Should I convert to keg Pocket Holes or stay with Mortise and Tenons on Deck Bench?

**Peter Eng** · 24th May 2018, 09:24 AM

Hi Barry - I have recently started using Kreg screws and I'm quite surprised by their ease of use and strength. They will never be as strong as a good tenon glued properly as the tenon and glue have a much better area of grip. But if you use SS screws, a good construction adhesive and plug the pocket hole so water can't get in then you can resurrect the chair. Epoxy is a very good adhesive for timber. However it does have shortfalls. 1) It does not like water and timber holds water so if the timber is not dried correctly or its a wet day epoxy will not stick 2) Its relatively expensive compared to the options and the options are very good solutions to consider. PVAc's Like titebond like water (water is their solvent) so they are excellent to use on timber 3) Other construction grade adhesives like no nails and others are very good as well. These are generally polyurethanes or acrylics or hybrids and have the advantage of a bit of stretch for gaps and joint movement. They are gap filling whereas straight epoxy is not. On a technical note if a good glue is correctly applied a butt joint should be as good as any mechanical joint and the timber will fail first not the joint. So consider the screws a construction aid, make the fits as best as possible, seal screws with glue or plugs and refurbish poor timber prior to committing a joint to bonding. To discuss fits - all glues that use a solvent shrink as the solvent egresses from the joint. Epoxy does not shrink so this is the only adhesive that needs light clamping. So if you use any glue that has a solvent the joint needs to be fitted and clamped together quite tight. This is to ensure that as the glue dries, then cures it is not stressed due to its shrinkage. In some cases the shrinkage will crack the glue or pull it away for the faying surfaces. This is one reason joints fail. If you read the MSDS of PVA glues for instance you will see they are nearly 50% water so as they cure they shrink 50% by volume. This stress has to be supported by the glue which is quite a bit. To end - I would pull the chair completely apart correct any deteriorated timber with epoxy as this is a good application of it. Then use a construction grade adhesive to put it all together again. I'd use pocket screws if this was helpful on joints that can't be clamped. I use PVA to set all my screw connections (ie put PVA onto the screw then screw it in) and I'd plug any pocket holes or other screw holes that you create. Cheers peter s

**barrysumpter** · 24th May 2018, 09:40 AM

Hi Peter,
An Excellent reply.
Much appreciated.

I'd be very interested in what you would suggest as a construction grade adhesive.
Apart from Titebond III.

tia

-----

Watching many ytvids I see a thin coat of glue just on the tenons.
I find it very strange not to apply the glue on the tenon shoulders.
I've deduced its to prevent sneeze out cleanup.

I have only a few Tenons to clean this morning.

Then onto cleaning the ~150 Mortise.

Afterwards I plan on dry fitting.
Just to see where I'm at.

**barrysumpter** · 24th May 2018, 09:58 AM

Originally Posted by aldav

I think you'd find it easier to cut the tenon off, cut a mortise in both parts to be joined and use floating (loose) tenon's. If you still want to refurbish the existing tenon setting up a tenoning jig for the table saw or bandsaw would at least establish a regularly shaped tenon with accurate shoulders that you could then round the edges on.

Thanks aldav,
I have forgotten how much work actually went into this build.
Around 150 tenons and 150 matching mortise.

The Merbau is in surprisingly good shape.
Especially considering its been out in the weather year after year after year.

And considering my level of knowledge.

I just want to dry fit before deciding to remove the tenons and replacing with mortise.
And enlarging all the current mortise for a proper loose tenon fit.

I've already constructed a mortise jig.
And making accurate loose tenons seems easy enough.

**barrysumpter** · 24th May 2018, 02:45 PM

Wood Glue Vs. Construction Adhesive
Wood Glue Vs. Construction Adhesive | Home Guides | SF Gate

**BobMax** · 25th May 2018, 06:59 AM

What timber is the bench made from?

**barrysumpter** · 25th May 2018, 09:02 AM

Can't remember.

Outdoor hardwood.

Tassie Oak? or Jarra? or Merbau (aka Kwila)?

Can anyone help?
starting on page 2 post 29

Should I convert to keg Pocket Holes or stay with Mortise and Tenons on Deck Bench?

The oldest bench is at least 8 years old.
Build in 2000 I think.
the timber was from a fence at my daughters schools.
So the timber was even older.

**barrysumpter** · 25th May 2018, 09:07 AM

Taking a break.
Will start again on cleaning Mortise on Monday.

**barrysumpter** · 30th May 2018, 04:52 PM

2 to 4mm gaps in some joins

IMG_9460.jpg

IMG_9456.jpg

IMG_9457.jpg

IMG_9458.jpg

IMG_9459.jpg

IMG_9455.jpg

IMG_9462.jpg

**ian** · 31st May 2018, 05:53 PM

are you happy to live with those gaps, or do you want to close them up?

**barrysumpter** · 31st May 2018, 05:57 PM

is it even possible to close up a 4-5 mm gap?

Some of them looked like they were caused my my sanding to clean them off.

Even if I cur the tenon off to replace with mortise and loose tenon,
The gap wouldn't change.

**ian** · 31st May 2018, 06:35 PM

I'm thinking that to close the gaps, you will need to rebuild the bench so it is about 10 mm smaller than it currently is.

This should be easier than trying to lengthen the bits that would need lengthening

**woodPixel** · 31st May 2018, 09:43 PM

Originally Posted by ian

This should be easier than trying to lengthen the bits that would need lengthening

Indeed... shorten the lengthens rather than lengthen the shortens.

100% agreed.

**aldav** · 31st May 2018, 10:15 PM

What, no wood welder???

**barrysumpter** · 1st June 2018, 09:28 AM

Originally Posted by woodPixel

Indeed... shorten the lengthens rather than lengthen the shortens.

100% agreed.

Shorten the lengths rather then lengthen the shorts.

**barrysumpter** · 1st June 2018, 09:42 AM

Originally Posted by ian

I'm thinking that to close the gaps, you will need to rebuild the bench so it is about 10 mm smaller than it currently is.

This should be easier than trying to lengthen the bits that would need lengthening

Yes. I've thought about adjusting the back to make the posts closer together.
Where the top feature rail could be shortened by 5mm each.
The centre post tenon narrowed by 5mm each side.
That would take up the gap in the 12 middle rails.

The 8 outside rails would need adjusting as well.
I could cut the top feature rails (don't want to) on the outside of where the middle posts meet the top feature rails.
And take up the gap there for the 8 outside rails.

Still the question remains about cutting off all the tenons and replacing with mortise and loose tenons.
Or shortening all the existing tenon shoulders and the existing tenon lengths to suit.

Now that winter has arrived (freaking 3° this morning) I'm in the "Nah" winter mood. grrrrr

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