[RichardDeptris]

I don't own a milling machine, but I would like one. I am also a complete Noob learning from YouTube making little money sitting in a cube.

I have two drill presses, a Skil 10" and a cheap Harbor Freight 8". I've taken apart the cheap one to examine it as it is of no use to me anymore. I've decided to turn it into a lightweight milling machine and at some point in the future turn it into a CNC or chuck it for a real one (NPI). I already have a 3/4hp DC motor I salvaged from an old treadmill and I also purchased a 120v PWM motor speed controller.



My idea is to replace the existing spindle inside the quill with a beefy ER20 tool holder and swap out the bearings as well.



I bought an 3/4" diameter ER tool holder from a US seller on eBay at a price I couldn't resist:



DZ Brand 3 4" ER20 150 Collet Extension | eBay





The existing spindle is 12mm and the quill housing has an inside diameter of 32mm. The quill has two 6201 bearing (12mmx32mmx10mm). I couldn't find a bearing matching the same OD with a 3/4" ID. The closet fit I could find was a 20mm x 32mm x 7mm from AST:


71804C Angular Contact Ball Bearings | AST Bearings


I have a few questions.


First, is there a solution available for shimming the shaft diameter from 3/4 (19.05mm) to 20mm? I haven't seen any specific parts for this. If there are no solutions, I can always exchange the tool holder for a 20mm one, which is even beefier or just buy another one of the correct size. As for the missing 3mm from the width of the bearing, I am considering using thrust washers, thrust bearings and or shaft collars to make up the 3mm difference. Will this work? Is there a bearing bore adapter?


Second, the existing spindle has a 4 tooth 3/8" splined section to allow for transfering torque to the spindle while allowing the quill to retract and extend. I will need to somehow reproduce this mechanism. My current thought is to use a 3/8" square rod stock or cut off the splined section of the existing spindle. I can use a 3/8" to 3/4" coupling to connect the spline to the ER collet. Will this pose any issues as far as connection strength? The 4 tooth spline has the corners rounded over for a better glide into the splined pulley sleeve, but it may pose slop or compromise the holding power. Any ideas? I am open to using to using another mechaism or different size.


Finally, how do I resolve the issue with preload. Are there any solutions available for allowing me to preload the bearings? Given the combined 6mm missing from the bearing widths and roughly 1mm missing from the diameter of the shaft. There should be room for additional components on the shaft. Any ideas?


Thanks.

[Fastest1]

I don't own a milling machine, but I would like one. I am also a complete Noob learning from YouTube making little money sitting in a cube.

I have two drill presses, a Skil 10" and a cheap Harbor Freight 8". I've taken apart the cheap one to examine it as it is of no use to me anymore. I've decided to turn it into a lightweight milling machine and at some point in the future turn it into a CNC or chuck it for a real one (NPI). I already have a 3/4hp DC motor I salvaged from an old treadmill and I also purchased a 120v PWM motor speed controller.



My idea is to replace the existing spindle inside the quill with a beefy ER20 tool holder and swap out the bearings as well.



I bought an 3/4" diameter ER tool holder from a US seller on eBay at a price I couldn't resist:



DZ Brand 3 4" ER20 150 Collet Extension | eBay





The existing spindle is 12mm and the quill housing has an inside diameter of 32mm. The quill has two 6201 bearing (12mmx32mmx10mm). I couldn't find a bearing matching the same OD with a 3/4" ID. The closet fit I could find was a 20mm x 32mm x 7mm from AST:


71804C Angular Contact Ball Bearings | AST Bearings


I have a few questions.


First, is there a solution available for shimming the shaft diameter from 3/4 (19.05mm) to 20mm? I haven't seen any specific parts for this. If there are no solutions, I can always exchange the tool holder for a 20mm one, which is even beefier or just buy another one of the correct size. As for the missing 3mm from the width of the bearing, I am considering using thrust washers, thrust bearings and or shaft collars to make up the 3mm difference. Will this work? Is there a bearing bore adapter?


Second, the existing spindle has a 4 tooth 3/8" splined section to allow for transfering torque to the spindle while allowing the quill to retract and extend. I will need to somehow reproduce this mechanism. My current thought is to use a 3/8" square rod stock or cut off the splined section of the existing spindle. I can use a 3/8" to 3/4" coupling to connect the spline to the ER collet. Will this pose any issues as far as connection strength? The 4 tooth spline has the corners rounded over for a better glide into the splined pulley sleeve, but it may pose slop or compromise the holding power. Any ideas? I am open to using to using another mechaism or different size.


Finally, how do I resolve the issue with preload. Are there any solutions available for allowing me to preload the bearings? Given the combined 6mm missing from the bearing widths and roughly 1mm missing from the diameter of the shaft. There should be room for additional components on the shaft. Any ideas?


Thanks.

Ok, first of all the safety guys are going to jump all over this. On the other hand I say go for it, be careful, make sure you are aware of where you are when you power it up.

There ways of using bushings on a shaft to increase the OD. IMO purchasing the correct shaft up front will save in many ways. Bearings can be found in a myriad of dimensions too. Maybe try a few more sources.

Same with the bearing height. There are shims available, or just order the best bearing to eliminate other operations or parts. Make it is solid as you can.

Stay safe. post your progress. Pics too.

[109jb]

I don't see any real reason you plan won't work. Here are a few comments.

I would say the easiest thing to do is to get the ER collet holder with the 12mm shank. I don't like the idea of trying to shim the 3/4" shank to fit the bearings. If not done perfectly you will have horrendous runout.

As for the splined end, I would not use a external coupling. Since this setup would not need the capability of driving in reverse, I would probably drill and tap the end of the ER holder, and the end of the cut off splined shaft and use a threaded stud to join the 2 pieces with permanent locktite. You will have to turn the mating ends of each piece so that the spline runs as true as possible. Do you have a buddy with a lathe? You will also have to have a thread cut on the outside of the ER holder so that you can adjust bearing preload. See the crude drawing for what I am talking about.

[RichardDeptris]

Wow! I didn't expect to get this level of help and attention. I will definitely post back here with progress with pics!

I've been mulling it over and I realize that using a 12mm toolholder might be a better fit than using a 3/4 one. II would only have to source a few parts and I can cut threads for the spindle preload nut. I have a tap and die set up to 1/2".Can I use a regular right thread? Wouldn't the hardened metal pose issues when using a die?

The only problem is that the 12mm toolholder has a wimpy through hole diameter, which means I get a lot of stick out. I might have to just suck it up and deal. I could also go with a 20mm, but finding a die to thread the end would be difficult.

[Fastest1]

Any machine shop should be able to help with the threads. Where on the planet are you. There might be a zone member right around the corner.

[109jb]

The external threads may be tough to do because the ER shank is going to be pretty hard. I'm not sure if they are case hardened, or if they are through hardened. If through hardened, then the internal thread will be tough too. You may have to anneal the end for machining. You could cut the spline just below the threads ans cut the ER holder right at the top of the top bearing and use the original external threads for the bearing preload adjustment.

[mactec54]

RichardDeptris

Have a look through this thread, you may find some more ways to use your ER chuck

http://www.cnczone.com/forums/cnc-wo...dle-build.html

[RichardDeptris]

I currently reside in the Atlanta area. I would love to know of any resources there.