re-graduating a top and a back without opening the instrument.

[jazzjune18]

While we are on the topic of kids, I have a question of my own. I first started out building on kits, specifically the saga kit. And the very first instrument that built was very crudely graduated. And you can tell when you listen to it. Not having anything better to do this weekend I figured it might be fun to strip that instrument down and try to re-graduated, however I don't want to take it apart. Any suggestions on how best to do this? I will be sanding from the outside of the instrument and was thinking of sticking a light inside of there and just graduating based on the light that I can see through the instrument. Anyone have any good pictures or videos for reference? I know this will be very inexact since I can't fit a tool in there to measure but it might be kind of fun. Tips??

[MikeEdgerton]

Some folks have used scrapers put in through the end pin hole. I'm going to guess that might take some time.

[jazzjune18]

Mike, that's an interesting concept. Sounds like you might need to go to medical school to develop that ability. Jk Do you have any suggestions or references on gauging the thickness without actually being able to open up The instrument and measure the plates?

[MikeEdgerton]

http://www.stewmac.com/Luthier_Tools...ess_Gauge.html

http://www.howardcore.com/Catalog/to...ers&Gauges.htm

I believe there was a DIY Hacklinger gauge someplace here.

[Bernie Daniel]

While we are on the topic of kids, I have a question of my own. I first started out building on kits, specifically the saga kit. And the very first instrument that built was very crudely graduated. And you can tell when you listen to it. Not having anything better to do this weekend I figured it might be fun to strip that instrument down and try to re-graduated, however I don't want to take it apart. Any suggestions on how best to do this? I will be sanding from the outside of the instrument and was thinking of sticking a light inside of there and just graduating based on the light that I can see through the instrument. Anyone have any good pictures or videos for reference? I know this will be very inexact since I can't fit a tool in there to measure but it might be kind of fun. Tips??

I'd say based on my limited experience relying on light would be, like you suggest,a rather unreliable way, to assess the thickness especially because I think it would be hard to manipulate the light in a predictable manner inside the mandolin (I assume it has f-holes?). In the end, I think if you really want to do a re-graduation the easiest way would be to take the back off and go to it.

[darrylicshon]

http://www.stewmac.com/Luthier_Tools...ess_Gauge.html

http://www.howardcore.com/Catalog/to...ers&Gauges.htm

I believe there was a DIY Hacklinger gauge someplace here.

Wow i always wanted to get some gauges but for $500 i will have to put off buying a few things

[Ken]

If you are looking at controlled and specific re graduation I think the Hacklinger guages are the only game in town. Otherwise you are looking at "random hippie sanding".

[Bill Snyder]

The Hacklinger are old hat now. The MAG-ic Probe is the tool of choice of many professionals now. There have been a few threads here on the Cafe about it.
Of course for your needs JJ18 is is a bit costly.

[Dick Hutchings]

I wonder if the MAG-ic Probe could be used throughout the build process eliminating the need for a dial indicator.

[fscotte]

I built my own "magic-probe". Same essential electronics, free software to boot. The biggest issue is that calibrating the thing needs to be done precisely or you measurements will be off. If you buy the real Magic-Probe you are paying for the calibrating process to be done for you.

Here's the thread. Started off as a curiousity and ended up as a very useful tool. Much cheaper too. I have a few videos on refining it and calibrating it.

http://www.mandolincafe.com/forum/sh...hickness-gauge

[jim simpson]

If stripping the instrument is part of the plan, couldn't one regraduate from the outside?

[Dale Ludewig]

I wonder if the MAG-ic Probe could be used throughout the build process eliminating the need for a dial indicator.

You could use it for that but it would be a PITA. When the plate is accessible from both sides, a caliper is much faster. MagicProbe is great but all tools have their places. When you have a hammer, not everything is a nail, no matter what you might think.

[Jeff Mando]

Otherwise you are looking at "random hippie sanding".

Ya got me laughing there, Ken! I know a couple local fellas--60 somethings--who fit the description of "old hippies" -- they have often told me of getting stoned on Saturday night and then taking finger planes to the insides of their guitars and removing "excess" wood -- of course, they always tell me how it opens up the sound! They like to use 60's terminology in telling me they were able to remove about a "lid" of wood!

It is refreshing to know the proven designs of CF Martin and others can still be improved upon......

[MikeEdgerton]

...When you have a hammer, not everything is a nail, no matter what you might think.

I own a ball peen Phillips head screw driver.

[Roccus]

The late John Sullivan, from Washington state I believe, regraduated the top and back of my '84 Kentucky KM1500 from the outside using a gauge that resembled a bridge clamp with long arms. I think it measured the magnetic attraction through the wood. Unfortunately he's been gone for sometime.

[Ken]

Hey Jeff, nice to know the technique is still in practice. For mandolins random hippie sanding refers to John Hartford's and Norman Blake's work many years ago on Sam Bush's "Hoss" mandolin before Sam acquired it.

For whatever it's worth, I have thinned the tops and backs of two of my mandolins after they were put together. Can't say I re-graduated them because I couldn't really get specific measurements. Both of these mandolins are oval holes, one I did about 16 years ago, the other about two years ago. In both cases the tone was not where I wanted it to be, and I did feel that I had left the tops and backs too thick, on purpose, for different reasons. I did consider trying to use a light source inside the mandolin, to at least let me know if I was getting things too thin in any areas, but ultimately couldn't find anything that would fit through the sound holes. So my two main controls for how thin things were getting and when to stop sanding, were just visual inspection of the thickness at the edge of the sound hole, and by how the tops and backs were deflecting when I pressed on them. I did go pretty easy with the sanding, willing to quit sooner than I needed too instead of going too far. In any event, both mandolins came out of it sounding much better to my ears and neither have had any problems since. Not really recommending this, but I guess I do also qualify as an old hippie.

[Steve Sorensen]

MAGic Probe.

Steve

[Dick Hutchings]

That's going on my list of needed tools. I've tried sanding after the fact and ruined a nice back by getting too thin in one spot. Of course I could probably avoid that just by staying away from the re-curve and doing a little tapping as I go. Live and learn.

MAGic Probe.

Steve