Underpinner advice

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noobie
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Underpinner advice

Post by noobie » Mon 09 May, 2022 9:41 am

I have a A+ A44-P underpinner which looks sexy but I’m having hit and miss issues with the timber pinning tightly closed with no gap visible or minimal gap visible.

When I place the two cuts on the pinnner, they appear to line up perfectly. Soon as do half a press to hold it in place vertically and from the top, I see it moves and shows an opening either front or sides and back.

I have played with the adjustments and maybe made it worse, so I’m going to reset and start again fresh- once I’ve had time to process. Before I get back to it I’m hoping for any tips that may help me resolve it.

I don’t think the issue would be from the cutting of the timber using the brevetti double mitre saw- but I am considering all options now.

Thanks!

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Re: Underpinner advice

Post by Not your average framer » Mon 09 May, 2022 10:33 am

If this is a problem with all moulding types, then it may be a problem with the underpinner, but if it is a problem with only one particular moulding then you may need to experiment with finding a better way of joining this particular moulding. Here a few different things to try:

1. Two small pieces of fine sandpaper taped to the surface on the underpinner with double sided tape, but clear of the area where the wedges are pushed into the moulding being joined will add extra grip when the moulding is clamped in place with the top clamp on the underpinner. This extra grip will resist the two pieces of moulding from trying to push apart when being joined.

2. Have you got the wedges loaded into the underpinner upside down, so that it is the blunt side of the wedges which is being driven into the moulding. This is almost certain to open a gap between the two moulding pieces being joined together.

3. There are certain difficult to join mouldings, which don't join well and sometimes open unwated gaps in the middle of the join, but both the inside and outside edges are closed. This is sometiming due to a problem while cutting the moulding, but it can also be a problem while underpinning the joint instead. These often happens with spooned mouldings, or coved moulding, if the is a slight bow in the moulding and it is not sitting properly while being either cut, or joined. Taping the dges together to hold the dges together while in position in the underpinner sometimes works, or carefully adding little pieces under the moulding to compensate for this problem some times works, but otherwise the problem may have been cause during cutting the moulding.

I hope some of this will help! Unfortunately, you often need to be a bit of a detective with such problems to figure out what is causing such problems.
Mark Lacey

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noobie
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Re: Underpinner advice

Post by noobie » Mon 09 May, 2022 11:22 am

Thanks very much. You have me some motivation to come back out and play.
It’s all mouldings and I’m using flat 20/30mm mouldings so nothing fancy to test.

I have the fasteners loaded glue side up which I believe is correct.

I have attached some photos of recent join. Looks great on surface looking straight on but closer inspection shows something not quite right.

I’ll keep playing, thanks for your advice. If the photos help with more clues, I’m all ears!

Thank you.
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Re: Underpinner advice

Post by Justintime » Mon 09 May, 2022 11:35 am

Make sure that you have the clamp the recommended height above the moulding, up to 30mm usually. If it's too high to start with you won't get the clamping pressure. I would only use 2 wedges. Place the inner wedge as close to the inside as you can 2-3mm from the inside and bring the back wedge closer to the front. If the back/outside wedge is too far back it will push the back open.
I prefer to put the back wedge in first then the inside one.
If you're not 100% happy use a strap clamp with cardboard corners inserted to protect the moulding. Clamp it up nice and tight. The glue needs pressure to go off. Most glues need 30 mins to go off and 24 hours to fully cure.

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Re: Underpinner advice

Post by Justintime » Mon 09 May, 2022 11:53 am

By the looks of it you could adjust your Morso left fence the tiniest bit towards you too (cat's whisker), assuming that you're cutting on a Morso.

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Re: Underpinner advice

Post by Gesso&Bole » Mon 09 May, 2022 12:16 pm

Reading your original post here, you say the join opens before you put the wedges in.

(Although I agree totally with Justin's comments 2 wedges, one very close to front, and the other nearer to the centre)

I think you mat have adjusted your fences out of square. I don't know this particular underpinner, but I think it has adjustments to 'twist' the fence too. This is designed to help you deal with warped moulding. Get a square, and set the fences to start with. So that it is 90 degrees, and the 'twist' is square.

Then get the widest flattest moulding you can find - something like 50mm wide by 10mm thick, and cut a small square frame (say 150mm) on your saw. Lay it flat on the bench to see if it joins properly. This will soon tell you if the saw is set up right. Assuming it is, put 2 sides in the underpinner and see if they join properly with the clamps activated. If not, adjust the fence/clamps until they do
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Re: Underpinner advice

Post by Not your average framer » Mon 09 May, 2022 2:02 pm

Yes really sound advice and this will help a lot. The fences on your underpiiner need to be set up really accurately. I've got a digital angle finder and I like my two fences to be exactly 90 degrees to ecach other. I also have a set of engineers feeler gauges and I check any errors from pieces of wood cut on the morso by measuring the gap after joining between the already accurately set underpinner fences and the two pieces of moulding which I have just joined. The resulting gap is for times the amount, by which the left hand Morso fence needs to be corrected by. After this you still need to cut two more pieces to re-check the results.

This may at first sound a bit crazy, but I'm not as young as I once was as need to have easy ways of doing some things. When I know how much I need to adjust the fence by I either clamp a wooden block to the bed of the Morso, before I loosen the fence and then place the necessary thinkness of feeler gauges between the wooden block and the now loosened fence, or else clamp the wooden block in place spacing it away from the still locked into position fence using my feeler gauges to set the wooden block forward of the fence and after clamping fence in position remove the feeler gauges and reposition the fence against the wooden block according to which direction that you need to move the fence.

My set of engineer's feeler gauge have sizes down to one thousanth of a inch. This enable you to reposition your Morso's fence by as little as one thousanth of an inch. If necessary keep repeating the process as you get everything zoomed in to exactly where you want i to be. I doubt if any of use can guess what one thousanth of an inch is by eye, but you can easily tend what it is with a feeler gauge. Does it show that I spent most of my work life as an enigineer. Yes, I guess that makes me seem a bit sad!
Mark Lacey

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Re: Underpinner advice

Post by vintage frames » Tue 10 May, 2022 9:03 am

From what I've read, you are cutting with a double mitre saw.
Maybe first thing to do is to get the absolutes right. Cut your mitres as normal.
Now go back on each mitre and make a shaving cut with the saw. If you have clamps. disable them and just hold down the moulding firmly.
Now try joining up the frame. If you're still having the same problem then follow any previous advice on under-pinners.
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Re: Underpinner advice

Post by noobie » Sun 22 May, 2022 12:21 pm

Thank you all for your feedback. As an update, I have worked out that the square I was using to adjust the Pinner was out by a mm. This was a made in US more expensive one. I have used a cheaper square and the issue seems to be resolved for the particular timber I was using, which was for a floating frame L shaped moulding.

Using the 20/20 natural timber moulding is now giving me different results where the front closes, but getting gaps towards the back on the edges. It may be a technique too, but I'm slowly chipping away at it. Any other ideas I am open to suggestions.

I will try a 30/30 moulding shortly too using the same adjustment and see what happens.

I do have the option to adjust the sides of the Pinner to angle them down or up (if the timber is not straight). At a slightly down angle the front closes up but the back and (rear edge of the side of the frame remains slightly open).

I like the idea of the digital angle finder for the fences, I will invest in one and see how these results differ. Im also interested in the engineers feeler gauges. Thank you not your average framer, I like the sound of the intricacy of your work.

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