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I just finished my motorized sanding dish which works quite nicely and have a quick question regarding sanding the rims.

I'm building the stew-mac 000 kit which has you sand the linings with an angled stick thing. I need dishes for bandura building so I figured I'd use them to put the dish in the rims of this guitar too. As you can see from the photo, there's a good 1/8" to go to get to the linings at the waist.

1) Am I doing the right thing?

2) Do I need to do anything special to keep the neck block aligned or does that typically work itself out just by applying even pressure?

3) Am I going to have to trim my neck or something since there will be 1/8" less neck block at the top than what stew-mac was intending?


p.s. the belt is so long because I mis-judged how much extra I'd need.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

To expound a little more, the exact measurement is .140" to the rim at the waist. There's .060" to the top of the hole in the neck block for the truss rod.

It looks to me that if I continue, at minimum I'll have to enlarge the holes for the bolt on neck to allow me to drop it low enough and perhaps trim the bottom of the tenon a little bit.

Should I proceed?

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Andy my friend your motorized dish sander looks pretty slick - very nice job!

1) I can't remember if the Stew-Mac kits have pre-profiled sides or not. In any event, even if they do I doubt that they took the radius directly from a dish with a method like Colin's that uses the actual dish to transfer the profile to the sides. What radius is your dish? Anyway the gap that you see is not unusual to have when the sides have simply been cut and not pre-profiled. Also you know to sand the radius in prior to installing the kerfed linings right and then glue in the linings slightly proud 1/16th - 1/32nd" and hit it in your motorized dish sander again.

2) I am not real sure how well the Stew-mac cheap-arse waist clamp will hold up while using the motorized sander. Most people use a mold that supports the entire rim so be careful. In fact since you don't have an outside mold it might be a good idea to glue in the linings when you are getting close to rim contact all around. The linings will provide some additional support to the rim and help it keep it's shape. Nothing special is needed to keep the neck block lined up because the irregularities in the dish will be spread out, since it is spinning to the entire rim. For manual dish sanding, what Neanderthals like me do..... I flip the rim and mold 180 degrees every so often when I need to hit the dish with the shop vac to keep the dust from clogging the paper.

3) Your neck should be fine but the guitar's neck will need to be fitted which is part of building. Do you have a dovetail or bolt on? In either event some fitting is required once the neck block has the radius sanded into it.

BTW that sanding stick thing actually works pretty good although a dish is way better. One of the great things about Stew-mac kits is that you don't have to have an outside mold or sanding dishes.

Looking great Andy!

We posted at the same time.

OK you have a bolt on. With a bolt on neck with pre-drilled holes in the block it is not unusual to have to elongate the holes for the bolts and/or deepen the truss rod channel.

Just to cover this base the top has less of a radius than the back and I think, if I remember, the sanding stick thing has two radiuses too. You are using the lesser radius dish for the top right?

Hesh,

Thanks for the quick response.

The sides were not pre-profiled to a dome shape. The top part of the rims is dead flat. The back side probably has been pre profiled because it rocks when on a flat surface. The top dome is 25'.

Unfortunately I didn't know the trick about gluing the linings in after profiling the top. It definitely does make it a bit more solid though. I think I'll proceed then and if I need to, I'll remove and re-line if there's not enough glue area on the lining.

The neck is a bolt on with pre-drilled holes in the neck block. I think that if the holes weren't there I'd be in better shape. I'm not too worried though.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Yes, the top is 25'. The back braces are pre-arched to I think 15' but I didn't pick up a 15' dish as I didn't think it would be useful for bandura making (I only plan on making this and maybe one or two more guitars). I do have a 20' dome I was going to use for the back figuring it's close enough. I'll be bracing the back with a caul traced from the back braces.

The sanding stick also has two angles with the shallower one for the top and the steeper one for the back.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

You are doing fine Andy.

I think that Stew-mac even tells you to glue the linings on first but it's easier to sand the rim to profile without the linings, install the linings slightly proud, and sand again. The second sanding goes very fast.

Yes it would be easier without the holes pre-drilled then you could thread something sharpened into the neck and mark and drill exactly where the holes need to be.

Hows it feel to be building something with only 6 strings?

Andy, how far are you from your target depths at heelblock and tailblock? It may be possible to tilt the body slightly toward the tail as you grind, and close in on the waist gap without removing quite so much height at the heel.

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Dan
http://www.acme-archtops.com

So here's where I ended up. I measured the linings and in the waist they are .2" and at the neck they're .150" - I don't see any reason to re-line those areas.

I must say that using the dish for this is amazing. For my banduras, I started using a solera type of thing where the rims are flat but there's a dome in the soundboard. I never managed to get any decent results though and when I glued the domed top to the flat rim I'd lose most of my dome. My next bandura will use these dishes and I suspect I'll finally get the thing to hold a dome (I've got another couple tricks up my sleeve but those will wait for another post).

Enlarging the truss rod hole will be a pain - should I fill it and re drill?

Hesh - the first instrument I built was a backpack guitar I used to whet my feet a little before scratch building. I'd say that building a 6 stringer is roughly 10 times easier than a bandura, which has 60 strings, of course

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com