Mulga wood help please

[Avery]

A friend gave me a small piece of mulga that he had been hanging on to for about 20 years. I decided to turn it into this little shot glass that you will see in the attached (not very good ) photo. It is about 100mm tall and about 50mm at its widest point.

I was very pleased with the finished product. All of my 13 weeks of woodturning experience went into it.

However...

12 hours after taking it off the lathe it had cracked in about 5 places from the rim to the base of the hollowed section. These cracks certainly did not occur during turning or finishing.

Can anyone suggest a reason why this happened?

I am thinking that maybe I overheated the thing when boring the hole (35mm forstner bit). It did get quite hot.

Any ideas?

[mkypenturner]

I am thinking that maybe I overheated the thing when boring the hole (35mm forstner bit). It did get quite hot.

Any ideas?
thats prob the answew did you bore the hole in one go or did you start small and change to a larger bit ?? if not thats why way to much heat

troy

[TTIT]

Going by the sapwood around it I'm guessing you've used a small branch so it still has the heart in it and most hard acacias in that arrangement will crack like that no matter what you do. Overheating might have made it worse but using any wood with the heart in it is always risky. For a dark acacia with bright sapwood that doesn't split like that try Yarran. Nice little shot-wood :doh: anyway :;

[Avery]

thats prob the answew did you bore the hole in one go or did you start small and change to a larger bit ?? if not thats why way to much heat

troy


I bored it in one go. I thought using a smaller bit first but I was concerned that not having a centre to bite into would allow the larger bit to wander around. It did generate a lot of heat even though the feed rate was very, very slow.

[Avery]

Thanks for that info TTIT. Your guess was dead right, it was a branch that started at maybe 100mm including the bark. I have not heard of Yarran. I will start looking.

[Ed Reiss]

Avery, shame about the split, but whatever you do, don't get rid of the turning...hold onto it then 13 years down the road you'll look back fondly at your first turning with the "13 weeks of experience" :U