Securing Mortice & Tenon joints

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Roberto Flintofski

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Hi all,

Started a bit of an adventurous project, the construction of a replacement wooden greenhouse. My old one of about 12 years has stood used and abused and untreated for all that time and has now seen better days, on a limited budget I plan to replace with a new one constructed from 68x43 finished sizes pse timber then paint it before glazing with one of the Cuprinol shades colours knowing full well I am going to have to paint it every couple of years

I know in reality I should be using some form of far more durable rot resistant hardwood however funds currently do not allow for this, I have a morticing machine for the mortices and cut a sample joint to see how I got on ( just fine ) using my Band saw for the tenons on the test piece. Made a start today , mortices just fine however been struggling with trying to cut the tenons on the bandsaw due to the timber lengths, so have had to resort to cutting by hand. Had thought of trying to do them on the cross cut sled of my table saw, but again timber length 3300mm an issue, any ideas on how to do these an easier way ?

Next question, I'm a plodder so in no rush so can take my time and get 'tight joints' so do i just use a water proof glue to secure the joints or glue & dowels through the joint or glue and stainless screws ?

All help & ideas greatly received
 

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Ollie78

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Wedges maybe? If they are through tenons then definitely wedges if blind then you can still do wedges but you had better get them right first go !!

Cut the tenons marginally big on the bandsaw and use a shoulder plane to trim them nicely. Do you have a sliging mitre saw with a trenching stop you could do them on that.
I would give it all a good soaking with 5 star or whatever the Sika preservative is if its untreated softwood.

Ollie
 

Roberto Flintofski

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All will be through tenons so wedges are not a problem in the middle rails as I had already thought of those but I am also doing some tenons at the ends ( within 20mm of the ends of the verticals ) and thought that if I used wedges here it would split the last 20mm of timber out of the end with it being softwood.

Have a Dewalt sliding mitre saw but however alas no trenching stop !

Can you paint over 5* or Silka preservative ?
 

DBC

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You’re getting good advice above. Re. cutting the tenons you could make a jig and route them out. Cutting them by hand is very good practice though.
 

Jacob

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Glue (waterproof PVA) and wedges, plus pins through after the frames have been glued. Put one or two close to the shoulder line so that they keep the joint closed.
Drill for the pins after the frame has been put together - don't mess about draw-boring - this is a specialised joint for particular situations, not routine framing.
M&Ts need to be through, not blind as these can be water traps and can't be wedged.
 
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Roberto Flintofski

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Thanks for the info Jacob, draw-boring looks like a great idea, but tedious with long parts assembling and un assembling then re assembling ! re the message from pe2dave, if i swapped them over then the tenons would be on shorter lengths yes, 2000mm and less unwieldly !
 

Roberto Flintofski

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Ive looked at trying to make some form of trench stop arrangement for the Dewalt saw, with little success, it looks easier to just buy a new saw !!

 

baldkev

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Are you sure theres no stop? My old basic dewalt has a bolt which you screw in or out to set the height. Its not very accurate over wide cuts ( doesnt stay parallel to the base plate )
 

Sheptonphil

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Are you sure theres no stop? My old basic dewalt has a bolt which you screw in or out to set the height. Its not very accurate over wide cuts ( doesnt stay parallel to the base plate )
My Dewalt sliding mitre was can’t do trenching as the slides are enclosed in the saw head, and the saw head pivots, not sliding on twofixed parallel bars as most saws do. When making a sliding cut, there is no movement that is parallel to the saw base, except full depth for cut through.
 

Jacob

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Just remember to pull not push with your drawboring.

" To the shoulder
to the face
pulls the old git into place."
er - had to think about this!
Shouldn't it be:
" To the shoulder
from the face
pulls the old git into place."

i.e. draw bore holes in the tenon nearer to the shoulder than the holes in the mortice are from the edge?
 

Jonm

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My Dewalt sliding mitre was can’t do trenching as the slides are enclosed in the saw head, and the saw head pivots, not sliding on twofixed parallel bars as most saws do. When making a sliding cut, there is no movement that is parallel to the saw base, except full depth for cut through.
Same as mine, DWS778, 10 inch, big advantage is there are no rods sticking out the back. Bought it because it was a bargain, reputable seller, brand new, error in advert, £10.90 including vat and postage. I expected them to refuse the sale and was very surprised when they honoured it.
 

macca

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Same as mine, DWS778, 10 inch, big advantage is there are no rods sticking out the back. Bought it because it was a bargain, reputable seller, brand new, error in advert, £10.90 including vat and postage. I expected them to refuse the sale and was very surprised when they honoured it.
jheez ive paid more for postage alone!
 
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