Grain orientation in a glue-up for a vacuum chuck

[Sam Fleisher]

I'm in the process of gathering the items needed to make a couple of vacuum chucks and rather than buy a solid blank I'm going to get some local kiln dried hard maple that is 1.75 thick glue two together and have it 3.5 thick.

Is there an advantage of gluing one board with the grain perpendicular to provide more stability or am I just over thinking it again? Would that just make it harder to turn with more end grain?

I'm going so thick because with the axminster faceplate ring the screws line up almost exactly with the pvc coupler plus by the time I true everything up with my luck it won't be that thick.

 

[Kevin Jenness]

I'm in the process of gathering the items needed to make a couple of vacuum chucks and rather than buy a solid blank I'm going to get some local kiln dried hard maple that is 1.75 thick glue two together and have it 3.5 thick.

Is there an advantage of gluing one board with the grain perpendicular to provide more stability or am I just over thinking it again? Would that just make it harder to turn with more end grain?

I'm going so thick because with the axminster faceplate ring the screws line up almost exactly with the pvc coupler plus by the time I true everything up with my luck it won't be that thick.

Just align the grain direction. Two pieces glued together crossgrain is inviting trouble. Three pieces with the outer two at 90* to the center one is better but unnecessary in this scenario.

I

 

[Tom Gall]

Use shorter screws ... the groove for the PVC shouldn't have to be that deep. Alternative approach: glue a 1/2" or 3/4" disc (or thicker) to your maple / turn to match the ID of your PVC coupling / slide coupling over the disc / drill 3-4 small holes through PVC into disc and screw on / use silicone (or other) to eliminate leaks. Also, if you are using your spindle as the vacuum tube (my preference) seal the endgrain very well on your maple and maybe even the vacuum hole.

 

[Sam Fleisher]

Use shorter screws ... the groove for the PVC shouldn't have to be that deep. Alternative approach: glue a 1/2" or 3/4" disc (or thicker) to your maple / turn to match the ID of your PVC coupling / slide coupling over the disc / drill 3-4 small holes through PVC into disc and screw on / use silicone (or other) to eliminate leaks. Also, if you are using your spindle as the vacuum tube (my preference) seal the endgrain very well on your maple and maybe even the vacuum hole.

Kind of in a gray area. #10 screws are as big as will fit in the faceplate ring and still sit flush but when you take in the thickness of the ring and a shorter screw doesn't leave a lot sticking into the wood and if I go longer on just a 1.75 board then I'm into what is recommended for the groove.
If I were to glue on a piece for the coupler to slide over I might as well just do the groove. I wasn't worried about the block sticking out too far. Unless I need to be?
This is the "frugal vacuum system" so the bearing will be in the chuck with a poly tube running through the spindle.

 

[Gerald Lawrence]

Since you are doing "Frugal" you can use PVC for the body. Cut a groove in a straight grained piece and drill for the Bering. Gluing the bering in is the tricky part to avoid getting glue in it. Glue the PVC in with epoxy and use foam for a seal. You can even make the nut to attach to lathe with wood and tap with a Beal tap and glue onto chuck

 

[Tom Gall]

Kind of in a gray area. #10 screws are as big as will fit in the faceplate ring and still sit flush but when you take in the thickness of the ring and a shorter screw doesn't leave a lot sticking into the wood and if I go longer on just a 1.75 board then I'm into what is recommended for the groove.
If I were to glue on a piece for the coupler to slide over I might as well just do the groove. I wasn't worried about the block sticking out too far. Unless I need to be?
This is the "frugal vacuum system" so the bearing will be in the chuck with a poly tube running through the spindle.

Sam, just trying to be helpful here. I've been using vacuum since 1994 and have about 20-25 chucks in different sizes and types, and for all different purposes. You seem to be locked in to your process .... so do what you want. All my chucks have faceplates (large & small), threaded inserts, blocks of wood with a tenon for the chuck to grip, or some tapped to fit my spindle (for smaller stuff). I've used 3/4" MDF, PVC board, and some plastic/acrylic for smaller chucks. Sometimes single thickness and sometimes doubled up - never more than 1.5" thick.
Other thoughts: Screws come in different lengths / The glued on piece will eliminate the need for your groove or for a more shallow one / Use a different size coupler - or just use the Sched. 40/80 pipe itself which will be slightly narrower / Yes, the further out from the spindle there is the possibility for vibration. However, most vacuum applications won't have that much of an effect. Good luck!

 

[Sam Fleisher]

I guess I could have made my post more clear in the first sentence instead of the last one.

Maybe I am locked into my process a little but I am following loosely the instructions for making a frugal chuck provided by Bob. My faceplate happens to be a ring instead of the type that screws onto the spindle. Axminster faceplate ring for "c" jaws.
I want to retain the ease of leaving the four jaw chuck on the lathe and just installing the vacuum chuck/cup when needed. The pvc coupler is being used because even though Bob doesn't sell the "angel wings" that are sold on the "odd not" site he must have access because one is coming with my bearings and pump so it's pretty critical that I use the schedule 40 - 3 inch coupler to have the correct diameter otherwise the seal won't work.
To be clear, I would give that Oddnot set up a try as well if I could get the back of the aluminum hub machined to work with my four jaw chuck but I haven't received a response from that guy about that.

I also realize that by the time I get done truing everything up I'm not going to have a 3.5 inch thick piece of wood with my coupler sticking out from there. I'll be able to make it as thin as I need to avoid the shortest possible screws which there are many lengths available.

Not trying to be difficult here, I realize that when I post sometimes my processes are different because in my head I have a plan but it's hard for people to know everything when they also have a way of doing things and can't read my mind.

So, back to the original post, I believe I'll glue them both with the grain the same and more than likely will end up with a 2 - 2.25 inch thick circle either by design or by my not so great ability to make a somewhat flat surface which I know doesn't really have to be perfect because the groove will take care of making it all coplanar.

 

[Brian Gustin]

Didn't read the replies very carefully, but my first thought is, how would you expect a vacuum chuck made of wood to hold vacuum? I'd think porous wood would leak vacuum if it was the chuck side of things? (shows what I know I don't even use vacuum chucks, and honestly don't have a lot of interest in doing so at the moment.)

 

[GRJensen]

Didn't read the replies very carefully, but my first thought is, how would you expect a vacuum chuck made of wood to hold vacuum? I'd think porous wood would leak vacuum if it was the chuck side of things? (shows what I know I don't even use vacuum chucks, and honestly don't have a lot of interest in doing so at the moment.)

It is pretty easy to do. I have 4 vacuum chucks made with Baltic Burch plywood. I just sealed them with resin after I turned and tapped them ... they hold vacuum just fine.

 

[Brian Gustin]

It is pretty easy to do. I have 4 vacuum chucks made with Baltic Burch plywood. I just sealed them with resin after I turned and tapped them ... they hold vacuum just fine.

Yeah I think the key point would be "sealed with resin" essentially the chuck is made of resin, the wood is just the form that holds its shape.

 

[GRJensen]

Yeah I think the key point would be "sealed with resin" essentially the chuck is made of resin, the wood is just the form that holds its shape.

Not really ... the PVC is epoxied into a groove in the plywood. The only part coated with resin is the plywood at the bottom of the PVC.

 

[Sam Fleisher]

Well, the use of my axminster faceplate rings and the vacuum chucks with the adapters might not work.

While in the process of making the damn egg for the challenge earlier I happened to stick just the faceplate ring on the chuck by itself and the hole through the center isn't very big due to the scroll parts (called accessory mounting jaws) that the actual jaws are bolted too.

Can anyone using the "frugal set up" tell me what the outside diameter of the short stubby section coming directly out of the bearing is? In the instructions it says the tube that goes through the spindle is 3/8 but I couldn't find mention of the short section on the bearing that the 3/8 tube gets pushed into.

I didn't have a way to get an accurate measurement but the shaft of the "t" wrench for tightening the chuck wouldn't go through the center with the faceplate ring in place. It's a little under 5/8" so I'm assuming metric of some kind. And I was trying to use a tape measure on a round shaft.

This could really put a kabosh on my plans with the vacuum chucks. Especially since I already bought the rings and mounted them and the pvc adapters getting ready for the bearings to get here.

 

[Dave Landers]

Can anyone using the "frugal set up" tell me what the outside diameter of the short stubby section coming directly out of the bearing is? In the instructions it says the tube that goes through the spindle is 3/8 but I couldn't find mention of the short section on the bearing that the 3/8 tube gets pushed into.

That short tube is a shade over 1/2" (I measure the main tube as a shade over 3/8).

FWIW, this is how I have my all vacuum chucks fixured - PVC glued into wood with tenons for several sized chucks. I picked the sizes based on what chucks would likely have been on the lathe for a piece needing that size vacuum chuck. The one in the photo fits 3 different chuck jaws (one has seen better days) - is just concentric rings/grooves or sometimes steps. All these fit as tenons on the jaws - one of my vacuum chucks has one for a recess because that's how I could get it to fit in the sequence.

 

[Sam Fleisher]

My problem is I already have the adapters epoxied onto the wood with the faceplate ring attached. Was anticpating just having to drill the hole for the bearing and being ready to go.

Now it looks like I might be back to square one because I doubt I'll be able to turn a tenon on the back of the vacuum chucks accurately with the pvc already in place on the front. Might as well start over and make new vacuum chucks without the plan of leaving the four jaw on there using the axminster faceplate ring or have a tenon at least big enough so the tube will go through the four jaw. 'll take a picture in a little bit to make it clearer.

I'm guessing the line is to place it the same each time?

I'm going to have to check on what hole size in the center will be for my "c" jaws because they are the ones I use the most and might be smaller than a mortise which is what the faceplate ring would be considered on these.

 

[hockenbery]

problem is I already have the adapters epoxied onto the wood with the faceplate ring attached. Was anticpating just having to drill the hole for the bearing and being ready to go.

So why not use these?

Most of my vacuum chucks are on faceplates.
They just have a hole and the i draw vacuum through the spindle.

 

[Sam Fleisher]

So why not use these?

Most of my vacuum chucks are on faceplates.
They just have a hole and the i draw vacuum through the spindle.

That is the axminster face plate ring for the "c" jaws on my sk114 chuck. The jaws expand into the center of the ring to hold it with a dove tail. When the chuck jaws expand into that ring there still isn't enough diameter in the center of the sk114 chuck for the frugal system vacuum tube I don't think. I'm afraid it's going to be so close that it will not be able to stay stationary. Drawing vacuum through the spindle wouldn't work with these rings because I don't think you could ever get a good seal.

I already have this ring attached to the back of the wood base when I trued it up and epoxied in the pvc adapters on the front. Luckily I stopped at two.

Plan B I guess is direct threading without the chuck because with the 114 I'd have to put a pretty big tenon to get a big enough hole for the vacuum tube.

One saving grace is maybe the 3/8 will fit through the hole in the center of the 114 chuck if I shorten the stub coming off the back of the frugal bearing setup. Second photo.

 

[Sam Fleisher]

It's going to be so close, I went to the shop and found a 3/8" aluminum rod, a 1/2" aluminum tube and the diameter on my t-handle is 5/8".
The 3/8" rod barely fits through the spindle. It's snug. The 1/2" tube fits through the center hole in the chuck with the faceplate ring attached but the 5/8" "T" handle won't. Fingers crossed I guess. Word is the vacuum pump and accessories are supposed to be getting shipped maybe next week.