good quality 1/2" ply (because its stable).  And now when for example I need to set the usb from "hole A" for my bowl gouges to a 3/4" roughing gouge, I simply wack the gauge block in the gap between wheel and usb and tighten...really simple.

I have a custom gauge block for each different tool.

My experience is that you really can get very accurate results with wood if you're extremely careful...obviating the need for expensive metal shop bought goods. Certainly for the purposes of this kind of application anyway.  When cutting gauge blocks it really isn't difficult to get 0.1mm accuracy just hand planning the edges of the ply with a block plane after machining close to that.  That's easily good enough for a gauge block and I agree with you Ken...they're a marvellously useful item to have around.

Similarly, I have separate outside calipers for repeatable spigot production set at exactly 50mm for my regular chuck jaw optimal grip setting.  I never use those calipers for anything else...they've become a permanent fixture.  I guess actually a 50mm wrench would have been a cheaper option for that :-)

[Herman Trivilino]

There are cases where an alternative to measuring is highly desirable when working with wood.

For example, if you have to drill a hole in a board in precisely the right location.  Or if you're mortising for a hinge or lock plate.

When I cut a mortise by hand for lock plate I'll attach the plate to the wood first.  Carefully cut around the edges of the plate with a sharp utility knife to mark its location, remove the plate, cut the mortise, then reattach the plate.

Of course, having sharp tools helps a lot.   

[mike40]

Very interesting post Ken. Gauge blocks are great. Another great way to use them of course is on the table saw, drill press,  Sliding miter saw, etc. for precisely spacing repeating cuts or holes. I have even used nuts as gauge blocks (not the kind you eat). These are probably not so very precise, but they worked for me. Most of my measuring mistakes are due to misreading rulers. The old adage about measuring twice and cutting once isn't a such bad idea. I do have a florescent lamp with a large magnifying glass. It is an essential aide which I use mainly with my scroll saw, especially while doing marquetry work where cutting accuracy is essential for a good fit and a good fit is essential for a good aesthetic result. Of course, getting a precise measurement and  marking it on a piece of wood is only the first part of precision. The other part is actually cutting and/or planing it accurately to that mark. This is where good routines and organization come into play to avoid errors like cutting on the wrong side of the mark for example and using shooting boards to increase planing accuracy, or like chopping mortises that could be a little inaccurate first and sizing the matching tenons to them to nullify any inaccuracies. I also do like Herman does, using actual pieces as templates for marking  to avoid measuring errors.

[Ken S]

Good point, Mike.  I believe good organization and routine is the key to accurate work.

As much as I appreciate the precision of Starrett and other machinist tools, fine, consistent work can be done with simple methods when well thought through and diligently applied.

Ken

[Herman Trivilino]

Good point, Mike.  I believe good organization and routine is the key to accurate work.

Not only accuracy, but efficiency, too.  I learned this when doing carpentry work for a living.  Good organizational skills can make the difference between a profit and a loss.

I think this is also relevant for hobbyists.  Many people give up on woodworking because of the frustration associated with errors.  How often do we have to start over on a complicated piece of joinery because we make a mistake?  Or get carried away when finishing and apply a coat before the previous layer has properly dried, ruining the work and forcing us to remove all the layers and start over.

These frustrations are part of the process, and we use them to learn and develop skills.  Many people will instead give up and try a less relaxing hobby, like golf!

[Rob]

for that very reason, if Im trying a new to me complicated procedure I always do a prototype to "load up" the skill and practice it before I apply it to the expensive piece of oak etc in the project.  It takes way longer than a professional might but the quality is pretty much guaranteed.

[Ken S]

One of the historic draws for the more expensive router dovetail jigs (Leigh, Keller and Omnijig) is the lure of being able to cut "forty drawers in an hour".  That sounds very impressive, however, since most of us will not make more than forty drawers in our lifetimes, what's the hurry?

I used to be amazed on the photo.net digital forum how many guys had racket up tens of thousands of shutter actualizations (I think that is the correct term.  We used to call it "exposures".)  These guys left Ansel Adams in the dust many thousands of actualizations ago.  For all their prowess, I don't recall any of their images.........

Ken

[Rob]

its the same in all technical endeavours isn't it Ken.  I'm a musician (guitar) and when my old band used to be out watching other guitarists play and he did a really fast solo that was all about ego and yet inappropriate for the song the term:  "Guitar wanking" was frequently used.

That extends to any technical discipline (though I now have absolutely no idea how this relates to this thread at all :-)

[Rob]

However....I can say that my kitchen global ultra sharp knives are about to get a right good weekends kicking.  My French sister and family are here in 5 minutes...this will mean most of Paris' finest will be packed into her car and that means:
Oysters
Foie gras
Finest Brittany Lobster (which is imported from Scotland apparently)
tons of lovely tapa style cured meats
massive beef toms
fresh shelled scallops
a case or two of the bubbly stuff

My knives are going to be in overdrive very shortly and I for one am looking forward to watching those suckers slide through a tommy tato like it isn't even there

[mike40]

The food sounds wonderful. I used to get lobster from the Shetland isles, probably where yours are coming from. The best I've ever had. Enjoy. Thinking about your knives, Have you used any of your Tormek bandages yet?  I have. I got my knuckle scrapped on the stone while adjusting the USB (I think). I may be the first person ever injured on a Tormek! I'm going in for an IQ test next week.

[Rob]

Oh no Mike you're in good company there.  I've cut myself many times, although,  not on the blades funnily enough.  It's almost always on the corner of the grindstone itself.

[Ken S]

Maybe that's the origin of the inside radius..... my tormek must be an earlier version; it came without bandaids, but with a tourniquet.

Ken

ps, Whenever I use the coarse grading stone now, I take a pass or two at the inside corner of the stone.  it's a micro radius which will grow to a small radius.

[mike40]

I'm glad to hear that I'm not the only one Rob. I guess I can cancel that IQ test, that is  unless you want to join me. I would think a musician would be extra careful with his hands.  As for the radius on the stone Ken, I am staying away from that for now. I have only one blade with a concave curved edge, an old scythe which I don't use anymore. As for the tourniquet, if the Tormek came with one I would never have bought it. BTW I had a devil of a time getting that bandaid out of the little plastic packet. I finally had to use my newly sharpened chisel to cut it out. And I was disappointed with the size. Finally something from Tormek to complain about!

[Ken S]

Rob and Mike,

I always thought the bandaid marketing trick was one of Tormek's lesser ideas. It sends the wrong message.

I have been reading David Charlesworth's third book.  (He is a member of this forum, but inactive for several years.)  I like his simple, but thorough technique.  Rob, you mention cutting yourself on the corner of the grinding wheel.  DC recommends restoring the bevels on the edge of (flat) water stones to keep them from chipping.  I believe the idea may have merit for the Tormek.  The next time I use mine, I plan to use the grader to knock the sharp edge off the outside corner of the wheel. Not a big radius, just making the corner a bit dull. I already have the start of a small radius on the inner edge (based on Jeff's suggestion).

DC also comments that once he dresses the wheel he does not move the universal support bar.  I was puzzled by his use of 9mm shims for the bar until I realized that that is the distance required to use the dressing tool.

I understand his thinking in not moving the support bar.  After dressing the wheel, the bar is aligned (parallel) with the wheel.  While he is correct in his alignment thoughts, it makes it difficult to use the Tormek for other than sharpening chisels.

Not using metric much, I didn't have nine millimeter ply handy.  I used the back of a 3/8" drill bit to try setting the distance.  I also tried using it as a feeler gage to check for parallelness.  I had uniform drag on both ends.  I was parallel.  However, in the process I discovered I had a slight crown in the middle of my wheel.  When my six inch rule was held against the edge of the wheel, the slight crown looked like the well formed slight camber of a smoothing plane.  Time to redress the wheel.

Actually, the 9mm distance can work well for chisels or plane blades with no camber.  The short projection length minimized the chance of finger pressure variance making the edge out of square.  It also minimizes the corrective ability of varying the finger pressure to correct the edge.  (We would call that "English" in the states, a more positive term than "French marks" from a hammer. )

Using a simple drill bit as a feeler gage to check parallelness between the grinding wheel and the support bar is an example of non measuring measuring. It is a good quick check of accuracy.  For longer distances, a set of inside calipers of a block would work.

Ken