underpinning a mould with a groove/bevel

[conway01]

Hi there
I'm having problems underpinning a polycore mould with a groove/bevel. Any tips on the best way to do it??

[MITREMAN]

Hi Conway01,
Please post a photo of the moulding profile you trying to join along with the size and reference number this makes it easier for members to help.

Also what underpinner are you using?

What type of wedge/ size are you using?

Are you using glue?

Also post a photo of your wedge positions

Kind Regards
Mitreman:D

[conway01]

THANKS FOR YOUR REPLY

Ref is POL 4222 - Mainline polycore mould. Underpinner is cassesse. It is an 8mm wedge. I am using glue. When I push the underpinner pedal down to drive the wedge through the two pieces of mould part from each other.

Any tips greatfully received. no photos available yet.

[Roboframer]

Here's the moulding - I'd post a picture but I can't get it to copy from Mainline's website.

http://mainlinemouldings.com/index.php? ... ry=POL4222

[kuduframes]

Hi guys, here's the photo of the beast in question.

Plastic can be difficult but it can be overcome -

Are you using the the correct grade wedges for plastic mouldings?
The top clamp may be causing the problem if it is not supporting the moulding adequately because of the shape of the profile
The wedge positions ares also important and should not be close to the back of the moulding or it will open up, see link
http://mainlinemouldings.com/index.php? ... th-Polcore
Also be careful how many wedges you stack as they will also tend to curve to the back and open up the join.
Don't rely on the rebate clamp alone to keep it together, some hand help will be needed.

hope this helps

POL4222.jpg (4.33 KiB) Viewed 6651 times

[framemaker]

I don't use plastic mouldings so the wedge position and sizes are just to illustrate the clamping positions, see Kuduframes post above for more info.

The vertical clamp always wants to be over where the pin is being driven in.

[prospero]

You can easily make a handy little gizmo to help with some slopey profiles. Cut a piece of thick ply in a triangle shape. About 4" wide, base to apex.
Stick a cork floor tile to one side. You slide this onto the slope section so you get the apex over the wedge insertion point and it will grip under pressure and not slide down the slope. I used cork as I had some tiles kicking about, but thick rubber or neoprene are also good.
To keep the cork from getting encrusted with glue, wrap the whole thing in handywrap which can be changed regularly.

if you are doing a long run or use a tricky profile regularly, you can make a chevron out of scraps of the same moulding but mitred the 'wrong' way round. that is, with the rebate facing outwards. This will fit neatly face down on the corner to be joined and apply pressure in exactly the right places thus equalising the pressure over the join. This is particularly useful of reverse profiles.

[conway01]

Hi many thanks for all your replies. or Kudoframes. Can you please advise what you mean by wedge quality?

[kuduframes]

Hi many thanks for all your replies. or Kudoframes. Can you please advise what you mean by wedge quality?

Basically wedges often come in different grades for different hardnesses of wood, for example, I use an alpha A2M which to best of my little knowledge only has one grade of wedge, but Cassese have different grades for hard /soft wood / plastic. If you are using the wrong one then it could further add to any issues you do have.
good luck, I'm sure it will work out in the end....

[Not your average framer]

Some moulding need a bit of experimentation to find what works best. Have you tried gluing and clamping it first, then joining it on the underpinner after the glue has set?

I don't know what sort of underpinner you are using, but not all shapes of top clamp pad are neccessarily helpful with this sort of profile and some can cause the mitre to open. I use a Cassesse CS-88 and have one of those magnetic right angled pressure pads with can be moved about to get the best clamp position and this gets me out of trouble a lot on difficult mouldings.

[Not your average framer]

There are two types of underpinner which have two independantly positionable "L shaped" top clamp pads, which automatically adjust their relative heights to suit the moulding in use.

These are the PILM range and the Gielle 4000e. I am fortunate to have recently bought a Geille 4000e myself and I am looking forward to getting it set-up and in use. The way that these underpinners clamp difficult mouldings may be worth imitating with one piece of solid thick plywood at the top and suitable spacers to make up the difference in height between the two moulding clamp postions.

I'm surprised that such a useful method of clamping 'difficult to join mouldings' has not been adopted my more underpinner manufacturers.

[sinbad72]

You can easily make a handy little gizmo to help with some slopey profiles. Cut a piece of thick ply in a triangle shape. About 4" wide, base to apex.
Stick a cork floor tile to one side. You slide this onto the slope section so you get the apex over the wedge insertion point and it will grip under pressure and not slide down the slope. I used cork as I had some tiles kicking about, but thick rubber or neoprene are also good.
To keep the cork from getting encrusted with glue, wrap the whole thing in handywrap which can be changed regularly.

if you are doing a long run or use a tricky profile regularly, you can make a chevron out of scraps of the same moulding but mitred the 'wrong' way round. that is, with the rebate facing outwards. This will fit neatly face down on the corner to be joined and apply pressure in exactly the right places thus equalising the pressure over the join. This is particularly useful of reverse profiles.

Very good advice here. Even Im learning things here. I havent much more to add except to always do the stacked outside wedge first. On that particular moulding I would do a single wedge slightly to the inside of the stacked wedge whilst pushing the two pieces as tightly together as possible. Then you can push the inside corner together tightly without opening the back again. I hope that makes some sense. Im not as articulate as some on this forum but I do try

[The Crofter]

Polymorph thermosetting plastic.

I posted this a long time ago, could be worth considering if you intend to use the moulding on a regular basis.

http://theframersforum.com/viewtopic.php?f=11&t=2097

[Roboframer]

I don't have a cassese, I have a Euro which is obsolete, but the cassese bungs (pressure pads - yellow for soft woods, green for hard woods) fit it.

Difficult to find a photo on line but look at page 20 here http://www.tabmaster.co.uk/products/pdfs/pdf_615.pdf.

They compress to the shape of the moulding on impact - there's pro's and con's though, like with everything, and I believe not all cassese underpinners take them anyway, maybe yours does.