Take That, Tenon Chuckers!

[snip]

As you can probabl;y guess, the faceplate for my vac-chuck is home-made too. A 19mm MDF (fine at lowish speeds) disk screwed to a 6" faceplate and faced with 5mm foam rubber. The foam itself is fairly porous, but with the high air-flow that hasn't proved to be a major concern.

I've even made minor catches severe enough to seperate the bowl from the faceplate and the high air-flow has sucked the bowl back down, albeit off-centre. Fortunately, apart from when first learning /how/ to use a vac-chuck, I haven't had any UFOs but I think that's probably because I've had to learn to use a light touch rather than any inherent advantages of the chuck.

For the record, I should say that I'm not advocating my system as being "as good as any other," just that there are some very cheap ways to make a start for someone with a little ingenuity. Anyone trying it should keep in mind that you only get what you pay for.

I am curious about drum chucks though, having never used one. I assume that they're like jam-fit chucks where it's best to make a custom one for each job, unless you've already made one that just happens to be the right size?

- Andy

Thank you, sir... this marriage is my 3rd try... hopefully, I've learned enough from the last 2 and won't screw this one up..

mac

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I also use 19mm MDF. Rather than mount it on a faceplate, I drill and tap a hole in the MDF to directly screw onto my spindle. I then true it up.

You can make a few different sizes of drum chucks. They don't have to be a tight fit at all just use the largest for the job since you will get more area and thus holding force.

I use ABS (black sewer pipe) straight connectors which come in several different diameters. You can also use a short length of the pipe as well. I make a recess with a parting tool (or whatever you like) such that the fitting sits in it with a snug fit. It only need be a 1/4" (6 mm) deep or so. I then epoxy the ABS fitting to the MDF. I then true up the open rim of the pipe and hot glue on some foam for a gasket and that is all there is to it. Note that the vacuum force will hold the pipe in the groove in the MDF so even if the epoxy fails the joint should still hold.

A drum chuck like this is even handy in non-vacuum applications say for truing a warped external tenon on a dried roughed bowl. Just put on the drum chuck. Place the bowl over it and bring up the tailstock and true the tenon. You could even finish the bowl bottom with this method if for some reason it can't be held under vacuum.

Billh

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Could be, but I don't think so. They needed lubrication just like any other cylinder/piston assembly. Seems that I do remember him changing oil periodically. Some racers also used these compressors for tires and air tools in the pits. They'd mount it on their tow truck either in place of the normal AC unit or build a separate mounting bracket to mount it below the block, sort of like some of the newer cars mount their water pumps. They used a regular automotive paper air filter to clean incoming air, so there was no lubricant in the airflow.

Ken

The modern refrigeration compressor as featured in everything from freezers to dehumidifiers is not the same.

I originally tried that but my spindle is threaded past the headstock casing, so unless I went to the extra effort of finding lock washers, the MDF'd spin itself in until the edge met the bottom of the casing (it's tapered back for accessibility) and promptly self-destruct.

Considering I make many tools/parts myself (having a tiny budget) I'm surprised I hadn't thought of that. For some reason I've been thinking of turning them out of scrap wood. Thanks for pointing me in the right direction.

That gives me a handle on another problem I have at the moment... I've recently finished turning the foot/tenon off an 8" English Yew bowl with cole-jaws and in my eagerness to marvel at my accomplishment was careless enough to clip the edge of the tool-rest which, of course, I hadn't removed. (I know, I know. You can't say anything I haven't already said to myself...)

The Yew is a truly lovely piece of birds-eye which had been sitting in a packing case for many years; it's almost impossible to replace nowadays. Certainly not on my budget.

Rechucking's out of the question and the foot-print is too small for the vac-chuck/faceplate. I assume it'd be feasible to mount the base of the bowl in a drum chuck, bring up the tailstock (padded) and trim the edge that way?

Just checking for feasibilty from someone who may know before I go trail-blazing for myself and discover something else I didn't expect.

- Andy

[---8 The modern refrigeration compressor as featured in everything from freezers

FWIW, I've asked a few local blokes about their experiences with vacuum chucking. Most of the blokes who tried it and gave it away as a bad joke had one thing in common... using a frig compressor. Of the ones with good experiences only a few used 'em.

There seems to be seperate two reasons why they failed to pass muster: burning out (I assume it's the lube problem you're talking about) and although they generate low pressure they're not high enough volume to handle the inevitable leakage at joints, faceplate or wood pores.

- Andy

Hi Andy

The real problem of burnout with these units is most likely the cooling that was there with the refrigerant and is no longer there, also no lubricant does not help but a drop of oil every couple of minutes would not be to hard to inject on the vacuum side, but the cooling problem is a hard one. Of course all the old freezer units had oil baths and those units last forever, they used a small electric motor and V-belts, I have made a couple portable compressor setups using a propane cylinder for storage tank, hooked up to a freezer compressor, they work great. Reversing this you could have a vacuum tank and vacuum pump, it should work imo. Some of those units are likely still to be had at cooling repair places for the asking or scrap metal prices.

Have fun and take care Leo Van Der Loo

Andy McArdle wrote:

Certainly worth trying and I don't see why it shouldn't work; if I had the problem it is what I'd do. Billh

I guess the best answer is to gird my loins and try, eh? I can't foresee any problems either, but only tomorrow will tell...

- Andy

For that tailstock bumper, turn a 1x? soft wood circle with tapered edge large enough to fit inside your bowl. Make sure you have a center mark, and use to center and contain the piece.

Even neater if you turn a tapered recess for your base on a faceplate with soft wood. Once it's centered, a tad of hot glue.

I made myself a drum-chuck and a 2"dia bumper curved to match the bottom of the bowl. Well... as closely as I could. Then discovered that sometime in the last week the vacuum hose had a nasty accident and, of course, my duct tape is nowhere to be found.

After a few moments of reflection I realised that a vacuum wasn't needed; the drum & tailstock seemed to be holding things quite nicely. I guess I was concentrating too much on trying what I've read to see what was as plain as my nose! [sigh]

Long story short, the bowl trimmed nicely although I did have a hairy moment when first introducing the tool a bit too quickly and it caught in the chip. The bowl shifted slightly off-centre but no damage was done and everything turned out for the best. No pun intended. So, I've added yet another useful method to my repertoire and all is well in my little world.

Thanks for the advice!

- Andy

circle. Gives you a bit better control over shifting.

Of course, If I had vacuum need and capability, I'd keep a spare roll of duck tape somewhere handy instead of stored with all those pencils I have down in the shop....

That's why I trounded the base of the bumper to fit, but it appears my logic was faulty.

Duct tape and pencils... the two banes of my life. I have boxes'n'boxes of both, yet all I have to do is put one down for a second and it disappears, along with the box it came out of!

I've even gone to the extent of drilling a whole through the end of my pencil and threading a string to hang around my neck. That didn't work either; the string kept snagging the odd corner and when I put it down for a second it /still/ disappeared. [sigh]

- Andy

Duct tape and pencils go o the same black hole that tape measures and one sock from each pair go..

mac

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