Vacuum chucking- be aware of potential problems!

[Don Geiger]

Vacuum chucking- be aware!

Dear fellow woodturners:

I want to share an experience I had with vacuum chucking that was a near disaster. First of all, let me say that I have had a lot of experience with vacuum chucking. I been using vacuum on three different lathes in my shop for at least ten years with great success and very few problems.

I was just finishing up an order for three bowls and decided to use a vacuum chuck when finish turning the bottoms. As a safe practice, I routinely leave the live center against the bottom of the piece until I have removed as much waste stock as possible then start the vacuum pump and slide the tail stock away. As usual I checked the vacuum gauge first and observed -24" Hg. As soon as I removed the tail stock the piece flew off the lathe and landed about 10 feet away.

I put my finger over the inlet of the pipe that goes through the spindle and felt no vacuum or flow, but the gauge still registered -24" Hg. I pushed a long drill bit through the pipe and dislodged a mud dobber's nest and immediately attained vacuum and flow.

Amazingly, my piece wasnt damaged!

The first mistake I made is I pulled a through pipe off the shelf without checking it for blockage (I live in Florida). The second mistake I made was not turning the lathe off before removing the tail stock.

I hope some of you will benefit from my misadventure.


Don Geiger

[Steve Schlumpf]

Don - Thanks for sharing! Glad you weren't hurt and that your bowl survived!!

[Alan Trout]

Don,

I am glad you and your bowl are OK. I can attest to the problem with mud dobber's when I use to own my machine shop they would clog every hole in the building. It was a constant fight with them and I rarely won. Just one more thing to check to prevent a disaster. Thanks.

Alan

[Bernie Weishapl]

Don thanks for the info. Glad things turned out ok and you weren't hurt.

[Primvs Aebvtivs]

Glad you're both o.k., especially you, as wood grows on trees round here... and again, thanks for the warning!

[John Keeton]

Good post, Don! Glad you were not injured.

[Josh Bowman]

Darn, never thought of that, glad you're safe! Guess we need to "pre-op" test our vacuum systems before putting our faces over what we think it's holding. Great info, thanks.
Bet you messed up some dirt dobber's day though.

[Jim Burr]

Thanks for the tip Don!! First, glad you're ok...second...I'm getting a vacuum chuck in February so I'll be sure to make a note to "look at my patient"...not just the numbers!

[Robert McGowen]

I can certainly see that happening where I live. Thanks for the tip!

[James Combs]

As has been mentioned thanks for the tip. As an electronic technician(Fire Controlman - Maintenance and operation of missile and gun fire control systems) in the Navy it was always a good idea to verify power supplies before running any kind of test or fire control equipment. A vacuum is just that, a power supply. Verification should always be done at the point of use not just at the power supply itself.

[Mike Cruz]

Solid advice that I hope to learn from...thanks!

[Bob Bergstrom]

I had to put a reminder sign on my headstock to remind me to put the vacuum connection in the spindle before taking away the tailstock. I have lost two bowls because the vacuum reads about the same with or without the connection engaged in the spindle.:eek::eek:

[Nathan Hawkes]

Don, thanks for your experience, and your humility in sharing it with us! I've got a vacuum system that I never made an adapter for when I upgraded to a Powermatic, and have been thinking about cleaning the dust off of it.

The mud dauber story is absolutely believable! They get into everything! I recently replaced my parents expensive Baldwin door latch, which had stopped functioning--a mud dauber nest had been the abrasive that slowly over time wore down the lock mechanism to the point that a small 3/16" pin made of brass was worn to the point of not opening the latch. I hope it didn't do any damage to your vacuum pump.

[John Giem]

Darn, never thought of that, glad you're safe! Guess we need to "pre-op" test our vacuum systems before putting our faces over what we think it's holding. Great info, thanks.
Bet you messed up some dirt dobber's day though.

Every time I mount up my vacuum system to use it, the first thing I do is a "pre-op' test as you mentioned. I keed a small aluminum plate handy. 1. I place it on the chuck and apply vacuum and read the vacuum level with my hand off of the plate. 2. I close the isolation valve I have between the filter and the manifold. This isolates the chuck and close plumbing. I then watch the rate of fall of the vacuum pump. The rate of vacuum decrease give me a relative rate of leakage. I will repair seals, etc. if needed. When everything is OK, I can leave the aluminum plate hanging on the vacuum chuck and it will take over 5 minutes for it to fall off. Now when I put my turning on the chuck, I know within a small area, the turning, where the leakage is and a relative feel as to how bad it is. Often, I can fix any leakage and can proceed to the fun parts. This simple, fast easy pre-op test verifies that the whole vacuum system is operting as expected.

[Jim Underwood]

Had one a those daubers plug up a tire inflation chuck one summer. Couldn't figure out why the tire wouldn't take air. Dang things get into everything...

Glad you weren't hurt Don...

[Jon Lanier]

Mud Dauber's need homes too! However, you'd think a home like that would be a dizzying experience.

[Jon McElwain]

Those guys are good little potters! Glad everything turned out okay!

[Mike Cruz]

Jon, actually, I think the rod stays still...

[Harvey Ghesser]

Appreciate the head's up, Don. Glad you weren't hurt.