Friday, June 21, 2013

Mill: Packaging My Android DRO

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I finished packaging the Android DRO. It went into a Radio Shack project box which I machined slots in for the USB adaptors to stick out through. I wedged them in there and glued them in place with two part epoxy. I also cut a hole for the USB cable which will provide power. To mount the Arduino I secured a thin piece of wood in the bottom of the project box, which the Arduino is then screwed to.

I then used Sugru to make the USB connectors look pretty, enclose the USB power cable, and provide it with strain relief.

Thanks to my mom for helping with the Sugru molding. If you haven't used it before, Sugru is a really useful thing to have in your tool box. It comes in little packets and it's silicone rubber which sticks to most things and is moldable for 30 minutes after opening, and cures in 24-48 hours.

After that the USB cable was hot glued into the USB jack on the Arduino, the unit was tested again, and then the top was screwed in place. Done! I don't think I'll mount it on the mill itself since it doesn't really need to be. Oooooooor I may mount it.

All packed up and ready to go.

Monday, June 17, 2013

Mill: Android DRO

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First off, all credit to Yuriy Krushelnytskiy of

While poking around the internet for information on the X2 mill, I stumbled on Yuriy's blog. What really intrigued me was his DRO application for the Android:

He was using iGaging digital scales, which most X2 owners end up using when installing DROs, connected to an Arduino, which interfaced with an Android via Bluetooth. The DRO app he wrote took the input from the digital scales and displayed it in a nice interface. Just that alone had my attention since the included iGaging remote LCD displays were a little hard to see. However, since all the work is being done in software, it'll be easy to add new features to the DRO in the future. Additionally, since it's open source, you can always add a must have feature yourself. Now that Androids have gotten cheap enough and powerful enough, it makes a lot of sense to do in software what traditional DROs did in hardware. Doing it in software is just much cheaper and much more flexible.

The app is already available in Google Play Store.

Since I had my old HTC Incredible 2 Android phone sitting around I decided to use that instead of a tablet. However, Android DRO needs at least Android v.3 to run, so I needed to root the phone and load a newer Android version. Additionally, once you have Android DRO loaded, if you're using a 4" screen or smaller you'll lose the buttons on the right. To fix this the app needs to be recompiled using Eclipse, which is included in the free Android SDK. You'll need to download the source code and import the project into Eclipse, fix the broken link in the build path, add "Android 4.2.2" and "Android Private Libraries" to your build path, and then drill down to res>values>dimens.xml and change font_lcd from 100dp to 85dp. Then go to "Android Tools" and save it as a signed APK. Go through the wizard, and then use ADB to install the APK file.

I also wanted to reduce the digits displayed. Currently the app shows 0.0001" and 0.001mm, which is greater than the resolution of my iGaging scales, therefore it just clutters the screen with unusable information. Plus, good luck getting 0.0001" precision out of a mini mill. To change it I went to res>values>strings.xml and changed inch_mask to "88.888", inch_format to "00.000", mm_mask to "888.88", and mm_format to "000.00". Since I removed a digit, I was able to cheat the font bigger again, and set font_lcd to 95dp. I again saved it as a signed APK and installed it on the phone.

For the Arduino I bought the Leonardo model which comes without headers, since I like soldered connections. HOWEVER, I learned the hard way the app does NOT like the Leonardo. The app would connect, and then immediately lose connection. Once I switched from the Leonardo to the Uno R3 everything started working beautifully. The Uno R3 comes with headers, so I needed to cut them off and de-solder the pins so I could solder the leads in place.

Uno R3 with the headers and pins removed.

The iGaging scales connect to the remote readouts via mini B USB connectors. I couldn't for the life of me find a cable with a female mini B USB connection on it, so I settled for adaptors instead. I opened up the end opposite from the mini USB and soldered my leads directly to the pins. Once everything was soldered and tested I covered all the connections with epoxy.

Demo moving the X and Y axis

I bought a small project box from Radio Shack, and aside from the very annoying issue with the Leonardo, the hardest part was installing everything inside the box.

Thursday, June 13, 2013

Mill: Bench Top Precision Belt Kit

I decided to preemptively upgrade my mill to belt drive. This way I never have to deal with broken gears, and the mill runs quieter as well. Since I frequently work later at night that's a nice benefit. After researching kits for a while, I found the one made by Bench Top Precision:

It looked identical to the Little Machine Shop kit, but was significantly cheaper (prices have gone up since I bought it) so I went with it. The seller was great to work with, and the money I saved allowed me to buy additional tooling. After receiving it I see there are a couple notable difference between it and the one from LMS:
  • The LMS kit pulleys use the  the stock shaft keys while the BTP kit uses dual set screws, one of which seats in the key way of the shaft.
  • The LMS kit has you re-tighten the spindle nut's set screw. On the BTP kit it's inaccessible so instead you use Loctite on the threads.
  • The LMS motor pulley is seated down all the way on the motor's shaft, while on the BTP kit the motor pulley is visually aligned with the spindle pulley and then tightened. 

Installation was easy, and took less than 30 minutes. Please note you want to install the motor standoffs on the base plate before installing the base plate on the mill. One annoying note is the kit was a mix of metric and Imperial allen bolts, especially since the mill is all metric.

Monday, June 10, 2013

Mill: Labels

I put labels on the mill's hand wheels indicating which direction the table moves. This helps prevent me from accidentally turning the wheel in the wrong direction at the end of a cut.

Lathe: Crank Retaining Bolts

The stock retaining bolts for the cross slide and compound cranks are socket head cap screws. I was constantly hitting my knuckles on them and was annoyed by them whenever I used my lathe.

I realized that some Avid Single Digit v-brakes for bicycles come with retaining bolts with the socket head sunk into the body of the screw itself:

 They sit the lathe's cranks perfectly. The only issue is you need to put a pair of washers between the crank and dial to space it correctly. The new bolts almost sit flush with the cranks and I have yet to hit my knuckles on them again. The bolts should be available in most bike shops.

Sunday, June 9, 2013

Lathe: Cross Slide DRO

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I've wanted a DRO on my lathe's cross slide for a while to deal with the back lash and confusing dial markings. I bought s digital caliper to adapt to the role, like I've seen several people do before. However, I want to make sure I still had rotation of the compound slide. I ended up mounting next to the side of the cross slide, with the caliper's readout mounted stationary to the carriage via a bolt through the base of the display.

I wish I could give directions on how to do it, but individual calipers are built differently, so there's a very good chance what worked for me won't work for you. You just need to buy a caliper and fool with it until it works.

Even though this is an annoying modification, I'd highly recommend it just for the added usability.

Wednesday, June 5, 2013

Mill: Gibs

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I think the gibs which come with the mill are fine, except the divots for the set screws are woefully inadequate. Because the set screws aren't pushing against a flat, they tend to rotate the gib, which compromises rigidity and creates uneven wear.

To fix this I decided to machine proper flats into the gibs for the set screws to sit on. First I removed all the set screws for the gib, then installed and positioned the gib. I sharpened the end of two M4 set screws in my lathe and first installed one and tightened it down, and then tightened the other one in each hole in turn. This left exact center marks for all the set screws. From measurements it looks like the gib angle is 55*, so I used my Wixey angle gauge to set my angle vise. Since the gib wanted to rotate when the vise was tightened, I placed a section of 1/2" steel rod in the corner formed by the gib and vise jaw, and then used my table clamp set to push down on the rod, effectively locking the gib in place. I then machined the flats using a 3/16" end mill with a plunge cut. For the lock's flat I used a 1/4" end mill.  By the way, that gouge you see is what happens when your vise decides to let go of the work.

The set screws were also upgraded from the stock dog point to cup point. The last couple millimeters of the set screws were turned down so they just fit in the gib pocket. This helped position the gib horizontally and keep it from sliding on the set screws.

I also took the opportunity to lap the gib slightly, but it turned out it was pretty flat to begin with. Once everything was reassembled, the gib has much more contact with the dovetail, and I can tighten the set screws tighter without making it hard to move. It was well worth it in my opinion.

I didn't like how the gib locks looked either. They have a rounded nose which pretty quickly becomes deformed through use. 

I figured if they had a flat nose to push against a flat surface, they'd work a lot better and wouldn't deform. So it was disassembled and thrown in the lathe where its end was extended and faced flat. Since its end turns on the gib I greased it just before assembly.

Tuesday, June 4, 2013

Mill: MT3 Spindle Release

The X2 comes with either a R-8 or MT3 spindle taper, with my mill having the MT3. Aside from there being more tooling available for R-8 it's biggest advantage that it's self releasing. To release an MT3 which has been over tightened will require much beating with a hammer on the drawbar. Even release a lightly tightened MT3 means at least one hit with a hammer. Personally, I don't like hitting my mill with a hammer.

However, even though I could change the spindle to R-8 for $60, I like that MT3 offers me more Z axis clearance. I also don't particularly want to spend $60. To allow me to eject the tool without having to use a hammer, I bought an 8" C clamp for $14 and cut the end off to give it enough clearance when there's a tool in the spindle. To eject the tool I simply loosen the drawbar, put the clamp in place with the base on the bottom of the spindle and the top of it on the drawbar, and then tighten it until it pushes the tool out of the spindle.

UPDATE: I modified the bottom of the clamp to better support the bottom of the spindle.

Sunday, June 2, 2013

Mill: Gas Spring Installation

After going back on forth on whether the gas spring was worth it or not, I decided to go ahead and do it. The added Z axis travel would be nice, and getting rid of the inconsistent torsion spring would make mounting the Z axis DRO much easier.

One thing I didn't like about the install was it wanted me to drill a half inch hole in the back of the column. I'm not a huge fan of putting holes in my column. Instead, I grabbed a piece of 1.5" UHMW tube left over from another project, cut it down to 5 inches long, and then squeezed it into an oval cross section using my bench vise and heat gun. I then drilled a 8mm hole through it 4.5" from the end. One end of the gas spring is bolted through using the hole, and it's then lowered down onto the column. The UHMW tube then site on the mill's base inside the column and spaces the gas spring correctly. This way there's one less hole in my column.

On a related note, UHMW is a horrible plastic to machine. Use something else unless it's absolutely necessary.

Ultimately, I think for the money this upgrade is worth it. It's not a huge difference, but it makes the mill nicer to use and definitely made mounting the Z axis DRO much easier. It also doesn't stick up above the mill as high as I thought it would. From the picture you can see it only sits a couple inches above the motor.  

Lathe: Favorite Tool Bit

I love this tool bit set up:

It's two carbide tipped tool bits I bought from Amazon (only $3 each) and mounted back to back in a tool holder. This allows me to switch from turning to facing extremely quickly and easily. The turning bit will get a lot more use, so when it starts to dull I'll just switch the two.

Saturday, June 1, 2013

Mill: Z-Axis DRO

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Once I installed the gas spring and removed the old torsion spring, installing the Z axis DRO was super easy. I removed the ruler on the left side of the column a while ago, since it was so course it was pretty much useless. The 12" iGaging digital scale was the perfect length to screw right into the holes left by the ruler. I then quickly fabricated a bracket to connect the scale's reader to the threaded hole on the head which used to hold the ruler's indicator. Perfect.

With the addition of the this last digital scale I now have one installed on all three axes. Further down the road I really want to eventually convert the scales from using their individual displays to using an Android tablet as a DRO with this: