Hardwood flooring tongue and groove tolerance

[Warren Lake]

ive done them with dadoe blades, on the woodmaster with a knife ground to do that, or even single saw blade cuts will relieve some strength. you want to break the back of the material

[brent stanley]

No bottom relief cuts or end matching on this run. Though I had plenty of time while milling to contemplate about what it might take to do.

Here’s photo of the end / bottom of a 5” flooring board from a batch of factory flooring for reference. The bottom relief cuts look to be ~3/8” wide x ~1/16” deep and there are 5 of them on this width board.

I realize that everyone making flooring with any scale and consistency is pushing rough blanks through a moulder, but how would the old school shop like mine efficiently approach the bottom relief cuts? My best thoughts were maybe small diameter saw blades (~4” or so) stacked with spacers on the shaper…obviously in a different setup / machine than the T&G portion. Or a similar setup on the table saw with a dado stack though my table saw arbor is much much shorter than my shaper spindle and this would require multiple passes / fence settings / spacer blocks and no power feeder on the table saw…or to just have a corrugated or other type of profiled knives made specifically around these relief cut dimensions, though limited to ~4” height if corrugated and ~half that or less if in a profiled Euro block.

The end matching is not something that I am set up to do efficiently. I’m not sure how necessary it is on flooring that is ~5” wide or less.

I had Whitehill make me a set of knives a long time ago for a 100mm limiter block, tipped in carbide for longevity, that machines a few rounded reliefs on the bottom, when run on edge, against the fence on the shaper. Quick and dirty, because accuracy isn't as important for something like that. All the T&G work I've done has been small runs for historic homes, reproducing existing, or making authentic looking material that suits even if none was there. I've also done some wider work so I have two sets of knives, kne for standard strip width and some for wider material.