On Topic: Gib Lock Handle & DRO

Jan 30, 2026 Last reply: 5 months ago 8 Replies

The cast aluminum (or maybe zamak) handle on the Y-axis gib lock busted and fell off on the South Bend SB1028F mill a while ago. I can get by without it most of the time, and if had to I could grab the head of the screw with a pair of water pump pliers or locking pliers to snug it down.



The X axis had started working intermittently at the positive end of the scale. To keep shop space clear I tend to work more to the positive end of the table, but my vise (the one that is bolted down) is nearer the center. For the most part I had no issues, but a couple days ago the DRO for X quit entirely.



I have five molds sitting on the mill table waiting on second ops. Mostly hinge pins and handles for lead casting molds. I do those operations on that mill.



So yesterday...



  1. I finished my household chores
  2. I chatted in the back yard with my son's BAJA SAE team about planned track layouts (simple easy oval right now).
  3. Took my mom to a doctor's appointment.
  4. Drove partway home, and then went back to the doctor's office so she could look for her phone.
  5. Finally went home.
  6. Walked back out to back field to chat with the rest of the BAJA team about track plans and track usage.
  7. Finally headed in the shop.
  8. A new (different style) handle for the gib lock screw.
  9. Repaired the DRO.

The gib lock handle is best explained with a picture. I used a technique of plotting points on a curve and then plunging with a a parting blade to rough the shape, and then finished with a file and emery cloth. Its a very old school technique, but its the first time I've done it. The I do the rest of the work on the mill without a working DRO or Y gib lock. I think I used the dials on the machine for the first time since I got it.



I checked the axis by swapping glass scale cables, and the problem was not in the display head. Then I pulled the cover and blew out the scale. No luck. I loosened the screws on the read head and a shim fell out. The DRO seemed to start working again, so I tightened the mounting screws, and tested. It seemed to work just fine. Even seemed to read about right running all the way to the positive end of the table, but when I ran back it quit working again.



Of course twice I had to dig through the huge pile of aluminum chips under the machine for screws I dropped in this process.



There were two things I could think of. Maybe the glass scale was damaged (or maybe it wasn't a glass scale) or very dirty, or maybe there was an alignment issue. I measured fromt he top of the housing to the top of the table with a guess-o-meter (dial caliper) and found slightly over 25 thousandths difference from end to end. I measured in the middle, and put both ends at about the same distance to the table top plus or minus a thousandth or two. Pulled the read head up as close as I could, and tightened all the screws. Then I ran the table from stop to stop listening very carefully for any dragging. It sounded good and I got 36.45 inches stop to stop like I have written down. Actually I can run slightly more, but I have an electric power feed stop set at each end of the table to prevent that particular crash.



By then I was about done even though it wasn't that late. I headed into the house and made myself a Bacardi and Pepsi Zero. I watched the latest episode of Starfleet Academy on Paramount, and fell asleep watching Fallout. I woke up just in time to see the large beastie knock the guy in the bottle armor through the wall opening up the area where they were contained to the rest of post apocalyptic Vegas. Yeah, bed time.



And that is what I did yesterday instead of going fishing.



Yowza! Really nice handle you made there Bob👍️

That is a pretty handle ! I'm surprised Bob doesn't have a ball turning attachment for one of his lathes though ...

I started to make one a gazillion years ago, and never finished it. A few times I've thought about making one to make ball mounts, but... unless I just take time I never have time to do the things I want.

The few round features I've done I usually CNC on a 4th axis, and then just finish/polish on the lathe. Its amazing how close you can get that way.

The thing is the point list and file works. First time I have done it, but the the 4th axis and polish is a close facsimile of the process. Basically the same process, but starting a little closer before finishing.

On thing I do fairly often that would really benefit from a ball turner is radius turning the end of insert rods, but usually I have a round over mill close enough, and just use it like a lathe bit. Gunner once told me about a really fast tool for radiusing rod ends, but when I looked it up it was crazy expensive, and you had to have one for each size rod.

I started to make one a gazillion years ago, and never finished it. A few times I've thought about making one to make ball mounts, but... unless I just take time I never have time to do the things I want.

The few round features I've done I usually CNC on a 4th axis, and then just finish/polish on the lathe. Its amazing how close you can get that way.

The thing is the point list and file works. First time I have done it, but the the 4th axis and polish is a close facsimile of the process. Basically the same process, but starting a little closer before finishing.

On thing I do fairly often that would really benefit from a ball turner is radius turning the end of insert rods, but usually I have a round over mill close enough, and just use it like a lathe bit. Gunner once told me about a really fast tool for radiusing rod ends, but when I looked it up it was crazy expensive, and you had to have one for each size rod.

Bob La Londe CNC Molds N Stuff

------------------------------------ That looks nicer than I would have the patience for when I needed to use it. Afterwards it could be prettified.

I ran through the G coding exercise on an Emco 5" CNC lathe and the parts came out correctly. If I pick up 3D CAD well enough in night school I could get into CNC and 3D printing, though I see limited use for off-sized, cut-and-try repair parts.

For small radii I grind the final edge on a quarter round concave lathe bit with an upright conical die grinder stone, which gives smooth roundness and cutting edge relief, though not precise size without care but that doesn't matter for hand levers or bolt ends. My Multifix tool post allows rotating it. Round shaft radius cutters are harder to hold securely without damage.

I turned two cast iron 5/8th spherical balls of around 3" diameter (as large as would clean up) from the halves of a dumbbell by using a spreadsheet to generate the X,Y coordinate list. I made the step size and roughing offset constants, changed between passes, to speed the roughing process. The final small steps removed little and went quickly and filing to barely remove the tool marks made it adequately spherical, they are the swivel feet for a shear leg hoist.

The sockets are stacked plywood turned concave by rotating the compound, which works reasonably well on wood and aluminum. I'd have to make an offset tool bit holder to cut spheres with the compound and the diameter is limited to 2". I like the look of purchased brass balls on handles that needn't be balanced. On the mill the brass ball's weight keeps the spindle and up to

1/2" drill chuck up.

The equation for a circle is R^2 = X^2 + Y^2. I rearranged it to make zero the right end of the blank and used a dial indicator to measure carriage position, starting in the middle to infeed the bit both ways. R was the sum of the ball and rounded bit end radii.

The TV News just mentioned that Boston is colder than Antarctica today. They predict -12F tonight. The Pilgrims had no idea how harsh the winter here would be at the same latitude as Rome.

If you have a set of radius gages (or at least the one you need) you can get a lot closer than you think.

Could you generate the ball rather than use a ball turning attachment like here

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, might need the 4th axis tilted. Could be done on a lathe if a similar rotating cutter was fitted in place in  the toolpost. A machinist I used to know did a helical machining job on his large lathe by fitting a Bridgeport M head in place of the compound and ran the lathe as when thread cutting, worked very well judging by the results.

If you have a set of radius gages (or at least the one you need) you can get a lot closer than you think.

-- Bob La Londe CNC Molds N Stuff

------------------------------ My sister gave me a radius gauge set for Christmas, in exchange for garden tools. I measure the diameter of the conical stone at the bit cutting edge. I've shaped two gear cutters by visual comparison against a light and they came out well enough.

Using bright light to fit a hand sharpened plane blade to a try square was a test we had to pass in 8th grade wood shop, as was filing rip and crosscut saw blades. We learned old timer precision without power tools and I used the skills on the lovely 1825/28/30(?) house my father was restoring and updating from 1920's plumbing and wiring and coal heat. Door hinges etc had to be closely hand mortised wherever they were, which became my job. The house had settled a little and nothing was exactly square, doors that no longer closed had to be refitted, sometimes elsewhere. With the Shopsmith we made custom cabinets with wood or glass panel doors and tongue-and-groove flooring long before big box stores provided them.

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It's more modern inside now. Mom had a nice collection of early American antiques that my sister has in her 1790 house.

When Dad had done enough with the brick house he bought the big grey house next door and converted it from a funeral home into nice apartments. The big tree beyond the white fence is a Linden, one of many uncommon types there including Chestnuts.

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