Sliding dovetail size

[stuartpaul]

I've posted before in relation to my upcoming pedestal table (4 feet as opposed to a tripod).

Nearly finished Mr M's mortice jig to cut the sliding dovetails but wondering what sort of dimensions they should be? I've been unable to find any guidance online or in any of my books.

The pedestal will be 3 inches in diameter (or thereabouts). The 'feet' (legs?) will be about 1 3/8" thick tapering down to about 7/8". The table isn't overly large at 20" wide and high so won't be that heavy.

The largest dovetail cutter I've seen in the axminster catalogue is 32mm 'deep'. This would seem to be the right sort of size to give some real meat to the dovetails but would only leave a little over half an inch in the middle of the pedestal.

Clearly this seems a little on the small side and I'm worried about the strength of the pedestal bottom and subsequent splitting etc. Obviously I can adjust the depth of the dovetails but then wonder if they'll be strong enough? I could increase the diameter at the bottom of the pedestal but this might have a detrimental effect on overall proportions.

Thoughts, guidance or comments welcome. Apologies for the mix of imperial and metric but that's how I tend to work

 

[Steve Maskery]

Stuart
Your sliding DT doesn't need to be that big. The cutter you mention would be ideal, I think, and you would not need to go deeper than 20mm. Indeed, you could easily do that with a smaller cutter.

A tip about routing this kind of joint. I can't remember whether I mention it on Workshop Essentials 2 or not, but it is this. Don't try to cut the whole DT slot in one go, it will put a great deal of stress on the cutter. Now clearly one can't rout down in stages as you wold normally, so the trick is to rough out with a straight bit first.

Then you can set up two routers, one with your beefy DT cutter to cut the final slot (this time in one pass, as the waste is already roughed out) and the other, which can be a little MOF96 or equivalent, with a straight, bottom-cutter, to rout the flats for the shoulders of the legs. That way, those flats will always be properly registered to the slot, which they will never be if you have to set up the leg separately for the finished slot, then change the cutter to go round each in turn again to rout the flats.

Still with me? Well I understand what I mean.


S

 

[stuartpaul]

Thanks Steve,

Really useful in my planning. 20mm should leave me with enough meat to keep the strength I think I'm going to need.

Yes you did cover using a number of cuts before the dovetail cutter.

Thanks again.