Tight mitres

[The Underpinner]

Hi Folks,

I am a newbie to the world of framing ( and this site), having undertaken a basic framing course with DIY Framing in order to produce my own custom frames to fit my photography requirements.
Initially I purchased a Logan Pro joiner manual underpinner, but have had very limited success in producing tight mitre joints with this system; many of my joints open slightly during the underpinning process.
I make it a point to cut my lengths and dry align my frame prior to the pinning, and at this point there are no perceivable gaps in the mitre corners. It is only during the underpinning process that the gaps appear, and the only obvious problem is that the clamp mechanism appears to physically contact the V nail block at the bottom of the stroke which causes the clamp to lift slightly. Having persevered and analysed what I believe to be the root cause, I am now of the opinion that a more suitable underpinner may alleviate my problems. C
I would appreciate if any of the forum members could advise if the Cassese CS79 would be a more suitable option, or would the CS88 be the answer to woes. All I really want to achieve is good tight mitre joints that will not detract from the displayed material.
I'd also like to thank you all for a great forum.

regards
Allan

[prospero]

Hi and Welcome Allan.

That's a benchtop rig with a hand lever, right?

Never used this machine, so I can't really give any help specific to it. But the symptoms you describe point to not enough pressure on the top of the join. The v-nail when it starts to push into the wood imparts an upward force which will try lift the two pieces off the bed. It it is allowed to do this, the top of the join will gap.
If you can increase the top clamping pressure (again, not sure how it works on this machine) then that might cure the problem. You need quite a bit more pressure on harder woods than the usual obeche stuff. It may seem to be clamped down hard, but there is a heck of a lot of force needed to push the nail in.

If you are thinking of a new pinner, any Cassese model should give you good sevice. How much you spend on one depends largely on how much work you have for it. I'm sure other members who actually use these machines will give you their opinions shortly....

[The Underpinner]

Hi prospero,

Thanks for the quick response, much appreciated.
Yes, indeed the Logan Pro Joiner is a benchtop rig with the hand lever; the clamping mechanism obviously holds the moulding and then the whole lot lowers down onto the stationary V-nail block. As I mentioned in my initialposting it looks like the clamp itself is actually contacting the V-nail block at the end of the stroke, so this may be causing the pressure to come of the top of the join as you explained.
One of my reasons for looking at a Cassese system is that the pins are inserted into the stationary frame corner which I can understand is more efficient that moving the clamping system and frame.
As I only expect occassional use at the moment perhaps the CS79 would be the more economical choice, however if there is any substantial benefit from using the CS88 then that would be an option.

Thanks again prospero,
regards
Allan

[WelshFramer]

I've not used a CS79 but I did buy a nearly-new CS88 for £300 on eBay and it's great.

Before getting the CS88 I used something similar to the Logan - it was made by the guy who taught me framing. The only way to get good mitres with that was to glue the frame first using a strap-clamp and then insert the wedges once the glue had dried.

[Pharos Framing]

Allan

I can only add that I bought the Logan joiner when I was setting up and eventually narrowed my poor mitres down to the Logan just not having enough 'oooooomph' when putting the wedges in. I bought myself a Cassesse CS88 and have been very happy with the improvement in mitres. Whether you buy one new or second-hand it's definitely a worthwhile investment and should last you many years.

Eric

[The Underpinner]

Thanks Mike & Eric,

for your comments, it's looks as though I'll be scanning the classifieds for a good used CS88 or equivalent.
Might have a bash at modifying the Logan, as I wouldn't be too happy selling this because of the problems I've experienced.
Anyway, thanks again to everyone for the feedback it is really much appreciated; I also look forward to all the other topics and feedback on the forum.

best regards to all,
Allan

[Big Ada]

Hi Allen

I currently underprin with a CS 79 with great success. Good allrounder working with wooden and cheaper polymer mouldings.

Adrian

[Roboframer]

I've no idea how any cassese underpinner works - I've got a Euro (they went bust) underpinner and love it.

What I like about it is that the clamp is a horizontal one ands has nothing to do with the nail insertion - it slides into the rebate/under the 'lip' of the frame and holds it solidly while the pad above moves with the hammer below. When the mitre is clamped, what you see is what you get when the 'V' nails go in. There are 3 points of pressure - clamp, pad and hammer.

I've seen underpinners demo'd - don't arkse me what make but they cost more - where the mitre is clamped from above and then the hammer moves under that (2 points of pressure) IOW 'V' nails, in wider mouldings, are inserted away from the clamped area and you can see the moulding lift as the nails are inserted - not good!

[Not your average framer]

Hi Allan,

I also use a CS79, it's the baby of the Cassesse range. I've had mine since about 2001/2002 and I've hammered it ever since then. It still works just fine, but you get what you pay for.

The CS88 costs more, but it built like a tank and can accomodate much larger mouldings.

You can't go wrong with either!

[The Underpinner]

Thanks again everyone,

For taking the time respond, it is very much appreciated.
My current Logan underpinner is apparently designed to insert two V nails simultaneously with one actuation of the manual lever handle. From the feedback provided it would certainly appear that the pressure head? is not applying sufficient downforce to combat the force necessary to drive the two nails home. However there is still an apparent design flaw which allows the clamping frame to contact the V nail carrier causing the rebate clamp to lift slightly at the bottom of the down stroke thus causing the moulding to open.
Anyway as I mentioned before, I'm currently looking for a Cassese CS79 or CS88 system in the hope that it will cure my open mitre woes; hopefully in the next few weeks I can find a suitable deal and report back on how things transpire.
Once more thanks again to everyone; I think I'm now becoming a Framers Forum fanatic.

best regards
Allan

[framejunkie]

I think I'm now becoming a Framers Forum fanatic.

This has happened to many before you - another one lured into John M's evil scheme.
If you don't watch out you'll find yourself buying a Valiani, just so you can start swapping digital voodoo spells for it with the other techno-framers. It's a slippery slope....

[John]

This has happened to many before you - another one lured into John M's evil scheme.

evilplan.jpg (19.64 KiB) Viewed 5291 times

Oh No! Have I been rumbled?