[MichaelHenry]

If anybody here has used the Tormach vacuum chuck I'd like to get some feedback on it. It has an 8x8" footprint and is designed to be held in a 5" or 6" vise between the jaws in the outside positions. At $279, it is a lot cheaper than the full size vacuum plate that Tormach sells or the ones that Pierson sells.

I'm think to use it to flycut some nominal 1/4" CPVC bar stock down to a specific thickness. The material bends and shifts too much to get consistent results when held by the 5" vise jaws, so the vacuum chuck seems like a good solution.

[soofle616]

Haven't used the tormach one specifically but my pierson is awesome. They're not really all that complex a thing. It's the vacuum pump that matters more imo. I would think rolling your own would be fairly straightforward. Only reason I went with the pierson was because I had several different parts to make and I liked the idea of the replaceable top plates the pierson offers. At the time I was not terribly good at precision locating features so I didn't feel I had the ability to make it myself. Today, I would probably buy a pump and make my own chuck.

[starvinmarvin]

They are too simple to make and having one made specifically for what you need matters too much so I have always made my own. Use foamed cord stock for your seal, dovetailed grooves in your fixtures, and you are good to go. I use vacuum to hold my pallets for production milling as well as holding parts when appropriate. My favorite vacuum source is a venturi unit from Vaccon that uses .5 cfm @ 60psi making 27". As long as you have good seals it works perfectly. If you go with an electric pump get a rotary vane, you DO NOT want a oil bath high vacuum pump that will boil whatever coolant/water is in your separator tank.

[MichaelHenry]

Thanks for the replies. For $279, I decided that the Tormach chuck was worth the cost and ordered one as there isn't time to make my own. It should be here tomorrow.

I also ordered a Robinair 15500 rotary vane vacuum pump (2-stage, 5 cfm) to supply it with vacuum. I don't have enough compressed air to drive a venturi device but maybe later. I won't have a separator tank but the current job will be run dry so hopefully that's not necessary. For the future, what do folks use for a separator tank? In the lab we used to use a heavy wall, glass Erlenmeyer flask but glass in a metal shop sounds like a bad idea.

[kstrauss]

My favorite vacuum source is a venturi unit from Vaccon that uses .5 cfm @ 60psi making 27".

Which model Vaccon unit are you using? Source for the cord?

[starvinmarvin]

That pump is exactly what you do not want if you are going to ever use coolant. Rotary vanes can't create enough vacuum to boil water and they will live through ingesting coolant with just a solvent rinse, no teardown necessary.

I will get both the Vaccon unit and cord source tomorrow, I am supposed to be programing tomorrow's parts right now.

[Mooser]

That pump is exactly what you do not want if you are going to ever use coolant. Rotary vanes can't create enough vacuum to boil water and they will live through ingesting coolant with just a solvent rinse, no teardown necessary.

I will get both the Vaccon unit and cord source tomorrow, I am supposed to be programing tomorrow's parts right now.

Sorry but which pump are you referring to here?
M

[starvinmarvin]

I used to get my foamed cord stock from Allied Seals but their website is gone so here is what I came up after a search that looks like it will work. I use 3/32" cord stock almost exclusively for all my parts or fixtures with Harvey O-ring dovetail cutters. The foamed cord stock compresses so easily you can use .01"-.015" compression even with thin plastic parts. With solid cord stock .004" compression can be a problem with 1/8" thick plastic parts as it takes so much pressure to compress the cord. I tried finding my pump on Vaccon's website but couldn't find it, the closest is the 60H but it uses .8cfm of air and I swear mine uses .4-.5 depending on 80 or 60psi incoming. Here is the link to the page. I first tried their bodies but had a major problem with it so I now roll my own.

Here are some photos of my vacuum set up. The first photo shows the brass venturi vacuum generator with a body I made for it with an integrated valve. The middle photo shows my pump bolted directly to a pallet receiver with the clear tube being my "silencer". This doesn't work too well if there is coolant involved as if it ingests coolant it will lose significant vacuum. The last photo is how I use it for most applications since I use coolant for almost all machining, and a trap is absolutely required. The threaded nipple and adapter block can be removed once I make a filter head that the pump can bolt to directly. I am real picky about my tools and setups, but I use this for months a year so having it perform better will save my hours over a year. It takes about 2-3 seconds to draw the vacuum to lower than 25"s when used as a pallet lock. You can see a t-nut on the bottom of the bracket so I can mount it to my mills table running a 1/4" tube between the fixture and pump. The black push-to-connect elbow is for the 1/8" compressed air feed. The regulator to control feed air pressure is outside of the machine.
Attachment 475796Attachment 475798Attachment 475800


The dual stage pump is what I am saying NOT to use if you are going to use coolant. It will draw down the vacuum enough to easily boil water, which you do not want in your oil. Plus you are supposed to change the oil out daily with those pumps. You should also filter the air going into them. I do have one so I know all about them from first hand experience. A rotary vane is better for work holding as they are far less picky about ingesting stuff, just have the correct solvent on hand to clean it out, by running it through the pump, when you suck some coolant into it. The rotary vanes are nice in that you can have a big flat plate with a port in the middle for your vacuum. Then just make custom seals out of rubber sheet for your onesie towsie parts. I have done this to machine 2"x7" aluminum parts. I had to face them down to 5mm from 1/4" and then profile the outside to a funky shape. Use small endmills and be real gentle and it worked just fine. The funky shape and tight thickness tolerance made soft jaws a bad option.

[kstrauss]

Thanks! Have you any thoughts on the cheap venturi vacuum units available from Amazon (https://www.amazon.com/CV-15HS-Gener...dp/B07N88R55Y/ for example)?

[shred]

Thanks! Have you any thoughts on the cheap venturi vacuum units available from Amazon (https://www.amazon.com/CV-15HS-Gener...dp/B07N88R55Y/ for example)?

I get brand-name surplus venturi pumps off eBay. Those have data sheets online and there's not much to them to go bad. The industrial scrapper-liquidators have piles of them, although if you want a particular model sometimes you have to setup a search for it.

They are made in a vast array of sizes and vacuums and air usage, so choose carefully if you have a small compressor.

[kstrauss]

Understood. My compressor can supply perhaps 20 cfm at 60 psi so the only problems should be the annoying noise from the compressor and the venturi.

[Milling_man]

The dual stage pump is what I am saying NOT to use if you are going to use coolant. It will draw down the vacuum enough to easily boil water, which you do not want in your oil. Plus you are supposed to change the oil out daily with those pumps. You should also filter the air going into them. I do have one so I know all about them from first hand experience.

Our situation is exactly the opposite - a two-stage vacuum pump works great when cutting plastic (POM), using a coolant. We used to change the oil about once a week of continuous operation, but the reason was not coolant, but rust from the vacuum receiver After replacing the receiver with a stainless one (I bought a stainless tank from a storage water heater), the problem disappeared, and the oil lasts at least a month of work. Our scheme is as follows: a vacuum table - a transparent flask from a water filter for the primary coolant separation - a water filter for separating small chips - a receiver - a 5 micron water filter from rust in the receiver (I think we will remove it now) - vacuum pump.

[scott216]

I used to get my foamed cord stock from Allied Seals but their website is gone so here is what I came up after a search that looks like it will work. I use 3/32" cord stock almost exclusively for all my parts or fixtures with Harvey O-ring dovetail cutters.

Can you provide links or part numbers for the dovetail cutter and 3/32 cord?

[starvinmarvin]

Milling_man, obviously your seals leak enough not to boil the coolant. What do you get from your 2 stage pump that a rotary vane wouldn't supply? I don't think the extra 2-3"s of vacuum would make a difference. Rotary vanes have more airflow, less maintenance, don't cost as much and are much more tolerant of ingesting stuff. They are a bit noisier though.

scott216, I got medium density neoprene sponge .093" diameter cord stock, which is in the link I provided in post 8. In hindsight I should have got the .07" cord stock as the dovetail cutters are for normal size cord stock, which .093" is an oddball. I faked it using a 1/16" size dovetail cutter and cut the bottom of the dovetail slots lower with a .078" ball mill to make more room for the larger cord stock. I probably should have used Bunna-N instead but my original use was with water instead of oil soaked metalworking coolant. I also got .125" cord stock but have never used it. The smaller cord stock is better for tight corners and .015" of compression is fine with the foamed stuff. Those custom designed dovetail cutters are well worth the $$ for making the slots to hold the cord since they have nice radiused edges at the top of the slot. I use the ones that will leave a plunge hole, they are not necked down to avoid it, and don't glue my cords together. I just leave them long enough to push together. Gluing them together is a hassle and the glue joint doesn't compress as well so it probably leaks more than just pushing the ends together.

Here are some other links that may be of interest.

Air-Vac Store: AVR SIngle Stage Models:

https://www.2linc.com/vacuum-pumps/

[shred]

Can you provide links or part numbers for the dovetail cutter and 3/32 cord?

Pierson Workholding has gasket and cutters. Some cool pallets and useful videos for the vacuum machining novice as well. https://store.piersonworkholding.com...sket_c_11.html

McMaster carries Vacuum Gasket but it's unusually difficult to find there unless you search by that term, and they don't have many sizes.

Mitee-bite also has gasket but the Byzantine sales system they use discourages me from them unless it's available nowhere else.

[MichaelHenry]

Tormach supplies 1/8" neoprene cord with the 8x8 vacuum chuck (their larger vacuum fixture plate apparently uses a much larger size). I ordered this 1/8" neoprene cord from McMaster:

https://www.mcmaster.com/vacuum-gaskets/

but haven't tried it yet until I can adapt the SAE fittings on the Robinair pump purchased to NPT fittings. Looks like an auto part store might have adapters and I'll find out if that's so tomorrow.

@starvinmarvin - I'm aware that coolant can damage a vacuum pump, but CPVC can be cut dry so I'm not expecting any problems there.

[shred]

Tormach supplies 1/8" neoprene cord with the 8x8 vacuum chuck (their larger vacuum fixture plate apparently uses a much larger size). I ordered this 1/8" neoprene cord from McMaster:

https://www.mcmaster.com/vacuum-gaskets/

but haven't tried it yet until I can adapt the SAE fittings on the Robinair pump purchased to NPT fittings. Looks like an auto part store might have adapters and I'll find out if that's so tomorrow.

Make sure it's really SAE threads. Lots of industrial vacuum gear uses "G" threads which are based off BSPP-- British Standard Parallel Pipe, using a sealing washer & probably Whitworth threads. .

As usual McMaster has the fittings, as does Amazon. That was a fun one to discover, although copious quantities of thread tape can make other threads work in a pinch.

[starvinmarvin]

Here are the fittings I got from McMaster-Carr for my Robinair pump. Page Link Part 50635K374. I use the intended HVAC hose to connect the pump to the receiver tank. I haven't removed the fittings from the pump itself to know what those threads are but you may get NPT to 45 degree Flared Fittings for Copper and Brass Tubing as a backup.

[MichaelHenry]

@starvinmarvin - thanks for the link to the MMC fittings. I was looking for adapters that have a female SAE on one end and NPT on the other. Near as I can tell, MMC doesn't offer any female SAE flared fittings.

I was able to find what I wanted at hoseandfittings.com. They had what I wanted in brass and shipped out my order within a day with delivery today. Looks like the flared female sides of the fitting might need an O-ring for sealing so I ordered what look like the right dash numbers from MMC and they will be here tomorrow. Or maybe male and female flares are meant to seal face to face with bare metal contact. Anybody here know?

For anyone else considering the 8x8 Tormach vacuum chuck, the little rubber discs that come with it don't seem to seal the top plate all that well - I get about 27-1/2 in Hg whereas a blank plate gets to 29 in Hg or so. Eventually I will try laser cutting some disks from 1/8" thick polyethylene foam, probably at a slightly larger ID to see if those ill seal any better. For the most, though, I will probably customise blank plates using the soft 1/8" neoprene cord stock that McMaster-Carr sells for vacuum fixture plates.