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Completing a rough-turned bowl

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Forum topic by kmetzger posted 10-05-2013 08:50 PM 1045 views 0 times favorited 15 replies Add to Favorites Watch
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kmetzger

78 posts in 513 days


10-05-2013 08:50 PM

Richard Raffan describes a method for mounting rough-turned bowl blanks on p. 172 of “Turning Wood.” He turns a step-jaw consisting of a shoulder inside the bowl and then mounts it on chuck jaws. I’d like to know if there are other simple methods of dealing with rough-turned bowls.

Kim

-- Kim, Ajijic, Mexico, http://tinyurl.com/7w5fm25


15 replies so far

View Arlin Eastman's profile

Arlin Eastman

2128 posts in 1257 days


#1 posted 10-05-2013 10:02 PM

Scroll chuck that I know of is the best because the foot might go out of round and you can grip it better with a chuck.

You can also use a faceplate and glue block to turn it. I use titebond orginial and wait for 24 hours before turning.

Hope it helps
Arlin

-- It is always the right time, to do the right thing.

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kmetzger

78 posts in 513 days


#2 posted 10-05-2013 10:16 PM

Thanks, Arlin. But what I’m mainly interested in is how to mount the bowl with the foot facing outwards.

-- Kim, Ajijic, Mexico, http://tinyurl.com/7w5fm25

View BalloonGuy's profile

BalloonGuy

93 posts in 619 days


#3 posted 10-05-2013 10:24 PM

Cole jaws or Longworth jaws are two that come to mind.

-- Tom Peterson, Omaha, NE

View Wildwood's profile

Wildwood

1118 posts in 830 days


#4 posted 10-05-2013 10:28 PM

Do know manufacturer in UK have stopped making the chuck Raffin uses in his Turning Wood book or video. Since not seen or read that book in many years hard to answer your question.

Today most people use 4-jaw scroll chucks to mount their bowls either with a tenon (contraction mode) or a recess (expansion mode) on bottom of the bowl.

To finish turn, sand and finish bottom of bowl can use larger jaws known as mega, jumbo, or cole jaws depending upon manufacture of your scroll chuck.

Can also use homemade donut, jumbo jaws or longworth chucks for that purpose. In addition, homemade jam chucks.

Of course can always use faceplates, screws, waste blocks, and glue to do same things do with a 4-jaw chuck.

This video will give you more up-to-date information
http://www.youtube.com/watch?feature=player_detailpage&v=aUXil-5dEeo

Nice site to visit for turning information is

http://www.woodturningonline.com

-- Bill

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Wildwood

1118 posts in 830 days


#5 posted 10-05-2013 10:39 PM

I have some old cracked blanks (WASTE BLOCKS) that turned a recess in to mount on my chuck, place some foam rubber over that and mount my bowl bring the tailstock up to hold bowl reverse turn, sand, and will remove a little nib left with a knife or chisel then complete sand and finish my bowl off the lathe.

I use an old 3/8” spindle gouge with very pointed tip to reach where bowl gouge cannot because live center in the way.

If a roughed out bowl blank will not fit my jam chucks (to oval), have no problem using my two prong drive center inside and live center outside to bring blank back so can ount in my chuck.

-- Bill

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ScrubPlane

187 posts in 891 days


#6 posted 10-05-2013 11:03 PM

One method I’ve used several times with success is to hot glue a piece of plywood to the ‘open end’ of the bowl and remount it with the face plate, true up the bottom and then remount in the chuck. Not saying it’s the best but it works for me…THANKS.

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lew

10100 posts in 2451 days


#7 posted 10-06-2013 04:04 PM

+1 on what Arlin said about the Longworth Chuck.

http://www.woodworkersguide.com/2010/10/17/how-to-make-a-longworth-chuck/

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

View Arlin Eastman's profile

Arlin Eastman

2128 posts in 1257 days


#8 posted 10-06-2013 08:07 PM

I use a face plate with a piece of wood just alittle bit shorter then the bottom of the inside of the bowl and then I use a 60* center and turn off anything I need.

When I am finish I just sand or use a chisel on the little stub that is left.

Arlin

-- It is always the right time, to do the right thing.

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Wildwood

1118 posts in 830 days


#9 posted 10-07-2013 11:22 AM

I have never made or used a longworth chuck.

Have made and used plenty of donut chucks for reverse turning. Only time brake out my assortment of donut chucks today is for bowls too oval to fit a jam chuck and get proper alignment. Donut chucks simple to make and probably safest way to reverse turn a bowl. Do not need tailstock support or glue, to hold your bowl.

http://www.nealaddy.org/node/8

I use jam chucks for both spindles and bowls. On spindles might need a wet paper towel to help hold on a birdhouse, box, vase, etc for reverse turning. On bowls use old piece of rug or foam rubber to keep from marring inside of bowl.

On spindle can get away without tail tock support at some point in my turning, sanding & finishing, but not on bowls.

Can use any wood you have to make a jam chuck. Size, get it as close as you can to support item to be turned. Padding over your jam chuck will keep from marring inside of a bowl. Tailstock support a must for alignment & safety. On spindles padding not as important as not forcing your piece onto your jam chuck.

https://www.youtube.com/watch?v=8Sml3b2x8EQ

-- Bill

View JTJr's profile

JTJr

11 posts in 1370 days


#10 posted 10-26-2013 03:53 AM

Kim, I have that book and his video. He is doing the second turning of the rough blank, and first remounted using the tenon to turn a shoulder on the rough interior of the bowl where he intends to grip it with a chuck to finish the exterior of the bowl. If you don’t have wide enough jaws, you could turn a jam chuck to fit into your jaws/faceplate and use the tail stock to support the bowl while finishing the exterior. You’ll have to work around a nubbin where the tailstock center resides, and take it off with a chisel if you don’t trust the jam chuck to hold the bowl for the last little cut to remove the nubbin.

The bowl foot is turned to have a rebate as close to a perfect fit for the chuck jaws for gripping the bowl to finish the interior by expanding the jaws into the finished foot. Raffan uses techniques that will disguise the jaw marks that would otherwise be detrimental to the finish, and his choice of finish doesn’t show marks as much as others might. In order to create that rebate to grip the foot with the jaws in expansion mode, you’ll have to use a scraper that will let you work around the tailstock to size the rebate correctly, since the jam chuck requires the tailstock support. You would then use a longworth, donut chuck, etc to do a final finish on the foot after finish turning the interior, or finish off the lathe.

Raffan is using the chuck jaws to grip on the unfinished interior to gain full access to the exterior for all of his final finishing, including finishing the foot before reversing the bowl to do the interior. If you have to use a jam chuck, then you don’t have full access to finish the exterior, and have to deal with the tailstock in the way.

Raffan must be extremely careful to avoid catches when doing the interior, because he’s talking about a rebate on the foot of only 1/8 ” deep. It should almost match the diameter of the chuck jaws, and he is using dovetails to ensure the full engagement of the chuck jaws expanding into the rebate. This also minimizes marks that would be made if the rebate was a sloppy fit, because the jaws would not be gripping with full contact in the rebate.

You will note that not many turners are willing to trust their skills enough, or trust the small rebate enough to do the final finishing of the interior of the rough turned bowl using Raffan’s technique because a major catch would probably throw the bowl. They would rather have a tenon to grip tightly, finish the interior, and then remount to finish the foot using techniques that others have described earlier in this thread. Nothing wrong there, I’m finally beginning to feel comfortable sticking big hunks of steel into the interior of a bowl, where a year ago I couldn’t have said that.

I believe Bob Hamilton has a video on using a jam chuck to gain full access to finish turning the profile of a rough turned bowl. The longworth chuck or donut chuck do not allow full access for final finishing of the exterior and are used for the final finishing of the foot. I think Bob may have used a vacuum chuck for his final pass at the foot.

Mind you that I haven’t tried Raffan’s technique myself, but am trying to answer your question in light of what Raffan describes in the book. I have however, expanded my jaw selection because I liked what I read, and want to try it myself. Having unrestricted access to the exterior for finishing the rough turned bowl would make life so much easier than banging into the tailstock. I have been using jam chucks and tail stock support on the few blanks that I have rough turned and left to dry. I definitely need more wood!!

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kmetzger

78 posts in 513 days


#11 posted 11-01-2013 11:21 PM

Thank you, JT, for your thorough discussion. I think you’re right about the possibility of catches using Raffan’s technique. My skills are far from adequate, so I’ll try the jam chuck method.

-- Kim, Ajijic, Mexico, http://tinyurl.com/7w5fm25

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Nubsnstubs

231 posts in 426 days


#12 posted 11-02-2013 06:06 PM

Kim, this is what I use to finish all my bowls. I invented this type of live center with roller blade wheels that support the work after the tenon is removed. I’ve probably done about 150 forms, and only lost 2. Those were at the beginning when I first was experimenting with it. Now, as far as I’m concerned, it’s settled science… Proper pressure, speed and a good sharp tool, and you’ll never have another failure at the tenon removal stage, and you can do all the clean up and sanding while still between centers without any interference from the live center….. ........ Jerry (in Tucson)

-- Jerry (in Tucson)

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Nubsnstubs

231 posts in 426 days


#13 posted 11-02-2013 06:14 PM

Another picture and more explanation. The live center body is threaded, and the wheel ring is also threaded. There is about 1” of adjustment on the threads. The wheel struts also have 1’ of adjustment, allowing over 2’ of adjustment, for those forms with pedestals, or large feet. both pictures posted show the wheels splayed out in a 3 3/4” width between wheels, but the ring can be remove and reversed to close up the wheel width to under 2”.... ........ Jerry (in Tucson)

-- Jerry (in Tucson)

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Nubsnstubs

231 posts in 426 days


#14 posted 11-02-2013 06:24 PM

These 3 pictures show my live center in use. The first shows the begining of the tenon removal, secong shows the very little nub left, and the last picture shows the completely finished bottom…... Jerry (in Tucson)

-- Jerry (in Tucson)

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Nubsnstubs

231 posts in 426 days


#15 posted 11-02-2013 06:44 PM

what is not explained in the above 3 post is I’m also using my Chuck Plate, another of my woodturning inventions, to support the form with a plug turned to fit most of the inside contour. I could have made the jamb chuck” plate” fit around the rim, but I chose this one to go in the inside. Since I started using these 2 tools I made, I’ve only lost 2 forms due to inexperience…


This particular Chuck Plate is dedicated to tenon removals only. It’s used with an MDF plate with 5 holes drilled that match up to the 4 outside screws that act as the driver. The center screw just locates center of the plate.

After mounting the plate onto the Chuck plate, measure your rim ID/OD, and cut a groove that diameter. Mount your form between centers and remove the tenon if you had the live center posted above. It’s starting to look to me that I just hijacked this thread. Sorry. I’ll post more pictures later if anyone is interested in my gizmos or gadgets…....... Jerry (in Tucson)

-- Jerry (in Tucson)

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