The Framers Forum

Hi
I’m new to commercial framing and still learning the craft.
I’m seeking some advice from those with more experience regarding joining mitres

I’m not 100% happy with the outcome when using my Cassese 79 on larger frames (+70cm) and more ornate mouldings mainly the larger the moulding the harder it is to handle and hold in place when underpinning.

I realise I can use workbench to support etc and also at some point upgrade but for now I want to be confident I can turn out a perfect join when given a job which is a bit challenging ,my morso cuts are sharp and clean.

I don’t have a busy workshop and trying to work on higher end jobs so was thinking about using band clamps as Im hoping i can lay the frame on my bench and get a good feel if the joins are nicely aligned before tightening.


Any thoughts or insights anyone can share would be greatly appreciated

Kindest Regards
Neal
Sorry for long post

An underpinner is great if you have a busy workshop and many frames to make and join.
But an underpinner 'takes no prisoners'.

Get even the slightest error in your cutting and the underpinner will amplify the mistake on the joints.

So if you're not in a great hurry and you really really want the perfect joint, a band clamp is your only man!

Thanks for quick reply
That’s kind of what I wanted to hear.
Good quality PVA and how long should i wait for glue to set before removing the band ?

Am I right in thinking the CS79 doesn't have adjustable fences? If so, that's a problem there. You can cut a perfect mitre, but wood is wood. Minimum, I'd swap in the 79 for an 88 and get a few of these.
https://www.stanleytools.co.uk/product/ ... band-clamp

With a decent pva like Titebond, you can remove the clamp after 30 minutes or so, but make sure not yo stress the joints for 24 hours.

Whilst agreeing with justintime about the glue left to cure for 24hr, I always leave the clamp on for the 24hr. The clamps are cheap so having several of them means you can leave the frames strapped up overnight.

All my frames are raw wood based, so I secure the corners by cross pinning with long framing pins. Pre-drilling the holes with a spare pin alleviates the shock when hammering them home.

If you are using factory finished mouldings (why?..) then glue and underpin first, then clamp.

"For most of our wood glues, we recommend clamping an unstressed joint for thirty minutes to an hour. Stressed joints need to be clamped for 24 hours."
It's a judgement call. Tbh I clamp most of my frames. No wedge will give me as tight a clamp as a band clamp. If it only needed a bit of tension it gets 30 mins, if a lot 24 hours.

I do a lot of big chunky frames and I like to slightly over-engineer the joins.

The fact is that over a certain size frame the sheer weight of a big moulding tends to work against it. You have a bigger
glue area, but the glued strength depends on tight joints and even contact across the face. With the best will in the world
this doesn't always happen. V-nails are great, but you reach a point where they are just not 'man enough' for a massive moulding.
Also, manoeuvring a big frame in an underpinner can strain the joints you have just made.

I use strap clamps. The ones I use are Stanley ones that are not made anymore. They are strong and very simple. They don't have
corner pieces which allows me to underpin with the strap on. The nearest best thing are trailer tie-downs but they are a a bit complicated.
I also would advocate the use of a biscuit slot cutter. Biscuits give a lot of strength to a join effectively making a simple butt join into a
mortise and tenon. They also help when assembling as they can be slid horizontally <> to facilitate alignment but hole the joint rigid up and down.
I typically cut the biscuit slots, glue up and assemble the frame. You have to work quite quickly here.... Throw the strap around and cinch it up
tight, all the time checking and jiggling into place. I put plenty of glue on so any oozes should be wiped off here. Once strapped I put
take it to the underpinner and put v-nails in - usually the deepest part of the moulding. Btw. v-nails should not go through the biscuit.
This done I sometimes screw a 75mm steel plate too the back - under where the biscuit is. These should have a slight 'bias' in them by
simply giving then a sharp tap with a ball-headed hammer on the corner before fixing on. When the screws are inserted they will
then pull the face together. Keep wiping any oozing glue. Leave 24 hrs for the glue to set before removing the strap.

This may seem a bit overkill but you get a good strong join. I have had occasion in the past to try to break a join like this
and unless you are Geoff Capes it's nigh-on impossible to do it manually.

** btw. I'm on my 7th box of 1000 No.20 biscuits.

Thanks for feedback and insights very helpful
@ Justintime What’s a “Stressed Joint” ?
Cheers

"The prime example of a stressed joint is mortise and tenon. Box or finger wood joints also fall under the same category because they’re strong enough to accommodate wood glue and nails amidst heavy impact." (www.sawinery.net)

Ooh, can I jump on and ask what you mean about band clamps Prospero? Your ones without corners that you can underpin? The one I have from Screwfix, I think I could take the plastic corners off so it is just the screw/handle/ratchtety thing and the strap. Is that essentially the same or are your ones much more technical?

(Hijack over)

WannabeFramer wrote: ↑Mon 07 Aug, 2023 1:44 pm Ooh, can I jump on and ask what you mean about band clamps Prospero? Your ones without corners that you can underpin? The one I have from Screwfix, I think I could take the plastic corners off so it is just the screw/handle/ratchtety thing and the strap. Is that essentially the same or are your ones much more technical?

(Hijack over)

They are less technical and that's the beauty of them.

No big sticky-out bits and you can get a spanner on them. The webbing can get a bit tatty but it's easily replaced.
I got some Rockler ones which I thought might serve the purpose but they are very badly designed. I managed to
shear the spindles off with very little effort.

Thank you, I will have a play