Heat cracks in blackwood.

[Kev Y.]

Can anyone tell me how to avoid getting heat cracks in blackwood during finishing? (apart from better tool finishing)

I have a good quantity of dry blackwood and have started making a few bowls from the stock, however I noticed that during the sanding phase, these damn cracks start to apper!.

Kev.

[ubeaut]

What you have is probably friction checking caused by too much heat from sanding. Try the following.
Lower your sanding speed.
Use good qualiy abrasive.
Use new abrasive not worn stuff.
Get a Rotary Sander (http://www.ubeaut.com.au/rotary.htm).
Cut cleaner with the tools and you won't need to sand as much.
DON'T use steel wool.
DON'T burnish the work with shavings.

Wet sasnding may be of some help.

It is also possible that the checking is in the wood from the start and doesn't become apparent until the sanding is done.

Hope this is of some help.

Cheers - Neil http://ubb.ubeaut.com.au/ubb/smile.gif

[Kev Y.]

Thanks neil however!

Lower your sanding speed. can not do just yet! lowest speed is 850 rpm. bring on the technatool dvr3000!!!!!

Use good qualiy abrasive. already do hermies(s) from carbatech

Use new abrasive not worn stuff. opps obviously not often enough!

get a Rotary Sander. used one at Vic's place, loved it but failed to buy one, already on the shoping list for October.

Cut cleaner with the tools and you won't need to sand as much. I am trying.......

DON'T use steel wool. NOPE never do

DON'T burnish the work with shavings. again never do, Vic said "DONT!!!!!!!" so I don't.

Wet sanding may be of some help will give it a try, got nothing to loose and heaps to gain.

Kev.

[BrianR]

Wet sanding with wet and dry will help.

[Sandy Johnston]

Rotary Sander - Make one -
Get 50mm dia ply about 15mm thick mount in centre gutter bolt , head recessed below surface, glue rubber 15 mm thick to this and glue velcro to that. Get velcro backed sanding paper of varoous grades.
Go to Hobby shop and get a bearing for RC car - to suit gutterbold - want tight fit.
Bore hole in handle to suit outside dia of bearing and reeces deeper for gutterbold shaft and superglue bearing in place - works a treat. Cost about $5 for bearing - ply and bolt and handle were scrap rubber was of jandle/thong.
Velcro backing from hardware - not expensive.
Make two and mount one (less bearing and handle) in elecrtic drill for "power sanding".

Regards
Sandy across the ditch

[ubeaut]

Better still stick with your plan to buy a Rotary Sander (http://www.ubeaut.com.au/rotary.htm).
The only one that really works, has a lifetime guarantee and won't get you a costly visit from the patent police. http://www.ubeaut.biz/scared.gif

Many have tried to make a better or cheaper version of the Rotary Sander but to date I am yet to find one that works even half as well, including the latest offering from Sorby.

Cheers - Neil

[Tim the Timber Turner]

Very interesting!!
I think I'll refrain from responding.

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Some days I turns thisaway, somedays I turns thataway and other days I don't turn at all.

[zathras]

Why would he get a visit from the patent police ????

As far as I understood, you can make anything for personal use, even a design freshly submitted for patent.
However if you then proceeded to SELL the item then your statement then becomes correct.

Ray

[ubeaut]

Ray - You're right of course, but it just seemed to fit in so well and lend a bit of colour and drama to the post. Legaly it is fine to copy others inventions for your own use. But morally, well I suppose if you are a tightwad, mean spirited coot then it's still fine especially being as how you usually end up with an inferior product anyway.
_________________________________________

Oh by the way if you want a power sanding head for your drill, an excellent choice are the ones made by Tim Skilton Tim the Timber Turner [email protected]

Sorry Tim Tam shoulda thunkuv that before. http://ubb.ubeaut.com.au/ubb/rolleyes.gif

Cheers - Neil http://ubb.ubeaut.com.au/ubb/smile.gif

[Kev Y.]

Personaly, I have used the ROTORY SANDER and found it a wonderful accessory, and seeing as someone else had already "invented the wheel" why should I even try..


sometimes I do try and "copy" things for my own use , most times it is just to see if I can do it.. maybe old age (44+ a bit) is setting in

Kev

[Alastair Bennetts]

850 rpm is fine, my lathe also goes no slower. I wonder if you use a pad, (leather for example) to protect your fingers? I have found that if you use the abrasive single with your fingers, you then make damn sure that it stays cool enough to prevent checking. Sanding does take a bit longer though!

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[Kev Y.]

Yes I do use a leather pad, it looks like this time it may not be such a good thing, IF my fingers get hot then there has to be too much heat in the timber.. Thanks again

[John Saxton]

Kev,I've noticed that with previous attempts on real dry hardwoods such as we have available in the Kalgoorlie/Goldfields region of West Oz, wet sanding has become a real alternative for me to temper checking with wet/dry sanding paper.
I use a small spray bottle to thoroughly dampen down the surface of the turned piece before applying the dry ...wet sanding paper.

HTH's
Cheers http://ubb.ubeaut.com.au/ubb/smile.gif

[Kev Y.]

Thanks john, I have a heap of the Blackwood left and would realy like to produce something with it, I may give the wet sanding a go on my next piece.

Kev

[Cliff Rogers]

Originally posted by Brudda:
Thanks john, I have a heap of the Blackwood left and would realy like to produce something with it, I may give the wet sanding a go on my next piece.

Kev
G'day.

Here's something else to try...
Do you have an Air Compressor?
Does it have a dryer & good CFM?
If so, try using a trigger operatered fine nozzle to blow a stream of air at the point of sanding. You have to direct it under the leading edge of the sand paper.
This does a couple of things,
a/. it keeps the paper cleaner for longer.
b/. it keeps the surface temp lower & that helps to reduce surface heat cracks.

It also does one other thing that is not so desirable... it blows fine wood dust EVERYWHERE!




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Catchya,
Cliff