Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Spinningray]

Note form admin: this thread was split from the 4th raffle thread
+++++++++++++++++++++++++++++++++++++++++++++++++++

A special thanks to all the organizers and participants of the raffles. This has been a lot of fun. I hope my top will be as fabulous as Nimbus. Great job on the one way bearing top btw Chris. Now you need to make one for yourself (I need to make myself one too).

My plan is to show progress photos during the auction. It will give you another reason to check the board every day.

The top is constructed from a Birdseye maple board. I selected the board from the hardwood store because it had fairly straight and consistent growth rings down the center of the board. It looks like a series of arcs when you look at the end grain of the board. I created a center line for the grain on each piece of wood so I could be sure to perfectly line them up when gluing. This gives the effect of looking like one piece of wood. This also helps with the balance of the top. The birdseyes in the wood are like little dips in the grain. They start from the center of the tree and radiate outward. It is the nicest maple wood I have ever turned.

The tip / bearing section is made from this 2 x 2 x 2 chunk of Cocobolo. I bought the wood back in 2000. It has a jet black growth ring that will make a very cool ring around the tip.

[Spinningray]

I find and mark the center of each piece. Now I cut a tenon so my 4 jaw chuck can firmly hold the wood. The wood is pushed into the face of the 4 jaw chuck with the live center at the center of the wood. There is only friction to drive the wood. This is enough to cut the tenon. The corners can be rounded too.
The live center is from my metal turning lathe. If you don't have a good one, it is well worth the investment.
One of the center sections of the wood will be used as the layer near the tip section. The Birdseyes can be seen as a dark ray in the wood.

[lincolnrick]

Hey Alan, does the thickness of the board lead you to use your jaw chuck in the headstock?  Would a 4 spur drive center leave to large a mark?  Or are you just to lazy to remove the center and screw on the jaw chuck 

[Spinningray]

I use the 4 jaw chuck to drive the wood because it gives me a larger diameter contact which translates to smaller to forces to hold it. The larger diameter contact also gives a better chance of getting the wood square. Sort of like using a longer level to give you greater precision. I'm also going to be flipping the wood and connecting it to the 4 jaw chuck after I cut the tenon, so it is already mounted and ready to go.
I never use a spur drive. The only one I own has the spurs ground off. Caught the tool on a spur one time and that was it. I prefer to turn between centers (just a cone point on the head stock) or something that will slip if you catch the wood. The only thing that will slip with a spur drive is the belt.
The wood can slip on the 4 jaw chuck if you get a catch with your tool. I have also used the friction of a face plate to drive the wood and cut the tenon.

[Spinningray]

I make the crown section first. The wood must be turned precisely flat and square so the joints don't have gaps. The tenons are used to hold the wood securely with the 4 jaw chuck while truing. The second ring is trued first so it will match with the top ring. A 3/8" centering hole is drilled in each piece. The top or crown ring is attached to the 4 jaw chuck and the hole for the crown is partially turned so that it can be completed from the outside as one of the last steps.
The second ring is glued to the crown. It is centered with the 3/8" centering hole and oriented with the alignment marks. The tail stock forces the wood together until the glue sets.
I was careful to remove the center part of the second ring and will find a use for it. The crown section gets final turned and trued. It is essentially a bowl with a hole in the bottom. The bottom hole will be used to align the two halves when the top goes together.
I'm really enjoying this Birdseye Maple wood.

[ta0]

Thanks for the description Alan. But I am not sure if I am understanding the process correctly. Do you first turn each ring separately, then glued them to each other and finally turn the whole thing together? Each ring has a shelf (tenon) to hold it with the jaw, a large hole to accept the tenon of the next ring and a through hole for alignment? Is the small piece to the left on the first picture the cut out from the 2nd ring you mentioned? Did you cut it after gluing the second ring to the first ring? How many rings do you use for the crown? I am sorry for my ignorance but I have never turned wood.

[Spinningray]

Jorge - Each ring is cut a little differently. They all involve cutting a tenon. There are 5 rings total. I had to adjust the drawing I had made since the wood was thicker than the last time I made one this size. My original plan called for 6 rings.
This one has 2 rings for the crown section and 3 rings for the lower section. The middle ring (#3) will be the only ring that won't have a centering hole since I use the center of the ring as ring #5. I use the centering hole by pressing the live center cone into it and forcing the wood together. This holds it centered and true while the glue sets.
The small piece to the left in the first picture is from the second ring in the crown section. You can still see a bit of glue on the piece since it was cut after gluing the first and second rings together.

[ta0]

Thanks Alan for the explanation.  That sounds quite involved. Before your post I thought one just got the rings of wood flat with a planer or something like that and just glued them together while clamped.

[Neff]

Ta0 - I do that for many of my tops, but I am using plywood or other woods that are already relatively flat. 
Exotic woods often have irregular surfaces or are rough, so rather than having to find somebody with a planer, you can smooth out each piece the way Alan describes above. 
I have a chunk of "bean wood"  I need to do this too...

[Spinningray]

The first photo shows how I cut ring #5 from ring #3. It was cut part way through when I cut the tenon. The second photo shows the two rings separated. I had to take off ring #5 to release ring #3. I could have just used another piece of wood for ring #5, but I wanted to save wood.
The third photo shows ring #5 back on the lathe to bore out a hole for the Cocobolo tip section connection.

[Trevor]

Alan, it's so wonderful to see this top taking shape.  Amazing work!

[Spinningray]

Now for the tip section. I want to have the grain aligned similar to the body of the top. The wood must be turned corner to corner is this instance.
Two opposite corners are chopped off to give me flat spots for the center point locations. I mount it on the lathe between centers. The friction of the cone tip forced into the wood is all that is necessary to drive it. I turn at almost the highest speed I have. The dust collector is running and I'm wearing a respirator when working with Cocobolo.
I need to cut a tenon so it can be mounted on the 4 jaw chuck in preparation for the center hole and outer bearing well.







You can see the black ring forming in the wood.

[jim in paris]

hi alan
thanx a lot for the whole text

this cocobolo looks so sturdy
i'm sure the tip won't fall in a hundred years time


jim

[the Earl of Whirl]

I am always fascinated at the work people do with a lathe.....but the biggest fascination of all is when they are making things that spin!

[Spinningray]

This is the critical part of the top. Now that it is held firmly with the 4 jaw chuck, I can drill the center hole and bole the outer bearing well. You can really see the black band in the wood that has now created a ring. It separates the orangish colored wood from the purplish colored wood. It turned out very cool.
Then next step is to flip it around and mount it on the 3/8" jamb chuck. This will provide all the force necessary to turn the entire top. I added nylon washers to fill and support the bearing well to help it remain true.
The connection between the Colobolo and the Birdseye Maple is very tricky as glue does not adhere to Colobolo as well as other woods since it is so oily.
I created a stepped and angled connection which forms a complex geometry that eliminates the wood from becoming very thin at the interface of the two woods.
The tip section was turned to its final outer form which includes a short cylindrical section. It was sized to exactly fit into the hole I bored in ring #5. I essentially made a jamb chuck for the #5 ring which is shown installed backwards on picture #4. This allows me to cut the matching complex geometry of the tip section. Since the ring is jamb chucked, it can be flipped around to check for fit and then re-installed to make final adjustments.
After the #5 ring is ready for installation, I bored the wells for the one-way and inner bearings. Three steel pins were installed to prevent the one-way bearing from turning. The tip section has grooves and score marks to help the glue adhere to the Colobolo.