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Thought I'd share!

I made an attachment for the rim sander that I made from Tim McKnight's plan of a Mario Proulx design (It's getting technical now!) Since the machine spins, I thought I would use it to make the dishes.

Here is the sled I used.



First I used my belt sander to get the disc absolutely round in relation to the axis of the machine.



Then I ran my router down the sled, slowly, as the disc was turning. I used a 1/2 inch up-cut spiral bit that I use for timber framing. After I did the intial pass I did another very light pass and then a very light hand sand with 120 grit paper. It works fairly fast and efficient. You might note though, that these pictures are taken outside, that is account of all of the dust that this process makes.

Anyway, here is picture of how I join the sled to the machine. DOWELS! This is a 25 foot radius sled.



Here is picture of the dog system I made to spin the discs. I used four posts but Tim used two and works probably just as well, I just thought four would keep the thing balanced better.



This last picture shows the holes in the bottom of the dish.



After I spun two dishes (one for the sander and one for a go-bar deck) I put two coats of Varathane diamond coat on them. THis weekend I will make a sled for the 15 foot radius back dishes and spin those. Once set up the process goes fairly quick and works very well with clean and accurate dishes resulting.

Hope this inspires you to try it!

On another note, I have an associate that I told about this process and he feels that we should make this rim sander, with some modifications, overseas. If some of these specialized machines were produced commercially for a reasonable price, would there be any interest in them?

Thanks

Shane

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Canada

That's pretty slick Shane! What speed does it spin the disk?

Any idea what the price would be if you had these mass produced? If the cost was reasonable it seems like it would be a welcome addition to any luthiers shop.

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Dave Rector
Rector Guitars

Shipping would be steep on these wouldn't it?

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

Dave, my disc spins at 136 rpm. THe 1/2 horse motor I use seems to handle the dish just about right. With a firm crip I could stop it but I can bear down a lot before it starts to bog down.

As for costs for the finished machine, I would need to work all of that out. My associate also wants to produce small CNC machines at a reasonable price for instrument making. So, we see the price of edge sanders in the $400 to $700 range. I am hoping that these would fall into the same but this is pure speculation, we may be able to get them cheaper! If there is interest I will get started at figureing things out!

Shane

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Canada

Shane,
Yeah, I'd be interested. I'd also be interested in the CNC machine, provided it was cheap enough. Man, those thing are expensive.

Shane, do you have a pic of how you set up your pulleys? I'm assuming that you used a 1725RPM motor and then used pulleys to get it down to the slow speed.

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Dave Rector
Rector Guitars

Dave,

I posted a bit of a discussion on how I changed the gearing from Tim's on this discussion:

Rim Sander

The post should have the details you want. Tim and Mario Proulx have some concerns over using a washing machine motor for fear of igniting sawdust on start up. I don't share those concerns but would suggest that maintenence would include ensuring good electrical connections and keeping the motor clean (blowing it out regulariliy). So with these motors you can start with 1140 rpm (using the slow speed terminals). My 2" to 6" to 2" to 6" gearing gives me 127 rpm. I calculated Tim's from his plans and he is at about 155 rpm or so. So that is the rpm range you are working towards. I also used 5/8" cold rolled shaft rather than the 1/2" hardened shaft that Tim used. The system I employed for keeping the belts tight is quite simple and results in all belts coming tight by turning the bolt at the back of the motor. I works very well, I am quite happy with how it turned out!

Good luck and feel free to drop me a line if you want more information.

Shane

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Canada

[QUOTE=Brock Poling]
Shipping would be steep on these wouldn't it?
[/QUOTE]

Brock, I have recently been checking into shipping from China. Believe it or not, it is cheaper to ship a container from China to your door than to ship an equivalent amount across country. The secret is to fill the container (either 20 or 40 feet in length). By the time you pro rate the amount of each unit in the cost of the manufacturing, it is reeeaaallly cheap.

Steve

[QUOTE=Dave Rector] Shane, do you have a pic of how you set up your pulleys? I'm assuming that you used a 1725RPM motor and then used pulleys to get it down to the slow speed.[/QUOTE]

Getting back to the idea of China making these, it should be spec'ed out with a gearmotor and variable speed drive, I think it would be cheaper than the jackshaft idea and would avoid certain problems associated with slip (and the need for adjustment) in the current setup. I know that a jackshaft is cheaper to do at home but it is relatively complicated and time consuming (read: expensive)from a production standpoint.

Think of those worm gear boxes as part of the Jet et al metal-cutting band saws. That and a variable speed drive would make the unit very versatile.

Just a few thoughts, Steve

Exactly Steve!!

That is just what needs to be engineered when I consider moving this from a backyard shop (even a big nice one) to a production process. I just need to get a sense of the desire to have one of these machines to get a feel for whether this is worth pursuing. I think I have access to the production facility and the desire is there to produce the machines if there is a market. So I was also wondering about binding machines, fret slotting machines, fret board radiusing machines, or even a combination machine that does a number of these operations, kind'a like a Luthier's Shopsmith??!!

I think I will get more details on this over the next few months and come back with more detailed suggestions.

Shane

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Canada

I think it's a great idea and you're sure to sell a bunch of them. You might want to give some thought to other uses for them, maybe with different sanding surfaces for different applications in non-lutherie ralated areas (ok, so I don't have a clue as to what they might be). If you can broaden your market you'll obviously sell more.

You might want to also factor in royalty payments to Tim McKnight & Mario Proulx seeing as you've already aknowledged that you used their plans and design - you're wide open on the IP issue.

I suspect that the spinny thing that would be produced in a factory would bear little resemblance to the spinny thing that Tim, Mario and I have, except that it will be another spinny thing. We would try to keep ALL costs down so that all you guys could afford to buy them!

Shane

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Canada