Video to go along with the project:
Titanium screws for Fluxcapacitor
(Link opens on Youtube in new window.)
I had to machine 30 and 10 custom titanium screws out of grade 23 titanium. 30 pieces with a TX8 torx head, 10 pieces of the larger version with a hex.
All the turning work is done from barstock, held in a collet. Turning the cylindrical OD with a resharpened DCMT insert.
The reground, very sharp insert was used to reduce cutting pressure to a minimum.
Next, a custom ground carbide tool is used to turn the step with the taper on the end and the chamfer for the thread.
Custom 20° chamfer tool:
Using a Horn 312 parting tool to cut a threading relief. Later the part will be completely parted off here.
Turning the thread with a carbide threading tool – Thread is M4x0,35:
For work like this, thread gages are a must – You need two, a GO and a NOGO gage.
The GO has to thread on completely, the NOGO may not thread on more than two turns, otherwise the thread is out of spec.
Following threading, the thread is then carefully deburred with a ruby stone and a abrasive rubber stick to remove any hairlike burrs.
After that step, the screw is parted off.
Checking the diameters with a Mitutoyo 0,001 micrometer. The diameter checked in the picture is toleranced +-0,03mm.
Using preset tools and the DRO in combination, I had only to do a minimum of checking during machining.
For the second side I needed a way to hold the screws by their thread, so I made a sub-collet out of aluminium. It was turned in one setup, slit and then parted off. It has a screw on the back to act as a depth stop.
The short screws where held in the sub-collet, faced, chamfered, centerdrilled and predrilled to make drilling the torx contour easier.
The depth stop in the sub collet allowed to work without doing much measuring.
The torx contour was milled on the engraving machine using a 0,6mm threeflute carbide endmill with 45° helix.
The longer screws where drilled axialy with a 1,3mm drill and then crossdrilled with a 1mm drill:
Using the 5C indexer, I milled the hex on the larger parts. Here a brass setup piece is shown.
Deburring took some relevant time. If you deliver a screw like this, the last thing you want, is the screw seizing up in the customers flux compensator.
A small keyless chuck and the sub-collet made for a perfect handle to hold onto the screws for deburring.
Deburring was done with tiny needle files, a sharp carbide scraper and rubber abrasives in a die grinder.
Especially the rubber abrasives do wonders in removing and blending burrs.