[InventIt]

I am working on building a precision spindle for my cnc router. You can read about the router here:
http://www.cnczone.com/forums/showthread.php?t=2249

The current 2.25 HP Porter Cable router on my cnc machine works well on plastics, wood and softer materials. However, milling aluminum shows the PC's weakness. I have ruined countless end mills due to chatter cutting aluminum.

SO.........I got the bright idea to try building a precision spindle based on 40 degree angular contact bearings. I chose 40 degree bearings based on the cost. I couldn't afford real spindle bearings! Hopefully they will work.

First I started with a ER-32 Collet extension I purchased from MSC. The collet holder is 1.5" dia, a little larger then 35mm. So, I chose 35mm angular contact bearings from McMaster with a 72mm outside dia. 2 of those will be mounted back to back at the collet end of the spindle. A 30mm roller bearing will be mounted at the top of the spindle to allow for maximum rigidity and belt drive.

Here is the finished collet holder turned to size and the bearings I will use.

[InventIt]

The next hurdle was machining the spindle housing. I started with a 4" dia chunk of 6061 T6 aluminum. First I chucked it in the 3 jaw and turned the outer dia and the ends to true it up. Then I decided I really don't want to sit there at the lathe for 4 hrs hogging out the center. So, I removed the chunk from the lathe and drilled-tapped two 6mm holes on the bottom. This allows me to mount my 123 blocks to the bottom so I now have a place to clamp the chunk on the table of my router. A 1/2" end mill makes quick work of chipping out the center where the shaft will eventually go. Of course I milled the dia small so I could precisly bore it to a finished diameter on the lathe.

[InventIt]

Back to the lathe......

After roughing out the center on the router the next step was to finish the bore for the angular contact bearings. After checking the milled bore for concentricity (it was within .005 TIR) I started truing up the bore till i got to 71.80mm. Then I used a propane torch to heat the housing to the expected max operating temperature of 120F. This added .06mm to the bore. So I carefully finished the bore to 72.00mm while maintaining 120F. This method should allow the bearings to have full radial contact with the housing at operating temp. Then a finish pass on the end to give me a square surface for the end cap that will retain the bearings in the housing.

Last I made a final finish pass over the outer diameter, no particular dimension here.

Next I need to make an end cap and cut the housing to finished length.

[derekbackus]

I am designing a long (96"), narrow (6") router to drill holes into and cut 45 degree angles on the ends of stainless tubes and need to figure out how to build (or find, pre-made) a low speed spindle (compared to a 25,000 RPM router!!).

Your spindle looks great. Did it work as expected? Do you have more pictures?

Thanks,

Derek

[InventIt]

Update,

Had some time to do more work on this project. Today I roughed out the bore for the top bearing. The top bearing is a plain abec1 ball bearing 62mm x 30mm to support the top end of the shaft. First I set the spindle on 1-2-3 block as before. Then clamped the assembly to the mill table.

After I got the bore roughed out for the top bearing I setup the spindle housing on the lathe in the 4 jaw chuck and centered the housing. Next step was to turn the bearing bore to size. This bore I did not heat the spindle housing to operating temp of 120F. I want the bearing to float in the bore so I made it 62.05mm at room temp.

[InventIt]

Also made the end plate to hold the dual angular contact bearings in the lower end of the spindle housing. Cut the basic shape out of a piece of 1/2" aluminum plate on the cnc router including the eight through holes for the 6mm flat head screws. Then turned the plate to size on the lathe.

[InventIt]

Did some assembly on the spindle today. The ER collet extension shaft with the angular contact bearings mounted fit perfectly into the spindle housing. I did heat the housing to about 150F to get the bearings into the the housing (remember I how I turned the final bore to finish size at 120F) This allowed just enough room for the two bearings to slip into the housing bore.

I did have one small problem after putting the end cap on and tightening the 8 screws that hold the bearings in place. I used two shims between the bearings and that was too much preload. The bearings tightened up pretty good when the cap was tightened down. So, I'll have to disassemble and remove one shim.

I can't wait to see how this thing works on the cnc router. It feels really tight/ NO slop in the bearings. I'm thinking it should make a big improvement in quality of cut and life of my carbide end mills.

In the 2nd picture you can see how small the Porter Cable collet is compared to the ER-32!

[InventIt]

I was amazed how well the top bearing fit between the bore and the shaft!!! It dropped in with a tight slip fit. This was one thing I wasn't sure was going to work out. Maybe I just got lucky?

Because of the way I machined this I was afraid the bore may not be concentric with the shaft/ front bore because I bored the two ends of the spindle housing in two different setups on the lathe. So I guess I must have done a good job positioning the housing for the top bore.

This top bearing (30mm x 62mm plain ABEC1 ball bearing) will support the driven end of the shaft and add rigidity to the assembly.

The ER collet extension has a threaded hole in the top of the shaft. I will use this to connect a pulley to the shaft as well as clamp the top bearing to the shaft with a bolt. I'll use the PC router to drive the ER collet spindle. I am thinking 3:1 ratio should be good. So if min/max speed of the PC is 10000 to 23000 then the spindle should turn 3300 to 7600rpm.

[InventIt]

More progress....

Made the mounting plate and milled a flat onto the side of the spindle housing for the plate to attach. Drilled the 4 holes to match the mounting pattern on the cnc router.

Never realized how useful 1-2-3 blocks could be! Wish I had bought these a long time ago. I used them to hold/align the spindle housing for milling.

Next thing to do is design a way to mount the motor onto the top of the spindle housing and make the pulleys to drive the spindle.

[ger21]

Any more progress?

[Herbertkabi]

hi InventIt,
Nice work,
but
Im bit baffled because bearings arragement you use.
Why you do not use DB ( Duplex Back-to-Back) arrangement???
Is it face-to-face arrangement?
Or do I see wrongly?
And Grease - what it is?
I have the same looks in Garage - it is exteme good for boats, cars ...
but never for Spindle!
Im wrong again?

Cheers,
Herbert,

Some of my spindles:
http://www.cnczone.com/forums/showth...t=12184&page=5
http://www.cnczone.com/forums/showth...t=72691&page=2

Now Im making taper 30 spindle, again direct drive, not so high speed - just up to 15k RPM, but planned with automatic toolchanger. Was very hard and long time looking for adequate spindle shaft - finally got it - German made, high quality