Official Luthiers Forum!

[QUOTE=L. Presnall] Don, a hand drill? Elaborate...I'm curious but my Alabama education is getting in my way again!! [/QUOTE]
Larry, just your run of the mill shop power hand drill. Mine is a Chicago Electric from Harbor Freight "3/8 chuck. It has variable speed but it is easier to use a router speed controller like the one John Hall ships with his bender.

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Don Atwood
Arlington, VA

So a hand drill to POWER the dish? Is that hefty enough?

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http://www.presnallguitars.com

Oy, no! Y'all are severly underestimating the power requirments of this thing. That is 24 inches of sandpaper sanding hardwood. Lotsa friction.

I'm running a 1/2 horse with 16:1 gearing and find it lacking power.

Not to mention what trying to spin a heavy dish would do to your drill and its bearings. Then think of what would happen if you do get it up to speed, and it grabs something? Or the chuck comes loose?

Guys, think things through. Please.Mario38605.9440162037

Mario...got a photo?

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http://www.presnallguitars.com

[QUOTE=Mario] Oy, no! Y'all are severly underestimating the power requirments of this thing. That is 24 inches of sandpaper sanding hardwood. Lotsa friction.

I'm running a 1/2 horse with 16:1 gearing and find it lacking power.

Not to mention what trying to spin a heavy dish would do to your drill and its bearings. Then think of what would happen if you do get it up to speed, and it grabs something? Or the chuck comes loose?

Guys, think things through. Please.[/QUOTE]

Listen to Mario, I got the idea to do this about 3 weeks ago. I used a heavy-duty Makita drill, One of those wrist breakers when it gets hung on something. It would spin the dish fine about 150 rpm, and had plenty of torque. BUT once that 24" 1 inch thick plywood disc started spinning I had no choice but to hold on until it stopped turning and it don't stop none too quick with the reduction on the drill + the weight of the dish. I didn't think this through and could have had a less than pleasurable experience.

Safety Rule Ignored = If it looks Unsafe, It probably is.

Geez, you mean you guys were talking about holding the drill! I thought you meant mounting it under a table or workmate or something and just powering the dish with it...I see why the warning now Mario and DL...I'll probably just break down and build one right someday....another rule..."if it sounds too good to be true..."

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http://www.presnallguitars.com

Ya know, this rig is not hard to build. I appreciate John K.'s comments about the neat job inside with no glue and all (thanks John), but I am pretty handy with the biscuit joiner, a drill, screws and plugs. You can make a pretty clean and very strong box with mdf with just glue and clamps. I used glue, biscuits and air nails just because it was fast and easy and have them. Unlike Tim, I didn't have a bunch of bits around to make this, so, aside from the donated motor and a few bolts I had to buy the rest.

In Canadian dollars:

5/8 cold rolled shaft - $8
A box of bits (Blocks, pulleys, belts, etc) - $112
1 Sheet 3/4 MDF - $35

The rest was shop scraps. Where I live that is about the same price of a decent drill and motor speed controller. I have spent a lot of time in the past building things that "will make do" that tend to stay around a lot longer than planned and you just accept their pit falls.

Although my machine isn't quite finished I already know it will work well. Mario is right, I have to layers of 3/4" MDF laminated and routed into circles for the discs and they are heavy. I only have a 9 to 1 ratio on speed from my 1/2 horse motor because I am using the 1140 rpm setting. I will let you know if it is enough in the next few days, but I can't stop the shaft with my hand!

So think about the long term and build or adapt something along these lines. If space was an issue I think you could build this right into the underside of your bench and then change the chuck arrangement for the shaft so that it terminated below the bench height and then having some sort of plug that lifted out of the bench top to access the shaft. Heck!! My shop isn't even built yet, I have been cutting timbers for it for the last three days so this unit will live in the basement until the shop is done!

Anyways, whatever you do, please be safe and ask those who have been down the road before if you need any help, I did (thanks again Tim!) and I will gladly now help anyone else!

Shane

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Canada

My 24" MDF discs are doubled, too and it is heavy. I just finished sanding my rims yesterday, by hand, and I don't think I want a motorized sander for this. The weight of the double discs made short work of the job and to my inexperienced eyes it did a great job. I just twisted the discs in a circular motion, attached the kerfing and repeated the sanding again when my kerfing was dry. It didn't take any time at all, and very little effort. I have 100 grit paper on mine.

Ron

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OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

I agree about doing the twist; it really doesn't take much time. I did it that way for 50-60 guitars' worth, and it was done in the time it took for one song to go by on the radio.

I built the machine after I blew my back, and lifting the dish, much less twisting it, became impossible. What's that line about mothers and inventions? <bg> Holding a lightweight rim set to a spinning dish seemed like a way easier task. And it is. But....

Point being, if you only do a few guitars here and there, and are physically capable of doping so, sanding by hand is a great and plenty fast way to go; lots of control, too.Mario38607.0282407407

Sensible advice,as usual, from Mario. I think that we have a general tendency to over-engineer our solutions. Sometimes the low tech way is the right way to go.

When I built my last lute I did the whole job from start to finish with hand tools only, no power tools allowed, not only did I get the best feeling for the material ever, but the job was very satisfying. OK, not a solution for the luthier trying to make a living, but for the hobbyist great fun. My next project the copy 1700 Stradivarius will again be hand tools.

Just rotate the dish by hand if your not into production.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Had another thought! I think that is two in one day, I better quit while I am ahead!!

The other reason I built this machine was because I want go-bar dishes to brace the top and the back and was looking around at all of my friends trying to decide which one I was going bury in MDF dust will they spun the MDF disc as I lowered my router on a sled into it. It occurred to me that I actually quite like all of my friends and decided that if I built the machine (which I planned to do someday anyway) then I could use it to spin the disc's as I rout the dishes and spare my friends of the great joy of clogged sinus' and eyes. Once I get the bugs out of the first one then I am set to make any radius dish I want in about one eigth of a sheet of MDF and about an hour!

Shane

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Canada