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A replacement Palm Tungsten E stylus.


My son, Peter, has a Palm Tunsten E PDA  - the same model as mine - and I knew he had lost the stylus for it. I decided to make a replacement in the workshop for his birthday and incorporate some design 'improvements' in the process.

The finished stylus
Tip unscrewed - showing the addition of the flat-bladed screwdriver
Tip screwed in, leaving the click-stop locating band
Top unscrewed to revealthe reset pin
Another view of the finished stylus
The original design sketch. Dimensions were taken from my stylus and recorded in imperial and metric as I knew some parts wouold be made on the Myford (imperial) and some on the Unimat (metric)
The tip design and the original design for a split body that would also house a crosspoint blade. In the event, Pete's birthday was looming fast so I used the old software project manager's adage - if you're behind schedule, jettison functionality, not quality.
Having turned the body to diameter and drilled for the cap, the next step was to tap M4 to accept the threaded cap.

(Yes, I know the oiler's a bit low!)
The body was then reversed, and drilled ready to accept the screwdriver blade. Then the end was turned and an M4 die run  down. Originally, the idea was to soft-solder the blade in but the blade (cut from a watchmaker's screwdriver)  was such a good fit it was press-fitted in in the vice.
On my stylus, the plastic reset pin is bent over because it is only 1mm dia and being moulded plastic, rather weak.  For Pete's version I decided this would be stronger if I turned a 1mm aluminium pin and press-fitted this into the cap. Using the Unimat to do this ensured the pin was exactly square to the cap.
The Tungsten stylus has a little finger catch to pull the stylus from the PDA. After thinking about how to do this for a long time I decided to make the catch as a separate piece of Delron let into the turned cap and then shaped to fit. Luckily I had just the right diameter milling cutter to mill the slot - shown above.
A separate piece of Delron was then turned to be a light press-fit into the milled slot in the cap. To ensure it seated correctly,  a flat was milled in the pillar drill with the job held in a cross-vice.
Having milled the flat, the part was reversed and sawn-off (using the saw blade from the Dremmel) and cut to the cap diameter plus the extra height for the finger catch.
The prepared insert was then glued into the cap. There is a slight design flaw here. In use, Pete pointed out that if you drop the sytlus into the PDA and the finger catch is not aligned with the slot, it hits the PDA body and puts a lot of load on the glue - which has come unstuck and needed re-gluing. A better design would have been to have milled a blind slot in the cap (like a mortice & tenon) so the load was taken by the plastic and not the glue.
The tip was surprisingly tricky to make. The Palm stylus has a nice continuous curve to the end cap.  This was approximated by taper turning at two angles and then hand-blending the curve. The depth of the drilled hole to house the screwdriver blade was critical - too deep and it would break through the taper, too little and the tip wouldn't screw home. The first attempt at this weakened the part so much that during facing the end to length, the part split - an evening's work down the pan :-( .

A further difficulty was that I drilled the end to hold the  tip strengthening pin after turning the taper and subsequently realised the hole was not exactly square to the body. If you look carefully at the cap on the actual stylus then this misalignment can be seen.
The tip assembly, body with screwdriver blade fitted and cap assembly.
Test-fitting in a Palm Tungsten E. The cap was shaped by hand  to meet the compound top shape of the PDA using a Dremel fitted with a miniature drum sander.