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Jaakko Fagerlund
02-25-2012, 05:47 PM
I'm making a small rig for a friend. This drilling rig has a small plate that is hollowed out from the bottom and a small 2-stage vacuum pump is used to attach the plate on the side of a safe. I'm milling a groove on the underside of the plate for a seal that goes around the plate.

The only thing I'm thinking if a regular large O-ring works or what type of easily available seal I should use. Usually the sides of a safe are quite flat and smooth, as most are a steel plate that has been powder coated.

The pump is able to be always on, so a small leak doesn't matter.

mike4
02-25-2012, 06:01 PM
I'm making a small rig for a friend. This drilling rig has a small plate that is hollowed out from the bottom and a small 2-stage vacuum pump is used to attach the plate on the side of a safe. I'm milling a groove on the underside of the plate for a seal that goes around the plate.

The only thing I'm thinking if a regular large O-ring works or what type of easily available seal I should use. Usually the sides of a safe are quite flat and smooth, as most are a steel plate that has been powder coated.

The pump is able to be always on, so a small leak doesn't matter.

I would use two Silicon O rings spaced about 80 mm or more apart with the vacuum between them that way you woud get a better seal and therefore a better grip to the surface.
If you have ever seem large sheets of glass being carried by a crane in factories etc they use a similar setup .
Silicon O rings tend to be a bit softer than conventional ones and its easier to get a seal.
I have used a magnetic drill to assisst the local locksmith remove a failed combo lock from an ATM , it took two of us 4hours and six tungsten tipped bits to get the job completed .Many have anti drilling systems in the doors.
Michael

darryl
02-25-2012, 06:06 PM
I know you can buy o-ring material in a roll- you just cut the length you need and tuck it into a groove, making the ends meet. I can imagine that with care in cutting the ends, you wouldn't need to use a sealant.

I would probably look for a soft compound, as that would have more give- possibly making it easier to get a seal all around.

Of course a lot depends on the size of the plate and the width of the sealing ring you could use. Maybe there's an off-the-shelf o-ring that would fit.

Offhand, it doesn't seem like a problem unless the surfaces are so non-flat that you can't make it touch all around without a lot of force to begin with. Once the vacuum is on, the larger the diameter the more the parts will be sucked together.

There are also different seal types that are used in sealing windows in double and triple pane assemblies. You could ask at a glass shop- chances are this stuff could be made to fit. Usually it has a lip which would have a large range over which it touches, compared to an o-ring. A .1 inch diameter o-ring for instance might have a squish range of 20 thou (just guessing) whereas this window seal might work over a larger range.

jnissen
02-25-2012, 09:05 PM
http://vacmaster.aryvacmaster.com/vacmaster/pdf/VP210C_Manual.pdf

#2 in the list is a double lip continuous silicone seal. My wife uses this machine and the seal is by far the best I have seen or experienced in any vacuum machine. It would be worth a call to them and see if they can sell you one. I believe they have smaller versions as well.

BTW - Not all safes have smooth finish. Many go with the pebble look and that could be difficult to seal with a standard o-ring.

Toolguy
02-25-2012, 09:12 PM
For a vacuum chuck for a mill (we always made our own) I've always used rubber surgical tubing. You cut a groove in the shape you want a little smaller and shallower than the tubing then make a chamfer around the top on both sides. Stuff the tube in the slot and trim it to length, 1/8 to 1/16 long to make the ends seal.

1-800miner
02-25-2012, 09:15 PM
Consider the rubber seal from a refrigerator door.

duckman
02-25-2012, 09:40 PM
When I was doing service work at GE I watched them drilling holes in the concrete floor using a vacuum base drill , got nosy when they were done and went and talked to the operator, basically the base was a flat plate with some grooves in the bottom and a sponge rubber gasket glued around the edge, he told me if they didn't have good seal they'd just pour some water around the edge for a better seal, amazing how powerful the suction was, even on rough concrete floor.

gary hart
02-25-2012, 10:04 PM
If you have a gasket supply place close by, ask about closed cell gasket material. They can cut gasket from sheet stock.

Use strips of it for a vacuum table on mini mill and works good in that application.

Google closed cell foam gasket

ckelloug
02-25-2012, 11:58 PM
I think a large size, large diameter soft o-ring would be a good choice. Liberally slathering the thing in Dow Corning High Vacuum Grease probably wouldn't hurt. For vacuum, you probably need an o-ring that doesn't have a break. Gluing silicone o-ring to make it vacuum tight is not easy.

Mike Burdick
02-26-2012, 12:11 AM
Permatex makes an array of sealants readily available at most automotive stores here in the USA. Maybe they sell it, or something similar, in your country...


http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Form-A-Gasket_No_1_Sealant.htm

knedvecki
02-26-2012, 12:50 AM
When I ran an 6 ft. X 6 ft. X 6 ft. electron beam welder that would pull down a vacuum to 4 Torr using both a roughing and a diffusion pump the door seal was just bulk 1/4 inch diameter o-ring seal with the ends super glued together using a cutting / alignment jig. Worked good!

danlb
02-26-2012, 02:30 AM
I only recall reading about mag base drills for drilling safes. That makes sense when the safe is made of steel, and most are. I would think the vacuum would not be as strong as a good magnet.

Commercial quality safes almost always have anti drilling provisions as well as anti torch mixtures inside the walls. They have 'relockers' that jamb the lock if you drill the door. Some of the tech is really clever.

They also have very specific areas that are NOT protected so that a safeman can drill it with minimal damage when it is called for. Reading through the trade magazines you find things like 'For this model, drill a 3/8 hole from the left side, 4 inches from the top through the wall and side of the door.' Bore scopes are often used to see inside the mechanism.

Dan

Jaakko Fagerlund
02-26-2012, 06:49 AM
Thank you everyone for the suggestions! :) One of talked about concrete drilling rig, so I called a friend of mine who does HVAC work and I knew he has a concrete drilling rig and went to see it. It indeed was a vacuum type rig, with a hollow base plate and spongy like rubber seal around it, glued down to a small groove. And he said the same thing: If it doesn't want to hold properly, just pour some water around it.

So I'll probably test this at first with a glue on door/window seal or similar that I can easily purchase from a hardware store and if that doesn't work out, I'll go to a sealant supplier asking for some silicone rubber or the like.

What comes to magnetic drill rigs, well, they are fine when you have a solid steel surface to attach to, but the problem is that many safes have thin plate on them so the magnet won't stick to it very well and some have stainless exterior which is austenitic and the magnet won't attach to it. This is the reason why a vacuum plate is better.

And yes, I happen to know "too much" of safes and what their walls and locks contain, have drilled/torched/cut/picked quite many of them open :)

EDIT: Would someone know where to get small vacuum meters? Like a pressure gauge but for vacuum. NPT or BSP threaded will work. Tried searching eBay, but couldn't find what I was looking for, maybe missing the right search terms.

knedvecki
02-26-2012, 08:42 AM
Automotive vacuum gauge?

Jaakko Fagerlund
02-26-2012, 11:15 AM
Automotive vacuum gauge?
Thanks, found what I needed but not for automotive use :) Seems that there was an ID 10 T error involved in typing in eBay :rolleyes:

Jaakko Fagerlund
02-26-2012, 04:18 PM
Damn, found a veneer stuff supplier from USA I think, but they only deliver to certain countries and Finland is not among them. The stuff is called vacuum gasket tape, it is 3/8" wide and a roll of 82 feet costs about 20 dollars plus shipping.