My take on vacuum pump control.

[Alan Trout]

I have been putting together a vacuum system. I wanted a convenient, portable, compact, effective, safe, and easy to store setup. As well as something I could use on multiple lathes in case I need to take my system for a Demo etc.

This is what I came up with. I used high quality quick fittings that the elbows swivel and found some awesome quick disconnects that do not limit flow. Of course for safety I wanted to have a toggle switch in easy reach to control the pump. I placed a motor rated toggle switch in a aluminum box that the extension cord passes through. Of course there is a plug on one end and the receptacle on the other end that the pump plugs into. The manifold and fittings are affixed to the top of the box. The box has rare earth magnets on the bottom and the back so I can place the control panel any where I want or need. I tried a needle valve at first for the vacuum bleed but found I did not like it as well as a simple ball valve which is filtered. I used polyethylene tubing for the plumbing. It is dirt cheap works great and can be found at any home center in the country if needed. The filter is placed before the gauge to prevent trash from getting into it and the rest of the plumbing and pump.

The pump is a JB HVAC 6CFM vacuum pump that I pick up on craigslist for $125. It was in good condition. I changed the oil and I put a mist filter on the exhaust. What I have found as oil sump rotary vane pumps don't really mist unless there is no vacuum load on them and if they did the mist filter takes care of it. The entire system through the spindle pulls just a little shy of 29" and it pulls down instantly. I think this pump is going to serve my needs well and it is a quality pump that service parts are readily available.

Right now the rotary adapter is a Oneway. I first thought this would be a pain but it really is not and will work on both my Nova, and Woodfast lathes with just an adapter change. It seals incredibly well so I am very happy with that. I can also purchase other adapters as needed. However I do plan to make my own slide in adapter for the Nova but right now I just do to have to time to do the machining.

I am now in the process of making some chuck drums but may also buy on of Tom's at JT turning tools Precision Chuck hubs. However cash is always tight this time of year. Anyway here are a few pics. and thanks for looking. Alan

[Roger Chandler]

That is a nice and well engineered system Alan..........I think you did a super job. Maybe the addition of a portable box or stand that could be carried and set up easily would be good if you need to make it transportable to other locations.

[Mike Cruz]

Very compact and clean. I like it.

[Dave Mueller]

Alan,
Nice setup...What type of quick disconnects did you use, and where did you buy them.
Dave

[Scott Hackler]

*I don't know squat about vacuum chuck set ups...so...

I thought I read somewhere of a need for a reserve bottle or backup method to maintain the vacuum in the result of a power outage while the wood is spinning. Any thoughts on that?

[Jim Burr]

Sure am glad you thought of that, because I have no idea!!! Looks really cool!

[Eric Holmquist]

I would think that sizing a vacuum reservoir would depend on the goal.

If it is just to hold long enough for the lathe to slow down to the point where the piece will not go flying then the reservoir would most likely only need to be a cubic foot or two.

If the goal is to hold vacuum long enough to bring up a tailstock to keep the piece in place, then you would need something larger.

A better idea would probably be a UPS on the vacuum pump. My Gast is 1/3 HP which is around 250 watts, so a fairly small 500VA UPS should keep the pump running for several minutes. A UPS this size runs around $50. You could also have an LED light source running off the UPS as a safety factor so if turning at night, you are not faced with a scary spinning chunk of wood in pitch darkness.

[Alan Trout]

Thanks for the comments. Yes, there are some that do use vacuum reservoir. Power outages are pretty rare in this part of the country. but the idea of an APC is probably better in my opinion. I don't remember where I got the quick disconnects as it has been a while. I will see if I can find them again. These are commonly used in medical equipment.

Alan

[Baxter Smith]

Very neat setup Alan!

[John Giem]

Thanks for the comments. Yes, there are some that do use vacuum reservoir. Power outages are pretty rare in this part of the country. but the idea of an APC is probably better in my opinion. I don't remember where I got the quick disconnects as it has been a while. I will see if I can find them again. These are commonly used in medical equipment.

Alan

The usage of a vacuum resevoir has better justification than backup for a power outage.
1. If you place an isolation valve at the manifold seperating the pump and resevouir on one side and the vacuum chuck on the other, then opening the isolation valve can produce a sudden application of the vacuum and allow mounting of some difficult items that other wise would not mount. This is similiar to mounting a care tire on a wheel. The tire fits loosely around the wheel but does not have an air tight seal. When the Tech applies a sudden rush of compressed air, the tire pops into place sealing itself to the rim.
2. If the vacuum pump is located remotely from the lathe, placing a resevoir next to the lathe can help maintain vacuum at a constant level with changing conditgions.

[Tim Rinehart]

I've thought about making a reservoir out of a long section of schedule 40 PVC, which is the same material I use for my vacuum chucks. I think I've seen that to be a fairly common approach.
In the meantime...it's rare for me to ever vacuum chuck something without also applying a liberal amount of masking tape ... and for some objects that are just too porous to hold vacuum, I will bring up the piece to the vacuum chuck and just tape it down for removal of a tenon and forming the base without using any vacuum at all.
Nice rig Alan, well thought out and the pump has a good cfm spec that will help maintain vacuum under more porous conditions than what some lesser rated units will hold.
Most any vacuum pump out there has the pressure rating to hold a piece sufficiently, even down towards the mid-20"Hg mark...what many don't have is enough flow to account for system and workpiece leakage.

[Bernie Weishapl]

Alan that is a nice setup and very compact.

[John Giem]

I've thought about making a reservoir out of a long section of schedule 40 PVC, which is the same material I use for my vacuum chucks. I think I've seen that to be a fairly common approach.
In the meantime...it's rare for me to ever vacuum chuck something without also applying a liberal amount of masking tape ... and for some objects that are just too porous to hold vacuum, I will bring up the piece to the vacuum chuck and just tape it down for removal of a tenon and forming the base without using any vacuum at all.
Nice rig Alan, well thought out and the pump has a good cfm spec that will help maintain vacuum under more porous conditions than what some lesser rated units will hold.
Most any vacuum pump out there has the pressure rating to hold a piece sufficiently, even down towards the mid-20"Hg mark...what many don't have is enough flow to account for system and workpiece leakage.

A couple of things to consider here. 1. If you are using the vacuum resevour to float through a power glitch, you need to consider the type of pump you are using. Diaphram and piston pumps have valves in them that will prevent leakage when turned off and will allow you to hold a vacuum. Rotary vane pumps do not have these valves and when turned off, the back flow of air will cause a rapid loss of vacuum. 2. Regarding the CFM of your vacuum pump. It is important but not the most important. The pump needs to remove the air that leaks in from the mounted turning and from within the rest of the system. Any air leaked by the system reduces what is left to hold the turning on. The statement that "my pump has a high capacity and will overcome any leakage" is false. The plumbing and hardware between the vacuum chuck and the pump is the limiting factor for the amount of air that can be removed. I have tested and have data showing that a 5 CFM pump stand alone can only move aroung 2.5 CFM of air through the overall system. Every connector, hose, bend, etc. contributes to the flow limitations. 3. Leakage through the wood limiting vacuum levels is easy to fix. Saturday, I had a green apple bowl mounted on my vacuum chuck. (1/4" wall thickness) I centered the bowl on the chuck and turrned on the vacuum pump (3.5 CFM rating) and achieved a vacuum level of 5 in Hg. Too low for comfort.
This was enough to hold the bowl on while I fixed it. I moved the tailstock out of the way and grabed a roll of plastic food wrap from the kitchen. Ripped off enough to cover the complete outside ot the bowl. As I approached the bowl with the film, there was enough air flow to 'jerk' the film to the surface of the bowl. I covered the entire outside of the bowl, including the tenon to be removed, and smoothed it out. As I applied the film, we observedd the vacuum gauge rapidly moved from 5 in Hg to 18 in Hg. This was enough for me to proceed. I supported the bowl with the tailstock as long as possible, moved it out of the way and finished off the bottom. The vacuum level stayed around 18 in Hg until I was finished. Yes, the film did cover the area to be shaped but my bowl gouge did not notice and went ahead and did its job. Blue painters tape, I have enough confidence in what I am doing that I get good prformance without needing to use it.