I've been looking for a X3 belt drive conversion for some time because I would like a broader rpm range for this machine. Something similar to the X2 would be preferable. I'm away from home for about another month so designing the conversion myself before school starts up again would be a bit of a problem. Also, I am not sure how to find the way to figure out what the proper size of pulleys I would need and how I would go about making them. The biggest problem wouldnt be the pulleys, I know how to machine those, it would be the keyways which are a mistery to me. And yes, I have seen the "ArcEuroTrade.Com" pdf file but I would like to get rid of the gears so that I can expand the rpm range and quite the machine. Any suggestions. Thx

I've been looking for a X3 belt drive conversion for some time because I would like a broader rpm range for this machine. Something similar to the X2 would be preferable. I'm away from home for about another month so designing the conversion myself before school starts up again would be a bit of a problem. Also, I am not sure how to find the way to figure out what the proper size of pulleys I would need and how I would go about making them. The biggest problem wouldnt be the pulleys, I know how to machine those, it would be the keyways which are a mistery to me. And yes, I have seen the "ArcEuroTrade.Com" pdf file but I would like to get rid of the gears so that I can expand the rpm range and quite the machine. Any suggestions. Thx

Well for RPM figure what the machine can turn and figure how fast you want it. Say it turns 500 RPM and you want 2000 RPM Small pulley 4" and larger on 12" put the big one on the motor and the small one on the spidle.

The Keyway you need to buy a "Broach" they run around $45.00 for both part.

Smitty

Well, after the less than stellar response to this thread I have decided to make the thing myself. However, before I can start to purchase materials I need to know the pulley diameters. I intend to design and mount the motor just like this gentleman has done on his x3: http://homepage3.nifty.com/rockhill/index.htm.
I dont intend to replace the motor so what I need to know is, how fast is the motor turning at max rpm. I cant find the info on the motor itself nor in the manual pages. So help with this would be appreciated.

Well, after the less than stellar response to this thread I have decided to make the thing myself. However, before I can start to purchase materials I need to know the pulley diameters. I intend to design and mount the motor just like this gentleman has done on his x3: http://homepage3.nifty.com/rockhill/index.htm.
I dont intend to replace the motor so what I need to know is, how fast is the motor turning at max rpm. I cant find the info on the motor itself nor in the manual pages. So help with this would be appreciated.

I believe that the max motor rpm on an X-3 is 3750 rpm - I think I've seen it in the manual of Grizzly's version of the X-3, and it's what I used to try and figure out my pulley sizes - I have an X-3 motor on an X-2 head. I have a 1.5:1 pulley ratio to give me about 5500 rpm top speed.

Thx digits. I will use those numbers than in figuring out the pulley ratios.

Smitty,

Don't you mean 16" for the larger pulley?...

Jordan

Thx digits. I will use those numbers than in figuring out the pulley ratios.

Here's the link to the manual page I used - I can't guarantee that your motor has the same specs as the Grizzly one though - use it at your own risk...

http://www.grizzly.com/products/G0463

Smitty,

Don't you mean 16" for the larger pulley?...

Jordan

Jordan,

Your right, unfortunatly I talk/type without fully thinking. It could have been 1/3 reducer also. LOL

Smitty

Look at the last pdf on this page, its a belt drive mod for the X3, with pulley sizes etc.

http://www.arceurotrade.co.uk/projects/X3-CNC/index.html

Look at the last pdf on this page, its a belt drive mod for the X3, with pulley sizes etc.

http://www.arceurotrade.co.uk/projects/X3-CNC/index.html

The mod that Dick Stephan did was mainly to reduce the gear noise - it had little effect on spindle speed. Note also there are still the High/Low gear sets which are inside the main head casting.

The stock motor runs about 4000rpm, I am thinking of a 3 pulley direct drive and bypassing the gears completely.

Low............ 8:1
Med............ 2:1
High ........... 1:1.25

This gives 50-500 in low
200-2000 in med
500-5000 in high

i have to wonder what the life expectency of the bearings would be at these increased speeds...

5000 RPM is right at the upper limit for the OEM X3 spindle bearings. However most people are not going to be running the machine 40 hrs/wk like a business would so even at these speeds they should get many years of service.

Replacement with a higher quality aftermarket bearings would let you run 7000 RPM all day long if the bearing bores and shafts have the exact press fits Keep in mind this machine was made in a factory in China that has only 1 CNC tool, a FADAL mill. All these shaft parts are run on manual equipment.

So YMMV, and good luck. :)

So going on those numbers, what are the diameters of the pulleys. I intend to get rid of the gears. Also, when figuring out the diameter, you are going to use the smallest diameter of the pulley right? So for instance, with the one from stirling steele for the minimill, you would measure at the smallest diameter correct of each pulley ring. I intend to use the higher two ratios u suggested. The 200-2000 and the 500-5000. So what would the diameters be?

First I will state that ALL MY design criteria is based on the application of the machine as a metal cutting mill.

I have not fired up SolidWorks yet for that part of the conversion as the spindle is the last item on the conversion list.

I broke the speed ranges into 3 groups to be sure there would be enough torque available at chosen RPM's with overlap. I am keenly aware of the fact the standard motor is optomistically rated at 3/4HP and that the speed control will cut out if overloaded.

I chose the 500-5000rpm high range so as to run small tools at light loads 1/4" or 6mm endmills or smaller. Likewise the low range was to provide an ample margin of torque without overheating the motor or controller.

Now all this torque needs to be transfered by a proper belt that is meant to be run with this type of load. This rules out Vee type belts or the round O-ring type. I would say that you need either a serpentine type belt or a toothed timing type belt. Vee belts are rated at the total load but work poorly when transfering high torque at very low RPM.

I will be using a timing belt because I will require positive drive for rigidtapping. However the serpentine type is easier to cut to exact diameter to make the speed ratio you want. With the timing belts it comes down to tooth ratios.

Another option I am seriously looking at involves dumping the entire OEM spindle motor and speed controller and replacing with a 1.5hp 6000 rpm unit.

Okay, so I still need a couple questions answered that werent. I intend to use a v belt because I tend to use 1/4 inch endmills and smaller to have as little material waste as possible so I typically use the higher speeds. I have never used the lower rpms for boring or high torque applications so I feel that the vbelt would be sufficient. I have used the minimill belt drive and it worked dandy. Now, for the diameters, I am going to be using the inside diameter of the pulley as my measurement for the diameter correct. Not the outside diameter?

Well, the belt first prototype belt drive is all done. It works like a charm. I set the two pulley size at 2 to 3, 3 to 2. This gives me a high range of about 6000 rpm for using the small carbide endmills, such as 1/8in and 1/4in. And around 2400 for any drilling and such. I did try to drill using the belt in the high range and it was completely unsuccessful. I was using 8mm drill bit into aluminum and I had to change the feed rate to 1ipm. It was ridiculous and is not conducive to long bit life. I had to because I was not finished with the new spindle pulley and wanted to get my fixture plate going while I was making the new pulley. Im going to post some pictures of this version which is kinda makeshift and will post some other pictures when my new one is done.

I do have one concern, my lathe abilities have proven to be extremely inadequate when it comes to making precision components. The inner diameter to fit on the spindle is about .010 to big. Using the smaller 2 inch diameter belt area it is not a concern, using the larger 3 inch belt area it is. This is because the pulley actually moves on the spindle and cause a great deal of vibration. So I need to redo this for a third time to make the inner bore a nice tight fit. I also need to find a keyway maker because using a file to make a 1.375 inch long keyway sucks big time. I also should mention that I am using the longer belt from littlemachineshop.com, the one that fits the grinder, and it works perfect.