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New Website!

You may notice a new look to the website and that would be because I just updated it!  If you are here to shop, it should be much easier to track down what you are looking for.  However if you are looking for an old blog post or an invoice from one of your previous orders, that will be a little trickier.  I will be migrating the old content over as time allows, but for now you can head over to http://old.desktoplathes.com and still find a version of the old site there.  Feel free to email me directly if you can’t find what you’re looking for and I will track it down.  Thank you for your support and happy machining!  -Keith

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Threading Using the 1152 Die Holder for Tailstock

Threading on the Taig lathe!  This is a quick and simple demonstration of how the 1152 “Die Holder for Tailstock” is used to hold 1″ button dies on center and enable the Taig lathe to cut standard diameter threads.

The task at hand was to make a small handle out of plastic that could be attached to a little hatch lid for closing the lid from the the inside.  I grabbed some scrap 3/4 in Delrin and quickly turned down a length to 1/4 inch diameter.  I love machining Delrin as it tends to stay rigid and you can take massive cuts.  I was removing 0.100″ diameter per cut! 

Next I installed a 1/4-20 button die into the 1152 Die Holder and attached to the tool post (threads over the dead center).  The set screws are a bit long but I suspect Taig uses them because they are identical to the ones used in the older style tool posts and they work just fine.  The tool holds the die with a snug fit that keeps it on center when installed in the tailstock.

When performing this operation, adjust the tailstock so that the die is within range of the work and the ram is set to allow it to slide by hand.  Ensure that enough travel is available in the ram to complete the threading job.  Use the ram lever to push the die onto the work and slowly turn the chuck by hand (DO NOT USE POWER).  As the die engages the work, the ram will be slowly pulled towards the part.  This is one of the advantages of having a ram style tailstock rather than a lead screw.  It is important to break the chip every turn or so (depending on the material) and use the appropriate cutting oil.  Delrin doesn’t require either of those however.

And that’s about all there is to it.  Some notes on threading other materials – as mentioned before, use cutting oil and remember to break the chip when things get tight.  Also, steels tend to be quite a bit tougher to thread than aluminum and plastic, and the 3 jaw aluminum soft jaws typically do not have enough grip to hold small round steel parts tightly enough so that they do not slip.  Instead, use the 4 jaw with hard steel jaws to get a better grip.  Also, hex stock is ideal for threading as it fits squarely in the 3 jaw chuck and will not slip (doesn’t work in the 4 jaw though!).  Here are some pictures of the installed hatch handle.  Happy machining!  -Keith

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Snapper Mower Deck Repair

I was given a heavily used snapper lawn mower a few years ago and it has been a great riding mower!  However, it was made in the mid 90’s and has several parts in need of attention.  Lately the deck belt has been jumping its pulley system every time I disengage the blades.  Apparently 20 years of the tensioning pulley pivoting on its hinge has caused some wear.  This turned out to be a perfect job for the lathe.  Here we go!

Old vs Newly Machined

For the snapper-curious, this is a snapshot of the mower deck removed.  The small pulley located inner-right is designed to function as a clutch.  Pulling on a lever results in this pulley tensioning, pivoting back, and engaging the belt with a drive pulley attached directly to the engine shaft.

Snapper Riding Mower Deck

Next we have a close up view of the clutch pulley.  You can see that the pivot pin and bushing are quite worn.

The badly worn pin was fastened to the deck with a nut from underneath.  Also the pressed bushings were badly worn and so I started by locating approximate center (relative to the wear) and drilling out until the hole was returned to round (or close enough).  Here is a shot of the final drilling operation.  Note that the wear was off center and so the new hole will be as well.

enlarging the worn bushing

After drilling out the bushing, I measured the hole and moved on to making the replacement pin.  I started by cutting off roughly 3.75″ of 5/8″ steel round.  I’m not sure exactly what type of steel it was, but it cut nicely.  I deburred and mounted in the 3 jaw.  Next is a facing cut on each end for cleaning up.

facing cut

Here you can see layout dye was applied and then the depth stop was set for a turning operation.

setting depth stop

Action shot!  The turning operation went well.  I roughed it with 0.020″ cuts (0.040″ dia per pass) and then finished with a 0.005″ pass.  Note that taking more than 20 thou would have proven difficult.  I used cutting oil with each pass and the HSS cutter held up well.

turn turn turn

Now to test the enlarged bushing with the freshly turned pin.  It fits!  Actually it was pretty tight the first attempt and so I took another couple thou off and polished it up a bit with sand paper.  You can cut a piece of sandpaper and polish your parts removing a half thou or so while leaving a nice finish right on the lathe.  Unlike when using the larger machines, in my experience it is difficult to get more than a minor cut on the Taig.

Next step is to flip the part around and turn down the section of the pin that mounts the pin to the deck.  Note how the rough cuts do not look as pretty as the final passes.  You can get a very nice finish with the round nose tool but then you are limited on how sharp the corners will be.  I wanted a 90 degree flange so I used the right hand cutter.

turning to major thread diameter

Ready for 5/16-18 threading!

ready to thread

Threading on the Taig is accomplished via taps and dies held in the tailstock.  Regular taps can be held dead center in a Jacob’s chuck while 1 inch button dies are held dead center in the die holder tool.  Caution here – all threading is recommended to be done by hand turning the chuck (and reversing to break chips every turn or so).  Threading under power is not recommended (but feel free to experiment and let me know how it goes)!  Ok, so why aren’t we threading yet?

switching to the 4 jaw for a better grip

And what’s with the 4-jaw?  I’ve found that attempting to use a die for larger (relatively) external threads on steel doesn’t go so well in the 3 jaw chuck.  The soft jaws can only grip so tight and what tends to happen is the pin will begin to spin in the chuck once the thread die gets a full bite.  There are workarounds (e.g. start with hex) but I favor going straight to the 4-jaw chuck.  It has steel jaws that can maintain a much stronger grip.  If I was thinking ahead, I would have setup in the 4-jaw before the turning operation but no big deal.  Using a dial indicator mounted as shown, you can get the runout down to less than half a thou pretty quickly.

threading steel with the die holder

Threading was only required to a depth where the nut seats under the mower deck and so as shown below, the new pin is ready to go!  You can see how much larger the new pin is and how badly worn the old one was.  I used a center drill and 7/64″ twist drill to add the cotter pin hole but forgot to take photos.

old vs new

Here is the new pin installed.  It pivots nicely with a few drops of way oil, which will hopefully last because it’s almost certain I will fail to add more oil in the future.  I remembered to add the washer after taking this photo (and after bending the cotter pin to a near un-removable shape).

new pin installed and working!

So there it is, no more excuses to avoid mowing the lawn one more weekend…  More projects soon.  Take care!  -Keith

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Mini Cannon

Mini Cannon!  Here is a quick lathe project that provides a lot of bang for the buck, ha ha.   Oh my…

BB mini cannon!

First, a note about safety.  A cannon of this size may not look hazardous but it packs quite a punch.  The barrel is very short and I drilled it large enough to provide ample clearance between cannon ball (Daisy BB) and barrel bore.  I expected this feature would reduce the effect to something closer to that of throwing the BB vs. shooting it.  That didn’t turn out to be the case.  I haven’t tried to measure the velocity but I would guess it approaches air rifle speeds based on the dent left in my workshop door.

aftermath!

This design is super simple.  I started with a short piece of 5/8″ steel round stock and turned down approximately 1/2″ from one end to a 1/2″ diameter.  This wasn’t necessary but provided a smaller end for aesthetics.  A BB measures 0.177″ diameter so I picked a 3/16″ drill bit for the bore (always center drill first!).  This leaves a little over 0.010/2 = 0.005″ clearance around the BB.  The drill bit takes a bit more than its diameter so I figured there was at least an extra 2 thou in there for safety.  The bore was made ~3/8″ deep using the tail stock and jacob’s chuck.  Next I drilled a 1/8″ hole roughly 1/4″ deeper.  I figured this would allow for a bit of powder and fuse while the BB would be held at the 3/8″ depth.  Finally I drilled a 1/16″ fuse hole perpendicular to the stock and back far enough to intersect with the 1/8″ hole.  Here is a quick sketch I made for reference during machining:

For powder and a fuse, I dug out some leftover fireworks.  Those little Saturn rockets you find for $0.25 around here have some surprisingly powerful mini cannon black powder!  The fuses slip right out and are long enough to cut for multiple shots.  Using a pair of pliers, I crushed the solid rocket fuel and poured it onto a folded piece of paper.  Next, I placed the fuse and poured a little powder into the barrel.  The photo below shows the BB simply dropped in.  Later on I discovered that nesting the BB in a tiny piece of paper towel helps to keep it from rolling out and acts as a soft seal for more powerful bangs.  For testing purposes, I used a machinist vice to hold everything for the first few shots.  The scrap paper seen here was to ensure the BB was not just rolling out.  I lost a lot of BB’s during these first few firings.

Lastly, I laser cut some 1/8″ baltic birch and hot glued it to the barrel as shown below.  The mini cannon project made for a perfect Christmas gift for my father and was one of the more rewarding projects vs. time spent.  Also, it was perfectly sized for the Taig lathe.  Happy machining!

mini cannon ready for GI Joe battles!
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South Bend Clutch Repair

I recently picked up an old 13 inch South Bend lathe and have been working to get it up and running.  Here it sits, just off the trailer and inside the garage.. yay!  The first thing I noticed was that the clutch handle swiveled freely (not meant to work that way).

The clutch worked but not well, and the set screw that locks the handle from rotating was fully set.  After taking things apart and pouring over the parts breakdown illustrations, I came to the conclusion that I must have inherited some hybrid assembly that was perhaps made up of more than one design.  Regardless, I needed something that would function like a pin and a key at the same time, so I made one on the Taig micro lathe!

Here you can see the clutch handle and set screw underneath the apron.  Pulling the handle out engages the clutch which starts the power feed.  Some of these lathes have a star shaped handle that is turned in order to engage or disengage.  This model uses the lever and allows for adjustment of the angle of the handle via set screw and collar.

The set screw was fully tightened and the handle was still free to rotate.  Meanwhile, the clutch assembly wasn’t fully engaging.  After removing the apron and disassembling, it was obvious that something was missing or mis-configured.  The collar shown here presses up against a thrust bearing which allows it to remain stationary while the mechanism inside rotates.  A shaft that you will see later is what attaches to the handle and this shaft is supposed to be coupled to the collar.  The collar has a key way while the shaft has a hole.  I decided to make a small part from key stock that would fit both the key way and the hole.

clutch handle assembly

Below is the key stock that I started with.

key stock

I mounted the stock in the four jaw chuck, off center so that only one side would need trimming.  Turning down approximately half the stock was quick and easy with a facing operation.

Here you can see the turned piece.  Next I needed to trim off the end, which could have been done with a file, hack saw, or the milling attachment.  I chose to use the Taig mill.

ready for milling

And here is the setup in a small vise.  I took light cuts to prevent the part from slipping.

milling setup

After milling, this is the finished part and the rough dimensions I had sketched up.

finished part with sketch

Here you can see the shaft with key-pin combo installed.  I still haven’t seen what the intended design was, but this works fine.  The key isn’t put under any real loads and only occasionally is under light load when adjusting the clutch handle angle.

Here is the final installation with a thrust bearing washer shown clearing the key-pin part.

All is working well with the clutch assembly now.  I cleaned out many metal shavings and replaced the felt oil wicks.  Something to note about having a bigger lathe, is that it has not reduced my use of the smaller Taig micro lathe.  Machining this tiny key stock on the South Bend would have been quite difficult.  The four jaw chuck that I have for the larger South Bend wasn’t designed to grip tiny parts.  The larger radius on the tips of the jaws would probably mean I would have had to start with larger stock and then mill down the other half afterwards.  Also, machining very close to the jaws on a larger lathe is nerve racking.  In other words, I don’t think anyone has to worry about making a Taig lathe purchase and then having buyer’s remorse if they decide to go bigger.  While in my shop, the Taig lathe will still be the right tool for many machining tasks to come.  Happy machining!

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Can Cooler Project – Part 1

This is part 1 of the Can Cooler Project (as of this post, still a work in progress).  The plan is to make a small standalone soda can cooler that can rapidly chill on demand, a single 12 oz can of soda.  Here is what I have so far!

can cooler prototype

I’m shooting for a 30 deg F temperature drop in under 15 minutes.  The basic design approach is to sandwich a Peltier element between a CPU heat sink and an aluminum cold sink that I will machine to the contour of a can using the Taig Micro Mill.  I’ve seen the mini fridge style coolers out there and from what I’ve read, they don’t perform well at all.  The USB powered versions are just silly as they’re limited to ~0.5 A at 5 V (~2.5 Watts).  Also, conductive heat transfer occurs where a flat plate contacts the base of a can.  As for the power supply, I’m using an old computer PSU and using the 12V rails to drive the Peltier element as well as the cooling fan.

Here is the Peltier element I’m using (model # TEC1-12710):

Peltier Element Part Number TEC1-12710

This is a CPU heatsink-fan combo from my junk box.  It didn’t work so well but I took more pictures of it than the other so…

Now we’re getting to the machining.  Here is a chunk of aluminum bar stock that will become the cold sink:

aluminum bar stock

Milling the surface flat for contact with the Peltier element:

I used the fly cutter to create the can diameter curvature.  Setup is easier than you might think.  First I used an edge finder to locate the surface.  Next, I moved the y axis half the can diameter away from the fly cutter.  In order to set the cutting tool for performing a boring type operation, I rotated the cutting tool as shown and slid it out until it just barely touched the material; tighten up the the cutting tool and it’s ready to go! 

using a fly cutter to bore

Making progress; I had to increase the spindle speed to 5500 RPM and take very light cuts (.002 to .004):

can contact surface emerging

The 2.6 inch diameter “boring” operation (with fly cutter) is complete:

Cold sink is almost complete – just need to cut off the end:

almost done

Cutting off the excess on the bandsaw:

Back to the mill and trimming of the excess with an end mill:

side milling complete

Ready for first power-on test!  Thermal compound is used between both contact surfaces.  The Peltier element and CPU fan are hooked up to the 12 V rail on a PC PSU.

heat sink in place

It works!  Well, it gets cold enough to create condensation anyhow: 

So this is where I realized that the heat sink was not going to cut it.  The heat sink was almost too hot to touch after just a few minutes of run time which means the cold side wasn’t getting as cold as it could.  Peltier elements run more efficiently when the hot side is not so hot.  I removed the fan and placed the heatsink in an icewater bath to see where things could go given a better heat sink.  This resulted in much cooler cold side temps and so I switched heat sinks for the one shown in the nextpicture (with heat pipes, a 120 mm fan, and lots of fins).  Now the hot side doesn’t feel hot at all and the cold side is much cooler.  In part 2 I plan to build an enclosure and post some actual performance data.  That’s all for now!

bigger heat sink!