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Stepping Up to Larger Turnings: I Have Questions

Aaron Harris

Aaron Harris

Joined
Jan 3, 2021
Messages
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Location
Spartanburg, SC
So one of the reasons I upgraded to the PM 3520C was so I could turn larger work. I just got this 14x3" kiln-dried cherry blank to make a shallow bowl/deep platter display piece for a co-worker. It will be the most massive thing I have had on the lathe yet-my biggest previously was an 11x5" maple bowl. Just the weight and heft of it have me questioning my current holding chucking methods, so please indulge a few questions:

Face-plate(s): I haven't done much on face-plates, but I thought I would start this one on a face-plate while I work on the tenon, outside/bottom. My PowerMatic faceplate that came with the lathe is just a little over 3 inches, and is dwarfed by the blank. I feel like I need a bigger one for this. Is there a size-ratio rule there? What's a good general face-plate for bigger stuff?

Chucking: I've got the RecordPower SC4 chuck, and I just ordered the 130mm jaws for bigger work. Is this big enough, or do I need even bigger jaws?

Speaking of chucking and jaws, the customer asked me to preserve as much depth as possible. What would be the minimum safe depth for the tenon? And would it be safe to put a piece this massive on a glue block? I would be afraid the torque would send it flying in the event of a catch (thankfully rare for me any more) or a quick stop.

For what it's worth, I'm taking David Ellsworth's 3-day class later this summer. I'm hoping I'll have a lot of fundamentals like this sorted out before then so that I can concentrate more on form, more advanced tool control and techniques. Anyway, thanks as always for any help! Aaron

By the way, order with confidence from https://www.turningblanks.net/ . They shipped this overnight along with a free maple spindle. I have driven down to their warehouse in Donalds, SC a few times to pick through their ample stock, and those guys always take care of me. It's just a nice, well-run family business.
Cherry 14x3 Blank.jpg
 
Your way overthinking it. A worm screw with 3 inch or larger jaws is more then enough to start that size blank with tailstock support. I just got done with an 18 inch x 5 inch deep wet blank using 4 inch jaws and a worm screw to start. With the tailstock all the screw is doing is driving the piece. The tailstock is doing a lot of the work holding the blank tight against the jaws. For a tenon a 4 inch x 1/8 or 1/4 inch is plenty for a 14 inch bowl. Another option if your planning on putting a small foot on the bowl is to do a recess. If you can reverse chuck it you can blend the recess in when your done.
 
Thanks, Chris-I do tend to over-think things. But then again, I teach Hamlet, and he was the king (well, Prince actually) of over-thinking. I may try a recess-we'll see.
 
130mm (5") jaws are plenty.

Starting the blank you have lots of options:
Faceplate (just about any size with decent screws - not deck/drywall screws)
Faceplate w/ double-side tape (and tailstock support)
Faceplate as a friction drive between centers (you can even stick sandpaper to the faceplate)
Worm screw
Between centers (assuming you have a decent drive center)
Etc

All of the above are sufficient for getting a tenon/recess cut in the bottom. Some are less well suited for a recess (live center in the way). I would be personally ok with completing the outside of a bowl using any of the above, but that depends on experience as some are inherently more "solid" than others.

Another option is to hold it somehow and cut a recess in what will be the mouth of the bowl. Flip it around and then cut your recess (or tenon) on the bottom. This is a nice arrangement in those times when you think you might need to flip the pice back-and-forth a few times (unlikely for a plain bowl, but I mention it for possible future use). Also useful if your initial hold is good enough for a tenon/recess, but makes you uncomfortable turning the outside profile.

If you make a good, clean tenon or recess that's the proper size (diameter) for your jaws (perfect circle) - 1/8" or so is deep enough.
 
I agree with Dave that 130mm jaws are plenty. I normally use 100mm jaws for 16-20" without a problem. I made a few cowboy hats with wet blanks up to 20” with tailstock support for a lot of the turning with 100mm jaws.
 
Aaron Harris said:
Chucking: I've got the RecordPower SC4 chuck, and I just ordered the 130mm jaws for bigger work. Is this big enough, or do I need even bigger jaws?
Click to expand...
What everyone said. Worm screw in the center you can use a spacer to use a shallower hole but with 3” you probably won’t need to.
With dove tail jaws you can probably do well with a 1/4” tall tenon. Recess is an option too but I prefer tenons.
My wife does a lot 14” platters with 1/8” tenons.
You can use tailstock quite far into the process after the platter is in the chuck
 
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All good advice above. Were you planning to have a foot? The answer may affect your mounting decision, but design comes first and the mounting decision should fit the design you want, IMHO.

Yes, you could use a glue block if you want. Something just smaller than the size of the foot/bottom of the bowl would be very secure, if well made.

While I, too, have been intimidated by large blanks in the past and can empathize with your concerns, as Chris points out, a 14" round blank isn't really that huge, and you can reasonably approach it as you would any other bowl. When you get to the point of mounting out of balance blocks of wood so big they're hard to get mounted to the spindle and you have to chisel off some corners so they'll spin without hitting the bed, then you're gettin' serious. ;)
 
Thanks, all-Dean, I may do a shallow foot ring that could work with a recess. Then taper it in for a more "finished" look on the bottom-still weighing my options. Anyway, all the good practical advice here makes me feel better about it. I know 14" may not be big once you've got the experience. It's just a good deal bigger than anything I've done so far.
 
A faceplate and or glue block would work fine, you will be refining the base of the turning first, so when you remove the faceplate
and start turning the inside of the plate you will remove the material that the faceplate screws were in. You can use 3/4", 1" or 1-1/4"
long wood screws to secure the wood blank to the face plate, the shorter the screw the more screws you would use. You are starting
with a round blank so most of your battle is already fought.
 
It will get better once you get the big stuff out of your blood and settle into the average 8 to 12 inch.!4 is easy but yes it is nerve racking when it is the first one. Have done 10 inch blank on 2 inch jaws and my largest jaws are 100mm for those 18 inch blanks. Starting with the worn screw is the easiest way to get there so I will also echo what others have said
 
Aaron Harris said:
So one of the reasons I upgraded to the PM 3520C was so I could turn larger work. I just got this 14x3" kiln-dried cherry blank to make a shallow bowl/deep platter display piece for a co-worker. It will be the most massive thing I have had on the lathe yet-my biggest previously was an 11x5" maple bowl. Just the weight and heft of it have me questioning my current holding chucking methods, so please indulge a few questions:

Face-plate(s): I haven't done much on face-plates, but I thought I would start this one on a face-plate while I work on the tenon, outside/bottom. My PowerMatic faceplate that came with the lathe is just a little over 3 inches, and is dwarfed by the blank. I feel like I need a bigger one for this. Is there a size-ratio rule there? What's a good general face-plate for bigger stuff?

Chucking: I've got the RecordPower SC4 chuck, and I just ordered the 130mm jaws for bigger work. Is this big enough, or do I need even bigger jaws?

Speaking of chucking and jaws, the customer asked me to preserve as much depth as possible. What would be the minimum safe depth for the tenon? And would it be safe to put a piece this massive on a glue block? I would be afraid the torque would send it flying in the event of a catch (thankfully rare for me any more) or a quick stop.

For what it's worth, I'm taking David Ellsworth's 3-day class later this summer. I'm hoping I'll have a lot of fundamentals like this sorted out before then so that I can concentrate more on form, more advanced tool control and techniques. Anyway, thanks as always for any help! Aaron

By the way, order with confidence from https://www.turningblanks.net/ . They shipped this overnight along with a free maple spindle. I have driven down to their warehouse in Donalds, SC a few times to pick through their ample stock, and those guys always take care of me. It's just a nice, well-run family business.
View attachment 52859
Click to expand...
Aaron:
You have some good questions so here is how I approach this type of turning.
I use a screw chuck on an RPSC4 chuck with 100mm jaws. I bring up the tail stock (very important) and turn my tenon. I try to make my tenon 1/4” to 3/8” deep and pay special attention to the angle of the dovetail. Once I get the dovetail cut I take another jaw and set it on the dovetail to make sure of the fit. Once done I shape the bottom a little but not all the way. Flip it over onto the chuck and finish the project. You have many good responses so have fun.
 
Forgive me if this has already been covered. IMO, worm screws are great but they also present a 'single point of failure' in connecting the wood. This is of course relative to the size of the blank and turning speed, etc. For larger pieces I personally prefer the added security, albeit mentally to be sure, of the faceplate. If your customer wishes you to preserve as much depth as possible, then I would consider (encourage) a glue block. A hot glue gun works fine or you can go with the tried and true wood glue route. If you do, remember not to use plywood/mdf. Though everyone has their own particulars they probably default to I myself like poplar. One of the added benefits of the glue block is you can either 'grab' it with the chuck or even fasten a faceplate to the glue block itself. I haven't done this myself in years but I offer it as a thought only in so much as I sense a little hesitancy. And of course...regardless of your method, use the tailstock whenever possible to help support the piece. Good luck...j
 
John Grace said:
Forgive me if this has already been covered. IMO, worm screws are great but they also present a 'single point of failure' in connecting the wood. This is of course relative to the size of the blank and turning speed, etc.
Click to expand...
Quite true if the tailstock is not used.

However when most folks use a worm screw the tailstock is used also. With the tailstock it is a very robust mounting method.

Typical platter the bottom is turned with a tenon using the worm screw and tailstock. Center point in tenon is kept.
Then, mounted in a chuck, the top is turned using the tailstock until it is in the way.
Then the platter is mounted on a vacuum chuck using the kept canter point. Then the foot is finished.
 
Aaron Harris said:
For what it's worth, I'm taking David Ellsworth's 3-day class later this summer. I'm hoping I'll have a lot of fundamentals like this sorted out before then so that I can concentrate more on form, more advanced tool control and techniques. Anyway, thanks as always for any help! Aaron
Click to expand...
Did David's class about three years ago. Great instruction, food, and conversation. A wonderful experience. Get his book as a prelude to the class. Everything we did in the three days was started between centers and a tenon made to fit the 5" Vicmarc jaws.
 
Aaron Harris said:
For what it's worth, I'm taking David Ellsworth's 3-day class later this summer
Click to expand...

It will be worth more than you will ever predict. David is a fantastic teacher.
Had a class with him in the mid 90s.
Also had the pleasure of hosting david for several week long classes he did for our club.
Great to see the growth in our club expertise.
David has done so much for AAW and Woodturning.
 
I start all of my bowl and platter turnings by drilling a 2 5/8 inch diameter recess with a big Forstner bit. I expand my Vicmark chuck into that and turn the outside. This is fine for up to 16 inch diameter or so. I seldom get bigger than that, mostly because pieces that size take a long time to sell. I also use a recess of the same diameter for turning the inside.

robo hippy
 
How you hold it is somewhat dependent on your turning skills. If you are still getting catches, a faceplate is a great idea and keeping the tailstock up against the blank is critical. The most critical factor to safety is speed. Move your belt to the smallest pulley on the motor and take it really easy at the start. Also don't try to turn the outside diameter right away. Start on the face and work your way up to the OD.
 
All my round work is started with the Nova screw and dependent on the wood (soft or hard) is the size of the drilled hole (a smaller hole for soft wood and a larger hole for hard woods). For small bowls and platters I do not use the tail stock but for medium and large bowls I use the tailstock. As I've stated before most of the time I have to loosen the chuck and remove the piece with the screw attached and take the screw out with a set of water pump pliers as the screw is in there super tight.
 
I start those pieces that I've taken the time to hit the bandsaw and roughly round on a wood worm screw - but that's increasingly rare these days. even the largest blanks start with the corners loped of with the chainsaw and between centers. Usually its the Oneway Big Bite center in a chuck with 100mm dovetail jaws, I knock it in with the spurs at 90º to the grain. Start slow, get it balanced and adjust centers until the grain is where you want it. You can get the outside form established, the face squared up (except for the center where the chuck jaws cover) and, lastly, a nice strong tenon formed. All the above with tailstock support.
When the outside is done (or nearly so), turn it around, grip by the tenon and finish truing up the face. Because I typically core every blank that's over 10" d, I turn a recess on the face to fit the 100mm jaws. Core out the guts - from large to small (I know - blasphemy). Using the recess to hold cores for a tenon.

I've used 100mm smooth dovetail jaws in a Oneway Stronghold chuck for blanks up to 24" using this same process without a problem.
 
Use the faceplate. Why not, right? I like the 4 1/2 inch faceplates from easywood. They’re inexpensive, strong and lightweight. And so easy to do. Eight 1 1/4 #10 sheet metal screws isn‘t letting that blank go anywhere. No need or point to having that tailstock in your way.
Shape the outside. Create your tenon. Foot being about a third the diameter of the rim suggests just under 5 inches. Perfect for the new chuck jaws. Make a 5 inch tenon, and a shoulder on which the jaws seat. Sight your contour through the shoulder, looking for continuing the curve from rim to rim with the low point about 1/4“ from the bottom of the tenon. (The last step is removing the shoulder to complete the curve)
Be accurate when you cut your tenon!
Complete the outside to the point of 120 grit sanding.
Reverse the bowl. If you made your tenon accurately the bowl will run true.
Turn the inside, and finish sand.
Reverse the bowl onto a jam chuck and tailstock to complete the lower section. Create a lovely foot out of the tenon (no need to remove it) If you used a vacuum chuck as your jam chuck, you’re ready to turn on vacuum and create an interior to the foot.

This is the strongest mounting strategy, and can use 100% of the blank height.

Marc
 
Lots of good replies. I have used all the above methods.
I think faceplate is the strongest. But you can chuck up very large blanks using a large tenon in a Stronghold/tower jaws or equivalent from other manufacturers.
I use worm screws a lot but not usually for really large blanks.
Elio Safe Drive 3.5" is very secure and handles wood that is not flat, is punky, or has bark for a natural edge turning. Note this is for use with the tailstock for creating a tenon or mortise for chuck mounting.
 
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