“I happened to mount a length of ground bar in one of my second hand 4J chucks and noticed daylight at the front of one of the jaws! Dismantling cleaning and swapping jaws over did not improve the situation. I scanned the all the normal websites for a method of preloading the jaws that would allow a full length grind. Drilling the jaws and fitting bolts, wire tensioning were some of the methods I came across, but one involved a machined plate ( "Daisy"?) that all the jaws locked onto. A lot of work- time for a cup of tea and an alternative solution.
Not sugar lumps but 1/2" brass blocks.
One jaw at a time, set to protrude into the centre. Each block is set halfway up the angled jaw face and the adjacent jaw is wound in to nip it. When both blocks are in position the selected jaw is clamped down against the blocks ready to grind. A cleaning session after each jaw grind is required.
A diamond wheel in the Flexi grind chuck wound in and out does the job. DTI checks after proved satisfactory.
No lathe mods., this time, just a couple of projects.
Having recently upgrade my Hifi system and acquired a box of LPs from a friend it seemed from a trawl of the internet that it was imperative that I clean my vinyl before proceeding. Methods were analysed and expensive equipment for cleaning the grooves was studied and of course I did what I do best, have a cup of tea and get the pencil and paper out, this resulted in two gadgets that can be used on existing turntables or mounted on a dedicated cleaning rig with a vacuum pump installed.
The first gadget is for cleaning the grooves using the appropriate cleaning fluid, it comprises piece of paint pad measuring 1"x4" bonded to a piece of acrylic sheet. Adaptors turned out of acetal for alternate mountings fit in either end, the brush has to be reversed because the bristles have a definite lie.
Once the grooves have been scrubbed 3 or 4 times each way they need vacuuming. I managed to come up with a simple device combining the vac., connection and unipivot in one unit, a sort of inverted roller ball applicator that seals instead of leaking.
The vacuum arm is fabricated from 12mm acrylic tube, the end bar has a 4" slot in its lower surface. The self adhesive pads were cut from the spares of a $500 machine.
A 20mm delrin ball is located 6" 'ish from the vacuum bar and this has an 8mm hole drilled through from the bottom.
The 20mm ball sits on a 20mm diam., acetal pedestal, in a 14 mm diam., seating, this provides the seal and permits adequate movement. The seating is drilled down to the output coupling (length of pen case). The ball seating permits arm elevation and axial movement to cope with mat thickness and warped records (I have many of those) and if a cleaning head is attached to the arm and the' turntable direction reversed then the arm can be moved 90 degs., to the other side of of the record, the captive sleeve that locates the ball pivot on top of the pedestal controls the arm position.
The only other component is the scrubbing brush, fabricated from a piece of "U" channel plastic that clips on the arm.
The unit can be mounted in the corners of the plinth using double sided tape, but I can foresee a through mounted arrangement directly coupled to a vac., pumpnot on my new deck though.
The other little job was a pair of Hifi speaker cavity phase plugs, these replace the centre dust cap on the drive unit. More internet research on the theory behind the design and the improved performance claimed sent me to the work shop, I turned some 1" lengths of acetal bar stock and made two hollow plugs with a hole in the base as in the photos.
I pressed a steel washer in the open end that would stick to the speaker pole piece. The whole assy., is turned down to a clearance fit inside the speaker coil. Testing was an eye opener (should be ear opener), the performance in the treble range was astonishing, so much do that I am going to make a few more for my other drive units. I recommend this gizmo to all Hifi nuts.
One day last week when I was checking the latest on the airgun side of you blog, a picture of my lathe carriage showing the hand wheel and x-feed dial and lead screw popped up.
No sippin' whiskey or cup of tea involved this time but I suddenly realised that if the powered drive was turning with the carriage locked on the lathe bed then the hand wheel rotates! Why not couple the hand wheel to the X-feed dial and have that powered? How come I never made this connection (groan) before?
Experimental bits.
The layout lent itself to some sort of belt pulley arrangement so I dismantled my zero-able dial and turned and fitted a pulley to the X-feed. I turned a new hand-wheel pulley and mounted it on a shaft extension so that a belt would line up. I fabricated a suitable belt and powered up the arrangement. Well it worked but with a lot of slip, so I have opted for positive drive from toothed belt and pulleys.
A selection was ordered and slimmed down to 4mm. For now I have a small fixed toothed pulley screwed to the inside face of the X-feed dial and a large pulley that is free to rotate on the hand-wheel shaft extension. The pulley/hand-wheel coupling is made by a 1/8" pin that slips through the wheel knob into one of the holes drilled in the pulley, this is to be replaced by the pen ratchet system as on my indexing attachment. A belt tensioning fitting clamps on the apron dove tails.
To use, set the tool on X, LOCK the carriage, wind in on Y to engage the hand wheel drive pin, couple the power-feed elastic band, switch on, the hand wheel will now drive the X-feed via the belt. To stop, switch off, decouple power feed band and hand wheel, then the carriage clamp, do things in the wrong order and all the good work gets ruined as the tool keeps advancing towards the chuck. You can of course make cuts from the centre by crossing the power-feed elastic band.
The cut is very fine at 2:1, I am going to try 4:1 next week, but if I find myself with a hand full of gears, then I might try 10:1. Normal drive from the gearbox will feed the X-slide in, reverse the elastic band and of course the power feed reverses and that drives the X-slide back out.”
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