Chinese 7x Lathe Safety Issue

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Tin Falcon

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Guys what part of turn the machine OFF don't you understand. the speed control is not a power switch. This is operator error!! not a design flaw. :wall:
Tin
 

MuellerNick

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This is operator error!! not a design flaw.
That's like saying it is OK for a car's engine running in idle to suddenly rev up (with a automatic transmission in D, that would be fun).
It is both.


Nick
 

Tin Falcon

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Nick when one parks the car the AT lever is placed in park and the ignition switch is turned off. One does not leave the engine running and leave the car in drive and walk off. that is what cogs is doing.
Tin
 

MuellerNick

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One does not leave the engine running and leave the car in drive and walk off. that is what cogs is doing.
Hah! That even did my landlord with his Claas 7040 telescopic lift. Until we heard some strange noise outside. But we could not open my door because the Claas blocked it, breaking some pallets on its way. It very slowly starts to creep forward when the engine is running and not in neutral.

There are two mis-behavious you have to look at separately and that are BOTH unacceptable:
The lathe suddenly starting to rev up.
cogs doing a unsafe procedure (no need to keep on bashing him, he already learned his lesson).


Nick
 

Tin Falcon

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OK we agree that the lathe should have been shut off and it was not.

As far as the lathe starting on its own IMHO sounds like there was a bit of energy stored in the circuit board. the operator turned the motor enough so the brushes engaged, the energy was momentarily discharged . The pulse suddenly turned the spindle 1/4 turn.

I can not discount the possability there is a problem with the control board. these boards do have issues from time to time. there is no way to know if the board is defective without testing or examination. I therefore canot confirm or deny a problem with the circuit board.
Tin
 

starnovice

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Personally, I have to go with Tim on this one. I have one of these lathes and would not think of working around the chuck without turning the toggle switch off but I don't see the need to turn off the power switch for routine measurements and tool changes. I would power it down completely before I swapped out material or changed the chuck.

Mine is an older one that has the toggle switch from forward-neutral-reverse and does not have an E-Stop. Real easy to go from forward to reverse by mistake. :)

Having said that, I really don't need some company to protect me from myself if I use the machine as advertised.

Pat
 

kf2qd

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My 7x10 has a toggle switch and a potentiometer. When the speed pot is turned all the way down the spindle will still turn slowly. So I put the toggle switch in the moddle - OFF position when I want the spindle to stop.

My MiniMill has a potentiometer with a switch at the low speed position. Mine also has a toggle wswitch that I added. It has 2 positions - Forward and Reverse.

I would never assume that low speed on the minimill is STOP. Poweris still fully applied to the speed control and there is no guarrantee that the spindle won't turn. Low Speed IS NOT spindle stop. It is just Spindle LOW SPEED.

Just the same as low throttle on a car, truck or fork lift is not the same as engine off.

I would say this was a case of operator error, and to blame that on the manufacturer is the reason it is so expensive in this hobby... Someone else is to blame for my error. And to tell the truth, I really don't want to get to the point where someone else gets to make all the descoisions what SAFE means. Because then we will all be less safe because safety really depends on the operator using some common sense, and most of the so-called safety ideas are just trying to compensate for a total lack of common sense and without some sense from the operator there is no way anything can be made safe.
 

Jeff-in-PA

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Guys what part of turn the machine OFF don't you understand. the speed control is not a power switch. This is operator error!! not a design flaw. :wall:
Tin

I'm with Tin on this one. It's a machine, it doesn't care if flesh is in the way when it starts or impacts something. YOU are the safety device on the machine. It's up to you to be responsible for your own safety ( I do agree if it truly is an electronic problem, the manufacturer must address that ).

I've been a machinist for about 35 years and when it comes down to it, I am responsible for my own safety.
 

Cogsy

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Whoa, this has turned into quite a debate!

Just to clarify, I was at fault for touching the chuck when I did, no doubt, absolutely.

However, the machine has got some sort of fault with regards to the occasional speed fluctuations (and it's jumps of several hundred RPM) while running and I believe it should be covered by a warranty longer than 30 days. This thing cost me $750 + shipping and then tooling as well, so I would expect more than a couple months of hobby use.

The best thing to come out of this though, is I have now learned a valuable saftey lesson, and it didn't cost me any blood.
 

Tin Falcon

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1) Cogs thank you for sharing you lesson so others are not tempted to make the same procedural error.
2) We can now all see the importance of electrical isolation when adjusting maintaining machines two or thee points if needed. direction switch center position. power switch off . Unplug or power off power strip.
3) thanks to all for keeping this thread civil and above board, respectful and to the point.
4) You are right the machine should last for more than 30 days.
5) you are right there should not be major unprompted fluctuations in rpm.
6) I do hear and feel your frustration.
7) lets move forward and help solve the problem of unpredictable card function
8) Again I am glad you were not injured . I apologize if I added to the emotional pain . My intention was not to bash you only to point out the procedural error.

Tin
 

gus

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Gus worked for 7 years in a Chinese factory with dud ISO Certification. I told the boss and we had a hot argument but he finally admitted so as practically every Chinese factory does to bluff consumers.
For 4 years I worked with the QA and got quality up to mark. Three years down the line, old problems resurfaced. I gave up and left.
There are many factories in China with DUD ISOs.One good look at the framed up Certification will show. International ISO Certification Companies are mutually cross audited and accredited by other ISO Companies to be credible. This is not so in China. Quality is compromised.

A bad speed control board would have been picked and replaced by a Japanese Supplier and Corrective Actions taken followed by Preventive Actions plus a note of concern/apology to end user.Apparently not so in China.

Vee belt driven or gear driven lathes has on/off switch to isolate power supply and accidental self starting is prevented. Variable speed control lathes are best to rely on the on/off switch to isolate power supply and accidental self starting prevented. Same applies to electronic on/off switches.Took me a long time to accept soft starters. I would turn off and lock up isolators before working bare hands on starters.It is my life and I only have one life.
 
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mwilkes

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Thanks for that, Gus. I swear I'll never buy a Chinese machine. Cheap things come with a price tag, as they say. By buying a Chinese machine I'd be implicitly supporting poor working practice and exploiting people.

...plus I'd end up with a machine totally covered in packing grease....
 

hacklordsniper

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That is right, it should not happen.

It doesn't make much sense to switch off all switches on your lathe, unplug it and cut the mains to your house after calling the power plant to switch off the nuclear reactor. You just have to use a safe procedure that you can not accidentally turn the spindle on.


Nick
Im guessing this criticism was aimed at my post. My procedure lasts exactly 3 seconds, timed and proven on video just for this topic. This way i cut off power to the motor, engage turn direction to "neutral" and turn off the main switch witch completly cuts off power.

Is 3 seconds needed to turn off the machine worthy of my fingers, hand or something else? I think not. Accidents don't happen to "other" people, they can happen anytime to anyone.

I like to play it safe.

Here is a video showing what i think is a safe procedure before manipulating the work in lathe.

http://www.youtube.com/watch?v=wV0Z2f1R2oA&feature=youtu.be
 

skyline1

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There are many factories in China with DUD ISOs.One good look at the framed up Certification will show. International ISO Certification Companies are mutually cross audited and accredited by other ISO Companies to be credible. This is not so in China. Quality is compromised.

A bad speed control board would have been picked and replaced by a Japanese Supplier and Corrective Actions taken followed by Preventive Actions plus a note of concern/apology to end user.Apparently not so in China.
Gus you've been reading ISO9000 again, this is exactly how it should work and does in most parts of the world, but not it seems in China. Indeed much of their certification is bogus. It really screws up traceability (another ISO requirement). They do tend to pay lip service to Q.A. I have seen quite a few potentially lethal bits of Chinese "electronics", which carried all the certification required, but had never actually been tested, if they had they would have failed.

Regards Mark
 

gus

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Hi Mwilkes,

Bought a 7x Sieg in the US for a friend.He spent a week cleaning up the superduper,messy gunky rust preventive !!!!. Glad I bought on the net thru LMS.Lathe arrived in good condition and good quality as LMS has their own on-site QC. Items bought from LMS were up my expectation.

Spent s$2500 in 2004 to buy a Japanese Sakai 360 , 150mm swing over 360mm between centre.
Above is actually a watch maker's lathe. Had some regrets paying too much but now it worth every cent. Will take very light cuts and gives the precision and finishing. Tapping Fluid is very good for surface finish.

Came with conventional step pulley drive. A bit inconvenient to change speed so I left at 500 rpm.A robust on/off/forward/reverse switch ensures no accident self start. I still have my all fingers plus nails.

Bye now.Off to finish up the W.I.P. QCTPost now on my thread. This my second QCTP with cam lock.
 

Cogsy

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My intention was not to bash you only to point out the procedural error.
No worries, no offense taken.

I would like to explain my actions a little bit though, not to justify them, just so you know how I managed to make such a 'simple' error.

My speed control knob needs to be turned a reasonable distance before the motor starts to 'hum' then turn, so I assumed it was cutting the power when fully turned off. I assumed it worked somewhat like my variable speed hand drills - they have a switch for forward/reverse but not 'off'. I think nothing about grasping the chuck on one of them, as long as the speed control is at zero. (Now that I type it, I wonder if I'm wrong in that as well...)

Anyhow, that's how I arrived at my incorrect conclusion. With zero training, it was actually an easy assumption to arrive at. I'm going to really take a careful note of all the actions I do in my shed, just to make sure there's no other potential hazards that I'm exposing myself to without thinking about it.

One last item of interest - when it happened, it was far from the first time I've moved the chuck in exactly the same manner, it's just the first time I had an issue doing so. What this tells me is that just because you've gotten away with a hazardous operation in the past, doesn't mean you will always get away with it.

Stay safe everyone!
 

hacklordsniper

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Ken I

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As stated in earlier posts - never rely on a daisy chain of semiconductor devices always switch off.

Its possible your circuit is open circut (on the potentiometer) = flat out - then a momentary loss of contact on a cheap Chinese pot will cause the problem.

I wouldn't trust my safety to any pot - let alone a Chinese one.

I used to have a shop lecturer who would say "are you really going to trust your life to just one switch !" that's a thought that's been implanted and has served me well for several decades of work on industrial equipment without serious mishap.

Ken
 

gramps51

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After reading through this whole thread I learned two things: cogsy was lucky and his lathe is faulty. I had one of these things and because of lousy quality I sold it and bought a REAL lathe, a South Bend 9A. 50 years older and 150% better. My opinion only of course based on ownership and use.

Mike
 
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