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Articulated sanding arm

Here are the guts of an articulated hollowing rig I made, using 3 ball-bearing hinges (one hidden) and ordinary lumber. It attaches to the tailstock through the hollow quill. You could add more links for increased versatility, and for sanding, conventional door hinges would likely be satisfactory. You might even be able to attach the sander to the last link.
 

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Outstanding idea, robo!!!!!.......:D

This might be a time to consider an industrial electronic robot arm.....something where the movement can be calculated and programmed into the arm rest. Looking forward to seeing what other ideas result from the basic concept. I'll bet your idea takes off......and flies! :cool:

-----odie-----
 
Reed, I will try to contact you later today about possibly showing this at the Turning with Physical Challenges session at the AAW Symposium in Kansas City.
 
Alan, I will be in and out all day, e-mail is best. I can bring it with me to KC.

If my bowls were round, then a programmable arm might work, but far too much money/complexity.

robo hippy
 
To replace your lazy susan bearings you will need thrust bearings. They are available at McMaster Carr and others for not much money. They can be had in a bore size of 1/2" - 2". You will also need a thrust washer on each side of the thrust bearing.
 
I was going to suggest using yoke type elbow joints with a standard ball bearing at the top and a thrust bearing at the bottom. However, Joe Griener's idea of using ordinary hinges is outstanding from just about every perspective and the cost can't be beaten.
 
I have used (2) steady rest extension arms fitted together so they articulate
as a rest to support my hand and a sander on a deeper hollow vessel.
 
Mike Johnson said:
I have used (2) steady rest extension arms fitted together so they articulate
as a rest to support my hand and a sander on a deeper hollow vessel.
Click to expand...

If you can manage it, Mike........I'd love to see a photo of what you are describing here. :D

Just like in keeping the lathe tool rock steady through an arc, the same applies to sanding.....both with powered sanding, AND hand held papers.

-----odie-----
 
Oh yea, one final thought on this... This is part one for the ultimate bowl sanding set up. Part two is finding the ultimate sander. We use drills which don't handle being used as grinders very well. I want one that I can't wear out every 400 bowls or so... The idea would be to mound the sander on the end of the arm. Thoughts include a cordless drill which should handle being used as a grinder, but would need to be hard wired rather than having the heavy battery on the drill. The speed ranges seem to be fine. According to a friend who can fix just about anything, you should be able to take a charger and the charging end of a battery and hook them up for continuous duty. No idea if a cordless drill would be able to withstand continuous duty.

A flex shaft would be another option. The Fordham (or however you spell it) flex shaft set up will run a 3 inch disc, but let's face it, it is made for smaller carving bits, not continuous duty 3 inch or even larger discs. So, for a flex shaft to work, it still needs variable speed from 100 to 1000 rpm, and a bigger motor...

Mounting the flex shaft head on the end of the arm would also pose a few problems. You need 3 axis pivoting universal joint to mount it on....

Still trying to figure this one out.... I know there is a solution some where....

robo hippy
 
robo hippy said:
Oh yea, one final thought on this... This is part one for the ultimate bowl sanding set up. Part two is finding the ultimate sander. We use drills which don't handle being used as grinders very well. I want one that I can't wear out every 400 bowls or so... The idea would be to mound the sander on the end of the arm. Thoughts include a cordless drill which should handle being used as a grinder, but would need to be hard wired rather than having the heavy battery on the drill. The speed ranges seem to be fine. According to a friend who can fix just about anything, you should be able to take a charger and the charging end of a battery and hook them up for continuous duty. No idea if a cordless drill would be able to withstand continuous duty.

A flex shaft would be another option. The Fordham (or however you spell it) flex shaft set up will run a 3 inch disc, but let's face it, it is made for smaller carving bits, not continuous duty 3 inch or even larger discs. So, for a flex shaft to work, it still needs variable speed from 100 to 1000 rpm, and a bigger motor...

Mounting the flex shaft head on the end of the arm would also pose a few problems. You need 3 axis pivoting universal joint to mount it on....

Still trying to figure this one out.... I know there is a solution some where....

robo hippy
Click to expand...
Why couldnt you just take battery off drill and run wire from battery to drill
 
Correct me if I am wrong, but you wouldn't necessarily need to start with a curved rest like yours, would you? Or is that an important feature for the design?
 
Lots of 'experimenting' still ahead on this one. One thing for sure, being able to spin the bowl by hand has become standard for my sanding since the arm holds all the weight of the drill. The 2 arm design allows for both inside and outside sanding.

robo hippy
 
Have you thought about using brass or bronze sleeve bearings? Especially for connecting the lower (outside bowl) section. It is the same concept as a hinge, but you get the full 360 movement. You would probably have to add a piece of steel to one of the arm rest sections to set the sleeve into, then the other section would just attach to a post or bolt without full threads that goes through the sleeve.

For the other question of grinder or sander, has anyone ever used something designed as a sander for sanding bowls? I know there are 3 in air sanders and a few dedicated 3 in sanders on the market. There is a 3 in metabo sander that costs around $150. I know it is more expensive than a drill, but if it is designed to be a sander it might last longer in a dusty environment. I'm a relative newbie and new to this forum so maybe this has been addressed before.
 
robo hippy said:
.... According to a friend who can fix just about anything, you should be able to take a charger and the charging end of a battery and hook them up for continuous duty. No idea if a cordless drill would be able to withstand continuous duty....
Click to expand...

It only takes an hour or so of heavy usage to run a battery down, but it takes 4 - 6 hours to charge the battery. This says that the charger doesn't have the necessary current output needed. Additionally, the voltage output of the charger is somewhat higher than the battery voltage. The charger voltage isn't nice clean DC like the battery, but is unfiltered half-wave AC. I think that I would let your friend do this mod on his drill and see how things go before doing it yourself.

The situation is even worse if talking about a high speed charger because the voltage is much higher than a standard charger.
 
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