That pisses me off!!

[Gary Beasley]

I had a nice large poplar bowl nearly finished, trying out the Osmo Finish on, and had it mounted in my big mcpherson chuck nibbling off the tenon with the corner of my square carbide scraper. It was half gone then without any warning the bowl was slung across the room and smashed. I was using the lightest touch I could manage and still disaster struck. This isnt the first time this has happened, Ive tried every tool I can think of but it still fights me when I use one of these chucks.
I really need to built a donut chuck!

 

[Bill Boehme]

Time to get a vacuum chuck.

 

[Gary Beasley]

Sound like a good alterative. How easy is it to center the work on the chuck?

 

[hockenbery]

View attachment 25150
I had a nice large poplar bowl nearly finished, trying out the Osmo Finish on, and had it mounted in my big mcpherson chuck nibbling off the tenon with the corner of my square carbide scraper. It was half gone then without any warning the bowl was slung across the room and smashed. I was using the lightest touch I could manage and still disaster struck. This isnt the first time this has happened, Ive tried every tool I can think of but it still fights me when I use one of these chucks.
I really need to built a donut chuck!

Ouch!

I prefer removing the tenon with a spindle gouge. However it is not foolproof and I have broken tenons easily when I let the gouge get pulled under the tenon. This will happen in an instant if I have the tool rest low and touch the gouge tip to the tenon.
So I get the tool rest up so I cut on the top of tenon. This greatly reduces/eliminates the chance of the gouge getting pulled under the tenon.

Removing the tenon with a scraper I would set the tool rest below center and keep the tool handle up so I am working below center with lots of clearance between the wood and the scraper bevel. With the lower tool rest positions and the handle up from level I avoid letting the endgrain climb onto the tool or letting the bevel of the scraper contact the wood both of which are big time catches.

 

[hockenbery]

I use a jamb chuck for most bowls to remove the tenon.

Fast forward to 35:50 to see how I turn the tenon off a finished bowl.
I use a bowl gouge and spindle gouge.
It takes about 3 minutes.

View: http://www.youtube.com/watch?v=sCZWsHB4vlM

 

[Gary Beasley]

I had the bowl jammed in with the tailstock until it got too close to work so the support had to come off. So a jam chuck wouldnt have helped here. I need a positive lock on whatever surface I use. I have several vacuum pumps so Im going to look into that option. Whats the general experience using vacuum on large bowls?

 

[hockenbery]

Vacuum works great on large bowls and platters.
Too much vacuum will crack them so you need to use a bleeder valve to reduce the vacuum.
You don’t need much vacuum to hold for turning off the bottom 10 mg will work for most bowls
20+ mg will crack a lot of 1/4” bowls.

A big catch will pull a bowl off the vacuum chuck too.

 

[William Rogers]

I use my vacuum chuck all the time. An advantage is being able to sand after removing the tenon. My 4; chuck is homemade PVC that is secured to hard maple and the hard maple is threaded for my spindle. I sealed the maple. I check the vacuum gage and use masking tape if the wood is porous wanting a minimum os 22 in hg.

 

[john lucas]

I much prefer a bevel rubbing tool to clean up the foot and remove the tenon. The reason is the bevel is pushing against the wood and pushing the bowl into the chuck. I don't normally recommend pushing on the bevel. I think you should glide or be very light on the bevel, but for these cuts I apply a little pressure toward the chuck and as little forward pressure as I can and still get a good cut.
I'm not familiar with the McPherson chuck. I did an article for our club many years ago on diffferent ways to reverse turn a bowl.
https://docs.wixstatic.com/ugd/268d5d_b027e5c9973d47d09b1ca74422a38e4b.pdf

For more good tips and tricks just to our club website.
https://www.cumberlandwoodturners.com/tips-and-projects

 

[Bill Boehme]

Big bowls usually means thicker bowls, but measure to be sure that the center isn't too thin to use vacuum. As Al indicated you don't need especially high vacuum. A larger diameter vacuum chuck or jam chuck reduces the likelihood of slipping or squirming around which can be a reason for getting a catch whether you are using a vacuum chuck or a jam chuck. Slipping is often caused by too much force which is often the result of using a dull tool. Avoid using thick spongy material as a vacuum seal or jam chuck padding. It's OK to leave a nub in the center and then grind and sand to get rid of it. Nobody will know or care how you removed the nub.

 

[Dwight R Rutherford]

Here is a handy chart that I use.

 

[Gary Beasley]

I definitely wasnt using much force on it. I’ve also tried bevel cuts with some success but the grip of the chuck, I dont know why I keep thinking mcpherson but its longworth, is tenuous at best. Its good for centering but barely grips. The catch probably was caused by the bowl slipping loose but it happened so fast I got no warning it was trying to move.
I put in an order for a oneway kit for my DVR. I have the pump already. We’ll see what I can cobble together when the parts arrive. Do you put an inline dust filter on the pump to keep out sanding dust? One of my pumps is a gast that already has a filter unit but its attached to a contact printing frame, it may have to be sacrificed!

 

[Richard Coers]

Don't take the tailstock away. When you get to the point when you can't turn any further, take it off the lathe, cut the last bit off with a hand saw, and carve and sand it smooth. Sometimes simple is the solution.

 

[Bill Boehme]

Absolutely use a filter and put it close to the rotary coupler so that you don't get dust in the vacuum gauge or the rest of the tubing or especially not in the pump. It can be the same type of filter as you use on an air compressor. While you'e at it, get a needle valve and a vacuum gauge.

 

[BobCoates]

View attachment 25150
I had a nice large poplar bowl nearly finished, trying out the Osmo Finish on, and had it mounted in my big mcpherson chuck nibbling off the tenon with the corner of my square carbide scraper. It was half gone then without any warning the bowl was slung across the room and smashed. I was using the lightest touch I could manage and still disaster struck. This isnt the first time this has happened, Ive tried every tool I can think of but it still fights me when I use one of these chucks.
I really need to built a donut chuck!

At least you found the pieces. I am still missing some big sections. Perhaps it time to clean shop.

 

[Zach LaPerriere]

I'm with others that would suggest not using a scraper. There's a potential to dig in, so a bevel rubbing cut with a gouge is best. For thin bowls or poorly held bowls, I prefer sheer cuts on the foot because they put less stress on everything.

 

[robo hippy]

Hmm, so a McPhearson chuck is a variation of the Longworth chuck, which is a variation of the Cole jaws.... At least I think so. I don't use any of them. One friend who uses the Cole jaws uses the blue painter's tape to help make sure the bowl doesn't launch. I did try it once or twice. I do keep the rpm way down when I did that, in the 500 or so range, but I don't have a read out, so guessing, but way slower than turning speeds. As a scraper psycho, I would not suggest using a scraper for that cut. Also a very dainty touch is needed, not standard turning cuts for stock removal, more like 1/16 inch shavings. As a martial arts instructor (Wing Chung) says, 'Appetizer first, main course second.' but with this type of cutting there is no main course, you really have to nibble away gently. With the bevel rubbing cut approach, you still have to follow 'the bevel should rub the wood, but the wood should not know it' rule, so the bevel rub is not really pushing the bowl down into the chuck. That would create the wrong type of pressure. You can use a very light finger push on the wood, or your hand as a steady rest pushing in towards the chuck. If your hand is getting warm, you are pushing too hard, and/or your rpm is too high. This is just one more reason why I use a recess as my finished bottom for my utilitarian pieces. One less step, and less risk also. Maybe some day I might get a vacuum chuck...

robo hippy

 

[Charlie Knighton]

if u want to use scrapper.....1 inch wide scrapper with round nose for the final cuts and depth of bottom......I also agree to cutting the nib and sanding

 

[Dean Center]

Absolutely use a filter and put it close to the rotary coupler so that you don't get dust in the vacuum gauge or the rest of the tubing or especially not in the pump. It can be the same type of filter as you use on an air compressor. While you'e at it, get a needle valve and a vacuum gauge.

Somehow I stumbled onto using an automotive air (oops. Bill caught it) fuel line filter. These are the plastic ones with visible paper filters so you can see how much junk you've collected and know when to change to a new one. They come with different sized male ends to connect to your tubing, cost just a few bucks and are available everywhere.

 

[Bill Boehme]

Sounds like a fuel line filter. Some people use them and they seem to work fine for vacuum chucking.

 

[Gary Beasley]

The gast pump filter is a large felt cylinder in a glass jar that also works to muffle the noise. These same filters are used in print shop equipment to handle the paper dust and offset powder and are pretty effective and easy to clean.

 

[Bill Boehme]

The gast pump filter is a large felt cylinder in a glass jar that also works to muffle the noise. These same filters are used in print shop equipment to handle the paper dust and offset powder and are pretty effective and easy to clean.

Is it an oiled type rotary vane pump?

 

[Emiliano Achaval]

View attachment 25150
I had a nice large poplar bowl nearly finished, trying out the Osmo Finish on, and had it mounted in my big mcpherson chuck nibbling off the tenon with the corner of my square carbide scraper. It was half gone then without any warning the bowl was slung across the room and smashed. I was using the lightest touch I could manage and still disaster struck. This isnt the first time this has happened, Ive tried every tool I can think of but it still fights me when I use one of these chucks.
I really need to built a donut chuck!

I have never worked Poplar, but if I scrape even the bottom of a Koa bowl or lots of other Hawaiian woods, I would get a horrible surface that no amount of sanding would fix. Like John Lucas I much prefer a bevel rubbing tool. My tool of choice is a 1/4 Thompson detail spindle gouge. I use a vacuum chuck whenever possible, if not a jamb chuck.... Whenever possible I try to leave the tailstock mark on the bottom, making it very easy to mount perfectly centered... You will love a vacuum chuck!

 

[Emiliano Achaval]

Sounds like a fuel line filter. Some people use them and they seem to work fine for vacuum chucking.

Glad to hear they work, I have been using one, purchased it at Napa auto parts... So far, so good...

 

[Gary Beasley]

Is it an oiled type rotary vane pump?

No, its a dry graphite vane pump, pretty common on graphic arts equipment back then.

 

[Bill Boehme]

That's good because the dry vane type are essentially maintenance free. Personally, I think that the felt cylinder filter isn't sufficient for really fine dust ... and there will be lots of dust coming through the wood. You can figure that dust has to be really fine to pass from the exterior of a bowl to the inside when you are sanding. That is something that made me say WOW the first time that I vacuum chucked a bowl.

 

[Jerry Maske]

And if anyone cares, I've used the expansion method and NEVER had a problem. Plus, it allows for a creative foot I can do a lot with. Most chucks will expand. And I've made some pretty big bowls that way. But if a tenon is what you insist on, then you'll have to find your own way. Expansion is too easy and, I think, looks pretty neat.

 

[hockenbery]

If you need more space under your live center.
I have a set of these inserts from Bruce Campbell. The fit in the ONEWAY and powermatic live centers

http://www.artisansworkbench.com/Product info/Extension Points/extension_points.htm

 

[hockenbery]

And if anyone cares, I've used the expansion method and NEVER had a problem. Plus, it allows for a creative foot I can do a lot with. Most chucks will expand. And I've made some pretty big bowls that way. But if a tenon is what you insist on, then you'll have to find your own way. Expansion is too easy and, I think, looks pretty neat.

The expansion works well with some designs. It is also totally incompatible with most of the designs I like.

I almost always use a tenon because
I find it much easier to true a tenon than a recess on a dry warped bowl
I can leave a center point in the tenon for recentering since the tenon gets turned away
A tenon wastes a lot less wood on natural edge bowls than a recess when I want a small foot or no foot
I don’t like having to compromise my design to accommodate a 3” hole in the bottom
I can turn features in my tenon I can’t turn anything in the hole space.
Sometimes there will be 2” for a tenon and not 4” inches for the recess and a 1/2 of wood outside it..

I do on occasion use a recess where it fits my design better than a tenon. Most often this will be platters turned from dry wood. Here the recess on some designs saves wood especially if I want a 4-5” foot for a functional platter.

 

[Bill Boehme]

If you need more space under your live center.
I have a set of these inserts from Bruce Campbell. The fit in the ONEWAY and powermatic live centers

http://www.artisansworkbench.com/Product info/Extension Points/extension_points.htm

The MultiStar live center includes an assortment of tips that enable you to get closer when finishing the borrom. The Robust live center has a reversible tip that is pointed on one end and flat on the other.

 

[hockenbery]

The MultiStar live center includes an assortment of tips that enable you to get closer when finishing the borrom. The Robust live center has a reversible tip that is pointed on one end and flat on the other.

These centers stick out about an inch so you have lots of working room for gouges etc.
I don’t think the others protrude very far.
The Campbell centers might fit the Robust. Bruce Campbell would know.

 

[Bill Boehme]

The center pin on the Robust is straight and held in the desired place with a setscrew so the protrusion is adjustable.

 

[hockenbery]

The center pin on the Robust is straight and held in the desired place with a setscrew so the protrusion is adjustable.

If it can stick out an inch it may do the trick.


Bruce’s little points one has a flat with a tiny point to help,center but when they ge that small centering can’t get off much.keeps slipping t

 

[Gary Beasley]

I got my Oneway vacuum adaptor today, nice solid piece of equipment. Unfortunatly the insert that came with it had damaged threads right out of the box. I called Packard Woodworking where I ordered it from and they are bending over backwards to fix the situation for me. Thats some good folks there.
Now the dilemma of the chuck itself, Oneways version is pretty darn expensive but you get what you pay for, well built. Hold Fast has the same thing at less than half that but made from plastic. Then theres the homemade option Im looking at described in some of the threads here. I havent found a complete build description yet but Im sure its there. Decisions decisions!
Next item is I dragged the vacuum frame out of the corner and salvaged the control panel and pump off of it, just took a screwdriver and small wrench and the box was off complete with gauge, bleed valve and power switch. That saves a lot of tinkering!

 

[Bill Boehme]

Making a vacuum chuck is easy. There are all sorts of designs. I use a faceplate, some MDF, and a PVC coupling.

 

[Raul McCai]

chuck

What he a said - - twice. A vac rig will let you to off set turning too.

 

[Gerald Lawrence]

There are several articles like this out there but this one shows the chuck and may be helpful.http://mkmk.com/swiwt/PDF/Building_a_vacuum_Chuck2008[1].pdf

 

[odie]

View attachment 25150
I had a nice large poplar bowl nearly finished, trying out the Osmo Finish on, and had it mounted in my big mcpherson chuck nibbling off the tenon with the corner of my square carbide scraper. It was half gone then without any warning the bowl was slung across the room and smashed. I was using the lightest touch I could manage and still disaster struck. This isnt the first time this has happened, Ive tried every tool I can think of but it still fights me when I use one of these chucks.
I really need to built a donut chuck!

I had the bowl jammed in with the tailstock until it got too close to work so the support had to come off. So a jam chuck wouldnt have helped here. I need a positive lock on whatever surface I use. I have several vacuum pumps so Im going to look into that option. Whats the general experience using vacuum on large bowls?

Hello Gary.....I'm having a little difficulty understanding exactly what you were doing. Were you attempting to part away the tenon, while the bowl was held by both headstock and tailstock support? If that is so, then did you use two passes, so that the part gap was substantially larger than the width of the tool? If yes, and then no, the combination of these two things could be disastrous.

-----odie-----

 

[Emiliano Achaval]

The expansion works well with some designs. It is also totally incompatible with most of the designs I like.

I almost always use a tenon because
I find it much easier to true a tenon than a recess on a dry warped bowl
I can leave a center point in the tenon for recentering since the tenon gets turned away
A tenon wastes a lot less wood on natural edge bowls than a recess when I want a small foot or no foot
I don’t like having to compromise my design to accommodate a 3” hole in the bottom
I can turn features in my tenon I can’t turn anything in the hole space.
Sometimes there will be 2” for a tenon and not 4” inches for the recess and a 1/2 of wood outside it..

I do on occasion use a recess where it fits my design better than a tenon. Most often this will be platters turned from dry wood. Here the recess on some designs saves wood especially if I want a 4-5” foot for a functional platter.

You have many more design opportunities with a tenon than with a recess...

 

[William Rogers]

The fuel filters do work just fine. That is what I have before the gauge and pump. I also use a liquid filled vacuum gauge and the fun foam from Walmart that is closed cell about 1/16" thick. I make my chucks by tapping a wood block usually about 1-1/4"+ thick sealing with shellac. I use the PVC couplings, but also put a section of pipe in it and radius the end and attach the gasket material with spray adhesive. One of the nice things on my Laguna lathe is all I need to do is to screw the rotary adapter into the hand wheel, screw on the vacuum chuck and in less than 30 seconds I am ready turn.