WIP: your thoughts

[rsser]

My first effort at deep hollowing. Pics below.

It's cypress, about 24cm square and 50cm long. Aim was to turn a tapered vase with a shoulder at the top.

Pic 1: mounted with a cup centre at the tailstock to distribute the load, and 2 spur 1" drive at the business end.

Pic 2: trued at about 500 rpm. Plan was to turn a spigot at the headstock end and mount that sacrificial end in Titan Powergrips, but in the pic you can see a branch with bark which poses a challenge. It runs right through the centre, and 90 degrees around there's another smaller one that does the same. Both have some voids.

So what are the options?

1. Lop that end off and end up with something very much smaller
2. Continue and call it a rustic piece 😀
3. Reverse the piece and see how it might go at the foot.
4. Change the design? ... to what?

Thoughts:

1. It's a practice piece for deep hollowing, so no to 1

2. Prob option 2 is best in keeping with the original design intention, though the knots will make for bumpy hollowing and strength will be compromised. Can wrap some duct tape round it though.

3. Option 3 would increase the ratio of unsound to sound wood at the bottom where the narrowing taper will have to carry a deal of force and it's likely that one or both branches will fly out.

4. Redesign?

As this is a practice piece I'm happy not to go down to translucent thickness ;-}

Will hollow with the Munro and Proforme tools, so little chance of catches.

Would appreciate your thoughts.

 

[Charlie Knighton]

thoughts

that's about 20 inches long, how has it cut and felt so far (as in solid)

do you have any doubts about doing it safely? i will be interested in your progress with this piece :cool2:

 

[Dan Wickles]

Epoxy Good, Bad or Ugly?

Being new to turning I will throw this out.

If the knot is loose enough, knock it out and epoxy it back in.

I am sure I will find out from the others if epoxy has a place in wood turning.

 

[MichaelMouse]

The grain is sweetest near the knot, isn't it? I just change design when I get caught in my own efforts to push the envelope. There's always another chunk.

If you're into rescues, you can do the CA routine and hope for the best. Just remember that once is not enough, and keep after the area. Alternative is to hollow until you can knock it out and make "art" out of it.

 

[Bernie Weishapl]

I had one similar to that with the knots at one end. I reversed it on the lathe so the tapered end was where the knots are. On mine they happen to turn out so all was well. I had another one I just took the knot out and finished turning it. It came out pretty well.

 

[Steve Worcester]

Why not do a long HF where the end of the knot just crests the apex of the top curve. With including a knot you have to make it proud. It has to look very intentional and not that you tried like hell to turn it out, but it wouldn't go away, so you left it.

 

[rsser]

Thanks for the ideas and advice folks.

Around most of the perimeter of both branches are voids and coarse bark. Too much to fill with CA; epoxy maybe - never tried it. Expect the knots will have to be glued to stay in there. Don't fancy one being pitched at me at speed.

Great idea Steve of making a virtue out of necessity; will take some care and planning.

 

[plamb]

Indecision?

First post having been a member of AAW for many years, turning for a little over 22 years and still learning. I don't do many hollow forms. That said I would agree with the suggested use of CA as needed. Turn away! Depending on your original design or slightly modified, the inclusion may be mostly turned away. You never know if you don't try.
plamb

 

[Al Neighbors]

Too much to fill with CA; epoxy maybe - never tried it. Expect the knots will have to be glued to stay in there.

Ern, I've heard that CA sets too brittle... unless you have the type that doesn't... and will crack loose with changes in humidity.
Epoxy that I have used... called 2-ton epoxy, in the cheap, two-tube-one-spout gizmo. I haven't had any that came loose on me, yet. I mix it slow and easy to keep the bubbles down, and apply it rather slowly to fill small voids. It needs to set overnight to really cure.
Just info.🙂

 

[rsser]

Yeah, I'm happy to suck it and see - it's just wood after all, but as noted, both branches run to or through the centre and so they're not going to be turned away.

Added: thanks Al; appreciated.

 

[Richard Baker]

Ern,
You probably know this already, but you can thin epoxy with a little DNA or ethanol so it will flow into the cracks and voids more easily. Will need to tape the "bottom" side if voids run all the way through. Need to let set up overnight.

You have potential for a very interesting piece. Have fun.

 

[rsser]

Thanks for that tip Richard.

... might be annointing the cypress with another type of DNA before it's done 😉

 

[James McClure]

Steady Rest???

Are you going to use a steady rest? That's a long way to hang off especially if you are holding it with a chuck. I would use a faceplate.

 

[rsser]

Hi James,

Yes, it is a long overhang.

My spindle steady is a bit small; it may fit towards the bottom of the form - have yet to see.

I'll try the jaws - they're substantial and may do the job. With screws there's the risk of pulling out of softish endgrain.

 

[GeorgeH]

Well, OK, it's been four days. So let's see what the finished piece looks like😀

 

[rsser]

😀

... minor matter of work getting in the way

Will do some filling tonight and tomorrow and have at it on Sat.

 

[George Guadiane]

Thanks for the ideas and advice folks.

Around most of the perimeter of both branches are voids and coarse bark. Too much to fill with CA; epoxy maybe - never tried it. Expect the knots will have to be glued to stay in there. Don't fancy one being pitched at me at speed.

Great idea Steve of making a virtue out of necessity; will take some care and planning.

Once you have the outside form (whatever you decide), use some pallet wrap/stretch wrap around the knotty area. That should keep the knots from flying out, and you will be able to hear them if they come loose and remove them safely.

 

[rsser]

Good thinking Batman ;-}

 

[Charlie Knighton]

wip

bump......

 

[rsser]

Sigh. Not a lot to report.

Filling took longer; chores took Sat., family took Sunday.

But the steady rest will fit the piece half way or more away from the tailstock and the Proforme hollowing head on shop-made shaft may just reach the bottom. Shaft however is only 5/8" and will be prone to flex or bending.

There's a lot of tear-out at the bottom branch piece so I'll have a go at reverse turning it out - that explains the pencil line in the photo.

 

[Charlie Knighton]

wip

great progress, not measured in time

what did you use to fill knot holes???

Shaft however is only 5/8" and will be prone to flex or bending.

i have never attemped hollowing over 10 to 11 inches, that with 1 inch square elbo tool, 5/8 inch may be a might thin, but you are making progress, look forward to learning as you turn it, thanks for sharing 😀

 

[rsser]

Thanks for the encouragement bb.

Fill is epoxy mixed with dry coffee grounds about 1:1

(Smells a lot better than epoxy on its own ;-} )

I decided just to fill the surface voids rather than deeper and the thickened epoxy worked fine for this.

I may have to mount the Proforme hollower is a 3/4 shaft which is the biggest the hollowing rig will take. Suck it and see first.

 

[rsser]

OK, got some shed time last night.

Had to turn down the shoulder to clean up more fills and that left the belly looking bloated so the line had to be refined.

Had at it with a bowl gouge and did a lousy job. Never had to do such a long line before. (Did roughing out with a forged spindle gouge but lacked the courage to use it to take a whole new line). So cleaned it up with a scraper; shear or flat seemed to make little difference to the finish off the tool.

The dropping of the shoulder has revealed the voids as you can see but I did manage to get an almost unbroken bead to define the top opening. Would have liked a larger bead but there's not enough meat left for it.

Some concerns ...

I hadn't left much of a tenon shoulder to square the jaws on so a big push sideways while hollowing may well break it away.

It's a shortbed lathe (well, shortish) so I'm not sure there'll be space for everything - steady, rig, long shaft. Will suck it and see.

Not sure how well the rig will allow presentation of the Munro hollower to undercut the shoulder, and Proforme head to track down the inside.

The VM hollowing tool rest has a laser to track the position of the cutting edge - the rig is an articulated arm - so I'm assuming I can reset the laser point for the various changes of line by running the cutting tool down the outside of the form and judging the offset from that. Sound do-able?

Next steps:

Sand and finish the outside
Mount in chuck and steady to turn away the top stub
Depth drill with a saw-tooth bit with extension
Start in on the hollowing.

This one's a real adventure 🙄

 

[Joe Greiner]

The VM hollowing tool rest has a laser to track the position of the cutting edge - the rig is an articulated arm - so I'm assuming I can reset the laser point for the various changes of line by running the cutting tool down the outside of the form and judging the offset from that. Sound do-able?

We had a demo at our WT club a few months ago, and that's it exactly. Reset the offset so that the laser target is perpendicular to the wall as the curve sweeps along the piece. Except you lost me with the bit about "running the cutting tool down the outside." I think you just need to gauge the angle from the slope at the depth where it's cutting, and set the offset to agree with the wall thickness. Below the shoulder on this piece, the angle looks fairly constant.

Joe

 

[rsser]

Thanks Joe.

Hmm. Let's say for purposes of illustration that that shoulder was a tight curve through 90 degrees and too far in to see or feel. As the cutter starts through the curve the laser should be reset opposite it and at 90 degrees to the wall ... but loosening off the laser arm mounts to reposition it will deprive me of the only ref. point that tells me where the cutter is ... ? Make sense?

Added: so thinking this over since posting, I guess you could locate the cutting edge provided you'd gone around the first half or so of the curve taking a thickish cut leaving a shoulder as a stop for the cutter.

 

[Joe Greiner]

I'm definitely not the voice of experience on this, Ern. At least not yet. I'd be inclined to draw a plan view of the outside profile, and sketch the cutter's final location at various depths, including the inclination of the shank with respect to the lathe axis. Remove the sketch toward the tailstock for working space. Mark the shank where it would enter the hole for future reference, and set the laser target to suit. This should be easy enough with a captive D-frame, not so sure about the articulated ones. The Elbo tool, though, has the laser attached to the shank with a magnetic switch, which makes adjustment easier. Same as the base for a dial indicator, and would work well on the D-frame too. On my ever-expanding list of unfinished projects, which I may or may not live to complete.

If you can't reach in to see or feel, nobody else can either, so interior grooves wouldn't be sinful. One of our WT club's professional turners leaves even the visible and tactile grooves unfinished.

Joe

 

[rsser]

Thanks Joe.

Yeah, I'm not fussed about grooves - leastways not beyond finger length 😉 , only concern is going through the wall.

There's a website out there where a turner has written up his template follower system as an alt. to laser - maybe he had the same problem I'm having. [Added: right in the neighbourhood! http://www.aawforum.org/vbforum/showthread.php?p=37557#post37557]

Pic of the rig attached.

 

[Joe Greiner]

Stan Harder's template-boring rig looks top notch. One of the reasons I made my four-wheel steady was to allow use of the laser. But I also considered using a template mounted at the top of the headstock housing for varying wall thickness, with the laser spot shining on the template. Stan's rig eliminates the laser AND allows tracing in the region of the steady.

"right in the neighbourhood": Yeah. About 300km shorter than the distance from Melbourne to Alice Springs, as the crow flies. Almost 800 miles if I was a crow.

Joe

 

[rsser]

Bit more progress ...

Have gone down 3" and undercut the shoulder using the Proforme slightly and seriously bent shafts in an Irons toolgate.

One small bit of epoxy fill has flung out and the hole will have to stay. I've reinforced the internally exposed knot bark with CA and blended in the line between the outside turned centre and the inside with 80 grit paper. It looks OK.

There was a good deal of vibration; the three wheels on the steady don't contact all the way around and that could be cos the cypress has gone out of round or maybe the wheels aren't round. Next thing to check before I go deeper.