Inheritance Machining Boring Head

[Maker Mike]

I'm sure some of you have seen the new Youtube video from Inheritance Machining. He makes a boring head with differential threads one with a 40 TPI of 40.816 and the other with a 40.816 TPI. This differential thread allows for very fine adjustment of the cutting diameter. He had to make a special lathe change gear for the 40.816 threads.

I was wondering, you people with electronic lead screws, would it be as easy as punching in a thread of 40.816 TPI and cutting it? The boring head adjustments have always seemed a bit course, to me, for what you may ask it to do. This differential thread design allows for a .001 diameter adjust per revolution of the fine adjust know.

 

[jorogi]

Don't know about ELS but my Narex has 0.0005 graduations with lots of room for interpolation beyond that. Saves me making a new head myself.

 

[gerritv]

Ignoring his hyperbole, yes an ELS you specify the pitch. My Rocketronics ELS Pro lets me choose an arbitrary metric pitch. 40 tpi is not that fine. I have an Infinity 857T boring head that does the same thing.

0.615mm and 0.635mm would be the matching threads.

 

[Maker Mike]

Thanks, it looks like I need a better boring head then. Mine has .001 graduations. I think I'm putting this boring head on my list of things to make. I like the design.

 

[whydontu]

Always love this stuff, even though my metrology skills are about on par with my Olympic hammer-toss skills. If you get a chance look up Maudslay Lord Chancellor micrometer, or Whitworth Millionth Measuring Machine.

 

[PeterT]

Another way to get around the somewhat coarse 0.001" diameteric tick marks & mental math is if you can position a dial gauge in & out as required on some repeatable datum reference. It kind of depends on the footprint of the part being machined but I just used my mag stand on a 123 block that lined up nicely to a repeatable edge. Its best if you can screw a wider foot accessory to the indicator plunger stem so the cutting tool sweeps accross the foot & record the (max) measurement. From there its easy as you increment or sneak up on target dimension. Finer adjustment BH's are available but they get spendy & sometimes more limited range. I also see more modern $$$ BH's with digital readout, kind of surprised thats not more of a thing in knockoff grade. The gauge is a no-lie instrument as long as its repeatable.

 

[Arbutus]

Always love this stuff, even though my metrology skills are about on par with my Olympic hammer-toss skills. If you get a chance look up Maudslay Lord Chancellor micrometer, or Whitworth Millionth Measuring Machine.

https://collection.sciencemuseumgro...2/maudslay-s-lord-chancellor-bench-micrometer might be my next project! Amazing history and story in there.

Whitworth ( one of the founding engineers in machine history) invented and improved many of the processes at the root of modern engineering practice. The Kensington Science Museum has many of his inventions on display. This is a Gemini view of his legacy...

Sir Joseph Whitworth (1803–1887) was a prominent Victorian English engineer, entrepreneur, and inventor. Known as the father of precision engineering, his innovations in measurement and manufacturing laid the ground rules for modern mass production and standardization.

Key Achievements​

1. Standardization of Screw Threads (1841)​

• British Standard Whitworth (BSW): Prior to Whitworth, every engineering shop made screws with unique thread pitches and sizes, making interchangeability impossible. Whitworth collected samples across Britain and proposed a uniform system with a standardized 55-degree thread angle and fixed pitch dimensions based on bolt diameter.
• Impact: Adopted nationwide (most notably by British railway companies), it became the world's first national standard for screw threads, vastly accelerating industrial production and machinery repair.

2. Modern Precision Engineering & Measurement​

• True Flat Surfaces: Whitworth devised a method using three surface plates and scraping techniques to generate exceptionally precise flat reference planes.
• Measuring Machine (1855): He invented a mechanical measuring machine capable of detecting differences as small as one-millionth of an inch (1/1,000,000 in), moving industrial manufacturing away from rough eye measurement to scientific accuracy.

3. Machine Tools & Advanced Manufacturing​

• He designed high-precision machine tools, including lathes, planers, and slotting machines, winning top international awards such as the Grand Prix at the 1867 Paris Exhibition.
• Fluid-Compressed Steel: To prevent defects and air bubbles in cast metal, he patented a process for solidifying molten steel under extreme mechanical pressure, producing stronger steel for gun barrels and industrial parts.

4. Armaments & Firearms Development​

• Whitworth Rifle (1857): He invented a rifle with a hexagonal bore and a fitting hexagonal bullet. Celebrated for its extreme accuracy at long range, it is widely considered one of the earliest sniper rifles and was used during the American Civil War.
• Breech-Loading Ordnance: He applied his hexagonal rifling and steel manufacturing methods to heavy field artillery and cannons.

Legacy and Impact​

• Foundation of Mass Production: Whitworth's insistence on standard measurements and interchangeable parts laid the blueprint for modern precision manufacturing and assembly lines globally.
• Whitworth Scholarships & Education: Created in 1868 and maintained by the Whitworth Society (founded in 1923), his scholarships have funded generations of engineering students in Britain.
• Philanthropy in Manchester: Upon his death, much of his fortune funded major civic institutions in Manchester, including the Whitworth Art Gallery, Christie Hospital, Whitworth Park, and the Whitworth Building at the University of Manchester.
• Enduring Standards: While metric systems later became the global standard, Whitworth thread specifications are still used today in specialized applications, including standard camera tripod mounts (1/4″ and 3/8″ Whitworth threads), microphone stands, and scaffolding systems.

 

[Mega arc 5040dd]

Making a boring head has been on my project list for a couple of years. I have seen quite a few videos of people making them and it looks doable. The only thing holding me back is the reverse engineering so to speak. I don't have a boring head to use as an example or pattern so I don't know what dimensions to make parts and features. One of the pars I have been unsure of is the screw. I don't know what thread pitch is best. I just know since it is a pretty small diameter it needs to be a size and pitch I can get a tap for. Now I have seen this video and things are starting to look complicated.

 

[Maker Mike]

This one is more complicated than a typical one since it has two screws. I was able to buy a 1/2" 40tpi tap and cut the outside threads on my lathe. I'm not sure how common 40tpi setting is on lathes though. Just going with the 40tpi screw should get you to the typical 50 divisions per revolution of the adjuster with .001 change in diameter of the hole, if I did the math correctly.

 

[Mega arc 5040dd]

This one is more complicated than a typical one since it has two screws. I was able to buy a 1/2" 40tpi tap and cut the outside threads on my lathe. I'm not sure how common 40tpi setting is on lathes though. Just going with the 40tpi screw should get you to the typical 50 divisions per revolution of the adjuster with .001 change in diameter of the hole, if I did the math correctly.

Would it be 50 divisions or 25? Are 1/2" 40 tpi taps common? I would have to check if my lathe can do 40tpi if not would a die be an option or would it be to sloppy? I am assuming that if I can get a tap then I should be able to get a die.

 

[Maker Mike]

So the thread would move .0005 but the diameter change would be .001. KBC Tools has the tap, but strangely enough the dies go from 1/2-36 to 1/2-48 with no 1/2-40. I'm sure you could find a die though.

 

[Mega arc 5040dd]

Thanks I will have to look into this more if or when I decide to bite the bullet and take on this project. Might have to start searching the net and see if I can find some plans for a boring head to take some of the guess work out of it since I have never even used a boring head before.

 

[gerritv]

40 tpi taps and dies are known as model engineering taps. UK hobby tool web sites will have them.