Author Topic: snapped centre drill  (Read 22615 times)

Offline Stilldrillin

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4972
  • Country: gb
  • Staveley, Derbyshire. England.
Re: snapped centre drill
« Reply #25 on: December 07, 2015, 06:25:51 AM »
I should add that unlike some I don't use mine for deburing or countersinking, I use a countersink for that!

The reason, they are at a 90* angle is to produce the chamfer. Before the hole is drilled.

The produced spot, is a larger diameter, than the finished hole.......

David.
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 673
  • Country: gb
Re: snapped centre drill
« Reply #26 on: December 07, 2015, 06:43:26 AM »
I only spot the hole, I don't drill to the full diameter with the spotting drill. For example I only have 6mm and 8mm spotting drills but still use these to "spot" or start holes of any diameter.

Offline kayzed1

  • Sr. Member
  • ****
  • Posts: 294
Re: snapped centre drill
« Reply #27 on: December 07, 2015, 03:31:23 PM »
Gents, this i will do in the future as today i found the box with it's 6 spotting drills. As has been said me being new and all that i put them in a draw as i had no idea what they were used for....I do now thanks...i will have a play tomorrow after i have fixed a sack truck for the pub up the road.. :beer:
Lyn. Ow! just had notice my 3phase kit will be here 10th to 12th in the am...so that will be the weekend job.

Offline sparky961

  • Hero Member
  • *****
  • Posts: 844
  • Country: ca
Re: snapped centre drill
« Reply #28 on: December 07, 2015, 05:31:40 PM »
Don't forget that if you do cut jobbers drills down to stub drill length, the diameter won't be accurate as drills taper slightly to create clearance. They will cut slightly under size.

I've known for what seems like forever to measure drill bit diameter near the cutting lips but never realized that there is an intentional and surprisingly large taper as you mention. By large, I'm talking only a  thou or two over the length from what I measured. Considering drills are generally only expected to rough your hole this is acceptable.

Thanks for providing that tidbit. I'm sure it will keep me from doing something silly at some future point.

Offline Will_D

  • Hero Member
  • *****
  • Posts: 668
  • Country: ie
    • National Homebrew Club of Ireland
Re: snapped centre drill
« Reply #29 on: December 07, 2015, 06:42:16 PM »
are generally only expected to rough out your hole
Ooohh Matron!
Engineer and Chemist to the NHC.ie
http://www.nationalhomebrewclub.ie/forum/

Offline ieezitin

  • Hero Member
  • *****
  • Posts: 662
Re: snapped centre drill
« Reply #30 on: December 08, 2015, 05:03:13 PM »
This is a great subject for people who are new to machining.

Sparky.... your a 100% correct about the tip on a center drill, I unintentionally made that statement to mean its a spotting drill in itself I see where it could be miss leading, I meant it to be the drill for the lead of a center drill.

I also use stub machine drills. I have a complete set number through fractional and letters, I only use them on critical work as i find them better than a spotting drill...... but over the years its just a habit for me to bore holes i really care about for accuracy, with the aid of a QCTP and always having a boring bar from 3/16 to 5/8 ready on center height i take that time to bore it.... drilling holes accurately to correct diameter is not easy and most new people think drills do the job and they do not.

If its that critical ill drill thread and use a button then bore.

Anthony.
If you cant fix it, get another hobby.

Offline Jonny

  • Hero Member
  • *****
  • Posts: 780
Re: snapped centre drill
« Reply #31 on: December 08, 2015, 06:12:13 PM »
Valid point Anthony I do exactly the same bore to size via 5 different tool choices.

I don't even centre drill, just plough straight in even for semi critical jobs you will see drill deflect so know its a no no and try other means! Mill I ultra rarely use centre or spotting drills, straight in with desired drill never ever a problem unless on a taper.

Gone off the subject rather than answer OP's requests.
How to get a busted centre drill out of a hole.

Offline tomfilery

  • Jr. Member
  • **
  • Posts: 7
  • Country: gb
Re: snapped centre drill
« Reply #32 on: December 12, 2015, 07:16:23 AM »
Guys,

Rather than using Alum to dissolve the drill, use citric acid.  Most of us in the steam engine world have a ready supply of citric acid for pickling components after silver soldering.

Just leave the component in overnight and by the morning you will find the centre dill has rusted badly and you'll probably be able to poke around and get it out.  If not, leave it longer and eventually the drill will disintigrate.

Regards Tom

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: snapped centre drill
« Reply #33 on: December 12, 2015, 07:57:37 AM »
Tom,

That greatly surprises me, as I am a regular and avid user of Citric Acid for removing rust, and I've never had steel dissolve in it even when left for a long time  :scratch:

It is excellent though at removing rust  :med:
Andrew Mawson
East Sussex

Offline kayzed1

  • Sr. Member
  • ****
  • Posts: 294
Re: snapped centre drill
« Reply #34 on: December 12, 2015, 02:47:29 PM »

    ***** just had notice my 3phase kit will be here 10th to 12th in the am...so that will be the weekend job****


Well, the kit did not arrive as stated in the sales bumf, so i have sent a message to the seller via ebay....but no
reply from them yesterday or today :hammer: i should have gone to collect it as i am only an hour away. :doh:
Lyn.

PS: thanks for the citric info, i will try and find some to test.

Offline tomfilery

  • Jr. Member
  • **
  • Posts: 7
  • Country: gb
Re: snapped centre drill
« Reply #35 on: December 14, 2015, 05:18:00 AM »
Andrew,

I don't know why it should be!   I'd guess you use a saturated solution for rust removal - as I do for drill removal.  I usually heat the acid liquid in the microwave for around 30 seconds - but, apart from speed of reaction, I can't suggest why the steel should get eaten away in one application and not in the other.  Might it be electrolytic - in that with two dissimilar metals in the acid (in my case brass and steel) the steel becomes sacrificial?

Regards Tom

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 673
  • Country: gb
Re: snapped centre drill
« Reply #36 on: December 14, 2015, 05:37:34 AM »
Citric acid will dissolve steel, it's just a matter of how strong the solution is to how quickly it does it.
I've tried using it for rust removal but never again as it leaves the surface looking a very dull grey.
I use washing soda and a battery charger as it doesn't attack the surface of the steel at all, it just loosens the rust.

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: snapped centre drill
« Reply #37 on: December 14, 2015, 06:59:29 AM »
Odd isn't it - I've used it for years and have never noticed any dissolving of the steel. In the case of brass I would be concerned that it might de-zincify it, as happens to under ground brass water fittings that eventually become porous.

When I rebuilt my 60 ton EPCO press, it had been in a bad fire then left in the open for several years, and the four 1.5" steel acme threaded platen raising screws were solidly rusted into their bronze nuts.

I was able to rise the platen with the fork lift leaving the huge bronze nuts low down, then put each in a bucket of citric acid that was saturated, initially hot, and regularly changed over ultimately about five weeks before they were all freed. Then I was able to remove each screw and further soak them for days on end in citric acid in a length of 110 mm soil pipe bunged at one end.

Despite having been in the citric acid for best part of two months those acme screws still fit nicely on the nuts and are now in use.
Andrew Mawson
East Sussex

Offline S. Heslop

  • Hero Member
  • *****
  • Posts: 1154
  • Country: gb
  • Newcastle Upon Tyne
Re: snapped centre drill
« Reply #38 on: December 20, 2015, 02:54:41 PM »
One place i've found alum and citric acid at is halal food stores. They of course usually have great selections of spices, and alum is usually included in that since it's got some food uses.

Offline porker

  • Jr. Member
  • **
  • Posts: 22
  • Country: england
Re: snapped centre drill
« Reply #39 on: December 20, 2015, 03:52:59 PM »
I'm learning stuff here so that is good. Why is it that I seldom see spotting drills for sale (at least in places I go in the UK)? I don't think Arc carry them for instance.

Offline Bluechip

  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 1513
  • Country: england
  • Derbyshire UK
Re: snapped centre drill
« Reply #40 on: December 21, 2015, 04:19:04 AM »
Try:

http://www.ebay.co.uk/itm/Gloster-Set-of-7-HSSCO8-spotting-drills-90-excellent-quality-CNC-spot-/370990999829

I have had one-offs from Gloster, not just a set. His phone# is lower down the page.

or 'cncpoorboy' another seller.

Dave

I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 673
  • Country: gb
Re: snapped centre drill
« Reply #41 on: December 21, 2015, 05:40:59 AM »
I'm learning stuff here so that is good. Why is it that I seldom see spotting drills for sale (at least in places I go in the UK)? I don't think Arc carry them for instance.

Good question. I don't know why Arc and many others don't sell them. I got mine from eBay.

Offline Manxmodder

  • Hero Member
  • *****
  • Posts: 739
  • Country: gb
Re: snapped centre drill
« Reply #42 on: December 21, 2015, 01:55:50 PM »
APT (Associated Production Tools) sell solid carbide spot drills for reasonable money.

Not associated with them in any way,but I have been satisfied with various tooling I've had from them.

http://www.shop-apt.co.uk/spot-drills-altin-coated-carbide-90-120-point.html
 ...OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline sparky961

  • Hero Member
  • *****
  • Posts: 844
  • Country: ca
Re: snapped centre drill
« Reply #43 on: December 21, 2015, 05:05:10 PM »
Not that I don't love carbide but consider that most hobby machines aren't rigid enough to use it effectively. Carbide is brittle compared to HSS and won't keep an edge for long if chattering away. That said, its not too good for HSS either but the price difference is huge!

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: snapped centre drill
« Reply #44 on: December 22, 2015, 04:00:23 AM »
Kayzed1 any update - did any of the dissolving methods work  :scratch:
Andrew Mawson
East Sussex

Offline kayzed1

  • Sr. Member
  • ****
  • Posts: 294
Re: snapped centre drill
« Reply #45 on: December 22, 2015, 03:32:09 PM »
Sorry, Yes the Alum did the trick in 3 days, i started off with it Hot and just had a look a poke about now and again. all drilled and taped and ready for me to draw up :doh: should have made a diag before i started..
it was so interesting following the direction of the thread i forgot to reply..
Lyn.

Ow! and the 3 phase gear arrived in has been installed and is working well, i will start a new thread on that.

Offline PJW

  • Jr. Member
  • **
  • Posts: 53
  • Country: gb
Re: snapped centre drill
« Reply #46 on: December 22, 2015, 05:46:15 PM »
I used alum to remove a broken tap from ally, I was amazed how quick it worked, it did turn the ally black in places but it polished off. I got the alum from fleebay. I keep my stash of alum in a safe place & hope I dont need it again!
Old Guys Rule the Dark Side of the Shed!

Offline kayzed1

  • Sr. Member
  • ****
  • Posts: 294
Re: snapped centre drill
« Reply #47 on: December 22, 2015, 08:18:17 PM »
My supply is back in it's cardboard tube at the rear of a shelf and BIG black letters says ALUM,,,just so it does not get binned.
Lyn.

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 8966
  • Country: gb
  • East Sussex, UK
Re: snapped centre drill
« Reply #48 on: December 23, 2015, 03:26:15 AM »
In my experience, if you have something in stock you probably won't need it, and if you don't have it in stock, not only will you need it, but it'll be hard to find where to get it  :lol:

So on that basis I've ordered a kilo of alum to sit on my chemicals shelf to make sure I don't break any taps or centre drills in brass or aluminium. :ddb:

... Mm .. Most of my work is in steel ....  :scratch:
Andrew Mawson
East Sussex