Lathe Chuck disasters

[JorgensenSteam]

I took a machine tool technology class years ago in college, and even though the teacher repeatedly told the class on the first day "DON'T LEAVE THE CHUCK KEY IN THE LATHE CHUCK", sure enough, a few minutes into the first class, CLANK-BANG!, here comes a lathe chuck flying across the room and banging into the wall.

 

[steamer]

Well, that's all part of learning, especially if its on your own.

The good news is if your OK ( and thats a good thing) after the first time you do it, it usually scares the &#&^) out of you and your not likely to repeat it. :big:


SouthBend has a great book on running a lathe that is very helpful. I have a very similar one from Hercus that is very good.

Welcome to the Forum...and that's OK...We're all learning.

Dave

 

[stevehuckss396]

I have been trying to learn how to machine, and am learning at the school of hard knocks.

You are not alone! I'm sure everybody here has made a bad move or 2. I had a whopper that resulted in a $750usd repair bill for my Bridgeport. And Steamer, you are correct, I wont be doing that again. Good news is the mill runs great again and I avoided injury. The 750 hurt alot less than injury!!

Keep at it and don't forget to have fun.

 

[Tin Falcon]

Pat:
Yes the school of hard knocks indeed. I am a professionally trained machinist.Courtesy of good old uncle Sam. I spent the summer of '97 At the USAF Machining welding school at Aberdeen PG MD. And I worked in a couple of civilian shops.

But I still find myself doing most of the things on your list on occasion. And a few more as well. I think my worst wake up call was having too much material sticking out of the head stock . It bet whipped around a took a big gouge out of my pre-WWII vintage oak machinist chest. I was thankful I did not get hurt but 65 year old furniture does not heal.

Here are a few rule of thumb pointers that may help.
Keep stick out to a minimum
3-5 diameter on work more than that support with a center or rest.
10 D out of the tail stock
2 -3 tool stick out for HSS
Always check and double check your set up
turn the chuck by hand and check for interference
make sure the tool reaches where it needs to before you start cutting.

Tin Falcon

 

[black85vette]

turn the chuck by hand and check for interference

Yep. Saved my bacon more than a few times. Thm:

 

[Royal Viking]

Remember the chuck key! I've gotten into the habbit of removing it as soon as I am done using it. ;D

 

[steamer]

Yep. Saved my bacon more than a few times. Thm:

OOOOOOH yeah.....MINE TOO!

Dave

 

[T70MkIII]

A good thing about the C2 Mini lathe chuck key is that it has an "ejector spring" around the key.

Might be a useful safety modification to think about.

 

[chillybilly]

You cant beat hitting the chuck with the tool .that is scary !!!!

Best thing is accept the odd stack up ,the skill being avoiding any of the bits hitting you ....

Be safe and enjoy

 

[TroyO]

*knock on wood* I haven't launched a chuck key yet, BUT.... I did once spin it up with a chuck jaw not engaged. It throws those pretty good too.

I thought it was engaged in the scroll. Now I pull on each one after changing anything so I know it is, LOL.

 

[SeanG]

As a learner - level 1

I've broken (forgotten) two of the rules so far.

not so long back I carefully rotated the chuck by hand - nothing fouled. So I took a cut, leadscrew powering the slide - wanged the topslide into the chuck - Mr Muppet here only checked everything was clear at the the start of the cut - not at the end as well. :rant:

And this week, for the first time ever - yep - left the key in the chuck. Luckily the speed was slow, so it tapped me on the chest and tinkled to the floor. I was furious with myself for making such a stoopid error though. Unplugged the lathe there and then as punishment and went to bed early with no supper.

I like the spring idea I was thinking of fixing the key to the plug end of the power cord so I could never use the key when the power is up - by preference though, I'd like to learn to be less forgetful th_rulze

 

[mklotz]

Maybe it's just me but the idea of a spring-loaded chuck key sounds like the most enormous PIA I can imagine - especially so when working with the four jaw.

To my way of thinking a far more practical approach is to make the key a series element in the lathe power supply circuit. Take a piece of stock and bore it out to a close sliding fit on the key and machine a bell mouth so it's easy to insert the key. Fit a microswitch to the bottom of this device such that the switch is closed when the key is inserted. Wire the switch in series with the lathe power supply such that the key must be in position in order for the lathe to run. Mount the key holder in a convenient location on or near the lathe.

 

[johnthomp]

they did that idea with the switch in my old highschool and it worked a treat to the point the chuck keys were removed during times when the teachers and other staff went on lunch so nobody could fool around with the machines unatended sort of an immobilisor
regards john

 

[zeeprogrammer]

My (mini-lathe) chuck key is spring-loaded and like Marv suggests it's a PIA. It pops out and drops quite easily.

My second grumble is that I have yet to develop the habit of putting the key in the same place and am always looking for it. I was thinking of making a key holder for it but Marv's suggestion to make it integral to the power system is attractive.

Hm...I have more trouble with the mill. At least twice I've turned on power with the spindle lock engaged. That sounds like a pretty good opportunity too.

 

[TroyO]

I considered the chuck key holster/interlock a while ago and never did it on mine.

Some thoughts on it, though:
A small switch may not be able to carry the current to use it on the “Power side” of the circuit. (IE small enough that gravity on the chuck key would activate it.)

You could use the switch to run a relay, OR.. Maybe a meaty reed switch (See edit) mounted on the side (So that pushing the bar in would turn it on) could work... you’d probably have to push the chuck key in against some resistance rather than just “dropping it” but in practice it shouldn’t make a difference.

There’s also an issue with the serial interlock part of it. If, for some reason the power switch was on already the lathe would start up when you slid the chuck key home... not sure I’d want that.

If your machine has a magnetic switch (Designed so the machine will NOT turn back on after a power outage even if the switch is left “ON”) you could use the energizer (Keep alive) side of the circuit, which is low power and even a small switch would be OK on. The problem with that (at least on mine.. HF 8x14) is that even if an interlock is “Open” when I press the “ON” switch the lathe still comes on while I physically apply pressure. In my case I have an interlock on the DC motor overheat switch, and on a “HEY DUMMY! Don’t reverse the motor while it’s running!” interlock for the reverse switch so using that circuit works OK for my purposes.

Just some food for thought. Still a good idea in general... just takes some thinking to figure out the best way.

{Edit} I looked it up, apparently wthe type i meant was "Snap action" not reed switch... http://www.mouser.com/ProductDetail...=sGAEpiMZZMumBvQ1hY/fBa0rKDzVGhP3yQ6dl/W4a7o=

 

[mklotz]

My suggestion is that you stop bumping and start turning the chuck by hand to test your setup.

If a chuck jaw is going to hit an extended compound, doing it under power may fracture the compound no matter how fast you get things turned off.

One thing I've done on my lathe is wire a magnet-mounted microswitch to a small battery-powered alarm. When I'm doing something where an inadvertent overshoot would cause a disaster, I place the switch so that it triggers the alarm far enough in advance to give me time to take corrective action.

 

[cidrontmg]

Hi Pat,
quote "I have three keys, and keep them in a holder on the wall adjacent to the lathe. One is for the 4-jaw, one for the 3-jaw, and one for something else (I forget what)."
The third one would be the second key for the 4 jaw. You really should have (and use) 2 keys to adjust a 4 jaw. There are many, many threads here and in Madmodder showing why, and how.
Thm:

 

[cidrontmg]

Hi Pat,
You might read this
http://www.schsm.com/html/centering_work_in_the_four_jaw.html
By Marv Klotz, shows you why another key for the 4 jaw is a very good idea.
Thm: