Laminated jar wip

[powderpost]

At last, a laminated jar as a work in progress. First step is to design the jar. I have done this on a sheet of graph paper. First the outside profile, then the inside profile parallel to and 5mm wall thickness. It will probably help to hold a mirror vertically down the centre line to get a clearer picture of the finished shape. This job uses 18mm thick layers, standard thickness less 1mm for cleaning up the rings. Each ring is numbered from the bottom. Note the bottom is a solid piece for convenience. The attached "plan" shows the development of ring No 6. I have chosen 12 segments for this one, but the system will work for 6 or 8 segments. Underneath the profile draw two lines 15 degrees apart and centred as in the diagram. To get the angle, divide 180 by the number of sides.
Now draw two lines vertically about 4mm either side of the profile of segment 6. The extra width is waste to allow for small inacuracies. With a compass scribe set too the minimum internal radius, scribe an arc on the 15 deg angle. Now, with the outer radius, scribe the outer arc on the 15 deg angle, From that, the length of the segment, and minimum width required can be seen, and the length of timber required for the ring, can be worked out.
Do that for each layer. Now you can calculate how much timber is needed. As a matter of interest, I used 1.2m of 100 x 25. Thats probably enough for one session, more tomorrow.
Jim

[TTIT]

Thats probably enough for one session, more tomorrow.
JimOrrr I dunno - I could still go a bit more yet!:;
Lookin' forward to the rest Jim - 'secrets of the master' and all that!:U

[Skew ChiDAMN!!]

What I really, really, REALLY want to know is how I can cut angles accurately enough to do work like that... :rolleyes: :-

[SawDustSniffer]

im right with the set out and cutting , its just the glueing up last time that gave me the Sh!+s , epoxy every where lots of numberd bits of timber on the table , but not the next bit of timber , glad rap and fencing wire ,ya need 4 arms to do it

[powderpost]

Calculations done, timber machined, now is the time to start cutting. I now use a Kreg mitre jig, it is very accurate and easy to use. Before the Kreg, I used shop made mitre jigs, set permanently to cut 6, 8 and 12 sided rings. And before that I made a mitre box to cut the appropriate angles. The choice is yours.
I cut the pieces on a circular saw, but they could equally be cut with a mitre gauge, on a bandsaw. Use a pencil with an eraser on the end to flick the segments out of the way, safer than using fingers. I use a piece of wire with a point shown in the photo. Which ever way the segments are cut, they will need to have the "fur" removed. This is done on a sand paper board.
I have found band clamps, the type used for radiator hose connections the best. Get the cheap ones, they are more flexible than the good quality ones. Clamp up the ring and check for gaps. If the gaps are too big, adjust the mitre gauge and try again. If the gap is almost good enough, slip a match stick in the joints on the opposite sided and tighten the bands. Now loosen the bands and glue the joints, but don't glue the match sticks in. When dry sand the two halves on the sanding board and glue together. I use Selleys, "Tradesmans Choice" for gluing, it sets harder than normal aquadhere and sands better.
Make up all the rings and when dry sand one side flat on the sanding board.
Screw a scrap of wood to a face plate turn it to the diameter of the bottom from the drawing. Now cut a hollow in it, in preparation for the base piece.
I have, in the past, replaced the circular with a disc of plywood with sand paper glued to both sides, to adjust minor discrepencies in the segments.
Can't add any more photos, so, more tomorrow night.
Jim

[lubbing5cherubs]

Thank you Jim. I am enjoying this
Toni

[BernieP]

G'Day Jim

Great tutorial gives me something to look forward, like the old Mandrake episodes at the Saturday pictures when I was a kid.

Cheers
Bernie

[powderpost]

Ok, so now you have all the rings glued up, sanded, base turned to shape. Glue on the base block. If you are a bit fussy, mount the base on a screw chuck and turn a shallow recess in the bottom. When this is set, turn the base piece to the outside diameter as in the drawing. Now it is time to glue on the first ring. Set the tool rest exactly on centre. Use a cone centre in the tail stock to get the height right. Make a block with a hole to match the tool rest post and as long as the distance between the tool rest and the banjo boss. Put the block on the tool rest post and check the height of the tool rest is on centre. Adjust the block if necessary.
Now with the waste piece, base block and face plate in the lathe, slide the tool rest up to the base block, engage the spindle lock and mark a line accross the waste block exactly on centre. Turn the face plate and base block 90 degrees, lock and mark a second line accross the base block. Extend the line down the sides. Using these two lines glue the first ring on so that joints coincide with the two lines. Sounds complicated, but this process ensure the subsequent rings go on in the right place.
Turn the first ring square, to the outside diameter from the plan. True up the first ring and mark the two lines across the centre and down the sides. THis time these lines are half way between the first set, so the the joints in the second ring do not coincide with the joints in the first ring. Using these lines, glue on the second ring. True up the face of the second ring and turn the outside to the diameter from the plan. Mark the lines to coincide with the first set, again so the the joints of the third ring, are in line with the joints in the first. Repeat the process until five rings are glued to the base. At this point I rough turned, and a little full for cleaning up later, the outside face using the stepped rings as a guide. Turn the inside using the outside as a guide and check the wall thickness with a set of calipers.
Now using exactly the same process, glue the top three rings on to a waste block fitted to a second face plate. Glue the top on. I used the lathe as a press here.
We are into the home straight but gotta wait for the glue to dry, so the next instalment tomorror night...
Jim

[powderpost]

Bernie, we used to get Hop Harrigan. He was a pilot :D
Jim

[powderpost]

Hope you have done your homework and kept up with the rest of the class. :oo: Next step is to shape the outside profile, sand and if necessary a couple coats of sanding sealer to fill the grain. Now cut off the waste block on the top end. Clean up the top and give a thorough going over with sand paper, and more sanding sealer if necessary. Cut it off the waste block and clean up the bottom. This one I gave two coats of sanding sealer and finished with two coats of lacquer (sprayed).
A couple of ideas for a variation. Instead of cutting out only one set of segments, cut two or three and mix and match the segments or form patterns of different colours. Or maybe cut and glue some thin (2mm) pieces of a contrasting colour, between the segments. Even glue in between the layers thin veneers. Would recommend you make a simple one for starters, then start experimenting. The first one is the most difficult, after that it is a very simple process. Just be careful when cutting the segments. I hope this whole exercise has been helpful
Jim

[TTIT]

Extremely good tutorial Jim :2tsup: Thanks for taking the time - I might actually have a go at one yet :B

[lubbing5cherubs]

really nice thanks Jim
Toni

[BernieP]

G'Day Jim

Very enjoyable and very saveable, now to cut and paste into Word. I remember Hop Harrigan also guess we are showing our age.
Greenie sent I think.
Cheers
Bernie

[ss_11000]

great tutorial mate...i rekon it should be nominated for best of the best...

cheers

[Sprog]

What I really, really, REALLY want to know is how I can cut angles accurately enough to do work like that...

Skew, here is how I make the segment rings.
First make a sanding disk for your lathe, about 300mm, MDF works great as it is very flat. Make a platform that sits at the centre height and is exactly 90degrees to the disk. Fix sand paper to the disk with Sanding Disc Cement, Velcro backed paper is too soft and rounds over the edges.

Cut your segments as accurately as you can. If your edges are not exactly 90 deg you can touch them up on the sanding disk.
Now take 2 of the segments and apply glue to the sides and rub the joint. Best to do this on a flat surface to keep the segments aligned. When the glue grabs just hold it steady for about 15 seconds then carefully put it aside until the glue has set. Repeat with the remainder of the segments.
If it is a 12 segment ring you should now have 6 lots of 2 segment pieces.
Now repeat with 3 of the 2 segment pieces. You should end up with 2 semi-circles.
When the glue has dried, using the sanding disk you made, sand the ends of these 2 semi-circles so the ends are in-line, then glue them together to form the completed ring.
Sanding the ends of the semi-circles compensates for any errors in the original segment cutting.
You can also flatten the faces of the completed rings on the sanding disk.

[Skew ChiDAMN!!]

[...]Now repeat with 3 of the 2 segment pieces. You should end up with 2 semi-circles.
When the glue has dried, using the sanding disk you made, sand the ends of these 2 semi-circles so the ends are in-line, then glue them together to form the completed ring.[...]

EUREKA! :elefant:

You put your finger on exactly the problem I have. Now, why didn't I think of that? :-

[powderpost]

The rubbed joint is effective, but slow. I gave that up some time back. I will repeat what I said earlier, do a dry run using band clamps. If the joints are good, glue it up. If the joints are close, glue up two halves and put a match or small dowel in the joints without gluing and apply the band clamps. When dry, sand the two halves to get a good joint and complete the ring with glue in a band clamp. If the joints are pretty bad, then glue up in quarters, sand the quarters to fit and glue up. The other problem I encountered with rubbed joints was aligning the corners of the segments. The band clamp overcome this problem. Band clamps are the type used on older car radiators. Buy the cheapest, poorest quality as they are more flexible. Two or more of these bands can be joined to make larger rings. I have also found the perfectly square cuts for the segments are not critical, what is critical is the removal of the dags made by the cuts so the joint closes properly. The cuts not being square means you have to grind more off the face of the ring and it will be thinner.
Jim

[powderpost]

The sanding disc is also a good idea. I replaced the circular saw with a disc of ply with sand paper on both sides. Using one half of the ring on one side and the other half of the ring on the other side counters the disc not being square. If you use the sanding disc in the lathe, sand the first half "face" down and the other "face" up. That counters the disc not being square to the table. All learned by stuff ups and there were a more than a few of them. :-
Jim

[TTIT]

The sanding disc is also a good idea. I replaced the circular saw with a disc of ply with sand paper on both sides. Using one half of the ring on one side and the other half of the ring on the other side counters the disc not being square. If you use the sanding disc in the lathe, sand the first half "face" down and the other "face" up. That counters the disc not being square to the table. All learned by stuff ups and there were a more than a few of them. :-
JimBloody good tips Jim - wish I had thought of them! I bought a Triton sanding disk for the tablesaw many, many moons ago and always had trouble because it 'bends' as you push the work on to it. Either of your methods would counteract the errors caused by the flex in the disk. About to greenify!:;