Official Luthiers Forum!

I am going to finally break down and build a rim sander. I pretty much know what I want in terms of design and I broke out all the old threads on the subject and re-read them.

But one thing I was a bit unclear on was how big should the motor be? I read two conflicting things about Mario's (1/2 hp and 1 1/2 hp) and I am not sure I saw how big Tim's motor was, and IIRC Shane was using a 1/2 hp appliance motor. ... and I get the math on stepping down the RPMs.

I am curious about what you think of the motors you have and what you would recommend.

I can pick up a new Baldor 1hp 1ph 1725 RPM motor fairly inexpensively, but I am not sure if that is a good size.

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

I have a 1/4 hp on mine and it's underpowered but works. 1/2 should be fine. Appliance repair places are a good source for cheap 1/2 hp motors. I've gotten a couple for $10.

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http://www.chassonguitars.com

You will be gearing (probably with belts & pulleys) down your rim sander a whole bunch. With the decrease in RPM you'll get a proportional increase in torque. I would think anything over 1/2 HP would be overkill, unless you're going into high production mode.
Can you post some pics when you get the rig built? A rim sander is on my list, but it's still a long way down from the top.

I'm interested too. I tried the method of installing a lazy susan to the bottom of the dome and then rubbing it on something stuck into the drill press, and although it did work, this is not a permanent solution for me.

Keep us posted on what you come up with!

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Reguards,

Ken H

It may be more expensive after the drive/speed controller, but this would be an ideal application for a DC motor. Adjustable speed, constant torque, etc. By the time it's geared down I think 1/3 hp would be plenty.

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Eschew obfuscation, espouse elucidation.

It's important to do the following:

1. Use a 4-5hp motor, geared so that the speed of the dish is running about the same speed as a table saw blade.
2. Use 36 grit sandpaper.
3. You'll want a rig to hold the rim in place laterally so it doesn't go flying off when you start the sander.
4. Rather than holding the rim to the dish manually, it's best to load the rim, then set a board on it and put a 50lb weight on the board which will help apply even pressure around the rim.
5. Turn it on, and leave it for about 45 minutes...just walk away, and when you come back, the rim will be done.

This works especially well for Brazilian RW and other expensive woods.

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

You forgot the big chainsaw engine running at 10,000 rpms for the sound effects , just to let everyone know how serious about power you are Uuuaargrgh!!!

I used a 1/2 or 3/4 hp? Baldor with a gear reduction box and it is one of my favorite tools in the shop, works like a charm and is a magnificent time saver.

GG

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Gwaltney Guitars

Awesome... thanks guys (well... except you Don. )

I will post pics after I build it. Basically it is going to be a variant of what Tim is using. I am going to incorporate a down draft table into it so I can pick up as much dust off of it as I can

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Guys, I am trying to get my head around this and not trying to be a smart A.

So you set up and dedicate the floor space to a machine specifically designed to grinding just a little from the linings to give you a matched radius to the back? How many guitars are you building a year??

I know from first hand that it takes a wee bit of twisting and turning to do this by hand to the back of the rim with a radius dish, but it's really not that much of a big deal. As for the top of the rim it would seem pointless if you where flattening the radius from the soundhole forward and gluing an unradiused (is that a word?? unradiused??? only in lutherie...hey wait a minute, lutherie ain't a word either??) transverse brace, because you need to go back and regrind that area with a flat sanding board any how. I must be missing something or you guys are pumping out 5 gits a week and not posting.

Cheers

Kim

It sounds like you have some good advice so far. I ended up using a 3/4 HP motor with a right angle gear drive which works very well.

Please post your results once you get things figured out.

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Brad
Avon, OH

Kim, it does seem like over-kill doesn't it.....It's not though, not to me anyway, it would take a LOT of something to get me to trade this thing away, it's that important to my building.

GG

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Gwaltney Guitars

Definitely not overkill if you're building more than a few a year. Mine took about 3 hrs to build (including a long trip to the hardware store) and cost maybe $50. Saves me at least 15-30 minutes per guitar and, as Greg said, it's much more pleasant.

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http://www.chassonguitars.com

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Brock Poling
Columbus, Ohio
http://www.polingguitars.com

Not everyone really needs a motorized dish. An apprentice is a great substitute tool for this job. Plus, with a motorized dish you miss the enjoyment of getting to watch someone suffer.

Rosewood dust, settling on a sweaty forehead
Perspiration drips
from the tip of the nose
to the mushy dust pile on the bench

A cloud of dust
A sneeze
Sweat flies, like Rocky Balboa taking a punch in slow-mo
The dust cloud swirls

It's a beautiful day
85 degrees
"I'm heading Kosmos for lunch, you want anything?"
He curses at me under his breath

I check his progress before leaving
spin 20 rounds
lift and check
nowhere close

Face is red
sweat and dust have mixed on his arms and forehead
tone putty
I hope that wasn't a good shirt

I turn to leave, pretending to look indifferent
"Only two more sets after this", I say.
He doesn't see my smile as I walk out the door
I did it, so can he

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Eschew obfuscation, espouse elucidation.

Is that how you went from being a great guitar builder to a mini ukelele builder?

No, that's how to develop a line of slim-line electric acoustics.

Very slim....

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"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

I want to spend an afternoon at Lance's this fall and have him help me build one of his very cool manual rim sanders - the one with the handle that you turn around and around. This would be a big set up for me and let my love handles grow back.......

Kim bro I agree that it does not take a lot of time to sand the radius into the rim. It is not my favorite task though and usually takes me about 1/2 and hour and can be tiring to do - at least for me.

There are some things that one can do to speed this up regardless of if the builder is using a motorized jig or wrenching their back "driving the bus" as brother JJ puts it.

Sanding the rim in the dish prior to gluing on the kerfed linings was something that did not occur to me until guitar 3....... But it is way faster than trying trying to sand through the sides, blocks, and linings when you have a long way to go.

Also radiusing your sides prior to bending or at least the back with Colin's method using the piece of wood with a hole in it and a pencil to capture the radius from the dish always precludes the need to sand much in a dish for me.

And building the proper angle into the blocks can save time in the dish too.

I flatten my upper bout of the top too but I do so after radiusing the upper bout in a dish so that from the sound hole down there is a radius. That is the most time consuming part and needs to happen first. Then with the rim face down on a flat surface covered in 80 or 120 grit I shim the tail block up 1/8" and just move the upper bout back and forth. I make marks with a pencil on the kerfed linings from the neck block to the waist. When the marks are all gone the upper bout is flattened and so too is the neck block.

The first motorized rim sander that I ever saw, in pictures here on the OLF, was Brad's and it was about the nicest made jig that I have seen.

I watched my apprentice sand his rimset last night. Very relaxing to watch Wonder if I can get him to do mine for me.... He DID help put in my AC units

David C's DC motor is right on. But, 3/4hp to 1hp is what I plan to use. This thing takes up some real estate in the shop though. Brock's idea of using it for double duty is a good one. I'd like to see what you come up with. I have a good sized basement shop, but I try to keep the footprint down where I can.

Keep us posted Brock...

Very good David,

I can see why you would never want a motorised dish in your shop. It pays to keep the hired help in good physical nick with periodic bouts of aerobic exercise and a low risk task such as rim sanding keeps them away from nasty machinery and stuff when it would be most difficult for you to adequately supervise their safety whilst otherwise distracted luncheoning at Kosmos.

It's also nice to have a clear visual indicator, something tangible, of just where it is that your hard earned money is going, just be sure to provide a dust mask now and then. Why you could even use the mask as a feed bag filling it with oats before you head out the door. That way the good fellow could imagine share a meal with you while he happily toils away. This would no doubt do wonders both productivity and industrial relations within your workshop....Do you need a HR Manager??.

Brock,

I had to ask because as Hesh mentioned, I too used Colin Symonds method of pre-profiled the sides for the back and I trimmed the neck block fairly close with a sharp block plane, so there really is not that much "Bus driving" to do. But I do concede, I can see where doing this task by hand more than just a few times a year could become laborious unless like David you are using someone else's hands to get the task done.

Cheers

Kim

The new forum software seems to have something against me, and I cant seem to find the old threads on these sanders. Would someone who has better search skills than me be kind enough to post the links to the old threads where there were pictures of these machines?

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Reguards,

Ken H

I use a motorized rim sander, and I don't pre-profile the sides, or angle and trim-for-height the end blocks, and I haven't felt the need to extend my dust collector to my sander, because it runs so slow that the dust just seems to drop, without going airborn (I'm sure SOME gets into the air, but what does isn't visible, and I depend on the suspended air filter to grab that) and anyhow I'm usually across the shop when the sander is running, doing something else.

I use a double-reduction set of pulleys, shop-made of plywood, and a cast-off washing machine motor, 1/4 horse, and the reduction has so much advantage that I pile a little weight on the work to speed the cut; I've never stalled it. I realize I could have saved a bit of construction by using dc, but when I looked in Grainger's, my eyes rolled up into my head. Three or four hundred for the motor, and the same again for the speed controller - I assume variable speed is the reason for dc, but an ac gearmotor of the right speed is still over two hundred. Excluding the motor my parts cost way less than a hundred bucks, and every body has to buy the ply for the cabinet.

Take a look at the photo-essay on my website.

Dan

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

I built a removable motorized sander into my main workbench. The motor is permanently mounted to the side of the workbench near the back and the arbor with a small pulley pokes through the back corner of the workbench, so it doesn't really get in the way. The dish is attached to a base with a built in lazy susan bearing and it slides along the front edge of the workbench to adjust the fan belt. I machined a slot in the round base of the dish to accept the belt. The large radius of the dish's base and the small pulley on the motor shaft gives me a rotation of about 100 rpm. Let me know if you want more detail or a photo.

Mine has a 3/4 hp motor and it will not start with the loawd applied so I start it and then lower the side onto the dish. I can stall it by pressing it down with a little more force than gravity but gravity is fine for shaping the sides. One thing I do recommend is sort sort of way to guide the rim and keep it centered on the dish. I use 4 threaded rods that are just outside the circle of the dish and fit in 4 holes in my form. My forms are all rectangular so that I can drill these guide holes so you may have to come up with an alternative. I would also recommend keeping the speed of your dish, around 100rpm. I use 80 grit on the dish.
here is a link to a short video of my sander in action.
http://www.johnhowguitars.com/images/PC/Side%20Contour.WMV

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Tickle your guitar daily, and it'll tickle you back.

Broc,
I am using a 1 HP, 1725 RPM motor with a C-face mounted to a 15:1 right angle gearbox, wired for 220V which yields a final 115 RPM at the output shaft. I can put all of my weight on a 24" diameter spinning disc and can't stop the wheel. Having been down the belt & pulley reduction method previously, I would advise you or anyone considering that method to NOT use it. A right angle gearbox / motor combo is more robust, higher torque, far less maintenance and a LOT easier to mount and build up.

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tim...
http://www.mcknightguitars.com