[flojor10]

I'm thinking of making a diy benchtop mill, so I started in CAD with the spindle. I made a simple spindle with pillow blocks, and an er25 collet, and a 1hp motor. Will it be solid enough for milling steel? Here is all the parts I plan to use.

ELECTRIC SCOOTER BIKE 750 WATT 1 HP DC MOTOR.. | eBay

KML UCPE204 20mm 2 Bolt Pillow Block Bearing UCP 204-20mm Set Screw Locking | eBay

ER25 Straight Shank D20-150L Milling collet Holder -US | eBay

[691175002]

No, I suggest you read up on bearings for spindles. I would be surprised if such a spindle could even do a decent job on aluminium.

You need at least a pair of AC bearings, and generally you would see a pair of AC with a deep groove in the back, or two pairs of AC. The preload is important as well.

[nateman_doo]

Looks sexy though. is that 2x2 square tube steel?

[flojor10]

Looks sexy though. is that 2x2 square tube steel?

I took a look at these angular contact bearings, I see that they are mean't for radial loads so they should do better.

7204 Nachi Angular Contact 20x47x14 C3 20mm/47mm/14mm Steel Japan Ball Bearings | eBay

[flojor10]

Here's a rendering of my design I'm working on the saddle, and I changed the spindle by using angular contact bearings inside a turned aluminum housing.

[SCzEngrgGroup]

I'm baffled by this.... As drawn, it appears you have HUGE Y axis travel, but the spindle is set so far back, it appears only about the rear-most 1/3 of that travel will be usable, as the table will be forward of the spindle for most of its travel. Maximum usable travel will be roughly twice the distance from the rear edge of the table when it is as far back as it can go, to the spindle center line. Any additional forward travel will be pretty much useless.

That tubing framework looks to me like it would have very little torsional stiffness.

Your spindle design will NOT work well at all, doubly so with an aluminum housing. When the spindle heats up the bearing pre-load will increase due to differential thermal expansion of the housing (which will expand a LOT), and the (presumably steel) spindle (which will expand FAR less). The two A/C bearings should be back-to-back at the bottom of the spindle, with a single radial bearing at the top, with a slip-fit to the spindle, so thermal expansion does not affect pre-load.

[UUU]

I quite like your generous Y-travel. No use at all for actual milling, but it will allow you to bring the table out into clear air for setting up. Perhaps if you repositioned the bracing for the column you could get the table to travel right to the back of the machine and have even more!

You don't seem to have much stucture in the main bed - it's all in the column. Are you going to bolt this down to something that will add rigidity?