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Twice Turning Using 40/40 Grind

Joined
Sep 10, 2021
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Location
Collingwood, ON
Hi All,

Fairly new turner here, grinders and small boxes mostly, but I've been putting in some serious time with bowls also. I am using the twice-turned method and have been having reasonable success, but I recently made the decision to switch from my swept-back grind to the 40/40 grind and I'm wondering if anyone has tips/tricks/secrets as to how to get a clean pass on the outside of bowl on the second turning...

Once the bowl has dried and come out of my kiln, I friction-mount it using my Oneway vacuum chuck as a drive (just using the friction of the neoprene, not engaging the vacuum), and the tailstock for support. I would normally true the original tenon and then complete the outside of the bowl before remounting it with the trued-up tenon to finish the inside. Last step is to use the vacuum chuck to finish the bottom. The issue now is that I can't get the 40/40 to swing far enough to make the finish cut from the bottom of the bowl because of the tailstock. All of the videos I've watched show how to make the cut when the bowl is mounted from the rim - either by a tenon prior to hollowing, or by a jamb chuck after, using a lot of real estate over/beyond the lathe bed.

Should I consider using my bottom bowl gouge to get the first part of the curve on the outside of the bottom and then switch to the 40/40? Or is there another alternative I'm just not considering? I suppose I could try to mount the warped original tenon first and true the inside, but that forces me to use a custom jamb chuck to turn the outside for every bowl (not to mention the risk of a sloppy grip on a bad tenon) - something I'd like to avoid if at all possible. I could also use the hot-melt glue block, but that also adds an additional step and every step I can avoid is more time saved and more money in my pocket. I could true the tenon first, then remount the bowl to do the inside, and then jamb chuck it, but that also adds steps as well as the risk of not running true between mountings.

Any ideas/suggestions are welcome, and if anyone can point me to a video that might show this issue - please do! Although I'm pretty sure I've been to the end of the internet and watched every turning video out there... just ask my wife!!

Thanks for your time!

John
 

hockenbery

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I don’t use the 40/40 on twice tuned bowls largely because of the fun you are having. The 40/40 is terrific on platters once turned from dry wood.

One solution is to jamb/friction chuck with the tailstock tailstock centered in the tenon.
1 Balance the rims to the same distance to the headstock By shifting on the friction drive (open bare chuck jaws for me)
2 true the rims to improve the weight balance
3. True the tenon
4. Turn a recess in the bottom center just need the recess ring to be close to the perfect circle of your jaws.
5. Mount on the recess
6. You can now turn the outside using the recess to hold
7 check the tenon for true
Mount in the chuck and hollow.


PS - a pull cut with the Ellsworth grind will match or outperform the 40/40 on the outside of the bowl.
The 40/40 is superior in the push cut because you are using a 40 degree bevel vs 60 on the nose of the Ellsworth or
45 degrees on the slicing sweet spot most turners use on the push cut with an Ellsworth grind.
The pull cut uses a 25-30 wing bevel on the Ellsworth which gives a nicer surface than a 40 degree.
 
Last edited:
Joined
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Wrentham, MA
I'm in a similar position. One thing I'm keen to try is something I saw from Richard Raffan - mount the bowl between a chuck and tail stock. True up the tenon then reverse, mounting the tenon in the chuck. Turn a small recess inside the bowl, about a 1/16" deep just larger than the closed diameter of the jaws. Reverse with the jaws expanding into this recess. This provides a good grip with dovetail jaws and total access to the outside. Turn outside, then reverse again to turn inside.
 
Joined
Sep 10, 2021
Messages
17
Likes
10
Location
Collingwood, ON
I don’t use the 40/40 on twice tuned bowls largely because of the fun you are having. The 40/40 is terrific on platters once turned from dry wood.

One solution is to jamb/friction chuck with the tailstock tailstock centered in the tenon.
1 Balance the rims to the same distance to the headstock By shifting on the friction drive (open bare chuck jaws for me)
2 true the rims to improve the weight balance
3. True the tenon
4. Turn a recess in the bottom center just need the recess ring to be close to the perfect circle of your jaws.
5. Mount on the recess
6. You can now turn the outside using the recess to hold
7 check the tenon for true
Mount in the chuck and hollow.


PS - a pull cut with the Ellsworth grind will match or outperform the 40/40 on the outside of the bowl.
The 40/40 is superior in the push cut because you are using a 40 degree bevel vs 60 on the nose of the Ellsworth or
45 degrees on the slicing sweet spot most turners use on the push cut with an Ellsworth grind.
The pull cut uses a 25-30 wing bevel on the Ellsworth which gives a nicer surface than a 40 degree.
I may have to re-watch a few Ellsworth videos and work on my pull cut technique. I am excited to use the 40/40 for the initial turning though! Thanks for the input!
 
Joined
Sep 10, 2021
Messages
17
Likes
10
Location
Collingwood, ON
I'm in a similar position. One thing I'm keen to try is something I saw from Richard Raffan - mount the bowl between a chuck and tail stock. True up the tenon then reverse, mounting the tenon in the chuck. Turn a small recess inside the bowl, about a 1/16" deep just larger than the closed diameter of the jaws. Reverse with the jaws expanding into this recess. This provides a good grip with dovetail jaws and total access to the outside. Turn outside, then reverse again to turn inside.
I saw RR use this technique as well - thought it was quite brilliant. Only issue is I will definitely need larger jaws, as most of the bowls I do are in the 9-12" range and usually 4" or more deep, so it will be tough to get deep enough to set the jaws properly.
 

hockenbery

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I may have to re-watch a few Ellsworth videos and work on my pull cut technique. I am excited to use the 40/40 for the initial turning though! Thanks for the input!
The 40/40 works for lots of folks.
Using the recess inside the bowl I suggested is a proven method for returning the outside without a tailstock.
For deep bowls you might want to get some tower jaws or O’Donnell jaws.
 
Last edited:
Joined
Sep 10, 2021
Messages
17
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10
Location
Collingwood, ON
The 40/40 works for lots of folks.
Using the recess inside the bowl I suggested is a proven method for returning the outside without a tailstock.
For deep bowls you might want to get some tower jaws or O’Donnell jaws.
I will definitely have a look. I’ve been wanting to expand my chuck collection (haven’t we all??) to include larger dovetail jaws. Currently I only have the stock jaws that come with the Stronghold and Talon chucks from Oneway, which have served me well, but I know there are more appropriate setups. Thanks again for your valuable input!
 
Joined
Sep 10, 2021
Messages
17
Likes
10
Location
Collingwood, ON
The 40/40 works for lots of folks.
Using the recess inside the bowl I suggested is a proven method for returning the outside without a tailstock.
For deep bowls you might want to get some tower jaws or O’Donnell jaws.
I will definitely have a look. I’ve been wanting to expand my chuck collection (haven’t we all??) to include larger dovetail jaws. Currently I only have the stock jaws that come with the Stronghold and Talon chucks from Oneway, which have served me well, but I know there are more appropriate setups. Thanks again for your valuable input
Am I missing something? Why not just turn on the vacuum, move the tail stock and use the gouge you like?
Hi Dean. With the bowl being warped from drying there isn’t a consistent enough interface with the chuck to get a seal to pull the vacuum. At least not with what I’ve tried so far. Have you had success this way?
 
Joined
Feb 11, 2022
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Fort Bragg, CA
The process Kirk is mentioning above works great and doesn’t have to be complicated. Grab the warped original tenon in your chuck. Most times you won’t need to true it up, just use as is. Turn a fresh recess inside, no need to true up anything else inside. Flip the bowl around, mount on the recess, and you’re solid and ready to go.
 
Joined
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Location
Lummi Island, WA
The process Kirk is mentioning above works great and doesn’t have to be complicated. Grab the warped original tenon in your chuck. Most times you won’t need to true it up, just use as is. Turn a fresh recess inside, no need to true up anything else inside. Flip the bowl around, mount on the recess, and you’re solid and ready to go.
This is my process - the tenon doesn’t have to be true to get the recess inside turned. I use a recess as close to the rim as possible so the largest tower jaws I have will provide enough clearance so the chuck key works. That recess does not need to be close to the min size your jaws will expand into - I often size them for the maximum diameter of my largest jaws. Works just fine.
 

hockenbery

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Currently I only have the stock jaws that come with the Stronghold and Talon chucks from Oneway, which have served me well, but I know there are more appropriate setups

These will work for open bowls. May we’ll work for all the bowls you turn.
But some bowl shapes won’t work because the key can’t be used or the chuck body hits the side walls.

Tower jaws give you another inch of height ONEWAY has them for the stronghold and talon.

These will work on more bowl shapes than the stock jaws but won’t work on all bowl shapes either.
CAEE9F24-D2EF-4550-97C7-B0F4F70A849C.jpeg
 
Joined
Jan 3, 2012
Messages
381
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315
Location
New City, NY
Hi All,

Fairly new turner here, grinders and small boxes mostly, but I've been putting in some serious time with bowls also. I am using the twice-turned method and have been having reasonable success, but I recently made the decision to switch from my swept-back grind to the 40/40 grind and I'm wondering if anyone has tips/tricks/secrets as to how to get a clean pass on the outside of bowl on the second turning...

Once the bowl has dried and come out of my kiln, I friction-mount it using my Oneway vacuum chuck as a drive (just using the friction of the neoprene, not engaging the vacuum), and the tailstock for support. I would normally true the original tenon and then complete the outside of the bowl before remounting it with the trued-up tenon to finish the inside. Last step is to use the vacuum chuck to finish the bottom. The issue now is that I can't get the 40/40 to swing far enough to make the finish cut from the bottom of the bowl because of the tailstock. All of the videos I've watched show how to make the cut when the bowl is mounted from the rim - either by a tenon prior to hollowing, or by a jamb chuck after, using a lot of real estate over/beyond the lathe bed.

Should I consider using my bottom bowl gouge to get the first part of the curve on the outside of the bottom and then switch to the 40/40? Or is there another alternative I'm just not considering? I suppose I could try to mount the warped original tenon first and true the inside, but that forces me to use a custom jamb chuck to turn the outside for every bowl (not to mention the risk of a sloppy grip on a bad tenon) - something I'd like to avoid if at all possible. I could also use the hot-melt glue block, but that also adds an additional step and every step I can avoid is more time saved and more money in my pocket. I could true the tenon first, then remount the bowl to do the inside, and then jamb chuck it, but that also adds steps as well as the risk of not running true between mountings.

Any ideas/suggestions are welcome, and if anyone can point me to a video that might show this issue - please do! Although I'm pretty sure I've been to the end of the internet and watched every turning video out there... just ask my wife!!

Thanks for your time!

John
I have a few comments but let me answer the last of your requests first:
The holding methods with the step-by-step process of re-chucking a twice-turned bowl were recorded in a Stuart Batty presentation in The AAW 2021 Virtual Symposium. I think it is still available for rental. I would call AAW to see if viewing is still available. I reviewed my notes on this video and I recall The process began a little more than halfway thru the presentation.

Here are the steps from the video:
1. The now seasoned rough-turned bowl was held by a live center in the tailstock by using a center mark made previously in the wet turning. It was held in the tailstock with possibly a jam chuck of some sort on the headstock. Batty trued up the tenon only. He did not true up the outside of the bowl at this stage.

2. The bowl was then held in the chuck by the newly trued-up tenon and he made a shallow recess tenon on the inside of the bowl so that it could be gripped in expansion mode by a chuck with at least 4-inch jaws... maybe bigger. For the Oneway stronghold chuck perhaps the number three jaws may work here. (Batty used Vicmarc dovetail jaws.)

3. With the Bowl being held this way, the tailstock is not needed so he proceeded to true up and finalize the outer shape of the bowl using his 40-40 push cut.

4. He remounted the bowl again so that the inside is hollowed true with his 40-40, bottom of the bowl gauge, and NRS. (The recess tenon cut in step2 was turned away in this step)

5. In the last step of the twice-mounted bowl process, he remounted yet again by fitting the bowl on a jam chuck masking and taping the rim to the jam chuck. He proceeded to finish to the final thickness and convert the tenon to the finalized bowl bottom.

I am not going to say that this is a lot of extra work, because I do realize that Batty is a production-turner and that he is probably able to produce more bowls in a day by reducing his sanding time. If implemented properly the 40-40 will produce almost sandless finishes. However, not everyone can achieve this economy of scale if the overhead includes all this re-chucking. They just may not want to go through all the trouble of a special setup so that they can execute that perfect 40-40 push cut. For me, it does not matter how long it takes for me to finish. No one has asked me how long did it take me to make that bowl? I don't sell them either.
I used the Ellsworth gouge solely for about 18 years and sandpaper.
Now, that I've learned how to sharpen and use the 40-40, I have increased my understanding and awareness of how tools cut on a lathe. I find that after I produced a beautiful finish off the tool, I have become irrationally addicted to using the gouge. However, both the 40-40 and Ellsworth grind have their advantages in certain situations. So I use both.

So should you use your "bottom of the bowl" gouge on the outside of the bowl? My answer: Would I recommend using a roughing gouge on a bowl? So under the Looks like a duck, sounds like a duck rule I probably would use myself it but I wouldn't recommend it. Yet I have no problem recommending the Ellsworth gouge.

Just in case you have not viewed this you tube:
View: https://youtu.be/N7BjRcSDurM
 
Last edited:
Joined
Sep 10, 2021
Messages
17
Likes
10
Location
Collingwood, ON
The process Kirk is mentioning above works great and doesn’t have to be complicated. Grab the warped original tenon in your chuck. Most times you won’t need to true it up, just use as is. Turn a fresh recess inside, no need to true up anything else inside. Flip the bowl around, mount on the recess, and you’re solid and ready to go.
I’m excited to give it a try once I get the appropriate jaws. And who am I kidding - another chuck to go with them so I don’t have to bother switching them back and forth!
 
Joined
Sep 10, 2021
Messages
17
Likes
10
Location
Collingwood, ON
These will work for open bowls. May we’ll work for all the bowls you turn.
But some bowl shapes won’t work because the key can’t be used or the chuck body hits the side walls.

Tower jaws give you another inch of height ONEWAY has them for the stronghold and talon.

These will work on more bowl shapes than the stock jaws but won’t work on all bowl shapes either.
View attachment 49608
Yep - I’ve studied that chart many times - now I just need to pull the trigger!
 
Joined
Sep 10, 2021
Messages
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Likes
10
Location
Collingwood, ON
I have a few comments but let me answer the last of your requests first:
The holding methods with the step-by-step process of re-chucking a twice-turned bowl were recorded in a Stuart Batty presentation in The AAW 2021 Virtual Symposium. I think it is still available for rental. I would call AAW to see if viewing is still available. I reviewed my notes on this video and I recall The process began a little more than halfway thru the presentation.

Here are the steps from the video:
1. The now seasoned rough-turned bowl was held by a live center in the tailstock by using a center mark made previously in the wet turning. It was held in the tailstock with possibly a jam chuck of some sort on the headstock. Batty trued up the tenon only. He did not true up the outside of the bowl at this stage.

2. The bowl was then held in the chuck by the newly trued-up tenon and he made a shallow recess tenon on the inside of the bowl so that it could be gripped in expansion mode by a chuck with at least 4-inch jaws... maybe bigger. For the Oneway stronghold chuck perhaps the number three jaws may work here. (Batty used Vicmarc dovetail jaws.)

3. With the Bowl being held this way, the tailstock is not needed so he proceeded to true up and finalize the outer shape of the bowl using his 40-40 push cut.

4. He remounted the bowl again so that the inside is hollowed true with his 40-40, bottom of the bowl gauge, and NRS. (The recess tenon cut in step2 was turned away in this step)

5. In the last step of the twice-mounted bowl process, he remounted yet again by fitting the bowl on a jam chuck masking and taping the rim to the jam chuck. He proceeded to finish to the final thickness and convert the tenon to the finalized bowl bottom.

I am not going to say that this is a lot of extra work, because I do realize that Batty is a production-turner and that he is probably able to produce more bowls in a day by reducing his sanding time. If implemented properly the 40-40 will produce almost sandless finishes. However, not everyone can achieve this economy of scale if the overhead includes all this re-chucking. They just may not want to go through all the trouble of a special setup so that they can execute that perfect 40-40 push cut. For me, it does not matter how long it takes for me to finish. No one has asked me how long did it take me to make that bowl? I don't sell them either.
I used the Ellsworth gouge solely for about 18 years and sandpaper.
Now, that I've learned how to sharpen and use the 40-40, I have increased my understanding and awareness of how tools cut on a lathe. I find that after I produced a beautiful finish off the tool, I have become irrationally addicted to using the gouge. However, both the 40-40 and Ellsworth grind have their advantages in certain situations. So I use both.

So should you use your "bottom of the bowl" gouge on the outside of the bowl? My answer: Would I recommend using a roughing gouge on a bowl? So under the Looks like a duck, sounds like a duck rule I probably would use myself it but I wouldn't recommend it. Yet I have no problem recommending the Ellsworth gouge.

Just in case you have not viewed this you tube:
View: https://youtu.be/N7BjRcSDurM
Wow - thanks for your time Dennis! I have watched all of the SB YouTube videos I can find, but I don’t think I saw the AAW video. It is these videos that made me make the jump to the 40/40. I’m hoping the larger jaws and inside recess method will work, as I don’t like the idea of making large jamb chucks for each bowl (I realize one jamb chuck would get many uses, but still - I don’t have the room for storing multiple chucks to cover all the sizes of bowls). Nevertheless - I am very appreciative of everyone’s advice and I will definitely take all of it into consideration as I develop my methods going forward. Thanks again for your time (and everyone else who replied!!)
 
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I haven't used a swept back gouge in years, and that started when I learned the 40/40 grind. I once turn all of my bowls. If I did do the twice turned bowls, I think I would just true up the tenon, then reverse the bowl and use pull cuts to finish up the outside, and standard push cuts for going down the inside to the transition area, then switch to a BOB (bottom of bowl) tool. With the pull cut on the outside, you can use that to true up the first inch or two, then switch to a BOB tool for finishing the outside of the bowl. You can angle the handle better so you are not running into the headstock. You might be able to do the same thing with the bowl in position for truing up the tenon. Not sure.

robo hippy
 
Joined
Sep 10, 2021
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I haven't used a swept back gouge in years, and that started when I learned the 40/40 grind. I once turn all of my bowls. If I did do the twice turned bowls, I think I would just true up the tenon, then reverse the bowl and use pull cuts to finish up the outside, and standard push cuts for going down the inside to the transition area, then switch to a BOB (bottom of bowl) tool. With the pull cut on the outside, you can use that to true up the first inch or two, then switch to a BOB tool for finishing the outside of the bowl. You can angle the handle better so you are not running into the headstock. You might be able to do the same thing with the bowl in position for truing up the tenon. Not sure.

robo hippy
Sweet! Thanks for the input - I think I will try just about everything suggested here and see what works best for me. It’s amazing how much time and effort everyone has put into their responses - I always check the forum when I have questions, thus I knew you were a 40/40 man and a one-timer, but this is the first big question I’ve asked and the response is awesome! Thank you so much!
 
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Hi Dean. With the bowl being warped from drying there isn’t a consistent enough interface with the chuck to get a seal to pull the vacuum. At least not with what I’ve tried so far. Have you had success this way?
That explains it. And you're right, you can't always just turn around a warped bowl. John Giem wrote an article for the AAW journal on how to mount irregular shapes on a vacuum, but that's too big a tangent to get into at this point. Carry on.
 
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