Boring a circular groove

Hi Guys,

I intend boring a half round groove of diameter 2.5mm into the bottom of a 15mm mild steel cube. Not sure what tool to use any suggestions welcome.

Regards

Chris

Happy Christmas

I think you will need to explain more clearly what you are trying to do.

Is this a circular groove in a face? (Say for an O-ring face seal)

'Bottom of cube' could be anything.

Ian P

You could make a D bit or use a 2.5mm ball ended milling cutter, in both cases just plunge straight in.

That would create a circular (semicircular in section) depression, its not a shape I would describe as a groove as one would expect a groove to have a length dimension.

Ian P

Well if it has length then the ball ended milling cutter would still be the tool of choice if it's straight across the cube and a D dit could be held stationary just like a form tool of it's an O ring groove. If a dimple in the middle of the cube then plunge in as per my first reply.

Hi Chris. Is it an annular groove that you want to machine? If it is for an 'O' ring, it doesn't need to be semi-circular in section but rectangular. An 'O' ring should deform towards the corners of the groove.

Alan

I wonder why I have that 'here we go again' feeling....

Many times previously, threads have developed a life of there own with many members suggesting solutions for problems the OP never even thought existed. Without knowing what Chris wants all we can go on is guesswork. I know I mentioned O-ring but TBH it was a bit tongue in cheek (O-rings are rarely or never fitted to semicircular grooves).

To me a groove is a groove. A stationary D-bit would work as a form tool but its an unlikely tool to use in the lathe or mill because most bit are relatively long so holding it would not be easy.

Ian P

Looks to me Chris has drawn a 2.5mm diameter dimple in the part, so as said a form tool or a 2.5mm Ball Nose slot drill could be plunged in 2.5mm for the desired shape.

Emgee

1.25mm plunge would be better

If the exact details of the groove were specified, (hole or groove + length ) the combined experience / skills on here could provide an answer very soon.

None of us know the length of a piece of string.

Howard

The OP has proven many times that he is expert in not explaining the problem to be solved very well, arguing with good practical advice, and not trying various things (or even googling) before wasting peoples' time.

Ditto the 1.25 plunge with a 1.25mm rad ball end cutter (2.5mm diameter).

Of course that is not a groove, just a dimple.

Edited By old mart on 28/12/2020 18:04:58

+1 for that Jeff.

Andrew.

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

Regards

Chris

Exactly, my error for stating 2.5mm.

But now we know the groove is right across the part then it seems a round nose form tool/slot drill is the tool needed.

Emgee

Chris

So if this is a half round groove running the whole width of the face, it odd that you asked about doing it by boring? Even odder that you had to ask at all .

From your previous posts and work that you have shown or discussed its obvious that you are fairly well skilled and knowledgeable, my initial thought was that this groove was somehow in a difficult area to access.

I would like to respectfully ask that in future you take a little time composing your questions.

Ian P

If the problem is clearly defined, the means of solving it will be more easily found..

For those fortunate enough to have been in Engineering all their lives, this becomes second nature, but for a newbie this has to be part of the learning curve.

Naming a process or part incorrectly can cause confusion and produce answers to a question that has not been asked. A picture or drawing often clarifies matters.

So it is beginning to sound like a groove 1.25 mm deep across the face with a 2.5 mm ball nose end mill.

Personally, I would be wary of doing it all in one cut, half the diameter of the end mill, even with a very fine feed.

(Unless you have LOTS of spare cutters to hand! )

Maybe gradually take out out some of the material with a 2mm end mill, for part of the depth, and then finish off with the ball end cutter.

Howard

Chris now we know what you need to do my suggested ball nosed milling cutter would do but if you don't want to buy one then you can actually do it but simply drilling a 2.5mm dia hole right through the cube and then using a standard milling cutter to form the rectangular recess shown on your sketch which will split the round hole in two.

Jason has given you an excellent choice. Should you decide to get a 2.5mm ball ended milling cutter to do the work, you will have to be very careful milling it. You will have to do the groove in careful stages to avoid breaking the cutter. With that size, I would recommend the following stages;

First cut 0.5mm deep.

Second cut 0.3mm deep.

Third cut 0.2mm deep.

Fourth cut 0.15mm deep

Fifth cut 0.1mm deep.

Run the mill at its maximum speed. Don't rush the feed rate. You can cut in either direction as you increase the depth.

Use oil if using HSS, or dry if solid carbide.

Edited By old mart on 29/12/2020 15:02:15

Like it Jason, clever. many thanks.

Chris