[GreatNorthGnome]

Hey guys, Ive been starving for some more rpms. I typically use 1/4" endmills for my little aluminum projects, but 2400rpms isn't enough.
I've read the stock bearings can handle 3800 if you gear it? That may be the easiest option.

However I am curious about two others, can any one give me any info on using the stock motor and speed controller for a new high speed spindle set up. If I built my own milling head and spindle, then geared the stock motor to drive a spindle at 6000rpm for example, would and could the speed controller/motor handle that?

Second idea, variable speed 1/4-1/2" router. While I see most sit around 8-16k rpms, can any one comment on the life span of a router being used to machine aluminum?

I should mention I'm not really in the market for engraving, I just want to drive my 1/8-1/4 endmills a little closer to their proper speeds in aluminum.
Thank you so much.

[hoss2006]

You'll find a few ideas here, from gear mods to belt drives.
http://www.g0704.com/Projects.html
Hoss

[wizard]

Hey guys, Ive been starving for some more rpms. I typically use 1/4" endmills for my little aluminum projects, but 2400rpms isn't enough.
I've read the stock bearings can handle 3800 if you gear it? That may be the easiest option.

One thing to consider with gearing is noise which might become excessive at high speed. Wear is another issue. Personally I'd consider a belt drive or direct drive spindle.

As to bearings and speed don't take some bodies word for it. Hit the web and look up manufactures data for the bearings in question. Top speeds vary widely based on a large number of factors. The other thing is that many of these mills come with less than optimal bearings for the task at hand.

However I am curious about two others, can any one give me any info on using the stock motor and speed controller for a new high speed spindle set up. If I built my own milling head and spindle, then geared the stock motor to drive a spindle at 6000rpm for example, would and could the speed controller/motor handle that?

That is a bit of a loaded question. How hard do you want to drive the mill? Is this a CNC mill? Your best bet here is to do some research with a good speed and feed calculator. You should be able to determin horsepower requirements with a little bit of estimation.

Second idea, variable speed 1/4-1/2" router. While I see most sit around 8-16k rpms, can any one comment on the life span of a router being used to machine aluminum?

Again a loaded question. The big problem with most routers is their open design with the high likely hood of pulling in metal leading to an early failure. High speed router though often need rebuilding simply due bearing wear even if routing wood. It is a cheap solution though even if you toss a router from time to time.

I should mention I'm not really in the market for engraving, I just want to drive my 1/8-1/4 endmills a little closer to their proper speeds in aluminum.
Thank you so much.

This is a big problem on these low cost mills, thus you can find hundreds of different approaches to high speed spindles on the Internet. Your course of action depends upon how much use you actually only need this capability. By that I mean if you never run steel or other hard materials then maybe a more dramatic overhaul would be in order.

If you are sure that aluminum will be the only material cut then it might make sense to build a new spindle with high speed capability. Maybe something with an ER collet and a direct drive motor.

I get the sense though that you want to do this cheap, mainly because of the questions about reusing the old motor and controls. Your best bet here is probably some sort of belt drive upgrade with new bearings in the spindle you already have. I'm not sure if the RPM gains would be worth it though. Say you hit 4000 RPMs, would that be enough for how you intend to use an 1/8" end mill?

[amyers]

+1 on hoss's project page, he's been the innovator of many of the upgrades and has done all the research and testing for you.
am

[GreatNorthGnome]

Sorry for the delay, things have just been a little busy lately.

Thank you for the responses and ideas, this gives me some possibilities to look into.

[GreatNorthGnome]

So here is my solution for now, however I hit a bit of a speed bump.




It was supposed to be a 1:1.16 ratio, however the one pulley wouldnt clear a couple things. So I had to reverse it and run 1.16:1.
So I can get upwards of 4600rpm, but I'll keep it below 4k.

Now I knew it would reverse my spindle rotation, but apparently I've never used reverse on this machine. Why does my machine only run like half rpms in reverse? I just read that this is a common thing on these bf20's? That's unusual so hopefully I can just reverse the motor wires and run the forward option. I ran out of time tonight to try it out.

[Al_The_Man]

Or..JEH - Milling Feeds & Speeds page
Al.

[Al_The_Man]

That's unusual so hopefully I can just reverse the motor wires and run the forward option. I ran out of time tonight to try it out.

It is a DC brushed motor so just swap the motor leads.
Al.

[GreatNorthGnome]

Thanks Al, It is working great now. The extra rpms have made a huge improvement, reduced chip load and the cutter ejects the chips alot easier.

[Mad Welder]

Very, Very Nice innovative approach to the belt drive.

[GreatNorthGnome]

Thank you! Its not as pretty as I wanted, but it works so who cares
I noticed a minor loss in torque which is to be expected, but nothing severe.

[huxleypig]

Sorry for posting on an old thread but I wanted to show you how I have handled this higher RPM problem. My motor says it is rated for 5600RPM and so I have cranked up the pot to go to 4k on the main spindle. I did not want to push the spindle bearings because I am unsure what they are rated to.

Attachment 238992

The main reason I have made this bracket to hold it is so I do not make any modifications to the mill and therefore do not invalidate the warranty. I have a good 11 months left on her yet! It would have been much easier just to drill and tap it straight to the head.

It uses 2 of the 6mm threads holding the top of the head down(it is still keeping the head together, just sandwiching the bracket now), the 8mm thread for the spindle lock (while the secondary is attached I lose the spindle lock option) and the 2 5mm threads that used to be holding the safety guard on.

So far it has worked very nicely!

[Fastest1]

So this is running the extended rpm through the original gear train H/L? I cant imagine how long the plastic gears will last. How is the noise?

[huxleypig]

So this is running the extended rpm through the original gear train H/L? I cant imagine how long the plastic gears will last. How is the noise?

The primary spindle has its extended RPM running through the original gear train but I rarely push it past 3500RPM because I do not know how it might adversely affect those other bits I don't know about. So the spindle bearings and the gearing. I know the motor is fine for up to 5600RPM. It has been fine so far. Do you think that too much of a push for it?

The 24K is coming from the spindle motor mounted to the side.

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