How large of a blank can I mount on a Powermatic 3220B?

[Esteban Churin]

A (wonderful) neighbor surprised me with a huge "blank" which is about 25 inches square and 8 inches thick. Needless to say, very heavy... The largest blank I've ever used in my Powermatic 3220B was 15 inches. Now it is very tempting to try to go BIG. But how big? Wise wood turners out there, what is the largest size/weight I can mount on my lathe while operating safely and not damaging my beloved lathe?
Thank you.
Esteban

 

[Clifton C]

I know you love your lathe, but your noggin cannot be replaced...

 

[hockenbery]

15" to 25" is a big jump.
Big pieces have more potential danger, take a lot longer, may require mechanical assistance to mount them.
I don't think you will hurt the powermatic a bit with that block.

From a practical point of view the 20"'powermaric can turn an 18" bowl between centers quite nicely.
This allows the movement of the banjo.

Above 20" diameter you have to work off the end of the lathe w/o the tailstock for support and added safety. What tool rest would you have for the end work?
Using a free standing tool rest introduces more complexity and a few more things that can go wrong.

Consider cutting a nice grain balanced 18" bowl blank,from the block.
This is not that much of jump from a 15"'bowl and you can use the tailstock while roughing.
You may be able to get blanks for other object from the cutoffs.

If you want to go big platters are a bit less of a problem than big bowls and generally there are a lot more folks who would want a 24" platter in their home than a 24" bowl.
you could chainsaw 4 platter blanks. 1 3/4" thick.

Have fun, work safely

 

[Leo Van Der Loo]

Maybe you would be better off to make four 12.5” blocks from that wood, and maybe slice some into two thinner slabs, many more bowls can be safely made from that big piece of wood, but I know new turners like to make this humungous bowl, ............. and than what to do with it.

Without a way to core this large piece of wood, all but a little of that wood is going to end up on the floor.

Also turning a very large bowl isn’t like turning a 12” bowl, the speed at which you can safely rotate a large piece is pretty low, this means turning the center part also at this slow speed, you should try doing that first with a smaller piece of wood, spinning it a say 60 or 70 rpm and then turn it, you will get the idea, it will give you an idea on how time consuming this is going to be, much longer than most do realize.

I’m not trying to tell you not to turn that big bowl, but try to appreciate what it will take and the end result you’ll have.

Then there is the safety factor, a catch isn’t going to stop or stall that heavy lump of wood, you can easily get hurt with doing this, or damage your lathe, your lathe isn’t really build for such heavy wood.

Yes it can be done with care and experience of turning larger pieces, just make sure you have that before starting on it, be safe.

 

[Esteban Churin]

All,

I appreciate very much your comments, even if they bring my enthusiasm down to earth! I love woodturning and the objective is to have a good time and make pieces that I can offer to family and friends, not to get hurt or damage the lathe.

I think I'll follow Al's advice and go for a kind of 18" platter.

I appreciate you taking the time of pointing me into a reasonable and safe direction.

 

[Mike Brazeau]

You could take a 3" slice off for a platter and still make a nice size bowl. 4-5" thick is enough for a bowl. I have a Oneway 2436 and the largest bowl I have roughed out was 21-22". Never finished as it has a rotten spot. Have a 17" natural edge salad bowl and it is too big to store anywhere. A big bowl makes a good place for a cat to relax!

 

[Bill Boehme]

.... A big bowl makes a good place for a cat to relax!

Not that there's anything wrong with that.

 

[john lucas]

Depending on where and how you use the tool rest you can turn something a hair under 20". By the time you get it roughed out a little under that. Over the banjo is a fair amount smaller, probably 18" or less. Turn a big one just to say you've done it and then go back to turning what is reasonable. Large bowls don't sell well and unless they are short don't even sit on a table as a display very well. I still have 2 roughed out blanks that have been sitting for years simply because they are such a hassle to finish and sand and I won't be able to sell it.

 

[odie]

I know new turners like to make this humungous bowl, ............. and than what to do with it.

Yes......

Turn a big one just to say you've done it and then go back to turning what is reasonable. Large bowls don't sell well and unless they are short don't even sit on a table as a display very well.

Yes, again!

Well, there you have it!

Big bowls have the "wow" factor, but aren't very sale-able, and because they are very time consuming, are necessarily very expensive. My lathe has a 16" swing, so I'm incapable of going beyond that without adding an outboard attachment......but, I have no desire to do that. In all these years, there has been only once where someone has requested a bowl larger than I am capable of turning. Besides, from my experience, a bowl in the 12"-15" range makes a salad, or centerpiece bowl big enough to satisfy nearly everyone who is looking for one. Now, if you just want to be part of "the big bowl club", there are those turners who measure your skill level by the size of the bowl you have produced.......so, don't get sucked into that mind-set, unless you really do want to go big for your own personal satisfaction. Making a finely crafted medium sized bowl takes every bit as much skill level to produce than the huge bowls. There is a recognizable difference in skill between designs and shapes that require very little sanding straight from the tool, and those simple shapes that require a great deal of sanding......it's all in the details!

ko

 

[Bill Boehme]

Big bowls are very sellable if they're free. I made an 18" bowl for Mrs. B. and then the neighbor lady saw it and wanted one like it so now I have another 18" bowl on the lathe nearly finished. And now SIL wants one as well.

Even though these big bowls have a wall thickness that is slightly over one inch, they can be much more challenging to turn than a small thin walled bowl. As Leo said, the lathe speed has to be slow because the centrifugal force at the rim can cause a lot of force pushing the shape out of round and this can lead to a lot of vibrating so very light cuts are necessary as well as keeping your tools very sharp.

 

[hockenbery]

Even though these big bowls have a wall thickness that is slightly over one inch, they can be much more challenging to turn than a small thin walled bowl. As Leo said, the lathe speed has to be slow because the centrifugal force at the rim can cause a lot of force pushing the shape out of round and this can lead to a lot of vibrating so very light cuts are necessary as well as keeping your tools very sharp.

Getting a nice curve and good surface on an 18" bowl is much harder than getting a nice curve and surface on a 12" bowl. A 24" bowl much more difficult than an 18.
I find 10" bowls about the easiest size. Small bowls get harder to get a nice curve.
A decent 4" bowl is harder to make than a 10" bowl

 

[Bill Boehme]

I haven't noticed any difficulty with the exterior curve, but the interior curve gives me heck. I like to be able to move my hand from rim to rim without feeling any irregularities such as a bump or a change in curvature, but not being able to see what I can feel is sort of like being blindfolded.

 

[odie]

I find 10" bowls about the easiest size. Small bowls get harder to get a nice curve.
A decent 4" bowl is harder to make than a 10" bowl

Yeah, I hear ya, Al.....

I will not do anything less than about 5 1/2" diameter bowl (Approximately a 6" bowl blank), unless it's an exceptional piece of wood. Even then, I'd say anything between about 8"-12" takes about the same amount of time and effort to produce......no difference in difficulty, or time/effort to complete. The difficulty progressively gets more time consuming as the diameter increases from there. This makes it hard to price bowls in the 8"-12" range, because you can't take into consideration what time and expense you've invested, as the only considerations. All a potential buyer sees is one is bigger than the other, so the final price needs to have that influence in the sales price.

ko

 

[odie]

I haven't noticed any difficulty with the exterior curve, but the interior curve gives me heck. I like to be able to move my hand from rim to rim without feeling any irregularities such as a bump or a change in curvature, but not being able to see what I can feel is sort of like being blindfolded.

Hi Bill.......

It's true.....as the bowl spins, it's very difficult to determine exactly where irregularities in the interior profile are located. One thing I've been using to pinpoint a discrepancy in the shape of the interior, is to use a laser. That way, I know exactly what spot to concentrate on as the piece is spinning.....

ko

 

[Leo Van Der Loo]

Hi Bill.......

It's true.....as the bowl spins, it's very difficult to determine exactly where irregularities in the interior profile are located. One thing I've been using to pinpoint a discrepancy in the shape of the interior, is to use a laser. That way, I know exactly what spot to concentrate on as the piece is spinning.....

ko
View attachment 22335

Feeling a ridge as the bowl sits still is easy, what I usual do is take a pencil and scribe an ark where the ridge top is, you can see that when it turns, even marking the width helps in that way, feel and hold the pencil tip there and start stop the lathe and check that you marked the right location, works for me

 

[hockenbery]

I haven't noticed any difficulty with the exterior curve, but the interior curve gives me heck. I like to be able to move my hand from rim to rim without feeling any irregularities such as a bump or a change in curvature, but not being able to see what I can feel is sort of like being blindfolded.

Seeing the outside curve is easy but any flats in the curve are easy to see on a big bowl.

I can't see the inside curve as well and little bumps get lost visually.
Keeping the body moving is the biggest help in getting the curves.
The shear cut allows the tool handle to be in to my side.
Still little bumps pop up when.
I too like to feel for the bumps. I can usually find the bump by turning where I felt it.
With a little luck I can cut the bumps off using the the shear cut. starting before the bump the cut is not removing wood until the cutting edge engages the front edge of the bump and it stops cutting when it comes out out the back edge of the bump along the curve.
Then take a light cut across the whole surface.

I used to use chalk to mark the bumps easy to seemand it cleans off drynwood with compressed air.

 

[Dean Center]

One additional thought on sizes. The biggest chain sawed green blank I've been able to get to spin on my Powermatic is about 19". The rough blank from that starting point ends up about 17.5". When I return that size blank, at least with our local fresh woods, I end up with about a 15" or 15.5" finished bowl. (Now that I've figured out how to rig a 'third leg' for the band saw table, in the future, I'm going to use my circle cutting jig and make a nice, easily worked and highly spinnable 18" blank. Too much fighting with and chiseling on a 19" blank with corners. I expect to end up with the same 15" bowl at a lower Advil burden)

 

[Bill Boehme]

I like the laser idea that Odie showed. I have used pencil marks like Leo suggested, but on an 18" bowl, it takes a lot of pencil to still be visible when the piece is spinning.

I'm at the point of getting nervous because I like the current thickness and this box elder wants to tear out end grain if I just look at it wrong. If I go any thinner this thing is going to ring like a bell. I'm thinking of making a cardboard template for the inside curvature to gauge where the high spots are.

 

[Gretch Flo]

Like Al, I use chalk (white), Gretch

 

[Leo Van Der Loo]

I like the laser idea that Odie showed. I have used pencil marks like Leo suggested, but on an 18" bowl, it takes a lot of pencil to still be visible when the piece is spinning.

I'm at the point of getting nervous because I like the current thickness and this box elder wants to tear out end grain if I just look at it wrong. If I go any thinner this thing is going to ring like a bell. I'm thinking of making a cardboard template for the inside curvature to gauge where the high spots are.

Pencils are pretty cheap around here Bill , there must be a couple dozen in the shop, If I can find them, they like to hide on me

 

[Leo Van Der Loo]

I like the laser idea that Odie showed. I have used pencil marks like Leo suggested, but on an 18" bowl, it takes a lot of pencil to still be visible when the piece is spinning.

I'm at the point of getting nervous because I like the current thickness and this box elder wants to tear out end grain if I just look at it wrong. If I go any thinner this thing is going to ring like a bell. I'm thinking of making a cardboard template for the inside curvature to gauge where the high spots are.

You certainly can go thinner than that 1” thick wall Bill with no problems on a 16” bowl, I have one sitting here, rephrase that, Anny has one that is 16 inches with a 3/16” thick wall, and a 28” bowl with a ⅜” wall, mind you they are hard Maple, but still the large bowls are rough turned to about a 1” wall and when returned they do get at least ⅛” thinner on both sides (in and out) so ¾” would be the thickest and probably closer to ⅝”

 

[olaf Vogel]

Hi Bill.......

It's true.....as the bowl spins, it's very difficult to determine exactly where irregularities in the interior profile are located. One thing I've been using to pinpoint a discrepancy in the shape of the interior, is to use a laser. That way, I know exactly what spot to concentrate on as the piece is spinning.....

ko
View attachment 22335

Simple, cheap and smart! Like all the best ideas.

 

[Paul M. Kaplowitz]

I regularly turn 20-24" bowls on my VB36. I have turned several 30" ones. I sell my bowls at the Charleston(SC) farmers market and find the big ones sell at the rate of 2 or 3 per market. The Charleston Farmers market was rated #3 in the country behind Portland,OR and Baltimore,MD. We get 5,000+ people coming through.

 

[Esteban Churin]

Leo, the bowl you are holding in the photo above is great!

 

[Bill Boehme]

Success! I had to resort to the 80 grit gouge to take care of some end grain tear out on the interior of the bowl, but I wound up with a smooth curve from rim to rim and I can't detect any bumps or dips or flat spots whatsoever. And, it's only a gnat's eyelash from being circular. Not too bad considering all of the sanding.

Next step is bleaching with hydrogen peroxide and sodium hydroxide mixture.

 

[Bill Boehme]

You certainly can go thinner than that 1” thick wall Bill with no problems on a 16” bowl, I have one sitting here, rephrase that, Anny has one that is 16 inches with a 3/16” thick wall, and a 28” bowl with a ⅜” wall, mind you they are hard Maple, but still the large bowls are rough turned to about a 1” wall and when returned they do get at least ⅛” thinner on both sides (in and out) so ¾” would be the thickest and probably closer to ⅝”......

I have been informed by management that I shall make no thin bowls. End of story.

I do turn thin when making basket illusion pieces. Those are scary thin because I can see light through them. That's OK as long as I can't read the newspaper through them.

 

[hockenbery]

I do turn thin when making basket illusion pieces. Those are scary thin because I can see light through them. That's OK as long as I can't read the newspaper through them.

I use a light to turn lighter woods thin
Bright yellow light -> GOOD
White light -> BAD

 

[odie]

I do some thin wall bowls that are intentional.........but, there is that occasional thin wall that is totally unplanned! :mad:

......like the Claro walnut bowl on my lathe right now. Final thickness is 1/8".....but, I intended to hit closer to 1/4". As you work on the interior to make a nice curve that becomes flat at the bottom, it just works out that way sometimes.

ko

 

[Raul McCai]

A (wonderful) neighbor surprised me with a huge "blank" which is about 25 inches square and 8 inches thick. Needless to say, very heavy... The largest blank I've ever used in my Powermatic 3220B was 15 inches. Now it is very tempting to try to go BIG. But how big? Wise wood turners out there, what is the largest size/weight I can mount on my lathe while operating safely and not damaging my beloved lathe?
Thank you.
Esteban

You mean 3520B?
I have the extension on my PM lathe. They make one for yours too. If not send me the blank and that'll solve your problem. Or you could get a truck disc brake from a junk yard and have a welder put a pole on it for a rest or - - - A poly bucket with concrete in it will do jam the steel pole in before the concrete sets up . For the pole you could use Oak or hickory or ash I wouldn't use maple unless it was laminated.

 

[Leo Van Der Loo]

I use a light to turn lighter woods thin
Bright yellow light -> GOOD
White light -> BAD

You mean like this ??

GOOD like this


and Bad like this

 

[Bill Boehme]

Here's my little 18" box elder (Manitoba Maple) bowl before bleaching.



And, here it is after bleaching. It's not completely dry yet so it will turn a bit whiter by the time it is dry.



Box elder is soft and I managed to put some small dings in the rim . Hopefully, they will steam out.