Large Hollowforms: From 6" faceplate to 4" base

[John Tisdale]

Here are a couple of pics on one approach to large hollowforms some may find of interest:
1) The rigors of hollowing require a faceplate - on a "large hollowform", a 6"
2) Holes should be predrilled to a tightly controlled depth - the outer screws should allow for the curve of the piece - I grind the tips off of 1" screws as the tips add nothing to the holding power.
3) Last step after final hollowing and final shaping is to remove the outer screws - no problem since you're back on the live center
4) Then "dive under" with small gouge, parting tool, and detail gouge to complete the profile
5) Cut the annular ring that will be the base which leaves about a 3" to 3.5" tenon.
6) I then remove the faceplate and mount a floor flange for 1/2" pipe - provides a convenient way to handle for subsequent sanding and finishing operations

 

[Clifton C]

Thanks John, I really enjoy "methods of work" posts. After the sanding and finishing, is it back on the lathe to remove the remains of the tenon, or is that a, it depends on the piece question?

 

[DON FRANK]

That post helped me a lot. Thanks!

 

[John Tisdale]

Thanks John, I really enjoy "methods of work" posts. After the sanding and finishing, is it back on the lathe to remove the remains of the tenon, or is that a, it depends on the piece question?

The tenon is removed after finishing and sanding. The process is:
1) Barrier / sealer / sealer
2) Pour in low viscosity untinted epoxy, swirl around, and wipe out excess - if some runs out on the outside, no problem.
3) Fill problems with dark brwn epoxy or water-base Timbermate. No problem with staining - the barrier prevents that.
4) Sand all fillers and outside to 500. I start with a 3" or 5" DA with 250 then hand sand to 500. I only use a DA with 3/32 orbit - you can spend a bunch with Dynabrade or a little on a AirVantage from The Sanding Glove. A paper-back 250-grit is great for removing orange-peel - I find hand sanding to be more efficient after that - Eagle Assilex is best for hand sanding and is available from turningwood.com.
5) Then another barrier / sealer / sealer. I use a 000 sable-hair brush to correct little pits - the piece dries with a bunch of bumps which is no problem to sand off.
6) Then another 250-grit on the DA for orange-peel and hand sand to 700ish.
7) The piece goes back on the lathe with Kelton mandrel, tenon removed and a concave cavity is cut. I typically uses a dovetail scraper and try to make the cavity at least 3/8 deep. If the annular ring base is 1/4", the scraper starts the cavity at that point and follows the outside to the desired depth.
8) I paint a little barrier in the cavity and sign with a paint pen
9) The piece then goes on my "umbrella fixture" - four coats of automotive clear coat are applied - if the surface is not perfect, it shows - clear coat doesn't hide anything.
10) Back to DA with 700 - 800 grit Eagle Yellow paper back (cloth back doesn't remove orange-peel). Then hand sand with Eagle Assilex to 1000 / 1500 / 2000 / 3000. The Assilex is amazing stuff - who'd think you could dry sand to 3000 and actually see the results of each stroke as you go.
11) After that it's compound (Wizard Purple is great stuff) - first with wool and then with yellow foam on a 3" palm buffer (not DA).

Hopefully bits-n-pieces of the above will be of value. If the above is actually understandable and interesting, you may need help.
John
ps. In a Woodenboat magazine about 20 or so years ago, I read a lengthy article on butt-blocks by Giffy Hill, boat repairman Somewhere, Maine. I actually found it interesting. I remember parts of it - if you want to talk butt-blocks, I'm your guy.

 

[Bill Boehme]

@John Tisdale could you explain to der dummkopf like me what DA means.

I thought that butt blocks were a soccer maneuver.

 

[Clifton C]

Incredibly valuable, and... I know I need help...
I thought this sport was supposed to be cheaper then therapy???

 

[John Tisdale]

DA is a Dual-Action Sander and they come in all flavors: pneumatic or electric, palm or larger, aggressive (5/8" orbit for house painters, 3/8 for rapid removal, 3/16 is considered "finishing" sander, and 3/32 for us timid souls afraid to screw up.
A lot of guys really like Mirka and Festool - they have a vacuum system and great for smaller shops. I like AirVantage's 3/32 3" and 5". Lot's of cool product out there.

COMMENT: As I give advice please remember my definition of an expert: A guy that knows how to have sex 35-ways but doesn't know any girls. (never personally used a Mirka or Festool sander)