Thread: WIP: deep hollowing

Originally Posted by hughie

Yup thats what I would do, Back of the chuck and tighten up the steady, get running true and tighten the chuck and away you go again

Exactly. To get it running true, hold off on tightening the steady, and use a revolving cone centre on the tailstock. In lieu of buying one ($$$), make one for the purpose at hand - doesn't have to be one size fits all. If the vase must be removed from the lathe to make this accessory, mark the jaw numbers on the tenon for accurate re-mounting.

With the chuck just barely loose, use the cone centre for alignment. Tighten the steady and the chuck, then pull the tailstock. Even with "perfect" alignment, you may need to re-sand the outside slightly except near the steady, where blending should work fine.

Instead of direct use of the lungs for a compressor, add a piece of vinyl tubing about 300mm long. BTDT.

Joe

Thanks guys. Will have a fiddle.

Should work if the form's off centre rather than out of round.

Joe, good tip. Had been wondering about something like that for when the parting off takes place - there's designs out there for moving cones on a shaft which also supports the bottom.

Though again, if the opening is out of round ...

(Yeah, was using a tube ... did a fine job of clearing out the bore right into the schnozz ... think maybe two feet would be better ).

Hi rsser
I have found when deep boring with whatever bit is used,using the vacuum cleaner helps keep the chips from clogging the bit,sure beats blowing out with a piece of tubing.Works for removing the curlies from the hollow when you attack with your hollowing tool of choice.
Cheers
gidgee 1

Thanks gidgee; yeah, could get the vac in once the hollowing started but the depth hole boring was too small to get it in, hence the tube blow job. (Hope one of us enjoyed it).

I've taken the form off the lathe for a bit of a holiday. Attending to 3 green crotch pieces of Sycamore from Rowie. The crotch figure doesn't go very deep so preserving it has brought new things to figure out.

Meantime I've ordered three John Jordan hollowing tools ... couldn't resist; the shafts are really well done. And the service is excellent.

Originally Posted by rsser

Though again, if the opening is out of round ...

There are probably more skilled ways to do it, but in my ignorance I just bumble along with simple principles. My experiments were made on a vase similar to yours in shape but much shorter (190mm hollowed 160mm bottom chucked in expansion mode). Turned a truncated cone, sticked 60 grit on it, trued the opening with it under the drill press, took off the sandpaper, put the truncated cone on the tailstock, rechucked the piece held centered by the cone in the opening, trued the outside.

Thanks F&E.

Will file that idea away.

The bead is too small to solve this problem that way, though retruing the outside might be the shortest way home.

What's the timber of yours? Got some nice figure there.

Meantime I've roughed out four pieces of the sycamore, one or two with spekky figure that IIRC Rowie called 'angel step'. Not in this crotch piece however (in which the figure is somewhat clouded by drying grain sealer).

.

To get it running true, hold off on tightening the steady, and use a revolving cone centre on the tailstock.

even better!

Originally Posted by rsser

What's the timber of yours? Got some nice figure there.

AKA Crapiata by the prejudiced.

Frank nice vase

Had a fiddle; reseating in the chuck produced no improvement - the run-out is about 30 thou where the steady wheels track.

One of those wheels however is out of true and will be replaced, and I'll try a layer or two of duct tape on the form's low spots where the steady sits.

Afterthoughts as to why there was so much vibration and so little run-out:

1. Out of true wheel wouldn't have helped, but I figure I had all wheels pressing too hard anyway. (btw, the bad wheel was the one of three I hadn't checked with a dial gauge mounted on the bed cos it was too high; you can be unlucky.)

2. Still could be flex in the piece but there's a lot of meat there and it would seem unlikely.

Originally Posted by rsser

Had a fiddle; reseating in the chuck produced no improvement - the run-out is about 30 thou where the steady wheels track.

One of those wheels however is out of true and will be replaced, and I'll try a layer or two of duct tape on the form's low spots where the steady sits.

Afterthoughts as to why there was so much vibration and so little run-out:

1. Out of true wheel wouldn't have helped, but I figure I had all wheels pressing too hard anyway. (btw, the bad wheel was the one of three I hadn't checked with a dial gauge mounted on the bed cos it was too high; you can be unlucky.)

2. Still could be flex in the piece but there's a lot of meat there and it would seem unlikely.

30 Thou??? In the scheme of things this is negligible.

My thoughts on the runout.
Is the vase seating against the front or the base of the jaws? It should be seated on the front of the jaws with the extreme base of the vase clear of the bottom of the jaws.

The steady is just that. A steady, and in extreme circumstances (like we have sometimes ) should not be used to straighten an out of line article.

The grain can compress and cause the steady to "ride" on bumpy ground.

Looking at the picture of the vase, the steady was probably running on a knot and then "soft" timber.

Overtightening a steady can defeat the purpose by compressing the grain even further.

Soft wheels on a steady also allow vibrating moments to be set up at certain speeds. Slowing down or speeding up sometimes eliminates this.

Ern, if you can't true it up in the chuck, take some light cuts to bring it back to round, fit the steadly lightly and start hollowing.

You may find that the timber has warped a little and gone out of round. Cypress can sometimes do that particularly around the knots.

Many thanks for the tips .

In turn ( ahem), yep, 30 thou is nothing so something else was causing the gross vibration.

Shoulder seated at front of jaws, slight though it is.

Yes, wheels pressing in too tight at the beginning might well have done some compression.

But the wheels are running on clear grain.

Spinning the piece without the steady it runs smooth; think I've been paranoid with the steady (though really the need for it is yet to appear as I go further than the current 3").

Hi peoples,

Originally Posted by Frank&Earnest

AKA Crapiata by the prejudiced.

Frank&Earnest, I absolutely admire that vase of yours, is just something different and pleasantly colourful, with those pieces of "knotty pine" from the stock I collected from the local pine plantation. Just beautifully executed also, my congrats...!



Cheers
RBTCO

Thanks RBTCO, the bill for the advertisement is in the mail.