View Full Version : What size steppers for Grizzly mini mill?

Mini Miller
12-01-2004, 01:31 PM
Hey folks, I have heard different stories about what sized motors are sufficient for the mini mill. I am building the parts for the ballscrew conversion now and i'd like to buy some steppers soon so I can get to building the power supply.

What size motors are needed for the mini mill? I see a lot of guys using 300+ Oz motors and I see others using 200 Oz motors. I do most of my work in brass and aluminum but I need to be able to cut steel from time to time. Any help is appreciated.


12-01-2004, 02:43 PM
Mini Miller,
Sounds like your making good choices all ready. Ball Screws and not Acme - Good! As for motors, I would recommend going with 300+! I have build many conversions and mills and the stronger the better. I am doing some right now, and have 400+oz/in on the x-y and 300oz/in on the Z. Another suggestion, pull the gibbs and replace them, it will help with the amount of work the motors have to do!

P.S. AutomationDirect has new 400+ oz/in motors with cables for 99.00 bucks!!!!

12-01-2004, 05:57 PM

Automationdirect was a good lead. Thanks. Haven't seen them before now. Obviously didn't look hard enough. Anyways I'm in the market for some 400oz steppers and the prices are pretty competitive and the extension cables rather nice.

I took a look and noticed something interesting. If you compare the torque curves of the nema23 276oz-in at $39 and the nema34 434oz-n at $99 the 276oz is actually significantly more powerfull over 300rpm... depends on your leadscrews and how fast you expect to run them I guess..

12-01-2004, 06:16 PM
Yepper, I have been buying from them for years and a good company. Located in Atlanta, I live in Spring Hill and get my stuff in a day! I like the 23's myself, they are some powerful motors for the money. For mini mill conversions, I have been using the 434's for the x-y and the 276's on the z and working very well for me. I see your in Tampa, what area?

Check out there sensors, switches and most every other line they carry, good pricing and ships the same day, cant beat that!

Good luck man!

12-01-2004, 06:34 PM

I'm in St Pete's, though I'm often away working or back 'home' in the UK which cramps the cnc habit....

I've ordered the catalog and suspect I'll be buying some AD stuff. Building a 36"x36"x6" for a guy in Sarasota to do boat stuff with...



12-01-2004, 06:47 PM
Hey there! I live up in Spring Hill, but work in St. Pete. I work for a very large international semi conductor company and build automation and machines on the side. Its a small world, one of the engineers I work with builds 3-axis stuff for a boat builder in Pinellas Park. He is about to get the 3rd one done for him. I just build a 17"x20"x5 in my garage this weekend. All out of stuff I had laying around (my bud at work's idea). I have all kinds of motors, drivers, screws etc laying around. I figure I can build a few more just as fun aluminum/plastic machines. Good pratice tools for my friends that are learning this stuff.

Anyway, good luck. I think you will be very surprised with AutomationDirect, I have been dealing with them for years. Did you check out the ac drive/motor combos (great for spindle motors). Maybe we can meet and have a beer someday!


12-01-2004, 08:37 PM
Definately 300oz/in or more, I have some for sale in the classifieds:) take a look!


01-11-2005, 11:02 PM
Can anyone comment on these steppers?


01-11-2005, 11:16 PM
They are huge for the mini mill. I would say that 300oz-in motors have to be the best suited for the mini mill in my opinion. larger and smaller can be used, but both have their downsides.


02-12-2005, 07:46 PM
I'm just starting out here in UK. I have an Eagle25 bench mill and want to convert to CNC on 3 axis. Sounds like Big Daddy says the Nema23's should be fine ? anyone got 3 for sale and willing to post to UK?
How about the Gecko drives ? are they up to it ?



04-29-2005, 12:22 AM
Yes it is a small world. I have been reading here looking for info on a purchase I will be making Saturday with luck for a combo machine that I would like to convert. I have a nice shop area but it still getting set-up. I have no real tooling or well anything at this point and would like a local person to help point out some suppliers. A local machine shop has taken 3 weeks to do a solid shaft with 3 steps 3 key slots and threaded ends. Time for my own equipment.

John Labutsk
05-07-2005, 12:35 PM
I use 276 inch ounce steppers from Automationdirect.com. They work fine with a xylotex board 2.2 amps and 24volts. You can get full drive with the Arcsin board from Buildyouridea.com. This board provides upto 3 amps drive which is more than the 2.8 amps drive for the steppers. It also runs at up to 48 volts so rapids are faster than sensible to use on the mini-mills. I use 2.1 to 1 cog pulleys, 5/8ths ballscrews. I don't use the gas strut or counterweights and I have 40 ipm easily on the z axis. No counter weight or gas strut means I have the power to plunge the cutter down into the workpiece and not worry about lost steps. I have 3 board brands, the Xylotex, arcsin, and Hobbycnc. I have tried all three boards on my mini-mill. In the case of Hobbycnc I had to swap the Automationdirect motors for the hobbycnc unipolar steppers. All worked fine. The Arcsin has the most torque and speed but is also more expensive. The arcsin gets you close to the gecko range and has optoisolation so you don't need a breakout board as you do with gecko's. Hobbycnc has an economical kit, and xylotex is assembled and tested. I've been happy with all three boards that I mentioned. All with cog pulley drives these boards have the drive abilities to exceed the rigidity of the mini-mills when cutting.


07-16-2005, 11:05 PM
I'm drunk and feeling pedantic, so here goes (please don't be offended) :

"300 oz in" is a measure of torque (and holding torque at that, so only handy as a guide and not the torque that matters for most applications). Torque is quantified by multiplying the force measured by the distance at which it is measured.

So my 300 oz in server would have a holding force of 300 oz at a distance of 1 in (300 * 1 = 300). At 2 inches from the centre, it will have a force of 150 oz (150 * 2 = 300 still), at 3 inches it will have a holding force of 100 oz, etc.

In other words, this is "300 oz in", perhaps "300 oz-in", or maybe even "300 ozin". It is not "oz/in" or "oz per in". If you Americans can't use real units (N and m), then at least use your imperial units correctly :) (this is meant as a joke)

John Labutsk
07-17-2005, 09:46 AM
I used the 276 inch ounce automation direct steppers, 2.1 to 1 cog pulley drive and 5/8ths ball screws. My tests indicate that this setup exceeds the rigidity capabilities of the mini-mill table with the gibs super tight and no lost steps. My tests are real world. Heavy cuts and heavy feed rates. Simply put, it works for me.

07-18-2005, 12:45 AM
I will concur with John L, and my steppers are direct drive for X and Y. They have MORE than enough power for what I do. Mainly AL, 12ipm at 0.05" DOC. I have cut through 0.05" of AL and 0.50" of clamps when they got in the way. I could probably take a bit more DOC, but for what I am making it works reliably.

HF Mini Mill
Xylotex 4 axis
276oz in steppers
ballscrews X Y Z