Cracks in maple blank...how to assess

[Jamie Straw]

The maple blank below had no cracks in it after I took it off the bandsaw and mounted it to the lathe. It's fairly dense (for BLM). I stopped a few times as I was to knocking the corners off. While adjusting the tool rest the last time, I noticed the two cracks in the picture. I'm thinking the shorter one isn't much to worry about, at least right now, but the longer one is headed directly toward where the tenon/foot would be. Though it seems very close to the surface, its orientation and how quickly it got that length concerns me. FYI, the dimensions of that area are about 4" x 4.5". How do we evaluate such things?

 

[john lucas]

I'm having trouble in my new shop. the Gas heater blows hot air across the shop. It's in the opposite corner of the room from my lathe. However I brought a piece of what I thought was dry Hickory in and put it on my workbench. I'm having to store my wood in a building that has water running through it when it rains real hard so the wood apparently has a higher moisture content than totally dry. Anyway I noticed some fairly deep cracks starting. That's really go me worried. My guess for your situation is the crack may have already been in the wood you just didn't see it. When it started to dry while spinning on the lathe it opened up. Don't know, purely guessing. Or it could be something similar to my situation where warm air is blowing on it making it try to dry on the outside which always leads to checks.

 

[hockenbery]

I'm thinking like John that the cram was there an began opening up when younger it inside .
It looks like an end grain crack and may not be real deep

End checks are difficult to prevent in stored wood.
I leave my blank material in 2-3 foot long 1/2 logs with sealer on the end grain.
It will get end checks but they are rarely deeper than an inch in a month or two.
I cut the blank just before turning on the bandsaw cutting off a couple of inches from the end to get rid of the end checks.

Al

 

[robo hippy]

Well, for me, I toss pieces like that. It is small, and I would expect the crack to run through it in very short order if you don't turn it to finish soon. If you want to finish turn it, turn to final shape, fill the crack with medium CA glue, and/or sawdust. Then turn out the inside. Oh, use a tenon, not a recess. Depending on how much CA you flood into it, the inside may still be tacky and spray glue all over you, the lathe, your face mask, and tools. More saw dust.... Any time I am turning, unless the piece is kiln dried, I turn it to completion. Letting it sit causes cracks, just because. If you let it sit, even if it is kind of, or mostly dry, cover it in plastic, and with a bit of water. Cracks can happen in minutes.

robo hippy

 

[Odie]

Well, for me, I toss pieces like that. It is small, and I would expect the crack to run through it in very short order if you don't turn it to finish soon. If you want to finish turn it, turn to final shape, fill the crack with medium CA glue, and/or sawdust. Then turn out the inside. Oh, use a tenon, not a recess. Depending on how much CA you flood into it, the inside may still be tacky and spray glue all over you, the lathe, your face mask, and tools. More saw dust.... Any time I am turning, unless the piece is kiln dried, I turn it to completion. Letting it sit causes cracks, just because. If you let it sit, even if it is kind of, or mostly dry, cover it in plastic, and with a bit of water. Cracks can happen in minutes.

robo hippy

I have roughed bowls partially, and have gone to dinner, or let it sit for a short time.....cracks appear. It's best to cover all surfaces completely in anchorseal, or equivalent, until you return. The others are correct.....you may not notice a small crack appear at first, but quickly becomes a major problem in short time. If it's already there, there's not much you can do to prevent it from enlarging. Anchorseal will retard the crack from becoming larger.....others are using CA for the same reason.

ko

 

[Jamie Straw]

Firewood....

Well, when I got back into the shop mid-day, it had developed another crack, and the smaller crack from yesterday had lengthened. It will help keep us warm this evening. I'm half-way through turning another piece of maple, so far so good.

 

[Odie]

Well, when I got back into the shop mid-day, it had developed another crack, and the smaller crack from yesterday had lengthened. It will help keep us warm this evening. I'm half-way through turning another piece of maple, so far so good.

Jamie......There is likely not one turner here who hasn't lost a bowl because it cracked up in the roughing stage. Some pieces of wood are more prone than others, but the likelihood can be minimized by immediately sealing moisture in....in effect, retarding moisture release.

Also, there is something else that can contribute to developing cracks during the roughing stage......My idea of what is sharp, has changed over time, and this is another thing that can be a factor. Sharp tools create less friction than less-than-sharp tools. That friction tends to heat up the immediate surface, and will cause surface cracks that will spread deeper with time. They may not be big enough to be very noticeable, but once the crack is established, it's difficult to keep it from enlarging......especially if there is a high moisture content. Heat will cause rapid moisture loss at the very surface, and this is the right circumstances for creating tiny surface cracks. I have no idea what level of sharpness your tools have, so this may, or may not have been a factor for you.

edit note: A super-sharp tool may be overdoing it by some who consider the prospect.....but, a super-sharp tool will quickly dull to a level of sharpness that is sustainable for a longer period of time. If a turner is satisfied with a level of sharpness that is less sharp than that which can be sustained realistically, then there is obviously a gap between what is acceptable, and a higher degree of sharpness that is realistically sustainable. In the end, sharp tools are not a guarantee that cracks won't occur, but it is one more thing that can help to prevent them......

ko

 

[john lucas]

Odie mentioned coating the bowl if you leave it. What I do is put a plastic bag over the bowl any time I leave it even to take a bathroom break. Lost too many to surface checks. In the early days my turning was a lot slower and I lost more probably do to drying while I was turning. I started squirting water on them to keep the outside wet. That, the plastic bag and my increased speed of turning has eliminated most cracks.

 

[robo hippy]

I doesn't hurt it to use a mister to get the surface wet if you have to go away for a bit, and cover with plastic. Keeps the humidity up, and you cut away the wet wood with your first finish cut when you get back.

robo hippy

 

[Jamie Straw]

Odie mentioned coating the bowl if you leave it. What I do is put a plastic bag over the bowl any time I leave it even to take a bathroom break. Lost too many to surface checks. In the early days my turning was a lot slower and I lost more probably do to drying while I was turning. I started squirting water on them to keep the outside wet. That, the plastic bag and my increased speed of turning has eliminated most cracks.

I doesn't hurt it to use a mister to get the surface wet if you have to go away for a bit, and cover with plastic. Keeps the humidity up, and you cut away the wet wood with your first finish cut when you get back.

robo hippy

I've always done the above when turning green wood, but with dry wood I've generally done the bag thing only if I have to leave a piece overnight and generally not sprayed it. The cracks appeared very quickly after bandsawing and starting the rough turning. A couple of things probably contributed: (a) The wood was "dry" but hadn't been living in the shop ( biggest factor, probably) and (b) there was stress inside as evidenced by the wrinkles on the surface, which is why I picked that piece -- hoping for some figure inside.

The piece I'm finishing up right now has the tiniest little crack on the outside, short and not deep. I CA'd it last night, just finished turning the inside. I'm going to sand and start Watco right away. I think it'll be OK. Thanks, guys!