Chucking inside a recess

[Reed Gray]

Bill, I think I cover the loose jaw screws in my video. First couple of times it happened, it took a while to figure it out. If run out is 1/16 inch or less, don't worry about it because that means plus/minus 1/32 of an inch, which is very close. My finish cut on the inside of a recess is a shear scraper, instead of a bevel rub cut, and I use Doug Thompson's small fluteless gouge, which I show in the video link up above. Small tools can fit inside a recess. The thing with the shear scrape, since you are not rubbing the bevel, you don't get any bounce from the different wood grain directions. You can do okay with a bevel rubbing cut, but the shear scrape does a better job. Do make checking those screws a regular thing...

robo hippy

[Bill Jobe]

Bill, I think I cover the loose jaw screws in my video. First couple of times it happened, it took a while to figure it out. If run out is 1/16 inch or less, don't worry about it because that means plus/minus 1/32 of an inch, which is very close. My finish cut on the inside of a recess is a shear scraper, instead of a bevel rub cut, and I use Doug Thompson's small fluteless gouge, which I show in the video link up above. Small tools can fit inside a recess. The thing with the shear scrape, since you are not rubbing the bevel, you don't get any bounce from the different wood grain directions. You can do okay with a bevel rubbing cut, but the shear scrape does a better job. Do make checking those screws a regular thing...

robo hippy

Yes, I've cut some very pronounced unevenness caused by using the wrong/improperly sharpened tools.
Each time at the lathe can be very humbling. Today I was hollowing out the bowl when the piece came out of the chuck. At first I thought I had broken off the glued on piece I added to get a deeper bowl and a longer base. Turned out the wood gave out and I was able to put it between centers to carefully hollow out a new recess to chuck in. Had I not added that piece the beautiful walnut I've been hording would be firewood.

[Bill Jobe]

Thank you all for your advice and suggestions. And thank you for the photos, Leo.

Had a guy stop by as I was at the lathe near the overhead door where I drag it to. Turns out he's only a block away from me. He was particularly interested in my walnut slabs I'm using to make large, very shallow bowls. I have (had) 4 4-5" x 6' slabs that were kiln dried by my son-in-law's friend.
He really liked the 0766 as well. He wants a bigger lathe but just can't decide if he'd use it enough to justify the cost. Sounds like we can help one another. He has a 14" midi that he has had for many years.
But I'm going to have to keep a closer eye on my walnut from now on.

[John K Jordan]

...
But I'm going to have to keep a closer eye on my walnut from now on.

Ha! But a good way to be and make a friend is to share just a little. If he doesn't have a band saw a round 8-10" blank would make a great gift!

JKJ

[Michael Mills]

In addition to other suggestions, Alan Batty has some good videos on the fundamentals of turning.
There are seven that he typically covers but at Vimeo they are broken down more (such as three on stance, tool overhang, etc)
There are three on chucks, recesses, and tenons. Presented very persnickety but that is very good.
https://vimeo.com/woodturning/videos...rmat:thumbnail

You should try to match the angle of your dovetail as close as possible. My Novas are 15* but others are 10* or 7* IIRC.
One tip I read was to tighten the jaws down on a business card then mark the card with a sharpie. You then have a template to make a tool or transfer to a more durable gauge (tin or hard plastic).

[Bill Jobe]

As always, possible ways to proceed depend on several things: size, type of blank (rough chunk or plank?), green or dry wood, tools on hand, how perfect you want it to be.

FWIW, I work basically the same way as Bill:

- Mount the block on one end. If starting with a plank with mostly parallel sides I cut round on the bandsaw then most often use a screw chuck (Glaser) or turn a tenon on the lathe, or drill a recess with a Forstner bit. If a irregular chuck of wood I might flatten one side off the lathe for a screw chuck or a faceplate or flatten or cut a tenon between centers on the lathe for a chuck. This will be the top of the bowl.

Then,
- Mount the block with screw chuck, scroll chuck, or faceplate.
- Flatten what will be the foot. Turn the outside of the bowl. Turn a tenon, recess, glue block, etc. to hold by the base.
- Mount the base on the lathe and hollow the inside.

Assuming this is dry wood, how perfectly round I want it to be the outside may need to be trued both before and after turning the inside. Before, due to slight irregularities in the wood at the point of mounting, and after due to to the wood moving by the hollowing. Wood almost always has internal stresses - hollowing can allow these stresses to relax and the wood will move. When I make a lidded box or bowl that requires a good lid fit I follow Raffan's advice and let the piece sit overnight after turning close to the final wall thickness. The next day it almost always requires truing. Green wood, of course, requires other methods. Just like from stresses, the wood can also move a little if there is residual moisture in the dry blank or as the newly exposed dry wood acclimates to the conditions in the shop.

As for a trued blank not running perfectly true when turned around, there are several things I can think of that could be going on. One, every time a chuck is tightened in a recess or on a tenon the steel can press unevenly into the wood as it deforms it slightly. Some wood is worse than others. For example, if the jaws press more into one side than the other due to a softer spot there, the whole blank can be shifted or tilted slightly. Two, if there is any "fuzz" in the bottom of the recess (or a bit of sawdust) it can keep the jaws from contacting perfectly. This can even happen when mounting the chuck on the lathe! When mounting a chuck, Chris Ramsey, in a demo on turning a cowboy hat, made a point of first carefully cleaning any sawdust away from the contact points on the chuck on the lathe spindle. (And never use a fiber or plastic spindle washer! - they are notorious for causing problems)

I usually don't worry about the outside being very slightly out of true with the inside unless the walls are very thin or I want to turn detail on or below the rim which will require touching the outside. In this case, I might true up just the upper part of the outside and blend the transition. I usually true twice or more: once after first mounting, again after hollowing the inside, and maybe again if the wood moves a bit after it sits on the lathe a while.

Oh, another thing that can cause it to run out of true when chucked: the chuck jaws themselves may be slightly out of true. You can check this on tightened jaws with a dial indicator (turning the spindle by hand) but it may be different when the jaws are expanded. When machining some chuck jaws recently to make them absolutely true for precision work, I expanded the jaws into a ring I made to take up any play. This worked very well.

JKJ

John, I'd like to know more about the process using the ring you said you made.

[John K Jordan]

John, I'd like to know more about the process using the ring you said you made.

All gears and most mechanisms have some play or they may be too tight to operate. The backlash in gears can be significant. What I did was machine a ring to simulate expanding the jaws tightly into the exact size of recess I wanted to grip, in this case 22mm. I expanded the jaws until they were snug in the ring, enough to take up any slop/play in the jaws and scroll mechanism. Then I turned the jaws down to the precisely 22mm diameter. This way when I expanded them in to my 22mm recess the diameter was also 22mm and the jaws fit as tightly as they possibly could and in perfect alignment.

Since I machined it mounted on the exact lathe spindle I would mounting the chuck on, any runout was removed as well.

The value of going to all this trouble is more when the hole is significantly different from the closed jaw diameter, for example expanding 50mm jaws into a 75mm hole. The disadvantage of modifying a chuck this way is it will only work optimally on a hole of one diameter. And if machined for expansion, there is nothing to say the accuracy in contraction would not be had. Probably not worth the effort for general purpose chuck and jaws.

JKJ

[Bill Jobe]

I understand. Not something worth doing working with wood, unless that exact diameter recess could be made on every piece. But definitely when turning metal. Or do you actually turn certain shapes where you control the recess that close? I recall you telling me you had quite a number of chuck's.

There were a few of sets of chuck jaws machined that way when I worked at the shop, but that work was performed strictly by journeymen. Union shop, you know. Sometimes on the very machine used for production, always on the very chuck used for that production piece and that piece only.

Are you a journeyman machinist? Much of your postings give me that impression.

[John K Jordan]

I understand. Not something worth doing working with wood, unless that exact diameter recess could be made on every piece. But definitely when turning metal. Or do you actually turn certain shapes where you control the recess that close? I recall you telling me you had quite a number of chuck's.

There were a few of sets of chuck jaws machined that way when I worked at the shop, but that work was performed strictly by journeymen. Union shop, you know. Sometimes on the very machine used for production, always on the very chuck used for that production piece and that piece only.

Are you a journeyman machinist? Much of your postings give me that impression.

You can never have too many chucks! I did a demo at the turning club last night and showed how two with the same jaws are useful for making a lidded box for the Beads of Courage.

I actually posted about preparing the expansion chuck before, but didn't go into a much detail on the chucking. I wanted to make some of the quickly moving faddish fidget spinners and wanted something to hold the pieces with repeatable precision. The balance and runout is critical on these. The hole for the bearings I use is 22mm. If they were made from metal or from a metal sleeve bonded to the wood it would have been easy but to hold an arbitrary piece on the wood lathe then turn it around to do the other side I wanted the chuck as precise as I could make it.

The first thing I tried was a simple tenon with a press fit. Then an expanding collet chuck turned from a piece of wood. This worked better but I wanted something more precise. Just because.

FidgetJamChuckMG_20170621_110144_768.jpg wood_expanding_chuck.jpg

I machined a set of steel pin chuck jaws down while mounted on my PM3520b, using woodturning tools. The first time I compressed the jaws around shims to get the diameter right but I still wasn't happy with the result when expanded to that diameter so I made the ring and turned the jaws again in the expansion mode. I'll leave those jaws on that chuck and use them only with that machine. That may seem like a waste of a general-purpose chuck! But I have 16 chucks and making these for a special purpose for expansion doesn't change their utility for what I always use them for - compression on small pieces. (I keep three chucks with small 25 mm spigot and pin jaws.)

Turning the steel on the wood lathe was far easier than I expected, although slow. I've turned a lot of brass and aluminum that way but this was my first try with steel. I used Thompson tools, mostly a scraper I ground just for this. I did have to sharpen several times. Sorry, I didn't take a picture of when I turned these the second time with the expansion constraint ring.

turning-steel_IMG_20170605_081521_124.jpg

In use with a piece of cocobolo:

Fidget_mounted_IMG_20170619_215544_445.jpg

I made a handful of the spinners but this is the only one I photographed. I turned the brass weights on the metal lathe. I have another made from carved cocobolo I'll get around to finishing some day!

spinner_cocobolo_brass_IMG_6217.jpg

I'm not a machinist although I play one in my ongoing untelevised shop docudrama. I have a metal lathe and a couple of milling machines, weld shop, and some other metalworking things and love to play, make tools, and fix things around the farm and for friends. I'm self taught from a library of books, a few videos, and a bunch of experimenting. My background is hard-core technical software development and scientific/technical 3D computer graphics, modeling, and animation. Retired in '06 and traded that for horses, peacocks, a herd of llamas and driving around the farm singing "Green Acres." Life is good.

JKJ

[Randy Heinemann]

A lot of responses already but . . I am fairly new to turning and have done the following since starting. I only have turned bowls and a few small ornaments. I don't believe I've ever had any real problems with the blank vibrating too much once it's trued up on the outside and the first side facing out. Is it perfectly trued? Probably not, but I don't notice any significant vibration and it appears true.

1. Cut the blank round and drill a hole in the center for mounting on a screw.
2. Mount the blank on the "worm screw" and true up the edges and face which is exposed.
3. Turn the outside of the bowl.
4. Cut a dovetail recess in the bottom of the bowl (still the outward face). Since I bought a dovetail chisel from Nova (I have a Nova lathe and chuck.) I have found that I only need a recess that is very shallow since the Nova chisel cuts at the same angle as the edges of the chuck. My recesses have only been about 1/8" to 3/16" since I've used the chisel but I am doing bowls 8" or less so far.
5. Sand the outside and bottom.
6. Flip the bowl around and secure via the recess over the chuck. At this point, I usually do true up the face that is outward now. This might not be necessary but sometimes it makes the blank turn more to my satisfaction. I was taught this when learning so I guess I've just continued. It doesn't do any harm, but might not be necessary.
7. Cut the inside of the bowl and reshape the upper part of the outside, if necessary to make it work with the lip of the bowl, if necessary.
8. Finish sand.

I don't remember every really having any vibration problems due to the blank not being trued up after the initial steps. I have found that it is important to be sure that, when flipping the blank and mounting the recess on the chuck, to be sure that the blank is as tight as possible against the chuck while tightening so I put a little bit of extra pressure against the chuck until it's tight in the blank.

[John Keeton]

Randy, you were taught well and obviously learned well! Good synopsis.

[John K Jordan]

Randy, you were taught well and obviously learned well! Good synopsis.

I agree with JK - very well thought out and written, Randy. I envy those who think logically and can also write clearly - I like to blame my own rambling posts on ADHHHDD!

JKJ

[Harold Balzonia]

I agree with JK - very well thought out and written, Randy. I envy those who think logically and can also write clearly - I like to blame my own rambling posts on ADHHHDD!

JKJ

Don't sell yourself short JKJ - I might be your biggest fan!

You could write a treatise on how to drain an abscess from an alpaca's hoo-hah and I'd read every word!

[Randy Heinemann]

John Keeton & John K. Jordan - I appreciate the vote of confidence. I feel that my modest success so far has been due, in large part, to 2 classes I took from the same turner; the first one teaching me the basics and the second to correct technique problems I was experiencing.

While I assimilate a lot of knowledge from books and videos, I have always felt there is nothing better than a hands-on class or two from a good teacher to push you in the right direction. The rest is mostly practice and patience.

Again, thanks for the comments. I'm not always that good at setting down my thoughts.

Randy

[John K Jordan]

Don't sell yourself short JKJ - I might be your biggest fan!

You could write a treatise on how to drain an abscess from an alpaca's hoo-hah and I'd read every word!

Ha! Made me laugh! Thanks. I think my problem is knowing how to consolidate and when to stop - I can almost type faster than I can think!

When you come visit will can pull fecal samples from the llamas and alpacas in your honor. "Pull" is the appropriate word there - the process involves disposable surgical gloves.

JKJ