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Message started by unkabob on Apr 10th, 2008 at 6:17am

Title: What do you use to measure while building
Post by unkabob on Apr 10th, 2008 at 6:17am
I use a steel rule 16 inches long and ruled in 1/32"s and a (cheap) dial caliper ruled in 1/128's.
I had to borrow an 18 inch steel rule ruled in 1/64's to set my bridge.

Using the caliper depth-guage is always handy but I keep a calculator around to convert back and forth.

I suspect that everyone has used unorthodox ways for measuring special cases.


Title: Re: What do you use to measure while building
Post by Matt Blacka on Apr 10th, 2008 at 12:53pm
Hi Bob,

I use a 300 mm steel ruler for doing most of my measurements, with 1 mm markings. I also have a 150 mm steel ruler with 0.5 mm (0.02") markings. Being Australian, I measure everything in mm, and find it much easier to do it this way, as opposed to in fractions of an inch. Like you, I have to keep a calculator handy to convert numbers, but typically my conversions are mm to inches and vice versa, as most stuff in lutherie is specified in inches.  >:(

I also have a set of 200 mm digital vernier calipers. They cost me about $50Au, and I wondered if I would use them much when I bought them. Now that I have them, I would recommend to any luthier in the learning, that they are an extremely useful thing to have.

On a slightly different note, to thickness sand all of my plates, I have made a plexi disk on a lathe (about 150 mm diameter) and installed a centre pin through the disk. I stick sandpaper on them bottom, then put the disk into the drill press (wagner safety planer style). I have a bunch of squares of sheet metel and plexi, all of different thickness, that I use to set the stop depth on the drill press, so that I get the exact thickness under the sanding disk that I'm after. Then i work my way over the top of whatever I'm thickness sanding, until the whole thing is uniform. I can get the plates to uniform thickness within about 0.1 mm (0.004") all over using this method. Only problem is that you end up with swirl type sanding marks which have to be sanded off later (this is not too bad if the last thickness sanding pass is done with finer grit sandpaper like 180), and you have to be careful not to let the spinning horizontal disk grab your plate and rip it out of your hands while sanding. However, it sure beats thickness sanding by hand for those of us without a thickness sander.


Title: Re: What do you use to measure while building
Post by unkabob on Apr 10th, 2008 at 6:22pm
I would find it easier using metric but I figure that you should stick to what the plans say, at least for the first one or two.

I have been looking at a digital caliper (200 mm) for about $25 CDN. Being electronic, it swings both ways.

Your thickness sander sure beats my early attempts using a belt-sander but a drum-sander is the right way to go. After you finish building one it is so simple (to build the second one). Mine uses 1/3 hp motor and is adequate in thin layers. Most people use 1-1 1/2 hp but I had a 1/3 hp and it works.

The first one is always the hardest.


Title: Re: What do you use to measure while building
Post by Don_Orgeman on Apr 11th, 2008 at 9:20am

My primary measuring tool is an 18 inch long stainless steel ruler graduated in 32nds for the first inch and 16ths for the rest.  The ruler also has metric on the other edge.  I also have several 6 inch rules graduated in 64ths.

When I want to get close measurements I have two calipers.  I usually grab the dial caliper graduated in 64ths first because I know the battery isn't going to be dead.  My other caliper is a Cen-Tech (Harbor Freight) 6 inch digital which read in both english and metric.  The problem with this one is I usually want to know the results in 64ths and it reads decimal portions of an inch, so I have to convert.

When I want to get accurate measurements on longer lengths (like nut to saddle lengths) I like to cut a piece to an optional length (such as 16 inches for a tenor uke with 17 inch scale length) using my table saw rip fence and then rip the board again to a couple of inches wide.  I then use this 16" board plus my caliper to measure the length.  As old age sets in my eyes can't easily pick up the lines on a ruler scribed in 64ths any more, but they can read the dial caliper with ease.

Harbor Freight sells a 12 inch digital caliper (number 47261) for $39.99.  I wish they had an 18 inch model available -- maybe in the future.  It would be great for us uke builders.  I see there are some 18 inch calipers out there, but the prices I have seen are all out of sight.


Title: Re: What do you use to measure while building
Post by unkabob on Apr 12th, 2008 at 7:12am
I agree with your opinion on the dial caliper being easy to read. I find the depth guage good for measuring between the saw-blade and the fence on my table-saw.

I keep a couple of 12 inch steel rules ruled in 1/32 that I picked up at the dollar-store. At that price its nice to have several.

The final measure of thickness is a micrometer which I inherited from my father. Moore&Wright may be gone but their quality still stands.


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