The indexable mandrel handle. - Cost = $0.50
Not only do I use this to do indexing on the lathe, but also to rewind the leadscrew when cutting a metric thread (my leadscrew is imperial, so the thread chaser can't be used).
You can see that this was made for a material cost of less than $1.
|Components showing the pin & slot mentioned.|
|Measure the bore of the lathe mandrel & estimate how long you want the
shaft be. Make this as long as possible without interfering with a Morse
taper being used in the headstock.
|Inner Shaft. Make about 25 to 30mm longer than the outer shaft.
|Make the expanding taper piece next.
|Turntable Platter & Crank handle.
|Tensioning nut - anything suitable, I used an old VCR part but a large wing
nut would be just as good.
|After assembly, a good idea is to put graduations around the platter
circumference. I chose to put 1-degree markings on the circumference. This makes it usable for indexing purposes & is used
whenever I am graduating a new dial etc..
The outer end of the thread is protected by using a dome cap nut. Washers were added under the adjusting nut to reduce friction.
There you have a mandrel handle for working the lathe by hand (without the motor) - as I sometimes do for cutting small threads. This can be useful at times when screwcutting where you can't disengage the leadscrew half-nuts, but want to move the carriage back along the bed between cuts (having moved the cross-slide outward first of course).
By clamping the handle in position, it is also fully functional for simple indexing.
The photo shows it attached through the mandrel, and using a piece of angle aluminium clamped to the tray as an index pointer. The self locking wrench is my temporary method of stopping the mandrel from turning while marking on the work held in the chuck or on the faceplate. Play safe though, always unplug the lathe before clamping the mandrel - it makes sure you can't accidentally turn it on.
Made from the flywheel off an old 1960's Singer sewing machine bored to fit the end of the leadscrew, a grubscrew holds it in place, a bolt with its head cut off, 2 Nylock nuts & a small piece of stainless steel tubing as the handle. Graduated with my 'turntable platter' Mandrel handle. My leadscrew is 8-tpi, so each revolution is 125-thou, hence 125 divisions on its perimeter.
I just set up a spreadsheet to calculate the degree position of each of the 125 markings, then marked each one based on that. Marking out was done by holding the item in a 4-jaw chuck, align the mandrel handle for each division in turn, clamp the mandrel handle to stop it rotating, use the saddle controls, scrape a pointed lathe tool past the item a couple of times. Marked lengths were set to be different for 10's, 5's & 1's.
Let a spreadsheet calculate each of the 125 marking position for you in degrees - don't do it by just adding 2.88-degrees to each new mark, as by the time you have made 359 measurements, the cumulative error will be a problem & likely to be quite large.
Simply fasten with a grub screw & mount it on the gear end of the leadscrew.
Made from the base of a set of VCR heads (Identical original part shown resting on bed, final on leadscrew end). Graduated with my 'turntable platter' Mandrel handle. Graduated the same as the above hand dial, but for the opposite end of the leadscrew.
Fastened only by friction fit onto the tailstock end of the leadscrew. Instead of using a pointer to the markings on the dial, I just line it up by sight on the edge of the bed when I am using it.