BWB Plus Blackwood Bindings Part 1 & 2

[TimS]

BWB Plus Blackwood Bindings Part 1 (Set Up and Gluing)

In my experience combining BWB with a wood binding can be quite sucessful if you have access to a vacuum pump, work out a logical sequence and work methodically and quickly. You are working against glue drying and wood expanding on one surface ata fairly fast rate, particularly on a hot day. I have found that:
Glad wrap is a good medium for a cover on the vacuum board
Flywire works well as an air circuit for evacuating air
Melamine is an effective surface to sustaining a vacuum seal.
Expansion joint foam works well as a compressive clamping caul on the neoprene rubber.
The wood binding piece works well as a pressure caul on top of the veneers, so keep the wood on the top side.

Vacuum clamping time works is about 1 hour but you can sustain the vacuum for longer if you like.

The glue will cause the venner to curl if left in the unclamped state for too long.
The wood binding section will cup slightly as the moisture from the glue is drawn through the wood.

Check out the images. When I process the bindings I will add some more images. The seal between the neoprene and the melamine doesn't usually require a caul but i put it on top just in case it leaks when I leave the workshop. The vacuum pump (Busch) will get hot ~ 75celcius but this is its normal temp.

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[TimS]

BWB Plus Blackwood Bindings Part 2 (Machining)

Bandsaw and Drum Sander


Plywood support under the BWB/Blackwood binding is essential to avoid tear out or fracture on the exiting edge of the wooden binding. The plywood should also be up against the blade tip with no clearance.
[attachment=5]BWB-Demo-13a.jpg[/attachment]

Bindings are cut 0.5 - 0.6mm over size. Make sure the BWB Purfliing on the top surface. Please note that due to the small dimensions it is recommended that you guide the wood to the blade with no side ways pressure after the blade as you will/might cause bad tracking which will compromise the thickness and cause the blank to taper. Slow to moderate speed only!!!

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21 bindings were recovered from an 80mm wide blank

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Width and thickness should be checked with a digital pair of verniers. The thickness and width can then be sized with the drum sander

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Sanding thickness

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Sanding width

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[John Maddison]

An excellent tutorial, Tim

[Kim]

Thanks for that Tim a most useful tutorial indeed. A few of us now have vacuum pumps in the shop so this could come in handy.

Just a question, does titebond original hold up to the heat bending process OK? I only ask because I have read on other fori that TB 3 is the glue of choice for this, and only this, application as it does not separate so easy under heat.

Cheers

Kim

[TimS]

Good question Kim. Sounds like a bench test is required. I have not had any issues to date so I guess we might be able to initiate a practical comparison between glues. I will keep you posted.

regards

Tim

[Bob Connor]

I had been using Titebond 3 for attaching purfling to bindings but I recently ran out of it so I used Titebond Original.

I had no trouble at all with it giving way in a Fox bender but I can't vouch for how it would hold up if you were hand bending.

[Dave]

I've just finished binding an OM by hand.

The first lot of bindings had the perflings glued on using Titebond II and they came apart in quite a few places and the perflings snapped - so I remade them.

I used Titebond III on the next lot - same timber and veneers - these were great no problems

Dave

[ozwood]

Gee Tim ,

They Look a lot Like some bindings I just received.You've just robbed me of all the Mystery ....... .

Paul.

[Clancy]

I've used Titebond 1 to attach purfs to qld maple binding then bent by hand. Not a single problem with them seperating.

[Kim]

It sounds like the 'issue' with TB1 is not always going to be apparent. A bit hit and miss you could say so that sometimes the glue appears to work just fine, and other times it does not.

There is also a potential for the bond to soften and 'fail' under heat, but for it to reestablish itself as it cools again. Given that any tell tale separation lines would need to follow the purfling lines which are the whole point of the operation, this process could go completely unnoticed as it is occurring, even under quite close examination. So although the joint does reestablish to be invisible, it remains weaker and therefore more susceptible to future separation. (This happen all the time with the bracing of guitars glued with PVA type glues that have been left in a parked car to become heat stressed)

This is because PVA is not like collagen based hide glue which essentially remains the same whether it is wet or dry with the only variation being moisture content and temperature. As I understand, but I must admit it is without complete clarity, PVA is a number of elements which under go a chemical alteration at a molecular level as the glue cures. So the application of heat and moisture after the fact is not 'reversing' that alteration, it is only reducing its effectiveness as a glue............permanently.

My reference to others who recommend using TB3 is advice from them having gone through the process of using TB1, experiencing a failure which had not rectify itself, and then experimented with the options to find a solution which would avoid the 'potential' problem. Given the rarity of woods which have the intensity of figure to be selected for use as guitar bindings, prevention is probably a better focus than trying to come up with a cure after things have gone pear shaped.

That said, I have no direct experience with bonding purflings to bindings off the instrument myself as I have only ever used bindings and purflings as separate components in the build or repair process.

Cheers

Kim

[Allen]

Tim showed me this idea last year when I was at his place and I was amazed at how well the vacuum worked the way he's set it up. Very clever fellow that Mr. Spittle.

I use HHG for the entire process. Don't use any moisture to bend them once laminated. Rarely a problem with a purf coming loose, but if it does, no big deal as I use HHG to glue them to the instrument.

[kiwigeo]

I had no trouble at all with it giving way in a Fox bender but I can't vouch for how it would hold up if you were hand bending.

I had trouble with some rosewood/bwb bindings I made up using Titebond I and bent on an iron. The next set I made up using Titebond III and results were alot better.