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Fuzzie
12th June 2014, 01:32 PM
I'm attempting my first turned small knobs. I've attempted to follow some descriptions for turning Shaker style pulls. Two FWW articles I've read, one by Philip Lowe and another by Christian Becksvoor, both cut a tenon first on a blank and then mount the tenon in a Jacobs Chuck to turn the rest of the pull. We're talking a 1" pull on a 1/2" or so tenon.

I've had ZERO success with this method. I'm turning some rather soft Maple Silkwood. After I've got as far as cutting the tenon I try mounting it in the drill chuck, but the 3 jaws just squash into the wood and cannot really hold it. If I tighten up the chuck firmly the blank also goes off centre somewhat.

Even if I get a hold onto the tenon in the chuck, the rest of the blank snaps off pretty soon when I try turning.

I'm suspecting the North Americans would be turning pulls from Maple or Cherry which must be a much firmer wood than Silkwood. Not sure what to try next. I bought the Jacobs chuck from Gary Pye and don't have any other style of scroll chuck or anything like that to play with, just a drive spur for turning between centers.

Any suggestions??

starr
12th June 2014, 01:59 PM
You could try a morse taper collet chuck - I bought a set of 5 (6mm and up) for about $50, but I can't remember where I got them - a search on the web should find them. The collet won't crush the wood as long as you cut the tenon the same size as the hole in the collet.

Just make sure you get ones which are threaded on the end so you can insert a threaded rod through the headstock and tighten up the outboard end to prevent the chuck from coming loose.

The following youtube video shows how it works: http://www.youtube.com/watch?v=IqvCrH4dam8

Hermit
12th June 2014, 04:01 PM
Could you possibly make up a glue block with a countersunk bolt/nut through it to go into the Jacob's chuck, then glue that block to your blank for turning? Turn the tenon etc, shape as much as possible, then part off at the top and hand finish.
(Sounds like it's time to start saving for a scroll chuck. :wink:)

By coincidence, I'm wrestling with small knob making myself at the moment, but have a scroll chuck to make things easier. I turn the tenon and a 25mm base for the knob, then wrap masking tape around the base to prevent marks and reverse the base into the scroll chuck to turn the top. No help to you, I'm afraid.



Just make sure you get ones which are threaded on the end so you can insert a threaded rod through the headstock and tighten up the outboard end to prevent the chuck from coming loose.


Fuzzie, along these lines, I hope your Jacob's chuck has the same setup. You don't want to get smacked in the head by the chuck if it comes loose from it's moorings.

Fuzzie
12th June 2014, 04:16 PM
Thanks Starr. McJing seem to have something like that for about $125 and Carbatec have something for $250 but they look different and I'm not sure I want to spend $$ on a solution here.

I had a thought that maybe I could do something similar and strengthen the tenon with a plumbing olive. The GPW chuck is only 12mm but my drill press has a 16mm chuck which would accept the OD of the olive, so I stuck a thin brass olive on the 1/2" tenon and tightened it up in the drill press chuck as a test, unfortunately the olive just distorted and squashed a cleaner triangular shape to the tenon and still wobbled out with small sideways pressure. Back to the drawing board again.

Big Shed
12th June 2014, 04:18 PM
For small work like this I prefer to use a collet chuck as it doesn't just hold the work in 3 or 4 places but all around.

I use this regularly for my pen work with smaller than what you are talking about and certainly some quite soft material, eg the bark from the Red Ironbark.

See here (collet chuck came from Vermec)

http://www.woodworkforums.com/showthread.php?t=132424&highlight=finial

Fuzzie
12th June 2014, 04:24 PM
along these lines, I hope your Jacob's chuck has the same setup. You don't want to get smacked in the head by the chuck if it comes loose from it's moorings.

The MT adapter for the GPW chuck has a thread at the end of the MT2 side but not at the JT33 taper end for the chuck. It's going to take a really long screw to get all the way through the drive shaft though. I've had the MT loosen up during my experiments so far but I also hadn't seriously knocked the MT into place yet.

Big Shed
12th June 2014, 04:26 PM
The MT adapter for the GPW chuck has a thread at the end of the MT side but not at the BT taper end for the chuck. It's going to take a really long screw to get all the way through the drive shaft though. I've had the MT loosen up during my experiments so far but I also hadn't seriously knocked the MT into place yet.

When I only had an MT2 collet chuck I used a suitable length of all-thread.

Big Shed
12th June 2014, 04:34 PM
Something like this perhaps?

http://www.ebay.com.au/itm/Collet-Chuck-MT2-with-7-collets-/261501612956?pt=LH_DefaultDomain_15&hash=item3ce2b5f39c

http://www.ebay.com.au/itm/1-8-5-8-Precision-Collet-Holder-Set-MT2-Shank-Free-Postage-/351078999437?pt=AU_HeavyMachinery&hash=item51bdf0658d (http://www.ebay.com.au/itm/Collet-Chuck-MT2-with-7-collets-/261501612956?pt=LH_DefaultDomain_15&hash=item3ce2b5f39c)

chuck1
12th June 2014, 06:01 PM
Could you make the blanks longer and turn most of the job between centres? And then just sand the of knob in the drill chuck?!
Or turn tendons then turn a Timber Morse taper and then belt it headstock drill hole in Timber to tight fit tennon then turn rest of knob, and if it comes lose dip tennon in water!

Fuzzie
12th June 2014, 06:10 PM
Or turn tenons then turn a Timber Morse taper and then belt it headstock drill hole in Timber to tight fit tenon then turn rest of knob

The chance of me turning anything that accurately to that tolerance is something less than Buckley's......

ian thorn
12th June 2014, 06:14 PM
Just a thought how about a short piece of copper pipe that will fit in your chuck spit it length ways and spigit inside and tighten no crushing .

Old-Biker-UK
12th June 2014, 06:34 PM
Cheap & cheerful - cylinder of softwood drilled for knob spigot, saw down length one side and hold in three-jaw chuck. Not super accurate but works OK for small knobs. I've turned dozens with spigots down to 1/4"
Leave spigot a bit longer than required and cut off before fitting as mentioned above.

Mark

Christos
12th June 2014, 06:45 PM
The chance of me turning anything that accurately to that tolerance is something less than Buckley's......


Now I think you are being too hard on yourself.

tea lady
12th June 2014, 06:49 PM
It snaps off? Silly question....... Do you have the grain going the right way? Other wise the wood just might be to soft. Or maybe use a gouge rather than a scarper which puts a lot of stress across any holding mechanism.

I turned a stack of nobs in a little home made jam chuck with a little screw coming up from the bottom.

tea lady
12th June 2014, 06:55 PM
Here is some pics of how I did nobs. Was some softish cedar. But you can see the chuck I hope.

316457316458316459316460316461316462316463316464316465

tea lady
12th June 2014, 06:57 PM
Actually the detail pic of the chuck fell off the list.

316466

powderpost
12th June 2014, 07:56 PM
I have turned a few knobs, both small (12mm) and larger (45mm). Most simple method I have used is a 19mm thick piece of timber screwed to a small face plate, with a coarse thread screw (particle board screw) driven through the centre of the 19mm board. Cut the blanks off square and allow a millimeter for cleaning up the top. Screw the knob blanks centrally onto the screw and turn. You will need a sharp tool and careful technique. Works well for me.

Jim

Fuzzie
13th June 2014, 09:58 AM
Thanks TL and Jim. You've given me a couple of ideas for what I can try next that might work without having to buy new gear.

I'm thinking a chuck like TL's mounted on a large face plate that I have might work.

Skew ChiDAMN!!
13th June 2014, 06:28 PM
I'm a bit late, but...

I turned a few cedar pulls a while back and had similar problems. Worse, once I'd finished 'em and they were installed, they were broken off the chest of drawers in fairly short order. (The customer had some rambunctious kids. :rolleyes:)

I replaced them with another set BUT I gave up on turning the tenon as part of the pull. Instead, I drilled the blank and glued in dowels which I think I made them from meranti. But I'm not sure...

I didn't have anywhere near as many problems when turning with this approach!

DaveTTC
13th June 2014, 07:56 PM
Good idea Skew


Dave the turning cowboy

turning wood into art

Dalboy
14th June 2014, 12:00 AM
Turn them in spindle mode and do 5 or 6 at a time then part them off make up a jam chuck and finish the heads off of just sand the end

Fuzzie
14th June 2014, 07:44 AM
A jam chuck similar to TL's is sort of working for me. At least I'm keeping the blanks on the machine, it's just my tool skills letting me down. I have however moved on from 'not possible' to 'will work eventually'.

Rather than trying to turn accurate tenons in spindle mode that fit the jam chuck, for the moment I'm simply cutting a tenon on a blank first using a plug cutter. Same size every time.