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How to sand flutes?

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For quite a while now, I have been thinking about building a set-up to use a router to flute turnings. When we returned from Texas a couple of weeks ago, I was delighted to see John Lucas' excellent piece in the February issue of American Woodturner. That inspired me to get on with it! Here's is a picture of my rig, and the first bowl with 60 flutes added. I'm happy with the first one, and working on a few improvements already. However, I am looking for suggestions with how to sand the flutes. My hands are quite arthritic, and I am finding the process of hand sanding 60 flutes with 5 different grits to be quite painful, not to mention tedious. However I don't want to do anything too aggressive to destroy the crisp edges. Any ideas would be appreciated. Fluting Resize.jpg Fluted resized.jpg
 
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Keith, what John showed is one the best articles I've seen in the journal in a long time. This is the same way I do flutes on the CNC milling machine.

I suggest you change the router to a vertical orientation like shown in photo 22 of John's article. Use a router bit similar to a Grizzly #C1378 (I'm not recommending Grizzly bits, that's the quickest picture I found to show the style of bit). With the way you're currently setup the effective cutting speed of the cutter is zero at the very tip. With the vertical orientation the cutting speed is very high making a smoother cut needing less sanding.

Another thing is make a very light finishing pass cut. Have some sort of shim to space the router away from the pattern until the final pass. With punky or difficult wood I like to spray a sanding sealing prior to the last pass, that controls the fuzz a bit..

There's another thing which can be a little tricky so be careful. Add heavy weights to your router assembly so it doesn't slide too easily. With the heavy weighted router cut in the WRONG direction only on the light final pass. In machine work that's called a "climb" cut which gives a better finish. From experience most know what happens with a climb cut with a hand held router, the router has a tendency to self feed out of control. Keeping the final climb cut light combined with a heavy router will help keep things under control.

As to sanding, I use a flap wheel, that gets into the grooves without removing much detail.
 
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Thank you Doug - great suggestions. Reorienting the router as you suggest has a number of benefits that I can see. I'm going to give that a shot on my next bowl.
 

john lucas

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Re orienting the router so youncan use the outer perimeter of the bit does.2 things. It cuts cleaner but also eliminates the burnish mark you sometimes get in the dead center of the cove.
For sanding I wrap the sandpaper around a dowel.of the right size. If the flutes are large enough i have lots of sizes of sanding drums that fit in either my dremel or foredom. I've had them so long I don't know where I got them. Possibly from Rio Grand or from one of the carving catalogs. If I remember in the morning I will look and see if any of them have markings. I have done the entire flutes with these drums on some occasions.
 
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When I saw that article I was convinced that it is a poor way to use a router some of the problems I see are:
1) The router bases are too top heavy and don't provide enough stability.
2) The indexing method appears unsteady such that in all but the lighter cuts the work piece would vibrate.
3) The jam chuck holding the piece is extended too far from the head stock and tail-stock adding to the vibration.
4) The table surface and the bottom plate on the router base need to be polished for smoother movement.
The router bit suggested for the vertical mount is a 1 1/2" diameter on a 1/4" shank which is bad enough but having a router large enough drive it would amount to a terribly unstable mounting. Note in the article a dremal tool was shown.
 

RichColvin

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Keith,

In ornamental turning, one is taught to never sand the shape as it would soften the sharply defined edges. Sharp tools and light cuts are a must. This is an age-old wisdom

Sharp tools produce the least expenditure of time; surfaces so nearly finished as to require but very little polishing. Whereas blunt tools leave the lines and moldings less accurately defined, and the additional friction or polishing employed to gloss over the defects makes a bad case worse, and obliterates all the keen edges that would impart to the work a defined and exact character.

Ornamental Turning by J.H. Evans (1903)​

John Lucas’ advise is a good idea for making the light cuts.

Kind regards,
Rich
 
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When I saw that article I was convinced that it is a poor way to use a router some of the problems I see are:
.....................................................................................................................................................................................................................................................................
The router bit suggested for the vertical mount is a 1 1/2" diameter on a 1/4" shank which is bad enough but having a router large enough drive it would amount to a terribly unstable mounting. Note in the article a dremal tool was shown.

I didn't mean to use that exact bit, only one similar to it that does it's cutting at the outer radius for high cutting speed. I have several bits of that style that are much smaller diameter, some with 1/2" shank others with 1/4" shank. A Grizzly #C1268 with 1/4" shank would be ideal, we call those lolly pop bits. Other makers offer them in a variety of radius grinds.

I disagree about the lack of stability of a vertical vertical mounting for even a large 1/2" routers. Make the mounting's base as large as needed for stability, add weights for vibration dampening and more stability.
 
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Keith,

In ornamental turning, one is taught to never sand the shape as it would soften the sharply defined edges. Sharp tools and light cuts are a must. This is an age-old wisdom

Sharp tools produce the least expenditure of time; surfaces so nearly finished as to require but very little polishing. Whereas blunt tools leave the lines and moldings less accurately defined, and the additional friction or polishing employed to gloss over the defects makes a bad case worse, and obliterates all the keen edges that would impart to the work a defined and exact character.

Ornamental Turning by J.H. Evans (1903)​

John Lucas’ advise is a good idea for making the light cuts.

Kind regards,
Rich

Ornamental turning may not be a good comparison since flutes, etc are generated with small, narrow, sharp tools a little bit at a time. Here the issue is using a tool with the full flute profile taking quite a cut by ornamental turning standards. Having a lolly pop type cutter with helical flutes would ease the cutting load, but I don't think such cutters are readily available.
 

john lucas

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Don. You obviously havent tried my method. I have done an awful lot of pieces and all the things you mention are very minor problems if they even exist. Yes it's not perfect but most of us cant afford an ornamental lathe. I wrote the article because using the router is fun, gives people.a lot of options to add some surface design to their work, and its inexpensive.
 

john lucas

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Here are a few links to the sanding drums I like. You need easily replaceable paper. The mini drum sanding kits that come with sanding sleeves don't work very well. The sleeves don't last very long and are expensive. The kind I like have a removeable inner tube that locks a piece of standard sand paper in place. They should come with a piece of metal or wood that you use as a guide to cut the sandpaper to the exact size needed. I use an exacto knife and one of those rubber self healing mats to cut my sandpaper. I find the really big drums are fantastic for sanding the outside of larger carved pieces, not just sanding flutes. The bigger ones only come with 1/4" or larger shanks so won't work in the Dremel. Check the shaft size before you purchase to make sure it will fit your Dremel or flex shaft machines.
https://mountainwoodcarvers.com/collections/sanding-drums
https://www.chippingaway.com/cat/wo...cts-manual-and-power/sanding-drums-and-cones/
 
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Here's different flute type. This flute is "generated" rather than having the shape of a cutter. The size of the flute varies with the part diameter. The cutter was a small carbide saw blade with the tips ground to a 60 degree point. The wood is hard maple, very light sanding might be needed.

This was done on the CNC. With clever jigs it could as well be done with a router setup. The setup would be approaching the complexity of an ornamental turning lathe, only a little simpler. Back in the day furniture factories had mechanical machines to make parts like this. It was a matter of setting up jigs to control the cutter motion.

Flutes 1.JPG
 
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John, I use a Sand-O-Flex head. I feed fine grit abrasive out a little beyond the back up brushes. Sand lengthwise rather than rotating the part as you usually would with turnings. Mine is on a buffer shaft instead of the drill mounting as shown in the picture. I run it at low rpm's using a 3 phase buffer with a VFD for speed control.

About any flap sander that's not aggressive will work. It just happens I have a couple of old Sand-O-Flex's so that's what I use.

Amazon has this version of the heads I use, although I don't see any for buffer shaft mounting.

flap wheel.JPG
 
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3M makes a variety of radial bristle sanding discs, both in size and grit. They mount on mandrels of various sizes, depending on the disc size. The 1/8" shank mandrel will mount the 1" discs, which can be used singly, or as a "mop". Don't use them at high speed, as they will tear apart, and pay attention to direction of rotation when mounting them on the mandrel. Jewelers suppliers carry these.
 
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Here's a square fluted dish I did years ago, found the sample of a CNC production run in my shop cleaning yesterday. About 3-1/2" square. Meant as a mint dish for a high end restaurant.

Twelve flutes each side, using the John Lucas router method you'd need 6 different guide templates. Each contour is duplicated 8 times for a total of 48 flutes. It'll take a bit of effort to hand lay out the curves, CAD will help.

The same concept can be used to make other non-round shapes. Also offset centers work by moving the guide template in and out as the work is rotated.

fluted bowl 1.JPG


fluted bowl 2.JPG
 
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