Can a BP R2E3 handle a 3HP spindle motor?

I just got my R2E3 up and running and I noticed that the largest end mill I can get it to realistically handle is my 3/8, 4 flute carbide end mill. Cutting regular hot roll steel I can take about .5" depth of cut and about 50% width of cut before I hear the RPM's start to suffer too much. So, I figured my cubic inch per minute removal rate was simply .5"(.1875")(24") = 2.25in^3.

I don't know if that is actually decent for this machine or whether its lame-o slow-mo. The next thing that popped into my head was kicking the 2hp motor to the curb and upgrading to a 3hp motor . I imagine my removal rate would go up at least another 30% with the added power. But now I am wondering if the company that made these mills had in mind a little over engineering to handle higher powers of whether it would start to tear itself up with the 3hp motor. Any thoughts?

Here is a video that I uploaded of my machine working on that piece of hot roll.

F14 said:

The next thing that popped into my head was kicking the 2hp motor to the curb and upgrading to a 3hp motor . I imagine my removal rate would go up at least another 30% with the added power. But now I am wondering if the company that made these mills had in mind a little over engineering to handle higher powers of whether it would start to tear itself up with the 3hp motor. Any thoughts?

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Ummmh... well, actually? None, really.

You might want to have a few more of your own first.

TWO HP was "over-engineering".

Monarchist said:

Ummmh... well, actually? None, really.

You might want to have a few more of your own first.

TWO HP was "over-engineering".

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Sure, I have had plenty of thoughts about it. I could go the more technical route and start to disassemble the machine and calculate how much deflection there would be in the spindle shaft with higher loads applied to it. I may also run a battery of tests on the Vari-Speed system for possible instability. If proven unstable, then I could also go direct drive to remove it as a potential problem down the road.

Before making the attempt to reinvent the wheel here, I was just curious to see if anyone has heard of it being done or know of any successes / failures or possible lack of longevity in placing that kind of demand on the hardware.

Are you saying that two HP was already considered to be the upper limit of what the mill could handle? If so, then what would be the limiting factor in only allowing that amount of power in the system?

I don't have the technical manuals on this mill, but it seems that it was built more sturdy than one of those pivoting ram style J-head machines. Being a solid ram, I know that is in my favor.

I don't generally take the mill above 3,000RPM because I find that unless I am running even smaller end mills that could benefit from the increase in RPM, then there is no advantage in taking it higher. I will loose too much torque.

The bearings in the quill / spindle are in good shape and are likely able to withstand several thousand pounds of load before any inclination of a failure can be expected from them. I hear more often that it is over revving the spindle that can cause bearing failure mainly due to the total loss lubrication system that is not able to keep up with the generated heat. Some say this is possible at speeds over 5,000+ RPM and some others claim more like 6,000+ RPM. Nobody had mentioned the possibility of just applying another foot pound or so of torque on system to achieve higher metal removal rates.

The two HP motor that came with my mill is actually rated for up to three HP by a simple increase in frequency and power. But, doing that would limit the duty of the motor to 30min max and also force me to get a device that can adjust output frequency such as a VFD. I would also start to loose the lower end of my operating RPM with that motor operating at a higher frequency. If not, then I could risk overheating the motor by forcing a lot of amps through it at a lower frequency.

My hypothesis is that I may be able to see some benefits from a 3HP motor such as a slightly improved metal removal rate and less of a drop in RPM when under load.

With all of this being said, I only be willing to try this idea out if I felt that there would be no obvious indicators of trouble. The only thing I heard that could be problematic is the Vari-Speed system that came with the mill. I have not had any trouble with mine, but I generally keep it set in one place unless I am doing some drilling or boring or something like that.

You sound like an engineer by trade. No machinist with dirt under their nails would ever use the word "hypothesis", or give that detailed of analysis for swapping a motor on their knee-mill. No offense, just an observation...

I don't know what an "R2E3" is exactly, but based on your description and the video, I'm guessing it's a standard Bridgeport Series-1 mill with a CNC retrofit?

3hp on a Bridgeport? I would do it if I had a cheap 3hp motor, and the time to tinker with it. The extra torque would be useful for drills 5/8" & larger.

If you are wanting more heavy metal removal "hogging" power, then use some of the old HSS corn-cob endmills - they really are the best option for a weak machine like a Bridgeport. Put the machine in low gear, 300ish RPM, go .100-200" wide, full depth. Put a wrench on the handle so you can feed it smoother, and feed it as hard as you can until the motor bogs. It's tough to out-do one of these cutters on a knee-mill.

An R2E3 is a boss 8. If you've got one that's running, you're already way ahead of the game. You are aware that the spindle motor shaft is way long and is part of the very-drive assy? You can't just throw in a bigger motor.

With the cut condition described, I suspect the Vari-Drive may be slipping causing the apparent slowdown of the cutter. New belt? Good spring?

F14 said:

My hypothesis is that I may be able to see some benefits from a 3HP motor such as a slightly improved metal removal rate and less of a drop in RPM when under load.

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This is NOT "new ground" that requires even two minutes of "engineering" calculations. They were done ages ago by many, many others, then tested out in the world, all OVER the world, Milwaukee to Milan, etc.

Just go and look at as many other vertical mills as you can find photos and specs for.

They get larger and heavier as power goes up, and there are LOTS of examples of that.

Bee Pee look-likes alone include MANY machines with far, far heavier build.

What do you know that those makers - and their USERS - have MISSED the past seventy years and more?

Monarchist said:

This is NOT "new ground" that requires even two minutes of "engineering" calculations. They were done ages ago by many, many others, then tested out in the world, all OVER the world, Milwaukee to Milan, etc.

Just go and look at as many other vertical mills as you can find photos and specs for.

They get larger and heavier as power goes up, and there are LOTS of examples of that.

Bee Pee look-likes alone include MANY machines with far, far heavier build.

What do you know that those makers - and their USERS - have MISSED the past seventy years and more?

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I would highly doubt that I would know more than people that have actually taken the time to modify and test different pieces of equipment. Their results would be real world and could serve as the benchmark for what works and what does not. I have seen a few other knee mills that run three and four HP motors. They also tend to weigh a few thousand pounds more than what I have, as you have mentioned with a "far heavier build".

My aim here is to just gather some advice from people that have been in this industry for a while and get their input. Perhaps someone really knows these R3E3's and could save me a lot of time and money by providing me with a set of realistic expectations that I can abide by.

I find machining fun and I have taken a liking to this mill of mine. A lot of that is probably due to the fact that I have been trying to get it retrofitted for the past several months. So, to finally see it in a operational state is rewarding for me. Then I get to where I just can't leave it alone and I want to try to improve on it where possible.

Just the other day I installed magnetic scales that can give one micron resolution. I did it because I thought that attaching scales directly to the table and quill would be a improvement over those encoders that attached directly to the servo motor shafts. The servo encoders would sometimes have noise issues and cause the controller to count pulses when it was not supposed to. Noise issues have plagued my retrofit...

Anyway, so naturally I like to improve the machine where I can.

That is a definite possibility. I could not tell if the drop in noise frequency was the sound of the motor slowing down, or the cone pulley sets starting to slip. Truth be told, I have not taken apart the head of this machine to find out. I still need to get a decent set of instructions that can show me how to maintenance that Vari-Speed system.

When I bought the mill, It seemed to be in pretty good shape mechanically. The ways are in excellent shape and that was my main concern when I decided to buy it. Seeing that the ways were in good shape gave me some confidence and I shelled out some coin so I could take it home. But, of course that does not guarantee that the head is without issues. I just made sure it did not sound like it was gargling marbles when I fired it up.

Larry Dickman said:

An R2E3 is a boss 8. If you've got one that's running, you're already way ahead of the game. You are aware that the spindle motor shaft is way long and is part of the very-drive assy? You can't just throw in a bigger motor.

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I did see from some eBay listings that the standard two HP motors for the R2E3 have pretty long shafts. If I ended up going through with it, I figured it would be OK to make a shaft adapter on another motor and turn that adapter out of something fairly stiff like 4140. I would imagine the adapter would have to be something like a light press fit, otherwise the pulley moment would make the shaft adapter beat the hell out of the motor shaft with any possible play that is given to it.

I don't know if there is actually enough room to fit some sort of adapter up there on the head. Just an idea of mine.

Looks to me like you were taking a 75% WOC at 1/2" DOC when the spindle complained.

You calculated your max HP at 89%, I don't know what more you want.

I'm assuming that you retrofitted the control and are running it with some PC based control; I wouldn't worry about 2HP being enough, just run HSM toolpaths and get past it.

F14 said:

I would highly doubt that I would know more than people that have actually taken the time to modify and test different pieces of equipment. Their results would be real world and could serve as the benchmark for what works and what does not. I have seen a few other knee mills that run three and four HP motors. They also tend to weigh a few thousand pounds more than what I have, as you have mentioned with a "far heavier build".

My aim here is to just gather some advice from people that have been in this industry for a while and get their input. Perhaps someone really knows these R3E3's and could save me a lot of time and money by providing me with a set of realistic expectations that I can abide by.

I find machining fun and I have taken a liking to this mill of mine. A lot of that is probably due to the fact that I have been trying to get it retrofitted for the past several months. So, to finally see it in a operational state is rewarding for me. Then I get to where I just can't leave it alone and I want to try to improve on it where possible.

Just the other day I installed magnetic scales that can give one micron resolution. I did it because I thought that attaching scales directly to the table and quill would be a improvement over those encoders that attached directly to the servo motor shafts. The servo encoders would sometimes have noise issues and cause the controller to count pulses when it was not supposed to. Noise issues have plagued my retrofit...

Anyway, so naturally I like to improve the machine where I can.

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Here is a picture of how I mounted the X and Y scales to the table. I simply used the limit switch box and associated table cams as mounts. It worked out pretty well.

F14 said:

I did see from some eBay listings that the standard two HP motors for the R2E3 have pretty long shafts. If I ended up going through with it, I figured it would be OK to make a shaft adapter on another motor and turn that adapter out of something fairly stiff like 4140. I would imagine the adapter would have to be something like a light press fit, otherwise the pulley moment would make the shaft adapter beat the hell out of the motor shaft with any possible play that is given to it.

I don't know if there is actually enough room to fit some sort of adapter up there on the head. Just an idea of mine.

Click to expand...

Give some thought to the fact that you HAVE CNC.

Many cuts, light if they must be, are not a failing. They are a STRENGTH of CNC goods in general.

'coz it can do them FAST and very repeatably as to accuracy.

CNC doesn't get tired, distracted, bored, nor so pissed-off as to quit and run off with a cocktail waitress over having to do repetitive work.

Plan for that and put it to advantage. It is what your machine was meant to do.

I'm going to stay out of the rest of the discussion, and address just this bit:

F14 said:

I figured my cubic inch per minute removal rate was simply .5"(.1875")(24") = 2.25in^3.

I don't know if that is actually decent for this machine or whether its lame-o slow-mo.

Click to expand...

For a machine with 2HP at the motor, cutting steel, that's quite a good metal removal rate. The unit power (HP per cubic inch per minute) for milling steel varies with the hardness of the steel and the condition of the cutting tool, and the usual range is 1.0 for soft steels and sharp tools through 2.2 for Rc45 steels and dull tools, and can go as high as 3.5 for hard milling of stuff close to Rc50. So if you were getting through 2.25 cubic inches of steel per minute with the available HP, you were doing as well as can be expected.

With aluminum or magnesium, expect 2 to 3 times the steel metal removal rate. With cast iron, expect "somewhat more" than the steel rate, but just how much will depend on the type and condition of the cast iron. Perhaps 30% more for nice soft grey irons. White irons may be unmachinable altogether!

Tables of unit power for various machining operations can be found in most machine shop practice textbooks.

sfriedberg said:

I'm going to stay out of the rest of the discussion, and address just this bit:
For a machine with 2HP at the motor, cutting steel, that's quite a good metal removal rate. The unit power (HP per cubic inch per minute) for milling steel varies with the hardness of the steel and the condition of the cutting tool, and the usual range is 1.0 for soft steels and sharp tools through 2.2 for Rc45 steels and dull tools, and can go as high as 3.5 for hard milling of stuff close to Rc50. So if you were getting through 2.25 cubic inches of steel per minute with the available HP, you were doing as well as can be expected.

With aluminum or magnesium, expect 2 to 3 times the steel metal removal rate. With cast iron, expect "somewhat more" than the steel rate, but just how much will depend on the type and condition of the cast iron. Perhaps 30% more for nice soft grey irons. White irons may be unmachinable altogether!

Tables of unit power for various machining operations can be found in most machine shop practice textbooks.

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Thanks for the information . Going by what you said, is there any particular book that you would suggest as a good reference for me?

Monarchist said:

Give some thought to the fact that you HAVE CNC.

Many cuts, light if they must be, are not a failing. They are a STRENGTH of CNC goods in general.

'coz it can do them FAST and very repeatably as to accuracy.

CNC doesn't get tired, distracted, bored, nor so pissed-off as to quit and run off with a cocktail waitress over having to do repetitive work.

Plan for that and put it to advantage. It is what your machine was meant to do.

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I can't argue with that at all. Your absolutely right. Perhaps I do need to just leave it alone for a bit and just have some fun with what I have for a little while.

F14 said:

Is there any particular book that you would suggest as a good reference for me?

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I like Karl Moltrecht's 2-volume set entitled Machine Shop Practice, but there are other good choices.

Perry Harrington said:

Looks to me like you were taking a 75% WOC at 1/2" DOC when the spindle complained.

You calculated your max HP at 89%, I don't know what more you want.

I'm assuming that you retrofitted the control and are running it with some PC based control; I wouldn't worry about 2HP being enough, just run HSM toolpaths and get past it.

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That's correct. I did retrofit the machine with a standard desktop computer. Although very nice, I could not justify the cost of going with Centroid for a retrofit.

This is good information. I was wondering if the wanting to put a more powerful motor on the machine would be unreasonable or not. The fact is that it will mill things out on it's own and do it just fine. Before I bought this machine, I was looking at wanting a Sherline mini mill. I tend to machine parts about the size of my hand, so I believe I would have been disappointed going with that brand. Glad I got the R2E3 even if it does weight 3000lbs.

F14 said:

Before I bought this machine, I was looking at wanting a Sherline mini mill. I tend to machine parts about the size of my hand, so I believe I would have been disappointed going with that brand. Glad I got the R2E3 even if it does weight 3000lbs.

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"Sherline?" Now THAT is .. f*****g hilarious !!!

Sure hope you don't go as "upgrade greedy" on timepieces or London's "Big Ben" will need some serious tailoring to your Levi's to serve as a pocket watch...