Friday, December 28, 2012

Sherline Lathe - Chip Guard

I needed a chip guard for a while but I'm particular, so when I finally designed it in my mind I started looking through the scrap metal bin and found the perfect aluminum extrusion.



I was looking for the smallest screen possible, not a whole machine type cover. The only way a minimum chip shield works is if it travels with the tool bit. The chips come off of the tool bit and go radially from that point. My machine is not set up to bathe the parts in coolant so I am only protecting myself from chips and oil spray. I use a needle point tip on my oil can (see in background) and put the absolute minimum drop by drop on my work.

I also wanted to attach it the same way as the tool holders. I leave the holder post in each T slot on the cross slide and spin out the Allen screw for each tool holder change so there is always a post available to the right or left of the tool holder post in use.

Sunday, December 2, 2012

Sherline CNC MILL - Diamond Circle Square Test

The reason I went to the 20kg motor was because of the problems I was having with my millings specifically the motors skipping steps. The most important thing that I think I have done to mitigate this problem is slowing down the feed rate to 75% of top speed; 16ipm.



I performed a Diamond Circle Square test milling with the new motor and my 75% speed setting. The milling took about 30mins and went off fine.
I will provide all of the inspections data in a few days.

12.11.12
I am not a statistition but I do have a lot of inspection room experiance. This is the over - under graphic with dimensions for the DCS test.


I think that the circles are the most out of spec and because most of the dimensions came from a circle to a flat it is difficult to figure out. Ultimatley the X axis has most of the errors, Y axis is evry good.

The next time I run this test I will make two decrete runs: multiple concentric circles and multiple "concentric" squares.

Sherline CNC Mill - Motor Upgrade

Like so many Sherline owners I too had questions regrading the Z axis with respect to the motor capacity to handle the weight.
I found a 20kg - cm 6 wire motor to replace the 10kg - cm original equipment motor.
For installation I carefully reviewed the two spec sheets and  matched the color coded wires, making a temporary set up on a breadboard to test things at every stage.All went fine and the 1.8deg. motor was a perfect match but it turned in the wrong direction. Luckily for me the Mach 3 software has a reverse motor direction switch so with a few clicks I was up & running.






Unfortunately I did not get the dual ended version, I don't recommend this; you will want the hand wheel someday I'm sure.





Standardization is a wonderful thing isn't it?
I don't think I' am going to replace the other two axis right now but it would not hurt. 

Thursday, November 22, 2012

Sherline Mill - Double wide T slot clamps

I have found that with so many of my larger milling projects that clamping the maximum area is preferred especially when using 12 lb foam. Another issue is that the exact center of my Y travel is located at the front edge of the cross slide which means that these bigger millings always overhang.

I especially do not like the extra step of bonding  the blank to yet another piece of material just to have to chisel it off later.

I decided to make a gang clamp that would combine both of the standard Allen screws onto one bar giving me maximum surface area and extending a little way over the edge for added stability.


The question was how wide is wide? The T slides are 1.5" apart so right off it became at least 3", the T slot to the edge is .615" so add them up and you have 4.230" total.


I took 5/8 x 1 C channel and cut off one leg; a perfect 3/8 height without any further work.

04.04.13
I made V2 of the double wides out of 1 x 1 x .12 aluminum channel.

The goal this time was to get a deeper bite onto the tooling foam groove that I cut using my biscuit joiner.

Monday, November 12, 2012

Sherline CNC - Y axis cover

The Y axis components are very exposed, I had been trying to figure out an easy way to to cover them but always came back to the bellows. Not wishing to fabricate them from scratch I procrastinated.

Last weekend I found the answer in the basement of one of our local estate sales... the bellows from an old camera or developing machine. For $3 I picked up the full bellows, a little wider than a perfect fit but I think it looks OK.


The neat thing about the bellows is that it came with end plates and there are enough sides to make both front and rear covers. This picture shows both my camera bellows and my thin acetate front cover too.

I'll get the front cover converted to the bellows ASAP.

Sherline CNC - Setting Backlash in Mach 3

The machinists obsession with backlash is understandable and I have a healthy respect for having it set correctly on Mach 3.

I think 0 backlash is a little crazy, it can't realistically be done or is at least is not worth the effort, especially when it's not necessary. I also believe that my Sherline doesn't like low numeric backlash numbers at all, the Sherline wasn't made for it and would require expensive upgrades to do it right. It also doesn't like the ways too tight either.

 Two images take you through the Mach3 menus.
1st select Backlash from the Config drop down.




2nd: Enter in the numbers you get from your machine backlash analysis



Say OK and that's it.  I have set the Backlash speed to 25% after becoming very leery of running my machine anywhere near top speed. 

To get my backlash numbers I use the following method.


I set up a 0.200" travel indicator especially for quick and easy use.and developed the universal bracket that can be turned 90deg. or positioned anyway that works best.







Small detail; because the indicator is offset from the spindle it rotates and so the spindle must be held fixed. I made the little snubber you can see on the top that I can jam against the pulley to keep the indicator from moving.

Instead of the short travel indicators the long travel makes all the difference; I drive it at least 0.500" into a right angle plate and use the 0.100" jog mode on Mach 3 to go back & forth. I do it all real time; check the reading on the indicator, change the setting in Mach 3, hit enter and check the indicator again. 

Doing this once a year is not enough, I'm trying to do it at the start of every new project and I'm keeping a log too.

Saturday, October 6, 2012

Sherline Lathe - Dremel grinder attachment

Working with leather as much as I do I learned to sharpen things... everything!
When given the chance I love to sharpen circular stuff on the lathe; my leather hole punch is just one of the many things that works especially well when very sharp.

I had been simply holding the Dremel up to the work piece and getting acceptable results when I decided that I could make a holder mounted onto the Sherline compound slide.

Here is the set up for putting a nice point on a punch.

The Dremel has a 3/4 - 12 thread on the end so it became a simple way to attach. Because the the grinding operation is so light to the touch the plastic housing on the Dremel is sturdy enough.

The design allows a great deal of freedom in set-up.
The Dremel is about 2" in dia and the CL of the lathe spindle is .940" above the cross slide so you need a little downward angle to hit the work piece. I also wanted the ability to angle the rear of the Dremel up in order to create a hollow grind effect if necessary.

I also like to take those small grinding stone wheels and true them up before using them with my diamond dressing bit thereby getting more than just the use of the high spot due to the out of round nature of all mini grinding stones.

See my wheel dressing invention post here

My most recent project required a very precision shape. I needed to create the mushroom half of the tool set that sets an eyelet into leather. I chucked a 1/16th ball end mill into the Dremel. With both Dremel and Sherline at full speed I was able to tune the finished part to create a perfect mushroom end.

03.03.13 Update:
Today I made V2. The original design ended up on the compound slide milling device all the time so when I rediscovered the Sherline mill vice angle holder (which I have never used) I new I could leave the Dremel attached permanently.
I like this arrangement better than the above example, it keeps all of the components closer together.


Also see Dremel Drill Chuck Attachment and Dremel Grinder, Dressing Attachment posts for surface grinding usage.


04.19.13 Update:
After discovering the Sherline motor reversing instructions I went right out to get the recommended switch at Radio-shack. The installation went smoothly; I followed the wiring diagram and it works perfectly.

I put the switch where I felt it was best situated; to the rear of the housing protected by the two bumps on the electronics housing. I oriented the switch so that when pushed to the right the motor turns in the conventional direction, pushed to the left the motor turns in reverse.


The reason for the reverse with respect to the Dremel grinder is two fold;
  1. With the grinder bit on the operator side of the tool being sharpened the sparks and the grinder dust are sent down, not up.
  2. The grinder bit and the tool being sharpened are turning in opposite directions. 


Wednesday, September 5, 2012

Sherline Mill - Laser Center Finder #1

So I took the nearest laser pointer lying around and retro-fit it onto the mill.


As you can see it is not aligned to the axis of the bearing shaft. I think that the circle it makes is a little large but with a good eye it should work fine.

Finding a right laser and aligning it perfectly may be quite a challenge but it is something worth working on. I will try again.

There are two alignments that are critical:
  1. The angle relative to the axis
  2. The distance from the axis
Solving both of these is the problem.

Monday, September 3, 2012

Sherline - Tools Wish List

A couple of things are off on the machines that I have and would be great advancements:
  1. Top on my wish list is the diameter of the hole on the main shaft; instead of 13/32 it should be 33/64. this would allow up to a 1/2 in pass thru. The trick of course would be to keep all of the machine dimensions the same.
    This would be a great after market up grade: a main shaft retro-fit.
  2.  The Z axis ways are obviously deficient in Y axis stiffness. Not an easy upgrade I'll admit but for the CNC machine could be combined with a larger diameter lead screw and nut. 
  3. Sell and support Mach3 or the like on the CNC package; lets face it that Linux driver is pretty crappy. I have made the upgrade and love it.
Don't get me wrong, I would not go for any other desk top machine. Sherline has my respect because they are a complete system, these are just what I have found after years of use.

Thursday, July 19, 2012

Sherline - Digital Display

Both of my hand cranked machines are located next each other. When I added the digital readouts I decided that I would save the money and use a single readout.


So I just leave the wires clearly marked nearby and plug in whichever I'm using at the time. Mainly it keeps valuable bench top space in order.

Of course the Zm (Z position mill) display never has to come out and remains plugged in all the time. I find backlash to be a constant challenge on the Sherline machines and so just resign myself to constant fiddling and compensating.

Sherline Lathe - Tool Caddy

There are the few set up pieces I need to cover 90% of the jobs on the lathe and the mill.
My two hand cranked machines are located right next to each other.


I drilled holes into a plastic block for the:
  1. 3 jaw chuck bars
  2. A drill chuck key
  3. Large allen wrench
  4. Small allen wrench
  5. Edge finder
With these six pieces at my fingertips I can really fly!

This is truly a huge improvement with my left hand I can pick up both of the 3 jaw chuck bars at once and before the head stops spinning I am ready to release the work piece.

The T handle Allen wrench is a must for swapping out the three different tool bit holders quickly, I leave the tall T nut in the cross slide and the bolt in each of the tool holders and spin the T handle to run the bolt up and down.

Wednesday, July 18, 2012

Sherline CNC Mill - Biscuit Jointer Hold-down Groove

Its all about getting the workpiece onto the cross slide ASAP.

I often find that I simply want to mount the blank directly to the cross slide and instead of using the tall clamps and stepped riser blocks (which are a pain) I prefer to use the little clamps. Cutting a groove in the ends of the workpiece can be time consuming but not with this method.

The standard method is to epoxy the blank to a piece of plywood but that takes time and money. 

I set up my biscuit joiner to the proper depth (3/8ths) and in two seconds I have a groove into my blank.


In this case it went thru nylon with no effort.



This an example of "cross-pollination" from my woodworking experience. The biscuit joiner is a little portable End Mill that has excellent accuracy, repeatability and adjustment.

Tuesday, July 17, 2012

Sherline Mill - Quick Set - Up Machine Vice

The machine vice is of course the number one tool for my hand crank mill.



 I made a set of plates that can mount onto any of three sides and hang down below the level of the cross-slide. The result is that I can hold the vise up against the side of the cross-slide and tighten the clamps in seconds.

Is this cheating? I think not; it is accurate enough for most work, possibly as accurate as these little machines can be. 



Sherline Mill - Y Axis Extension

To start working larger pieces on my CNC Sherline I bought an 18" cross slide and lead screw. During installation I realized that the Y axis lead screw was a lot longer than it needed to be and thought of this modification.


The Z axis block is bolted to the bed plate with two screws, I decided to move the Z axis block back and use the rear fastener as the front. I then made this extension out of 3/8 aluminum angle. When I bolted it down for the final time I added 5 minute epoxy to the surfaces for added stiffness. I've been running like this for about two years. I use paper to shim the vertical axis ways into perpendicularity.

Because the Y axis lead screw nut is at the front cross slide saddle the rest of the lead screw is unused. Best of all this is a one morning project and you get about 2.0" extra Y travel for free!



As you can see the lead screw is plenty long enough to stay comfortably in the anti backlash assembly. 


This guy is on to something Laser Alignment for the Sherline Mill  *I*

Sherline - Tool Caddy

Not so much an invention but I am thrilled when something works better than expected.


Because I have my machines in two different locations I needed to have a way to bring all of the bits & pieces back & forth.

I added a robust wire handle across the top. It is great to have everything in one place; just spin it around to find what you need.

I looked around at estate sales until I found an extra  box wrench that had both 9/16 & 1/2 on it so I have only one wrench to keep track of.


Spin-O-Tray Rotating Desktop Organizer

Monday, July 16, 2012

Sherline Mill - Mechanical Center Finder

My motto is "do the easy stuff first" so I try make things easy.

Because I use my CNC for all sorts of millings from 2d to 3d, large & small I have adopted the "start at the center of the blank" rule. We know we are going to have extra stock all around so finding the work piece center is good at plus or minus ten all day.

I took a piece of 13/32 OD brass tube and added a solid brass end to it and turned it to a point.

I mark the center of my material, place it on the cross-slide, drop the pointer down, and move things around until I get the position I like, and lastly clamp the work piece down.This alleviates a lot of effort and anguish trying to bump the axis' into position.

Note the little arrows I put on the bed, with these I can get back to the center of the travel (with a few thousandth) and again for CNC work that starts in the middle of an oversize blank




This thing works great, it would be better made of steel but the off the shelf brass tube is a home run.


Of course it's not dead center; it creates a small circle if you spin it.  I will post center finder 2 ASAP.

Ultimately someone needs to invent an optical piece that drops into the hollow shaft; that would be cool!