Extension Arms Purpose ?

[coxsox]

So having purchased an Alfamachine U200 to replace my ageing Cassesse CS88, I decided to splash out on some extension arms. I've struggled sometimes to support my long frames before when joining, resorting to various support methods to hold that dangling end, along with brute force.

I only frame one moulding 50mm wide and 60mm deep, so its quite substantial and also prone to the nuances of wood, with the odd twist, bend, warp and thickness.

Fitting and aligning the extension arms could take many attempts and having got to the stage where I thought they were aligned I proceeded to start framing. I thought the new machine would perform really well, however I found it to be to the contrary, some of the worst joints I've ever done.

I thought what a useless underpinner I had bought, but after I had calmed down I had a think about things. As my wood moulding can vary along each length, I started to question what these extension arms were actually doing, and also designed to do. As the small wood section around the join is the most important area, I now think the support arms are there to not hold up the joint, but help you in handling the wood, and should sit slightly below the wood. Having them aligned to the underpinner would mean the whole length of wood has to be perfect, which is seldom the case. Yes you could adjust them perfectly, but would have to do this for every frame which isn't practical.

Just wondered what other people think about this/do. I've resorted to a rise and fall desk I have in the studio which seems to give me the best results in joins and handling, the arms are now redundant !

thanks.

[JKX]

They're not to hold the joint, clamps do that and if this model doesn't have them, then your hands do it.

My last two underpinners came with extension arms but I didn't even unpack them, because I had the machines in a cut-out in one corner of my workbemch; it was 12x6 ft so it did the job the arms were intended for, to support larger lengths, but better, as all 4 sides were supported when joining the last two corners. I had the machines as flush as possible to the bench, they weren't perfect but that wass OK as long as the bench was not higher. The last machine, a CS 200, couldn't be made flush without removing its feet. I doubt if the workshop floor was level, or my bench!

I think the main framers that use extension arns are those strange ones that have their machines the wrong way around & end up standing inside larger frames

[coxsox]

Well I've persevered with the extension arms, especially as they cost so much, and I agree, as long as they are not higher than the underpinner surface I should be ok. I've also moved the underpinner into a leant back position and this seems to also help things alot, not only with supporting the weight of the frames, but also lowers the underpinner so I can actually reach over and clamp the moulding myself easier....and no longer need the platform I ended up making....and the rise and fall desk just goes high enough to lean the opposite frame corner against.