Jacobs chuck polishing

After spending a great part of the other day refurbishing a nice chuck I set out to fix some of the problems on the drill press.

The whole quill tube has a lot of play but turns out there’s a set screw loose that just makes it better.

I chucked a short section of precision ground bar and set up a dial indicator while I ran the pulley with my hand. The run out was around two tenths of millimeter. Tried again after moving the jaws and applying more force but the result was the same.

Some fumbling and a big hit with a punch removed the chuck from the shaft. There were some patches of light corrosion on both surfaces.

Even so, a dial indicator on the drive shaft showed a wobble of a couple of hundredths. That’s more than good for a machine like this.

But looking closer inside the chuck the taper it had machining marks, like concentric ridges. I didn’t know better when I first assembled it and assumed they were for improved grip or something.

I started the motor and lightly kissed the shaft with fine sandpaper, first 800 and then some 1200 grit until it was smooth to the touch.

Then I painted it with a sharpie and installed the chuck again. This time I noticed it was kind of a loose fit and sure enough when pulling it down only some parts were inked.

I held a drill on the vise and with a paperclip and progressively fine sand paper removed the roughness inside the cone. Now there are ink spots more or less evenly distributed and the indicator registered about 15 hundredths.

Repairing an Albrecht chuck

Long time ago I was waiting for my turn to use the weighting scale on a scrapyard when I stepped over something curious.

Inside a sturdy chunk of mud there were the remains of an electric drill but what got my attention was the keyless chuck. I asked at the counter and got it for free.

It slept for some time on a shelf until I found it again cleaning. It resisted a civilized dismantling intent so I bathed it overnight in a mix of gasoline and paint thinner.

The front came out easily and looked good enough given it’s history except for a couple of spots with tool wounds and corrosion with significant missing iron. Seems it had been passivated on the inside.

There’s a two hole pig nut on the back and that one gave more trouble. I first tried with a round nose pliers and then a punch but it only made things worse.

I used a heat gun to clear any remnant of gasoline, hoping that it would loose the threads but no cigar. So I welded a piece of scrap and with that I managed to pry it.

Compared to the rest this part looked much better. I expected a ball bearing but there was only a hardened steel ring instead.

I padded a couple of beads on the body and after a bit of careful grinding it’s like it never spent time buried.

Now I only have to fix the horrible amount of run-out and play of the drill press.


Quite a while ago (in the last century nonetheless) my idea of a productive day entailed writing a lot of code, measured by size in any suitable metric.

Lately I’ve been writing less in volume but I realize that I spend a greater time thinking about the problem at hand as a whole and that it happens mostly in the background while I’m doing something else. By the time I’m again at the workstation everything falls into place.

Also, when stepping aside and contemplating whatever I engineered I can’t help to feel anything but pride. Perhaps except for the documentation I build things from the get go thinking of what I would like to have were I a library user, on terms of building blocks.

During the last two weeks I built a library to parse a protocol called LX200 used to control telescopes and I can’t be happier with the result (for now it’s at https://github.com/telescopio-montemayor/python-lx200 ). The first one was a roller coaster, due to some other issues I went back to a night owl schedule and I can’t remember when was the last time I had such prolonged and intense periods of flow. I also taught myself asyncio.

It’s terse, concise, and (mostly) well structured. My former self would’ve made a mess of a state machine tied together with pages of if statements that worked, for sure, but was a pain to extend or correct. Of course looking down the path and leveraging years of experience this things seem obvious now.

Coincidentally, the other day Eric wrote about the advantage of declarative/table driven approaches.

Wiring progress

In the last couple of days I finished the remaining welds on the steel support and mounted it on the wall with some percussive persuasion.

I made a couple of supports:

To hang this tray from the roof beams (I also made the mess of dust and bricks):

Weekend worklog

This weekend was a bit slow.

A couple of days ago I started to learn FreeCAD, mostly for its FEM analysis mode and to build a couple of construction plans.

I made another part of the cable trays for our comms closet. Initially I wanted to use FreeCAD for that but at the end it was faster to do a bit of trig and sketch the cuts on paper. It’s held in place with a couple of rivets. I also added a layer of pvc to shield the cables from the metal edges. Fits like a glove.

Cable tray bend

I also started to build a steel support for one of the walls. We made a big opening for cables and I’m a bit uneasy about the lack of support.

Fun with a plasma cutter follows:

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Glass door

These doors were waiting a long time to be installed. Now this looks a bit more professional than before, except that on the opposite side there’s a chunk of wall missing and a lot of dust on the new hole to feed another cable tray.

Name plate and tags

Well the remote control for our transmitter is officially finished. Today as a last detail I built a couple of name tags for the cables and a bigger plate to mount on the front panel.

They are not only for aesthetic purposes but also to keep things where they should be, as sometimes they drift apart with strangers.

I cut some pieces from a scrap lamp and used the alphabet punch on them. They certainly look better with a small touch of permanent marker.

I like how they lay on the cables. All of this gives me an old time vibe feeling.

Metal name tags installed on audio and rf cables

Sunday worklog

Today I started to build the rope guides for the lightning fixture. I have some nice ground rods from a textile machine that are perfect for this.

Rope guide with rollers

On the evening I went to Futura and cleaned up a bit the stage, moving most of it to one place:

The Museum Corner at Futura

Then I started to install real cable trays instead of our improvised version with halves of water pipes. I need to cut a small section with a special bend to accommodate the opening on the wall.

Cable trays

I emptied most of the rack cabinet and installed the patchbay I built earlier. I had to drill and tap another set of holes as the power outlet interfered with the movement.

I also finished that small table:


We have this old scope for the students. It’s been unused for a while as it behaved erratically and then stopped working completely.

After setting the trigger to a more or less sane value I had something on the screen but the controls where flaky. A heavy dose of our deoxit equivalent and twisting it sprang to life. I adjusted the dc offset (drifts a bit while warming up) and matched the channel gains as much as I could and called it a day.

Fixing a Hitachi V212 oscilloscope

Lamp fixture: done

At least for now. The next step will be adding another support for the roof frame and rollers to guide the ropes around it to unblock the light path should we want to project from there.

Today I hanged the lower frame and then attached the cable trays with a set of bespoke clamps and self tapping screws.

Lamp fixture, metal version.

Today I started to replace that old wooden fixture with another one made of steel.

Our original plan was to install some cable trays to have a more industrial look.

Yesterday I assembled the frames on the floor:

Lamp fixture: metal frames

Today I spent most of the afternoon drilling the wood trusses on the roof and attaching the hooks. Then came the time to lower the old frame and hang the white on those hooks.

Letting it gently go down was easy:

Lamp fixture: dismantling the old one

I used some wire to attach the new frame to the old pulleys and help me lifting it near the roof. That seemed a lot easier on the planning stage but I managed to pull it off in a couple of hours.

To end this day I wound the new rope on the pulleys. Tomorrow I’ll hang the other frame (the black) and screw the trays to it.

Door handle

We have a discrete, and new, metal door but the inner handle is one that was in the house since the 1950’s.

On the outside there’s just a simple knob but it’s not linked to the lock. The handle works as intended but if we are not careful when pulling we end up with it on our hands.

I made a simple plate and kept the rod in place with an M4 screw threaded through it.

Looks like it came with the door:

Door handle

DTMF Remote control and sequencer

Many years ago I built a remote control for our transmitter. It was pretty simple, just a dtmf decoder rescued from an old answering machine.

It served us well for a long time, however it was lost when we moved to a new location.

For the last couple of weeks I spent a while polishing the firmware and making new boards in KiCad. The original was very crude, just a simple on/off panel and delayed power sequence.

This one adds an RF sense and automatic restart, so if one of our amplifiers bails out on a power dropout we don’t have to do anything about it.

Yesterday I etched the boards. I ran out of toner and had to ask a friend to print the transfers. They came horrible but work fine nevertheless.

It’s amazing that nowadays buying an arduino and a preassembled dtmf decoder is cheaper than the single chips (and not counting the time to layout a more complex board).

All the design files are here: https://github.com/fm-futura/dtmf-remote-sequencer

DTMF remote