There is excelent YouTube series: Making a Toolpost Grinder by Clough42
Playlist of the whole series.
Drawings etc.
http://clough42.com/2018/05/24/toolpost-grinder-part-24-first-test-grind/First I have to complment him of showing his process. Very well represented and most ideas are clear and well put. One of best I have seen.
However, it would not be me, if I would't think that while it is very inspiring and well though, there are some features that i will take different approach.
I plan to use same over all design and most dimenssions as they are. This is no problem, because he basically worked with metric parts and dimenssions and when not, he showed the rationale.
I'll be most likely using 400W BLDC motor, that lost it's ER11 chuck on the other thread.
https://madmodder.net/index.php/topic,12957.0.htmlI am torn between using a very good ER20 C20 extension or the one I don't have any use, but it is little minus tolerance on C20 shaft and 0,03 mm TIR on the ER-cone.
The part I am planning to deviate from original design is bearing arrangement and mounting.
While the original design relies threaded caps to fasten the bearings onto spindle body, I am thinking to mount them a little differently.
One clear departure is that I'm not using threaded caps, other how free brearing is mounted I will make two exra bosses to aid bearing removal, if it ever comes necessary. Front boss will have bit over 20 mm holes and will have light press fit into spindle housing. When front bearing is removed , 25 mm rod can be pressed inside of the spindle housing and this will meet the ID20 mm boss that will push the front bearing out at outer race (plan is to prevent brinneling through balls).
Front bearing will be fixed (as in the original design), however I'm planning to use light press fit and glue if necessary. Front bearing has a light press fit onto spindle (ER20 C20 extension), possibility to glue. There will be spacer/flinger on the spindle to locare the spindle onto front bearing inner race.
Rear bearing will have a sliding fit onto spindle body and it will be preloaded with a wave washer outwards. prper preload of this wave washer is when it is compressed to 1 mm wide space. There is a lgiht press fit boss, fairly similar than to eject the front bearing, but here it is to size a 1 mm space for the wave spring. I though that while the belt drive will most likely guarantee mininimum loading for the rear bearing to prevent balls from skidding and wearing out the bearing in no time, does not hurt to make it proper way. While lightly loaded bearing arrangement of this kind can work with a sliding fit between inner ring and shaft, it is not good habit when loading is higher, thus I'm considering gluing the rear bearing inner ring onto shaft, when it has proved to work and preload is established.
Some pictures of the progress this far.