I am working on an ash cabinet again. For small drawers I normally make the runners as to the right. Rout a 3 mm (1/8 inch) grove and insert a spline. Works fine.
The drawer divider to the right is only 6 mm thick so I could not use that method, instead I routed divider and runner in one piece. I now realise that the grain orientation makes the runners very fragile. To strengthen the construction, can I put some hard wax oil, lacquer or thin epoxy on the runners?
when I have used that method, I used plywood for the runners. The grain direction of the exterior layers of the plywood runs parallel to the direction of drawer travel, minimizing friction and chipping, while the interior layer runs perpendicular, preventing the runner from splitting. For approximately 1/8" runners, 3 mm, 3 ply doorskin works well enough. For heavier drawers, Baltic or Finnish birch or aircraft ply would be even better.
NB: For a CD cabinet, this type of runner works just fine without any drawers or shelves.
The vertical divider to the left with the runners are routed in one piece. The grain orientation is therefore vertical which is more sensitive to breakage, compared to the approach to the right where the runners consist of a spline glued in a grove and the grain direction is horisontal.
So is there any way I can strengthen the runners with vertical grain direction, eg apply some hard wax oil, lacquer or thin epoxy on the runners?
so on the left you routed away material from the divider and the runner remained, which is of course vertical grain? Not sure how you did that. Sounds complicated and a lot of dust.
On the favorable side, ash is strong. Stuck with this situation I would either fill the pores with cyanoacrylate adhesive and hope for the best, or more likely I would do nothing other than wax.
There may be another better solution....I'm thinking...will get back later
It is common in American antiques to see runners simply nailed to the case side. This arrangement has lasted centuries in these cases.
If faced with your situation and I wanted to do it "right" I would plane off the runner and route a shallow, say 1-2 mm, deep groove whose main purpose would be to securely locate the runner location. Then I would install a runner in the groove, glue the 1st half in place and nail the rest.
That said, what you have now will probably work acceptable, though I am unsure if the vertical grain for a sliding surface will present any problem.
I'm not sure that glue will have any meaningful effect, except possibly to lend a harder surface. Apart from chipping at the extremes, the seriously vulnerable spot is where the runner fibers attach to the divider. It will be very likely to split off a) if the drawer expands slightly in its opening and presses on the runner, or, more likely b) if downward force is applied to the drawer when it is partway out of the opening. I would not have recommended this approach, for reasons of the amount of work involved and the potential for failure.
If I had to deal with this situation, I think I would have used a modified egg-crate construction, where you rout or saw a slot in both the runner (long-grain) and the divider, with a shallower slot in the divider to keep everything aligned. Glue the front of the runner into the shallow groove and leave the back part unglued so the divider can expand and contract without causing problems.
