Skip to main content

Screw Cutting The Square Thread-Brake rod (Part 3).

 Screw Cutting The Square Thread-Brake rod (Part 3).



Hello again. (To put a face to the Blog)
 

The brake rod threading is still very much in the practice stage—we’re now on part 3. Screw cutting is proving to be a real skill to master, especially when it comes to achieving the correct thread form and overall appearance.

The latest attempt (shown above) still isn’t quite right, but it will be used as the basis for making a tap. The plan is to produce a clean, symmetrical thread, then mill flutes into it and case harden it. This tap will then be used to cut the bronze nut so it matches the thread that will be machined onto the brake shaft.

The current issue is with the pitch-to-width ratio. I used a 1.5 mm cutter for this test, but in hindsight it really needs to be closer to 1.25 mm to achieve a proper 50/50 tooth-to-gap ratio, which I wasn’t able to get here. The drawing specifies 10 TPI (2.5 mm pitch), and while I’m close at 2.55 mm, the groove width of 1.6 mm is too large.

Next step is to reduce the parting blade width to around 1.25 mm and repeat the process.

As a passing mention to my father he said "you have never done screw cutting, and is a big part of lathe work" however my previous engine I simply used a die to produce a metric thread, and being on a 1inch miniature looks fine. This time I intend to do it properly, however as he's is no longer with us Its threading by trial and error. 

The 2nd attempt 😉

 After a few scrap attempts, I'm close to tackling the actual part. I decided first to make a tap to match the brake rod thread, with the aim of producing a one-off tool to cut a bronze nut.

The tap is turned and threaded, with flats milled on the back for a spanner. It still needs the flutes cutting with a ball end cutter and case hardening, but the idea is a soft-core tool with a hardened outer layer—tough enough to avoid snapping, yet hard enough to cut effectively.

Next comes cutting the flutes, adding a slight lead-in, and hardening. With careful use, it should do the job it’s intended for: producing a single, clean internal thread. (And saves £24 on a tap).


Feel free to leave a comment !!     stephen.meredith1@gmail.com

If you have any questions while reading these blog updates—I'm always happy to reply.

If you would like to see more photo's from the archive, I have a Flickr page:  https://flic.kr/s/aHsmJ9LEH6

Until Next month, stay safe, make swarf and be the best you can be.
Labels:

Comments

Post a Comment

Popular posts from this blog

1" Minnie Traction Engine By Stephen Meredith   Background Working Progress (Gears) Front End Parts Following the completion of a small marine steam engine "Trojan Engine", I decided to tackle a larger project. Having visited various shows and the model engineers Exhibition, I decided to buy the Construction book for building the popular 1" scale 'Minnie' traction engine. The initial workshop experience was limited but keen to learn, and research has enabled me to get it this far. A s can be seen, this is basically finished well almost, it steams, and runs well a few tweaks are needed but tweaks don’t make piles of swarf. The intention was to show the engine and run it, at rallies but what I really wanted was a capable engine that could pull an adult or (me) on a field. This engine was, therefore, a stepping stone to be able to tackle the engine I wanted. After research, I bought a set of drawings for the Plastow 3” Bur...
Post a Comment
Read more

Stoke Prior Steam Rally 2025

 Stoke Prior steam rally 2025 📣 Show Report ✅ Strong Attendance – Rain or Shine! The show, as usual, was well attended, and we’re pleased to report that paying numbers held up strongly —despite a soggy Saturday. Fortunately, Sunday brought sunshine all day , which made up for it! A big thank you to everyone who braved the elements. This year’s weather was a definite improvement on last year’s continuous showers—and a far cry from the scorcher we had the year before that (we still remember those sunburns!). 😎 🚜 715 Exhibits on Display! We were welcome a whopping 715 individual exhibits this year, offering a fantastic variety for visitors to enjoy. This included: 25 Miniatures 7 Full-Size Engines 2 Steam Cars A huge number of commercial vehicles , classic cars , motorbikes , military vehicles , and stationary engine displays From the tiniest model to the largest working machine, there was something for everyone to marvel at.  <---This is us on the Su...
Post a Comment
Read more

Welland Show Report 2025

 Welland Steam Show 2025 Report..... (Saturday)    FULL  Video    https://youtu.be/ayib_Q_EvKc Welland Steam Show (Upton-upon-Severn July 25th - 27th  2025). Ross-0n-Wye Steam Engine Society 59th Annual Rally. Hotel : Star Inn also responsible for the "Minge Lane" Music festival. (We attended 1 month earlier). The show as usual was well attended. I'm happy to report the numbers looked fantastic and the weather was as good as needed. Maybe we have inspired the next generation of Model Engineers. It certainly looked like there was no shortage of money changing hands for tools.  The show boasted 42 miniatures and 105 full size engines, along with a huge number of commercials, cars, bikes, tanks and military vehicles and displays. This time again, like last year, there was the heavy haulage arena, which was fascinating to watch, as long as you could keep the coal ash out of your eyes :-) I can imagine the rising fuel costs to move large machines, but ...
Post a Comment
Read more