Harbor Freight Mini-Mill CNC Conversion

Self Made Knives

Well-Known Member
Ok guys, here's part one. A short intro and table disassembly. Skip right to the video or read my boring explanation of why I'm doing this below.

Here's a little background on my interest in CNC. I went to college right out of high school to become a mechanical engineer, but after a couple years of school, I was extremely bored and restless. Got the brilliant idea to quit college and start a roofing business with a friend, which didn't end so well.

Joined the Marine Corps and worked avionics on F18 Hornets. After the military, started college for the second time, in the Electronics Tech program. I became aware of CNC milling in the early 90's while our college class took a tour of a local business that was converting old equipment into modern looking CNC machines bound for factory duty.

I was getting pretty good at computer programming and electronics so I built a couple stepper motor controllers and wrote some code to do basic x and y movements. I even made a cnc Etch-a-Sketch that worked pretty good! Made a crude cnc foam cutting machine for making foam cored R/C airplane parts too.

Then, along came marriage, kids, better job, more school, etc. All those cnc thoughts faded and technology advanced well past what I knew. A few years ago, I bought a Carvewright cnc wood router and it sort of renewed my interest in cnc for a while, but it is pretty limited as to what you can do with it. Everything is proprietary and every little option costs more and more money.

But lately, with this new hobby of knife making, all those cnc thoughts have been creeping back in. Someday, I like to get into some 3d machined pocket knife scales or even some 3d machined fixed blade scales. Pistol grips? I like working on old cars and hot rods, so I've got some ideas for that arena too.

Now, I just hope I can figure all this stuff out again!

[video=youtube_share;Lu8VAfHwjGI]https://youtu.be/Lu8VAfHwjGI[/video]
 

Self Made Knives

Well-Known Member
Here's part 2 of the project. I'm making stop blocks or ball nut holders, if that doesn't make sense you're not alone. I've got a few comments from guys that say they're not sure what I'm talking about. It'll all make sense eventually.
[video=youtube;00xXvAkdbic]https://www.youtube.com/watch?v=00xXvAkdbic[/video]
 

Drew Riley

Well-Known Member
A simple formula for finding the minor diameter of any tap: Bolt O.D. minus (.975 divided by PITCH) = I.D. of nut. So .9375 - (.975/16) = .8765, which for all practical purpose is what you got with a 7/8 drill. ;)

Also, the reason HF (or rather the Chinese company that made the mill) rounded that original ball nut was probably for efficiency. Rather than make 2 completely different parts, they just set up a machine to make one and probably turn them out by the hundreds. I imaging the x nut is then trimmed down to fit during a later step. I may be wrong.

At any rate, looks like you're making good progress. Looking forward to video 3!
 

Self Made Knives

Well-Known Member
Now that you mention it, I remember someone talking about a drill size formula before. I got lucky that it worked out since I had that drill bit already. If I were a "real" machinist, I could've cut internal threads on the lathe, but I'm not that good.
 

Self Made Knives

Well-Known Member
Part 3. Machining ball screws. This was a little tough for me/my lathe. I don't think my little lathe is really stiff enough for this job, but, nonetheless, I got the Y screw finished. The X screw will just be a repeat, so I don't show it in the video. I'm sure you machinist out there will find a bunch of problems with my technique, but what do you expect from a YouTube machinist? :biggrin:
[video=youtube_share;SCbNhOAMFEQ]https://youtu.be/SCbNhOAMFEQ[/video]
 

Self Made Knives

Well-Known Member
Part 4. Still working on the Y axis, this time its a bearing block for the ball screw. And, my first "screw" up, but not too bad. I hope you guys don't mind these shorter videos because it sure is a lot easier for me to keep up with and edit in smaller chunks. If I wait until I get several hours of video recorded and then try to condense it into 30 min. or less, its a ton of work and takes forever to upload. I think keeping them less than 10 minutes each and focusing on one part at a time is best for my sanity.

[video=youtube_share;gad5wrFwWAE]https://youtu.be/gad5wrFwWAE[/video]
 

Drew Riley

Well-Known Member
I've had the same experience with the imported dies... They're only mediocre at best at chasing threads, and I wouldn't even bother trying to cut a new thread with them. They MIGHT work once, and that's about it. The taps aren't much better. I bought one of the $40-$50 sets at the hardware once, and there's not a single piece in it that I'd give a nickel for. Anyone is much better off just buying a good USA brand as they're needed, or if funds are there, to just by the whole sets.
 

Self Made Knives

Well-Known Member
Oh, the irony! I catch myself griping about import tools and then it occurs to me, I'm using them on an import tool! I was stationed in Japan for a while in the military and I noticed that the cars they were driving looked nothing like the Japanese cars sold in the US. I asked on of the locals once where were all the Honda's and Toyota's? The guy said, "We make those to sell to Americans, we don't use them here". I wonder if the same is true for Chinese tools? Do you think they use this crap they peddle over here or is it "just to sell to Americans"?
 

Drew Riley

Well-Known Member
Haha... that's a good question. I'm sure if I looked, I have more import tools than USA made, especially considering the increasing difficulty to find anything stamped with MADE IN USA on it anymore.
Granted, not all imported tools are bad, and many of them are actually quite decent. That said, I've had nothing but trouble with Chinese taps and dies, including some that cost a significant chunk of change. Either they're just not hardened enough, or the size is ever so slightly off, or you just can even get the dang thing started...
 

Motor City Mike

Well-Known Member
Very enjoyable videos!

They're well shot and edited.

And strange enough, I'm really digging the music.

Keep up the good work. I'll be keeping an eye out for new episodes.
 

Self Made Knives

Well-Known Member
Thanks, I've almost got another installment ready, my Mom's husband passed away last week and I haven't been in the shop. Been crazy around my house.
 

Self Made Knives

Well-Known Member
Here's part 5 of this project. Making a motor mount plate for the Y axis and doing a little milling machine maintenance. Might be a while before the next installment, I won't be able to work in the shop for the next couple weeks, my son is having surgery on both feet. Double casts for 6 weeks, yuck.
[video=youtube_share;Z8FhT4nGk20]https://youtu.be/Z8FhT4nGk20[/video]
 
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