Runaway bowl

[Fumbler]

Just curious to hear if anyone has experienced a bowl blank in a scroll chuck coming off the lathe at speed, chuck and all?

i had a relative from the UK with me last week and was given some time in the shed to make a gift, I had a small block of Coolabah burl cut almost round ready to turn. I put the worm screw into the jaws and whilst I was cutting the recess to reverse in the chuck, the eccentricity of the block, caught the tool and then proceeded to pop off the spindle, bounce once or twice on the path bed before darting across the floor. As I was standing to the right of the jobabd facing the lathe almost end on, I was well out of the way. The tool rest also helped deflect the piece away from me.

i am still at a loss as to how, with counter rotating thread. Ie locking the chuck onto the lathe as it spins, that it can effectively come undone? This has happened twice now, and still don't believe it. I can believe a catch to be forceful enough to free the job from the jaws, but not free the chuck also!!?

can anyone suggest as to how it can reverse direction and undo? Luckily once the dismount had occurred it lost a lot of momentum, as was turning at a relatively low speed 1000rpm.

???

[Skew ChiDAMN!!]

Something is seriously not right.

I've had similar situations when I've spun up a heavy blank and turned the lathe off. The motor/shaft stopped but the blank kept on spinning, unwinding the chuck.

But never, ever from a catch except when I was running the lathe in reverse. I do not do that any more, not even for sanding. :no: Reverse is much over-rated.

The only suggestions I can come up with are:

A: there is a mismatch between the chuck thread and the spindle thread. ie. it's tight enough to "feel" secure but a good sharp blow reveals that it isn't.

B: If you have a variable speed lathe, a heavy(ish) blank and the chuck isn't properly tightened on the spindle at the start, IF after bringing up to full speed you drop the speed drastically (and quickly) the chuck could possibly unwind similar to my "stop situation."

I find the latter doubtful, particularly if you're using tailstock support, but still... I imagine it's possible.

Either way, I'd assume A and double- & triple-check the thread sizes if, as you say, it's happened before. If they seem to be correct and your chuck has an adapter insert, I'd actually order another one just in case of a mfrs flaw.

I wouldn't worry about B until I'm absolutely sure it isn't A, then I'd just make sure the chuck is properly locked to the spindle every time I used it. This is a good habit to pick up anyway.

Hint: If it has a grub screw to lock the chuck thread to the spindle, try removing it and dropping a lead shot down the hole, before replacing the grub screw. ;)

[NeilS]

I've had similar situations when I've spun up a heavy blank and turned the lathe off. The motor/shaft stopped but the blank kept on spinning, unwinding the chuck.


Ditto. With very heavy blanks (30kg+) I have to remember to dial down the speed before hitting the stop button.

A very thin rubber washer between the chuck insert and the shoulder on the headstock spindle reduces the risk of overrun, but introduces its own issues if not removed once the weight has been taken out of the blank.




Reverse is much over-rated.



Agreed! Had it on some of my earlier lathes but didn't include it as a requirement when selecting my most recent lathe.




Sent from my ZTE T84 using Tapatalk

[Mobyturns]

Something is seriously not right.

I agree.

Time to relearn the basics. Stuart Batty offers good advice and well reasoned guidance on the how and why -
https://vimeo.com/woodturning

https://vimeo.com/137484615

[Fumbler]

Something is seriously not right.

I've had similar situations when I've spun up a heavy blank and turned the lathe off. The motor/shaft stopped but the blank kept on spinning, unwinding the chuck.

But never, ever from a catch except when I was running the lathe in reverse. I do not do that any more, not even for sanding. :no: Reverse is much over-rated.

The only suggestions I can come up with are:

A: there is a mismatch between the chuck thread and the spindle thread. ie. it's tight enough to "feel" secure but a good sharp blow reveals that it isn't.

B: If you have a variable speed lathe, a heavy(ish) blank and the chuck isn't properly tightened on the spindle at the start, IF after bringing up to full speed you drop the speed drastically (and quickly) the chuck could possibly unwind similar to my "stop situation."

I find the latter doubtful, particularly if you're using tailstock support, but still... I imagine it's possible.

Either way, I'd assume A and double- & triple-check the thread sizes if, as you say, it's happened before. If they seem to be correct and your chuck has an adapter insert, I'd actually order another one just in case of a mfrs flaw.

I wouldn't worry about B until I'm absolutely sure it isn't A, then I'd just make sure the chuck is properly locked to the spindle every time I used it. This is a good habit to pick up anyway.

Hint: If it has a grub screw to lock the chuck thread to the spindle, try removing it and dropping a lead shot down the hole, before replacing the grub screw. ;)

Cheers Skew,
A. i'll check, as is probably the cause
B. It is a variable speed but the lathe was still in motion, and not slowing down

I wasn't using the tailstock as I was cutting the recess for the jaws. I know my face plate has a grub screw but not my insert or scroll chuck.

my only thought was the catch has somehow increased the speed of the job/chuck, and its ended up spinning faster than the lathe and therefore undone itself. or the catch has thrown the job off balance and the insert has somehow dislodged and jumped off the spindle. I will check to see i its cracked or split.

but its happened twice now, so might take the chuck/insert back to the shop and test on their lathe to see if it fits correctly.

I will keep you posted

[Colin62]

If the insert is loose enough to jump off the spindle, it’ll probably wobble a fair bit before it registers and tightens up.

[Mobyturns]

Has the project been completed?

Rather than dribble pieces of information could you supply some key basic information as it will be helpful for others to interpret what occurred and hasten the elimination process. A photo/s of the blank as mounted on the lathe, lathe set up, belt positions will also greatly assist.



Lathe make & model
Fitted with EVS / VFD - Y or N , original, aftermarket?
Fitted with Fwd / Rev - Y or N
Chuck make & model
How was the chuck / insert initially fitted to the spindle i.e. just firm, snugged up, spun on with force....
Was any lubricant used on the spindle / insert thread interface?
lathe speed
belt position (1,2,3 etc or L, M, H )
blank dimensions
tool in use when the event/s occurred
was the lathe motor, or has it been, "stalling" during turning, of this or similar sized projects?
which side of the lathe bed did the blank "fly" to - near or off side?
finally to eliminate "dumb" mistakes - lathe direction i.e. fwd or reverse. (we all make mistakes.)


If a lathe has EVS and is "underpowered" i.e. not enough grunt or the wrong belt setup is used, it is possible to stall the lathe motor with a "soft catch" (a progressive stalling rather than an abrupt stall/stop), reducing the spindle / blank RPM. When the turner reacts :oo: and withdraws the tool the EVS recovers and attempts to return to the selected / dialled speed and increases the spindle / blank RPM.

Most EVS setups are programmed to "ramp up" torque within limits to overcome stall conditions. So it is possible that the combined blank / chuck / insert that is loosely fitted to the lathe spindle may momentarily reach a temporary "overspeed" condition i.e. faster than the lathe spindle, and then becomes loose on the lathe spindle as the EVS recovers to the set speed. This can be a significant issue with larger bowl or platter projects that test the limits / power of mini / midi / cheap lathes and is alarmingly easy to do on any lathe running in "reverse".

The same occurs when a turner uses their hand as a brake on the hand wheel to abruptly slow the lathe spindle, the spindle slows however the inertia / momentum of the insert / chuck / blank overcomes the friction of either the spindle / insert or insert / chuck interface and "goes for a walk."

If its not fitted with EVS and "hand braking" was not involved then I'm :?:?:?

However if recommended practices, lathe speed etc are being observed and good techniques are employed, lathe setup checks performed before turning the lathe on, this should never occur. :2tsup:

It will be interesting to hear what the cause of this issue turns out to be. Simply a process of elimination.


Using large chucks on small lathes also creates a potential hazard due to the relative mass of the combined chuck and blank compared to the mass of the lathe itself. Inertia causes some "interesting situations" with light lathes sitting upon temporary benches - i.e. topple over.

[Fumbler]

Has the project been completed?

Rather than dribble pieces of information could you supply some key basic information as it will be helpful for others to interpret what occurred and hasten the elimination process. A photo/s of the blank as mounted on the lathe, lathe set up, belt positions will also greatly assist.



Lathe make & model
Fitted with EVS / VFD - Y or N , original, aftermarket?
Fitted with Fwd / Rev - Y or N
Chuck make & model
How was the chuck / insert initially fitted to the spindle i.e. just firm, snugged up, spun on with force....
Was any lubricant used on the spindle / insert thread interface?
lathe speed
belt position (1,2,3 etc or L, M, H )
blank dimensions
tool in use when the event/s occurred
was the lathe motor, or has it been, "stalling" during turning, of this or similar sized projects?
which side of the lathe bed did the blank "fly" to - near or off side?
finally to eliminate "dumb" mistakes - lathe direction i.e. fwd or reverse. (we all make mistakes.)


If a lathe has EVS and is "underpowered" i.e. not enough grunt or the wrong belt setup is used, it is possible to stall the lathe motor with a "soft catch" (a progressive stalling rather than an abrupt stall/stop), reducing the spindle / blank RPM. When the turner reacts :oo: and withdraws the tool the EVS recovers and attempts to return to the selected / dialled speed and increases the spindle / blank RPM.

Most EVS setups are programmed to "ramp up" torque within limits to overcome stall conditions. So it is possible that the combined blank / chuck / insert that is loosely fitted to the lathe spindle may momentarily reach a temporary "overspeed" condition i.e. faster than the lathe spindle, and then becomes loose on the lathe spindle as the EVS recovers to the set speed. This can be a significant issue with larger bowl or platter projects that test the limits / power of mini / midi / cheap lathes and is alarmingly easy to do on any lathe running in "reverse".

The same occurs when a turner uses their hand as a brake on the hand wheel to abruptly slow the lathe spindle, the spindle slows however the inertia / momentum of the insert / chuck / blank overcomes the friction of either the spindle / insert or insert / chuck interface and "goes for a walk."

If its not fitted with EVS and "hand braking" was not involved then I'm :?:?:?

However if recommended practices, lathe speed etc are being observed and good techniques are employed, lathe setup checks performed before turning the lathe on, this should never occur. :2tsup:

It will be interesting to hear what the cause of this issue turns out to be. Simply a process of elimination.


Using large chucks on small lathes also creates a potential hazard due to the relative mass of the combined chuck and blank compared to the mass of the lathe itself. Inertia causes some "interesting situations" with light lathes sitting upon temporary benches - i.e. topple over.



Firstly, yes the job is complete, a small 90mm x 60mm cool mint bowl, in coolabah burl.

1.Hafco WL-14
2. EVS - fitted - no hand brake was being applied.
3. Reverse - fitted
4. Hafco 100mm scroll chuck
5. Hand rotated snug fit, no play.
6. No lube
7. 1000rpm
8. 2 belts, on 2nd belt for higher end polishing.
9. An off- round reversed burl blank roughly 120mm diameter. on the worm screw until I could true the outside and face then set the jaw recess
10. Roughing gouge
11. No, it hasn't been stalling, but that was twice on the same blank several weeks apart
12. Near side and down, it hit the bed rolled off and round my feet. I was standing to the right.
13 normal anticlockwise direction.

i think the stall may be it because it shuddered and then went plop.

i will take the chuck/insert back to the shot and fit instore to see if I get the same feel.

cheers

[Mobyturns]

Well the mystery deepens. That is a small blank (bowl wise) so it does not have the issues of large mass to create the situation I had envisioned. Nothing really untoward for that size blank, unless the chuck was not snugged up well enough to start with. The use of a roughing gouge is not generally recommended for "bowl blanks" however if it was genuinely a burl blank the "cross grain" effect is not really present.

As the bowl is now finished, what did you change to successfully complete the bowl?

[Fumbler]

Well the mystery deepens. That is a small blank (bowl wise) so it does not have the issues of large mass to create the situation I had envisioned. Nothing really untoward for that size blank, unless the chuck was not snugged up well enough to start with. The use of a roughing gouge is not generally recommended for "bowl blanks" however if it was genuinely a burl blank the "cross grain" effect is not really present.

As the bowl is now finished, what did you change to successfully complete the bowl?

I basically put the chuck back onto the spindle, made sure that it was snug and kept going, but as it had happened twice on the same block, I thought it best to true it up asap. Although it was a small bowl blank it was quite off kilter until I trued it up.

i will go through the steps you discussed and take it back to the shop and check it out.

[Fumbler]

Further to this, the thread is good, there is no play, and the insert seats snugly on the spindle. Also, there is no lug screw to tighten to lock the insert on.

448134 448135

[woolclasser]

why are you using a roughing gouge on a bowl. they are designed for spindle use only. what happened was that the roughing gouge caused a catch. momentarly stopped the machine and caused the chuck to spin loose. you were lucky that you didn't do more serious damage. i suggest that you look at the video by retired that is in a sticky at the top of this page. it might save you from getting hurt.
cheers
jim

[Nubsnstubs]

What happened there is certainly a mystery to me. You are right as turning counter clockwise should not unscrew anything even with a complete stop. Your tool caused and stopped all forward motion. If anything, it should have tightened the chuck even tighter on the spindle.

I'm surprised that the chuck doesn't have a grub screw to lock it onto the spindle or insert. If you have a drill press, drill out a hole on the insert and tap it for a grub screw. But looking at the pictures of your chuck, there doesn't seem to be enough room on it to put a grub screw, which is needed to keep it on the spindle.

I'm only familiar with Nova Chucks, and haven't seen any without a grub screw. I did buy inserts and tapped them for grub screws. It's pretty simple to do. ................. Jerry (in Tucson)USA

I took a look at the chuck you posted. You probably could take that index plate off, and locate where you could drill into the chuck and tap a hole for a grub screw without interfering with the mechanics of the chuck operation.
I did that to my Nova G3 chucks because the 1/4" screws interfered with the chuck key. It's pretty simple if you have a drill press and a vise............ Jerry

[Mobyturns]

Any update o the insert threads matching the spindle thread etc?

[Fumbler]

I haven't been able to get out to H&F yet, but apparently this lathe is synonymous for this kind of activity. I went to my club and asked if anyone had experienced this issue. It was met with laughter. Then they said, yep, there, there and there, and proceeded to point 3 holes it the ceiling from just that issue. They then said, now look at the lathe and read the sign. It said "chuck permenamtly attatched, do not remove".
I instantly felt relief, and happy that this was not an isolated incident, I will however now be looking into fixing a grub screw.

[Mobyturns]

I haven't been able to get out to H&F yet, but apparently this lathe is synonymous for this kind of activity. I went to my club and asked if anyone had experienced this issue. It was met with laughter. Then they said, yep, there, there and there, and proceeded to point 3 holes it the ceiling from just that issue. They then said, now look at the lathe and read the sign. It said "chuck permenamtly attatched, do not remove".
I instantly felt relief, and happy that this was not an isolated incident, I will however now be looking into fixing a grub screw.

:?:?:?:?

Have they raised this with the suppliers? I presume the club has modified the lathe/chuck to create the
"chuck permanently attached, do not remove" as the manual shows it supplied with MT2 and faceplate.

[Fumbler]

That's a good point. I may do when I go out to H&F.

[ubeaut]

Hello Fumbler

Couple of simple questions:




How long have you been turning?
Were you using a screw chuck in that bigger chuck to hold the timber onto the lathe?
Did the blank come off or the entire chuck?


If it was the blank and you were using a screw chuck or single screw fitting to hold the blank, the simple answer will be that the thread for the screw chuck was stripped due to the catch. Easily done especially if you are using the wrong tool, which you were.

If the entire chuck came off then there is a real problem because that's impossible unless you stopped the the motor instantly.

If you weren't using a screw to hold the piece onto the chuck and didn't have the tail stock up against the blank how was it being held?

Good idea to put a machined metal or perspex washer/spacer (about 3mm thick) on the drive spindle and the chuck either will seat the chuck better and stop it from coming off in an emergency stop (unless it's very heavy) will also make it easier to break the seal to take chuck off later on.

Been using both on lathes for around 40 years and only ever had one thing wind itself off when lathe was stopped and that was a 6 ft diameter table top 40 mm thick. Nothing was ever going to stop that sucker from coming off. That incident was before I started using the washer/spacer.

Just as an aside the pics you put on look like there are different inserts in each photo. Is that correct or just an optical illusion?

Cheers - Neil :U

[Fumbler]

Neil,

with this lathe, about 6mnths, in total about 8yrs, by no means would I call myself a pro, but steady as she goes and I manage to turn out a few nice pieces .

I had the blank tightly on the worm screw in the jaws of the scroll chuck.

The ENTIRE CHUCK WTH BLANK still firmly attached to the worm screw (which is now subsequently bent) came off.

I have never seen it before, and due to the nature of the forces vs threads etc, spindle rotating counter clockwise, thread clockwise, that the momentum of the rotation will keep everything in place, well I this instance, it doesn't seem to be the case.

The blank was only about 120mm diameter and 80mm long, and as the chuck is only rated to 2000rp, and being off centre slighty (I had roughly rounded on band saw) I didn't crank up the revs.

I like everything about this lathe except how it stops, most coast to a stop, cut the power and it slows down, this stops dead, no ifs buts or hey lets take a breather, it stops.

I want to try and replicate it but next time may cause me some damage so i'm taking it easy when turning using the chuck and no tail stock

I have recently asked on here about washers and most said they dont use them, so i may just make one to fit. I have some perspex laying around. But I am also still going to speak to the manufacturer about my experience.

[Colin62]

This has been puzzling me - each time I read this thread I leave unsatisfied, because I’ve not been able to come up with a plausible scenario that would explain what happened.

Now knowing that the lathe is braked, and quite heavily by the sound of it, perhaps the catch slowed the lathe down, the lathe tried to recover the speed, drawing start-up levels of current, which caused the breaker to trip, which in turn caused the brake to stop the lathe, allowing the chuck to spin off. The problem is that a catch big enough to stop the lathe would have tightened the chuck up quite nicely even if it was slightly loose.

Does that sound feasible to anyone else or am I bending physics to make it fit?

I suppose it would help knowing how the lathe brakes itself.

[NeilS]

I have recently asked on here about washers and most said they don't use them, so i may just make one to fit. I have some perspex laying around.




Good idea to put a machined metal or perspex washer/spacer (about 3mm thick) on the drive spindle and the chuck either will seat the chuck better and stop it from coming off in an emergency stop (unless it's very heavy) will also make it easier to break the seal to take chuck off later on.



When turning larger pieces (like 40kg) outboard on an earlier lathe I had problems with the faceplate/chuck unwinding when stopping. I found a very thin rubber washer worked best (for me) in minimising that problem. Rubber won't give you as accurate a seating on the headstock shaft as metal as the variation in the density/compression of the rubber can give rise to a small amount of runout on larger diameter pieces. This could be a problem if your work involves multiple re-chucking or re-fixing to the lathe. But, that was less of a problem for me than than having a 40kg piece take off across the workshop.

I've not found the need for a washer/spacer since moving over to electronic variable speed control lathes, which allow you to dial down the speed before stopping. However, a malfunctioning EVS unit could also create the problem.

[Treecycle]

Did your lathe stop itself after the catch or was it still spinning? EVS lathes that have a braking function usually ramp down slowly, not stop instantly like you say yours does. I think you have a fault there if that's what it does.

[Kbeitz]

I had a 30# 4 jaw chuck come off my metal lathe.... Does that count ?

[Fumbler]

I had a 30# 4 jaw chuck come off my metal lathe.... Does that count ?

If you found the reason why it came off and it can help me figure out, then yes, it does count.

[Kbeitz]

It was all my fault... I was in a hurry and chucked my 4 jaw chuck inside
my huge 3 jaw chuck and it was not centered. Only two jaws was doing the
holding. Things got exciting for a while. No harm done,.

[Fumbler]

Well a quick trip to H&F today and I have discovered they were in the process of contacting purchasers of a circuit board issue which needs replacing. After showing them the video of my machine in action, they were concerned due its sudden stop, not step down.

it still doesn't explain how the chuck came in motion, but would still be interested to hear what they think of my lathe and whether it's s lemon or not. The 2 definitely sound different when running, but again, doesn't explain counter-acting threads undoing whilst in motion.

best I nip the chuck up with a spanner tightly in future, and or drill/tap a hole for a grub screw.

[Mobyturns]

Well a quick trip to H&F today and I have discovered they were in the process of contacting purchasers of a circuit board issue which needs replacing. After showing them the video of my machine in action, they were concerned due its sudden stop, not step down.

it still doesn't explain how the chuck came in motion, but would still be interested to hear what they think of my lathe and whether it's s lemon or not. The 2 definitely sound different when running, but again, doesn't explain counter-acting threads undoing whilst in motion.

best I nip the chuck up with a spanner tightly in future, and or drill/tap a hole for a grub screw.

The best advice and action is not to use the lathe until the issues are fully resolved.

This is pretty much as I expected in my post #7 - strong braking, however with only the chuck and a very small blank involved I still find it very perplexing. There have to be other issues at play as well - not "firming up the chuck on the spindle" etc.

Usually these events are not entirely due to one single issue, more a combination of several "small and un-concerning" issues providing the "perfect storm."

[Fumbler]

The best advice and action is not to use the lathe until the issues are fully resolved.

This is pretty much as I expected in my post #7 - strong braking, however with only the chuck and a very small blank involved I still find it very perplexing. There have to be other issues at play as well - not "firming up the chuck on the spindle" etc.

Usually these events are not entirely due to one single issue, more a combination of several "small and un-concerning" issues providing the "perfect storm."

agreed, and i wont be doing any turning til its been seen to. But again, a perfect storm twice? thanks.

[Woodcrafts_UK]

May I suggest a possible cause for the chuck being able to come off the lathe. Having tried to find the specs for this lathe, I found it stated as M30 x 3.5. Many lathes use the more common M33 x 3.5 (T38) size. Is it possible you have the wrong insert? The slight difference will give a reasonable hold if you just mount the chuck by hand but a catch could well loosen it.
And as a woodturning instructor, PLEASE never use a spindle roughing gouge on a bowl blank. Most SRGs are forged tools so have a relatively small tang that cannot withstand the extra effort cutting cross grain. You run the risk of snapping the tool, and the very last thing you want is half a steel chisel come flying at you.

[Optimark]

May I suggest a possible cause for the chuck being able to come off the lathe. Having tried to find the specs for this lathe, I found it stated as M30 x 3.5. Many lathes use the more common M33 x 3.5 (T38) size. Is it possible you have the wrong insert? The slight difference will give a reasonable hold if you just mount the chuck by hand but a catch could well loosen it.

Firstly, welcome to the forum.

In Australia, for whatever reason, we use the M30 x 3.5 spindle thread as a de-facto standard. The rest of the world pretty much uses the slightly larger M33 x 3.5 spindle thread, meaning it makes life difficult to get some turning stuff that screws onto spindle threads here. I wish we did use the M33 x 3.5 in this country, it would make buying some stuff from overseas possible.

Having actually used a lathe with an M33 x 3.5 thread alongside another lathe with M30 x 3.5 thread, I can state it is virtually impossible to get the larger female onto the smaller male.

The English company, Record Power, are, to the best of my knowledge, currently the only manufacturer/supplier of lathes in this country that have M33 x 3.5 on their spindle threads, everyone else has M30 x 3.5.

Mick.

[Fumbler]

I can state it is virtually impossible to get the larger female onto the smaller male.

Very true, in life also

[Fumbler]

May I suggest a possible cause for the chuck being able to come off the lathe. Having tried to find the specs for this lathe, I found it stated as M30 x 3.5. Many lathes use the more common M33 x 3.5 (T38) size. Is it possible you have the wrong insert? The slight difference will give a reasonable hold if you just mount the chuck by hand but a catch could well loosen it.
And as a woodturning instructor, PLEASE never use a spindle roughing gouge on a bowl blank. Most SRGs are forged tools so have a relatively small tang that cannot withstand the extra effort cutting cross grain. You run the risk of snapping the tool, and the very last thing you want is half a steel chisel come flying at you.

I have been to the shop, and can catagoricslly say I have the correct insert. But as for the roughing gouge, I can't say whether I was using it or not, but the shock of it coming off and chasing me feet across the floor concerned me a touch.

i haven't spun any odd shaped blanks up lately and am also nipping the chuck up tight and all seems apples. But will know when I get back from the EVS circuit board being replaced next week.

Thank you

[NeilS]

And as a woodturning instructor, PLEASE never use a spindle roughing gouge on a bowl blank. Most SRGs are forged tools so have a relatively small tang that cannot withstand the extra effort cutting cross grain. You run the risk of snapping the tool

I fully agree!

There are a few exceptions. The old P&N SRGs had a hefty milled tang, as does Doug Thomson's special order SRG. Also, Carter & Sons.

However, the other reason is that few turners have the necessary skills to manage the large potential cut of a SRG on a bowl blank (cross grain), especially with a 1-1/4" SRG. Keep in mind that SRGs don't have the flute profile or the typical swept back grind of a bowl gouge, which are optimised for bowl turning. Using a straight across grind would be courting disaster.

If you need a larger gouge for bowl work, start with a 3/4" BG and see how you go. If you get comfortable with that and you think you need even bigger shavings, the next step up from there is a 1" BG, but they are a bit hard to come by (Crown does/did make one).
There might be a very good reason why they are not being made, other than price...:stars:

[Fumbler]

I think we're getting off track, it's not my incompetence or choice of gouge to use on a 100mm diameter block of burl.

there was something that happened that made the blank and chuck spin faster than the lathe and unscrew the chuck.

besides, I have had many a catch with all manner of gouges, whether it be not addressing the timber correctly, incorrect angle etc. I by no means am a professional and don't claim to be. I haven't had a blank spin off at 3k rpm and go through a window, nor have I had a job break up on me and chunks go flying.

ill chalk this one down to the unexplained and move on, tightening the chuck fiercely, and using the tail stock for longer than necessary.

[NeilS]

I think we're getting off track, it's not my incompetence...

Sorry, Fumbler, if you thought I was implying any incompetence on your part. Far from it!

And, apologies for taking the thread further off topic.

As Woodcrafts_UK had raised the roughing gouge matter in his post I felt I must comment on that and not just leaving it hanging there. My comments were in no way directed at you. I tend to make my comments broadly to anyone who is currently reading the forum or to those who might be reading it in the future. It's my small contribution to fellow woodturners, for what they may be worth to someone now or in the future.

Back on topic, like you, I reckon your incident was probably caused by a faulty control and not a user error. It will be interesting to hear if the problem persists once your circuit board has been replaced.

[Colin62]

Back on topic, like you, I reckon your incident was probably caused by a faulty control and not a user error. It will be interesting to hear if the problem persists once your circuit board has been replaced.
I agree, but it’s not going to be easy to prove that all is OK.

[Fumbler]

Sorry, Fumbler, if you thought I was implying any incompetence on your part. Far from it!

And, apologies for taking the thread further off topic.

As Woodcrafts_UK had raised the roughing gouge matter in his post I felt I must comment on that and not just leaving it hanging there. My comments were in no way directed at you. I tend to make my comments broadly to anyone who is currently reading the forum or to those who might be reading it in the future. It's my small contribution to fellow woodturners, for what they may be worth to someone now or in the future.

Back on topic, like you, I reckon your incident was probably caused by a faulty control and not a user error. It will be interesting to hear if the problem persists once your circuit board has been replaced.

All good, no offence taken.

To a certain degree, a lot of people become complacent and cocksure, when things go right for such a long time, then whammo, it all goes pear shaped. Don't get me wrong, I am guilty of complacency at times, take my thumb incident for example. Had the saw for 10yrs, the previous weekend I had spent an hour straight repatatively cutting small lengths one after the other, some at odd angles. Then a quick 2 minute job put me out of action for 2 months.

i also agree bringing the what not to do's to people's attention is a good thing, I have learnt lots from lots of wonderful people on this site, and am very grateful for all the help, advice, pointers and parts that have been sent my way.

yes, I can't wait to get it back. As I have the conductors batons to finish.

i won't however be trying to reproduce what happened to see if it's fixed or will do it again. Chucks flying round the shed is never a good thing.

Richard

[Fumbler]

I agree, but it’s not going to be easy to prove that all is OK.

True, as I just mentioned in my reply to NeilS, I won't be replicating the situation to see if all is good.

[Colin62]

I just happened on the following comment about a Nova lathe which is relevant here

https://sawmillcreek.org/showthread.php?203017-Any-owner-of-Laguna-Revo-24-36-Lathe-Reviews-comments/page2&p=2299332#post2299332


I intended this for the Nova 2024 lathe.


I have had this for several months ......not ready for prime time.
Warning......when under slight stress, motor will suddenly lurch and double it's speed. The engineers are working on the problem. When coring a pine blank on slow speed (100rpm), it slowed for a moment, then raced up to 250 rpm, catching the tool and throwing the blank off the chuck. Same thing when using a roughing gouge at 250 rpm........a slight pause at a small catch the motor raced to 450rpm.
Nova was going to trade out motors but they found that the ones they were going to send did the same thing. I have been waiting several months for them to send me the swing away as well.

[Treecycle]

That tends to make a lot of sense. The fact that the tool caught on the blank, maybe it spun up to a high speed and with the faulty violent braking maybe it tried to almost instantly get back down to the original set speed and this is where the thread released.

[Colin62]

That tends to make a lot of sense. The fact that the tool caught on the blank, maybe it spun up to a high speed and with the faulty violent braking maybe it tried to almost instantly get back down to the original set speed and this is where the thread released.
In my mind it goes like this:


lathe spinning at (for example) 1000rpm
tool catches, dropping rpm to close to zero
control software sees speed is way down and aggressively ramps up speed
catch removed, and now the lathe is spinning at twice the speed it should
control software sees the speed is now way too high and applies the brake


If there’s an additional problem with a brake that is too aggressive, the chuck can easily spin off and we have an entirely plausible explanation that doesn’t rely on fairies :)

[Mobyturns]

If a lathe has EVS and is "underpowered" i.e. not enough grunt or the wrong belt setup is used, it is possible to stall the lathe motor with a "soft catch" (a progressive stalling rather than an abrupt stall/stop), reducing the spindle / blank RPM. When the turner reacts :oo: and withdraws the tool the EVS recovers and attempts to return to the selected / dialled speed and increases the spindle / blank RPM.

Most EVS setups are programmed to "ramp up" torque within limits to overcome stall conditions. So it is possible that the combined blank / chuck / insert that is loosely fitted to the lathe spindle may momentarily reach a temporary "overspeed" condition i.e. faster than the lathe spindle, and then becomes loose on the lathe spindle as the EVS recovers to the set speed. This can be a significant issue with larger bowl or platter projects that test the limits / power of mini / midi / cheap lathes and is alarmingly easy to do on any lathe running in "reverse".

The same occurs when a turner uses their hand as a brake on the hand wheel to abruptly slow the lathe spindle, the spindle slows however the inertia / momentum of the insert / chuck / blank overcomes the friction of either the spindle / insert or insert / chuck interface and "goes for a walk."





As I mentioned - one possible cause. Its alarming that lathes with these faults are not being discovered through product testing before reaching the market place.