DOH moment of today - vacuum chuck related

[Jon Prouty]

My stupidity reigns supreme tonight... I got some hard maple from the lumber yard - nice chunk - 9.5" wide by 5 ft or so. I cut myself a 9.5" diameter blank of the maple and proceed to turn a nice bowl. During my hollowing process I was getting some weird reactions so I stop the lathe and find that my tenon is broken and almost separated from my bowl. Returned a larger tenon and away I went. Figuring I had already had my Murphy for this bowl, I turn to my new toy - my HoldFast vacuum chuck. Only got about 15"Hg on the meter but I figured that was enough. nope... not enough to turn away that busted chunk of tenon. Kept fighting it and couldn't get more than 10-14"Hg vacuum. Kept fiddling and getting more and more irritated. Why wouldn't this thing work? It pulls more that 22" with my hand stuck over the end of the chuck. I thought that I must not have a big enough chuck (I have the 3" version rather than the larger 6"). Finally I turned to the website for TMI Products and they suggested troubleshooting the thing with a dinner plate (non wood). Pulled 23"Hg on the dinner plate so I figured that my maple was porous which I thought wasn't possible. I reversed my bowl on the vacuum chuck and applied some DO to the inside and burnished it in with a paper towel. Added a coat of WOP on top of the DO and removed the bowl from the vacuum chuck. Flip the thing over and see where the vacuum pulled the finish right through the bowl. Sure was porous... I wouldn't have believed it until I saw it. I'll wait till tomorrow when the poly is dry and see if I can't get the bowl to stay on the vacuum chuck long enough to turn the tenon off.

That was my DOH of today - porous stupid wood. (And realizing that my donuts chuck from my previous lathe is too small to be useful - gonna have to build another for this lathe).

Night all!
Jon

[Roger Chandler]

it pays to get the 6 inch vacuum chuck as well as the 3 inch one. Porous wood will get ya every time!

[Bernie Weishapl]

Jon it does happen to the best of us. Been there done that. I agree with Roger on the chucks.

[John Keeton]

Shellac!! The quick fix for porosity. Spray a couple of coats of shellac inside and out. Give it about 30 minutes between coats. Should work on most woods, so long as there are no worm holes or knots. However, there are those pieces that no matter what you do, they won't hold a vacuum.

I would suggest that you use the tailstock for turning away the tenon - even with the vacuum chuck. Get it down to just a small pillar, saw off the pillar, and 12-14" should be enough to finish the nub.

[Scott Crumpton]

Another quick fix for porosity is sawdust. I had some leaking wormholes while turning off a tenon, simply rubbed sawdust into them and got the vacuum up from 15"Hg to around 22". Kept adding more sawdust as I exposed more worm holes. Blew the dust out with compressed air when I finished.

[Jon Prouty]

Shellac!! The quick fix for porosity. Spray a couple of coats of shellac inside and out. Give it about 30 minutes between coats. Should work on most woods, so long as there are no worm holes or knots. However, there are those pieces that no matter what you do, they won't hold a vacuum.

I would suggest that you use the tailstock for turning away the tenon - even with the vacuum chuck. Get it down to just a small pillar, saw off the pillar, and 12-14" should be enough to finish the nub.

Thanks John - Picked up a can from the BORG tonight. Paint dude looked at me cross-eyed when I told him I was looking for dewaxed shellac. I was reading the cans and found they only had it in the spray can - which works for me. Picked it up and sprayed the back. Also hit a dunno wood bowl that is not building layers of poly like I want. Hope it works on top of WOP as well.

I tried the vacuum chuck after my DO / WOP had a couple hours to cure and it pulled 22"! I was pumped - till I stopped the vacuum and found that it was pulling the finish to the surface and causing wetness (gotta be patient and let that stuff dry). Quick wipe and she is resting overnight. I'll post results on this thread once I get back to turning the rest of it.

Thanks all for the help! (6" chuck will be ordered tomorrow as well)

Jon

[Jon Prouty]

Another quick fix for porosity is sawdust. I had some leaking wormholes while turning off a tenon, simply rubbed sawdust into them and got the vacuum up from 15"Hg to around 22". Kept adding more sawdust as I exposed more worm holes. Blew the dust out with compressed air when I finished.

Thanks for the idea Scott - I woulda tried that if I could have seen the pores... I didn't think there were any and still did not believe it till I saw it.

[Steve Schlumpf]

Yup - been there... I still remember watching my finish soak into the wood and thinking to myself - Man - this stuff is really dry!!! Course when you take it off the chuck - you find all your finish coating the inside of the piece!

Another quick way to see if the wood is porous while on the vacuum chuck is to place your hand on the wood. If the wood is porous - it will be very cool to the touch and almost feel damp because of the air being sucked into it.

[Fred Perreault]

Jon.......... wait awhile, there will be other "moments". And it seems that they get more frequent, and more diverse as the years pile on.......... :) The LOML is a knitter, and a week ago she set her knitting down to give me a hand with something (doh...). She went back and couldn't find her 4th needle... she was knitting a hat. We tore the living room apart for 20 minutes, twice. It was when we picked up and turned over her chair for the 3rd time, that the needle fell out from behind her ear. It's really not for discussion what she had to help me with :) :)