Sherline Mill CNC Conversion - Model Workshop

In August 2004 I picked up the new IMService System 3 DeskCNC Sherline Servo CNC conversion package. Fred at IMService was a great help in putting together what I need and getting me started despite my numerous newbie questions.

This page is pretty long. I decided to include information here on the Sherline CNC upgrade kit, the IMService System-3 Servo CNC system, and the CAD/CAM Software I use for designing parts to be machined. To view larger versions of any of the images, simply click on them. The larger image (typically 1024x768 or so) will open in a new window.

If you find the information on this page useful or interesting, please take a moment to sign my guestbook. Thanks!

A quick CAD/CAM/CNC Primer

My intended use for my setup is to produce parts for my HO scale (1:87.1) model railroad locomotives and rolling stock.

Now, of course you can create the NC code by hand if you wish. If you do that, you remove the need for CAM and CAD software. However, that is not the route to take for anything but fairly straight-forward parts. Sure, some folks always work in this and never use CAD/CAM, but some programmers also like to write applications in assembler or MSIL as well :-)

1. Installing the Sherline CNC Upgrade Kit

1.1 X and Y Axes

Figure 1.1.1 - X Axis Motor Mount The Sherline X Axis Nema 23 motor mount installed. Pete Brown, August 13, 2004

While waiting for the IMService servo kit to arrive, I installed the Sherline CNC Upgrade kit (pn 6700). This kit consists of Nema 23 motor mounts and couplings for the X and Y axes, as well as a motor mount, coupling and new screw for the Z axis. Since my Sherline was a newer model, purchased in 2001, the X and Y axes were already drilled and tapped to accept the motor mounts. Installing them presented no problems.

Figure 1.1.1 shows the motor mount in place on the X axis. If you're going to convert your Sherline to CNC, definitely go with these mounts and flexible couplers. I was told that they are worth every penny, and so far they have lived up to that claim. Since these are the single point of interface between the motors and your leadscrews, don't skimp here.

1.2 Z Axis

Drilling

Figure 1.2.1 - The Z axis column drilled Great results from a regular hand drill. Pete Brown, August 13, 2004

The Z axis was neither drilled nor tapped; I'd have to do that myself. This was a bit of a nervous moment for me as I had never previously drilled or tapped steel. Prior to this, plastic was all I really worked in. Nevertheless, it went off without a hitch. The templates Sherline provided, and the adivce I received from the great folks on the Sherline CNC group helped me get the work done correctly and pretty quickly.

Note: If you purchase the CNC-ready Sherline mill right from the start, you will not need to do the drilling and tapping like I did.

The first thing I did was remove the headstock from the Z axis column. I did not want to get any chips in the ways, spindle or motor. Once that was done, I covered the mill table and base with shop towels, and did the same with the Z axis column (figure 1.2.1). This protected the whole unit from chips (and there were a lot of fine chips) as well as the drill and tap fluid.

Figure 1.2.2 - Tapping Fluid and Tools Tapping fluid, the taps, and the small brush I used to get the fluid on the drill bit. Pete Brown, August 13, 2004

Whenever they exist as a good alternative, I use non-hazardous and environmentally-friendly chemicals. This is not only better for my eyes, skin and lungs, but also for the area we live in. I found the biodegradable Tapmatic Natural drilling/cutting/tapping fluid (figure 1.2.2) has worked well for cutting in the past, and for drilling and tapping the column.

Drilling the holes was pretty easy. I attached the steel sherline template with a C clamp (using a block of wood to protect the ways from the clamp) and lined it up by eye. To drill I put some tapping/drilling fluid in the holes in the template and installed a #29 TiN-coated metal-cutting drill bit in my Dewalt corded hand drill. The template made using a drill press unnecessary. In fact, the template was likely far more accurate than my drill press anyway, so using it would have probably bound the bit up in the template. (If you do use a drill press, I'd recommend using the template only to position and mark the holes, then remove it to do the actual drilling.)

I backed the drill out a couple times to clear the chips from the holes, and to brush more fluid on the bit. Once the holes were drilled, I wiped up the fluid and chips, and blew compressed air into the holes to clear out any remaining chips (do this with a paper towel over the holes or you'll make a heck of a mess - don't ask me how I know!)

Tapping

Figure 1.2.3 - Tapping the Column Back out often to break and clear the chips. The last thing I wanted to do was break a tap in this column.Pete Brown, August 13, 2004

This was my first time tapping steel, so I sought the adivce of the folks on the Sherline CNC forum. Based on the advice of the nice folks on the Sherline CNC forum, I took my time tapping the mill column, and made sure to only go a half a turn or so at a time before I backed up to break off and clear the chips. Every couple turns, I would back out completely to make sure nothing was stuck. I would also re-lube the tap at that time.

The tap I used to start the threads was a brand new sharp HSS american-made Plug Tap from Enco USA. I picked it up in a kit that had the three commonly-used taps. The plug tap has a longer taper before the full threads start, so it is exactly what you need to start off squarely. However, it is not any good for finishing the threads in these blind holes. For that, I used a Bottoming Tap from the same kit. Again, both were brand-new, very sharp and very well made. I've seen other import taps that simply look terrible and not nearly as sharp. When you're working on something as important and as costly to replace as your Sherline mill column, don't skimp just for the sake of $2.00.

The blue tape in Figure 1.2.3 is there to help me gauge how far to go until I reach the required tapping depth. The tape moved due to the tapping fluid, however, so I'd suggest something better like a rubber band, or a real metal-collared depth stop. Also, please note that the tapping handle I used really was too large for this job, and likely made it more difficult to control than necessary. A smaller tapping handle would have been a much better choice.

Figure 1.2.4 - Column Tapped The perfectly-tapped holes. Everything fit together smoothly. Pete Brown, August 13, 2004

The end result (figure 1.2.4) was even better than I had hoped. There is something very satisfying about drilling and tapping a piece of steel. It is hard to express quite what it is, but seeing your nicely-tapped holes, and being able to put the hex-head screw into them smoothly is a very primal experience. My friend Ron said that people have been working metal for thousands of years, so there is almost something in the blood that responds to it. Of course, people have been working wood for even longer. As much as I like working with wood, wax, and plastic, it doesn't elicit quite the same visceral response that this did. I suspect it has to do with the relative toughness of steel and cast iron vs. the relative ease of working with wood.

Installing the Z-Axis Motor Mount and Leadscrew

Figure 1.2.5 - Z-axis motor mount installed The new Z-axis motor mount and anti-backlash nut. Pete Brown, August 13, 2004

Once I had cleaned-out the newly-tapped holes, installing the Z-axis motor mount and new lead screw was pretty easy. At the same time, I installed Sherline's new Anti-Backlash adjuster pn 4017Z (barely visible behind the column). This helps control just how tight you keep the Z axis to reduce backlash.

The Z axis motor mount and leadscrew come pre-assembled, so there is not much to do other than thread the nut up the screw, mount the motor mount with the two screws provided, and remount the headstock. I also used this time to adjust the headstock gib so there was no visible play.

I ordered both the backlash adjustment nut and the CNC Upgrade kit from The Sherline Shop. I've picked up accessories from them several times before, and have always found them to have the easiest catalog and checkout, the lowest price, and the quickest shipping. When it comes time for me to pick up the CNC-ready rotary table (I didn't realize at the time that rotary table could not be reliably converted to CNC using the Sherline-standard motor mounts), I will certainly pick it up from them.

With these steps done, all I needed was the IMService CNC system. That would arrive quickly - just a few days later.

2. CNC Controller Computer

Figure 2.1 - CNC Control PC The new Z-axis motor mount and anti-backlash nut. Pete Brown, August 15, 2004

While I was waiting for the controller and motors to arrive, I set up the CNC controller computer. Figure 2.1 shows the computer actually standing on a shelf on the pegboard (seems to be holding up ok). Behind the computer is the UPS. I try to make sure any electronic equipment in the house (TV, DVD, game consoles, various computers, DSL router, water softener etc.) are all on well-conditioned power with battery back-ups. Regular surge supressors don't even out the power going to a piece of electronic equipment - they only cut off the tops of any spikes. APC battery backups do a better job of handling lower-power conditions and therefore help keep your equipment running well and running long. I have around 8 or 9 of these around the house. When the power goes out the house is a symphony of alarm beeps.

I seem to have no shortage of old PCs around this house. For the CNC computer, I appropriated the fastest of the in-storage PCs - my wife's old Gateway Celeron 400. It had only 128MB of RAM, and a very old and worn hard drive. I filled the last available RAM slot with a 64MB stick snagged from another old PC, and picked up and installed a new Western Digital 40gig hard drive. The 40gig drive was dirt cheap over at Circuit city, and was a good investment. Not only was the old drive well beyond its expected 3 year mean time between failures, but it was also slow as a snail.

To make better use of the space, I picked up a cheap keyboard drawer at Comp USA. It seems to be working out well in its new home.

3. CAD/CAM Design Computer and Software

Figure 3.1 - Rhino Demo Screenshot Rhino is simple for me to use, but extremely powerful. The screen looks very wide in this shot because of my HP 2335 wide aspect-ratio LCD screen Pete Brown, August 28, 2004

I wouldn't use the old 400mhz old PC for any real work, but as the controller PC, it works very well. All my actual design and modeling (and programming work I do) is done on a 3.0ghz Pentium 4 with 2gigs of RAM, two extremely fast 74mb Raptor 10k RPM SATA drives in a striped array (very very fast), and a HP 2335 23" wide LCD panel running 1920x1200. That panel is very nice, and is a recent addition.

Being a software developer for a living means I spend a lot of time in front of my computers. I typically try to keep them up to date with pretty modern technology. I do a significant upgrade about every 16 to 20 months. The old PCs typically end up as servers (this web site and my mail server are running on two of them), or as in the case above, as utility PCs for some project or another.

I use Rhino 3d as my design software. I tried out the demo for a while (Figure 3.1) before settling on it. In the screenshot you can see the extra width the 23" wide-aspect ratio screen provides. It really makes a difference with software like 3ds Max and Visual Studio .NET - both of which have tool pallets or file/class browsers on the sides. With Rhino, the extra space is good for general workspace, and to fit a couple extra toolbars on the side. The simple locomotive driving wheel you see in that screenshot is one I tried to create in various CAD and 3d programs.

Figure 3.2 - Rhino Render Version 1 of a replacement end for the Walthers' troop sleeper. I later made significant changes - something that is very easy to do with CAD software. Pete Brown, August 27, 2004

I tried a lot of different CAD programs before settling on Rhino. Some, such as the excellent Vector XT do many of the things Rhino does, plus do all the CAM work. Many others are good for basic 2d CAD work, but not for the complex surfaces I intend to machine. In the end, however, it came down to how easily I could use each program and how well the UI "gelled" with the way I like to work. I've been modeling in 3d for several years now using TrueSpace (the first one I used), Bryce, Lightwave and most recently, 3ds Max 6. Rhino worked more like those 3d programs than any other CAD program I used, and had the advantage of being a native NURBS modeling program. I was able to get into it right away and be productive literally within minutes. Since I own 3ds Max 6, I also evaluated NPower Power Solids before I settled on Rhino. I was hoping that Power Solids would basically turn 3ds Max into Rhino, but that was not the case. Again, it came down to workflow and ease of use for me.

When it comes to the software, try out the demos of several programs before you pick one up. It is often not just the feature set that will decide what you get, it will also be how well each program works the way you work. A superior feature set means nothing if you will never be able to figure it out. However, a very simple program with very limited features is something you'll quickly outgrow. Figure out how easy it is for your to learn the basics of the software, and base your judgement on that.

Figure 3.3 - Rhino Add-in Screenshot My first Rhino C# add-in Pete Brown, September 3, 2004

Oh, yes. The final thing that sold me on Rhino was the availability of the .NET SDK for Rhino. I code in .NET all the time, so the idea of being able to automate Rhino using the tools I already own and use daily was just too much for me to pass up. I've already created some addins for Rhino in C#. I'll post those to a different section of the site soon. The first add-in I completed (figure 3.3) was one that allows me to quickly create lots of rivets that have a specific diameter and spacing, and follow a drawn line. The excellent developers at McNeel (especially Steve Baer and Dale Fugier) were a great help in getting me started with the .NET SDK for Rhino. They both monitor the Rhino Plug-Ins newsgroup and respond to tons of queries, day and night. How they ever get their other work done is beyond me. :-)

For those of you who don't code for a living, you can also automate Rhino using VBScript. VBScript is a standard scripting technology that is very easy to pick up, and is very forgiving. There are lots of samples for VBScript on the www, and McNeel themselves also supply an excellent primer in VBScript development.

If you're a student, or you are getting this for your son/daughter who is a student, Rhino is very inexpensive. Unfortunately, I'm not a student and have no kids, so I paid full price for it. Even at full price, however, Rhino is thousands of dollars less than many other programs with similar features.

I'm still evaluating CAM software that does more than the basic XY paths supplied by DeskCNC. Given the crazy prices of these programs, and the horrible user interfaces of many, I might just write some of the CAM software myself as Rhino add-ins. TBD. In the mean time, I've picked up Peter Smid's "CNC Programming Handbook - second edition". This is a decent primer on CNC and g-code programming. It's geared towards non-programmers, so some of it can be tedious for me to read, but overall it is an excellent primer and reference.

3.1 Software I Evaluated

The table below lists only software that I evaluated. In some cases (Visual Mill, for one), the evaluation was just research and literature. In most cases, the evaluation consisted of using a demo version for a trial period. There is other popular software out there for CAD/CAM that I have not yet evaluated. At this time, my CAD needs are completedly filled, but I am continuing the search for Rhino-friendly CAM software.

While I do have a degree in Computer Science, specializing in Human Factors / User Interfaces, the UI comments below are subjective. What works for me may not work well for you. The opposite holds as well. Some user interfaces are truly horrible, though, so I made sure to note that below.

Keep in mind that my work is mainly 3d with surfaces with complex curves (think about the front of a F-unit). If you are spending your time working mainly in 2d, designing flywheels, pockets, plates etc., the software comments below will not apply. Most CAM software, including DeskCNC have very good DXF-based 2d toolpath generators. Not many (in the lower price spectrum) have good NURBS-based toolpath generators.

Bold indicates that I own a license of that software. This table is accurate as of 2004.

Title	3d Design	3d CAD	2d CAD	CAM	Notes	Link
3ds Max 6 with PowerSolids	yes	no	no	no	Not for CAD. Good UI for Max, not so for Power Solids. Lacks dimensioning and exact measurements. Great for rendering and animation.	Discreet, NPower
DesignCAD 3d Max 15	yes	yes	yes	no	Decent CAD program. UI OK.	IMSI
DeskCNC	no	no	no	basic	Purchased. XY/Parallel 3d toolpaths only, more options for 2d. so-so UI. Also serves as controller software for DeskCNC system. Online support through IMService	DeskCNC
DeskProto Lite	no	no	no	basic	Excellent UI. Basic CAM	DeskProto
DeskProto Full	no	no	no	advanced	Excellent UI. Advanced CAM	DeskProto
Dolphin 3d CAM (HobbyMaster)	no	no	no	advanced	so-so UI. Good 3d CAM. Buggy on my PC. Frozen at current version. Under $700. Yahoo Groups support group.	Dolphin
FreeMill	no	no	no	basic	Does less than DeskCNC, but is free.	MecSoft
madCAM	no	no	no	intermediate	under $500. Waterline, finishing etc. This is a Rhino Plug-in, and is pretty good for the money.	madCAM
MeshCAM	no	no	no	basic	In development. Promising UI, basic features for now, but includes waterline and parallel/XY toolpaths. Well under $200. Yahoo groups support group with active developer involvement.	MeshCAM
QuickCAD 8 (now Autosketch 9)	no	no	yes	no	Own. QuickCAD 8 has been discontinued. Upgraded to Autosketch 9. Good 2d. Good UI. I use Autosketch 9 for much of my 2d Work.	(Replaced with AutoSketch 9)
Rhino 3d	yes	yes	yes	no	Best UI for me. Instantly productive. Has C++ and .NET SDK. Excellent support through McNeel newsgroups with active developer involvement. Most bang for your buck when it comes to 3d modeling and CAD software, IMHO.	McNeel
StlWork	no	no	no	basic	XY/Parallel and Waterline toolpaths. Absolutely Horrible UI, but inexpensive	IMService
TurboCAD Pro 10.1	yes	yes	yes	$	CAM is extra. CAD is typical 3d CAD. Could not test CAM module using trial version of CAD.	IMSI
TurboCADCAM 2.5	?	?	?	?	Despite system requirements on site, the demo won't install without TurboCAD 10.x installed. Unable to evaluate	IMSI
Vector XT CAD/CAM	yes	yes	yes	advanced $	Very Powerful. 3d and 4th axis are extra but still under $1000 total combined. NURBS. On my CAM shortlist. Only program in this table that gives you 100% control over toolpaths. The CAD part does nothing for me as I prefer Rhino. Online support through IMService. If you need a one-stop CAD/CAM package, look seriously at this.	Centriforce,IMService
Visual Mill	no	no	no	advanced	Excellent, but way too expensive. Basic version not any good for my needs. Also available as Rhino plug-in. This is the standard most people refer to. The price (several thousand dollars) is beyond what most of us will pay for hobby software, however. Note: See update on RhinoCAM below.	MecSoft

3.4 Final CAM Software Purchase

In response to an introductory sale (for the first 50 customers), I picked up a copy of RhinoCAM Pro from Andrew Werby at computersculpture.com . I highly recommend both the product and Andrew. RhinoCAM Pro is Visual Mill integrated into the Rhino user interface. It's a very impressive product and a very slick integration. Andrew is also a great guy to deal with, and always has the best prices on the net.

4. Installing the IMService System 3 Servo CNC Conversion

4.1 Overview

I purchased the four axis System 3 DeskCNC Servo system from Fred at IMService. I also included the toolsetter/probe as part of the kit. Alltogether the kit came with:

4.2 Motors

Figure 4.2.1 - System 3 Servo Motors and Gearboxes Three of System 3 Servo Motors. The A-axis motor (not shown) does not have a gearbox. Pete Brown, August 15, 2004

The version of the System 3 I purchased included four great Servo motors, three of which have reduction belts (figure 4.2.1). These things are quiet, cool and powerful. There is a lot of debate about whether or not you should get servo motors or if stepper motors are good enough. While I suspect steppers would have been sufficient, I like the full-feedback (closed loop) provided by the servo motors. As an example of that, I turned the Z axis handwheel a tiny bit while the servos were holding everything in one place - and the servo immediately compensated and put the Z axis back where it was being held.

I have since removed the handwheels, not because they unbalanced anything - that is not really an issue with this kit, but because they tend to hit things (like knuckles and cables) when spinning. Once I get the cable management issue solved, I might put them back on.

I was initially concerned that the heavy servo motors and the large aluminum extrusions housing the reduction belt would be too much weight hanging off of the X axis. In practice, that has turned out to be a non-issue. The Sherline 5400 mill may be small, and may lack the power of the big mills, but it is extremely well built.

According to Fred at IMService, the white striped wire on the power connection is negative and hooks to the black motor brush. "If you reversed the polarity, the servos will fault because of the direction sensing in the encoder channels."

For reference, the motor appears to be a custom run (at least the flat) of this motor. The encoder on mine is a Hewlett Packard HEDS-5505. http://www.globe-motors.com/21en_in.pdf

4.3 Controller Box and Cables

Figure 4.3.1 - Power and Signal Cables Power and Signal cables for System 3 Pete Brown, August 22, 2004

Oops! The system was sent to me without cables! I left a message for Fred on his machine, as well as popped him an email explaining that I really wanted to get the system going by the weekend, otherwise I'd have to wait another week before I'd have a chance to play with it. Even though he was away for part of the week returning from the Cabin Fever expo, he managed to overnight the cables to me (at considerable expense to himself) so that I was able to get the setup running by the weekend. Service like that is always appreciated, and it is something that helps distinguish the good guys from the so-so guys.

Once I had the cables, it was pretty easy to get things hooked-up and running. The cables themselves are pretty basic concoctions (figure 4.3.1) . The power cable is a regular audio-type cable with power connections on one end. The signal cable is a regular old S-video cable. The s-video to servo adaptor might be made special for this job. I'm not entirely sure. I'm still considering options for cable management. I need to check with Fred to see if there are any signal problems with bundling the cables inside flexible wiring tubing.

Figure 4.3.2 - Controller Guts Here is a large chunk of what you're paying for. Pete Brown, August 22, 2004

The controller is very professional wired and arranged on the inside (figures 4.3.2, 4.3.3). Fred did tell me ahead of time that the new power supply for these new motors, and the addition of the fourth axis would mean that there will be no room for the additional coolant and spindle relays. I plan to pick up an external box and wire up a spindle relay so I don't need to remember to turn on (d'oh!) or off (after long-running jobs) the spindle. IMService sells the relays, and Fred already explained to me how to wire it up.

Figure 4.3.3 - Controller Lid The cooling fan and the e-stop switch are nice features. Pete Brown, August 22, 2004

Inside the box you can see the DeskCNC controller board. This is really the heart of it all. Unlike the Parallel-port step and direction types of controllers, this actually has logic embeded on a circuit board that speaks to the PC. The advantage of this is speed and reliability, as well as no issues with signal timing and the parallel port under non-DOS-based Windows (Windows 2000, XP) systems. The disadvantage is that you're locked into using DeskCNC as your controller software and firmware, and you will only have the G-codes they support. Time will tell if that becomes an issue or an advantage.

Figure 4.3.4 - Controller Connections The aesthetics are a little rough, but it gets the job done. Pete Brown, August 22, 2004

On the outside of the controller box (figure 4.3.4) you can see the top-mounted fan and e-stop switch, as well as the various connections on the side. The cut-outs are a little rough, but the unit functions well, and nothing is loose or delicate. The four power connections are at the top, and the four signal connections right below them. The 1/8" mini connection at the left is for the tool-setter/digitizer/sensor. The 9 pin connection at the bottom left connects to the computer's serial port, or to the USB port via an adaptor. The yellowish-green LED below the signal connections lets me know if the board is in an e-stop condition or not. For convenience, there is a green LED on the top cover that serves the same purpose.

I did originally consider getting Gecko drivers, servo motors from another source, other power supplies, and different software, but the cost quickly approached that of the System 3, and I would have to assemble it all together myself. I'm pretty competent with assembling PCs and other component-based systems. However, when it comes to building power supplies and soldering to boards, you quickly get out of my comfort zone.

During the time when I was evaluating options, I solicited opinions from people on the Sherline CNC yahoo group. Among those that replied was Fred from IMService. I sent him an email later with about a million questions in it. He got back to me explaining why he felt his system was better than the others out there. He also let me know that a new version (System 3) was going to be coming out, and that it would have different servo motors with replaceable brushes and speed reduction boxes. The feed-rate specifications he quoted at the time were pretty impressive, and have born out in my trials.

Figure 4.3.5 - The Whole Thing The full setup after I mounted the mill on a new base, installed the 10k spindle, remounted the motors, and protected the cables. The DeskCNC controller is to the right of the PC. Pete Brown, September 18, 2004

While Fred can sometimes seem a little quick to draw and perhaps over-enthusiastic about his products in his email and forum messages (how people ever survived when they communicated only through letters, I'll never know), he does not come across that way at all in person. I met him at the Cabin Fever expo in York, PA in 2004 (the weekend before my system arrived). He is a nice gentleman, and happy to help you out or answer questions you might have. This has also borne out in the numerous private emails we have exchanged in relation to his products and the various questions I have had.

I have also had great support from Ray West. Ray West is the UK distributor for DeskCNC. He runs a web site with an RSS feed here. He has no obligation to help me, having not had any part in the sale, but he has still offered advice and has gone out of his way to test things for me. Thanks Ray! If you're living in the UK or Europe and want to purchase DeskCNC, he's the guy to talk to.

One thing Fred recommended to me was to remount the motors so that I had better balance and additional clearance. You can see the way the motors were finally mounted in Figure 4.3.5. For the Z axis, I simply turned the whole assembly 90 degrees. For the Y axis, I needed to remove the motor from the reducer, turn it 180 degrees to the cables faced down, and then remount it to the reducer. The reducer was then turned 90 degrees and attached to the Y axis. That shot is of the mill with the motors remounted, the cables protected via split flex tubing, the 10,000 RPM spindle installed, and the entire mill mounted on a piece of finnish birch, coated in multiple layers of water-based polyurethane.

5. First Cuts

Figure 5.1 - First Cuts Test cutting that wheel in Freeman Machinable Wax. Pete Brown, August 22, 2004

Freeman Machinable Wax is my material of choice when it comes to producing masters and molds. The wax is non-abrasive, doesn't hurt if you get a piece of it in the face, does not produce any real dust, is non-hazardous, does not dull your cutters, and is easy enough to machine at full feed/speed. The wax will withstand the temperatures from most non-rapid-curing polyurethane resins, so you can use the wax as a mold for your master parts. I ordered my wax from Enco after trying out a piece from the Freeman materials sample package ($25 from the Freeman web site)

I have various small cutters that I use. In addition to the normal fractional inch HSS mills and the wire-size carbide end mills like that seen in figure 5.1, I have several tiny ball-end mills sized at .005", .006", .010", and .020". These are used for finishing passes as well as for machining rivets into a wax mold (the .006" cutter is perfect for most HO-scale rivets). Because of the tiny size of these mills, I am considering installing the 10,000 RPM modification on my mill. I have the upgrade kit already, but I have been hesitant due to some of the comments in the literature regarding runout. However, again the Sherline CNC forum has come to the rescue. Several people there have used the 10K RPM modification with no problems and no loss in reliability or increase in spindle heat.

Figure 5.2 - More Tests Test cutting the troop sleeper end in Freeman Machinable Wax. Pete Brown, September 18, 2004

I did later install the 10K RPM spindle. I backed-off the preload nut as much, or perhaps even more than the required 2 degrees. I found that at the full 10K, the spindle does still get very hot. Instead of running it at the full 10K, I usuall go at 5000 to 6000 RPM. That gives me a little more speed than the regular setup, but keeps the motor cool. As you can barely see in figure 5.2 to the left of the mill, I also keep a fan on the motor and spindle. This helps to keep things cooler, and has a side benefit of clearing out many of the fine wax chips. Well, at least it clears them off of the workpiece! :-)

You can see in the photo that the X axis hand wheel has been removed. I keep going back and forth about keeping those handwheels installed. They are awfully convenient for moving the axes when the controller is off (don't try when the controller is on, or the servos will keep correcting the movement), but they just seem in the way when I'm machining a part. I'm sure the next photo I post will have the handwheels back on again.

Figure 5.3 - Smokebox Front WM H8 smokebox front mold machined with .0330 and .010 mills in freeman wax. Pete Brown, January 4, 2005

FWIW, the blue wax swarf is pretty harmless. It is lightweight, but not so lightweight that it floats around the room. The edges are not sharp, and the pieces are not sticky. I need to rig up a vacuum or something, or at least put the mill in an enclosure to help reduce the mess, however.

In January 2005, on my vacation, I created simple 2.5d plans for the Western Maryland H8 smokebox door. The replacement H8 smokebox door was very simple, having no compound curves or angles. It is perfect for 2.5d machining. (figure 5.3). The circle also made it obvious that I had some backlash in my setup. I adjusted out as much of it as I mechanically could, and the results are now much more circular.

I completed the circle and the inner rectangle in two steps (two .DNC files) both using a .0330 carbide end mill from Drill Bit City (figure 5.4, green ring). If you look closely at the mold, you can see concentric rings. I get rid of those, I plan to make my next attempt using ball end mills. From the photo, it appears that I have a slight backlash problem or something as the circle has some odd dents in it. It may also be that the arces aren't being properly machined. I'll look into it.

Figure 5.4 - Tiny Mills The two tiny mills used to machine the H8 smokebox front. Pete Brown, January 4, 2005

The inner and outer rivets were done using two separate drill cycles (two more .DNC files) and a .010" sub-miniature ball end mill from discount-tools.com. (figure 5.4, red ring) On the next run, I will use a .0156 ball end mill from the same location. The .010 ball end mill produces rivets that look too small on the front of a smokebox door.

As an aside, I installed the red ring (I purchased an assortment of colors from Drill Bit City) using my sensipress. I was able to put the ring on there without damaging the very delicate point on the mill. The Drill Bit City end mills come with the rings pre-installed and labeled.

For more shots of the Wax CNC Machining I've done, check out my CNC and Casting Page here on my site.

6. Complete Parts and Items List

The information and links below is provided for reference only. When I purchased the equipment during the summer of 2004, I shopped around to get the best prices and support. When I put together this table in September 2004, I noticed that several of the items (Rhino, Sherline CNC Upgrade, pulley set etc.) have all gone up in price, many by 15% or more. Feel free to shop around for the best deal.

I have no affiliation with the companies below other than being a satisfied customer.

Sherline Items (Many distributors online)
6700	CNC Upgrade Kit for 5000/5400 Series Mills	Instructions, Purchase
4017Z	CNC Mill Z-axis backlash adjuster (recommended)	Purchase
4335	10K RPM Spindle conversion (for tiny end mills and drills - not the best high-speed spindle, but definitely one of the less expensive ones for the accuracy you get)	Instructions, Purchase
IMService Items (IMService is sole source for these items)
System 3	DeskCNC System 3 3-axis Servo System - Assembled (includes 3 Globe motors with reduction boxes and encoders, 3 cable sets, DeskCNC controller board, three servo controllers, enclosure, power supply, DeskCNC software)	Kit Information and Sales, Contact IMService for Assembled
A-axis Driver	Driver board, cables and connections for rotary table (4th Axis)	Information and Sales
A-axis Servo Motor	Globe 537A480 IM21 Servo motor (with flat and 500 line encoder) for 4th axis	Information and Sales
P0276	Probe / Toolsetter for DeskCNC	Information and Sales
Other Software (Many distributors online)
Rhino 3d 3.0	Rhino 3d 3.0 3d Design / CAD program	Information, Purchase
Misc
3/4" Finnish Birch	For the mounting base for the Sherline (after about 6 coats of polyurethane)	Information and Purchase
Split Flex Tubing / Wire Loom	For protecting the wires. I purchase Buchanan 772241 from Lowes/Home Depot. If you get the non-slit type, ensure it will fit over the cable ends.	Information
Rubber Self-Adhesive Padding	For "feet" on the bottom of the birch platform. I purchased from Lowes/Home Depot. Cut to size.	Home Depot/Lowes
Cable Zip-Ties and Self-adhesive Clips	For holding the flex tubing in place along side the mill. I had these around from my structured wiring project.	Home Depot/Lowes

7. Closing Words

I'm really looking forward to machining some parts for my various HO projects. I plan to machine some locomotive details (domes etc.), as well as replacement ends for converting the Walthers troop sleepers into the Western Maryland Troop Sleeper Cabooses and Wreck Train Cars. Once I get things going, you'll see the results of these various projects on the roster pages in my railroad section.

I eventually want to add photo-etching to my manufacturering capabilities. That's a messy proposition, however, and might not happen for a bit. That will provide the capability to produce nice side-rods, valve gear, walkways, screens, grills etc. In September 2004, Micro Mark added a small photo-etching kit to their tool offerings. The jury is still out on that one, though.

To see some of the parts I have machined, select from the links on the menu at the upper left.

If you found the information on this page useful or interesting, please take a moment to sign my guestbook. Thanks!

Model-Building Workshop - Sherline CNC Mill Conversion