Category: Workshop Tooling

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Rotring 300 2mm clutch pencil modification

A replacement lead pusher/ sharpener button

I am a great fan of the Rotring 300 clutch pencil that takes 2mm lead. Together with Sharpie markers these make good shirt pocket workshop assets. The pencil has one weakness … the useless ‘sharpener’/ lead pusher that always keeps dropping out, rolling under something/ getting lost, all of which render the pencil frustratingly useless.

When this happens my solution is to model and make a replacement pusher albeit without the sharpener facility. I already have a Staedler Mars sharpener (#502) which is a far better sharpener.

The choice of how to make the new pusher is either a very luxurious metal replacement or a cheap and easily replaceable 3D printed one. Both work well and below are the essential dimensions. Note that these are correct for a metal replacement but for a 3D printed one you might need to tweak the 4mm and 5.5mm diameters to suit your printer accuracy (4.25mm and 5.45mm on mine).

The 3D printed version has a natural friction that retains it in place. The metal one is a bit too perfect and needs the open end slightly distorted (crushed) to help retain it.

The pencils, spare leads and the sharpener all available on Amazon.

The final shirt pocket recommendation is the twin tip Sharpie marker. These are really useful for marking out.

Sorry that wasn’t very interesting but someone somewhere might be grateful of not having to waste too much time down on their knees looking for the useless end button.

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Kindling Cracker – a safer option

Better late than never

Four weeks ago I had an argument with my wood chopping axe. . While chopping wood against a wobbly tree stump, the stump wobbled and the axe came down on my thumb end. I didn’t feel it but it took off the tip of the bone and the severed end was only hanging on by a very thin section. My wife got me to the local A&E and a very nice paramedic cleaned and strapped things together. Since then life has been fairly miserable as I battle with buttons and being unable to do much in the workshop.

The wound is now less tender and the size of the bandage is getting less bulky. I have been warned it could take months to get any sense of feel in the tip. The problem I most stuggle with is trying to ‘unsee’ the flash back image of my thumb with its end hanging off.

In the course of recounting the incident to her golfing friends my wife was told of the Kindling Cracker. This is a wood chopping gizzmo invented in New Zealand by a young lady as a school science project . There are various YouTube videos of this device on their website. It reverses the chopping process and has the axe blade stationary with the wood being impalled in it and bashed with a club hammer. A protective ring keeps flesh away from the sharp bits.

As I have been out of action in the wood chopping department, we bought a Kindling Chopper and my wife has taken over wood chopping responsibilities. She can now split wood like a check shirted lumberjack. It is a simple but elegant design. I agree it is not as quick as chopping by hand but it needs much less effort and the chore can be delegated safely to other members of the family.

The only problem is I discovered it four weeks too late and I have got a few months left to dwell on my stupidity.

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SINO SDS2MS DRO repair

It turned out to be an easy fix

The SINO SDS2MS is a relatively old DRO control and display box. The owner of the unit brought it to me for a ‘look at’ after it had suddenly died after many years of faithful service. The internals consisted of a power supply and a PCB motherboard. The feed from the power supply was a two wire connection and the PCB clearly stated this was 5V. I isolated the connection and measured the power supply in isolation which revealed the power supply was only delivering 3V. Feeding the motherboard direct from a bench power supply at 5V brought the unit back to life. Current drawn was around 1 Amp.

I had in stock a MakerHut 5V/2A power supply that would physically swap out for the original power supply. I have used a lot of the MakerHut PSUs and found them to be very reliable. So problem solved, unit back up and running.

Reading around about the SINO units, it seems the power supply is the most common mode of failure. Comparing the size of the old PSU and the replacement unit gives an indication of how technology has changed.

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A useful Amazon sourced small item storage system

An attractive way to store small items

My capacitor storage system was a mess and the arrival of some new stock kicked me into investigating a different approach to storage.

My initial thoughts were along the lines of buying one of the many pill storage systems offered online but they all seemed to be in garish colours and overprinted with days of the week etc.

In the course of further searching I came across this enclosed set on Amazon

https://www.amazon.co.uk/dp/B0839J2TV1?

For the price being charged (~GBP10) I was dubious about what the quality would be but on delivery I was pleasently surprised. The individual cases have a good action snap shut clasp on the lid and the outer container also closes and latches well.

I labelled up the individual cases using 6mm black on white tape using a Brother P Touch Cube printer (a lovely little machine).

While my initial need was for capacitor storage, I can see one or two more of these collections appearing in my workshop.

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3D Printed Threads Modelled in Fusion 360

Tweaking the geometry

I recently posted an idea for a 3D printed depth setting jig for use on my Myford Big Bore lathe. A couple of readers had run the STL files and struggled with the fit of the mounting boss thread (M35 x 1.5) that mates with the thread on the end of the lathe spindle. This is a known problem with 3D printed threads where the accuracy of the 3D printer and the size of the thread being printed can interact and have an impact.

Fusion 360 does not have a tolerance tweak in the thread creation tool. This is not a problem in that you can use the Face Offset tool to adjust the thread geometry. This does not take long to do. The process also allows you to add fillets to the thread peaks so they are less aggressively ‘sharp’ and therefore more likely to survive longer.

Select the Inspect/Section Analysis to view the cross section of the thread to be adjusted. Choose any axis for this. Manipulate the view so you can see the cross section face and the around to the side of the 3D model. Do the tweaks shown below by selecting the appropriate faces of the thread and making an Offset Face adjustment and then adding a chamfer. The difference is very minor but it makes the thread less ‘sharp’ and aggressive to its mating half which is likely to be a metal component. If you are working with a modelled threaded hole rather than a rod then the changes are the same. The values shown are nominal and will change with the modelled thread size. If you overdue the offset the thread will become very sloppy.

The only tricky part is Manipulating the view in Fusion to allow the appropriate face selection otherwise the Offset command is straightforward.

To a degree some of this could be achieved in your 3D slicer but adjustments would become global rather than specific to just the thread geometry.

If you want a more detailed explanation then I suggest you watch Kevin’s post on Product Design Online.

I have modified the geometry of the Depth Setting boss threads to give more tolerance and reposted the STL to match on the link below.

Myford S7 Big Bore Depth SetterDownload

If you have a Myford Small Bore lathe and would like to send me the bore size and end thread I can create a new version of the depth setter to match.

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