For some weeks (yes, really) I have been working on a design for an automatic boring and facing tool. I think that I've now come up with the finished drawings. What I would like is for some kind person to have a look at them and see if they can find any errors which I have missed and point them out to me. I have bought the metal for the project but want to be sure not to ruin it by cutting it up too small – come on, we've all done it! There are six drawings in DXF file format, a brief description in a PDF file and a jpeg of dubious quality reproduced below to give some idea to anyone who's interested.

I should point out that I am NOT a draughtsman, neither am I in any way qualified to present the drawings in any other than a way that I can follow and suits me. That is to say, They are produced for me and by me, as long as I can understand them and make it from them, that's fine. Basically, I'm not after a critique of my draughting ability. Sorry if this sounds a bit haughty, but there are some on here who tend to ride horses of high stature.

Here is the jpeg of the general assembly:

If you would care to help me, please send me a PM in the first instance.

Thank you,

John

I have taken up an offer to cast their eye over, so no need to read further, thank you. I look forward to cutting metal soon. Progress and results to be published in a new photo album in due course.

John

Blimey! I didn't expect it to get this much attention. So….

Murray – No, I don't have any 3D drawings. It's about as much as I can do to produce the 2D ones. But if you're offering . . .

Michael – I looked at the thread in my off-the-shelf Asian boring head and that was mighty small, probably in the region of 0.5mm pitch. That's why I've gone for 0.75mm, as I'm anticipating the generated forces to be higher on mine.

As I tried to explain in the post above, the feed screw is 0.75mm pitch – I happened to have one – and the feed wheel has 10 cut-outs, so one turn of the feed screw turns the slide screw 2/3rds of a turn – 0.50mm, thanks to the 12:12:18 gearing. Thus, one feed "click" advances the boring bar by 0.05mm. By having the drive pins arranged in two diametrically opposed pairs, differing PCDs and engaging with the feed wheels at the same differing PCDs, drive can be neutral, selected for an advance of 0.05mm or 0.1mm. There is, therefore, no need for the expense of a left-hand thread. There is provision for holding the feed ring by hand or using a screw-in bar to prevent rotation.

I'm on goodness only knows what version of the drawings – I've lost count – but I think I've found most of the errors and am about to freeze the design. Work has started on the slide and I expect to post some photos in an album in the next couple of days.

Other changes to Graham Meek's admirable design were prompted by the fact that I wanted a bigger one – who doesn't – and what I have available in the way of tooling and materials, etc. For example, I happen to have suitable MOD1 involute gear cutters obtained for a previous project, so I am using them instead of having to make and use a single-point form tool.

I must acknowledge the help I have received from John Stevenson and the encouragement he has given me in addition to a suggestion for further development. That'll be for another day. My brain hurts too much to start on that.

Regards to all,

John

A few people have expressed an interest in this project, so I've started an album entitled "Modifying a Graham Meek design". As work progresses, I'll add some photos and a brief description. I'll not clutter this thread when adding to the album, however. When (if) it's finished, I'll let you know. (If it doesn't work, I'll keep quiet and slink away and cry.)

John