Cracks after turning. PLEASE HELP!

[Wayne39uk]

Hi there everyone. I’m a relatively new Woodturner and have really enjoyed making various projects, unfortunately EVERY time I have finished a piece after around 24 hours they all develop a hairline crack or two. Less than a day after they become full blown cracks. I have tried various woods from various suppliers. I sand the piece, working through the grits, then finish with Yorkshire Grit to a great shine.
If anyone can offer any reasons or suggestions as to why the cracks appear and how to stop this I would be greatly appreciated!
Thanks for reading 👍🏼

[bodrighywood]

Main reason this happens is usually becuse the wood isn't dry before turning. You need to either dry the wood out (see other thread fpor ideas ) orpart turn leaving to dry and then finish off. The orientation of the wood you 're using also can dictate whether it will crack e.g. end grain bowls are likely to either move or crack. Also (loads of reasons LOL) different woods will be more prone to cracking or splitting as well. Fruit woods for example generally can be a pig as can laburnum and yew. Afraid it is a matter of experience and that is an ongoing thing.

pete

[Twisted Trees]

First advice is try different wood, or different wood supplier, however you said you have already tried that.

So in no particular order:-

Make sure your tools are sharp, and you slow down the lathe for sanding friction heat in the surfaces can cause distortion which becomes cracks.

Give it a day of rest after turning in the workshop, before taking it into a heated house.

Whatever thickness you cut, try to keep the entire vessel the same, not quite so important at the base but uneven wall thickness can be a cause of stress cracks.

Don't cut end grain bowls unless you are certain of the wood or it's special enough to risk it.

Maybe upload some photo's to help suggestions.

[Wayne39uk]

Thanks so much for your advice so far guys! Has been pretty frustrating spending hours covered in sawdust and clippings to have the end result crack on me.
You’ve certainly given a few new things to try.
Thanks again 👍🏼👍🏼

[Derek]

It depends on who your suppliers are if it is a tree surgeon then the wood may be still very wet in which case as Pete said rough turn then seal the outside and leave somewhere cool to dry out.
If it is from a supplier who air dries the wood again it may need rough turning and again left to dry.
Kiln dried wood should not split well not that easy.
Wood will take in moisture as well as expel it(I forget the right terminology) so be careful taking it into a centrally heated home and putting it next to a radiator

[Wood spinner]

slow down the drying process by putting your item in a sealed plastic bag for 24 hours
Then remove your turning , turn the plastic bag inside out and repeat for 24 hours

Weigh your items when turned and when the weight stops reducing it dry

Also the wall thickness needs to be uniform throughout the turning , thick and thin cause cracking as the stress withing the timder moues different amouts inducing cracks

Cracks can be design opportunity's 

[Twisted Trees]

Thanks so much for your advice so far guys! Has been pretty frustrating spending hours covered in sawdust and clippings to have the end result crack on me.
You’ve certainly given a few new things to try.
Thanks again 👍🏼👍🏼

The purpose of wood turning is to create wood shavings and sawdust, that bowl shaped bit left in the middle is actually the waste product 

It really shouldn't happen too often, your timber is key. and I suspect it is too wet, though that's  hard to understand if you have tried various sources and types.  Wood moisture meters are not expensive, it is not an exact science but somewhere around 12% and touch dry is a good start.

[windfall]

I agree with Derek Kiln dried wood should not split. If dried hardwood is stored outside in winter the moisture inside can freeze and then expand rapidly when brought inside, its rare but I've seen shakes in Brazilian Mahogany slabs, after being stored in outside overflow containers over winter.  I've no idea how to handle greenwood, but I'm learning with the help of this community, but I have put a couple of thousand feet of various hardwoods through a 4 cutter and in my experience well seasoned hardwood rarely cracks after processing.
Something I did learn from the old timers when I was an apprentice ( now don't laugh) is plank tapping. Actually holding the plank raised in one hand and tapping the wood with your finger knuckles. Its been done for 100's of years by musical instrument makers, the same way a antique dealer will tap a vase to see if its had a crack repaired. Sounds are hard to describe but a board with internal cracks makes a dull note compared with a solid piece that has no internal stress. I don't know why your wood is cracking just offering a bit of advice when you go to buy some.
Could overheating from sanding cause cracking ?
Anyway hope you solve the riddle.

[yashin57]

This happened to me regularly as a new turner and the best advice I received was to not be in too much of a rush to finish a piece. Until you have some more experience of how the wood reacts, turn some, then leave it till the day after and do some more. This lets you see how the wood is reacting to your turning, and slows down the release of any moisture. All the previous posts detail some really good advice and I would only add further that a moisture meter is a great buy and will save you money in the long run. Good luck!

Ian

[bodrighywood]

Kiln dried wood can still split. In fact is more likelty to than air dried as it can be dried too much Optimum moisture content is variable depending on where you live. I had wood I took from Cornwall (a damp county) to Wiltshire( inland) that split long after being turned and dried. As I tried to say earlier, the rules cvary too juch to be specific.

Pete

[Mike313]

I had wood I took from Cornwall (a damp county) to Wiltshire( inland) that split long after being turned and dried.

As a beginner, I didn't know that could happen. Excuse my ignorance (don't laugh) but what happens if someone buys a bowl whilst on holidays in Cornwall and then takes it home to Wiltshire or any other drier county?

[bodrighywood]

I had wood I took from Cornwall (a damp county) to Wiltshire( inland) that split long after being turned and dried.

As a beginner, I didn't know that could happen. Excuse my ignorance (don't laugh) but what happens if someone buys a bowl whilst on holidays in Cornwall and then takes it home to Wiltshire or any other drier county?

It could happen that it moves or splits but depends on the wood as much as anything. The piece that split on me was yew and had been turned green initially. It obviously didn't dry out as much as it eventually did in Wiltshire. It isn't something to worry about really, just trying to show that 'how dry to turn wood' is one of those 'how long is a piece of string' questions.

pete

[michaelb]

I know we are all keen see the finished bowl but I have found the best way is to rough out shape, keep for 12 months depending on thickness , then return to the lathe, the only exception would be Burrs.  Also ask yourself the question why does old furniture crack and alter shape central heating great for furniture restorers. 

[bodrighywood]

The furniture company my wife designed for stopped selling fitted pine furniture to the states as they aften have 0 humidity in their air conditioned homes and the wood moved as much as an inch over a month or so after fitting.

Pete

[Twisted Trees]

Wayne39uk, Despite all the potential horror stories, you do need some easy success in your turning. and the reality is I turn all sorts of things and find light weight bowls while fun to make, are disappointing in reality. One of my old tutors once told me if you throw an apple into the bollw and it tips over it isn't a fruit bowl! So the majority of bowls I turn are at least 5mm  thick in the wall with 10mm thick bases, so forget the thin walled easy distorted types for now.

Get a moisture meter (about £12)
Get yourself a nice easy piece of wood, something interesting like Yew or Ash that show somewhere between 10% and 15% on the meter.
DONT do an end grain bowl, they can be a problem.
Turn it to about 5mm wall thickness with very sharp tools.
Sand it at slow speed with your fingers not with a pad. if your fingers get warm, so is the wood!
Leave it on the lathe overnight, and Yorkshire grit it the next day (it may have distorted overnight so don't try cutting it again just polish)
Put it in the kitchen for at least 2 days the variable humidity and heat in the kitchen I find is a great settler of newly turned items.

Have a WIN! we all need those.

If you are still having problems post some pictures, and I am sure that help will be offered.

Good luck and happy turning