Advice on work holding

[Percy]

I have recently bought a number of pieces of bog oak. They are all large pieces from the base of the tree, so they are very irregular shapes with bits of root buttress, etc, but seem very sound and solid. They all have very nice sculptural shapes that I am keen to keep whilst trying to turn away some of the middle to make vessels that will show of the beauty of the wood inside.

Does anybody have any good advice on holding the pieces so I can retain the external shape without leaving any visible signs of mounting/chucking whilst enabling me to turn the inside?

I am experienced at turning irregular lumps of wood and burrs, but these bog oak lumps are quite large, and very wiggly indeed. I would love to turn them without cutting them up first. Any bright ideas would be welcome!

The photo below shows the smallest lump I have (it is propping up an ash vessel but the lump of oak is around 14 inches in length)

[Derek]

I would use a faceplate with spacers as needed and various screws the more the merrier this hopefully will allow you to turn a chucking pint for the hollowing

[bodrighywood]

Face plate with spacers / wedges and hogt glue. Make sure that you are not gluing bark though and that the glue is really dripping hot when applying. Keep the speed down low to start and wear a face mask.

Pete

[Percy]

Thanks for the advice chaps. If I use screws, won't I still mark the outside of the piece with screw holes? This is what I am trying to avoid. The only way this would work is if I mount the blank on the face plate and then hollow around the mounting until I turn the bit I want to keep off its mounting point.....not sure I fancy this! At least the screw holes would be in the bit I don't want to keep though.

The lumps are too irregular to vacuum chuck (I don't have one of these anyway!). I might investigate trying to fix the wood to a large plywood mounting plate with 'non-invasive' fixings. I'm still considering the best way to do this. Maybe a combination of shims and packing, hot glue, and a selection of large jubilee clips or steel banding to hold the blank onto its backing plate? Any further advice is welcome - I'm still thinking of new daft ideas!

All points taken about low speed and face masks. I might even fit the large cage that Powermatic supply with their larger lathes to provide a little safety backup...!

[The Bowler Hatted Turner]

Percy I think I would be inclined to build a round plywood box to fit the piece in and mount that on the lathe securely with the work inside of it. With a combination of judiciously placed hot glue and slots cut in the box to allow for jubilee clips you should be able to afely mount it for turning at a slow speed. With all of those protrusions you only need a second's lapse and you will get a nasty knock.

[John Plater]

I think that BHT has it. A similar approach would be to mount a plywood blank on your faceplate against which the intended base of the piece will fit. Then have a second piece of plywood with a hole cut out through which you can do your hollowing. Attach this to the base plywood with lengths of studding, washers and nuts, thus clamping the wood in place in between. Clingfilm and tape is a good idea with Bog Oak as there is precious little guarantee of structural integrity. In fact the only guarantee is the potential for grief !!!
Wear plenty of PPE because you are going to come out looking like you've "bin darn t' pit" !
ATB John

[The Bowler Hatted Turner]

Actually John's suggestion is probably an easier solution and after reading his comments how about making a donut chuck with holes or cut outs for the projecting pieces, that would work very well.

[bodrighywood]

Have to agree, looking at the wood that would probably be the safest option by far.

Pete

[Twisted Trees]

Totally agree John has got the best answer, from the picture structural integrity looks very suspect, so wrap it, clamp it in plywood, go slow! and don't stand in the firing line!

But sometimes the most difficult, and dangerous gives the best rewards, please post an after picture of that piece.

[Percy]

Thank you for all the answers and help. I think John's solution is the one I will try. I will post an update when/if I have something to show for my trouble! Cheers all.

[hughie]

I think that BHT has it. A similar approach would be to mount a plywood blank on your faceplate against which the intended base of the piece will fit. Then have a second piece of plywood with a hole cut out through which you can do your hollowing. Attach this to the base plywood with lengths of studding, washers and nuts, thus clamping the wood in place in between. Clingfilm and tape is a good idea with Bog Oak as there is precious little guarantee of structural integrity. In fact the only guarantee is the potential for grief !!!
Wear plenty of PPE because you are going to come out looking like you've "bin darn t' pit" !
ATB John

Sounds familiar, I use a modified donut chuck on the occasion this arises. Then do some of the rough turning there until it can be held by a chuck.