Tuesday, February 23, 2016

Third Turn's a Charm (Almost)

Having finished the boiler backhead and cab detailing (or at least the bits attached to the body casting) I've turned my attention to one of the other details of the original model which I think can be improved... the buffers. Certainly the loco is currently fitted with some rather distinctive buffers that have a circular core wrapped with a metal band as you can see in this photo.

If you remember back to the original model the buffer heads are just plain disks. Now no matter how skilled I might be with a file there is no way I could accurately file those heads down to represent the prototype and anyway given I own a lathe turning replacements sounds like a lot more fun.

I've actually been thinking about how to turn replacements for a few days, as having never turned anything without Paul's supervision I had to think about the best way of approaching them all on my own. In the end I drew a picture with dimensions and then a list of steps (on the left hand side, the right hand side is notes I made while turning the first attempt).

If you can't read my handwriting (sometimes I can't even read it so I wouldn't be surprised if most of you think it illegible) by plan was to basically work inwards in steps; turn the bar down to the max width of the head first, then turn down the rest to the width of the shank, and then turn down just the locating pin. The only complications being the slightly smaller diameter of the front and back of the buffer head. Turning the one on the back of the buffer head is easy, but the one on the front I decided probably needed doing after I'd parted off the buffer by turning the buffer around and mounting it on the lathe using the locating pin. After lots of careful measuring and turning I had my first attempt completed.

Unfortunately, just as with my first turning, I managed to loose some of the buffer head when parting off, so the head ended up being a lot thinner than I intended, so much so I didn't bother to re-mount it to do the final work on the front face. While it was far from perfect I had at least turned something so I set off to have another go. This time I managed to make the buffer head too big when parting off and when I went to try and rectify this with it mounted the other way around in the lathe, I got my handles mixed up and took off too much, so that was also a bust. On the third attempt though (I still parted off too much but I then faced off the buffer to thin it down) I produced something that dimensionally I was fairly happy with.

The shank could do with being a touch thinner but I could live with it as it is now. The main problem is that the surface is not very smooth. I'm guessing I've not set something up right as I basically end up with lots of grooves around the turning, which are easy to see in the photo and easy to feel as well. After my experience last time I made sure everything was nice and tight and as far as I can tell nothing shifted while in use. My guess is I've got the tool at the wrong height or angle, but I'm not entirely sure. Anyone have any suggestions as I need to figure out what I'm doing wrong before it's worth turning a full set of four replacement buffers.

1 comment:

  1. Mark, increase cut depth and lathe spindle speed. Then traverse a bit slower finish with a bit of emery on a stick. I assume tool height is correct too high it will rub and too low it will tear both being obvious.