A horizontal router table is a very versatile machine and the safest, easiest and most efficient to use when it comes to making mortices, tenons, mouldings, picture frames, when edge-grooving and making raised panels.
Just to clarify; a conventional router table, or vertical router table (VRT), is the most widespread type of router table in use. In a vertical router table the router motor is suspended in a vertical position with the cutter projecting up through a horizontal table.
The horizontal router table (HRT) is not so commonly used but is an extremely useful machine. In a horizontal router table the router motor is mounted in a horizontal position with the cutter projecting through, and perpendicular to, a vertical table.
With a wide workpiece I find it much more practical and controllable to machine it when it’s laying flat on a horizontal table as opposed to it standing on edge on a vertical router table. When stood on edge the slightest movement is exaggerated at the cutter and can impact badly and spoil the edge being machined.
When making raised panels the exact same result can be had using a relatively small vertical panel cutter on the HRT rather than a massive panel raising cutter which you must have with a VRT set-up.
Trying to machine a tenon on the end of a particularly long piece of timber, or a mortice in the end of a piece of timber when using ‘loose tenons’ is problematic on a conventional router table but extremely easy and safe on a horizontal router table.
Making mortises is another specific task where the HRT is far more efficient than the VRT. Once you have set your ‘stops’ on the sliding tables then no more adjustments are required during the process of cutting the mortise. But trying to cut mortises on a VRT involves a number of cutter height adjustments for every single mortise that is cut; very time consuming
Both types of table have their advantages and disadvantages of course but one thing I really like about the horizontal router table is that it doesn’t get all the wood-chips, shavings and fine wood dust drawn through the router motor, which happens continuously with the vertical router table.