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MachinistBlog.com

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

New V-belt makes speed changes easier

Changing the spindle speed of your Harbor Freight 8×12 or Lathemaster 8×14 lathe will probably be easier if you replace the factory belt with a size 3L300, which you can buy at most auto parts stores for about $5.  The original is so tight that changing the spindle speed by moving it to a different set of pulleys can be an unpleasant chore.  Richard on the Lathemaster Yahoo discussion group discovered that the 3L300 is just a little bit bigger and it makes speed changes much easier.  I tried one, along with others members of the group, and we found that he was right.

Mine was made by Dayco and I bought it at a NAPA store.  Another store I’d visited didn’t have one in stock and they tried to sell me a heavy-duty version which I declined, because it cost twice as much and I didn’t think I needed or wanted a heavy duty belt.  (Addendum 3/18/2011:  I’ve heard that the Gates 6730 belt is the same size, 3/8 x 30-inches  or 9mm x 760mm.)

Carriage Lock Modification for 8×12 or 8×14 Lathe

This is Steve Shyver’s carriage lock modification for a Harbor Freight 8×12 or Lathemaster 8×14 lathe (both lathes are the same size if measured the same way).  His handle replaces the easy-to-misplace hex wrench that comes with the lathe.  Its longer length also makes it easier to turn.

Steve made it using a M8 stainless steel cap screw with a press-on cap he fabricated.  The cap allows the handle to be adjusted so it’s in the proper position when unlocked.  To allow some additional adjustment he put a loose-fitting thick washer under it that can be made thinner to change the position of the handle.  Less than a quarter-turn is needed to lock the carriage.

Steve also told me how to fix a small problem I was having with my 8×12.  I had to really tighten the locking screw to keep the carriage from moving.  Steve told me that less force would be needed if the two M5 cap screws to the right of it were a little loose so the brake “shoe” could rock and pull up against the bed when it was tightened.  The two screws can be seen under the handle in Steve’s first picture.

Steve can be found on the Lathemaster Yahoo Discussion Group, which is a good group to belong to if you own a 8×12/14, 9×20 or 9×30 lathe.

Photos by Steve Shyver (The SteamshipCO).  Text by Rob.

4×6 Bandsaw Cart

This is the roll-around stand I made for my late 80’s Taiwan-made 4×6 bandsaw, which is almost identical to the one Harbor Freight sells.  It uses a Harbor Freight 3-shelf service cart with the top shelf turned upside down.  I was a little worried about it being top-heavy so I replaced the original 5-inch casters with 3-inch ones mounted on outriggers made from pressure-treated 2x6s.  Now it’s much more stable because the wheels are farther apart and it has a lower center-of-gravity.

The 16×30-inch steel cart was on sale for $50 and I used one of HF’s easy-to-find 20%-off coupons to save another $10.  The casters were also on sale.  I think they were $4 a piece.  My scrap bins provided the wood and the 1-inch aluminum angle I used to fabricate the brackets that attach the saw to the risers.  I splurged about $8 on a tube of Minwax “Crimson Red” Express Color stain so the wood would compliment the red color of the cart.  The stain was a lot quicker and easier to apply than paint.  I still need to find a suitable hook I can attach to the cart to store its extension cord.  As you can see there’s lots of room on the middle shelf for a coolant pump and reservoir, if I ever decide I need to add one.

The sheet-metal stands these saws come with are a major source of grief, so putting the saw on a another stand is a popular modification.  I learned about using one of these carts on the Yahoo 4×6 discussion group.  Another popular method is to mount the saw on top of a 2-drawer filing cabinet that has been mounted on casters.  If you browse the group’s photo archive you’ll also find some nifty designs for welded steel stands.

I’d wanted one of these bandsaws for a very long time but I didn’t think I had room for one.  For years Harbor Freight regularly had them on sale for $160, but of course once I needed one I found the sale price had gone up to $230.  I was ready to pay that but I decided to check Craigslist one more time.  I couldn’t believe it when I found this one for $50, which included a brand new Lenox blade which was probably worth at least $30 by itself.  I had to replace the power switch but it works great and I get very square cuts with it. Continue reading 4×6 Bandsaw Cart

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You miss 100 percent of the shots you never take.

— Wayne Gretzky