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Oddy
26th March 2017, 08:45 AM
The kids want me to make them some puzzles. I know a few good ones but need to make some wooden rings about 5-6cm in diameter.
I'd like them to be rounded like a curtain ring, not a flat disk with a hole in it. Are there any good techniques (or chucking methods) for accomplishing this with standard tools?
I've seen those captive ring tools but don't want to buy anything for this project.
The way I have tried so far is to turn a spindle, make a deep bead, hollow and round the inside edge of the ring on the tail stock side, then cut away as much as I can on the head stock side to give me room to undercut the bead a bit on the head stock side and cut through to the hollow. (I finish with friction polish before cutting all the way through). I can't get a decent inside curve on the headstock side though so the problem then becomes how to chuck the resulting ring to finish the side that was previously towards the headstock. Best I could come up with so far was to glue a bit of sandpaper to a dowel and put that in the lathe and use it to hand shape and finish that inside edge of the ring - not ideal though.

chuck1
26th March 2017, 09:09 AM
This will call for some old fashioned friction chucking with scrafical timber , I usually use my 3/8 detail gouge
I have not got any photos sorry, maybe google turned bangles?

Skew ChiDAMN!!
26th March 2017, 06:05 PM
Another trick is to separate the ring & shut off the lathe. Either remove the half-done ring or, if you can't, tape it to the head-/tail-stock end of the spindle (in a balanced way!) then start the lathe and clean up the spindle. Turn off the lathe again, tape a bit of sandpaper to the spindle et voila! A mini flap sander.

This is pretty much how I clean and buff the captive rings on my goblets.

It does help a lot if you profile the ring(s) as closely as you can to the desired shape beforehand of course. Less clean-up directly equates to less chances of invoking a Murphy. ;)

Oddy
26th March 2017, 07:40 PM
maybe google turned bangles?
Thanks Chuck - I didn't think of bangles, but that search turned up some good ideas for holding the half complete ring. Not a lot of woodturning experience yet - still learning the tricks of the trade.

KBs PensNmore
26th March 2017, 09:20 PM
Another way to do it would be to turn and polish the outside and sides as you've done, cut through to the other side, trying to get as close to the finished size. Make up the quantity required, then make a JAM Chuck out of scrap wood. To make a JAM chuck, face off a block in the lathe, then turn the centre out to suit the smallest outside diameter (OD) ring, leave a small step so that it won't go all the way in. The reason for making it to suit the smallest OD is that you'll need to take it out a bit more to suit the next sized ring. If you've made it a bit to big, a few dabs of Hot Melt Glue will hold them in place. Turn the inside to a finish ready for sanding and polishing.
Hope this helps.
Kryn

rob streeper
26th March 2017, 10:05 PM
Sorby makes, or perhaps by this time made, special scrapers for turning rings.

woodPixel
26th March 2017, 10:53 PM
The bangle idea was an excellent one. I wasn't going to comment, but just follow, as the problem seemed like a real doozy.

Still, a bit of self research wouldn't harm...

This video goes a good way to showing a repeatable process:
http://youtu.be/EUD5oAyKFpQ

It still feels a little slow (good for 5) but I wouldn't want to make 50....

Still, a bit better than a captive ring, which still isn't a bad idea too.

Oddy
27th March 2017, 10:22 PM
I gave the jam chuck idea a go. I think this would work well for wider rings where you have a flat spot in the middle, but since I am trying to get a fully rounded inside edge on a smallish ring, it is very difficult to make this work. I got good enough results for a quick puzzle for the kids, but its definitely not heirloom quality.
The only way I can see to do this properly is to hold the ring from the outside. Maybe something like cole jaws with long posts to keep the ring away a bit from the face of the chuck and notches in the posts to seat the ring in. Maybe making a large wooden collet style chuck would work also. Oh well, I have enough rings for now. Maybe I will return to this problem in the future to see if I can do something better next time.

powderpost
28th March 2017, 07:56 PM
Try your nearest op shop, they often have curtain rings in bags for sale.

Jim

Oddy
28th March 2017, 08:46 PM
Try your nearest op shop, they often have curtain rings in bags for sale.
... but then I don't have an excuse to play on the lathe! :wink:

KBs PensNmore
28th March 2017, 11:19 PM
Oddy, do you have any metal working skills and tools? Basically need an angle grinder and a Dremel with a stone the diameter that you want the rings thickness to be. Get hold of a metal cutting blade that has broken, should be available from saw sharpening places, usually they get thrown out. (If you can't get one or bits let me know and I'll send some to you.) You'll also need a bit of 12 mm square bar with a 5 mm threaded hole for the handle. Have a look at the Sorby tool and basically copy the shapes with the grinder and Dremel.
If you don't have MW skills send me a PM and I'll see what I can find for you, :D.
Kryn

dogcatcher
29th March 2017, 10:17 AM
I would drill the center hole using a 4 jaw chuck and finish the inside of the circle,

Then I would make an expanding mandrel like this to finish the outsides of the circles.
http://i63.tinypic.com/2ntl839.jpg

To make the expanding mandrel, drill and tap a piece of wood too fit your lathe spindle. Turn it to the diameter you need. Drill and tap the front of the mandrel for a 1/2" pipe plug. Then saw/split the front part where the pipe plug threads are in 2 parts, so you have 4 "fingers". As you screw in the pipe plug it will expand the "fingers and hold the circles. Now you are ready to finish the outside of the circles.

You can make a similar expanding mandrel and use your live center to force the fingers to spread. Or use a thin cone shaped piece of wood and stick it in the hole at the pipe plug end.

Oddy
29th March 2017, 09:55 PM
Oddy, do you have any metal working skills and tools? ....
Thanks for the generous offer Kryn. Yes I do have some basic metal working skills and all the gear to do that - will have to have a go at making some custom tools for these sort of things.

Oddy
29th March 2017, 10:11 PM
... Then I would make an expanding mandrel ...
I like that expanding mandrel idea dogcatcher - a good improvement over straight jam chucking. I think that would work well to finish the outside of an item without marking the inside like my regular chuck with pin jaws would.
I still have the problem though of properly finishing the inside edge of the ring on the drive side. Maybe it is just my bad technique, or unsuitable tools, but I find it very difficult to get in there and make a nice rounded curve - if on the other hand I could hold it properly from the outside edge after separating, I am sure I could put a very smooth curve on it. Might not be a problem with a large ring, but I was trying to make small 5-6cm ones.

KBs PensNmore
29th March 2017, 10:12 PM
Oddy, if you want/need advise on them send me a PM. Where the screw goes I put a slot with the angle grinder, as it can't be drilled without special bits.
To help finish the inside, hold it in the jam chuck, have seen where a hose clamp was used to help hold it in place, and use coarse sandpaper to get it to shape, then finer grades till you're happy with it, then turn it around to finish the other side.
Another alternative is to make a mandrel, that can accept different grits and use that to do the inside rim.
Kryn

ozka
30th March 2017, 09:28 AM
What about just using a round over (radius) bit with guide bearing on the router to do the insides Could do the out side as well if desired.
e.g., turn a 20mm x 20mm square/sharp edged ring. Use a 10mm radius bit and round all for edges. quick sand, job done.

Oddy
2nd April 2017, 09:50 AM
What about just using a round over (radius) bit with guide bearing on the router to do the insides
Interesting idea.... this got me thinking of potentially using a round over bit like a scraping tool on the lathe - pre made quarter circle in carbide. Would just need a safe way to hold it.
I don't know about using a router on such a small circle - could be a bit dangerous even on a router table with something suitable to hold the ring. Could possibly do it this way if I bored out holes in a larger board then went round the holes with the router and a guide bearing bit, then cut pieces from the board. could then friction chuck or take the mandrel approach to finish the outside. Hmm another technique to add to the growing catalogue :)

dogcatcher
2nd April 2017, 10:14 AM
Make a similar chuck to the expanding mandrel I described above But make it a 4 jaw collet chuck. Use a hole saw to cut your circles so that they are exactly the same size each time. In the end of your 4 jaw collet chuck, drill a hole 1/2 the width of the blank for the blank to fit. Use a hose clamp to force the 4 "fingers" to hold the blank. You can finish one side of the inside, flip it and do the other side. Then use the above expanding mandrel to finish the outside of the ring.

dogcatcher
2nd April 2017, 10:24 AM
Or, take a flat board, about 8" square. Drill your rings using a hole saw, drilling both the outside and inside rings leaving it rough size. In the center of the 8x8, drill a hole with the outside diameter of the rings. With a saw split one side into the hole, clamp pressure on that saw kerf should hold the ring in place. Then use a router table with a round over bit to do the inside, then finish the outside with the expanding mandrel.

woodPixel
4th April 2017, 01:23 AM
I stumbled across this idea:
http://youtu.be/APGEDaVBhqI

Oddy
16th April 2017, 10:36 AM
Revisited this after deciding to do a puzzle for my nephews birthday. Thanks for all the ideas - the approach that I have settled on that works perfectly is a collet style wooden holder that grips the ring around the outside. This allows you to turn and finish that final inside edge of the ring that I was finding impossible with all the other methods I tried. This is what I did:
* I turned a cylinder
* hollowed it to a diameter slightly smaller than the outer diameter of the rings
* cut a v groove on the inside face of the hollow cylinder for the ring to locate in
* cut slots through the cylinder to allow the "jaws" to flex open and closed
* used a hose clamp to tighten the jaws around the ring
A few pictures to show the approach for anyone interested:
410325
410326
410327
410328