Trevithick Dredger Engine Guide Bars
I was discussing the guide bars with a very experienced modeller, and he finished with some advice…. “make them either very accurately, or very sloppy, otherwise you will have problems!”
Well, I decided to shoot for “very accurately”.
I made the cross-head bar, and silver soldered it together.
So I made the bronze bushes, drilled them in the lathe to 9.5mm, then reamed them to 10mm. Or so I thought.
But when I fitted them to the 10mm guide rails, they were very, very sloppy. Checked the guide rail diameter… 9.99mm. Checked the reamer 10.07mm!! Chinese reamer.
So I searched my reamers and found 2 more. Another Chinese one measured 10.04mm. Another was a Sutton, made in Australia. It measured 10.00mm. I reamed a test piece, which fitted the guide posts perfectly. So which reamer did I use? Guess.
I made some more bushes and Loctited them to the cross-head. Then drilled and reamed them, carefully, accurately. This time the fit on the guide bars was snug, perfect.
Is there a point to be made here? You better believe it.