Adding a High Speed Spindle to the Mill

[Nick Hulme]

The drive option I chose when converting from a problematic DC Drive and Motor left me with what seemed a very reasonable 0 - 7000rpm on my little benchtop CNC mill.
When I came to do some engraving I found that my feeds & speeds calculator was constantly warning me that feed speed had been limited because of the maximum rpm of my mill, a little investigation led me to the conclusion that a top end of at least 32000rpm was desirable and what you see in the photo is the result.
I'll add some detail in a later post as I've not yet figured out how to insert an image mid-post.

 

[Nick Hulme]

The spindle that's fitted to the L-Bracket is one I built around the basic principles from Spindles by Harprit Sandhu, to simplify constuction I used an eBay sourced ER11 collet chuck on a 10mm shank then dropped into the local bearing shop and asked for some 10mm ID ball races that would run at 35000rpm.
The outer housing is just a lump of aluminium bar stock drilled through 12mm and bored at the bottom to accept 2 ball races and at the top just 1 with room for a little endfloat.
To assemble the spindle I used Bearing Fit to bond the bottom two bearings at the chuck end of the 10mm shank, once this set I bonded the bottom two races into the housing and bonded the ID only of the top bearing onto the shank, sliding it into the housing with a hand push-fit, the pulley, from the same stock as the housing, is retained by 3 grub screws at 120 degrees. It's run at between 28000rpm and 32000rpm for around 16 hours so far so I'm guessing it's a good 'un.
The drive belt is round Polyurethane belting which I cut to length and welded with a cigarette lighter flame.

- Nick

 

[petertha]

It never occurred to me to run the spindle off the main drive like that with a belt. On my 'one day' list I figured I'd get one of those ebay DC powered units & rob the power supply electrics off my RC inventory..

I have that 'Spindles' book by Sandhu too. But in the end I haven't built anything. I kind of got the impression the angular contacts were the way to go just based on his Good/Better/Best type description, but he shows other options using regular bearings & anti-endplay compensation. I'd like to learn more about what you selected, how you built it, lubrication etc. One day I'd like to make some spindle cartridges.

 

[Vixen]

I have often thought about mounting a Dremel 225 flexible extension onto the side of my mill for light engraving work.
The Dremel 200 series Multitool runs between 15,000 and 35,000 RPM and has a 125 Watt motor and a small collet chuck.
This could avoid a great deal of work making a high speed spindle and a special spindle drive.
Has anyone out there tried this route?

Mike

 

[Nick Hulme]

I used to use a Rotozip Rebel on my manual mill giving me 24000rpm and 30000rpm but I'm not sure it would be good for the run times that a 3 Phase motor and a pulley driven spindle with larger bearings will give -

 

[Blogwitch]

http://www.jerry-howell.com/HS-Spindle.html

John

 

[goldstar31]

Probably the simplest solution is to make a 43mm collar to fit either the saddle of the lathe or the vertical slide. Yes, it will all move to a mill.

Amongst my workshop tools are cheap usually Chinese drills with 43 mm collars One of my earliest ventures was a Bosch POF45 wood router. Examination of the instructions revealed that mine had started life as a tool post grinder.

For about £30, one can buy and shorten the pillar of a cheap desktop 'Chinese' drill.

Incidentally, there was considerable correspondence on using routers to make the motive power on homemade tool and cutter grinders.

For what it is worth, I threw out the scrap dental drills which my late wife brought home from her surgeries.

Norman

 

[Nick Hulme]

That's a cute little do-dad John, it would be really handy if one modified the design and built it to take ER11 collets,

- Nick

 

[Blogwitch]

Nick,

As I have a nice collection of no backlash 24 volt high speed precision Swiss motors, I was hoping to do something similar with my CNC build (much later).

ER16 was in my thoughts as that is what will be used on my X2 cnc mill, what will do a lot will also do a little, but not the other way around.

John

 

[petertha]

http://www.jerry-howell.com/HS-Spindle.html

John

Very intriguing. I really like that the motor is off to the side on a fixed plate so adaptable to different motors. The spindle within the main R8 arbor is also very cool. I would much prefer an ER collet arbor too, that would solve the inevitable availability of non-3/16" shanked tools, metric cutters, even centering indicators for that matter. I guess the only way to gage how adaptable the design is get the plans.

The spindle is designed to accept 3/16" shank diameter end mills which is common for end mills from 1/32" to 3/16" diameter. The spindle body is mounted in a standard 3/4" or 7/8" R-8 collet. The unit is adaptable to a wide range of modifications to suit any user. The plans set also includes an oversize computer grade precision lower ball bearing, a high quality upper ball bearing and a bearing preload wave washer.

 

[Blogwitch]

Peter,

I was thinking along the lines of because it fits INTO the main spindle and not hanging on the side of the head, it would be a much easier setup if using it with CNC. You would set it up just like your normal low speed spindle rather than having to allow for the offset of a motor on the side.

I might be right, I might be wrong, but whatever way, I will eventually get one made and try it out, and besides, I will be able to use it on my normal mill as well.

I would also consider than rather than making it to fit into an R8 collet, I would use a soft ended blank solid R8 collet and build the unit into that, the less joints and bits the better. I made a special fitting for doing such modifications with my 5C collet chuck on my lathe.

http://www.homemodelenginemachinist.com/showthread.php?t=24125


John

 

[Nick Hulme]

I was thinking along the lines of because it fits INTO the main spindle and not hanging on the side of the head, it would be a much easier setup if using it with CNC.

John,
If you plan your CNC jobs such that a known datum is always available to you and is never machined away durring machining, having an offset engraving and micro-machining spindle isn't an issue.
Planning work this way also means that re-work and picking up where you left off in the event something unforseen occurs are straightforward procedures.
You also have the option to set up a test piece and drill a small hole with each spindle and measure the offset, this will be fixed and can then be quite simply used in your machine controller's settings,
Regards,
Nick

 

[Blogwitch]

Nick,

Thanks for the info.
I have yet to build the mill and learn how to control it, so I just tend to think logical at this time.

But I will still make one as it will allow high speed milling on my Chester 836, which only goes to 2k rpm using it normally.

John

 

[Nick Hulme]

This is something I'm working on with the high speed spindle, I'm just prototyping at the moment, it's in phosphor bronze, the central ratchet is 7.8mm across point to point and the pocket is 1.1mm deep

Edit - I forgot to mention the job is pocketed using a TC 0.8mm 2 flute endmill at 28800rpm

 

[goldstar31]

Might I comment please?
I've just returned from the local Aldi in the UK and come out with mini bench grinder with a variable speed to 9,000+ revs and with a flexible drive and accessories. Price at £27.

Worth a look?

Norman

 

[Nick Hulme]

Might I comment please?
I've just returned from the local Aldi in the UK and come out with mini bench grinder with a variable speed to 9,000+ revs and with a flexible drive and accessories. Price at £27.

Worth a look?

Norman

Anything is worth a try,

- Nick