Boring a circular groove

Though Chris said 'groove', I read his drawing as a dimple!

As this is a classic engineering problem with 2D drawings, may be worth mentioning the answer. It's to provide two or more views of the object, which together provide all the information needed to derive the 3D shape.

Basically, draw what the object looks like from three sides, like plan, front and side:

Actually this object only needs two views to show Chris said and meant 'groove'.

Far more to Technical Drawing and Draughtsmanship than this example, but the basic idea is simple enough.

Jason removed ambiguities by developing the object in 3D CAD, which I generally prefer because the 'real' shape can be viewed from any angle. But 2D drawings are also useful, and good ones are a positive joy to look at - art!

Dave

Deleted as inappropriate

Edited By roy entwistle on 29/12/2020 20:46:21

Edited By roy entwistle on 29/12/2020 20:47:45

Although the size in this case would not suit the method there is no reason you could not bore a circular groove

Drilling the 2.5mm hole could be difficult if the drawings are similar to the job. That is deep for the diameter. What is needed is a starter hole made with a stub drill and then change to a NEW split point drill of a quality make. Everything depends on the tolerances required.

2D and 3D drawings should complement each other.

You need dimensioned orthographic drawings for making the parts, and I regard them as the more important (and easier to draw, manually or in CAD). However, isometric drawings aid visualising awkward shapes, and their real strength is the field of assembly- and explanatory- drawings.

It's common now for a small isometric "picture" to be put in some spare blank area on an otherwise orthographic drawing. Hemingway do that with the drawings and constructional notes packed with their kits.

'

There is nothing new in that of course. Very highly-skilled users can produce impressive brochure-art from CAD packages like Alibre, TurboCAD and Fusion, but Victorian engineers and architects frequently produced beautiful, tinted drawings (perhaps for the contract negotiations rather than shop or site use). Vehicle service-manuals have long used isometric cut-away and exploded images; and we of bus-pass age may recall the magnificent cut-away engineering drawings forming the The Eagle comic's centre-spread features!.

Oddly, despite the possibilities for architectural CAD, public-relations "artists' impression" drawings released by property-speculators now are often a lot rougher and less informative than in the past.

Of those CAD packages, TurboCAD (or at least the edition I bought) allows a direct choice of 2D drawing or 3D "model". Its competitors assume 3D-modelling from the start, with some means to extract from the model the elevations needed in the workshop.

'

As for "art", just examine some of the huge general-arrangement drawings produced a century or more ago, of railway-locomotives, power-station plant, etc. A wealth of repeated small parts, hidden-detail lines, cross-section hatching, etc - all starting as pencil on paper, with a loose T-square and set-squares. The draughtsmen (not many draughtswomen, at least not at design level) were also expected to be good at free-hand sketching. Even structural analysis was often carried out on the drawing-board, using techniques like Bowes' Notation (which I recall , vaguely, from A-Level) to calculate stress-vectors in frameworks.

It's a bit OTT IMO to need a drawing of any kind to know what Chris wanted when he posted the above.

Emgee

Depends on what you mean by 'above'.

Chris supplied a drawing that was nearly as undecipherable as his question.

Ian P

Hi Guys, thanks for posts for clarity the half round groove goes right across the face in a straight line.

Regards

Chris

-----------------------------------------------

This was the posting referred to as above Ian.

Emgee

Seems like you might be able to slide the ballnose end mill up into the collet until only 5mm or so is sticking out so less likely to snap off under side loading. Or to avoid risk of the cutting edges damaging a soft collet, turn up a sleeve to fit over the cutter, slit it lengthways with a mini hacksaw and fit the cutter plus sleeve into a larger diameter collet, again with just the nose protruding.

Or grind a radius on the end of a piece of square HSS steel lathe tool bit and swing it in the mill like a fly cutter, held in a piece of round bar like a lathe boring bar.

Or Google for "Shank Type Convex Milling Cutter" (sorry, not allowed to post a link or even mention a site name as previous posts have been deleted for doing so.) and find a cheapo cutter that is like a woodruff keyway cutter but with the radius on the ends of the teeth to cut a half-round groove.

The possible methods became clearer once the end result had eventually been made clear.

The word "Boring" probably threw us off the scent, allied to the lack of clarity of what the desired end result was..

Chris,

Sorry to chastise you, but, please take this as advice for the future.:

If your definition of a problem is imprecise, the suggestions will, in all probability, not provide the solution that you seek.

You need to define the the end result clearly, before asking the question. This one was like like extracting teeth!

Howard