Tuesday, June 30, 2015

A 4 jaw Wood Chuck Modification

When I was still with the Ornamental Turners group I was on the look out for a Independent 4 Jaw chuck often discarded by wood turners off old or cheaper lathes. David Laird and Darrell Smith picked one up from out Mudgee way,  that was some 4 years ago.
The chuck had a 3/4" 19mm bore - spindle thread which wouldn't fit any lathe I had, I had arranged to have it drilled and tapped to 1"x10 to fit the Jet mini spindle but Tim moved to greener pastures.

The 4 jaw chuck as it was prior machining and new washers.

Rear of the chuck showing original washers which were to small.

Below the jaw lead screw.

Now I have the Myford ML7 I had the opportunity to do this myself.

After removing the jaws of the wood chuck I mounted the chuck off the rear spindle shaft in the 3 jaw chuck on the Myford to check balance and run out.

Above and Left mounted in the 3 jaw chuck.

Right a spray with WD40 and a clean up.

My first mistake was just doing this visually, my second mistake was then mounting it in the 4 jaw chuck with the face to the headstock.
Having not checked run out using a dial gauge when it was mounted in the 3 jaw where I should have just drilled and tapped the bore using the 3 jaw chuck then checked run out again.

Lesson learnt.

Below I bored an area or 5mm to allow a clear shoulder.

  Right showing the clearance of the jaws to the bed of he lathe.

Once the bore was drilled and tapped 1"x10 I was able to fit it to the Jet mini Variable speed lathe I have......well I thought so. Seems the Jet spindle thread was tapered to the headstock and hardened, Ken came to my rescue we tried using my 1"x10 die to cut the thread but as it was hardened it only cleaned the thread or removed very little. Ken used a diamond file to deepen the pitch and used an adjustable reamer to remove some thread peak in the bore of the chuck. That worked, we got it to screw up tight to the shoulder.

Test fitting to the Jet.

Below parting a washer.

Thats when as I increased RPM to over 1100 I noticed a vibration much like when a car wheel has lost a balance weight, go above 1500 rpm and it ran smooth again.
All this testing was done without the jaws fitted. I used a dial gauge to check run out I got a .005 thou reading on the face in two areas, and a .007 on two way sections where the jaws run. The ways obviously had not been machined at all as the sand casting impression was not machined.

I re-mounted the 4 jaw chuck into the 3 jaw Myford chuck and machined the face (yes I checked run out first it matched that of the run out on the Jet Mini).
I also machined the out edge which wasn't square to the face even prior machining.
I used a file to level the ways (one day I'll learn to hand scrape) the filing proved positive.

 In remounting the 4 jaw to the Jet Mini it ran much better but still the vibration was there at around 1350 RPM to 1500 RPM so an improvement. In considering machining the webbing area of the back of the chuck which of course is cast iron, I can machine the ways and inner rim but the rough cast area is something else if thats where the vibration is coming from. Even with the jaws fitted and new washers little change was made.

Ken suggested it may be the bearing of the Jet Mini checking using the Nova chuck shows no vibration.

My use of the chuck is more for surface decoration of turned items not as a high speed/RPM chuck. So my work RPM will generally be below the vibration area.

I will look further for the problem but my hunch is the casting itself.

The finished chuck with jaws mounted. I have a Chuck key to make I will be using a 3/8" extension bar of a socket set weld a T bar to it.

Microwaving English Oak Turning Blanks

A friend Pat contacted me to say he was slicing up some English Oak and would I like some?
Straight away all I could thing about was another spinning wheel being made. I soon put that thought out of mind.
Sue had mentioned she required a medium size Mortise n Pestle, she had spotted one Jamie Oliver uses which appears to be a laminated English Oak, just the size she was after.
A 6" Cube would do nicely thanks Pat!

Thanks to Alan for picking the very wet 400x250 log up at the Sydney wood show it must have weighed close to 10k's wet. Dragging that from the pavilion to the car park poor old fellow.........of course along with his purchases and back pack full.

I sliced and diced it to workable size, getting two 6" dia x 6" high blanks as well as two 400x50mm spindle blanks ideal for a pair of candle sticks or light columns.
A number of spalted pen blanks and a couple of small bowl blanks  4"sq x 2" h.

Of course still all wringing wet, so the old shed microwave got a work out.
The two Mortise blanks of 6 x 6 got a total of 12 mins bring the moisture content down to 25% (I bought an Workzone Digtal moisture metre only one left).

The microwave was set to high, set for 6 min total but I only allowed 3 min period with intervals where I would open the door to allow the steam to condense and check the process of temperature increase.Allowed to rest overnight and a second session done the following day.

The two 400x50 mm pieces got a total of 9 min at 2 min intervals. The pen blanks all together at once got about 8 min at 1 min intervals.

The pith or heart area already had some checking it only became slightly worse after being in the microwave and after a week no further movement has been noticed.

 Above the pen blanks
Right the 400x50mm peices

 Two of the odd size pieces destined for other use.

Below in the left side of the microwave is moisture puddle from the blanks this was wiped up.
Right is the large piece showing the checking.

Below one of the 6" blanks and the checking - splitting this should be turned away easily enough.

 Below the other 6" blank.

 As with food a Microwave cooks from the inside out and caution should be of over length/period/time and temp at which the timber is submitted for.
I have seen the results of a Camphor blank approx 6" x 6" scorched black in the centre emitting smoke but outside still normal in appearance. The fellow burnt his hands when lifting the piece out.

I had considered using paper bags but the size I required i had none large enough. The paper bag reduces the speed at which moisture evaporates. 

Friday, June 19, 2015

Mallee Burl Weather Station

Birthday present for Mark his request little did he know I bought the gauges some 6 years ago to do this.

The Mallee burl was bought about the same time.

Holes were drilled right through so that the gauges get direct ambient air circulation. This also allows either side of the Burl to be used as the face.

Finished with six coats of Danish Oil hand rubbed to 1200 grit.

Happy 38th Birthday Mark.

Friday, June 12, 2015

Wandering Round and Table For 6x4 Bandsaw

Tony's (the electrician who did the wiring on the Myford) daughter is having her 7th birthday in July with a Harry Potter theme and requested some wands made as his gear is all still in storage.

 I made 7 a variety of timbers all just off cuts laying about with Sue's help she added a bit of blink to them.
 As Tony asked if they could be done by the Sydney Wood Show which starts today 12th June I only got to apply 2 coats of Danish Oil but they were sanded to 400.

My 6x4 bandsaw has/had a vertical table but I always found it to light in using it as it would flex, come loose with harmonics. I have to thank a variety of other 6x4 owners who modified theirs in a similar manner. I used 1/4" plate made it approx 1" larger all round and cut the back corner off to allow it to fit.

Testing on a quick cut had no harmonics and a tight plate which didn't come loose.
The plate cost me $9.00 from Edcon at Revesby.