Drill or mill?

[Paul C]

Have a .75 aluminum round, .5 inch long and it needs a .5 inch hole thru.
Better to drill or mill?

 

[goldstar31]

Paul it all depends on 'what you have got' in the way of tooling. A mill or drill is only good enough if you can hold the part in question. With a resultant wall after 'making a hole' with whatever you have is quite liable to collapse in a normal vice/vise-- or come out----di dah, di dah!
You might want to hold the disc in a chuck as an arguably safer method. I would by choice hold it in a collet chuck.

Again, what are going to make the hole? A 1/2" twist drill has only two cutting lips and you might have everything ripped out whereas there is possibly a better thing like an end mill or if you have your act together you might consider drilling undersize and then reaming or possibly creating a 'D' and using it.

I have no doubt that I will not be the last to list a number of points and suggested solutions.

For what it is worth, I'd say think seriously in holding the thing in the best holding device which you have and drill then bore it in the lathe.


Sounds like the previous question which I attempted to answer

Norman

 

[stevehuckss396]

Lathe would be better. If you dont have one maybe someone near you could let you borrow one.

 

[goldstar31]

Lathe would be better. If you dont have one maybe someone near you could let you borrow one.

I can't get my old grizzled head around this. Reading through his posts to glean what information there might be, he has a mill with a rotary table now and now a drill- of what sort we are again, having to guess yet again.

Shame really?

Norman

 

[BaronJ]

Hi Guys,

If I were doing this small piece of material, I would put it in a collet chuck on the lathe, drill the hole in small steps up to the 1/2" inch. Though I'm sure using a bit of 3/4" inch diameter thick wall tube would be easier. In fact I've got some 3/4" inch 8 gauge wall thickness tube.

 

[Noel Gordon]

Lathe Just center the darn thing and then rip a 1/2 drill all the way ,NO need for any silly step drilling

 

[goldstar31]

Lathe Just center the darn thing and then rip a 1/2 drill all the way ,NO need for any silly step drilling

What evidence do you have to support your advice please?

I went through all his few bits of correspondence here before penning my reply.

 

[stevehuckss396]

I just re-read the post and noticed the piece is .5, or 1/2 inch long and not 5 inches long. I would still do it on a lathe but if that is not an option I would go with the mill and a V block. Easier to center the hole in the lathe.

 

[goldstar31]

I just re-read the post and noticed the piece is .5, or 1/2 inch long and not 5 inches long. I would still do it on a lathe but if that is not an option I would go with the mill and a V block. Easier to center the hole in the lathe.

Yes, yes! But has he a lathe? There is NO indication so far.

We simply don't know--------yet

 

[RM-MN]

If you hold the material and try to drill the drill will choose its own path and may exit the side of the material before it gets to the end of the material. Drilling on a lathe, the drill will try to self center in the material. By using a pilot hole, then increasing the drill size you minimize the distance the drill can wander from center. If you want an accurate size hole accurately centered, you drill undersize and bore the rest.

If you have no lathe, the self cutting end mill will be more rigid and accurate that a drill bit. In either case how you hold the material matters as when finished the part will have a very thin wall to hold against the method of clamping.

 

[Noel Gordon]

60 years as a tool maker one developes a huge knowledge for all aspects of machining all types of materials etc

 

[stevehuckss396]

Yes, yes! But has he a lathe? There is NO indication so far.

We simply don't know--------yet

Yeah I know, thats why i mentioned the V block in the mill over the drill press.

 

[Paul C]

After fooling with a Chinese boring bar set for half an hour and getting crappy results, I finished it with a 1/2 in drill in the lathe tail stock and the results were very good.
Did a second one by progressively drilling a larger hole after starting with a center drill and that went smoothly as well.

 

[John Antliff]

It's a good idea when placing a hole in a piece of stock, to start with a centre pop and then to use either a centre drill or a small stubby drill before reaching for the bigger sized cutting tools. The centre of the stock/hole always has the slowest surface cutting speed and is consequently the most resistant area being cut. Without relieving this area with a small drill any tool point will have a tendency to wander off centre. Actually, even a centre drill (which has a chisel rather than a point) will wander a little bit initially which is why a centre pop is preferred to start the whole process off. In a lathe you can actually see the centre drill initially wander before starting to cut despite having a correctly set up tail stock and snug fit barrel - it's the nature of the beast to resist! Generally the centre drill will get pretty close to centre, within a thou or two. If you want a truly concentric hole you must eventually bore it true irrespective with how you start the process - reaming will not correct an off centre hole. That's my theepence worth.

 

[Paul C]

Thanks for that. A very good process to keep in mind.
Pence in New Zealand? Not dollars like the Aussies?

 

[John Antliff]

Oh dear, you've spotted my original motherland!

 

[John Antliff]

I make miniature steam boiler injectors which require close concentricity for them to work correctly and I am often drilling holes in the sub millimetre sizes. I have learnt that to get a hole bang in the middle a piece of stock a special centre drill has to be used. It has to have a point not a chisel and I make them by grinding a conical shape on a piece of HSS rod (usually an old 6mm end mill shank) and then grinding it into a "D" shape. This gives both a point and a cutting edge ensuring that when the tiny drill enters the dimple it falls into the bottom of the conical hole caused by this special centre drill. Hope this helps.

 

[BaronJ]

Hi Guys,

Some time ago I built John Moran's four facet drill grinder,

http://www.gadgetbuilder.com/
There is a picture of mine on there, as well as pictures of others that have been built.

A not too difficult project, it just requires a little care and thought when building it.
Since then I've spent a number of very productive hours grinding and regrinding both new and old drills with four facet cutting edges. Drills sharpened this way will start a hole without a centre pop and also cut more easily than conventional conical point drills.

However John Antliff's recommendation will also work well for getting a hole exactly on position.

 

[goldstar31]

Great stuff, John!

Breaking news!! I have found that my old Quorn tool and cutter grinder is more or less still OK. A day or so absence from my intravenous injections of coffee and whisky, I should have it working again.
One wonders what some reactions would be when an almost complete set of Mark 1 Quorn castings arrived last week. I bought them in case the old mangle needed new parts and possibly would convert cheaply to the all singing all dancing Mark3.

So keep well

Norman

 

[BaronJ]

Hi Norman,

That is good to hear ! As far as the new castings are concerned, at least you will have spares if you need them.

I'm still playing with my modified "Brooks" grinder build ! I've not done much on it for a few weeks though. The 6X4 bandsaw has been occupying most of my time. Its been fully refurbished now and I'm busy making a hydraulic drop damper for the blade arm.

I've used parts from an old car shock absorber. Mainly the internal cylinder, piston and piston rod. I've just a few parts left to make before I can attach it to the bandsaw.

Keep well.