hollow form blow out!

[smiife]

Hi all,
I had a nice myrtle burl blank which I had turned
a couple of weeks ago, so I put it back on to hollow out
on the weekend , all going well and then I noticed
shavings coming out the side ,,,,,,, oooooooppppppsssss!!!!!!!
This is the second time i have done this and was
wondering if anyone could tell me what i am doing
or not doing wrong?
Put up a couple of pics,,, any help would be appreciated

[Jim Carroll]

it is one of the most common areas for going through,

It has the sound of beign thicker than it acually is.

It is the old saying measure twice cut once.

[ian thorn]

Just looking at the photo it has only come out on one patch looks to me you may have a bit of run out ( wobble ) as well as what Jim just said take it slower stop and measure often

[TTIT]

it is one of the most common areas for going through,

It has the sound of beign thicker than it acually is.

It is the old saying measure twice cut once.It's also the area that is easiest to hit and take heavier, controllable cuts. What are you measuring with Smiife??? :think:

[Paul39]

Bore a hole in this one, put a contrasting tapered plug in it, and carry on.

Nice piece, nice figure, don't give up on it.

http://www.woodworkforums.com/attachment.php?attachmentid=327545&stc=1&thumb=1&d=1406971184

You could make or buy a laser guide. In the US one can buy a laser pointer for $5 - $10. Make a bracket to point at the end of your hollowing tool.

Expensive laser guided hollowing tools:

http://www.onewayeuropa.com/hollowing/

https://www.google.com/search?q=laser+guide+for+hollowing+forms&biw=1024&bih=615&tbm=isch&tbo=u&source=univ&sa=X&ei=ugc0VO_mM7iKsQT2iYLgBw&ved=0CDkQsAQ

[chuck1]

It does look like one partial cut of the tool with some run out, did you have a catch? How fast was the rpm?

[Tangoman]

Smite,

really wish I hAdnt seen this post, I've got a very similar one on my lathe which pushing my skills a bit too far ! Am terrified of blowing it up !! LOL.

i will be making a laser guide fitting soon for my tools, you can get a cheap laser pointer from Jaycar and Officeworks - fwiw.

Regards,
Cam

[Paul39]

Smiife,

The blank may have shrunk a bit in that area in the week it was off the lathe, or it may have shrunk more on one side and bent the piece over,making the opposite side thinner when you hollowed. The spigot may have shrunk more on one side making the piece go off center.

Or any or all of the above.

I have had "dry" partially finished pieces move all over the place when left in the lathe overnight. The more interesting the figure, the more they tend to move.

[Dalboy]

Not always possible but try and turn the whole thing in one day. Like others have said measure frequently and not just in the same spot

[Rod Gilbert]

I totally agree with Paul39 timber movement most likely way this happened with the time delay from start to finish. If you need to do in stages only rough out and leave plenty of meat to then finish the remaining cuts all at the one time.
Regards Rod.

[smiife]

Hi guys,
In a general reply to everyone,
as to movement i bought this blank quite a long time ago
as you can see it was waxed on all sides, and i thought it
was dry.
time is always a problem for me and i don, t always get
to finish a project in one session, so is it best to leave a project
on the lathe or take off and try get it centred again?

Laser pointer ! might have to look into that one!

Speed and measuring?? Not too sure on either
maybe 1200 /1500 rpm,,, and no I did not measure
with anything..but i will be next time:doh:............
No catch...i used my hollower

Thanks again for your comments and advice
much appreciated

[Paul39]

Smiife,

My jaundiced opinion of waxed blanks is the seller hopes they won't split until they are sold.

I assume that anything I turn, mostly bowls, is going to move if left overnight, a week, or a month. If I'm going to be back to a bowl within a week, I leave it on the lathe. If the timber is fresh cut, it may rust the chuck, so I take those off.

I got busy with my smaller lathe and left a roughed out bowl of semi dry palm trunk on the big lathe for over 6 months. It twisted all over the place. I had left plenty of thickness so it will be OK.

The "dry" blanks I rough turn leaving the thickness about 5 to 10 % of the diameter, leave it over night and if not too warped take some more off and set it aside for a week or more, then finish.

The found-on-ground or fresh cut pieces I rough out with a thickness of 10 to 20% of the diameter and boil, or soak in dish washing liquid and water for two weeks, or not treat. Then I wrap in several layers of newspaper and let dry for 6 months or longer. They move all over the place and become oval shaped. Then I treat as above for "dry" blanks.

I assume that all timber moves when roughed out, some more than others.

Straight grained kiln dried cherry, maple, or walnut moves the least. Straight grained timber is the least interesting to me. Crotches, stumps, and burls are the most interesting to me and the least stable.

[joe greiner]

A steady rest could cure a lot of those ills.

Cheers,
Joe

[Rod Gilbert]

Hi Smiife and all,

Movement is not only from moisture content perfectly dry timber can move considerably simply by the process of removing material from the piece and the resulting release of stresses in the timber can cause serious deflection in the circumference and vertical plane. (as for speed $13.00 digital taco is pretty simple)
Regards Rod.

[smiife]

Smiife,tMy jaundiced opinion of waxed blanks is the seller hopes they won't split until they are sold.

I assume that anything I turn, mostly bowls, is going to move if left overnight, a week, or a month. If I'm going to be back to a bowl within a week, I leave it on the lathe. If the timber is fresh cut, it may rust the chuck, so I take those off.

I got busy with my smaller lathe and left a roughed out bowl of semi dry palm trunk on the big lathe for over 6 months. It twisted all over the place. I had left plenty of thickness so it will be OK.

The "dry" blanks I rough turn leaving the thickness about 5 to 10 % of the diameter, leave it over night and if not too warped take some more off and set it aside for a week or more, then finish.

The found-on-ground or fresh cut pieces I rough out with a thickness of 10 to 20% of the diameter and boil, or soak in dish washing liquid and water for two weeks, or not treat. Then I wrap in several layers of newspaper and let dry for 6 months or longer. They move all over the place and become oval shaped. Then I treat as above for "dry" blanks.

I assume that all timber moves when roughed out, some more than others.

Straight grained kiln dried cherry, maple, or walnut moves the least. Straight grained timber is the least interesting to me. Crotches, stumps, and burls are the most interesting to me and the least stable.

Hi paul
Thanks for your thoughts, very much appreciated:2tsup:



A steady rest could cure a lot of those ills.

Cheers,
Joe
Hi joe,
Not too sure where you are going with that ?:no:


Hi Smiife and all,

Movement is not only from moisture content perfectly dry timber can move considerably simply by the process of removing material from the piece and the resulting release of stresses in the timber can cause serious deflection in the circumference and vertical plane. (as for speed $13.00 digital taco is pretty simple)
Regards Rod.

Hi rod,
I think that is what has happened,
as for the speed I just turn It up to what i think is safe!

[BamBam53]

Hi Smiife. Don't feel bad about the blow out. I was watching Phil Irons demonstrate last weekend and he did the same thing.

[Lyle]

Bugga jinxed me too. Did the same on a job I had going. Was concemtrating on one spot and shaped the wall too thin.
But I think I can recover with a bit of fiddling.
Good luck with yours.
Maybe cut it off and insert a contrasting ring and put back together?
Lyle.

[Allen Neighbors]

Smife, one thing I have had pretty good success at when I have to leave it on the lathe: I bag it with a plastic bag, and tie it with string around the base where it mounts on the chuck. I make sure there is as little air as possible left in the bag (squeeze it around the piece).
When I am turning a piece, if the wood is green (like most purchased, waxed timber), I try to get the outside of the piece shaped in one spate of turning. Then I spray the outside of it with soapy water, using an old 409 bottle. Then I bag it, if I have to leave it on the lathe. While I'm hollowing the inside, I keep the outside wet with the soapy water. It slings a lot of soapy water around the shop, but if you lay a towel on the ways it'll keep 'em from rusting...
Keeping the outside wet until you get the inside hollowed, keeps the piece from getting out of round or warping into a wobble, which will cause one part to get thinner than another, making it easy to get blow-outs.
Sort of puts a kink into finishing on the lathe, being wet, but that's the way it is... :)
Al

[smiife]

QUOTE=BamBam53;1813163]Hi Smiife. Don't feel bad about the blow out. I was watching Phil Irons demonstrate last weekend and he did the same thing.[/QUOTE]

Hi bambam,
Thanks for that, I am not too bothered by it,
just put It down to experiance, shame though
It was a nice piece of burl


Bugga jinxed me too. Did the same on a job I had going. Was concemtrating on one spot and shaped the wall too thin.
But I think I can recover with a bit of fiddling.
Good luck with yours.
Maybe cut it off and insert a contrasting ring and put back together?
Lyle.

Hi lyle,
Thanks , I will leave it on the shelf for now
and see what inspiration comes to me:U



Smife, one thing I have had pretty good success at when I have to leave it on the lathe: I bag it with a plastic bag, and tie it with string around the base where it mounts on the chuck. I make sure there is as little air as possible left in the bag (squeeze it around the piece).
When I am turning a piece, if the wood is green (like most purchased, waxed timber), I try to get the outside of the piece shaped in one spate of turning. Then I spray the outside of it with soapy water, using an old 409 bottle. Then I bag it, if I have to leave it on the lathe. While I'm hollowing the inside, I keep the outside wet with the soapy water. It slings a lot of soapy water around the shop, but if you lay a towel on the ways it'll keep 'em from rusting...
Keeping the outside wet until you get the inside hollowed, keeps the piece from getting out of round or warping into a wobble, which will cause one part to get thinner than another, making it easy to get blow-outs.
Sort of puts a kink into finishing on the lathe, being wet, but that's the way it is... :)
Al
Hi al,
Yeah thanks for your thoughts, I must try the bag
and wet spraying idea, will let you know how i go!