Working with cracks?

[Robomanic]

Hi All,

This was going to be a play and throw away, but I would like to do something about the cracks to learn as much as I can (and I am growing attached to it).

Here are the offending cracks;

88763 88764

The biggest is probably open to 2mm and pretty deep as you can see. I am thinking of using clear 24hr epoxy, warming it to about 60*C to thin it and make it go off quicker.

My understanding of CA is that it goes off when it reaches a certain thickness, and does not set properly if left in blobs. Does this mean that it is only good for fine cracks or do you guys get it to work for large ones?

Any tips or comments would be very much appreciated as always, thanks.

[dai sensei]

Your idea of epoxy will work.

You can also use CA, you just need more than one type, and don't use the cheap sh_t. Start with a quick coat of thin CA to penetrate well into all the cracks - do not flood the crack as the thin stuff will turn white if too thick. Then use medium CA to fill the larger cracks up to 2mm, then thick CA for cracks greater than 2mm. Leave it overnight, or if you are on a hurry, use accelorator after 0.5 hour then leave it another hour (or two to be sure). It does go off.

Cheers

[TTIT]

I don't use epoxy at all but plenty do. I find CA works fine regardless of the crack-size as long as you use something as an 'aggregate' such as brass powder or ebony dust (my preferences only :shrug:).
My 'rule of thumb' would be roughly...

0mm (cracked but not open) = thin CA
open to 0.5mm = medium CA
0.5mm and up = (brass powder + thin CA) OR (ebony dust + medium CA)

If the cracks go right through the walls of the piece, use 'All weather tape' to stop the powder and CA falling through - most other types of tape go gooey and are difficult to clean up.

One down side of CA fill might be that it makes for a very rigid fill so if your timber moves the fill doesn't follow it so to speak. Don't know if epoxy is any better in that situation - maybe one of the 'araldite aficionados' can enlighten us????:U

[Skew ChiDAMN!!]

I don't use the 5min Araldite for turning :no: but I've found that with the "traditional" Araldite (24+ hr) and other 2-pack epoxies (inc. West Coast) that it can cope with a little flex while turning the following day.

However a few days later, once it has fully cured, it becomes fairly rigid and doesn't stand up to this "turning flex" any better than CA. Also, it seems to become brittler with the application of heat, so I recommend it's not sanded until after all turning is done!

For a job with that many splits, I'd also wrap it in duct tape. Not in a spiral, but seperate bands, so you can remove/replace each band as you turn each area. This isn't to prevent further cracking - although it can help - but more an attempt to minimise lost teeth in case of UFOs. :rolleyes:

[rsser]

Another option is to leave the cracks as they are; ie. go really rustic - while taking precautions as Skew mentions.

With lighter coloured timbers CA and wood-dust fill is going to be a shade darker than the timber and so be very obvious to the eye.

FWIW when I use CA I squirt the cheap stuff in a section at a time, spin the bowl (while standing aside!) and sand with 80 grit paper to make the dust. The paper drives it into the crack. And keep doing this til filled. Anything over a mm wide would be a pain with this technique though. And of course you have to leave it til late in the shaping otherwise you just turn it out.

[rsser]

One down side of CA fill might be that it makes for a very rigid fill so if your timber moves the fill doesn't follow it so to speak. Don't know if epoxy is any better in that situation - maybe one of the 'araldite aficionados' can enlighten us????:U

As an Araldite amateur this is how it's performed so far in the Cypress 'WIP' ...

There were a number of sizeable voids in the shoulder of this piece, filled with the 5 min stuff and coffee grounds. In turning, one piece chipped out at the top of the branchwood pictured. It's about 8mm thick at this point. That might have been predicted given the void here is wider on the inside than on the outside.

Hollowing went below the branchwood and it held .. after that I slopped a bit more on while patching two other voids from the inside. So far there's as much damage from the timber cracking as there is from fill chip-out.

[Grumpy John]

0mm (cracked but not open) = thin CA
open to 0.5mm = medium CA
0.5mm and up = (brass powder + thin CA) OR (ebony dust + medium CA)


Vern, is the medium CA available in the 7 for $2 blister packs and is it the same as or thinner thinner than the gel.

[Robomanic]

Thanks for all the great tips guys, there is always so much to learn here :2tsup:. The reminder about the tape has got me wondering if I would survive (with teeth in tact) leaving the cracks in and sanding them smooth once finished to make a feature of them. Might give it some OMG factor. It has such an unusual shape that I might just get away with it.

Prob' not going to get much done on it for a while but i'll keep you posted...

[rsser]

What you can also do by way of insurance as you thin the wall is squirt CA in as you go, hit it with a water spray to accelerate it and go down bit by bit.

Good luck!

[NeilS]

spin the bowl (while standing aside!) and sand with 80 grit paper to make the dust. The paper drives it into the crack. And keep doing this til filled.

:2tsup:...tip, Ern.

And, standing aside, or at least wearing eye protection, is a good reminder that CA in wet eyes is going to set very quickly.

Should you forget to avoid a CA splash in the eyes, at least remember to keep your eye lids open (serious suggestion), otherwise you won't be seeing much....:sad2:... until a doc gets to work with a scalpel...:(

Neil

[NeilS]

My 'rule of thumb' would be roughly...

0mm (cracked but not open) = thin CA
open to 0.5mm = medium CA
0.5mm and up = (brass powder + thin CA) OR (ebony dust + medium CA)



TTIT, and others, any reason not to make up some 'medium' CA by mixing thick and thin CA? I seem to have more use for the thick and thin than medium CA, and have made up my own medium mix from these if ever needed.

Neil

[dai sensei]

Vern, is the medium CA available in the 7 for $2 blister packs and is it the same as or thinner thinner than the gel.

Warning - you get what you pay for. Personally, I'd hate to see a bowl I have spent hours on spoilt because I didn't spend $1 or $2 extra.


TTIT, and others, any reason not to make up some 'medium' CA by mixing thick and thin CA? I seem to have more use for the thick and thin than medium CA, and have made up my own medium mix from these if ever needed.

Neil

I use 2 bottles of medium to each bottle of thin & thick, but I use it gluing in pen sleeves. Not sure about mixing them, the thin goes off so fast and the chemistry of each are different surely?

[tea lady]

What about the urea formaldehyde glue for filling cracks? You can blend it with PVA to adjust the inflexibility the glue joint, which might help with the turning stresses. Also I think you can add fillers to it, so maybe colouring it would work too. Dust from sanding it is not healthy, but nothing seems to be with this wood turning lark.:rolleyes:

[TTIT]

Vern, is the medium CA available in the 7 for $2 blister packs and is it the same as or thinner thinner than the gel.The 7 for $2 stuff is what I call medium CA (but I could be wrong). Thin CA is watery by comparison.


TTIT, and others, any reason not to make up some 'medium' CA by mixing thick and thin CA? I seem to have more use for the thick and thin than medium CA, and have made up my own medium mix from these if ever needed.
NeilNot sure on this Neil - I once tried the CA Gel but it didn't do me any good. Haven't tried the thick CA - or is that the same as the gel???? :confuzzled:


...tip, Ern.
And, standing aside, or at least wearing eye protection, is a good reminder that CA in wet eyes is going to set very quickly..................
Neil
Don't worry about the eyes - spraying CA once cost me a $550 set of glasses that were only 3 months old. Solution = bought more chucks so I can load up something else while the CA dries properly

[Texian]

Shannon,
Recall you can thin 5 min. and 30 min. epoxy with a little DNA so it will flow into cracks more readily. Might want to try a test piece.

[Grumpy John]

Don't worry about the eyes - spraying CA once cost me a $550 set of glasses that were only 3 months old. Solution = bought more chucks so I can load up something else while the CA dries properly

The chucks prolly cost more than the glasses:D:doh:.

[rsser]

Well, just to add: with smaller bowls spinning is faster with the fill business.

But with larger bowls, just squirt and hand sand.

[Robomanic]

Thanks for the warnings guys, I was aware that CA was very dangerous for the eyes but it doesn't hurt to have the warning repeatedly put out there.

Unfortunately I am the kind of guy who thinks things through carefully then still occasionally manages to do something stupid right at the critical time :doh:. For now I will be staying away from CA for that reason. Hate the smell of the stuff too. (no offense to those who can't smell it over other smells that may be present :q)

[TTIT]

The chucks prolly cost more than the glasses:D:doh:.Yeh but what a good excuse to buy more chucks :;:U:U


Shannon,
Recall you can thin 5 min. and 30 min. epoxy with a little DNA so it will flow into cracks more readily. Might want to try a test piece.Hmmm - didn't know that one - does it effect the cure-time????

[rsser]

Yeah, it's a pox, but with a bit of care there's nothing else that can do what it can do as easily and quickly.

Overall it's less of a risk than bringing a stationary tool up against a lump of wood travelling at umpteen metres a second.

And of course you should buy more chucks. Cliff has IIRC nine of them. You should have a 4" and a 5" each with a full range of jaws. Oh joy.

[Robomanic]

...
You should have a 4" and a 5" each with a full range of jaws. Oh joy
...

I'll be sure to inform SWMBO ASAP. :2tsup:

[RETIRED]

Ya got armour on?:rolleyes:

[Robomanic]

Just my reflexes and quick wit:D. What do you mean she is right behind meeasdg;lksjdg;lknsfdb;kgssfgngfsg.......................................................................