Rounded tenons...

[cusimar9]

I'm in the early stages of making a cot. It'll have around 40 oak slats all the way around (55mm x 10mm), morticed into the upper and lower rails.

I keep going back and forth on how I'll attach the slats to the rails, I could:

1. Mortise the rails AND the slats and use a loose tenon to hold them together. This is a good idea but would require 160 mortises, which would take an age to do on my plunge router!

2. Mortise the rails only and put a tenon onto the end of the slat. The tenon should have a shoulder to cover any slight inaccuracies in the mortise.

I'm currently exploring 2. to see if I could make those 80 tenons quicker than I could 80 mortises.

I've just finished making a router table and I'm currently thinking that if I ran each slat over the router on my mitre sled, I could cut a shoulder along each face of the tenon. With a stop block I could easily knock out all the tenons in a couple of hours.

The stumbling block now is that the tenons will not be rounded. What's the quickest way of rounding 80 tenons?

I'm going to try and run each slat over the router and turn it over as I go, which *may* round the tenon. Any other ideas?

 

[woodchip]

Domino would do the job in no time

 

[cusimar9]

Unfortunately I don't have one so will have to make do with the next best option

 

[Mr T]

You could make up a jig to form the tenons using a collar. Below are a couple of quick sketches. The size of the opening in the top piece would be determined by the size of the collar and tenon. Clamp the tenon piece as shown in red then rout round the end. Using a toggle clamp would speed things up.

Chris

 

[cusimar9]

Thanks Mr T that would definitely work, I suppose this would be quite quick also.

 

[Mr T]

Accuracy in forming the opening would be important. I would suggest fabricating the top out of three pieces, the two middle pieces cut precisely to the width of opening you require. You can shim things a bit if the tenon is a tight by wrapping insulating tape round the collar.

Chris

 

[RogerP]

Tenons are very quick to make using a bandsaw or table saw if you one or the other.

 

[cusimar9]

Tenons are very quick to make using a bandsaw or table saw if you one or the other.

As I said I think I can make the tenons very quickly on the router table, it's the rounding which is the issue

 

[Jacob]

...

1. Mortise the rails AND the slats and use a loose tenon to hold them together. This is a good idea but would require 160 mortises, which would take an age to do on my plunge router!

A really bad idea - too much work and a weak joint

2. Mortise the rails only and put a tenon onto the end of the slat. The tenon should have a shoulder to cover any slight inaccuracies in the mortise.

What about inaccuracies in the shoulder?

I'm currently exploring 2. to see if I could make those 80 tenons quicker than I could 80 mortises.

Why not do accurate mortices and fit the slats direct without tenons? Half the work. Mortice with a router and square the ends of the holes with a chisel.
You'd do it to marks, with the router fence always from face side only. To transfer the marks start with a rod then lay the rails on and mark off direct with a set square.
You could set out the rod with dividers, for accuracy, repeatability and to get them perfectly spaced. It might be easiest to make the rod first then make the laths to fit.

 

[cusimar9]

Thanks Jacob, that was my initial intention, to insert the slats directly into a mortise. The slats will be rounded so in theory this should be OK.

However if the rounded slat profile doesn't match the mortise exactly or the mortise doesn't correspond exactly to the slat then it will show.

I suppose if I use a template to rout the mortises then they'll be to a high degree of accuracy anyway... it might not be worth the hassle to do it any other way.

 

[SteveF]

why not sandwich the rails to take the 10mm and cut some spacers to go inbetween
or route full length of rails and use spacers
I know it is a cheat but no M & T to cut

Steve

 

[Jacob]

Thanks Jacob, that was my initial intention, to insert the slats directly into a mortise. The slats will be rounded so in theory this should be OK.

However if the rounded slat profile doesn't match the mortise exactly or the mortise doesn't correspond exactly to the slat then it will show.

I suppose if I use a template to rout the mortises then they'll be to a high degree of accuracy anyway... it might not be worth the hassle to do it any other way.

Keep it simple - insert slats direct. Don't use a template just mark it up carefully. All the other suggestions mean more work and more possibility of error. A bit of looseness is OK anyway, within reason.

 

[marcros]

Could you borrow a domino from somebody? It really would have the job done in no time.

 

[deema]

Have you thought if dowels? There are normally excellent Record (No 148) dowelling jigs on the auction sites for not much money. They are excellent (I have two!) and would enable you to put the slats together noth accurately and very quickly. A great gizmo for many other applications, if your a DIY'er a dowel jig is a great substitute for a domino.

 

[AndyT]

I agree with Jacob. You will want rounded edges on the slats anyway, so design them to match a routed mortice and leave the ends plain. As well as simplicity this keeps maximum strength on the slats.
If there are gaps they will soon disappear with a little glue and whatever finish goes on the wood.

I know it's hard to believe, but the contents of the cot will always be the focus of attention, not the woodwork!

 

[cusimar9]

Cheers for the suggestions guys, lots of good advice and good options. All of the above would do the job so I'll just stick to the easiest option which is to slide the whole slat into the mortises.

Cheers

Rick

 

[Harbo]

Cut them square and use a Japanese saw rasp to round over the ends to match the routed Mortices

Rod