Paul Willis
On Stuart Firth said… I do find recently that everything needs to be opened up to get it to fit – the spacer and the worm both needed drilling out 2mm to get them onto their respective shafts, and the final drive gear was reamed 1/8″. The spacer was also a little too long, as with the previous loco, and needed shortening very slightly to allow the intermediate layshaft to spin freely. These things aren’t difficult to do but I have to wonder if they would be challenging to a newcomer, who might, reasonably, expect stuff to just fit…
Hi Stuart,
This is how it’s intended to be. It’s all covered in the instructions:
“A – Finish-to-Fit
High Level gearboxes build into precision mechanisms which are designed to run with fairly close tolerances. Some holes and components are Finish-to-Fit, which is standard engineering practice to achieve a precise fit of parts. This requires the use of basic model making tools and will help to ensure that the box performs smoothly and reliably in your loco.
B- Opening out Holes
We have intentionally etched hole sizes for shafts and bushes slightly undersize, so in most cases they will need to be carefully opened out to match the components. Take it slowly as you progressively open out the holes (a tapered reamer or broach is ideal for this) until the components, when offered up, are a push-fit in their holes. Remove a small amount of material at a time as you frequently ‘gauge’ the fit by trying the component in place. De-burr the holes by inserting the tip of a drill bit (of larger diameter than the hole) and gently rotating it between your fingers.
Holes in turned parts, such as axle bushes, may also be finish-to-fit. Occasionally, moulded gears may need to have a small amount of ‘flash’ removed at the end of bore, which can be done by gently rotating a small round needle file”
I’d much rather have to open out a hole to be the correct fit than to float an axle in a raft of solder whilst trying to centre it in an over-large hole…
All the best,
Paul