Thread: 1/4" cherry does not fit into 1/4" routed receiving slot

The bit size is probably fine, it's most likely just a case of timber being timber. Unlike metal, a machined piece of wood often doesn't stay the same size... depending on local humidity it can change. Not by much, but enough that you can't really work by 'engineering tolerances' if that's what you're used to.

Worse, it can also cup or bow or.... again, usually not by much but it still needs to be dealt with.

I'm guessing that your routed trench does measure 1/4" and the timber ordered from Rockler was 1/4" when they sent it but you're in a different environment, probably more humid, and it has expanded slightly..

I'd try two things:

Firstly put a straight edge acorss the tongue and make sure it is still perfectly flat.

Secondly, wrap some 180 grit paper around a small block of wood (or a similar rigid sanding block. Don't use a soft, rubber painter's block!) and give the tongue just one or two passes on one side. Test fit. If still too tight, repeat on t'other side of the tongue. Repeat until it fits. I'd definitely do this at least once, just so I get a good feel of how much needs to come off.

It can also help if you put a slight bevel on the end/edges of the tongue to ease the fitting. Not necessarily large, just a mm or so wide.


BTW, this is noi an unusual situation. Don't take what you see in WW videos as a guide to 'how it should go' except in very general terms Reality can't be edited in post-production.

+1 for Skews advice. There is no better bit for cutting a shallow mortise/groove than the downcut bit you're using. The chances of the bit not being 1/4" is zip. You might be surprised how little sanding you need to do to get a nice tight fit. If there is end grain adjacent to your groove don't force the separator in and then pull it out or you risk tearing the end grain.

Originally Posted by aldav

+1 for Skews advice. There is no better bit for cutting a shallow mortise/groove than the downcut bit you're using. The chances of the bit not being 1/4" is zip. You might be surprised how little sanding you need to do to get a nice tight fit. If there is end grain adjacent to your groove don't force the separator in and then pull it out or you risk tearing the end grain.

Thank you both for your helpful responses. I wanted to ensure that I had not made some fundamental mistake. I will take your advice and push forward with my little project!

Much obliged,
Rob