Biscuit jointing on the router table

[siggy_7]

I've been given a pack of #10 biscuits. I haven't used biscuit joinery before, and I don't own a biscuit joiner, but I know that you can do the cuts with a router instead. I have a 4mm groover (a Wealden's 60mm Heavy Duty one), is this up to the task? I know it needs to be 4mm slot height but I'm not sure what the requirements for cutter diameter and depth of cut (and therefore bearings) are.

 

[Phil Pascoe]

The depth of the cut needs to be just more than half the width of the biscuit - you don't want the biscuit holding your two pieces of timber apart.
The cutter in a biscuit jointer is larger than the cutter you'll have on your mandrel, so you'll have to guess the profile you're actually cutting - once you've cut a few it comes easily. You can always dry fit a biscuit to check, and the closer you can keep to the profile of half the biscuit, the better your joint will be, and the less glue you'll waste. I did hundreds of them this way before I bought my biscuit jointer - it's not difficult.
Phil.

 

[mseries]

You just need to set your fence so that you don't cut your slot too deep, as phil.p says just over half the width of the biscuit. Then slide the workpeice sideways a tad since you need a longer slot than one arc(chord) of the cutter will give. (Biscuit jointer blades are 100mm diameter). It doesn't have to be exact but don't make the slots too long as you remove glue surface if you do. It will be quite simple to roughly calculate the distance you need to move your workpiece. Draw a 60mm diameter circle. Strike a chord, at a distance equal to just over have the biscuit width, from the circumference of the circle and extend it out of the circle for 50mm. lay your biscuit on the chord so that one end is on the intersection of the circle and the chord and the other end on the chord (it'll be outside of the circle). Mark the other end of the biscuit on the line. The distance from this point to the nearest intersection of the chord and circle is the distance you need to move the workpiece.

 

[siggy_7]

Thanks for your replies, I hadn't twigged that you need to make an elongated slot with the router - thought it was the same as using a biscuit jointer in that you just plunge in. So the bigger diameter groover the better.

 

[Eric The Viking]

It's OK as far as it goes, but the proper power tool has two big advantages:

• It's harder to wiggle the wood by accident, so the slots are tighter, leading to a better fit (and, as mentioned you don't need to elongate the slot, either) .
• You can put biscuits in the middle of flat surfaces. This is impossible with a router table.

On the other hand, with a router table, you can biscuit very close to the edge/end of the stock (not always a good idea as the biscuit swells in use), as the ends of the slot are steeper. When I use my jointer, there's usually about 1/4" of empty slot at each end of a #10 biscuit. The slot on the router table is barely longer than the biscuit itself, if done carefully. I think this is good for table tops, shelves etc., as you're tacking the extreme ends together, so it's less likely to split. That said, my jointer-made biscuit joints have all been better made and tighter, so it probably cancels out.

I have to say though, that since I got a biscuit joiner a couple of years ago, I don't think I've used the biscuit cutter on the router table once, but it's an inexpensive way to start off with biscuits and I don't regret starting that way.

Bear in mind though that my hands are a bit shaky these days, which might account for the wobbly slots a bit!

E.