R8 spindle project based on LMS#1407

[mcantelobre]

Background:

I'm building a CNC mill in the spirit of the Swede CNC mill.
For this mill I have 3 project

-1- build a R8 spindle based on the LMS#1407 (new project)
-2- Repair a broken spindle found Triangle Machineryin San jose.
-3- Use a Mori-Seiki tool holder as a mill spindle.

Few days ago I win on eBay a pair of angular contact bearing type BM-J 348 from Norma-hoffman they are ABEC 7 ID= 35mm and OD=72mm, they are magnific.

Now it is time to start to hink about the design the spindle project #1 , the open questions are:

-1- Type of bearing assembly ?(back to back, face to face)
-2- Calculation ? necessary ?
-3- Bearing housing , material (dimension, cylinder ?, box type)
-4- preload adjustement
-5- bearing lubrification
-6- Maintenance
...
..

I'm planning to share my ideas , but I need yours also, so do not hesitate to contribute

Thanks in advance


Michel

[Mcgyver]

Michel, iirc, back to back is strongest isn't it? hopefully we get a real bearing expert piping up, but i was under the impression that the abec7's are usually sold as a matched pair and if used b2b already had the right preload - ie difference in inner/out race thickness so how would adjust the loading other than surface grinding spacing washers?

It would be great to get some commercial precedents, maybe sectional drawing of a Bridgeport of similar spindle – something to start from.

I assume since your saying back to back or front to front that the angular contacts in a set at one end, and a regular bearing used at the pulley end? That’s the way I'd go, as it all reduces/eliminates thermal expansion issues.

I’d be thinking cylindrical steel just for ease of procurement and machining - making an iron casting is currently beyond me. Not sure if I’d bolt or weld on mounting brackets, or maybe some clamping arrangement like on a tool post grinder. If I did weld on the housing I'd for sure get in stress relieved and finish machine afterwards – which could make for a more complex machining process.

without going out to shop to measure, it seems like those bearings aren't big enough for and R8 spindle are they?

This is a project I also want to undertake so am looking forward to seeing yours and others ideas