A new year and already we've had the first good woodturning demonstration. This month Adrian Smith gave the demo on off-centre turning. There are a few signs which indicate someone takes woodturning seriously, one such sign was present on Adrian Smith... his own work smock with his name stitched on breast.
He started off by giving a top tip on making and expansion chuck for holding rings or any piece with a whole all the way through. Of course his examples were all off centre. Simply turn down a cylinder to the hole size, the cut down the middle on a bandsaw (not all the way). Then you can slide your piece onto the spiggot, and when you bring up the tailstock for support, the point will push apart the two sides thus providing an expansion and more grip. This should be enough grip to even turn off centre.
Another idea he showed was a metal plate with single piece at right angles welded to the back. That can be gripped between two bits of a 4 jaw chuck. Hot glue gun your wood onto the faceplate. Then you can slide and adjust the panel in the chuck to adjust the off-centre amount.
Then he moved onto the first demo... making a paper knife, notable because one of the first demos I saw at the club was a paper knife. Adrian said he saw that demo and thought 'I wouldn't do it like that' Cut tenon on end that can be gripped in chuck between two jaws of the 4 jaw chuck. The other end can be supported by tailstock. You can line up tenon with edges of jaw to get centre. Then you can slide the tenon to change the centre. This is way simpler than the technique shown before. The main thing is that the previous technique scaled to production turning 4 at once. But this way is much easier for a single piece.
Pre push tail stock into each of the end centres before you cut away removing the support otherwise the pressure will just bend the wood and risk breaking away.
Divide the wood into squares running down its length to help guide the consistent of centering both ways.
Turn off centre one way moving the tenon to a mark and tail stock across the same amount. Then shift to the other side. To achieve the blade. Obviously turn down closer to middle as you go down the 'blade' length. Another tip for demoing...When you have catch don't stop to see it...turn it away then stop..
Once the blad is turned both sides shift back to centre to turn the handle. Could be sanded on the lathe but just finished by hand often
Next project.. Making a fancy candlestick with off-centre turned discs down the stem. Big ish cylinder/cone tapering to tailstock. With long spiggot on end so that it's still in jaws when off' centre Taking away material as much as poss to reduce weight whilst off-centre
Make a mark on wood and tape on chuck to allow setting back to this point. E.g. since it can get rotated when you switch centres, it helps to keep alignment.
Time for another tip.. .candle wax on the tool rest to aid even movement of the tool which helps for an even cut.
Draw a straight line across centre line on tail end. Whilst spinning draw circles on end at intervals out. The point where the circle intersects with the straight line is even off-centre to each side. The various circles provide different amount of off centre. Long'n'strong bowl gouge for cutting. Short grind on it. Wouldn't use a spindle gouge on it. Marked heavy lines down the length to show the different points to cut. Set to first off centre point then straight V cut into the area turn until you turning all the way round but not so far that it drops off :-) Once done, move to another centre. If you follow a spiral path of centres you'll get a spiral of off centres. If you jump back and forth you'll get a more haphazard arrangement. You can turn such that you have 4 sections. 1,3 the same centre and 2,4 the same. Don't need to sand finish the first until you've done the second at the same centre. Once you've done a couple don't tighten the tail stock too far..else you'll snap off the end...since there is now not wood all the way between tailstock and head stock. Another tip.. Sliding chisel back off a surface to feel where it starts to come back on. Can be easier than spotting by eye where the edge is. Re-centre to do base and top dome. Shape the top size appropriate to candle type. Obviously a tea light needs more space. Better to face off the top before drilling. The drill bit needs to touch evenly to avoid stresses on the weakened frame. Put brass or some candle fitment on top.
Demo 3 Turning a cube to an interesting bowl. Close 4 jaw chuck up leaving small hole in middle, put corner of cube in hole. Put opposite corner in appropriate live centre..hollow centre for auger. Cut spiggot on one end..will be the base. If you catch too hard it will just stop as the friction is reasonably low. Then turn around onto spiggot... you need to cut the spiggot relatively far in to get reasonable diameter to hold. Now the opposite point is in live centre round over the base down to chuck leaving square top. Then remove tail so you can hollow out don't do the stem too thin. The grain is not running lenthwise so it will be liabe to snap. Obviously as you hollow you're creating three 'wings' the tips of which where the edges of the cube and the dips are the centre of the sides of cube.
Next tip.. When hollowing, don't bother turning all the way to centre...leave small stub and cut under occasionally to let it drop away. Superglue the edges to give rigidity to help get thin without break out. Sand flat surfaces with sandpaper on block to keep them flat. Used a ring tool to finish the hollowing
All in all another great and informative evening. Learned lots and picked up some good tips and techniques. My bowl gouge usage had been all wrong, just watching it done right helps a lot. Harry was ill and unable to make it so I couldn't get his opinion on my turning efforts, but Bill was on hand to set me a challenge for next month...a wine bottle coaster.
Since the last meeting I had a go at a letter opener. I made mine too short, but I was pleased with how the technique worked and I think next time I can get the proportions right.