Glue Myths No. 3 - Biscuits

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DLB
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Re: Glue Myths No. 3 - Biscuits

Post by DLB »

RFGuy wrote: Tue Oct 19, 2021 9:08 am ...It is worth pointing out that there is a high end biscuit jointer made by Lamello that costs like $1,500. I know at least a couple of production woodworkers, who happen to have YouTube channels, that use and love the Lamello biscuit jointer. Lamello even sells knockdown hardware that can be used in the biscuit slot. Check out Mike Farrington or Guy's Woodshop if you want to see a Lamello in action.
I guess that Lamello is what he was referring to in the video as the red one. I presumed Milwaukee, couldn't imagine it costing what he said. Now I know.

I've never had a biscuit joint fail. I've also never used one for an end-to-end glue joint as demo'd as 'unsuccessful' in the subject video. I don't consider its failure to strengthen that joint as a failure, it is simply not its intended use.

The video did not convince me that a biscuit does not significantly improve the strength of a miter. The 'miter' tested isn't a real miter, and the force that broke it is not a force I'm worried about. I don't think a miter would ever fail the way he demonstrated in the second video, a combo of the glue joint and the material, under real world conditions. I've never seen a real miter joint fail anywhere but the glue joint, and believe that to be the normal case.

The video did convince me that biscuits have one unfortunate characteristic. If used in a miter, the biscuit's grain is likely to align with the grain of one of the two work pieces. And therefore does not reinforce the lignin in that piece. I checked samples I have of two brands and believe that he is probably correct that the grain runs roughly 45 degrees in biscuits. Which seems inexplicable. :confused:

- David
RFGuy
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Re: Glue Myths No. 3 - Biscuits

Post by RFGuy »

David,

Thanks. Yeah, that Lamello is supposed to be a fantastic biscuit jointer from what I hear...for $1,500 it better be!!! :eek: I think it even has some micro-adjust settings on it which gives more control over the joint to the operator. Biscuits wouldn't be my 1st choice for a miter, but I think some use these as a quicker way to achieve a splined miter joint. I only ever used biscuits for alignment for glue-up such as with panels. I would be curious to know how biscuits fare versus dowels versus dominoes for strength in a panel glue-up. I know some woodworkers believe that all the strength is in the glue (PVA) and that anything added for side-to-side grain joints is just for alignment purposes only. However, these brute force strength tests are just that and only a snapshot at one point in time. I am more concerned with joint strength versus time and how it holds up with temperature & humidity changes. As Patrick pointed out in this latest video with biscuits in miter joints, even when the joint fails there is still residual holding power that the biscuit confers on the joint. In other words, it is helpful that when a joint fails that it doesn't do so catastrophically.
📶RF Guy

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HopefulSSer
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Re: Glue Myths No. 3 - Biscuits

Post by HopefulSSer »

I've got a porter cable biscuit jointer. I haven't used it a lot but when I have, I haven't noticed a problem with loose biscuits. (Sounds like a medical complaint ;-)

The most recent use I had for it was multiple biscuits in a miter joint in 5/4 material in a wrap-around mantle. It kept it aligned and I thought provided strength. Perhaps it only did half of those....

Perhaps because of seeing Norm use one I always liked the idea of it but just never did that much joinery that I thought would have benefited from it.

So I thought I was a fan but now I'm not sure 🤔
Greenie SN 362819 (upgraded to 510), Bandsaw 106878, Jointer SS16466
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