Help making Radius Turner

hi all

I'm having a go at building a radius turner from plans in ME #3896.

I'm not sure I understand the details of the Base Plate & Pivot Shaft.

The centre hole in the base plate is marked 1/2” * 26T, as is the pivot shaft which fits in this.

my question is....

does this mean both are threaded 1/2” * 26 tpi (presumably cycle thread)?

would it matter if I threaded UNF or BSF (I don't have a 26 tpi die).

thanks

Yes, it's Cycle Thread. The reason for using the finer thread is that it is less likely to come undone/work loose. Therefor a 1/2" x 20 UNF would be better than 1/2" x 16 BSF and should be fine for personal use. You still need an 11.5mm or a bit bigger drill for the UNF tapping size. Better still would be 1/2" x 32.

At a real push and with good confidence, you could machine to a fit (no thread at all) and superglue at least the lower parts together.

Just go for it but make your parts concentric. No hand threadcutting in space.

Dennis

Thanks Dennis,

i had a and a dig around and found a 1/2” BSB die which seems to work OK with a 1/2” Whitworth fine tap. I'm not sure what angle of BSB thread is but it feels like a good fit.

British Standard Brass is 55 degree flank angle so will work well with your tap. I made a radius attachment loosely based on a design by the late Steve Bedair. I think plans are still on the web, works well and gets a lot of use. I would not get to hung up about having the correct size thread to any plans. Common sense and use what you have is my approach, if concerned about things loosening use a dab of threadlock.

As a point of interest most people seem to use carbide inserts rather than HSS. Google “Ball Turner”. This is a popular easy to make type.

Ball Turner

Others make use of a boring head.

Thanks, I had a go at making a carbide inserts one as in the link, but wasn’t happy with how it turned out. I think I didn’t put enough thought in to adapting it for an ML7 and made the rotating disk too thick, so had to make tool holder lower which limited the size of balls I could make.

came across this one reading some old ME's so thought I’d give it a go. I'll probably make another when I've finished this one, may try to incorporate a bearing. I tend to find my first efforts never turn out quite as planned, but that’s half the fun.

I follow a YouTube channel, Ades Workshop, he made a nice looking and relatively easy to make ball turner. I've started making my own based off his design and I've just got a couple of things left to complete it. I may have to reposition the tool on its plate to get in closer to the chuck but that's a simple job, haven't put a lot of thought into it and will worry about that later. I've put some pics up in an album on my profile.

Good grief ! 8 parts average length well over 30 mins. It's the same type as in Vic's link made in real time.

I watched them as he released them, didn't realise it's over 8 videos and I watch nearly all YouTube videos at 1.5x playback speed which helps.

The one I made is half way down this thread.

**LINK**

Found some time today to do some more work on this.

finally realised that the photos in the article must include Mk1 & Mk2 versions. 2 of the photos don't agree with plans which had me stumped - plans are for a 2 piece tool holder, photos are 1 piece. I spent some time thinking measurements must be wrong as didn’t fit with scale of plans dimensions. I’m unsure if 1 or 2 piece tool holder is best, but will build a 2 piece and see how it works.

I like the idea of being able to set centre and radius using the gauge peg, it was a little hit & miss with my old one