Chucking into a recess--grain orientation

[Hy Tran]

So I know that expanding a chuck into a recess isn't as strong as squeezing onto a tenon--and in addition, you risk breaking your recess if you crank too hard. But sometimes, you choose to do a recess.

I'm attaching (I hope) a sketch showing grain orientation and two possible chuck orientations. Is one of the orientations better to lower the risk of breaking your recess? I'm guessing Orientation A (in my sketch, anyway). (Or is the general consensus that I'm cranking the chuck too hard anyway?)

Thanks!

 

[hockenbery]

So I know that expanding a chuck into a recess isn't as strong as squeezing onto a tenon--and in addition, you risk breaking your recess if you crank too hard. But sometimes, you choose to do a recess. I'm attaching (I hope) a sketch showing grain orientation and two possible chuck orientations. Is one of the orientations better to lower the risk of breaking your recess? I'm guessing Orientation A (in my sketch, anyway). (Or is the general consensus that I'm cranking the chuck too hard anyway?) Thanks! <img src="http://www.aawforum.org/vbforum/attachment.php?attachmentid=8779"/>

I don't think it makes much difference as far as breaking the recess.
"A" will give a better grip if the recess has gotten a tiny warp.

You need to do the standard things like turn a flat for the top,of the jaws and be sure to match the profile of the jaws.
For expanding dovetailed jaws too small an angle on the dovetail will crack the recess.

I prefer tenons too.

Al

 

[Hy Tran]

Thanks, Al--I did try to match the profile. I have an inexpensive scraper (carbon steel, I'm pretty sure) that I reground to have a flat and an angle, to match my chuck jaws (Oneway Talon, smooth #2). (Eyeball matching, not protractor matching).

I'm working on an unintentionally spalted ambrosia maple platter blank (as in I stored it badly, and it grew some mold--surprising, considering how dry it is here in NM). The wood is a bit softer than I'd like. Not punky, but just a bit softer than soft maple; but the figure is unintentionally spectacular due to the spalting.

I'm going to try to support with the tailstock for most of the inside hollowing.

Hy

 

[Joe Greiner]

I'd vote for A.

Wood is more compressible across the grain, stiffer lengthwise. B would allow more crosswise deformation, and tend to split the wood. A provides more equitable sharing of the load.

In building codes, cross-grain bending is forbidden.

 

[Hy Tran]

I'd vote for A.

Wood is more compressible across the grain, stiffer lengthwise. B would allow more crosswise deformation, and tend to split the wood. A provides more equitable sharing of the load.

In building codes, cross-grain bending is forbidden.

Thanks, Joe. Wasn't aware of building codes, but my intuition (and diagnosing a couple of broken recesses--I meant to say, redesign to a smaller bowl) suggested that I ought to pay attention to grain orientation when mounting a chuck into a recess.

 

[Jamie Straw]

A

I watched a video recently that addressed this question directly -- can get you the link tomorrow. "A" would be his strong preference, because that way each jaw is on the same type of grain orientation.

 

[john lucas]

Half way between A and B. I want each jaw to touch an equal amount of side grain and end grain. This is especially true on punky wood. The jaws will compress the side grain more than end grain so you lose some grip after the wood starts wobbling as you turn. The most important thing on expanding into a recess is the keep a fair amount of wood outside the recess and to have the recess deep enough. I use recess expanding mostly on platters because I always have a fair amount of wood to keep the jaws from breaking it. On bowls you can easily have too little wood and then you also have the leverage of having the wood extend out 3 or 4 or 5 inches away from the jaws.

 

[Bill Boehme]

The A's have it

?.. I'm attaching (I hope) a sketch showing grain orientation and two possible chuck orientations. Is one of the orientations better to lower the risk of breaking your recess? I'm guessing Orientation A (in my sketch, anyway). (Or is the general consensus that I'm cranking the chuck too hard anyway...

Definitely A because this gives each jaw equal distribution of grain orientation. Having said that, we're probably over analyzing the problem in most instances. However, a couple days ago I was pondering the same question for expansion chucking a very thin piece that was intended to become a basket illusion piece. The orientation that I chose was your "A" orientation. The recess was about 3/16" deep so minimal force was very important. As far as chucking was concerned, I guess that this could be declared a rousing success ... and, a convincing demonstration that minimal tightening torque on the the chuck key is more than adequate.

But, alas, all this good chucking was for naught. When you can see through the wood there's not much else to cheer about.

 

[hockenbery]

Definitely A because this gives each jaw equal distribution of grain orientation. Having said that, we're probably over analyzing the problem in most instances. However, a couple days ago I was pondering the same question for expansion chucking a very thin piece that was intended to become a basket illusion piece. The orientation that I chose was your "A" orientation. The recess was about 3/16" deep so minimal force was very important. As far as chucking was concerned, I guess that this could be declared a rousing success ... and, a convincing demonstration that minimal tightening torque on the the chuck key is more than adequate. But, alas, all this good chucking was for naught. When you can see through the wood there's not much else to cheer about. <img src="http://www.aawforum.org/vbforum/attachment.php?attachmentid=8781"/>

Bill we all do that now and then.
KISS
Keep the Inside Smaller S.....

 

[Hu Lowery]

forty-five degrees, tenon or recess

I try to go with the forty-five degree orientation of jaws to grain whenever I chuck wood, tenon or recess. I also have a tiny notch in one jaw so that I can put a small pencil mark to match. It lets me check for slippage and put the wood in exactly the same place if I have to take it out of the chuck and put it back in for any reason such as shutting down a few hours or overnight.

The notch and pencil mark were a help in teaching me just how little pressure is needed to hold wood too. I crushed a few tenons when I didn't know why I was losing turnings. Once I learned to tighten only enough to prevent slippage everything started working better. I also went from turning almost to where my tenons touched the face of the chuck to only about quarter inch tenons and recesses, recesses sometimes even less.

Hu

 

[robo hippy]

I cover that topic here. I also use A so the jaws are all compressing into the same grain orientation. This doesn't make much of a difference if you are turning dry wood, unless you have a very brittle wood. Since the wood is dry, there will be very little deforming due to compression. If you are turning green wood, It can make a big difference. Wet wood will compress a lot under loads, and if you turn much of it, it is wise to stop on larger projects and tighten up the chuck because the wood has moved.

https://www.youtube.com/watch?v=5KHkkws9lWA

robo hippy

 

[Hy Tran]

Thanks for all the input, folks.

I like to think that I sharpen decently, but I'm definitely still not good at presenting the tool to the wood. (Hello, Mr. Maple, I'd like to introduce you to Mr. Spindle Gouge. Mr. Gouge comes from an air-hardening tool steel who's been tempered to Rc 62. Mr. Gouge, this is Ambrosia Maple. Mr. Maple was cut into a blank while still green, then, sealed. Mr. Maple has been aging for a year on the shelf. Mr. Gouge will come across the face to define a sharp foot transition--unfortunately, even after that lengthy dialogue, Mr. Gouge and Mr. Wood differ on angles...) Hence, I've had some unidentified flying bowls and platters. (I'm sure I will make some flying saucers too...)