A polite question - from a beginner :) Drilling a NONE wandering hole

Any time I have to drill a perfect hole, I look for a new quality drill first. I can't sharpen a drill to anything like the precision of the makers, and my efforts are bound to wobble and drill oversize.

If I wanted a perfectly ‘drilled’ hole, first thing I would consider is whether the part would fit the 4 jaw chuck.🙂 Not always appropriate, of course, but for one-off holes it can help...

Some have mentioned using light pressure to avoid wander - I'd just add this is especially important at the start, before the drill's full diameter is engaged and it's riding on its cylindrical land. If it's deflected to one side during that part of the cut, some degree of wander has become inevitable.

So give it time to be cutting as uniformly as possible all round during that period. once it's fully engaged, and especially when you've reached half-a-diameter or so depth, you can apply a bit more gentle pressure.

Edited By Mick B1 on 21/05/2020 17:08:31

Generally for drilled holes there should not be a perticular issue but if tight tolerance is required you could:-

Create a good centre as large as reasonable. Use a small drill to extend the pilot through the work.

Either drill to size with the final sized drill or do it in the smallest number of steps. Use a quality neat cutting fluid, fit the drill into the chuck to full depth, tighten all 3 positions of a jacobs chuck.

Failing all that you are into hardened drilling buttons accurately positioned.

regards Martin

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Hi at the risk of hijacking the thread, I would like to ask Jason to clarify what he thinks is a small drill that is too small for sharpening?

I have discovered in my workshop lots of small (less than 2mm) drills but despite using a micrometer on the shank (yes I know it's not accurate!.), I am not sure if they are a number, metric or imperial size!

I have always used centre drills or just drilled via a dot punch but I suppose these new fangled spotting drills are the answer to more accurate starting of the drilling process I have never used them....but of course the drill has to start in the right place whatever process you use to mark out where the hole has to go.

Regards to all.....this is a great forum!

Derek

Hi Guys,

A really good site for drill sharpening information is "Gadget builder"

https://www.gadgetbuilder.com/DrillSharp.html

He has a number of things on there for sharpening drills from mini to maxi. I built his four facet drill sharpening tool. It is my standard goto drill sharpener. There is a picture of mine on that page.

I don't sharpen much below 6mm and if I do it would only be used for rough work (metal), in the woodwork shop or out on site in a cordless. Certainly would not bother taking anything 3mm or less near a grinder unless I had nothing else.

I've built up a reasonable stock of the most used sizes from Dormer picking them up a shows or when suppliers have them on a decent amount of discount, they can also be used to bulk up an order so you get free delivery which effectively lessen the cost. I tend to use A002 Jobber length and A022 Stub.

I would like a set of spot drills but can't justify the cost yet. I am no expert, and probably most of what I do is voodoo, but what I do to start the hole is;

If free hand drilling use a center punch first, on the mill i dont bother.

Then I use a center drill, but all i do is make a dimple, I dont go any further than the conical end in the tip. So really I use the center drill as a very stiff small spot drill.

Then with the drill take it gently to start so the drill can find the dimple. At this point just before the drill cuts I look for any side ways deflection and re align the work if needed.

After that a gentle feed, as I was taught, "Don't push it, let the drill (saw) do the cutting"

And of course the deeper the hole the more frequent backing out to clear swarf.

Finally as others have said, good and sharp drills. I have two sets, general making holes and a more expensive set reserved for the mill and special holes.

Adrian

Thanks for that link John, I've not come across it before. Also thanks for another project to add to the to-do list. At work milling cutters, and drill bits, get thrown out so been able to sharpen them even just for roughing out means I now have a free source of drills and milling cutters

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Great reading from all! Many thanks for the suggestions....I have a 3mmspot drill on order, and will also follow other suggestions. And may even make the drill sharpener too.

Many thanks guys

Same here 1/8" and 3/16" do me which would be 3 & 5mm or if doing larger items then maybe 3 & 6mm, it is only if you want to use them as a combined CSK that you really need a larger range even then I can CSK most of the small fixings I use with what I have.

My way of assuring the hole is true is to pilot drill, then open the hole with an end mill, then drill it out to the correct size. The end mill is short and rigid so it barely deflects. Its square end will not tend to follow the pilot hole. I think of the end mill as a poor man's jig bore reamer.

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I always use a 3mm spotting drill before tapping M3 holes, the drill is taken so the full 3mm section just enters the work, saves having to clean any pulled thread off after tapping and also gives the screw a definite starting point.

Emgee

A very informative set of replies which I intend to make use of. Thanks guys!

Just one question: Why would you use a centre drill with a 142 deg angle? My own centre drills are 120 degree which is more-or-less the angle of the drill tip.

You're right Jason. I was thinking about something else.

Check with a dial indicator that the shank of your centre drill is running true within a couple of thou. Cheap chucks often let the drill bit wobble around and even a centre drill will wander, or drag the work across, if its running off centre.

Also check with dial indicator how much sideways movement there is on the end of the quill when it is extended to the normal drilling position, ie a few inches protruding. Movement there will also cause drills to wander, including centre drills.

Also cheap drill bits can bend and go all over the place.

Plus check with a dial indicator that your X and Y axes are properly locked and table is not moving under drilling load. Can be a problem on small lightweight machines. Sometimes the locking mechanisms need a bit of fine tuning.

Charles, this thread from a couple of weeks ago discussed peoples preferred spotting drill angle.