Underpinner problems

[iantheframer]

A general question really to help Ellis, perhaps us all

Personally on the example I gave It would depend on the wood, Trying to get 15mm wedges into hard oak is a little difficult, in this case I would try 12 but may even us 10mm especially near the back. With softer woods 15mm may be fine. If the section were 30mm wide I will try to get one in the middle too.

I guess what I am really trying to say is that underpinning has no hard and fast rules and has much to do with experience and experimentation as with most other things.

[prospero]

Pinning oak and ash is always pain. It's especially difficult when it comes to very narrow stuff, say <10mm wide across the back. The wedges tend to burst the back edges. In this case I would consider using the old 'poxy resin. The slooooow curing variety, not the instant, which is brittle. Pin toward the inside - not too close and not too deep and use a strap clamp if possible. But you must remove all traces of glue from the face before it starts to set. Particully on bare oak that you are going to polish after the frame is joined. Leave it clamped as long as you can. At least overnight.

[MITREMAN]

I guess what I am really trying to say is that underpinning has no hard and fast rules and has much to do with experience and experimentation as with most other things.

Totally agree with what you are saying, there are lots of wedge posistion that will work, but some better than others.

A good way while learning is to understand that the under pinner bung requires a flat platform to come down onto, there are many tricks to making a plaform if the moulding is a funny shape, such as using a v shaped piece of plywood or a bit of the same moulding upside down.

Then you have to learn what size wedge/type and pressure to work at, where to posistion the wedge.

If you mitre a corner and use one half only, look at the cross section, offer up the differant wedge sizes to it, see if they will fit or even if they can be stacked, is a taller wedge better. will the bung come down on a flat area.

When you have made your choice draw on the cross section the wedge posistion.
Put the cross section into the under pinner and set up the wedges to the marks, fire the wedges into cross section and you will see how the wedges react to your choosen postion, then you can adjust and try again.

Once you have learnt on a cross section try a corner, save a cross section so you can go back to it for wedge posistion when using the same moulding untill it becomes second nature.

MITREMAN

[framejunkie]

Trying to get 15mm wedges into hard oak is a little difficult,

I have a CS88, and gave up trying to join any oak and ash frames on it long ago. Until i can afford a pneumatic underpinner that can cope with such work(and there's lots of things above it in the wish-list!) i join all the harder woods other ways - bog standard is a nail gun - fires thin nails, so they're not massive holes to fill. Granted it's a PITA though...

[iantheframer]

I have a CS88, and gave up trying to join any oak and ash frames on it long ago

I too have a CS88 and join many oak frames, some better than others, oak (as with most woods)can vary a lot in its hardness and density. choice is important when selecting the wedge size for each individual piece 12mm works on some, but some need only 10mm. for instance I have used a selection of 12, 10 and 7 on the same frame in different corners

[prospero]

I like the manual pinners. You get a bit of bio-feedback though your toes.

I have an odd stick of moulding somewhere that is hard as the proverbial hells' doorknockers. Don't know what wood it is, but it makes oak feel like balsa. Won't even cut on a Morso unless you take wafer-thin bites. In the days when Ramin was common I tried underpinning a moulding about 70mmx40mm deep. The main spring on the pinner snapped and a bit went whistling past my ear.

[elly-d]

so 25mm by 30mm, depending on the wood and how well it joins from experience but I would probably use the biggest wedge I could. Maybe 2x 10mm stacked 5mm from the front and the same 10mm from the back.

I haven't been using glue. do you all use glue? on every frame? even the small ones? (the framer i used to work for who trained me up about 5 years ago never used glue) Just pva wood glue? isn't it a bit thick? doesn't it prevent a tight join? :shock

too many questions?

[Roboframer]

Yes, you must use glue, regardless of size, that's where the main strength of the mitre is; not the 'V' nails. The glue bonds the whole face of the mitre and dries harder than the wood - with most woods if you break a mitre, they won't break clean - there will be bits of wood from one side still stuck to the glue on the other.

One of the best ways to glue is to 'size' each side of the mitre - IOW seal it with a film of glue - rub it in with your finger, let it go off and then apply glue as normal before pinning. Doing this alone on some profiles, would be stronger with no 'V' nails than 'V' nails and no glue.

If the same person that taught you not to use glue taught you how to do anything else, then maybe your problem is as basic.

If when you push your mitres together on your underpinner, you see a perfect join but don't get one when you insert the 'V' nails, your machine has a fault, like maybe the hammer protruding too far, or is badly set up, e.g. the nail is inserted before the pad comes down, should be the other way round, or at least simultaneous. Your underpinner has no clamp - your hands have to push the two legs together as the nails go in, are you doing that with enough force/strength?

Are the 'V' nails going in the right way up? There is a sharp side and a blunt side - the sharp side is the side with the adhesive strip on.

But your machine uses a cartridge, can that be/is it inserted upside down?

GLUE GLUE GLUE!!

[vfmarky]

Like Prospero, I like the manual (or is that 'pedial'?) feel of my Inglet. You can actually feel the v-nail going into the timber.
Btw most of the mouldings made/imported into Australia aren't as rock hard as oak, so the choice of say, a 15mm v-nail in a 30mm deep moulding is based on that experience. Horses for courses really.
I find it pays to do a test join using off-cuts, that way any potential problems won't wreck the final job...

[Davie]

I myself very seldom use glue on mitres theres just no need,i think you get to know mouldings and how they react to pinning, for most i use cassese 89 but on oak i use either the cassese 299 or 486, im aware that most people wont have all these underpinners, but the 89 will do all by adjusting the top pressure clamp the correct wedge, and expieriance, what im saying is, there is no hard and fast rule, it all comes with time and trying what works best for you, glue does have its benefits but there is no one time when i always use it,but can be good if your having problems with the mitre opening up it acts then as a filler on bare wood.....Just a word of caution here, glue hitting the face of some mouldings can sometimes take the color off, so please beware.

[Roboframer]

The 'glue or not' has been done over and over, here and elsewhere, so has the nail or not (i.e. just use glue!)

Here's a quote - I can find hundreds more in favour; I found one against, from someone selling joining machinery.


Aways use glue and mechanical fasteners.

The mechanical fasteners -- whether v-nails, brads, or plastic inserts -- serve two purposes. Short term, they hold the joint still while the glue sets up, making it unnecessary to set the frame aside until drying is complete.That's important, because if any movement in the joint occurs during set up of the glue, bond strength is weakened. Long term, fasteners prevent catastrophic failure of the joint in the event of bond failure due to impact, or deterioration of the wood's fibers cemented, or the glue itself.

Some production framers skip the glue, considering it a messy "extra step", but that compromises the joint. Glue holds the corner's miters tightly together. Without glue, corners loosen due to gravitational and handling stresses on the joints, and normal expansion/contraction cycles -- sometimes within just a few months.

Whatever 'works' and maybe has for years for anyone is just fine, but I don't think it's good to suggest there is 'just no need' for glue.

[Roboframer]

Here's a current Grumble discussion - not on whether to glue or not - that's a no-brainer. But on whether to glue one side or both.

[Davie]

Sorry Robo,
Im a no brainer, to glue or not to glue, as i said in a previous post i very seldom use glue and cassese tell me there is no need minigraff make no referance either way, i have been framing over twenty years and have a successful business only doing framing i never advertise and have customers from three hundred miles away who use me on a regular basis i also join some very large moulding too big for the morso and these can be pinned together with no problems at all but if i try to break them apart i doubt Arni could do it, Frames i made twenty years ago you still could not pass air between the mitres, but just as a thought here, when applying glue and pinning immediatly does this not start the rusting program as the wedge is driven through wet glue, or do i need to let each frame set before i pin? I have a reputation here for speed, accuracy, quality and always deliver on time, I could expand without a problem but im happy as a one man band well more or less, working in 1000 foot workspace with two morsos two underpinners that work constantly the mitre saw cmc vacum press etc, So would you please tell this no brainer where im going so badly wrong?

[prospero]

Davie. You might get away with pin-only joins on a very large moulding where there is plenty of 'meat' in the moulding. But what about say, a 1" moulding on a 20x30 frame with glass? The joins are under constant torsion when it's hanging. Are you telling me the joins never gape just a little bit?

It's always been my belief that the main strength is in the glue bond. The v-nails are just there as internal clamps to hold the join tight while the glue sets and as a failsafe in case the glue fails.

[Davie]

Just had a call from one of my peers, A framer of great reputation, Like me he thinks that in some cases glue is appropriate but by NO means all, as he said "fine for the guys who do half a dozen a day and want to waste time" and went on to to tell me of some people who glue because thats what they have been told is the correct way. This guy is the finest framer i have ever seen and does some breath taking work, employing several other framers all of who are gcf, I aspire to his workmanship, methods and practices. I agree with him in as much as, you need to know your machines how they work and what it is your framing, ie size etc or handfinished and also a good knowlage of the timber being used, then onto wedges and so on.... Im still open to be converted, but give me the facts not hear say. If that can be done then you will have this phillistines gratitude. Thanks

[Davie]

Ah Prospero,
Here you have one of the few cases where i may use glue, There again if im doing say a framed poster glue again is not needed. I use pnumatic staple guns and put the staples through the backing board into the frame as well and the result is a nice tight finished and neat job.....Pick it up on the long side shake it and no movement....some people even use silicon to hold a narrow moulded frame together.....So the answer is no not even a little, again know your tools and the materials and how it reacts

[Davie]

Choosing the right underpinner nail choosing the right underpinner.......Google it.


It pretty much says what i think, sometimes but not always......

[MITREMAN]

Hi Davie,
In my Tutor role I would always advise the use of glue on individual custom framing, the wedges/ nails are there to hold the frame together as well as support the glue while it dries.

Mouldings for hand finishing, such as staining can be a problem with glue you just have to be careful and don’t over glue and wipe away quickly any surplus.

Glue can also affect finishes removing colour and leaf on mouldings care is needed, so can backing tapes if allowed to stick on the outside of the frame.

Yes glue will rust wedges, moister in some timber will also, some wedges are treated to minimise rusting.

Cassese agents can provide stainless steel wedges mainly used for the window trade, this would avoid rusting problems.

As a Framer who has done may thousands of frames on productions runs, where the pictures are just a disposable decorative item, glue on certain section can be avoided

Speed is a must in this type of work, glue takes time to apply, and can glog up the underpinner distributor head and transfer onto the moulding from the back fences. When working in factories to these high production levels you don’t have time to F…


What I am trying to say is each type of frame job must be assessed (size, section, weight) safety of the artwork, the end user and your reputation are all at risk if you don’t.

So for custom frames I would glue.

Production frames depending on profile, speed needed and quality required

Yes you can get a rock solid joint without glue at the time of joining, but over time I would expect it to open.

MITREMAN

[Davie]

Thanks Mitreman your more or less saying exactly what i meant.....A time and a place for it......I rest my case.

[elly-d]

Hi guys,

Well thanks for that, sorry to open that can of worms. I can guess it must have been argued many times before.

I have been using some slightly thinned pva on one side of each join, on my frames for the last couple of days after starting this debate. and I must say that I have been making better joins. Whether its the glue helping or the fact that in applying the glue it makes me pay more attention and take my time I don't know. Also I have spent alot of time cleaning are re-setting-up my machines, the block that the wedges are shot through had sank a little and caused the narrower mouldings to rock slightly when the pad pressed down. I think that was the main problem.

Well I had a good day today and all seems ok for now, until the next problem...laters.