Vice soft jaws and then soft soft vice jaws

A Different Approach to Soft Jaws

A comment that I often make is about how having varied resources available to do a job creates on the one hand a quandary as to what route to take but on the other hand it can lead to a light bulb moment. Having a 3D printer available along side a CNC machine often creates this dilemma and often to advantage. 

Stick with me on this.

I am currently immersed in creating parts for an old turret (church) clock as pictured below.   My wife put it down as a JSN job but once again the challenge it presented won the day.  

view of the church clock as delivered to me to work on
Not a pretty sight but things do seem to move and things are certainly missing.

The client found me from my blog entry about creating the Brocot wheel in CNC.   His clock as you can see is missing the pallet arbor, pallets, crutch and arbor suspension bracket.  If that wasn’t enough it also needs a new escape wheel.  This is very similar to the aforementioned Brocot wheel but smaller in size.  Fortunately the old escape wheel was still in place but in poor shape with the teeth ends fairly battered and one tooth partially missing.

I created the CAM for the new escape wheel in Fusion 360 and then from the wheel design created the geometry for the pallets.  (There is a great document created by the BHI as part of their DLC called ‘Drawing Clock and Watch Escapements’ that helped on this as did W.J. Gazeley’s book ‘Clock and Watch Escapements’). In order to check the pallet design I decided to first of all print a 3D model.   The printed part looked like it would work when tried against the original battered escape wheel.

Next step in my evolutionary process was to make an aluminium version on the Tormach CNC.   I used a superglue mounting block and cut the pallet profile for the full 10mm stock depth and down to the blue mounting masking tape.   Because the aluminium was so soft and I kept the DOC gentle this turned out well.

Although the aluminium version worked very well and helped me prove the working of the clock,  aluminium is too soft for clock pallets.   A steel set would now needed and I opted for 20mm ground flat stock as the ideal material.  

Side #1 was cut while being held in the machine vice on parallels.  A 2mm thickness of stock was left as the gripping layer.   All went to plan.

running side 1 of the clock pallets designed in fusion 360 and running on the Tormach 440 CNC mill
Side one machining of the clock pallet. An 8mm 3D Adaptive has completed and a 4mm follow on is now being run to clean up the finish.  Note the newly installed second Fogbuster nozzle.
Side one of the clock pallets completed showing the residual stock to leave as a side two operation
Finished side 1 operations and ready to invert to remove the residual stock used to grip in the vice jaws

Side #2 now became the headache.   I could have used the super glue bonding of the stock as per the aluminium version. My twitch was that this would leave very little of the pallet material remaining to act as a secure bonding face with the superglue.  Given I was cutting steel there was every chance of things parting company.  I could hold the model inverted in the vice but there was a real danger of the nib tips getting crushed.   Not a good idea.

Clearly the right solution was to make a pair of soft jaws to grip the pallet shape while I was decking off the side #2 residual 2mm.

Now here is the light bulb moment.   I designed the soft jaws in Fusion so they would swap out the existing steel jaws on my machine vice.   This is a straightforward process using the Project function.   The best demo of this that I have seen is by Cough42 and is worth a watch.

pictorial view of the pallet soft jaws to allow side #2 material to be removed
The jazzed up Fusion view of the soft jaws (red and green) and the finished pallet shape that gets gripped in them.

I was about to order some aluminium stock to make the soft jaws when the 3D printer winked at me from the corner of the workshop.  Could I print the soft jaws on the printer and get enough grip to allow the last 2mm to be decked off ?  This had to be worth a try and had the advantage that I could be getting on with another of the clock components while they were printing.

Taking this route I decided I would need to modify the design in Fusion.   The 3D printer always leaves cavities a bit under size.  I used Fusion’s Offset Faces to increase the profile shape by 0.2mm all around.  I set the gap between the two jaws at 1mm.

Print time was around 2.5 hours for each each jaw.   With CAM and setup time, running them in aluminium would have been similar.   I gained the 5 hours to do something else.  (i.e. Drink tea watching the mill ….)

The idea worked.   The PLA tightly gripped the inverted Side #1 profile while I decked off the 2mm residual stock.  I didn’t go too aggressive on DOC.

finished pallets with PLA soft jaws
View of the finished pallets with the PLA soft jaws in the background mounted in the machine vice

 A set of PLA soft jaws – not a radical idea but food for thought.   

Aluminium soft jaws are essential if you are going to be undertaking detailed feature machining of Side #2 but if it is a simple decking skim then PLA would seem more than adequate.  Soft jaws are 1 off items dedicated to a particular part.   They are consumable as is the PLA but the PLA versions are overall quicker to produce.

This has been another situation where what would have been a no brainer ‘this is how we normally do this’ turned into a ‘how else could I do this with the resources at my disposal and make life easier ? ‘.  It is that lazy side of me shining through yet again …..   

Onwards to the next phase of the clock activity.

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Mach3 alternative GUI

A Refreshing New GUI

It seems that many user of Mach3 CNC control software love the concept but hate how it is presented as a user interface.   I tend to agree as I used to tolerate it on my small CNCEST milling machine.  It is certainly not a patch on Tormach’s PathPilot.

While browsing YouTube I came across Physics Anonymous and enjoyed a rant by them about Mach4 and then the joy of seeing their version of a Mach3 GUI which I have to say was a breath of fresh air improvement.

If you hate your Mach3 GUI then have a look at what they are offering as a free download.   It isn’t totally bug free but an upgrade is promised.

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Myford Lathe ‘Bits’ Tray

A Rainy Day Job

Browsing this months copy of ‘Model Engineering Workshop‘ I was taken by the idea published in the Readers’ Tips section by Bernard Towers for his ‘Bits and Bobs’ tray for his Myford lathe.   A simple but obvious idea.  Quite often I am machining small parts or need to make drill changes and the related items all get lost in the swarf, tools and detritus that has accumulated in the tool tray.  Either that or I put them somewhere ‘safe’ on top slide and they get knocked off and lost …. we have all been there.

It was another grey and miserable lockdown day outside so the idea looked worthy of an hour or so of rewarding therapy.  The nice part about Bernard’s design was the ability to slide the tray in and out on the top slide front edge with a spring loaded T slot retaining strip.

I had inherited a stock pile of surplus nickel silver flat pack RF screening cans with one or two pieces having pre-etched folding lines that would match the size and shape needed.  Only a fourth side needing to be cut and hand folded.  Conveniently these folding lines were just at the right height for the tray walls so they would not foul the cross slide rotation.   Once all four sides were folded up a fillet of solder was run down each corner to seal it and any sharp edges removed.   Nickel silver is one of my favourite fabrication materials being rust free, strong and easy to solder.

The tray is held in place with a length of T slot material and I created this as a 3D print in PLA.   I included hex profile holes on the lower surface to take M4 Nyloc nuts.   This meant I was inverting the retaining construction as shown by Bernard.  I also used cap head screws to mount the pressure retaining springs.

A lovely and useful time filler project and I am indebted to Bernard for publishing his idea in MEW.

 

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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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CNC Work Reference Centring using Mushrooms

This is probably not original but worth commenting on.   I have a tooling plate on the bed of my Tormach PCNC440.  This has a matrix of M8 holes on 25mm spacing together with intermediate 3.7mm tooling pin holes.

Quite often I have a need to set up my work CNC coordinate system (WCS) such that it is centred on one of the M8 holes. 

If I want to do a quick and dirty centre on one of these holes then I use the Laser Centring tool as mentioned elsewhere on my blog.

If I need to be a bit more precise then I have a mushroom/top hat shaped disc with shank that is a tight fit in the tapped M8 holes.  PathPilot has a number of probing routines and these include finding the centre of a circular object.    Simply push the top hat into the desired hole and then probe the disc for centre.  You can use an active probe such as the Hallmark ITTP.

If you haven’t got an active probe you can use a Haimer.   Simply align the Haimer tip somewhere close to a maximum point on the disc circumference and advance the axis to show a reading on the Haimer.  Rock the opposite axis back and forth and watch the Haimer reading to find the high point on the circumference.   Zero the axis.   Go to the opposite side of the disc and repeat this process and divide the measured diameter by 2 for the disc centre.   Repeat on the opposite axis.

(You can use this Haimer rocking back and forth method to find the diameter high point when cross drilling a circular item to fit grub screws etc).

Hole centring mushrooms
Two examples from my ‘mushroom farm’

The mushrooms are made with a silver steel shank that is skimmed to be a non wobble (how technical is that ..) fit in M8 (~6.8mm) and an aluminium top hat that is superglued in place on the shank.   Once the glue has set the top hat is squared up while held in a collet in the lathe.  This ensures concentricity with the shank.   The disc will now sit flat to the tooling table when the shank is pressed home and perpendicular in the hole.

Clearly the larger the disc diameter the less centring error there will be.

I now have a ‘mushroom farm’ of discs for all manner of hole sizes.  It’s not rocket science but as you well know, I am all for a simple (aka lazy) approach.  Apologies to all the Grannies out there.

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