Stabilising small pieces for CNC

I am wondering what advice you could share with me on stabilising small pieces of Australian timbers for making harmonica combs. I am setting up to mill these myself and would like to stabilise the timber. Harmonicas go through a fair amount of torture from moisture and then drying out when not in use which leads to the comb becoming swollen and twisting out of shape. This effect it’s air tightness.

Manufacturers have used timber, plastic, acrylic, aluminium, brass and composite materials. Overseas, custom makers create combs that are a step above the big manufacturers. I am looking at extending it to the market here and possibly overseas with our timbers. It’s just another part of a little business I am setting up.

I understand from reading here that our timbers take longer to stabilise etc. in the process of milling the combs I can create an initial pass between the tines enabling the tines to be evacuated of air and accept CJ more easily. Or would it be better to stabilise a complete blank prior to cutting it?

This is an image of the combs, the front two are from a large manufacturer and the one at the back is my first trial cut.

https://uploads.tapatalk-cdn.com/202...ab30ca72dc.jpg

Hi
Well first things first.

Looking at you timber sample it appears to me that you have machined that from a solid piece. The other two it looks as though they have been laminated. The laminated will be stronger and far more stable. This is due to the fact they are different pieces of timber glued together where your sample is one solid piece. The laminated timber tends to move less in comparison to solid.

I do not agree that Australian timbers take longer to 'stabilise' as this really depend on what drying process has be used. You cannot compare air dried to kiln dried as they are two completely different processes. In Europe and Scandinavia basically all timber used for joinery, cabinetmaking, furniture making is kiln dried, normally to around 9 -11 percent moisture. The reason for this is the houses are centrally heated and the climate is much cooler.

All the timber I purchased in Sweden was in this range, but here in Australia it tends to be a little wetter around 12 percent. however this can vary depending where you are.

Therefor my advice would be to cut your stock into small sections and glue up alternating grain use kiln dried timber.

I now machine timber componentry in my business for clients (after 46 years as a joiner) and this is how I would approach your issue.

I hope this helps

Kevin

Thanks for your reply. The front comb is bamboo and the laminations run horizontally. The second comb is one piece and the grain also runs horizontally. My comb is the same as the second. All harmonica combs are cut the same way.
I understand what you are saying about laminating the timber to add strength, it isn’t really required in a harmonica as the comb is sandwiched between the brass reed plates. I thought the same about alternate directions in laminated wood but if it is stabilised with CJ it really negates the need.
I may laminate some of the combs just for visual purposes.
Okay about the Australian timbers (I read that information here), I will be ensuring that the mc I as it needs to be for CJ.

Timber that thin should stabilize, with regard to moisture content, quite quickly. The question you need to ask is about the penetrative powers of Cactus Juice into the timber and whether there are differences between penetration into end grain and the face. I'd probably look at milling the tines first and then giving it another go after treatment. How critical are the dimensions and finish for this part of the job?

Thanks for your reply, I’m starting to wonder if I should just stick with Shellac? After the timber goes through the process of heating to remove moisture and then re heated to set the CJ, I can imagine that there will be some movement including twisting. Even if I stick with quarter sawn timber it may end up moving more than I hope for. I have spoken to a friend today who uses CJ all the time for his wood turning, I may give him some of my timber to stabilise and see what comes of it. If it ends up suitable I will invest in my own set up.

Ok to stabilise properly you need to dry the timber to 0%MC (drying at over 100C until it stops losing weight, and then a few more hours). You then cool in sealed bags so they don't take on moisture. Once cooled they are then placed submerged in Cactus Joice Stabilising Resin (CJ) under full vacuum until the bubbles stop. The release the vacuum and let your blank soak in the CJ for min 2x vacuum time, more if very dense timbers, I generally use 4x for Australian hardwoods as they are a lot harder then overseas hardwoods. They the blanks are removed and baked in an oven to set the CJ.

I would not cut your blanks extremely thin before stabilising as the drying and baking can then cause warping. I tend to leave them at lease 20mm thick, stabilise, then cut/machine to shape.

Stabilising only increases the timber density and water resistance (not waterproof).

Quote:

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Originally Posted by dai sensei

Stabilising only increases the timber density and water resistance (not waterproof).

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I wondered about that. Is there any treatment that will waterproof wood?

Quote:

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Originally Posted by burraboy

I wondered about that. Is there any treatment that will waterproof wood?

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Only totally encapsulating it, but the encapsulating medium needs to be strong/flexible enough for the timber's movement. Stabilising removes movement due to moisture but nothing removes the temperature movement

Quote:

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Originally Posted by dai sensei

Ok to stabilise properly you need to dry the timber to 0%MC (drying at over 100C until it stops losing weight, and then a few more hours). You then cool in sealed bags so they don't take on moisture. Once cooled they are then placed submerged in Cactus Joice Stabilising Resin (CJ) under full vacuum until the bubbles stop. The release the vacuum and let your blank soak in the CJ for min 2x vacuum time, more if very dense timbers, I generally use 4x for Australian hardwoods as they are a lot harder then overseas hardwoods. They the blanks are removed and baked in an oven to set the CJ.

I would not cut your blanks extremely thin before stabilising as the drying and baking can then cause warping. I tend to leave them at lease 20mm thick, stabilise, then cut/machine to shape.

Stabilising only increases the timber density and water resistance (not waterproof).

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Thanks for your reply. This confirms what I read from your replies to other posts. I understand about leaving the timber thicker due to movement during drying, makes total sense. I will give my friend some of my timber to stabilise and then go through the process of cutting to thickness and milling it on the CNC and see what the results are like. It still sounds promising.

Good information, thanks!