Re: [CAD_CAM_EDM_DRO] Re: High Speed Spindle

Hi Steven,

I recently built a spindle for my Series 1 Bridgeport. I made the body
from scratch. The taper was a bit of a pain but for this job it doesn't
have to be perfectly accurate. Once the taper is done the rest of the
machining can be done with the spindle of the mill, with a boring bar
held in a vice on the table. The bore has to come out concentric that way!

I also used an 300DA extension chuck, shortened and with a pin pressed
into the end for a small needle roller to run on. By the way those
chucks are pretty hard. I wore out a brand new cobalt hacksaw blade when
I shortened it. The thrust and most of the cutting forces are taken by a
ball bearing close to the collet end.

My bearing was a close sliding fit so I used a drop of loctite to make
sure the shaft didn't spin in the bearing. Drive is via a toothed belt
from a small cheap router. Toothed belt is pretty noisy at these speeds
but it has the advantage that you can use small pulleys without slipping.

I have used it for quite a few jobs now including engraving and drilling
PCBs. It works very well.

Les

Steven Ciciora wrote:

> Great minds think alike? Since getting a series II B-port, not enough room
> for my home made router table. I've committed to giving it to my Uncle as
> soon as I can get the B-port to do everything the router table did. I
> mostly made 1/8" aluminum panels for electronic chassis work, using a
> harbor freight trim router at around 30k rpm, with 3/32" used carbide PCB
> drill bits. I would hope I have the skills to make a high speed spindle
> for the B-port that is at least as good as that setup :-)
>
> What I'm considering is the same 300 series DA collet chuck (can buy
> collets from 1/64" to 1/4"), some type R8 bearings from McMaster carr (1/2"
> shaft ID, 1 1/8" bearing o.d., 28,200 max rpm, see P.N. 60355K15)) and a 1
> 1/8" Kwik-Switch End Mill Adaptor (to fit my b-port). Motor would have to
> be mounted outside of this spindle, belt fed. It is my understanding that
> most collet extensions are undersize, just like end mill shanks are
> undersized. If necessary, I wonder if the collet extension can be plated a
> few tenths of a thou for a press fit on the bearings? I'd be really
> interested in hearing how well turning down the collet extension works. Is
> it hardened? How hard to machine without greatly increasing the run
> out? Remember, I only want _at least_ as good as the $20 harbor freight
> trim router :-)
>
> I imagine inside the end mill holder would be a bearing spacer. Some end
> mill holders have a threaded portion at the other end that I believe serves
> as an indexing stop for setting end mills in. This could be used for
> putting some pre-load on the bearings. I'd also need to figure out how to
> keep the assembly from falling out the bottom end; I don't mind welding
> something there if I had to, or I'm not sure if I can use the end mill
> setscrew.
>
> I imagine tapered roller bearings would be better, but I have not found any
> that had O.D.s and I.D.s that wouldn't require precision machining from me.
>
> I hope this discussion continues, because there is a lot I don't know and
> would like to benefit from the experience of others.
>
> Thanks,
>
> Steven Ciciora
>