First Biscuit

[Daz Gizmo]

I've cut my first biscuit on a piece of scrap.  Very surprised how much vertical play there is (about 1mm) I was expecting it to be a tight fit.

This is the bit:

https://www.screwfix.com/p/trend-biscuit...-2mm/86342

What does the cut measure 4mm?

The biscuits usually are a snug fit but I have known them a bit slack depending on temperature.
They are designed to swell slightly when PVA glue is applied to them. You could try wetting them and letting them dry to get a more snug fit..