[Azalin]

Hi,

Main idea is to build a spindle (simply a smaller version of the BT30 I've built before) for router and smaller milling machines. This spindle will be as lightweight as possible but robust, ATC compatible, power drawbar etc. My initial thought was to build over ISO20 tooling, but I'd like to know if there better tooling options in that size.

Any input will be appreciated.


Thanks,
Suat

[handlewanker]

Hi Azalin, my Skyfire SMV-0 mill has an ISO 20 taper.....when I ordered the mill from China I also ordered 10 tool holders with ER32 chucks mainly because there is nothing on EBAY to suit or cheap enough.....there are some ISO 20 tools with I think ER20 chucks but they're quite expensive.

The spindle is timing belt driven by a 1 HP BLDC motor....one pulley is fixed on the motor and two different sizes for the spindle to vary the torque and/or speed.....max speed is 7,000 rpm.

The power draw bar was electrically activated by a motorised thruster....worked very well while it was working..... but the motor failed and now for the time being I have a simple manual push down bolt on the top of the draw bar housing.

My own preference for a spindle I am building is a sealed double row angular contact bearing top and bottom with a spacer tube between the inner races and a nut on top of the pulley to apply preload etc.

The bottom bearing is fixed in the housing and the top bearing is allowed to float end wise in the top of the spindle body bore.

There is also a bearing retainer cap to hold the bottom bearing in the spindle bottom end.

Being sealed there is no need to have a seal at the bottom or top as the bearings are sealed for life.

On the subject of the ISO 20 taper I would have preffred to have an R8 taper....this is much more compact for height gain but I don't think it would lend itself to ATC. very easily...….the collets are quite long, but for manual tool changing it's a winner.
Ian.

[Azalin]

Hi Ian,

What type of a pull stud gripper has your ISO20 spindle? Jaw type or ball type?

[handlewanker]

Hi Az....it's a jaw type ….according to Defeng, the builder and supplier, it's a better gripper than the ball type.....photo attached of the ISO 20 tool holder with ER32 chuck and drawbar end.
Ian.

[Azalin]

Thanks Ian.

The tool holder in the photo has a pocket for spindle dog. Does the spindle have dogs? I'll be surprised if it has.

[handlewanker]

Hi....LOL, I had to go out to the garage to see what the spindle end looked like.....it only has a series of small holes around the spindle end, probably for balancing etc but no slots for drive dogs.

I can't think why the tool shanks have the drive slots.....probably part of the ISO design for 20, 30, 40 and 50 etc.

I doubt whether it's necessary to have any positive drive means, just the grip of the taper, as the cuts on this mill are small by comparison with a mill with a heavier work envelope capability.

For an ATC capability you wouldn't want to have to align drive dogs where they're not needed.

It goes without saying that the spindle taper and the tool shank taper needs to be hardened and ground.

I also subscribe to the idea that CNC machining is lots of small shallow cuts rather than attempting to hog material off like a manual mill even if the cutter is a large diam etc.....feed rate in proportion etc.

That is a two edge approach by my reasoning as it doesn't stress the mill and you only wear out the first 2mm of the cutter end which makes it easy to just cut the end off the cutter and resharpen it.....so what if it takes a bit longer to do.

I quite often do this by hand on the bench grinder (just the end face), same as grinding a drill etc.....the rest of the cutter flutes are unworn edges and it still retains the diam.
Ian.