adding high speed spindle

[magicniner]

Here's my set up fitted with the ER11 Milling Spindle which I built, it's genuinely an afternoon job and by applying the principles in Harprit Sandhu's book on spindles I came up with a design using a pair of bearings at the nose which are bonded to both the spindle and sleeve and a top bearing which is bonded to the spindle only and is a sliding fit in the sleeve.
The pulley on the mill spindle gives 4.7x which gives a theoretical 32900RPM top speed with my mill's 7000RPM top spindle speed, the belt is round polyurethane, bought by length and welded with a disposable gas cigarette lighter ;-)



You don't need a slide but I used the Deltron slide modified to micrometer adjustable spring loading to allow the use of a spare micrometer depth controlled spindle which came with my Gravograph IM3 shown fitted here -



The engraving spindle has an adjustable "nose" which is micrometer adjustable to allow a precise amount of the cutter to protrude, by applying spring pressure on the slide the engraving spindle nose will follow uneven and curved work surfaces maintaining a fixed depth of cut, the nose fitted incorporates a spherical follower which is very good for maintaining depth of cut over significant changes of surface angle, up to around 30 degrees -
Springing also allows "Diamond Drag Engraving" without the spindle running,



This is the milling spindle -



It's had 40+ hours of run time with no sign of any issues.

Post any questions you have and I'll do my best to give a useful answer,
Regards,
Nick