Don't try this at home

[Waka]

Yesterday I was finishing off a small bowl, I mounted the Cole jaws on the lathe and put the bowl in so I could finish off the bottom.
Everything was going fine, but on slowing the lathe speed down to the lowest speed the chuck decided to come unscrewed from the lathe on its own. No damage was done to me although it cut through my turning smock. I guess instinct made me try and grab the chuck, silly thing to do.
On reflection I guess I didn't tighten the chuck properly on the lathe, it could have been a lot worse than it was so I consider myself very lucky.
Just thought I'd share this.

 

[SVB]

Glad you're ok.

This is why the VSD on the bigger lathes ramp down (so don't try and stop them just because you've pressed the stop button, they are still driving the slowdown ramp) so the drive does not stop quicker than the momentum of the load wants to resulting in it coming unscrewed as seems to have happened to you.

Some chucks / lathes have a retaining feature to guard against this, does yours (for future reference?)

S

 

[Waka]

Simon
Not sure my chucks do, I'm using the Axi k100 on the 1000 lathe. Never had this problem on my M900 but there again the 1000 is 1 hp as apposed to my other lathe which is ½ hp.
I think I'll need to take the speed down a lot slower in future, really don,t want to experience that again.

 

[SVB]

Remind me, is the 1000 elec variable speed, mech variable or change belts jobbie?

For approx 10 / 12" Cole jaws the max speed is normally 500-600 but as you're typically turning the foot (small diameter) you want as much of that as you can get - too slow and it feels more like power carving than turning!

S

 

[SVB]

Btw - a solution is possible if your chuck geometry will allow - is there some space to cross drill the chuck threaded boss so you could use a brass set screw to lock it in place when using Cole jaws or is this chuck flat across the rear with all the threaded section internal to the chuck?

 

[Waka]

Simon
The speed change is via mechanical via the drive belt, regarding the speed of the Cole jaws, I think I was up at 800 rpm, so I guess I was running a little to fast. Must pay more attention the next time I use them.
I don't have the facility to to put a grub screw on the back of the chuck unfortunately.

 

[Lons]

My Axi SK100 has 3 grubscrews to stop the chuck coming off. I never use them tbh as thought it was just if you reverse the rotation of the lathe. Must start locking in now!

 

[CHJ]

Simon
The speed change is via mechanical via the drive belt, regarding the speed of the Cole jaws, I think I was up at 800 rpm, so I guess I was running a little to fast. Must pay more attention the next time I use them.
I don't have the facility to to put a grub screw on the back of the chuck unfortunately.

I take it by that statement you have an older version of the chuck do not have an M5 Tap and tapping drill.

That's what I use as you can then use the same hex headed screws as used to attach the accessory jaws.

Is there not a member local to you that has the kit.

 

[Phil Pascoe]

My 28 - 40 will send the blank and faceplate or chuck into orbit if the blank is heavy and it's switched off without ramping it down.

 

[Waka]

My Axi SK100 has 3 grubscrews to stop the chuck coming off. I never use them tbh as thought it was just if you reverse the rotation of the lathe. Must start locking in now!

I've got 1 of the older type K100's and 4 of the newer type, I see the grub screws you mentioned but they hole doesn't appear to go right through to the thread, am I missing something?

 

[Waka]

Simon
The speed change is via mechanical via the drive belt, regarding the speed of the Cole jaws, I think I was up at 800 rpm, so I guess I was running a little to fast. Must pay more attention the next time I use them.
I don't have the facility to to put a grub screw on the back of the chuck unfortunately.

I take it by that statement you have an older version of the chuck do not have an M5 Tap and tapping drill.

That's what I use as you can then use the same hex headed screws as used to attach the accessory jaws.

Is there not a member local to you that has the kit.

Chas thanks for that, I will endeavour to get that sorted in the next day or two.

 

[Waka]

My 28 - 40 will send the blank and faceplate or chuck into orbit if the blank is heavy and it's switched off without ramping it down.

I guess I got a little complacent, notice to self, pay attention and do things properly.

 

[Lons]

My Axi SK100 has 3 grubscrews to stop the chuck coming off. I never use them tbh as thought it was just if you reverse the rotation of the lathe. Must start locking in now!

I've got 1 of the older type K100's and 4 of the newer type, I see the grub screws you mentioned but they hole doesn't appear to go right through to the thread, am I missing something?

Without going out to look Waka I don't think they locate on the thread of my Axi lathe but the recess behind the threads on the spindle. Could be completely wrong in that as I don't use it. Will in future though.

I'm not sure about grub screws biting into the thread though, wouldn't they get damaged?

 

[NazNomad]

My 28 - 40 will send the blank and faceplate or chuck into orbit if the blank is heavy and it's switched off without ramping it down.

Must be a Poolewood thing :-D

Mine did it once ... ONCE ... with a big blank mounted, the momentum of the blank unscrewed the chuck.

Now, if I have a big blank spinning, I slow it down first.

 

[Waka]

My Axi SK100 has 3 grubscrews to stop the chuck coming off. I never use them tbh as thought it was just if you reverse the rotation of the lathe. Must start locking in now!

I've got 1 of the older type K100's and 4 of the newer type, I see the grub screws you mentioned but they hole doesn't appear to go right through to the thread, am I missing something?

Without going out to look Waka I don't think they locate on the thread of my Axi lathe but the recess behind the threads on the spindle. Could be completely wrong in that as I don't use it. Will in future though.

I'm not sure about grub screws biting into the thread though, wouldn't they get damaged?

Lots

I've just been and had a look at my chucks, yes you are right there are 3 grub screws but they are not for securing the chuck to the lathe.
I had a word with Axi tech's and they said there is no facility to lock the chuck to the lathe, you can only do this on their 114. So I guess its back to in house modification.

 

[CHJ]

Yes you need a grub screw positioned so that it clamps in the recess behind the thread, (it's there initially to aid cutting the thread) If by any chance you have not clamped tight enough to stop any movement the mere fact that the screw is protruding into the groove fouls on the back off the thread as it tries to unwind. (as you will find if you don't release it sufficiently when changing chucks)

It's a problem with lathes that have had their invertors set to supply resistive breaking as well, the rapid deceleration can cause unlocked chucks to let go.

If I have anything that I think might encourage a chuck that isn't locked such as a tool catch when running reversed I try and make sure the tool rest or tailstock is close enough to stop it leaving the spindle, a damaged bit of turning is annoying but the smug feeling factor is a big pacifier.


On my old Poolwood I have actually drilled a small indent in the spindle grove behind the thread and by careful marking of Chucks and Back-plates managed to position all my locking screws to seat in the same indent.

 

[Waka]

Thanks Chas, very good information, I'll be looking into plan B next week.

 

[Lons]

Lots

I've just been and had a look at my chucks, yes you are right there are 3 grub screws but they are not for securing the chuck to the lathe.
I had a word with Axi tech's and they said there is no facility to lock the chuck to the lathe, you can only do this on their 114. So I guess its back to in house modification.

Been out catching trout today so only just had time to go look.

Has your chuck got the 33mm thread Waka because if so I don't know where the Axi guys get their info from.

My SK100 screws appear to locate behind the threads on my AT1416 vs, measured with a vernier and the chuck instructions state:

"As some of our variable speed lathes and others witha 33 x 3.5mm (T38) spindle thread have reversing facility, a reverse locking feature is incorporated on this thread option"

Bob

Edit:
Just lifted this off their website in the SK100 info
"N.B. Thread options M33 x 3.5mm (ref T38) and 1.1/4" x 8tpi (T23) have an extended body with provision for reverse locking."

 

[Waka]

Lots

I've just been and had a look at my chucks, yes you are right there are 3 grub screws but they are not for securing the chuck to the lathe.
I had a word with Axi tech's and they said there is no facility to lock the chuck to the lathe, you can only do this on their 114. So I guess its back to in house modification.

Been out catching trout today so only just had time to go look.

Has your chuck got the 33mm thread Waka because if so I don't know where the Axi guys get their info from.

My SK100 screws appear to locate behind the threads on my AT1416 vs, measured with a vernier and the chuck instructions state:

Lons Mine is the 1" x 8 tpi.

"As some of our variable speed lathes and others witha 33 x 3.5mm (T38) spindle thread have reversing facility, a reverse locking feature is incorporated on this thread option"

Bob

Edit:
Just lifted this off their website in the SK100 info
"N.B. Thread options M33 x 3.5mm (ref T38) and 1.1/4" x 8tpi (T23) have an extended body with provision for reverse locking."