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Daddy3x
18th February 2009, 04:15 PM
So I finally got some longer m4 screws and broke down and bought some "buttons" from the company. I made 12" dia disk from scrap from 5/8" mdf. I finish tested and turned the bottoms on three bowls that had been sitting waiting for me take a "sick" day. Well, the first two went well, the thirrd one was a charm, it really exploded off, 3 of the 4 wings snapped off, but hey, i was able to save the bowl ! it will now be more of a contempporary peice, with some hand carved details and a whole lot of sanding :D

any suggestions on a new material to make my next set? Slow lathe down using same material? I am just too cheap to buy that aluminum set.

DavidG
18th February 2009, 04:20 PM
:worthless: :roll:

Sawdust Maker
18th February 2009, 04:24 PM
:whs:

robutacion
18th February 2009, 04:54 PM
Hi Daddy3x,

Yeah, you and another thousand of us went through the same. A simple search on our library will give more ideas than you can poke a stick on...!, seriously!. :D

Good luck

PS: Are you good and quick at "ducking"?

Cheers:2tsup:
RBTCO

Mulgabill
18th February 2009, 05:07 PM
G'day Daddy3x
As with all types of Cole jaw chucks, it should be used at slow speed. The centrifugal force of such a type of chuck is greater when "loaded" with a bowl.:o

joe greiner
18th February 2009, 11:31 PM
Material might not be the culprit. More likely inadequate edge distance to the holes, or between holes. If your MDF pattern is cloned from a stronger material, bad news.:oo:

Cheers,
Joe

Mobil Man
19th February 2009, 01:26 AM
Go with 1/2 or 3/4 inch plywood. You'll never blow it apart.

Daddy3x
19th February 2009, 04:52 AM
Thanks everyone. I did take some pics, however I need to consult my nine year old on how to reduce it to 800 x 600 pixel size for uploading, it is at 3024 x ? right now and I don't have time to research that up right now. I am good at ducking, and even better at being certain I am listening to what is happening, it gave me my first clue that something was about to hit the fan (literally too). I used common sense and stayed out of the line of fire, had on a faceshield, but had no shirt on at the time (just tinkering for a minute while waiting for the clothes to get out of the drier). Usually I wear a leather apron. Thanks again, I will be working of pic issues.

QC Inspector
19th February 2009, 06:35 AM
Thanks everyone. I did take some pics, however I need to consult my nine year old on how to reduce it to 800 x 600 pixel size for uploading, it is at 3024 x ? right now and I don't have time to research that up right now.

You could just re-shoot the pictures at the lowest resolution setting on you camera. I suppose you'll need to ask your 7 year old daughter how to reset the camera though.:wink:

Daddy3x
19th February 2009, 08:29 AM
The easiest directions I have ever been given, thanks:doh: I wish some of my colleagues would give such brief answers. I only know what I need to know about computers, will try to post pics later.

Daddy3x
19th February 2009, 11:11 AM
Here the mess is. My daughter just told me to get the directions out, I hate doing that.

Alastair
19th February 2009, 01:29 PM
Haven't tried it myself yet, but have heard of HDPE or nylon sheet, (eg cutting board) being used successfullly for this.

regards

powderpost
19th February 2009, 04:46 PM
Made a set some time back. Went to the local machine shop and bought a square of aluminium and cut it round on the bandsaw. I have a nonferrous metal cutting blade in the saw. The buttons are made from a nylon cutting board bought from a Salvo's Store. I have used it many times without failures. Lots of hole boring and thread cutting, but it was worth it.
Jim

Skew ChiDAMN!!
19th February 2009, 06:42 PM
MDF!?!? :oo::doh::no:

PLY! :2tsup:

Or perspex or ally or... almost anything 'cept MDF or chipboard or particleboard! [shudder]

Don't forget that there's not only centripetal/inertial forces at play (there's no such bogeyman as "centrifugal force" :p) but there's also lateral forces pushing the jaws towards towards the headstock. eg. any tailstock pressure on the bowl or any lateral pressure you're applying to the tool, etc.

And with cole jaws being as "long" as they are, that's a lot of leverage. It doesn't take much to snap a 1" wide strip of MDF and the jaws aren't that much wider at the chuck end...

QC Inspector
19th February 2009, 08:46 PM
The easiest directions I have ever been given, thanks:doh: I wish some of my colleagues would give such brief answers. I only know what I need to know about computers, will try to post pics later.

Glad to help and surprised to see that someone actually followed my advice.:U

Can't add too much to what the others have said about materials except. Don't use Plexiglas / perspex! It is brittle and may break like the MDF did. If you want your bowl to appear to be spinning in midair to the amazement of onlookers, then use a polycarbonate like Lexan. It's what they use in safety glasses and face shields because it is tough and flexible.

Ed Reiss
20th February 2009, 12:11 AM
Glad to hear that you weren't injured when the wings decided to go their own direction.

Don't mean to sound negative about making your own jigs and such, but sometimes it pays in the long term to just shell out the $$ for the proper gear.:cool:

joe greiner
20th February 2009, 12:26 AM
I skipped the Cole jaws myself (store-bought or DIY), and went directly to DIY Longworths. A forum search will find plenty of examples, as well as some precautions. Hint: Filament tape is cheaper than cranium surgery or shed reconstruction.:wink:

Cheers,
Joe

hughie
20th February 2009, 10:22 AM
Hint: Filament tape is cheaper than cranium surgery or shed reconstruction.:wink:

:U darn good advise, remember tape is your friend :U

As to info on this forum theres a truck load of it pertaining to Cole jaws and Longworth chucks etc, use the left hand side under "User Info" its abit more user friendly

rsser
20th February 2009, 10:39 AM
Speaking of tape, here's another option for bowl mounting for foot cleanup ...

Fix a ply or thick MDF disc to a faceplate.
Cut a series of shallow V grooves side by side in the front.
Mount your bowl rim in one of the grooves,
and fix it there with overlapping strips of tape.

Outlined in the last issue of Woodturning Design mag that hit our shores.

hughie
20th February 2009, 10:48 AM
Fix a ply or thick MDF disc to a faceplate.
Cut a series of shallow V grooves side by side in the front.
Mount your bowl rim in one of the grooves,
and fix it there with overlapping strips of tape.




:U there you go, tape is your friend. Good tip Ern :2tsup:

rsser
20th February 2009, 10:59 AM
At the last turnfest here mentioned reinforcing a thin bowl with tape to reduce flex, the best tapes for this purpose being Sellotape or packing tape (presumably because they're not made to stretch; I guess Joe's filament tape is in the same category).

TTIT
20th February 2009, 11:09 AM
I usually use masking tape - no stretch and it leaves less crud behind because it's designed to be removed :shrug:

rsser
20th February 2009, 11:22 AM
Good thinking Batman ;-}

(though all my rolls have dried out after our last heat wave .... winge, moan, mumble ... ).

And of course the first time you try the grooved faceplate your bowl rim will exactly match a high point :doh:

artme
20th February 2009, 11:42 AM
Wouldn't use perspex for Coles Jaws - Prone to shattering and is tempstuos stuff to drill.

I have seen home made models from aluminium, polycarbonate, ply and UHMW stuphph.
All good but the UHMW ones were a little flexible.

TTIT
20th February 2009, 01:47 PM
.......And of course the first time you try the grooved faceplate your bowl rim will exactly match a high point :doh:What about something like this Ern. I haven't used or seen the faceplate you're talking about but making it reversable with the grooves off-set would cover more sizes. Hmmmm - something else for me to make :C

Ed Reiss
20th February 2009, 01:52 PM
Wouldn't use perspex for Coles Jaws - Prone to shattering and is tempstuos stuff to drill.

I have seen home made models from aluminium, polycarbonate, ply and UHMW stuphph.
All good but the UHMW ones were a little flexible.

hmmmmm....what about carbon fiber?? I'ts suppose to be super strong.

rsser
20th February 2009, 02:36 PM
More good thinking Vern.

Strength and flex would be more critical in the design.

joe greiner
20th February 2009, 10:03 PM
Speaking of tape, here's another option for bowl mounting for foot cleanup ...

Fix a ply or thick MDF disc to a faceplate.
Cut a series of shallow V grooves side by side in the front.
Mount your bowl rim in one of the grooves,
and fix it there with overlapping strips of tape.

Outlined in the last issue of Woodturning Design mag that hit our shores.

That was my first method, with custom-cut grooves. Found in an article by Betty Scarpino in "Lathes and Turning Techniques - The Best of Fine Woodworking," 1991. ISBN: 1-56158-021-X But it never hurts to put old wine in new bottles.:wink:

My bowls are never the same diameter, and I got tired of cutting new grooves and/or cutting new disks for each one. Hence the Longworths - more adjustable. Almost any kind of tape is better than nothing; the "filament tape" has fiberglass strands embedded in the adhesive. Some folks suggest stapling tape on the back of the disk, but I haven't found it necessary, except for really poor adhesive.

One more thing, especially for green-turned pieces: Turn the bottom, only at the bottom. Forget about cleaning a "little way up the sides" - a recipe for disaster.

BTW, Betty is now Editor of the American Woodturner Journal.

Cheers,
Joe

Jack E
21st February 2009, 01:12 AM
Don't forget that there's not only centripetal/inertial forces at play (there's no such bogeyman as "centrifugal force" :p).
You may want a re think there Skew.

Both forces exist but it is more cenrifugal than centripetal force that would break a dodgy set of jaws :)
centripetal |ˈsɛntrɪˈpiːt(ə)l| |sɛnˈtrɪpɪt(ə)l|
adjective Physics
moving or tending to move toward a center. The opposite of centrifugal .

centrifugal |ˈsɛntrɪˈfjuːg(ə)l| |sɛnˈtrɪfjʊg(ə)l|
adjective Physics
moving or tending to move away from a center. The opposite of centripetal .

Skew ChiDAMN!!
21st February 2009, 01:38 AM
You may want a re think there Skew.

Both forces exist but it is more cenrifugal than centripetal force that would break a dodgy set of jaws :)
centripetal |ˈsɛntrɪˈpiːt(ə)l| |sɛnˈtrɪpɪt(ə)l|
adjective Physics
moving or tending to move toward a center. The opposite of centrifugal .

centrifugal |ˈsɛntrɪˈfjuːg(ə)l| |sɛnˈtrɪfjʊg(ə)l|
adjective Physics
moving or tending to move away from a center. The opposite of centripetal .

Not quite... Both terms above are simply adjectives. You can have Centrifugal Motion, for example.

My contention is that there is no such animal as what is commonly called "Centrifugal Force." People mistakenly mislabel Inertia (a masses "desire" to keep travelling in a straight line) as Centrifugal Force but giving something a name doesn't automatically mean it exists. Otherwise we'd be neck-deep in Unicorns, Gryphons, Fairies, etc. :wink:

Lessee... let's say we have a toy car traveling in a straight line. To get it to travel in a circle, you apply pressure on the opposite side to the direction you want it to turn - towards the centre of it's desired "orbit." You're applying a Centripetal Force. There's no other force being applied beyond what YOU are applying. To say that the car is exerting Centrifugal Force back on your finger is wrong... that's like saying a table is exerting force on your finger when you press down on it.

When Cole jaws break it's simply a case of the moment of inertia requiring a centripetal force to be applied that is greater than the tensile strength of the material.

Jack E
21st February 2009, 01:48 AM
No, Cole jaws breaking is the result of centripetal force being overcome by centrifugal force.

Whether you believe in centrifugal force or not is irrelevant.

It exists,

You can't believe in centripetal force and not centrifugal force as one can't exist without the other.

In fact, you can't "believe" in either, they are proven forces not open to conjecture.

Jack E
21st February 2009, 01:51 AM
When Cole jaws break it's simply a case of the moment of inertia requiring a centripetal force to be applied that is greater than the tensile strength of the material.
Otherwise known as centrifugal force :2tsup:

Skew ChiDAMN!!
21st February 2009, 02:36 AM
No, Cole jaws breaking is the result of centripetal force being overcome by centrifugal force.

Whether you believe in centrifugal force or not is irrelevant.

It exists,

You can't believe in centripetal force and not centrifugal force as one can't exist without the other.

In fact, you can't "believe" in either, they are proven forces not open to conjecture.

:no: One of the first things taught in Basic Physics or Vector Maths? "Centrifugal Force is a fallacy."

But it's easy to see why the fallacy persists. :D It's a "lie for children" like explaining a rainbow by comparing it to light refracted through a prism.

rsser
21st February 2009, 08:26 AM
Er, just to diverge from this learned debate ...

Joe, thanks for sharing that experience.

Yes, the mag piece was by Betty.

I've been nagging her about getting current AWTs online for purchase. By the time I pay for an individual hardcopy to be posted to Oz it's about 3x the cover price in AUD. But Betty says it's two years away at least.

Jack E
21st February 2009, 09:39 AM
:no: One of the first things taught in Basic Physics or Vector Maths? "Centrifugal Force is a fallacy."

But it's easy to see why the fallacy persists. :D It's a "lie for children" like explaining a rainbow by comparing it to light refracted through a prism.
Silly me, disagreeing with science.

Perhaps I should become religious so I can learn how the world really works :D

joe greiner
21st February 2009, 09:38 PM
Well, shucks! Now that the pot has been well and truly stirred, why would I want to sit it out?

"Centrifugal" force served well enough as a perception of reality. But with the space age, and recognition of vector analysis, the mathematics didn't add up. "Centripetal" force was needed in the opposite direction. Then things got anal.

As to the Cole jaws, I haven't done any experiments, but I think the offender is cantilever action on the thin parts at the attachment point, produced by pushing the tool parallel to the lathe axis. And this is where there's the least amount of material, further reduced by attachment holes. Spinning effects probably don't have as much influence. Good timber needs to be about double the thickness of an aluminium pattern for equivalent stiffness; MDF maybe more.

How about photocopies, Ern? For personal use only, of course. Absent that, Google is your friend.

Cheers,
Joe

rsser
22nd February 2009, 07:54 AM
My guess is that AWT is pretty uncommon downunder Joe. I've not heard any ref to it among forumites or the turning networks in my city. And my local libraries are poor for any kind of WW mag.

aak
22nd February 2009, 05:49 PM
Not quite...

...There's no other force being applied beyond what YOU are applying. To say that the car is exerting Centrifugal Force back on your finger is wrong... that's like saying a table is exerting force on your finger when you press down on it.

....

Well, I did not intend to buy into the debate, but.....

If there were no opposing force from the table to your finger, your finger would go right through the table and create a hole in it or break the table! In fact, every force has one or more opposing force/s to it.

Regards
Andy

Skew ChiDAMN!!
22nd February 2009, 08:35 PM
My guess is that AWT is pretty uncommon downunder Joe. I've not heard any ref to it among forumites or the turning networks in my city. And my local libraries are poor for any kind of WW mag.

The Public Libraries around here don't stock much on Woodturning either. Apart from the odd Raffan and I'm told they're constantly disappearing off the shelves and may not be restocked in future. :~

You're buying yours from O/S?


If there were no opposing force from the table to your finger, your finger would go right through the table and create a hole in it or break the table! In fact, every force has one or more opposing force/s to it.

:no: You're mistaking inertial resistance for force. A force, any force, takes energy to apply. The table isn't using energy... it's simply xferring the force you're applying through the legs into the floor, thus into the Earth. In theory (if you could apply a big enough force) you can move the Earth this way but in reality the table-top or legs would fail under waaay less force than that.

And it's every action has an equal and opposite reaction. Again, a different thing. :D

aak
22nd February 2009, 09:57 PM
.....

:no: You're mistaking inertial resistance for force. A force, any force, takes energy to apply. The table isn't using energy... it's simply xferring the force you're applying through the legs into the floor, thus into the Earth. In theory (if you could apply a big enough force) you can move the Earth this way but in reality the table-top or legs would fail under waaay less force than that.

And it's every action has an equal and opposite reaction. Again, a different thing. :D

When you stop pushing the table top (eg: your arm gets tired) and it flexes back towards to you, That is not force in your opinion, or is it?

By the way, it was you who used the table top example to prove your point. Hence I quoted it. As far as the Earth is concerned, let us not complicate the issue with it. However, I agree that the table top and its legs would fail.

Regards
Andy

Ed Reiss
23rd February 2009, 01:38 PM
....well, I can't resist getting into this one

..........gravity sucks:q

rsser
23rd February 2009, 01:49 PM
I thought it pulled?

....

Skew, I've just been ordering the odd AWT from AAW.

Did once have a sub to the UK mag Woodturning, but found later that The Woodsmith brings them in and you can sub with Len.

The local newsagent has the US Woodturning Design at about $17 which is a bit rich.

Manuka Jock
23rd February 2009, 01:59 PM
MDF!?!? :oo::doh::no:

PLY! :2tsup:

Or perspex or ally or... almost anything 'cept MDF or chipboard or particleboard! [shudder]

Don't forget that there's not only centripetal/inertial forces at play (there's no such bogeyman as "centrifugal force" :p) but there's also lateral forces pushing the jaws towards towards the headstock. eg. any tailstock pressure on the bowl or any lateral pressure you're applying to the tool, etc.

And with cole jaws being as "long" as they are, that's a lot of leverage. It doesn't take much to snap a 1" wide strip of MDF and the jaws aren't that much wider at the chuck end...

:whs:

MDF is sawdust and glue. Thats it , nothing more.
Its just cardboard !
There is no fiber running along to it to give it strength.
And natural timber , although it has running fibres , has grain , along which it can split.

When making Cole jaws with wood , the only type is plywood .
And suitable ply at that .
Good quality ply of a decent thickness . 10-12 mil. min. , for small jaws , 18-22 for larger ones .

And remember , no matter what the material , keep the speed down.

600 rpm is the recommended max.speed .

Cole Jaws are intended as a light finishing attachment only.

Skew ChiDAMN!!
23rd February 2009, 06:18 PM
Skew, I've just been ordering the odd AWT from AAW.

Did once have a sub to the UK mag Woodturning, but found later that The Woodsmith brings them in and you can sub with Len.

The local newsagent has the US Woodturning Design at about $17 which is a bit rich.

I used to buy UKWT from Len :2tsup: but somehow it seems to me to be 10 years behind the times. Not that that's a bad thing, but I usually only read mags looking for new ideas or concepts.

haven't seen Woodturning Design... might have to peruse your library at the next Ernffest. :D

Oh... and as for Centrifugal Force, this might explain it better: http://en.wikipedia.org/wiki/Fictitious_forces

Daddy3x
24th February 2009, 01:42 PM
I am going to try 3/4 birch ply. Silly question I am sure...perspex? Different name from something I am familiar with?

QC Inspector
24th February 2009, 08:35 PM
Perspex is the British name (and some of their former colonies) for what goes in North America as Plexiglas. I think both are trade names for clear Acrylic, but don't hold me to it.:wink: