I used 7/16" dia. brass, which is approximately 11.1mm, perfect as the widest part of the funnel needed to be 11mm. I cut a piece slightly overlength, then turned the parallel lower section (4mm dia.) before turning a 2mm dia. spigot on the bottom to locate in the smokebox;
To turn the lower part of the taper I swivelled the headstock around (there's no compound slide in the SL), and to get somewhere close to the correct angle I made a twice full size drawing of the spark arrestor, cut out the profile, and used the template to help set the headstock angle. Not very technical, and 'proper' model engineers will cringe, but the angle was close enough. I had to adjust the angle whilst turning the taper, but I ended up with the correct taper (or close enough anyway) in the end.
I had to use a pointed tool, and the original smaller toolpost rather than the 4 position post that I usually use, as the clearences are limited due to the angle of the headstock;
Again 'proper' engineers would cringe, look at the amount of overhang on the turning tool. Sometimes you just ain't going to get the perfect set-up!
To turn the upper part I held the job on the 4mm dia., then turned the short (.5mm long) top parallel section and faced the job to length. Then again it was a case setting the headstock angle and turning the top of the spark arrestor;
After setting the headstock square again I centre drilled the end, then drilled the upper section out to 4mm, starting with a 2mm drill then working up in .5mm steps, so as not to put too much strain on the turned section being held in the chuck.
Here's the finished job;
Spindle speeds were set at 1600/2000 rpm, and the work was cut dry.
Paul.
Now that's clever! I'm always in awe of engineers. Lovely job, Paul.
ReplyDeleteThanks Chas. I wouldn't class myself as an engineer though, despite my time spent in machine shops.
ReplyDeleteI'm only just scratching the surface of what I can do on this little machine, more soon.