|Project by Matt||posted 03-03-2009 11:54 PM||8140 views||19 times favorited||11 comments|
I’m barely 1 day old on this site and don’t have any projects in a state that is ‘first pictures’ ready. I’m working on some cornices for the windows of my living room but, right now, they are simply boxes. For now, I thought I would post post a project I completed several months ago.
It all started a little more than a year ago. I bought my first lathe. I beautiful little Jet 1220. 1/3hp, 12 inch swing, and very well put together. I picked it up for $325.00. The price of these things has climbed quickly to more than $400.00 but that is another story.
I have happily turned pens and bowls all of this time. A few months ago, I got the opportunity to use a friend’s PM 3250. I was making a large-ish walnut bowl and was looking for a jam chuck or something to allow me to flip the bowl over and finish the foot. My friend says, ‘just use my vacuum chuck’. He proceeded to show it to me and go about setting it up. It made turning the foot on my bowl SOOOOO much easier, I knew there had to be a way to have this wonderful fixture on my Jet 1220. Here is my story.
This is the most expensive part of the project. It starts with the pump. You need a strong pump for this type of project. There are pre-built systems out there but be prepared to spend some money. Oneway sells a system and the pump alone costs nearly $400.00. I picked up the exact same pump, never run, for $100.00. I got it on Ebay and if you’re patient, you won’t spend more than $150.00. Here are a bunch Gast pumps (recommended). Make sure to get an oil-less model. Trust me.
My friend’s pump is a 220v, 1/4hp Gast unit that does a great job. My pump is the 120v version with 1/3 hp. It also moves approximately 4-5 CFM. This is important. For tight, dense, defect free wood, less CFM might prove adequate. When you get into the woods with a loose grain or even small holes, you’ll be glad you had the extra air.
Next, I turned (on the lathe) a fixture from walnut to hold a 1/4 inch male fitting and a double sealed bearing. I also turned the threads off of a brass male fitting to connect my air hose to.
This next part is important. The little black O-ring you see, gave me an extra 2 inches of vacuum. Don’t skip this part.
Here is a picture of it installed in my handwheel. There really isn’t any installation. If it fits, it fits. The vacuum actually holds it in place when you have a bowl or something sealing the chuck on the other side. Keep your tailstock in place until you get the vacuum running. Using the tailstock also helps you center up your bowl prior to turning on the lathe.
Now this is what we want to see. 20 inches of vacuum! I’m actually pulling close to 22-23 on a nice piece of wood. The key is making sure your system is as ‘leak proof’ as possible because you will lose some through the piece you’re working on. It’s a matter of physics. Wood is porous.
Here is a small chuck I made with a 1X8 spindle tap (just screw it onto the headstock), and some closed cell foam you find in the craft section of Wal-Mart.
Last but not least. This is a globe I was turning for a Christmas ornament. There’s not really enough surface area in this example to hold that piece in place for actually cutting with a chisel but it holds just fine for sanding and finishing. Larger vacuum chucks will hold with enough force to implode your workpiece if you get thin enough.
I have included a 3d model of the vacuum chuck adapter after a few questions about it. It’s not to scale. You will have to modify the size and shape after measuring your handwheel. It’s simply to show how the parts fit together. I hope it helps.
From left to right:
1. Air hose fitting.
2. Double rubber sealed searing
3. Wooden body
4. Headstock spindle fitting
5. Rubber O-ring.
Well, that’s it for now. Here are some additional things to keep in mind.
1. Seal up the adapter you created to hold your bearing, hose fittings, and O-rings. When in doubt, make it air tight!
2. Mind the thickness of your piece. To thin, too much vacuum, or too much surface area = Kablooey!
3. Seal the piece and let it dry one time before you start applying finishes while in the vacuum chuck. It will pull that stuff right through the headstock and into your filter (you do have an in-line filter right?) or worse, your pump.