Neat Joints on Corners - help needed please

[Jacko]

Hi ,

I have just taken delivery of a second hand cassese 939 double mitre saw.

Have wired it up, and it seems fine.

Not being a picture framer, I'm not up with the intricacies of getting good neat joints on corners of frames.

Tried cutting a few pieces of Polcore, and the cuts seems good.

However, when we pinned them ( using an Alfa 3 position pinner ), the joints on the top/front of the frame seemed ok, but the join at the side seemed to be slightly open at the bottom.

Joint - Polcore 1

image.jpg (1.78 MiB) Viewed 24645 times

Joint - Polcore 2

image.jpg (1.68 MiB) Viewed 24645 times

Joint - Polcore 3

image.jpg (1.69 MiB) Viewed 24645 times

Not sure if this is an issue with the Saw, the blades ( which seem sharp ) , the angle or settings of the blades, the Underpinning ( we tried various pinning , 2 and 3 pins, adjusting the distance for the pin nearest the outer edge , as I had read not to pin too close to the outer edge on this Polcore, and we also tried pinning reasonably close to the outer edge. But problem always the same, with a gap at the bottom edge)

Any "veterans" amongst you able to shed some light on anything we could do to get an improved finish ?

Canvas is my game really, not framing, so although I have sold many many pictures over the years, I have never had to worry about neat / even corners , as we usually only cut stretcher moulding which is invisible on the finished product.

Really appreciate and advice and pointers on adjustments I could or should make, whether with the saw, the pinner , or maybe my choice of moulding !

Thanks in advance for any help

Kind regards

Jack

[prospero]

Hi Jack.

Could be a few things, but check the bottom to see if the gap is from the outside edge to the wedge. If it's like this, but tight from the wedge to the inside then it's likely the moulding is being forced apart by the wedge. Common problem on polymer moulding.

If the gap goes all across the bottom then I would look to insufficient top pressure on the pinner. What can happen is that as the wedge tries to penetrate it can lift and separate the joint before biting in the wood/poly if it's not held properly from above. Wedges are made with the 'ears' slightly flared out so as to pull the joint together. So the front will tend to be tight but the bottom won't.

btw. is that an 'L' or tray moulding? Those can be a pita at the best of times. Or it may be a deep std moulding....If you are trying to stack wedges in the narrow sides then you may be asking a bit much.

[Jacko]

Hi,
Thanks for the info, much appreciated.

Underneath , on the bottom, the join doesn't look apart hardly, and looks quite tight.

The gap seems to be mostly on the side, towards the bottom.

Wondering if the saw is maybe cutting the edge with a slight arc, as opposed to a straight edge.

Knowing very little about these cassese saws , we checked what we could.
The vertical clamps come down properly, and the rebate clamps lock in place properly, holding the moulding square and firm.

Is it possible that the saw is cutting a slight arc on the outside edge ?

The moulding btw, is just a square profile, but we cut it for a float frame.

Also on the cassese saws, with these Polcore type Mouldings , should the speed of the blade travel be at the maximum ? For these poly Mouldings ?
( I have no idea what speed it was set at ! We just tried it at the speed it was at when it arrived.

Any other suggestions or advice from any gurus is very welcome ,

Thanks in advance for your help so far

Kind regards

Jack

[stcstc]

if you cut the same moulding on your morso, and join at the exact same posistions on you underpinner is it better?

my gut feeling is it that the back wedge is to close the outside of the corner

if you sit the 2 pieces on a flat surface to they line up correctly?

i would try putting wedges about half way though the moulding

are you glueing the moulding too?

[Jacko]

Thanks for your reply ,

Our Morso is in one of the toilets in the warehouse , next to the old underpinner !
So we haven't tried cutting on that
That seems to be becoming our used equipment graveyard.
Raises an eyebrow if a visitor is caught short.

We experimented with the wedge position, and tried 2 wedges with the furthest away from the edge at about the mid point. We also tried it with 3 wedges, all space and positioned at various points , but still the same results. The results seemed the same no matter where the wedge nearest to the outside edge was placed.

Is framing and making a good job of joints ,more tricky than I first thought ?

Is making a neat joint easier on wood than on Poly Mouldings ? Or are they both tricky to get a consistent neat finish ?

Give me canvas and I'll make a perfect folded corner... Give me a frame moulding and I suddenly make a pigs ear !

Any further gems of wisdom ? From you wise sages and craftsmen ?

I'm all ears

Thanks again in advance

Jack

[markw]

Wood is (in my opinion) easier to cut and join - but thats a very biased opinion as I hate plastic moulding. The joint you get is dependent on one basic constant - the way the moulding sits in the saw must always be the same when it sits in the underpinner. That constant is not always easy to achieve as things such as warps and bowed backs etc can make holding the moulding nice and square against the fence a bit of an art - or completely frustrating. Obviously some profiles and materials are easier than others.
My advice is to try and make sure your saw clamps dont push the moulding into an unnatural position and that the moulding sits nice and flat on the bed and is not pushed back flat against the fence.

[yorkframing]

It does look like a wedge issue but can also be due to the saw blade.

I have a Cassese 969 and only cut wood on it, to cut polymer, you should really change to a different blade if you have not already done so, I think it is to reduce the heat build up when cutting the plastic but not entirely sure?

I have had a mixed response with polymer, some join fine and some seem impossible to join, if you can, I would stick to wood and keep life simple!

[misterdiy]

You will defintely need a different blade for cutting polymer to wood.

if you have not changed the blade may I suggest you cut a wooden moulding on the saw and then pin that. if you have the same problem then it is highly likely to be the saw. If the issue goes away then you are left with two options. Firstly change the blade for one that cuts polymer (it is to stop the polymer melting/warping) If that does not solve the issue then its the underpinner and likely the nail positions. They should not be further than half way across the mitre on plastic (sorry polymer)

[Graysalchemy]

Not necessarily misterdiy, though there are blades which are designed for polymer you can just increase the speed of the blade going across to as fast as you dare. plastic causes a build up of residue on the blades which can be cleaned off in between sharpening.

To me the problem is due to the outside wedge being to far over IMHO.

One thing that may need doing is having you saw set up properly, ie having the blades set so they run true and that everything is level. When Neil Stout set mine up he had a laser gizmo to set the blades correctly.

[IFGL]

Looks like the pin is too far back to me too.

[JohnMcafee]

Check if the back of the moulding is truely perpendicular to the base.

Your description is consistent with there being a slightly accute angle between back and base of the moulding, and the cut being made while the back is held flat against the fence of the saw. If this is the case then ensuring that the cut is made while the bottom of the moulding is flat on the bed of the saw (and the back leaning away slightly from the fence at the top) should make a big difference.

[markw]

Wonderful illustration John

[easypopsgcf]

Not sure which head you have/use on your underpinner. If you are using a soft one, try swapping it for a hard one. When you use a soft one it seems to allow a little movement during pinning. I have tried cutting a polcore, the same way as you and it joins much better for me using a hard triangular head rather than a soft round head (cs199) .
Good luck

[Not your average framer]

Polymer mouldings behave a little differently to wood mouldings because there is no grain structure to resist the tendancy of the wedges to force the corner open to to accommodate the thickness of the inserted wedges.

Fortunately there are tricks to largely overcome this problem:

1. Try inserting the outer most wedge first and work progressively inwards with the remaining wedges. The outer wedge will tend to pull the corner together and the remaining wedges will tend to displace some of the polymer moulding material inwards, thereby reducing the opening effect on the outside of the corners.

2. If you use small enough wedges then you can stack them to a reasonable depth close to the inide of the frame, but only insert one wedge towards the outer edge of the frame. If the moulding is wide enough the maybe you can insert one or more wedges into the moulding in between the inner and outer wedge positions.

3. If all else fails, try softwood wedges. They will pull the corners together more tightly, but if I don't need to use them I prefer to use hardwood wedges as they should result in less stress being created within the moulding core materials.

There are no exact answers, so sometimes you have try some trial joints using left overs to find ou what works best with each particular moulding. I'm hoping that this helps!

[Jacko]

Thanks for all of your answers and advice,

Really very much appreciated.

I always thought that framing was just a case of , cut, pin, quick wipe of the glass, staple the back board, and 4 strips of tape.
Clearly i was watching the wrong guys ! churning out £1 a time 10x8's in 1/2 inch spoon moulding, many moons ago.

You guys are craftsmen in comparison.

On the subject of Poly mouldings.....are there some that are consistently better / easier to work with than the others ?
I'm aware of Artcore, Polcore, Minerva, and Emafyl.

Any views on which have performed best over time ? if there is a clear outright winner in any of your minds, be interested to hear your views ?

Also, regarding underpinners...we have a 3 position AlfaMachine....which is fine for joining canvas frames,....but are they really the tool for the job if i want a decent finish ? or again, should i be looking at a decent cassese instead ?

Thanks again, and appreciate all the help and advice

kind regards

Jack

[Not your average framer]

As far as I'm aware, the basic polymer materials are fairly similar from one manufacturer to another, but in any suppliers range there will some profiles which are easier to cut and join than others. If any of these profiles were not possible to cut and join to an adequate standard then they would soon be dropped by framers who found them to be unsatisfactory and the suppliers would be forced to drop them as a consequence.

Many large volume framers are using large quantities of even the more difficult profiles and these are the buyers who are driving the polymer mouldings market. They obviously have experimented and found the best methods for cutting and joining these mouldings. Unfortunately like them, we sometimes have to solve these things by trial and error, until we get an acceptable result.

Have you tried speaking to you supplier about this? They may be able to give you some specific advice, or they may even be able put you in contact with amother framer with experience of cutting and joining your particular moulding.

I use some polymer mouldings in my framing shop and I have to admit that some are easier to cut and join than others. There are even a couple of profiles that from time to time may need a little bit of filler. Fortunately these particular profiles are in a limed white finish and I can easily fill any slight gaps with a white gap filling adhesive, such as "hard as nails", which being an adhesive (not a filler) stays stuck.

I always glue polymer mouldings, so that I can avoid placing wedges to close to the outside of the moulding, but at the end of the day, nothing is always 100% perfect, so it's our ability to solve these difficulties which will distiguish us from our competitors and build our reputations.

[Steve N]

You could just use a wood moulding

[Jacko]

Thanks again, for all the info and advice.

I've got one of the lads experimenting with tilting the fences slightly on the underpinner, trying different pin positions, and different clamp positions.

We have also increased the speed for the travel of the blades, and there is less of the "burn" that we were seeing before.

Any recommendation on an underpinner that would possibly do a better job than our Alfa Minigraf 4 ?

I understand personal preference comes into play with "which is best"....but i would welcome any advice , especially from any framers who have owned and used an Alfa Minigraf 4, and maybe upgraded to something that produced a better join ?

thanks in advance again, for all your help and advice

kind regards

Jack

[IFGL]

The alpha will produce corners as tight as any underpinner the issues you have are down to cutting and/or pin position and will occur with other underpinners.

the benefits you might gain from other machines such as the Cassese 299 are speed.

[easypopsgcf]

Got to disagree I'm afraid. The clamp on the alpha minigraf 4 isn't nearly as strong on, for example the cassese cs299.
I used a brand new mg4 for 18 months, yes it's a very nice underpinner, but its not in the same league as the cassese in my opinion.
Also you can't use your hands to manipulate the wood/plastic as you need to use one hand to fire the wedges in, although I think the older models had a 2 or 3 stage foot pedal, similar to the cassese.

I now use a 6 year old cs299 which is a joy to work with, no more changing the head just to change wedge size, no more weak clamping