Do I dare continue?

Tom Baugues

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Now that I have sharper tools I threw another piece of Mulberry on the lathe tonight and it was turning so well with shavings flying 6-8 feet across the room. I was really enjoying the process when I stopped to check my progress and noticed this long crack across the bottom. It looks to me to be a fatal crack and I'm afraid that the bowl might fly apart in halves if I continue. I have no desire to catch a 10 lb. chuck of flying wood with my face. So what do you think? Looking at the photos....would you continue to turn this?

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Vaughn McMillan

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That one looks pretty iffy, Tom. Personally, I'd possibly try turning it down a bit more to see if the crack disappears, but if your gut feeling is that it's not worth the risk, then I'd suggest abandoning it and trying a different piece of wood. ;)

As an aside, now that you've experienced how a freshly-sharpened tool cuts and feels, you'll likely see why most of us resharpen very frequently. On a piece that size, it wouldn't be unreasonable to sharpen several times during the process of making the bowl. For example, I'd want a freshly-sharpened gouge to cut through the bark, and then I'd resharpen as soon as I was through the bark and into solid wood. And I'd probably sharpen at least once more to make my finish cuts. And that's just on the inside part. I'd probably sharpen a couple of times (at least) when doing the outside, too. With a jig, it only takes a minute or less to freshen up the edge on a gouge. I see it as time well spent. :thumb:
 

Tom Baugues

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While waiting for a reply I decided to remove that piece from the lathe and started over with a new piece. The crack just seems to go all the way across and I just didn't feel safe given my limited experience.
So....on with a new chunk of the same Mulberry stock and I got back to turning. Vaughn, I see what you mean about sharpening more often as I could tell that my gouge was not cutting as well so I took it back to the grinder and freshened up the edge. I'm going to have to do something about my grinder situation because my big lathe is in my garage but my grinder with the wolverine sharpening system is out in my shop. Not far but inconvenient. So I might have to start shopping for a new grinder (slow speed this time).
Anyway, I got the new piece turned down and its starting to take shape. I hope to get it hollowed out by this weekend.
At first I thought this wood wanted to be a round hollow form, then decided I would just keep it a bowl. Maybe I'll get brave later.
That last photo shows some of the pith grain still there but that will get hollowed out from the bowl.
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Ted Calver

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Good decision. There's too much free wood out there to risk hurting yourself on a marginal piece. It's bad enough when a piece you think is solid suddenly flies apart because of some unseen flaw. One of the fundamental principles of turning is to stay out of the line of fire....always keep that in the back of your mind.
 

Tom Baugues

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Thanks Ted, I'll remember that.
I have another question...do you leave the tail stock in place when you hollow out the bowl? I have the wood held in with a chuck.
Vaughn I remembered you telling me to make the tenon smaller and I thought I did, but didn't measure it. So still working on getting that right.
 

Dave Hoskins

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Other than ditching the piece of wood in question, to salvage it I have one method that sometimes works. Of course you will have to still draw it down some more afterwards. If I am not sure how far the crack goes down I will drip in some good 'ol super glue into the crack and let it sit overnight to harden real good. Then slowly, slowly draw the wood down some more to see where it goes. If you don't feel comfortable doing that then ditch it, pitch it, or add it to the "ain't no good pile". :D
 

Ryan Mooney

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Imho good call on tossing it. I might have tried to turn it down more but ain't sure from the picture.


I try to keep the tailstock in place as long as possible. Hollow out at the rough bits and the cut the residual tenon off once the bulk of the wood is gone. I wait to finish turn until after that (if turning to finish).
 

Ted Calver

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I'm with Ryan on keeping the tailstock in place as long as possible. It might be difficult on small bowls and perhaps not so important. On larger bowls, there's a lot more mass spinning around and the tailstock pressure helps the tennon hold on better.
 

Ryan Mooney

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Yeah once you've cut the center out the weight drops a lot. It's kind of a call wether it's worth it or not on any given piece, but if it's big enough to be easy I usually figure it's worth leaving in as long as it's easy :)
 

Vaughn McMillan

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I go the opposite of Ted and Ryan, and usually get the tailstock out of the way when I reverse the piece and put it in the chuck. On very large bowls (or dicey wood) I might leave it there for a while, but in general I get it out of my way. This is all reliant on having a good tenon and a good grip with the chuck, of course.

As to the size of the tenon, there's nothing that says you can't flip the piece around and take a bit more diameter off the tenon. A common mistake many new turners makes is being afraid to remove wood. This is especially true in regards to form (where guys will make a bowl shaped more like a cylinder because they're reluctant to remove enough wood to make a smooth curve), but it also holds true for tenons (and bottoms of bowls).

My solution to reducing the number of trips to the grinder was to start collecting bowl gouges, lol. :D I've got 5 main bowl gouges, and I'll usually sharpen them all at the same time. I'll use one until it starts to get dull, then switch to a sharper one. When that one gets dull, I'll go to the next. When I run out of sharp gouges, I go back to the grinder. Even though they are different sizes ranging from 3/4" to 1/2" and two different flute shapes (V and U shapes), I use them fairly interchangeably for the most part.
 

Ted Calver

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As Vaughn suggests, there's more than one way to skin the cat and you should try them all and pick one that fits you best. Looking at your photos, I was wondering about your process. One method I often use for bowls is to mount the blank between centers using a spur drive in the head stock with a view to shaping the bottom and tennon first, so the top of the bowl is facing the head stock. I only rotate the piece by hand and adjust the position to find good balance points between centers so the piece doesn't wobble out of control to start out and I have the best grain orientation. Remove the blank and use a large forstner bit to drill a +/- 1/2" deep hole in the head stock end of the blank and re-mount the piece with the chuck on the head stock and the jaws expanded in the hole to hold the blank. That baby isn't going anywhere. (I also have a large spur drive that serves the same purpose.) With the blank secure between centers shape the bottom and create a good tennon, then flip, put the tennon into the chuck, remove as much wood as possible with the tailstock engaged, get the tailstock out of the way and finish the job. I usually rough blanks out of green wood. It's so much easier. The wood cuts like butter and the shavings fly just like the pros.:bliss:

You just have to have the patience to rough out a green bowl and then set it aside (using any of several techniques to assist drying) until you are ready to finish turn.

Another tip related to sharpening. I keep a small diamond card in my turning smock and use it to touch up the edges of tools between trips to the grinder. It works and reduces the amount of metal you remove on the tool by repeated grindings.
 
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Vaughn McMillan

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Good eye, Ted. I completely missed the fact that Tom is shaping his tenon at the headstock end. Like you, I almost always start with the bottom of the piece (bowl or hollow form) at the tailstock end. And if I'm using a spur drive at the headstock, I'll often drill a 1/2" or so deep hole for the spur drive to go into. (Mine is 3/4" in diameter, so a 3/4" Forstner bit works great.) Once I have the tenon cut and the outside of the piece to rough shape, I'll swap the piece around and put the tenon in the chuck, and then re-true the outside (if needed) and hollow out the inside. Once that's done, I'll swap it around once more to turn the tenon off.
 

Ryan Mooney

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I'll second Vaughns comment about not being afraid to remove a lot of wood if need be.

On leaving the tailstock in place.. there are a lot of ways to skin that cat. I know there are some turners who actually pre-drill the center out, which does make cutting in towards the center a bit easier. Depends a lot on the piece. The more dicy the more likely I'm going to want the extra support. If its really green that also means its softer and squishier and heavier so I like the tailstock then as well.

Like you, I almost always start with the bottom of the piece (bowl or hollow form) at the tailstock end.

Same, although I'm not sure why I do it that way.. just seemed natural :huh: I think its perhaps because I tend to have better access from the tailstock end.

Once I have the tenon cut and the outside of the piece to rough shape, I'll swap the piece around and put the tenon in the chuck, and then re-true the outside (if needed) and hollow out the inside. Once that's done, I'll swap it around once more to turn the tenon off.

Same as well, I rarely get the piece to run 100% true when swapping it onto the chuck. Especially with green wood, it always seems like there's a little movement there.
 

Tom Baugues

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Boy, I tell you.....you guys are sharp!
Ive only turned about 5-6 bowls but ALWAYS turned the tenon on the tailstock end. I had dreams of trying a live edge bowl on this piece so I started this piece differently. I changed my mind about trying to save the live edge so in order to get a deeper bowl I thought I would put the tenon on the other end which happen to be the headstock end. I wouldn’t normally do this.


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Tom Baugues

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Continued turning on this project this morning only to notice this when I was almost to the bottom. Bowl sides are still a good 1/4" thick but this thing cracked anyway. The log this came from has been in my garage for 4-5 years so its pretty dry. I may try to continue this very carefully but it just stinks that it's cracked.
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Ryan Mooney

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Yeah happens, it was likely already cracked before you started. Drying whole logs is a bit of a trick because the wood has no place to move so it introduces all sorts of weird stresses. This looks like a either a typical radial stress fracture, or possibly a fracture from when the tree was taken down from what I can deduce of the bowls position in the original tree. That's why a lot of us like to turn them green (well the other reason is that removing the bulk of the wood is so so much easier), but even then sometimes as they dry things happen.

So you're at sort of an unfortunate point in the bowl for it to crack as well. Odds are it will continue to move a little as the stress in the wood relieves (there is likely some moisture differential still as well which makes it a bit trickier to figure but even just cutting it it will move). So taking a lot of time to glue it up means you might not have a enough wood left to re-turn it. If you want to try to save it I'd saturate the crack with medium CA and finish turn it as quickly as possible. Either that or wrap the outside in plastic shrink wrap to contain the shrapnel, finish the inside, glue it, and then figure on sanding out the bumps by hand.
 

Vaughn McMillan

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I'll echo Ryan's suggestions about medium CA and stretch wrap on the outside as a precaution. I'll also add relatively low speeds, light cuts, and standing out of the line of fire (even though the stretch wrap should keep things from getting too ugly if it lets go.
 
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