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View Full Version : Turning the bottom of the bowl? Help please



chitswood
3rd March 2006, 02:59 PM
I have been turning bowls for a few years now, but I cant seem to find a very good way to sand and finish the bottom of the bowl the way I would like to. How is the bottom of the bowl sanded? Is there some tool or technique I dont know?

Also, I have seen signatures on the bottom of bowls, is this just done with a pen? I suspect it was burnt on?:confused: :confused:
Thanks in advance for the help -Darick

ribot
3rd March 2006, 04:15 PM
Not trying to be smart, but which bottom do you mean? Inside or outside bottom.

chitswood
3rd March 2006, 04:20 PM
The outside.

DavidG
3rd March 2006, 04:27 PM
Two ways for a start.
1 -- Finish the bottom before starting on the inside. The whole outside is done first. This leaves a disguised holding point so you need a good chuck to hold the bowl with out leaving much mark.

2 -- As you do now then, when the inside is finished turn the bowl around and hold with either bowl jaws or vacuum chuck (or a jam fit) whilst you finish the bottom.

The writing can be done with a pen (before finish) or burnt on after finish.

ribot
3rd March 2006, 04:39 PM
What DavidG said.
I usually use the friction fit/jam fit.
The key is to finish before you flip it round.
Whilst on the subject and not trying to highjack the thread, how do you stop the stain which occurs when I use a chuck(nova) to hold the bowl by the base.(black stain where jaws contact wood, usually green/Red gum.)

DavidG
3rd March 2006, 06:33 PM
(black stain where jaws contact wood, usually green/Red gum.)
Wet wood problem. Use sheet plastic to prevent wet wood to metal contact. Bit of garbage bag.
Also do not close too tight. Just enough to hold.

Skew ChiDAMN!!
4th March 2006, 12:48 AM
For bowls where the rim's the widest point, I use a set of home-made cole jaws. When the widest point is within some 30mm of the top of the bowl, I use the same cole jaws with longer door-stop rubbers. :) In other cases I'll use either a smaller set in expansion mode or a padded jam-chuck that fits inside the bowl along with a dowel in a jacob's chuck for the tailstock.

Other options would be a vacuum chuck, which is fairly simple to make, or a "donut chuck" which is a ring that's attached to the faceplate with threaded rods & wing-nuts, clamping the bowl in-between. I dislike the last: had more failures than successes with 'em. :o

Personally I like to turn the base last, to remove all signs of the mount and decorate the base... but this can lead to BIG headaches if I have to remount the bowl later for any reason.

chitswood
4th March 2006, 01:32 AM
Two ways for a start.
1 -- Finish the bottom before starting on the inside. The whole outside is done first. This leaves a disguised holding point so you need a good chuck to hold the bowl with out leaving much mark.

2 -- As you do now then, when the inside is finished turn the bowl around and hold with either bowl jaws or vacuum chuck (or a jam fit) whilst you finish the bottom.

The writing can be done with a pen (before finish) or burnt on after finish.


I have tried the first choice and it doesn't work too well with the chuck I have, There will be teeth marks no matter what I do.
The other problem is I have heard of something similar to the vacuum chuck, but I have seen none of these chucks and don't know how to get one. Thanks -Darick

Skew ChiDAMN!!
4th March 2006, 02:46 AM
Cole jaws are simple to make... this 'un just uses door-stoppers mounted upside-down. Although 'tis made from MDF, I really don't recommend it... ply is far, far better. I just didn't have any to hand when I knocked it together. [shrug] In this 'un the door-stoppers are just screwed into the MDF at the appropriate position, but normally I'd drill through and use small bolts & wing-nuts.

Hickory
4th March 2006, 03:13 AM
There are a number of different ways to turn the bottoms, There is the cole jaws as previously discribed, There is a vacuum chuck that holds the plate or bowl and a rig jig that holds the bowl between two discs with on having the center cut out to expose the bottom, Here is a link to a fellow's discription of how to make one.

http://www.enter.net/~ultradad/bowljig.html

As for the signature: I use an Extra fine Sharpie (felt tip pen) After several coats of finish but before the last coat, I write my name & date. Not on raw wood as it will bleed and make a fuzzy image. I use Wipe-on Polyurethane a great deal and I find that after a few coats, I scuff the bottom and Sign, then add one more coat.

chitswood
4th March 2006, 09:49 AM
:D :D thanks everyone, this is real helpful.

Cliff Rogers
4th March 2006, 12:08 PM
..., Here is a link to a fellow's discription of how to make one.

http://www.enter.net/~ultradad/bowljig.html

....
Similar jig described on page 60 of the March issue of Woodturning mag.
The author used it to turn a 'triplet' of bowls in the one piece of fence post.

TTIT
5th March 2006, 01:16 AM
My preferred method is the Longworth chuck - like 'em so much I made two! Trick is to make them so they fit on to your normal chuck/jaws so theres no need to muck around swapping chucks. I've made mine from perspex but the originals were made from ply. Very easy to make and very easy to use - worth a shot.:D

hughie
5th March 2006, 03:31 PM
''I've made mine from perspex but the originals were made from ply''

TTIT,
I have a sheet of 6mm polycarbonate that I intend to use for a Longworth chuck. But I see that your chuck looks like its made of thicker stuff. How thick is the material you used?

hughie

Caveman
6th March 2006, 03:22 AM
Here's a compression/doughnut chuck I made. Pretty basic - but I find it doesn't allow for the best of access to the bottom of the bowl.

Had not heard of the Longworth chuck - looks great and very friendly to use. Nice pics TTIT - might have to try one of them methinks. Presumambly works just as well in compression mode as opposed to expanding as in the pics???

TTIT
6th March 2006, 09:02 AM
Hughie - I originally used 6mm also and it worked fine but just had a little more flex than I wanted. When I went to make the smaller unit (pictured in post) I managed to score some 12mm offcuts which was just right for the back disk.

Caveman - I found the Longworth on the net - a woodie from Newcastle by the name of Longworth invented it and put it out for all to use - so easy to make nobody bothered with patents etc. Poor bloke passed away before finishing his 2 part article on making them but his club did so and put it on the net - can't find the link just now....

chitswood
6th March 2006, 12:34 PM
Thanks everyone! this is been very helpful. I have a lot of Ideas now. -Darick

hughie
6th March 2006, 01:25 PM
TTIT,
I figured my 6mm would be a bit thin for the back. Thanks for the info.
I found the link to the Longworth chuck
http://www.fholder.com/Woodturning/lwc-wtm.htm
hughie

docusk
1st April 2007, 09:58 AM
Thanks for the link to the Longworth Chuck. I've just printed it our from the article and intend to make a start next week.
Thanks to all for the good tips on finishing the foot.

docusk

Bang goes my resolution not to cruise this site after midnight! Ah well, it's only a few minutes past so I'll go to bed, However, I noticed a good item......?
GO TO BED!!!

Bill Wyko
3rd April 2007, 09:21 AM
I screw chuck it from the front then turn the outside. Then I reverse chuck it to turn the inside.:2tsup:

madmix
28th April 2007, 09:37 PM
Thanks TTIT and Hughie,

After creating a segmented frizbee last week, I went in search
of a better chucking method, and came across this thread.
So finished making a longworth today and to test it out mounted
the offending frizbee. Well the bowl might not be salvageable, but it
definately stayed in place. What a marvelous and simple idea, and as
I allready had ply and mdf, only cost about $4 for bolts and rubbers.

cheers Mick

Stu in Tokyo
29th April 2007, 12:55 AM
I've not made a Longworth chuck, yet, but I have two Donut chucks that work well.

One trick I do with the donut chucks it I make about 6 round pieces of plywood all the same size, then I center them, and drill a hole through the very center of all six pieces. I then put a long bolt, or piece of threaded rod in there and tighten it up, I drill all six pieces with the 3 holes needed for the donut chuck's bolts, then I mark the edges of the six pieces so I can line them up again.

The first piece is then glued to a thick block that I have threaded to go on my lathe spindle. On the lathe, I start at nearly all the way out at the bolts, and cut a big hole, then I go down about an inch on the 5th piece, and so on so at the end, I have one piece is the backer board of the chuck, and I have 5 rings, or donuts, each has about an inch bigger hole in it, this way, I always seem to have right sized ring for whatever I'm turning the bottom of....

Some pics of some of my donut chucks.......

44921 44922 44923 44924 44925

grybeard
29th April 2007, 02:07 AM
Hi guys
I dont post on here very much but lurk and read the others quite a bit...lots of good info on here.
Anyway just thought i would put my 2 cents in here for this one ...
The method i use for bowl bottoms is really simple..I use a 6 inch sanding disc on the end of a jacobs chuck that i slide into the headstock with a #2 morse taper...this is the solid type not the one that requires a screw in the middle to hold the paper if you follow me...think its made by 3m.....I don't put any paper on it ..instead i use a paper towel to prevent any scratching ...set the bowl over the disc and bring up the tailstock to secure it against the disc.(may have to move it a couple times to get in center) turn on the lathe at lowest speed and your good to go ...all it leaves is a little nub that you can chip off with a chisel or sand off .
After I get the bottom sanded off b4 i take it off the disc I will usually take the edge of a parting tool and carve a couple of circles about 1/2 inch apart for a space to sign and date the piece and then use a "sharpie" pen to do this...apply the finish after I sign and date it.
just my 2 cents ..hope it helps.
Bob:D

robynmau
7th May 2007, 01:25 PM
Hi folks:D

I've used all of the above methods at different times, depending on what I was working on, but I also made a simple faceplate that I found on the internet years ago [haven't got the link anymore and so can't acknowledge the original suggester ... sorry] that I thought you might find useful.

The idea is to use some ply that is reasonably solid, attach a face plate and round it true and flatten off the face. You then glue some thin rubber onto the front. After the glue has dried, draw several circles across the face of the rubber to give you some idea of centre for your bowl.

Put your bowl top to the rubber and bring the tail stock to the bottom [you finish up with the hole from the drive in the base if only sanding]. Providing you put the bowl near to centre, it self centres once the piece starts rotating, without flying off.

Now you can turn down the bottom to only a small stub under the tailstock to cut away with a chisel after sanding or if you're keeping all the bottom you can sand all but the very middle.

Note: I have tried getting away from that tail stock driver mark by using covers but these have created their own problems so now I'm happy just to leave a little mark that I hand sand.

Hope this helps, if I haven't explained something properly, please ask and I'll try to explain more fully.

Cheers

Robynmau

rsser
7th May 2007, 03:22 PM
I'm a fan of vacuum chucks.

Like to live dangerously ... when in a forgetful moment turn the vac off without a hand on the bowl --> "multiple expletives deleted"!

(Why is it that with age-related forgetful moments what you miss is this kind of thing rather than another zero or two on your bank balance??)

TTIT
8th May 2007, 01:20 PM
I'm a fan of vacuum chucks.
I finished my set up just before Dad got crook and haven't really had a chance to try it (in anger) yet. Do you have a gauge on yours Ern and more importantly, do you use it???? :confuzzled:


Like to live dangerously ... when in a forgetful moment turn the vac off without a hand on the bowl --> "multiple expletives deleted"!I've been wondering about that type of thing or some part of the system springing a leak - I think it will take a while for me to trust it. :shrug:

Cliff Rogers
8th May 2007, 01:51 PM
vacuum chucks.... have you blokes posted anything about these elsewhere? :?

Should I do a search? :D

TTIT
8th May 2007, 02:03 PM
vacuum chucks.... have you blokes posted anything about these elsewhere? :?

Should I do a search? :DI haven't posted anything yet 'cos I haven't given it a proper run yet - just a little "Yep - it's sucks!" sort of testing so far. The vacuum side was easy enough, getting the right materials together for the chucks took a little longer but I learnt a lot along the way - did you know crapiata isn't airtight??? - I didn't and wasted a lot of time trying to work out what was wrong. When I get something mounted for bum finishing next I'll grab the camera.:U

Cliff Rogers
8th May 2007, 02:13 PM
I am now interested in vacuum chucks too.

I saw a couple of home made jobs at the Prosserpine Turnout a couple of years ago & I should have taken some notes & pics at the time.

They used MDF in some of their set ups.

rsser
8th May 2007, 02:54 PM
Can't remember whether I've posted on this one before.

Yep, mine is MDF a with neoprene sheet glued on and some rings marked in pen on it to aid centring. Vern, I just use a domestic vac cleaner with some leakage designed in (2 x 1/8" holes drilled in the 'cuff'; otherwise the motor overheats). It provides reasonable grip and setup is quick provided you leave a centre mark on the foot and line it up with the tailstock. It's only good for light cuts but of course you can bring the tailstock up for heavier cuts and cuts further away from the centre.

Though frankly if you already have a suitable Longworth I'm not sure the vac chuck will add anything much.

Happy to post a pic or two.

... Edit: pics of the old Vicmarc model attached. This had a cheap foam surface. (The copper pipe prob wasn't necessary but it made the coupling a little simpler).

Cliff Rogers
8th May 2007, 03:47 PM
... if you already have a suitable Longworth I'm not sure the vac chuck will add anything much.

Happy to post a pic or two.

I'm interested in some pics.

I don't really need a vacuum chuck... I just want one now. :D

I have the BIGGEST set of bowl jaws that I could buy at the time & they are good, pics here...
http://www.woodworkforums.com/attachment.php?attachmentid=37353
http://www.woodworkforums.com/attachment.php?attachmentid=37360

These are great for holding all sorts of weird shapes & sizes BUT... they can mark soft timber, that is why there is still bit of masking tape stuck all over them. :p

TTIT
8th May 2007, 05:33 PM
I don't really need a vacuum chuck... I just want one now. :D That's about the situation I was in - the longworths did the trick EXCEPT on natural edge stuff which I seem to be doing more of. The Stubby has a vacuum adaptor built into the headstock and I scored a vacuum pump for the best price from the SIL so what did I have to lose? :doh::C. Indeed! :- (hair, brain cells, sleep etc!!!)


Yep, mine is MDF a with neoprene sheet glued on and some rings marked in pen on it to aid centring. .....................
.............Though frankly if you already have a suitable Longworth I'm not sure the vac chuck will add anything much........
.................. This had a cheap foam surfaceThe neoprene is interesting Ern. I couldn't find what the pommy articles I researched prescribed for the faceplate chuck - eventually discovered 'EVA foam' which is closed cell but the only stuff I could get was 6mm (a bit thick) which I am yet to test for real. I've since found some 3mm EVA which will go straight on the faceplate chuck if the 6mm doesn't work out. Could go on and on but I think some pics will explain it all better! .........cuppla days!!!:;

rsser
8th May 2007, 06:02 PM
A vac cup chuck out of PVC DWV pipe would be the go for nat edge.

And there's lots of posts on US sites about amount of suction if you have the real thing; expect you've seen them Vern.

Yeah, can't recall what Clark rubber called that blue foam in the pics. Whatever, not very durable.

I actually haven't tested the new vac chuck on the Stubby. Depends on the special washer in the port system being correctly located and properly greased. After replacing the bearings I'm not sure about that.

As for 'want, not need' I can relate to that ;-} ... I've caught the handplane affliction. With turning I love the tools, the work and the outcome pretty much equally. With planes the balance is different; heaven knows why.

rsser
8th May 2007, 06:10 PM
PS ... Cliff, I use the big VM cole jaws too, and your pics reminded me. Tho they're a pill to set up they do allow you to apply rather more force to foot finishing than with a vac chuck (at least my electrolux powered job).

Looking at your pics you really seem to have cranked the pressure up on them, way beyond what I've ever needed to do. But then I only use them for cleaning up as a last step.

Cliff Rogers
8th May 2007, 06:21 PM
...Looking at your pics you really seem to have cranked the pressure up on them, way beyond what I've ever needed to do. But then I only use them for cleaning up as a last step.
In those pics, I was using them to cut a chuck foot in a rough blank, not cleaning up. If I am really worried about it taking off, I bring the tail centre up as insurance. :2tsup:

The masking tape trick was for a clean up job... if you do them up too tight, they mark the timber, if you don't do them up tight enough, the piece can slip & spin inside the jaws.
The masking tape helps the grip. :wink:

rsser
8th May 2007, 06:44 PM
K, that explains it.

As for marking or spinning, I've not had either happen fortunately. (cough, hesitates ... ah, my buttons have convex and concave faces ...? ... Yep, looked again; yours do too. You must be eating your Wheaties :D )

littlebuddha
25th May 2007, 12:10 PM
Hi the LongWorth chuck is easy to make and is good to use. I made one and made the bit for fixing to the lathe out of beach and threaded it then added to the base of the chuck rather than finding the right nut or wasting a face plate. there is a link to a site that shows how to make one also a pdf file as well on the downloads page of my site if you are interested.

www.shapewood.co.uk (http://www.shapewood.co.uk)

ticklingmedusa
25th May 2007, 01:18 PM
Wet wood problem. Use sheet plastic to prevent wet wood to metal contact. Bit of garbage bag.
Also do not close too tight. Just enough to hold.

This can also be done with a cross section cut to size of an
inner tube... basically, a heavy duty rubber band.
Recently I discovered this type of rubber bracelet www.24hourwristbands.com fits over my expansion mode talon chuck perfectly.
tm

rsser
25th May 2007, 03:14 PM
Neat idea TM.

ticklingmedusa
25th May 2007, 08:10 PM
I forgot to mention that a larger piece of inner tube can be stretched over the outside of the chuck to protect your hands & tools when you're working close.
tm

hughie
25th May 2007, 08:54 PM
The neoprene is interesting Ern. I couldn't find what the pommy articles I researched prescribed for the faceplate chuck - eventually discovered 'EVA foam' which is closed cell but the only stuff I could get was 6mm (a bit thick) which I am yet to test for real. I've since found some 3mm EVA which will go straight on the faceplate chuck if the 6mm doesn't work out. Could go on and on but I think some pics will explain it all better! .........cuppla days!!!:;
[/QUOTE]

Clark rubber used to sell closed cell neoprene in a couple of thicknesses[4mm,6mm]. I know this as I used to buy from them for various R&D projects and its what I would use for my vac chuck to seal.

On the on the hand vac tables for cnc routers use a different system. The table has a series of grooves machined in it. Square, round, eliptical or whatever is needed. Into this is placed O-ring rubber, the vac comes through a single/several hole/s in the centre around 10-12mm or so
http://www.techno-isel.com/CNC_Routers/Accessories2.htm
http://www.techno-isel.com/CNC_Routers/accessories2_2.htm

The O-ring is a soft closed foam and can hold job very securely, although the vac units are big 25hp...:o mainly due the large area and porosity of the material being machined I suspect
For turning, no where near the size would be needed as long as the vac pump had the sufficent vacuum ie 80%+ and most small vac units should be able to achieve this.

WOODbTURNER
26th May 2007, 06:19 PM
My preferred method is the Longworth chuck - like 'em so much I made two! Trick is to make them so they fit on to your normal chuck/jaws so theres no need to muck around swapping chucks. I've made mine from perspex but the originals were made from ply. Very easy to make and very easy to use - worth a shot.:D

This might be old news but I came across this when looking for info on the Longworth Chuck. Makes me wonder if this manufacturer has given Mr Longsworth's family any recognition or monetary reward even though he did'nt have a patent on it. www.chickandduckmfg.com (http://www.chickandduckmfg.com)

TTIT
28th May 2007, 08:49 AM
This might be old news but I came across this when looking for info on the Longworth Chuck. Makes me wonder if this manufacturer has given Mr Longsworth's family any recognition or monetary reward even though he did'nt have a patent on it. www.chickandduckmfg.com (http://www.chickandduckmfg.com)Looks like they've been careful not to make any claims of inventing it at least! , and at the prices they have on them, I think most turners will still roll their own for a while yet. :shrug:

rsser
9th June 2007, 03:24 PM
'Sposed to have been independently invented:

http://www.fholder.com/Woodturning/Rimchuck.pdf