First screw threads cut using Clough42 electronic leadscrew

Metric Threads on an Imperial Lathe

You might well have read my write up on how I implemented the Clough42 Electronic Leadscrew on my Myford Super 7 Large Bore lathe.

While I have been successfully using the ELS as an automatic feed, I had put off attempting screw thread cutting.  You know how it is.   Screw cutting is nagging at you to try, but it is on the ‘too difficult’ pile pending other more interesting jobs.  There is always something else to do, so you kid yourself it is justified to put it off until another day.  Well another ‘lockdown’ day dawned and I decided today was the day.   

My experiences are recorded here as a full write up

Screw cutting using the Clough42 ELS

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Machining a job that is outside a milling machine’s table travel using Fusion 360

Introduction

This write up is not for the purists with years of experience but is an explanation of how I thought through how to machine something over size that would not fit into my Tormach PCNC440 milling footprint as a single operation.  Hopefully it might help others to grasp the process.

The challenge began when a local turret clock expert came to me and asked if I could machine a new Hour and Minute Hand for a clock he was working on.   The Hour Hand was around 14” long and the Minute Hand some 18” long.   

Here is the Fusion 360 view of the minute Hand.

clock minute hand milled in three steps

Clearly these lengths were way outside the 440 table X movement (10”) so a plan was needed.  There then followed a lot of staring into the distance at mealtimes and also at bedtime accompanied by vocal “hmmm”s as I tried to mentally visualise what was needed.  This idiosyncrasy is something my wife has come to terms with over the years…..

My conclusion from this mental preparation was that I needed to be able to accurately step the stock across the tooling table and then take two or three bites at the profile machining.  

What follows would almost certainly benefit from a video but sadly I am not set up for this. 

Click the link below to download the PDF document.

Milling an oversize object

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Stevenson Collet Block and the Angle of Dangle

Often a project comes along and it has you scratching your head how to go about it.   

The following job was simple and it could have been hand filed but my preference was to machine it.  The fact that I needed to make two added to my thinking.  (aka – I am fundamentally a lazy person …. and I follow my father’s adage that if a machine can do it a human shouldn’t)

You can simply regard the challenge as looking like a screwdriver blade but I needed to have it with the flats exactly on opposite sides, the end of the flats needed to come together to a defined blade point thickness (0.3mm) and the length of the flat taper had to be a defined length (30mm).   Here is a simple sketch.

taper milling

What I am about to describe is not magic and I am probably teaching many a granny to suck eggs (is this a universal saying or quintessentially English and how did it originate ?) but it might help someone somewhere save a few minutes of their life.

Stevenson Blocks in my opinion are the most elegant pieces of workshop tooling ever invented.   They consist of an accurately machined block of steel with an ER collet mounting.   Really quite simple.  They come in different ER sizes and the block can be square or hexagonal cross section.   These are they below and ArcEurotrade are one possible source.

stevenson collet blocks

If you have to machine a square head or hexagonal head on a piece of round stock they make the job so easy to run and make the result uniform, symmetrical and central.   Likewise centre drilling of round stock becomes so much more simple.  IMHO no workshop should be without Stevenson’s Blocks.

Back to the job in question.   I drew out the geometry and calculated I needed to set the 5mm round stock at an angle of 4.48 degrees.  Non scale sketch below.Angle calculation using Tangent Rule (Tangent rule – I can’t remember opposite and adjacent etc and remember it instead from – “Some People Have Curly Black Hair Through Persistent Brushing” where B = Base, H = Hypotenuse and P = Perpendicular).

I could have simply set the stock in the milling vice at the required angle but it would be a real pain getting it correct and protruding the right amount to skim flat. The resulting set up was as follows and you can see how the Stevenson Block came to the rescue.   

The 5mm stock was faced off and then marked at 30mm from the end and with a score line and then mounted in the Stevenson Block.

setup for milling round stock at an angle

My angle setter just fits nicely on the Block surface and has a magnetic base. This setup makes it so easy set the stock angle by  ‘hinging’ the Block up and down against the bottom edge of the Block and the angle plate surface.  (Clearly for other angles the height of the hinging point support would need to change).

Once set, the cutter is traversed in ‘X’ up and down the stock until the run out point coincides with the 30mm mark. Once the first side is cut, the stock and Block (could this be the name of a pub for engineers ?) are rotated 180 degrees which is fix defined by the Block lower surface edge.  The second side can now be run.

complete assembly set up for taper milling

I said it wasn’t magic but it beats filing and is far more accurate than I would have achieved by hand.   Good result.

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A Lazy Cable Clamp using 3D Printing

This is nothing magic but worth a mention.   Being fundamentally lazy I don’t like to assemble and solder electronic multi-way connectors.   There is never enough room to work on the contacts and the cables never lay up how you would like them to.  This could have course be a function of my eyesight ..

I am currently working on boxing and installing the Tormach USB Expansion Board which has a USB connector interface.   I wanted the cable to pass through some form of gland into the box but didn’t want to cut a standard USB cable and remake the connector at one end of the other.   

After some head scratching I came up with the following simple cable gland/cable grip.  It is nothing revolutionary but made life easy and the parts only took 20 minutes to design in Fusion 360 and then 3D print on the Sindoh 3DWOX.

It has two identical semicircular halves that hold the cable and there is a ring that pushes over these on the outside of the box.   A small flange holds these in place on the inside of the box. The hole in the box and the ring inside diameter are both 16mm to allow the USB connector largest dimension to pass through.   This is also one of the standard cut rings on a cone cut hole drill which makes cutting the hole in the box very straightforward.

The component parts (two halves and the retaining ring)
Inside view of the gland showing the retaining shoulder on the two halves
Outside view of the cable gland showing the retaining ring

Not rocket science but you never know it might come in useful and the dimensions can be tweaked to suit other cables and connectors. Similar or related subjects : –

Mill Turning Jig

After a few distractions the Mill Turning Jigs are complete and I have run a test piece that is representative of a clock pillar.

Mill Turning Jigs

The jigs were both designed in Fusion 360.   One consists of a large block with space for three 10mm cross section carbide insert tools and a second block with drill and boring related tools.   I have fitted three ER16 collet chucks to this to allow flexibility of tooling choice.  Both have mountings to fit onto my 25mm hole matrix tooling plate on the Tormach.

The jig manufacture was relatively straightforward with the exception of needing a new 10mm end mill having extended length (35mm) to bottom out the ER16 collet mounting holes.   I got this from APT and the edges were lethally sharp.

Design in Fusion 360
Mill Turning Lathe Tool Holding Block

Fusion 360 design
Mill Turning Drill and Boring Jig

Trial Clock Pillar

The pillar had simple geometry as below.

Simple Clock Pillar Trial Cut

I opted to base this on  the largest pillar I had come across in any design which was formed on a 5/8″ brass rod.   I held the stock in the spindle in a 16mm ER32 collet held in a TTS holder.

I struggled a bit with the CAM for the trial as the tool geometry of the tools  I recently received from Banggood were not in the standard tool library.   I got some of the settings wrong.  That aside the result of the first run is quite pleasing.

My feeds and speeds were a bit coarse and I cringed once or twice at the tortured sound of brass under pressure.   I didn’t complete the parting off as I didn’t fancy ducking from a large piece of brass spinning lose at 5000 RPM.

Mill Turning Setup showing both Jigs in place

Zoomed view of Trial Cuts

As ever there was quite a bit of learning while making both the jigs and running the trial pillar test piece.

Drop me an email if you want more information !

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