The Framers Forum

been having this problem for a while now.

Just changed blades on Morso so no problems with the blades(i hope). Cutting a 350mm square frame using a mainline polcore moulding 4041, check my cassese cs-79 underpinner with t-square, all seems ok....so why the open corners???? it's doing my head in!!!!!!

Also had the same problem with the larger polcore 4043 and a few others.

Also tried tapping the left fence adjustment...not much help there either


any suggestions would be appreciated

Andy

Open at the inside or the outside? Does it do it on other mouldings?

Could be the shape of the moulding. (Sorry.... Mailine cat gone walkabout atm). Sometimes plastic stuff can bend a bit before the blades bite creating a less than plane cut. Particularly if the sight edge is a bit weak.

Also, if the blades aren't really sharp. Plastic tends to dull them quicker than wood. If they are dull you lose accuracy.

ecossefineart wrote:been having this problem for a while now.

Does this imply that there was a time when you never had this problem at all? Is it only during the colder months of the year and is your workshop cold or the storage area for your Polcore cold?

If so, polymer mouldings become harder at lower temperatures and also have less friction with the bed and fence on a Morso. It may be that the blades are able to slightly push the moulding sideways during the cut, due to the reduced friction at lower temperature.

This may sound a bit far fetched, but the reduced friction with polymer materials at lower temperatures is science fact, not science fiction. I'm guessing from what you've already said, that you don't think it is due to the more obvious reasons, so here's something a little less obvious to consider.

You don't say where you are positioning the wedges. Polymer mouldings generally join better if the wedges are positioned towards the inner edge.

Which of the pressure pads are you using? The round yellow one seems to work better with this type of profile. Do you bring the pressure pad down so it almost touches the moulding as soon as the wedge starts to enter the moulding? Some people make up shaped sections to put under the pressure pad that matches the angle of the moulding profile.

I am not desperately keen on polcore type mouldings and restrict what I offer to the mouldings that join well. These mouldings are generally bought by price concious customers so the last thing you want is hassle and wastage.

Perhaps pneumatic underpinners with a strong clamping system are better for these mouldings?

thanks for all the info guys

1. my workshop is not particularly cold as such but it isn't exactly the caribbean

2. I generally place my wedges about 3 quarters away from the inner edge and I'm using a normal cream triangle shape pad on my old cassese underpinner sometimes the hard black pad to...there is research ongoing on replacing with a pneumatic...sooner rather than later hopefully

3. have came to the conclusion that some "polymer" mouldings are not quite as "square, flat, or straight" as they should be and think this is more of the problem than anything mechanical.

Andy

I have had the same problem, the only way I could fix it was by using polcore glue before pinning.
Hope this helps

I'm suddenly having this problem also, with a 20mm flat black polcore, so much so that I've taken it off the sample board. The corners are awful, some gap at front, some at back and some all the way along! Have just put new blades on morso & wooden mouldings are fine. I too do wonder if the square pol mouldings are totally flat.

I don't use a lot of plastic mouldings, only when I'm matching something else, and I was getting this issue too.
Like imagelab I was glueing them using plastic glue and holding them together for around 10 seconds before pinning. This seems to be enough to rectify the problem.

Hi
I think you have probably got most of the advice you need but I just wanted to add a small point when you said:

2. I generally place my wedges about 3 quarters away from the inner edge

this may be causing a problem if the joint is opening on the outside egde. You want to position your wedges closer into the inside edge, as a general guide when possible you want to start the wedge position 1/3 of the way along from the outside corner. You can pretty much go as close to the inside edge as you like, but when you start going too close to the outside edge it will open up the corner.

Sam