design of a drill spnidle

[marmon]

I need to create a somewhat small spindle that will hold a chamfer tool on one end needed to chamfer hundreds of holes inside of a ring approximately 20" in dia. This spindle will be mounted to a plate and driven via belt. Once mounted I will have control of the z-axis movement (spindle up-down). The ring will rotate via a chuck that is also controlled, so I will have an automated chamfering process. My question is, I was hoping to use standard cup/cone trailer axle bearings opposing each other for the spindle. I would mount a collet for the tool to one end of the shaft and a drive pulley to the other, The shaft would have a threaded area to snug up the bearings just like an common trailer axle. Rpm will be approx. 250rpm, I do not know the axial force, but the holes being chamfered are 3/8" dia, with an Rc of 50. I will use solid carbide for the tool which requires rigidity to keep from chipping. Is the cup/cone arrangement a good idea since almost all the force will be axial? or is there another bearing that may be more suitable for a spindle?

 

[BrianE22]

For sure you would want to pre-load them. Carbide tools don't like any looseness.

 

[lukin1977]

Can you provide a schematic drawing?

 

[marmon]

this is what I was planning on making for the spindle. Hopefully this bearing arrangement works

shaft size is 1-1/16" for scale

 

[lukin1977]

That could work but if I were you I will do it differently:

From your explanation I understand that axial force will be from left to right only so the cup/cone bearing at the right wont be supporting any axial load. I will put a ball bearing (with bore smaller than 1-1/16") at right side to hold some axial load and to increase the radial resistance of the whole assembly

I would not use a nut either. I will install a circlip

See attached file

 

[marmon]

Thanks for the suggestion, do you think a deep groove ball bearing would suffice, such as a 6205?

Also I need zero slop in the system axially, that's why I thought a nut would work well, so I can give zero clearance on the cup/cone bearing

 

[lukin1977]

6205ZZ or 6305ZZ will be fine

 

[BrianE22]

What you have looks fine. You definitely want axial pre-load and the common way to do that is with tapered roller bearings or angular contact bearings. Adjust the nut so your pre-load is a bit higher than the anticipated axial load.