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Vacuum Question for John Lucas

Bill Boehme

Bill Boehme

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John,

I would be interested in getting a copy of your plans for building your own vacuum adapter. I had planned to buy the EZ Vacuum adapter, but it is rather expensive and looks like something similar could be made for a lot less money.

Bill
 
Rotary adapter drawing

Here is the drawing that John Lucas sent to me. I have made some modifications to the design since getting started this evening. I have marked some of my changes in red. I am using a 6201ZZ bearing which has a hole slightly smaller than the OD of a 1/4 NPT nipple so I chucked the nipple in a Jacobs chuck (it needs to have a 5/8" capacity) and used a square end scraper to turn the diameter on one end of a 2 inch 1/4 NPT nipple down to the bottom of the threads approximately and then pressed the bearing onto that end of the nipple. I opted for an elbow connection to reduce the flailing of the vacuum hose and the other end of the elbow has a male quick-disconnect air-hose fitting installed. The 1/8 IP all-thread lamp pipe has 27 threads per inch and can be threaded into a hole threaded with a 1/8 NPT tap. I plan to take a few pictures as I proceed and will post them if anyone is interested.


Vacuum adapter drawing


Bill
 
ZZ Bearing

Hey this is the first time I get to share knowledge rather than ask a question. I do not know about this first hand, but I am in the process of constructing my own vacuum chuck, and I have the aid of a machine shop and several machinists where I work. When I was asking those guys some questions about bearings, fittings, etc.; they told me not to get a bearing with the initials "ZZ". According to them, a bearing with "ZZ" in the product code means it's double sealed with metal (not shielded, that's something else). They said to get a bearing with "C3" in the product code. That means it's double sealed with plastic/rubber and is truely sealed. According to them, a "ZZ" bearing can still have the grease sucked out of it by the vacuum (they should know, we use a lot of vacuum equipment where I work). Maybe our vacuums won't pull enough to suck out the grease, but I thought I'd share this info anyway.
 
Thanks Jason, that is one of the questions that I was not able to get a good answer to until now. My plan had been to use a 1/16 thick plumbing washer on the outside (high pressure side) of the bearing to reduce leakage and also to construct some sort of close fit labrynth to minimize the pressure differiential across the bearing itself. I will keep that information in my mind, but for now I will use the bearing that I have since I can't "unpress" it from its tight fit without breaking something. I am attaching a picture of the first part to be completed: Click here to see first part of swivel fitting.

Bill
 
I recently set up a vacuum chuck and used this bearing,

General Bearing Corporation
Double Seal
21808-88

I can pull over 25" Hg. I made the mistake of using a shielded bearing first and could not pull over 10" Hg it leaked so bad.
 
Last edited:
Jason,

Thanks for the information. I gave my ZZ bearing a leak test and it was terrible the way that it leaked, so it was back to the hardware store for a different bearing. I found a 6200 sized double rubber sealed bearing with a C3 rating. While I was at it, I also got a larger double rubber sealed bearing with a 5/8" ID and 1 3/8" OD. It was a good fit for a 3/8 NPT nipple after turning one end down slightly. I mounted the 6200 bearing on a 1/8 NPT nipple, so now I have two sealed bearings ready to be used in a rotary adapter. The total price for all of the brass fittings, all-thread lamp rod, and bearings is less than $20 which is very cheap compared to the commercially available units.

I began wondering what to do with the useless leaky ZZ bearing mounted on a 2" X 1/4 NPT nipple until I found that a tapered point from a live center fits perfectly into the end of the brass nipple so now I have a ZZ Top.

Bill
 
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