Marble sanding beam for fret work?

[Chris Mudd]

Hello all!!!
I am to the point in my first re-fret where I need to level the frets. I can't afford the Stewmac aluminum bean, and it is my nature to try to make my own first.
I had someone at the local stone countertop supplier cut a piece of marble countertop to 16 inches by 2 inches. I am planning on sticking sand paper to the 2 inch wide side that is finished and use that to level my frets.....

Does anyone see a problem with this approach?

Chris

[Bob Gramann]

Is the marble countertop piece actually flat? I got a 1" piece of square steel tube from Home Depot. I cut a 12" length and sanded one side perfectly flat with sandpaper glued to a piece of glass. I then glued sandpaper to the flat side of the steel tube. It works great for leveling frets.

[Mario Proulx]

Check that marble for flatness. Countertop marble isn't ground for true flatness, but instead is ground for a high gloss finish.

I had a nice big slab of granite that I had inlaid into my workbench in my previous workshop, thinking I'd have a excellent hard, flat area for fretting, and reference work and such, only to be very disappointed when I was done, where I noticed that it wasn't anywhere near flat.

[John Sonksen]

What I use is a beam made out of Corian, it's got a flat section for the sandpaper, and another section glued on as a spine. Much more consistent than marble because it's manufactured. Does your friend work with Corian?

[Woodrow Brackett]

I use a 24" carpenters level with sandpaper stuck on it. Mine is decades old but I suspect you could buy one a one of the big box stores for $20 or less. I suppose, like alot of modern tools it might not be perfectly straight, so sight down it to pick a good one.

I had a nice big slab of granite that I had inlaid into my workbench in my previous workshop, thinking I'd have a excellent hard, flat area for fretting, and reference work and such, only to be very disappointed when I was done, where I noticed that it wasn't anywhere near flat.

Me too. Mines no longer in my shop.

[Al Dodson]

I am finding Several options for steel flat ground Stock 1/2" X 3/4 " X 18" for under $50. If that is within budget you can't do much better. This was just a quick check on the MSC website. It's possible places like online metals might be cheaper. We have a piece like this we call the preacher because he always tells the truth; mileage may vary.

[Randy Roberts]

Corian is about the last thing I would use for a dependable flat level of any kind. Unless I'm mistaken, it is just a resin/epoxy. It definitely creeps, and it will deform with minimal heat. I have a bunch that has been lying around in a box, and any of the pieces of any length at all have curved noticably from their own weight just sitting if they were not lying flat on other pieces.

[John Sonksen]

Corian is about the last thing I would use for a dependable flat level of any kind. Unless I'm mistaken, it is just a resin/epoxy. It definitely creeps, and it will deform with minimal heat. I have a bunch that has been lying around in a box, and any of the pieces of any length at all have curved noticably from their own weight just sitting if they were not lying flat on other pieces.

that's why I glued it up in a T shape, it seem to have stayed plenty flat. I dunno though, maybe you're right.

[Barry Daniels]

The T shape should add considerable strength and may be just the ticket to keeping it stable. I say check with an accurate straight edge and proceed from there.

[John Sonksen]

The T shape should add considerable strength and may be just the ticket to keeping it stable. I say check with an accurate straight edge and proceed from there.

Yeah Barry, what I did was make sure the spine was dead flat and then made sure to clamp the two elements together on another flat surface using corian epoxy. I made the spine double the width of the sanding surface and it seems very stable. I think as long as I don't leave it in my car or next to a furnace it should be fine.

Here's a pic:

[Mario Proulx]

That'll do it!

[Clay Schaeffer]

I also use a carpenters level. A light weight metal "I" beam construction with sandpaper glued to it. I sometimes think people get carried away with how "flat" the surface needs to be. Has anyone checked the uniformity of the thickness of the sandpaper we are gluing to our substrates?

[John Sonksen]

I also use a carpenters level. A light weight metal "I" beam construction with sandpaper glued to it. I sometimes think people get carried away with how "flat" the surface needs to be. Has anyone checked the uniformity of the thickness of the sandpaper we are gluing to our substrates?

I've never even thought to check the thickness of the sandpaper, although I kind of think I'll try and do the best with what I can control. I'm sure if I got out the laser it might not be perfect, but this kind of thing was just as easy to try and make flat as it would have been not to.

[David King]

If you have room for a real boat anchor you can order a granite surface plate from one of the many machinist supply houses in various sizes. These are very flat by luthier's standards but the shipping is often more than the cost of the plate. I picked up some white marble scraps and found them very easy to sand as the stone is quite soft. I was able to sand three of them against each other sequentially checking with prussian blue to see the results. They are now flat and very stable but prone to chipping if they drop. I use them to sand nuts and other small items. My longer sanding sticks are made from very dense Honduras mahogany, I've had them for a couple of decades and they've never moved. There are lots of ways to get a flat surface but I wouldn't be paying for precision ground flat stock if I could help it and I probably wouldn't trust it anyway.

[Chuck Tweedy]

I was able to sand three of them against each other sequentially

A subtle reference to the concept of "automatic generation of gauges". A powerful tool we should all understand.
It's also touched on here: http://en.wikipedia.org/wiki/Surface_plate

[Jason Rodgers]

I'm going to jump out in the middle of this, wave my stupid flag, and ask the question: how friggin' flat do we really need a surface to be?! Would a scrap of granite countertop be sufficient?

[Mario Proulx]

For your first question, well, as flat as we can have. Any deviation from true flat will only serve to to confuse you, right? So the real answer is: as flat as you can afford.

Onto your second question....

No!

A granite countertop slab may be as much as or more than .005" concave or convex, which would make it less than useless. Or it may be "perfect" when measured between 25" centers, yet had a .003" dip(or rise) in the area you use to measure neck relief(which we would like to hold to a tolerance of less than .003").

See where I'm going?

[ThomD]

I do have a couple of granite surface plates. They show up on local sites for very low prices, and some of the big box machinist stores also sell them for peanuts.

I use an aluminum carpenter's level for my sandpaper reference.

That said, wood is a great choice. The neck is wood and we expect that to hold tolerance. There are a lot of ways to level wood to granite specs in seconds, in a woodworking shop. Granite plates do not hold dimension, and have to be stored just so, and then have to be measured and certified regularly. You can't beat wood for cost, workability, stiffness, accuracy, and weight in the hand. But of course, we don't trust it right?

Gougeon Bros used to make wind turbines out of wood for GE and NASA. The tooling they used, was just plywood boxes with rebar in the corner, given the size. They made a wooden sphere for a helicopter flight simulator, a large object. It held insane tolerances, and was built on wood tooling. Miracle Fiber W.

[Mark Swanson]

ThomD, please know that we require the use of full names, both first and last. If you message one of the moderators, or post your name here we'll change that for you. Thanks!

[Chris Mudd]

So that settles it!
I have an appointment at a machine shop Tuesday to have a 1x1 steel tube machine leveled for a few bucks so that I know I have a good level.
THANKS ALL!