Miniature Boring Head

A miniature boring head, without the graduated dial (not made it yet).

I've been wanting to make a small boring head for my Sherline mill for years, but was unable to find or make dovetail cutters small enough for the job.

I stumbled on this design on the interweb and thought it might serve.

It's basically a 2/3 scale version of this design by Harold Hall with a few changes.

The body is made from 3/4" square bar which makes it a lot easier to hold for machining. No messing around with faceplates and clamps, you can do everything in a 4 jaw.

Here's the component parts -

The "barrel" and the gib are made from 1/2" round bar.

The lead screw is M4 x 0.5 and it accepts 4mm shank boring tools. I've got a few broken end mills (my boring tools of choice) in 4mm and 1/8" shank so with an 1/8" adaptor sleeve, I should be ok.

Pictures with the barrel extended -

Anyone got some tips on making a radial dial of this type? The dial will be 14mm diameter and hopefully have 50 divisions. I have a rotary table, just wondering about the cutter. Small centre drill at high speed?

Cheers

Steve

Edited By Steve Crow on 31/01/2023 18:59:00

Sweet! You can buy 1/8 dia shank carbide engraving cutters in 10s for not much on ebay.

This one is 19mm and was done with a sliding engraving tool and the numbers with 1mm stamps perhaps that's a possibility.

That's pretty!

Bloody horrible that, carefully pack it up and send it to me for disposal. 😅

Awesome work. I have absolutely no need for one but might be tempted to make one just because.

Do you have a link to the drawings you found of the small version?

I do all my dials the way Bernard Towers shows above. In the lathe with a HSS toolbit sharpened to a V and laid on its side. Indexing is by change gears with a detent made from a bit of hacksaw blade on engaging with the gear teeth. 50 divisions is easy with the 50T gear directly on the spindle or geared 1:1 with the spindle.

Edited By Hopper on 31/01/2023 23:17:38

A good idea, but I think I would mostly stick to reamers for what I need to machine.

Ah, thanks. I missed that. I like the idea of using square bar to make it easier to hold etc. Interesting project.

The "mini" version looks a neat job. I made a full-size version a while ago, mainly as an interesting exercise but I have found occasional uses for it as an alternative to my GHT model. I chose 1/4" Whit. for the feedscrew thread to give 0.050" per turn. Since 50 divisions is a rather tight fit on the small dial I went for 10, ie 0.005" per division and interpolate smaller increments which suffices for my needs.

I thought that the Harold Hall machining description was quite clever.

Very Nice, very neat ! 10/10. Noel.

Steve

I've also done my radial dials in a similar manner to both Bernard and Hopper. A lathe tool ground to a 40 deg included angle with a very small flat on the tip, on its side and moved across the dial with the cross or top slide depending if the face is flat or angled. Indexing done with change wheels and an indent. The smallest I've done is 1/2" dia/ 25 divisions, (no numbers as I had none small enough ) which was for a ball turning tool. Here's my indexing set up for a 50 division dial.

I wrap a string around the chuck connected to a weight  via a small pulley  fastened under the shelf above and behind the lathe to take up the backlash in the gears.

Edited By John Purdy on 01/02/2023 18:31:57

Nice work!

Use a sharp thread-cutting style lathe tool mounted sideways to scribe the lines. That's how I did this one.

I like the round gib idea.

Neil

Edited By Neil Wyatt on 01/02/2023 18:50:08

For those who dislike dovetail cutting.

Dr John Beddard made a Large Boring Head based on a round slider. I think the design and build was published in the SMEE Magazine. The details of this design are available from Hemingway Kits, (usual disclaimer).

Regards

Gray,

And, of course, the Dore (not Dore-Westbury) boring and facing head had a round-with-flat slide.

I managed to find a 90 degree engraving bit that I've not seen for a few years so I had a go at the dial.

I engraved the faced and drilled end of a 1/2" brass bar on the rotary table then parted it off 0.5mm thick.

The graduations are blacked with marker pen which won't be very durable but will do until I get some engravers wax (which I need for another project). The lines are 2mm,1.5mm and 1mm long.

I also need to centre punch an index mark on the main body.

A long way from perfect but it will suffice.

Edited By Steve Crow on 02/02/2023 17:05:57