© 2007 Daniel E. Kemp
Frequently Asked Questions
1. Q? - How does the Power Drawbar work?
A - Bellevile spring washers force the drawbar up away from the spindle which pulls up on the collet drawing it tight. The air cylinder pushes the cam against the top of the drawbar forcing the collet open for a tool change. Tormach has an animation that shows how the collet works.
I stacked 6 springs from MscDirect in series like this ()()() which gives the total force of 1 spring and the total deflection of 6 springs for the drawbar. This gives 654 lbs (2910 Newtons) at deflection
holding the toolholder in the collet. This is more than adequate force for holding tools without slippage
for any milling the X2 or X3 could handle. The power drawbar can apply 1100 lbs of force at 100 psi.
so it is more than capable of taking these bellevilles to flat if needed, 859 lbs (3821 Newtons)
2. Q? - What CAD/CAM programs do you use.
A - I mostly use Autodesk Autocad that i've had for years for making DXF's.
The newest version costs about $4000. Solid Edge 2D is nearly the same but totally free.
DeskCNC is my main CAM program, pretty simple but does everything I need.
It's only $250 but try the trial version first to check it out.
For text engraving I use Deskengrave which is also free.
My next purchase will be Cut2D from Vectric. It has a easy to use interface for g-code toolpath creation and is cheaper than DeskCNC. They also have Cut3D and VCarve Pro.
These programs can automatically post the g-code to Mach 3.
3. Q? - If I buy the complete kit and ballscrews, what other parts do I need to buy to finish the CNC conversion?
A - You'll need the Bearings from MSC.
03548591 3/8 X 11/16 X 9/32 SET THRUST BALL BEARING (2 sets)
03380961 1.250X1.938X0.078 THRUST CAGE-NEEDLE ASSEMB
03381142 1.250X1.937X0.032 THRUST WASHER-NEEDLE-FLAT
03380045 1.250X2.344X0.625 THRUST-BALL-BANDED MEDIUM
http://www1.mscdirect.com/CGI/NNSRIT?PMAKA=03380045 or # S9912Y-TB125234 SDP/SI
-And the small pulley and timing belt from SDP/SI
A 6A 3-16DF03708 .200 (XL) Pitch, 16 Teeth, Aluminum Alloy Timing Pulley
A 6B 3-060037 .200" (XL) Pitch, 60 Teeth, 3/8" Wide, Urethane Belt (get a spare)
-And you'll need (3) ballnuts from Roton.com part # 19193.
For anything else check out the complete DIY list.
4. Q? - Why are the ballscrew end diameters different?
A - The X axis ballscrew diameter is .390 because it uses the stock X axis metric bearings.
The stock Y axis never used bearings so I added a pair .375 bearings to handle the rpm of cnc.
5. Q? - Can I call you on the phone to discuss something?
A - Sorry, no. I only use my cellphone which costs me per minute. I work odd hours so I'm usually
working or asleep when most people are up and about. I can give much better answers with links
in an email anyway.
6. Q? - Can you machine a complete kit for me or any other custom parts not listed in your store?
A - Complete kits are out, I just don't have the time. Custom parts are possible every once in a while if i'm not busy making parts for the store. I still have projects in the works so free time to work on them is precious.
7. Q? - Do you like your KL-4030 drivers from Keling?
A - I use 6 KL-4030's for my drivers, very happy with them.
It's easy to change the microstepping by just flipping some switches.
I like running on just half step for most of the axis and use 8 microsteps for the 4th axis.
They take a max 40 Volts, a lot less than some of the expensive drives but I get more than enough speed out of them. 120 IPM on the X with 5 tpi ballscrews.
Gecco has the new g540 that goes to 50V but they are stuck with 10 microsteps.
Keling offer several packages including the new g540, it just depends on how much you want to spend for a small gain in speed.
8. Q? - Considering all the time and money you've spent on this, have you considered just buying one of those mid-level cnc mills.
A - I'd love to have a used Haas Minimill but the problem is there's no way I could get one into my basement. I had to pass up a couple used bridgeports and lathes from work for the same reason.
Might have been a good thing because had I been able to get a Bridgeport, I would never have gotten into this whole benchtop CNC mill hobby.
9. Q? - Why did you buy an X2 and not an X3 or Taig?
A - After having to pass up a used bridgeport from work because it would't fit in my basement
I decided to buy the cheapest, heaviest duty small mill I could that had R8 tooling capabilities.
The X3 was new then and 3 times the cost of the X2 and a Taig is just too dainty for what I wanted.
I was looking for a manual mill and having to drill holes with a taig with it's hand crank would be a nightmare, the X2 has a quill handle to easily move the Z axis up and down. The X2 is cast iron and can handle much bigger tooling.
10. Q? - How does keygrabber work?
A - Keygrabber detects just about any input device that you have connected to your computer
keyboard, joystick, USB game controller etc. and allows you to assign Mach 3 hotkeys to any of the buttons or controls. It only works with Mach and is included in the Mach install folder.
I made a 3 page tutorial for assigning the keys with it on this page towards the bottom.
Also have a video to show how to get all the hotkeys that Mach 3 is using for your screenset.
11. Q? - Does the X2 Freak head extension hurt the rigidity?
A - I performed several feedrate tests to make sure the head extension didn't hurt the rigidity.
It passed with flying colors. It cut with a .500 HSS Endmill @ 2000 rpm, .100 D.O.C. @ 50 IPM and .125 D.O.C. @ 30 IPM. These were done before I had flood coolant which would make it even better.
Check out these videos on Videos Page 5, even more tests on Videos Page 4.
12. Q? - Why did you use 2 motors for the Lathe/4th Axis and not a Servo motor?
A - I started out just making a lathe attachment and used the parts I had from an old 7x10 minilathe. It cost me nearly nothing to make. Then I thought it could work as a 4th axis too.
To work for positioning a part for milling, it needed a motor that had a lot of holding power to keep the mill from moving the part out of position during machining. A stepper motor gives the best holding torque and I already had one so it was simple to make a bracket to mount it. Again it cost me next to nothing. An encoder on the DC motor could give positioning feedback but it wouldn't have the holding torque. A Servo motor could work for both operations but they aren't cheap. If you had to buy everything to make your own combo it would make more sense to go with a Servo of about 850 oz/in peak torque at least. The cost of my version and a servo version would be close to the same. A servo doesn't have the holding torque of a stepper but with about a 4:1 pulley ratio, you should get enough holding torque and still have enough rpm for turning.
13. Q? - Why did you use flood coolant and not mist?
A - These small mills are easy to enclose to keep the chips from getting all over the shop as compared to a kneemill or large benchtop mill. The main reason I chose flood is that it's whisper quiet. Mist requires a compressor running all the time and as anyone who has watched my videos can attest, the compressor is noisy as hell. Who wants to listen to that all day? Not this guy :-)
I use Syn-Kool for the coolant and haven't had any bit of rust in a year now.
14. Q? - Do you accept payments other than Paypal?
A - When you add an item to the Cart and then Proceed to Checkout, you are brought to the Paypal Checkout. You have the option of paying with a credit card or even a bank account if you don't have a Paypal account. There is no need to create an account with Paypal if you don't want. You can also send me an email requesting payment with a Money Order.
15. Q? - Why did you use that design for the Z axis?
A - I saw that design on a mill converted using the Sterling Steele plans and thought it had more pros than cons.
Pros - The screw is up and away from the flying chips.
- The ballscrew needs very little machining, just drilled and tapped.
- It lifts the head as close to the center of gravity as possible.
- Easy to mount, just drill 6 holes and tap 2 of them.
- Gib screw access is not a problem unlike with some other designs.
- The amount of stock need to construct is minimal.
Cons - The screw sticks up in the air when the head is up.
16. Q? - Is the Power Drawbar strong enough to hold the tools?
A - Yes it is. At least for what it's designed to work on, X2 or X3 sized mills.
The Belleville springs exert around 650 lbs of pull on the drawbar. This gives the collet more than enough clamping pressure on the toolholders to retain them for any milling the machines can handle.
These mills don't have the mass or rigidity of a 1000lb Industrial Hobby mill or a 2500lb kneemill so of course they can't get near the same cutting rates. Those mills will need much more pull to retain the Tormach type toolholders without slippage. A BT30 toolholder is a better option for them. It has dogs to keep the toolholder from slipping. The Tormach style is suited best for the smaller light duty mills that need much less clamping force. I've made a video that shows my Power Drawbar is more than capable of retaining the toolholder, holds fast with a .375 endmill with a .375 DOC in Aluminum.
The test was done with a 4 flute HSS endmill @ 2500rpm. This is a finishing endmill, not the proper roughing endmill I should use for a DOC this deep but I was all out of roughers. I'll rerun the test with a rougher and it should get the .001-.002 chipload I prefer. With a finisher I normally don't go more than .125 DOC @ .0015 chipload.
17. Q? - Does the Power Drawbar hurt the spindle bearings?
A - That was a concern early on but not now. The force put on the bearings is gentler than the shock force that can be applied by whapping the drawbar to release the collet manually. It's been nearly 2 years (10/07) since the drawbar was installed and it has done hundreds of tool changes since then. The stock bearings are still silky smooth and that's even after also being subjected to
2 1/2 times the original max (2500) rpm. The belt drive conversion runs at up to 6100 rpm.
18. Q? - Would you have bought a bigger mill if you could go back in time?
A - Maybe. Do I regret getting the X2? No way. I've made thousands of dollars because of what I've done to and with the X2. Made my money back 10 fold. If I'd have bought an X3 instead,
I probably would have "freaked" it as well but they aren't as common as the X2 so who knows If I would have made as much. Had I gone for a ZAY or RF-45 sized mill, I doubt I would have done much of anything to it other than CNC. Definitely wouldn't have been a money maker. I definitely would have spent more money. Don't have the room in the basement for anything bigger than those, If I had, I'd have bid on a used Bridgeport from work ages ago. Who knows If I would have even thought about CNC in that case. This site would not exist either. No regrets.
19. Q? - What endmill did you use to make the timing pulleys ?
A - I used a .078 (5/64ths) 2 flute HSS endmill. I made the groove depths .060 inch deep usually .010 per pass. I then made a single pass with a 3/16 90 degree countersink to make about a
.010-.015 chamfer on the groove edges. This step is necessary as the timing belts have a small radius and need the clearance for the belt to fit properly. Check out Bob Adams Timing Pulley Maker Program. He took the info from my earlier g-codes and videos and made a great piece of software.
20. Q? - What lathe tools did you use to turn the ballscrews ?
A - I used a CNMG toolholder and inserts. The tool holder has a 1/2 shank that should fit most lathes. MscDirect has a good quality toolholder and the CNMG 80 degree inserts for it.
Wholesale tool has a cheaper CCMT tool holder that uses single sided 80 degree inserts.
If you are interested in hard turning, MscDirect has CCMT ceramic inserts, don't use them on the ballscrews, the interupted cutting will shatter them.