TREVOR GIBBS MODEL RAILROAD PAGE 5
USING A LATHE FOR MODEL BUILDING Pt 2
MAKING A "SMOKE BOX"
Please ensure that you are wearing Safety Glasses and that you are not wearing any loose clothing such as sleeves where they can be caught by the machine. I have not made a pretence about the final shape being what you as a reader may finish up with or require. However I believe that the basics are essentially correct.
Face off a surface on the end of a piece of round stock. The Round stock should ideally be about 1/8" larger than the finished item is meant to be. This should allow for any out of roundness of the stock.
Begin Parallel turning of the surface and reduce the diameter to the major diameter or largest diameter required, See Diagram. Make sure that you do not cut too close to the face of the chuck, but that you do not have your cutting face so far away from the chuck that the stock can vibrate and possibly machine out of true.
Now create a "step" which will become the modelled smoke box door. Do not go undersize or you may need to re-turn the face and start again.
The next part is a little tricky. You may have a profile cutting tool to cut to the shape of the rounded smokebox door or you may be obliged to use a fine file and file the shape onto the edge of the smoke box door, using the lathe while it is running to provide the relative motion. The faster your lathe is at this stage, the better. Make your forward strokes then lift the file away and repeat the action. If you have a suitable profile cutter, then well and good but do not go out of your way to get one for such a limited use. Simply substitute the profile tool for the cutting tool and apply it to the edge to be shaped.
Your Lathe should have either a live (rotating) or dead (solid) centre as part of the accessories. This Centre fits in the Tailstock which as we said before supports over long work pieces. There should also be a "parting" tool type cutter in your accessories. Set this up in your tool post so that the cutting edge is as exactly aligned with the point of the live or dead centre tool set up in the tailstock of the lathe. Also ensure that the cutting tool is as exact to 90 degrees to the stock as possible
You may want to create a "step" which will fit inside your model boiler. This is a good starting point for practicing "parting".
Apply the parting tool to the work in the area you want to cut to length, then gradually wind your cutting tool in and part the smokebox from the stock. If you get "chattering" or unnecessary vibration from the lathe withdraw the tool from the cutting and re-centre it or take it slowly into the work. You are applying a lot of torque to a single point of steel and applying Murphy's law, your cutting tool will break at the worst possible time for you!. Restart your cutting.
Voila... one roughly cut smokebox! Now have fun applying your details!
More to come...