This really hurt! Don't ever try it.

[BenPeake]

I just thought I'd put this up so no one else tries this (not that anyone would )

I've had my lathe for about two years now, and I've pretty much taught myself how to use it. Unfortunately, when you teach yourself, you're bound to make some mistakes which could very simply be avoided. This was one of them.

I buy my stock in 3 or 4m lengths (9 - 12 feet) and being the way I am I like to get maximum use from it. I figured that to do this, rather than pre-cutting a piece of bar for a part and wasting the extra bit which I would need to hold it in the chuck, I would just put the whole length in the chuck! This meant there was up to 3m hanging out the back of the spindle. I got away with this for months without ever realizing it could be a problem. Then one day, the inevitable happened - the overhang started spinning off-centre at max speed and before I even realized what was happening it had bent itself under the massive centrifugal load and whacked me in the stomach, under my jaw and right beneath my eye. I was wearing safety goggles, But I doubt they would have stopped the hurricane of metal if it had decided upon my eye! I just about cried it was so painful and in hindsight it was the most stupid idea ever! (and I would be reminded of how stupid it was for the next couple of weeks while the wound on my face healed - you can bet I felt like a twit telling that story)

Well I've never done that again - now I never let the bar I'm working with extend beyond the spindle by any considerable distance. It also cemented the importance of saftey around machinery in my mind, as I very well could've damaged my eye or perhaps even lost sight in it - definately not worth saving an inch of bar!

Ben

 

[SAM in LA]

Ben,

Thanks for sharing. It sounds like you barely missed a trip to Heaven.

SAM

 

[zeeprogrammer]

Glad you weren't seriously hurt Ben.

I was wondering about this the other day. I had a longish rod chucked up...it was long enough to reach the rear of the head stock but didn't stick out. 1/4" or 5/16" round.

I wondered if the length that was in the head stock was wobbling enough to cause the part I was working on to wobble ever so slightly. (With the chuck being a fulcrum.) Curious if anyone has thoughts on this.

I think production people use some kind of, what would you call it, 'follower' to hold long length of stock.

 

[Deanofid]

That's really scary, Ben. What a relief to hear that you're not horribly injured.
When I say it's scary, it's because I know. Not wanting you to feel alone in what you're sharing,
I did it once too.

Was cutting 1/4" allthread into short studs for a job, and even had a carrier on the other side of the
spindle. On one cut, I forgot to move the carrier closer to the back of the spindle bore, and the piece
was free on that end. It whupped the tar out of the work bench, leaving a witness telling the boss
what I had done. No one hurt, but that little piece of allthread turned into something like a 2' wide
Waring blender blade.

Don't feel like a twit for telling on yourself. Will save someone from similar agony one day.

Dean

 

[Tin Falcon]

I had a similar situation took a gouge out of my prized antique 1940s vintage oak machinist tool box. That was emotionally painful.
Tin

 

[SKIPRAT]

Hi Ben

I too am glad you were not seriously hurt by the incident. and i trust you have learned a lesson from it there is no way you can extend the material beyond the headstock unless it is adequately supported .A long time ago i spent quite a bit of time operating a Ward 3a capstan bar lathe and used full length bar stock the material was loaded into a bar guide and fed forward as needed by the large handwheel left of the headstock the chuck was a lever operated collet and opened and closed as required apologies if i am off topic enjoy machining above all work safely.

Cheers Paul

 

[rake60]

Ben I am happy that you are still here to tell that story.

As a rule of thumb, 1/3 of the material being turned should be supported by the chuck.
If that is not possible a steady rest of center should be used.

We do not often talk about what is sticking out of the back of the spindle.
It can become just as much of a hazard.

My mini mill is mounted to the bench in an awkward position. The front crank handle almost
rubs the bench. In that position I can mount a steady rest to the mill table where it can
support any long stock protruding through the back of my lathes spindle.

I wish I could say I did that on purpose.
I didn't! I messed up when I drilled the mounting holes for the mini mill.
It just HAPPENED to line up with the lathe spindle, but it has been a beneficial error
more than once!

Rick

 

[mu38&Bg#]

I use 3 foot bar in my lathe. This means about half of it can stick out the back. To avoid whipping I've made a spindle spider to support stock on the back side of the spindle.

Bob Warfield has this on his site about 6 images down in the link below. Mine is based on this idea.

http://www.cnccookbook.com/CCBlogNov2008.htm

 

[shred]

My lathe has a 'spider' on the back of the spindle-- just 4 tapped holes at 90' to each other-- the idea being you put 4 screws through the holes and tighten against the long part. Kind of a pain to center though.

 

[Maryak]

Guys,

A spider is a help for SHORT protrusions, but for long overhangs a proper support/supports must be used and they in turn must be firmly bolted to the floor, wall, ceiling otherwise they too will take off with the off centre bar and you have several items ready to do you harm.

If it is necessary to have this set up it is also much safer if you run the lathe slowly.

Ben, I am sorry you were injured, but I'm glad you are still in one piece and can see from both eyes. You were bloody lucky and I would go and buy a lottery ticket if I were you. :

Thanks for sharing this with the rest of us. :bow: :bow:

Best Regards
Bob

 

[New_Guy]

I just thought I'd put this up so no one else tries this (not that anyone would )

I've had my lathe for about two years now, and I've pretty much taught myself how to use it. Unfortunately, when you teach yourself, you're bound to make some mistakes which could very simply be avoided. This was one of them.

I buy my stock in 3 or 4m lengths (9 - 12 feet) and being the way I am I like to get maximum use from it. I figured that to do this, rather than pre-cutting a piece of bar for a part and wasting the extra bit which I would need to hold it in the chuck, I would just put the whole length in the chuck! This meant there was up to 3m hanging out the back of the spindle. I got away with this for months without ever realizing it could be a problem. Then one day, the inevitable happened - the overhang started spinning off-centre at max speed and before I even realized what was happening it had bent itself under the massive centrifugal load and whacked me in the stomach, under my jaw and right beneath my eye. I was wearing safety goggles, But I doubt they would have stopped the hurricane of metal if it had decided upon my eye! I just about cried it was so painful and in hindsight it was the most stupid idea ever! (and I would be reminded of how stupid it was for the next couple of weeks while the wound on my face healed - you can bet I felt like a twit telling that story)

Well I've never done that again - now I never let the bar I'm working with extend beyond the spindle by any considerable distance. It also cemented the importance of saftey around machinery in my mind, as I very well could've damaged my eye or perhaps even lost sight in it - definately not worth saving an inch of bar!

Ben

Mazak CNC lathes have a warning sign on the back end of the spindles its of a stick man bending over and a bar belting him in the ass!!! you are still luck you could so easily have been killed and im sure people have!!! its not very good practice to hang a bar out the back of a spindle but it can be done at work we machined shafts 6m with threaded ends hanging out the back of the spindle so far they had to cut holes in 2 walls another thing i have seen is the bar end supported in a sling on the crane if you need to do this again use slow speeds and support the end with some sort of steady (not a human!!) but then again it maybe best to get out the old hack saw or buy a abrasive chop saw

 

[johnthomp]

i did something similar in school many moons ago i was threading some 6 mm bar on a large boxford lathe and only needed 8 inches of the stuff but had nothing to cut the bar coz the bloody hand tool cabinet was locked and without seeing any problem with it i put a 5 foot length of 6 mm bar in the lathe and started her up after it got up to speed it went offcentre fast and fukkin furious while protrudeing about 4 foot out of the back of the headstock i stood back in fear to see this giant weedwhacker i had spawned smash the classroom window remove 5 shelves destroy 8 polystyrene ceiling tiles shatter a striplight and gouge a workbench top like a knife through butter
thank god there was an emergency stop footbar running the full length of the machine but the head of the technology depot wasnt happy when i told him about my little mishap i then spent 3 weeks in detention cleaning all the machinery with a rag full of meths
ill never forget that day and the way it happened so fast i literally left my guts in the seat of my pants

 

[BobWarfield]

Guys,

A spider is a help for SHORT protrusions, but for long overhangs a proper support/supports must be used and they in turn must be firmly bolted to the floor, wall, ceiling otherwise they too will take off with the off centre bar and you have several items ready to do you harm.

+10 on that!

The thing that's ugly about the free swinging bar, is that if it starts to bend, it is then flung around at a longer radius, which increases the force causing it to bend, so it bends further. It's a vicious cycle.

I have seen fabricated supports that add a steady rest sort of thing to help hold the bar. But, I like the idea of having the bar not only supported in that way, but fully enclosed in a stationary pipe that is securely fastened down.

Once you're set up to do it safely, you sure can make a mess of parts in a hurry with a good bar feeder.

Cheers,

BW