DIY toolpost grinder?

[Misterg]

The current plan is to use an ER11 collet holder as the spindle, a pair of needle bearings (8mm ID, 12mm OD, 12mm long), maybe a thrust bearing on each end

FWIW, I'd go with a normal, deep groove ball bearing at each end, gently preloaded against each other. It's a simpler arrangement and there should be less slop than with needle bearings at this size. They will take the minimal thrust loads OK.

Check your ER collet extension for runout before you start - I've had both very good and very bad.

This was my attempt at something similar - aimed at drilling / machining, rather than grinding though.

Mini Lathe Toolpost Spindle

I got asked about the toolpost spindle that I use in my mini lathe, so I thought I would post some info here. I'll describe it 'as it is' - there are improvements I've yet to make, and changes to the basic design that I'd make if I were to start again. One of the main limitations of mini lathes...

www.mig-welding.co.uk

 

[ukracer]

More accurate than the ~0.3mm gap of sunlight I see at one end of the jaws when gripping the workpiece.

So.its bellmouthed then?

 

[daxliniere]

So.its bellmouthed then?

Very much so, hence this project.

 

[Agroshield]

To reach the back of the chuck jaws, the stone either has to be greater in diameter than the ER collet nut or have a long enough shank on it for the end of the stone nearest the collet nut to reach the back of the jaws. To some extent, the design of the machine that spins the stone will be dictated by the stone you can procure.