SS Dowels instead of Mortise and Tenon joint

[Wayne88]

Hi Guys,

 

I have gotCarpenter a question which I really can’t find a straight answer for on the net, I would usually go to my Dad for this advice as he was Carpenter, but sadly lost him back in January. 
 

Basically, I’m building a lead-to porch above some French doors on my house. 150x150 Green oak. 
 

instead of using mortise and tenon joint for the upright post and the cross beam which will sit in the wall, why can’t I use two or even one stainless steel dowel (which I’ll make at work, I’m a toolmaker) and then put a oak dowel through them. So I’d just be replacing the mortise and tenon joint with ss dowels. 
 

Would this be ok? And if not why would it not? Just trying learn and absorb as much information as possible. 
 

Kind Regards 

Wayne Reid

[SteamyTea]

Not sure why not structurally, @Gus Potter can answer that better.

Some grades of stainless steel do not like to be in an oxygen deprived environment, why they are not used much in subsea environments, or rock climbing.

I can't remember which grade it is though.  This may help.

 

https://www.cruisingworld.com/how/beware-stainless-steel-corrosion/

 

https://www.manufacturingtomorrow.com/news/2020/01/16/stainless-steel-best-option-for-corrosive-environments/14630/

 

Not many toolmakers left working.  I did my apprenticeship in toolmaking, now most people under 50 do not have a clue what one is.

Edited May 10, 2023 by SteamyTea

[JohnMo]

Generally SS isn't used structurally as it's yield and shear strength is pretty low. No near as good as carbon steel. But I think you get corrosion issues with carbon steel and oak.

 

4 minutes ago, SteamyTea said:

I did my apprenticeship in toolmaking

Me also.

[Wayne88]

33 minutes ago, SteamyTea said:

Not sure why not structurally, @Gus Potter can answer that better.

Some grades of stainless steel do not like to be in an oxygen deprived environment, why they are not used much in subsea environments, or rock climbing.

I can't remember which grade it is though.  This may help.

 

https://www.cruisingworld.com/how/beware-stainless-steel-corrosion/

 

https://www.manufacturingtomorrow.com/news/2020/01/16/stainless-steel-best-option-for-corrosive-environments/14630/

 

Not many toolmakers left working.  I did my apprenticeship in toolmaking, now most people under 50 do not have a clue what one is.

Yeah, not many young Toolmakers about now. I was going use 316ss, with me being able to get it though work. 

[SteamyTea]

25 minutes ago, JohnMo said:

Me also

So that makes 3 of us anonymous.

26 minutes ago, JohnMo said:

But I think you get corrosion issues with carbon steel and oak

Why they galvanise it. Well they do for boat anchors.

2 minutes ago, Wayne88 said:

was going use 316ss

Make a load of spares and change them if a problem.

Could always you oak dowels, like the traditionalist use.

[JohnMo]

5 minutes ago, SteamyTea said:

Could always you oak dowels, like the traditionalist use

I would do that, if SS was good to use people would. But not sure they do.

[joe90]

18 minutes ago, SteamyTea said:

Could always you oak dowels, like the traditionalist use.

+1. 👍

[saveasteading]

44 minutes ago, JohnMo said:

But I think you get corrosion issues with carbon steel and oak.

Also with some stainless steel. There are several 'recipes' depending on the use. eg different in swimming pools to roof screws, to cooking pans.

Some of the worst staining of hardwoods is the reaction of the metal, so do check further.

 

Stainless threaded rod is quite pricey, compared with normal rod, but would be a lot easier than making your own.

If capped off and no weather reaching it, there shouldn't be any worries.

[Wayne88]

Thanks guys. I was only going use SS because I can get my hands on it for free at work and make the dowels myself. 
 

So, using dowels instead of mortise and tenon is ok and shouldn’t be a problem? 
 

cheers 

[Temp]

I used some 20mm SS round bar to locate posts onto the top of brick plinths.  Whole outbuilding is clad with oak using SS nails and screws.

 

But I did use M&T joints where the posts meet horizontal beam. Its just traditional. Bought a Sorbee (spelling) chisel for the purpose. Green Oak is nice to work with. Just don't leave any steel tools on the oak, not even for 10 min break or you get black staining.

Edited May 10, 2023 by Temp

[saveasteading]

2 hours ago, Temp said:

steel tools on the oak, not even for 10 min break or you get black staining

Good point. Same with aluminium. We have an oak worktop, 'sealed' with Danish oil.   A damp pan creates deep black staining. Will never use oak worktop again.

[SteamyTea]

This is the ideal time to test.

@Wayne88

Make up so rods and bang them into some oak, let's see what happens.

Edited May 10, 2023 by SteamyTea

[GaryChaplin]

On 10/05/2023 at 17:05, Wayne88 said:

Thanks guys. I was only going use SS because I can get my hands on it for free at work and make the dowels myself. 
 

So, using dowels instead of mortise and tenon is ok and shouldn’t be a problem? 
 

cheers 

Can you explain exactly how you intend to use the stainless dowel? A drawing would be useful. 

 

Traditional mortice and tenon joints in green timbers are draw-pegged, meaning the hole in the tenon is off-set to the mortice and causes the joint to be pulled together tight. This also helps maintain a tight joint as the timber shrinks. Using mechanincal fixings you may get loose connections over time? 

 

Also, 'proper' timber framers use pegs, not dowels. Pegs are cleft from straight grain timber and hand finished with a draw knife on a shaving horse. The should be tapered and octagonal to get optimum bit and performance. Dowels are typically straight and turned, which means they can be significantly weaker and jamb in the peg holes easily. 

 

I hope that helps and not rambling off-topic!