Vacuum Chuck Question

[John Trax]

I have a Nova 1624 and am considering getting the vacuum chuck attachment. The Teknatool site seems to imply that this works with a shopvac rather than a vacuum pump. Has anyone used this with a shopvac? I have a 2hp dust collector and was wondering if just adding a port to the DC would work? Also, does the vacuum attachment block the hollow spindle so you cannot use the knock out rod?

[Jim Becker]

John, a vacuum chuck designed to work with a shop vac is not going to work with a dust collector. These two tools work on entirely different principles. Vacs move little air at very high static pressure. (SP is effectively the so-called "suction") Dust collectors work by moving very large volumes of air at low static pressure...there is very little "suction"...it's all moving air.

My recommendation would be to work up a vacuum chuck setup using a vacuum pump (surplus is what most folks use) so you can generate better vacuum and hold certain forms better. Vac powered setups tend to not hit the vacuum levels many of us prefer for heavy and/or large pieces.

[Gordon Seto]

I knew someone who used that, and according to him it worked. But he was using the Fein dust extractor. This is not a regular ShopVac; it has by-pass cooling for the motor. ShopVac needs air passing through to cool the motor. I find the ShopVac motor runs very warm if I don't clean up the filter very often.
The Fein price on Woodcraft catalog is as high as $460. You can get a real vacuum pump as Jim suggested at less than a quarter of that. And look up the excellent vacuum chucking tutorial here. This DIY version will be as good as any commercial unit.
If your handwheel is the same as the DVR, the adapter is even easier. The OD of a common 6004-2RS bearing fits the recess of the handwheel.
A home made gasket and the suction from the pump will hold the adapter in place, easy on and off, no lamp rod needed to pass through the head stock spindle. You can use the knock out bar when you are not using the vacuum.

[Tom Godley]

Gordon - Is that a thumb wheel bleed valve on your system?


I have been looking for one -- like them over a conventional valve.

Can not find one -- I wonder if it is goes by something else.



The vac does go/use the same hole as the rod -- but it is very easy to take on and off. Most regular shop vacs do use the air for cooling -- they are not designed to have the air volume reduced for any length of time.

[Gordon Seto]

Gordon - Is that a thumb wheel bleed valve on your system?

It is a Relief valve Grainger Item #5Z764
Better fine control than a regular shut off valve.

[Burt Alcantara]

John,
I didn't want to build my own so I bought the HoldFast. It works very well. Has a lot of suction and takes up very little space. However, you need a small compressor.

Burt

[Gordon Seto]

The Holdfast is not as convenient to use. You have to install and remove the hollow lamp rod through the headstock each time you use it. Use the vacuum chucks and make your own adapter. IMO

[Tom Godley]

Thanks Gordon -- That is just the ticket

[Burt Alcantara]

I leave the HoldFast on. Only time I've disconnected it was to sell the lathe and put it on the new one. Once it goes on, it stays there.
I should add that I use a chuck spur on the Talon.

Burt

[John Trax]

Thanks for all the information everyone!

I have a Grizzly dust collector system, not a Shopvac so not sure if that would work. The Teknatool site seems to imply that they prefer a "Shopvac" rather than a vacuum pump. Their reasoning is that the Shopvac provides a higher volume of air at lower pressure, so let it leak a little and it will still work. In fact it needs to leak to keep the motor cool. They say that vacuum pumps provide too little volume. Most folks here seem to prefer the vacuum pump though. Always more than one way to do something, I just thought since the dust collector is right there..............

[Bob Hamilton]

Hi, John:
I use the Teknatool adaptor with a shop vac on my DVR. It works well for the type of thing I use it for, which is removing the little nub where the tailstock was supporting the bowl and then sanding and finishing the bowl bottom. It doesn't develop anything like the "inches of mercury" numbers that a dedicated vacuum pump system can develop, but is also not nearly as susceptible to leakage problems. Like all vacuum systems the amount of gripping force is strongly dependent on the amount of surface area that the vacuum is acting on, so the smaller the diameter of the workpiece the more "feeble" the grip. A vacuum system that can pull 20"-25" of mercury could probably still hold on to a fairly small diameter workpiece but on my system the lower limit for diameter is in the area of ~4" and a piece that small would require a very light touch. Anything 6" or greater holds fine.

As Jim pointed out, a dust collector cannot substitute for a shop vac in this type of application. A centrifugal fan type blower moves a lot of air but if the supply of air is restricted the impeller just spins without doing anything. There is a bit of pressure differential which might be enough to collapse a plastic garbage can used as a pre-collector, but is not enough to develop any significant "grip". I once used vacuum clamping as a method to hold relatively small parts while pattern routing a profile on them and attempted to use my dust collector as the vacuum source. It did not hold the parts nearly tight enough. Simply switching from using the dust collector to using my shop vac on the same jig produced a much better grip on the parts and allowed me to complete the project.

I don't know how hard it is on the shop vac to use it for this purpose. I have never seen a shop vac that exhausts its air through the motor for cooling, but maybe some exist somewhere. Deadheading the vac does increase the load on the motor which could lead to overheating and premature failure. When I first started using the Teknatool system I was using a cheap shop vac that I had had for at least 15 years. I did not provide the bypass air flow that the instructions recommend. The vac worked well for almost a year of intermittent use and then the motor bushings started to squeal very loudly. Lubing the bushings quieted them down for a week or so but the noise came back. I bought a new, slightly more expensive shop vac and bored a bypass air hole as Teknatool recommends. The new vac is still going strong a bit more than a year later. I can't say whether the first vac failed because of the lack of a bypass air flow or simply from old age coupled with an increased work load, but since I did not really notice much of a difference in grip strength at the chuck after drilling the bypass hole I would say it is a good idea to follow the instructions.

Any vacuum system that draws through the headstock spindle is going to block access for using a knock-out bar. The adaptor will need to be removed in order to have that access. The Teknatool adaptor is simply retained inside the handwheel by a set screw so is very quick to put on or take off. I only have it on when I am actually using it for vacuum chucking.

Take care
Bob

[John Trax]

Thanks Bob! An excellent summary, I appreciate the time you took to explain all of that.

Best,

John

[Bill Mitchel]

I 2nd that! Thanks for the info.

Bill