Scaling the Eureka

Hello,

I am interested is scaling the Eureka form relieving tool so I can use one inch bore blanks. I see that John Stevenson has done this previously by a description in a previous thread.

I am wondering if only the dimensions associated indexing sleeve need to be modified for the larger bore or do I need to change the eccentric amount?

All input is appreciated!

Thanks,

Dave

Hello Dave,

I tried to do much the same but it finished in tears I'm afraid. I found another way round it after that experience

You will need to boost the scale all round for a bigger relieving throw to about 0.075 inches from the design value of 0.030 inches.

The eccentric throw can remain the same if you are making a 12 tooth cutter. The areas that need beefing up are the indexing pawls and the sections of the pieces that rotate within each other. Bushing and brass bearing interfaces are essential to avoid 'pick up' and I recommend using gear oil for lubrication of at least EP 80 grade

I also recommend gripping the drive boss in a chuck rather that trying to turn between centres

Wishing you well and looking forward to reading an article on how it went for you

Regards Brian

Hello Brian,

Thank you for taking the time to respond to my question! I will make the suggested changes and create the drawings. Once finished the drawings I will post them back here to try and help other readers.

Take care,

Dave

Hello David,

I wrote up my story for EIM [ Engineering in Miniature] magazine, they were published in two parts last year with Part I the Eureka experience and Part II my alternative hand powered method.

My copies are out on loan at the moment so I can't tell you which issues to look out for but I will look out for your drawings with interest.

I should have welcomed you to the forum as well today, I hope you find all manner of answers here

Kind regards

Brian

The Eureka device obviously creates a lot of interest. I was astounded to see that my video of the device in action has had over 10,000 views

**LINK**

Rod

Dave

The issues of EIM that had Brian Wood's articles in were June and July 2019. I've sent you a PM.

John

Hi Rod,

I actually watched your video last night and the video is excellent, the video really helps to understand the function. I would still like to understand the math behind the how the eccentric travels were determined.

Dave

Hello David,

I don't think there is actually a lot of maths involved in establishing the eccentric motion needed to shape the flanks of cutters. In my two part article in EIM, the June copy [thank you John Purdy for providing the dates for them] in which I described my trials with Eureka, I used a full sized commercial cutter of 2.25 inches in diameter to measure the eccentric amount a button tool needs to carve metal off on a blank. This came to 0.070 inches, a lot more than the design value of 0.030 inches chosen for much smaller gear cutters..

Just as an observation. Rod's video shows the action well but in common with another one I have seen, they both demonstrate the easier task of frontal trimming; not the more demanding task of shaping. It would be intersting to observe the performance in that task

Brian.