Help with endgrain hollowing

[Lee Alkureishi]

Hi all,

I decided to try a slightly bigger endgrain hollow form, and am encountering some challenges. Was hoping to get some advice from the collective!

Please note - I realize that all of the problems I describe are related primarily to my technique. The advice I'm seeking is for ways to improve the situation while my technique improves; I acknowledge that none of these are "magic bullets" or easy fixes!

So, here's what I have: a walnut hollowform, turned endgrain from a whole log. It measures 9.5" tall, 5" at its widest point, with a 3" tenon. The opening at the top is about 2" wide.

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I turned the outside between centres, and it went well - just like a spindle turning. I turned the tenon, and reversed the piece onto my chuck, a PSI barracuda 4.

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I then started hollowing the endgrain, using a combination of my oland tool, and shopmade carbide scrapers (radius square, and circle). It's slow going, but I don't mind that. The problem is I still get a few catches, and when I do, the piece is knocked off axis in the chuck i.e. the chuck is still tight, but the piece is now running (very) untrue. This requires me to loosen the chuck, reseat the piece, retighten the chuck, and start again. As you can see, it's happened more than once!

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So, here are my questions:

1) Is it silly to try to hollow a piece of these dimensions without a steady rest? I am planning to build one (or two), but didn't think these dimensions would require it.

2) Is it expected that a moderate catch will pull the piece out of the chuck jaws?

3) If not, is there a problem with my tenon? it's pretty much 90 degrees, which I thought is correct for these jaws...

Any other suggestions on how to improve things would be much appreciated - I really like the outside of this form, and would love to finish the thing!

Thanks,

Lee

[Scott Hackler]

Lee,

The very first thing I would do with this piece would be to drill the biggest hole you can using the tailstock and a Jacob's chuck. Then with a hollowing tool (you know the ones with the small "scaper" on the end) start hollowing it a little at a time from the edge of the hole to the side of the vessel. Now your hollowing side grain!! Take light passes and clean out the shavings often.

If tight in the chuck and you don't try to "hog it out", you shouldn't have to wory about a steady rest at this size.

[Thom Sturgill]

The flat on your tenon must be FLAT. Get a good ruler with a flat edge and check that no light passes between it and the tenon. Even the slightest 'overcut' (lower at the edge than at the point the tenon meets the flat) will allow the pice to lever itself out. A very slight undercut is acceptable. The face of the jaw needs to meet the wood at its widest point. In your picture it appears that you have a severe overcut.

[Harry Robinette]

+1 for what Scott said.

[Mike Peace]

As you found out there is a lot of leverage on a tall HF. Your tenon looks like it has a nice clean 90 degree shoulder but it looks like a long tenon. I can't tell from the picture but you need to make sure the tenon does not bottom out in the bottom of the chuck. I can't tell what size jaws you are using but they are open too far for the best hold. You should not have more than a 1/4" gap between the jaws for the best hold. For a good hold it appears you could use larger jaws. If your jaws are not big enough, you might want to consider a face plate. A lot of skilled HF turners recommend faceplates over chucks.

[Steve Schlumpf]

Lee - lots of good advice so far... and I can only add my take on things.

First thing I recommend is to turn the tenon down somewhat so that the jaws of your chuck can close a little more. Believe it or not - it makes a huge difference in holding power.

Next thing is to make sure - seeing as how this is endgrain - hollow from the center out. Scott's recommendation of drilling a hole through the piece to assist is a good one... but you can hollow without it.

Make sure that you hollow at the centerline - or slightly above it. When the tool wanders below the centerline, you get the instant catch! Exciting - isn't it?

While a steady rest is probably not needed for a turning this size... it would not hurt.

Good luck with everything and I look forward to seeing the finished form!

[Lee Alkureishi]

thank your all for the awesome advice - this is exactly what I was looking for.

I have a drilled hole, but was hollowing toward the centre. I think I was at centre line, but may have been slightly below. Will try those 2 things and report back! It's too late to change the size of the tenon on this piece, but that is a great little gem of info too.

I'm pretty sure the tenon is at 90 degrees - will check when I get home. I agree, the picture makes it look less than optimal! The chuck jaws are (I think) #2. The tenon doesn't bottom out - that's the one thing I already knew (yay me!).

Again, thanks for the great advice - if anyone has some more tips, keep 'em coming!

Lee

[robert baccus]

Deep hollowing is really tough due to the leverage the vase has. I do vases/urns mostly in the 8"--16" range and this is what worksfor me. I turn mostly green wood (easier) and find that faceplates & screws in end grain are not very reliable in soft green woods. I CA the wood to a strong glueblock (walnut+) with thick glue and a trued glueblock (1.5") screwed with blue concrete screws to a 3-4" faceplate. Make your set up relative to the weight and length of your hollow form natch. I find that tenon mounting to be very limited on heavy pieces especially where hollowing is planned. Also no wood is lost to screw clearance. Old forester

[Fred Belknap]

Scott's advise on drilling is good, I just want to add that it needs to be drilled to the bottom. If you end up with a tit in the middle of the bottom it is hard to get it cut off with end grain in a vase type turning..

[Jon McElwain]

I had a lot of trouble turning end grain until I really got a handle on cutting with the grain vs. against the grain. When you cut towards the center you are working against the grain and it will tend to catch. Also, I started using a ring tool and that improved my speed and quality of cut greatly. The DVD "Turnaround" by Jimmy Clewes has a great discussion about end grain turning. He goes through a number of turning tools and the pro's and con's of each. I use this ring tool (http://www.oneway.ca/index.php?option=com_virtuemart&page=shop.browse&category_id=12&Itemid=2). It also helps cut off that little nib left on the bottom that Fred was talking about!

[Reed Gray]

I am not sure about what sized cutters you are using. Most hollow form cutters are at most 1/4 inch, and down to 1/8 inch wide. Makes it a big slower than you can go on a bowl, but easier to control, especially as you start to hang way out there. 1/2 inch wide would be hard to handle.

robo hippy

[Kyle Iwamoto]

You can fix your tenon. Turn a jam chuck to fit in the top of your HF and flip it around and square off the shoulders and bottom. Use the tailstock to keep everything tight. You can cut right up to the live center. If you have stuff left in the center of you HF tenon, it doesn't matter.

[Thom Sturgill]

Kyle and Steve are right on about tenon size. I started with that chuck and jaws and had no end of problems until I replaced the jaws with the dovetail jaws.

[robert baccus]

Just an add-on to my reply above. This glue system has worked flawlessly on 8-10 vases in the 100-120# sizes, all in green wood and 100+ in lesser sizes. If i tried this for a demo it would probably launch a 5# bowl into orbit?

[robert baccus]

Just an add-on to my above reply. This glue/block/vase setup has worked flawsly on 8-10 pieces in the 100-125# weight class and scores of pieces of lesser weight. They were turned, hollowed, sanded and finished on the lathe. Haven't figured how to sign it on the lathe yet. I also suggest trying the Woodcut hollowing cutter with the limiter. It really is catchfree to 18"+ on my controled homemade rig. Leaves a nice surface too as it cuts rather than the usual scrapers. Probably hollows 5 times faster than a 3/16" cutter which I am very familiar with, especially on green woods.