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

[Former MemberParticipant @formermember32069]

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[derek hall 1Participant @derekhall1]

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

[John BaronParticipant @johnbaron31275]

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.

[JasonBModerator @jasonb]

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.

[AdrianRParticipant @adrianr18614]

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

[Jon CameronParticipant @joncameron26580]

Posted by John Baron on 21/05/2020 18:57:32:

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.

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

[Former MemberParticipant @formermember32069]

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[LainchyParticipant @lainchy]

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

[JasonBModerator @jasonb]

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.

[John ReeseParticipant @johnreese12848]

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.

[Former MemberParticipant @formermember32069]

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[EmgeeParticipant @emgee]

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

[CHARLES lipscombeParticipant @charleslipscombe16059]

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.

[Gary WoodingParticipant @garywooding25363]

Posted by JasonB on 21/05/2020 13:31:30:

Not sure about that Garry as first hole could wander and second drill follow, you may be getting mixed up with advice on getting a drill to cut to size, by doing it with two drills it does not matter if the second is asymmetric about it's point as the point is not being used.

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

[HopperParticipant @hopper]

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.

[JasonBModerator @jasonb]

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

[Former MemberParticipant @formermember32069]

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[blowlampParticipant @blowlamp]

I find using the spotting drill first is a great aid to getting a straight hole and in all honesty I haven't found its relative point angle to have much effect when using a follow up bit. It seems to me that the conical hole guides the next drill bit regardless of whether it's the centre or flank of the bit that contacts first.

One thing that I do find important is that of clearing the swarf frequently. If you don't do this then I think it's possible for the swarf to buid up and compact on one side of the drill tip, forcing it away from the desired line.

Martin.

[Neil WyattModerator @neilwyatt]

I don't think it's been mentioned, but the best way to keep drills accurate is to treat them with kindness

This includes a bit of cutting oil brushed on.

Neil

[blowlampParticipant @blowlamp]

Posted by Neil Wyatt on 22/05/2020 12:03:02:

I don't think it's been mentioned, but the best way to keep drills accurate is to treat them with kindness

This includes a bit of cutting oil brushed on.

Neil

Candle wax can be good too, if you don't want oil spreading over the part.

Martin.

[CHARLES lipscombeParticipant @charleslipscombe16059]

Thanks Jason, I had not followed the linked subject as far as I thought I had. In practice the point angle of a spotting deal does not seem to matter much except for hard materials. This is something of a relief for me as I became aware of spotting drills through the forum some time ago and thinking I was being smart, I ordered ones with a 120 degree angle (which seem to work very well).

Do you re-sharpen your spotting drills? Presumably this would need a good deal of accuracy, better than off-hand grinding ?

Chas

[Michael GilliganParticipant @michaelgilligan61133]

Posted by blowlamp on 22/05/2020 10:59:21:

.

I find using the spotting drill first is a great aid to getting a straight hole and in all honesty I haven't found its relative point angle to have much effect when using a follow up bit. It seems to me that the conical hole guides the next drill bit regardless of whether it's the centre or flank of the bit that contacts first.

.

The forthright advice that I referenced on on the other thread comes from a supplier of tungsten carbide drills … I think that source is probably very relevant.

[quote]

Some interesting notes and warnings about [carbide] ‘Spot Drills’ here:
**LINK**

https://www.destinytool.com/spot-drills.html

[/quote]

MichaelG.

.

Ref. https://www.model-engineer.co.uk/forums/postings.asp?th=157991&p=4

Edit: inserted the word ‘source’ for additional clarity

 

Edited By Michael Gilligan on 22/05/2020 14:00:18

[JasonBModerator @jasonb]

Not that conclusive on your link Michael, though I have not read it all.

"The spot drll point angle should be greater than or less than the final drill’s point angle."

Anyidea what they mean by:

Using  a spot drill with an angle less than the drill point angle WILL cause the drill flutes to be "blown off"

Edited By JasonB on 22/05/2020 13:45:03

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 22/05/2020 13:42:38:

[…]

Anyidea what they mean by:

Using a spot drill with an angle less than the drill point angle WILL cause the drill flutes to be "blown off"

Edited By JasonB on 22/05/2020 13:45:03

.

Yes … I believe that they mean if the cutting-edge of the large drill makes first-contact with the edge of the spotted hole, then the carbide will chip severely [and continue to do so if the feed continues]

Clearly this is in the context of what they supply, and its expected usage.

MichaelG.

Edited By Michael Gilligan on 22/05/2020 13:55:37

[Former MemberParticipant @formermember32069]

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