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Plans, projects and how-to's for home machinists

Dial Indicator Helps Set Z-axis Height

I bought an old Federal dial indicator from a retired machinist that had a big flat donut-shaped magnet glued on its back.  I almost passed it up because it was kind of ugly, but it has turned out to be one of the most useful tools in my workshop.  It is particularly useful for adjusting the Z-axis height on my Harbor Freight mini-mill.

I’m a little mistrustful about dialing in the height because of the huge amount of backlash in the Z-axis.  So I often stick my DI on the column and use it to set the height or to double-check the dial and make certain I haven’t miscounted the number of turns I’ve made.  It only has a range of 1-inch but that’s all I need most of the time.

It was really helpful last night when I needed to remove a very small amount of metal using a fly cutter.  The indicator showed that the head was dropping another 3-thousandths when I tightened the gib lock (which is one way to protect yourself from the mini-mill’s infamous “head drop problem“).  I hadn’t experienced that problem before and I hope the gibs just need to be adjusted.

A couple of potential problems

To get the most accurate reading your indicator’s plunger needs to be perpendicular to the head.  Instead of eyeballing it I’ve thought about building a magnetic mount for one of my other indicators that would slide up and down against the column’s dovetail.  It would make it easier to position the indicator and ensure it’s always perpendicular.  I didn’t have a big enough block of aluminum the last time I was going to make one and this morning I was wondering if it would be easier, cheaper and faster to just buy another column stop and modify it to hold an indicator.

And lastly, a more experienced machinist once told me you can ruin a cheap poorly-made dial indicator by sticking a magnet on it. Continue reading Dial Indicator Helps Set Z-axis Height

How I tram my mini-mill

This is how I tram my mini-mill.  I think the method I use is fairly common, although I may use slightly different equipment than others.  There are other ways of doing it and some people have strong opinions about which way is best.  I’ve included links at the bottom to some interesting discussions I found if you would like to learn more.  If you don’t know, tramming is the process of adjusting the mill’s column so the spindle is perpendicular to the table.

By the way, this procedure only trams the X-axis.  Unlike most other mills, the mini-mill’s Y-axis is not adjustable, although there are ways of doing it if you’re willing to go to the trouble.

My Equipment

  • A matched pair of 1-2-3 blocks
  • A digital dial indicator
  • The fine-adjustment arm from an inexpensive magnetic base for a dial indicator held in a 5/8-inch cross-drilled piece of drill rod mounted in a collet

I started using the arm from a magnetic base because it was the quickest and easiest way to mount a dial indicator so I could read it from the sides of the mill.  It replaced a home-made one that had the DI facing forward (good) and to rear (hard to read).

If your mill vise is big enough you can measure on the top of it with a dial test indicator (DTI) and tram your mill that way.  The vise shown in the picture is probably big enough to do that.  But the screwless precision vise I often use isn’t, which is why I use the 1-2-3 blocks, a trick I learned from someone else.  The blocks will also allow you to tram your mill without removing the vise.  I also believe you can get better results by taking your measurements farther apart.

For Best Results

Before you get started you should swing your indicator from one side to the other a few times to make certain you get repeatable measurements and there is no “play” in your setup.  You should also center your table under the spindle and make your measurements on its center line and at the same spots each time.

You should know that tramming your mill’s table does not guarantee your vise will hold your work pieces square with the spindle.  It should if it was made properly.  If it doesn’t you should find a way to fix it, consider getting another one or tram your vise instead of the table.  I’m talking about your vise being square with spindle, not with the table.  That’s also important, but it’s different topic.

One way to check your vise is to tram your table, mount a long parallel in it, and then measure at the ends of the parallel with your indicator.  It should be just as perpendicular to the spindle as your table, or pretty darn close.

It’s Easier with a Digital Dial Indicator

In the past I’ve always trammed my mill using a traditional dial indicator with a needle and dial.  Sometimes it would take me just 2 or 3 minutes but other times I’d be scratching my head for 10 or 15 minutes and wondering what the heck I was doing wrong.  It was usually because I’d gotten confused reading my “analog” indicator, which is easy is for me because as an amateur machinist I don’t use one very often.  So the last time that happened I took my old indicator off and replaced it with the new digital dial indicator I’d bought from Harbor Freight for about $25 (with a 20% off coupon).  It instantly put an end to my confusion.

The Procedure

The procedure is simple with a digital indicator.  Swing your indicator to one side and zero it.  Then swing it to the other side.  If the measurement is “negative” then push the column toward that side half the distance shown on the indicator.  If your measurement  is “positive” then push the column away from that side half the distance shown.  Then zero the indicator again and swing it to the other side to check your work.  You want to try to get the same distance on each side,  although I wouldn’t worry too much if you’re only off a thousandth or so over a good distance (my setup takes measurements about 10-inches apart).

If your indicator has a needle, then use it to find out which side has the shortest distance between the indicator and the table, and then “zero” it or write down the measurement.  Then swing it to the other side, calculate the difference in length and push the column toward that side half that distance.

Before you can adjust the column you’ll obviously have to loosen the big nut on the back of it a little.  There’s a good chance that the column will move slightly when you tighten it again, so re-check the tram.  I’ve found you can minimize that if you loosen the nut just enough to allow you to move the column by gently tapping it with a rubber mallet.

More information

CraftKB: How to tram a Sieg X2 mini mill

Practical Machinist Forum: How to tram a mill for best surface finish / flatness?

Wire Rack Attack!

This short video shows a simple low-cost method for organizing small reels of wire.  I found it on Makezine.com’s blog, which recently featured a couple of our articles.  One was Mikey’s contest winning essay and the other was Nate’s short article about some free plans for a Watt-style steam governor.

I’ve been working very hard lately at reorganizing my workshop and getting rid of stuff that I don’t need or rarely use.  I really need to make more space because I now have two lathes, two mills and a couple of friends who have been coming over to use them.

Installing a Drill Press Chuck

Properly installing a drill chuck on your drill press requires you to pay attention to a few simple details.  Done well, your chuck will be accurate and will stay put until you remove it.

Drill presses and many other machine tools use Morse tapers to enable the user to attach a wide variety of attachments to the machine via an arbor having a Morse taper to fit the machine and an opposing taper to fit the accessory to be attached. For a drill chuck this opposing taper is typically a Jacobs taper.  An accurate arbor is very important so buy one you can trust; Albrecht and Jacobs make good ones.

Fitting a male arbor taper into a matching female taper produces interference-fit joints that are very tight and accurate.  Once their contact surfaces are brought into intimate contact they will lock as long as their surfaces are burr-free and clean.  Since these tapers are ground to a high degree of precision they are also self-aligning.  When installed correctly the arbor will go in straight and stay there unless someone beats them out of alignment with multiple blows from a hammer during or after installation.

To install an arbor:

1.  Wipe the arbor and socket with a clean rag.  Don’t bother with solvents for now – we don’t want a lock yet.

2.  Inspect the socket and arbor and completely remove any burrs found with a diamond coated tool or fine file.  An Eze-Lap diamond hook sharpener works really well for removing burrs from a chuck taper.  Note that even new chucks and arbors can have burrs so don’t assume its okay because it is new.

If you gently spin the arbor in the socket any burrs will usually produce a bright line that is clearly seen.  If the bright line is on the arbor then the burr is on the chuck taper, and vice-versa.  Work on that burr until it is gone.

Smoothing a burr so the defect lies beneath the surface of the taper will not prevent a good fit as long the rest of the taper is untouched.

3.  Once all the burrs are gone use OOO steel wool or a Scotchbrite pad and lightly go over the taper and arbor to remove any invisible dirt or superficial oxidation; do this even with new arbors and chucks.

4.  Now use lacquer thinner or acetone on a lint-free rag (clean old T-shirts work) and clean the socket and male arbor surfaces; after this do not touch these surfaces with your hands.  Rubbing alcohol contains oil and won’t work well on tapers.

5.  Retract the jaws of the chuck into the body and place the nose of the chuck on a solid, clean, flat surface like an anvil or smooth level concrete, not your wooden work bench.  A sheet of paper laid down first will prevent marring the nose of the chuck.

6.  Slide the male arbor end into the chuck’s socket with a gentle twisting motion and it will self-align.  You can cock an arbor when pushing it straight in – trust me.

7.  Position a piece of wood over the end of the arbor and use a steel hammer to deliver a single firm tap straight down onto the end of the arbor.  You do not need to hit it with an overhand, powerful blow – just a firm tap, please.  With the chuck sitting on an unyielding surface this simple tap is all that is necessary to seat the arbor.  Try to resist hitting it more than once. If the arbor and socket were clean and burr-free that arbor will stay in there until you take it out, and it will run true.

To install the chuck into the drill press you must do the same prep work as above.  Move the table out of the way so you can work.  Slide the chuck (jaws still retracted) and arbor into the socket with a gentle twist and, protecting the nose of the chuck with a piece of wood, deliver a single firm tap to the nose of the chuck.

Your chuck is now installed and should stay there until you need to remove it.  When you do need to remove it, it will come out easily.

Now let’s go make some chips!

Mikey
September 2010

Random Quote

Don’t be upset by the results you didn’t get with the work you didn’t do.