What is a dot punch?

[Peter G. ShawParticipant @peterg-shaw75338]

ega,

Thanks for the flooding thoughts. We live on a hillside about let's say 30-40 metres above Cockermouth & the Rivers Derwent & Cocker so we are definitely OK. I do expect though, that there are a few anxious people in both Cockermouth and Keswick.

Back to punches.

Similar to others, I have been known to draw dotted marks over to the required position by means of my middle punch and hammer. The big punch is only used to make a deep indentation ready for drilling. I must admit that I'd forgotten about dragging the lightest punch along a scribed line until it found the intersection. Maybe I should resurrect that idea.

I think the idea of using a small drill because of its flexibility does have merit. Something else to try. At the moment on my (cheap and nasty) vertical drill, I use a one end broken BS2 centre drill soldered into an extension piece about 6mm diameter so that I can get down to the indentation, then change drills without losing registration.

Regards,

Peter G. Shaw

[egaParticipant @ega]

Peter G. Shaw:

Two points which I hope are sufficiently on topic.

Small drills – the flexibility point is a good one but is only fully effective if the punched indentation ("pop&quot is as big as the chisel point of the drill. I expect you are aware of the so-called bullet drills which in effect have a reduced size pilot drill at the business end eg a 3mm drill with 2mm pilot.

The centre drill is much used for starting holes whether centre-popped or via coordinates. In the latter case it is the stiffness of the short centre drill which is helpful in holding position but as you point out this shortness raises the problem of losing registration. I like your extension solution which I am using on the lathe in a modifed form. Incidentally, I think it used to be possible to buy extra length centre drills; a toolmaker friend gave me a couple years ago but it occurs to me that they may have been made inhouse. Another alternative is the spotting drill which is slightly longer than the centre drill and has the advantage of matching the point angle of the following drill.

Stay dry!

[martyn nutlandParticipant @martynnutland79495]

We're a bit light on humour here in France at the moment.

So what was the b—-y joke?

Could we give sort of nonsense a miss?

Martyn

[KWILParticipant @kwil]

ega

You can indeed buy long centre drills, very useful when you want/need to be further away or which to work through an intermediate obstruction. I have a range of diameters available.

Edited By KWIL on 18/11/2015 15:53:40

[Peter G. ShawParticipant @peterg-shaw75338]

ega,

I don't think it's off-topic at all, because what is one of the main uses of a centre punch? To create an indentation suitable to start drilling, therefore a discussion of the various types of starting drill seems to me to be a proper follow-up to the original point of "What is a dot-punch?". Delving into the merits of the various types of drill bits which are used after the initial starting drill might well be going too far, but not what you are saying.

I don't know if I've read this somewhere or not, but it does seem to me that the depth of the indentation, and hence the diameter of it, should match the size of drill to follow. I have heard of spotting drills, and I think I've seen somewhere long series of centre drills, but never heard of bullet drills. But given my knowledge level, that's nothing to go by.

As I said, my vertical drill is a cheap and nasty version. I do have a mill/drill but given the quality of the z axis and its ability to drop by itself unless specific precautions are taken, I tend to do all my drilling on the vertical drill. Which is not easy given that centering the work under the drill is almost "poke and hope", ie it involves moving the vice around and attempting to line it up and hope it stays lined up as I tighten the fixing bolts. Plus the amount of sideways movement on the quill etc. Therefore if using the flexibility of a small drill allows me to get a hole started rather more accurately, then that's all to the good. I do have a couple of pieces of steel which have a tapered point on them and which duly allow me to line up the indentation with the drill axis, and I do tend to do this with the drilling machine turning. Ideally, I really ought to replace the drilling machine, but hey-ho, there's a cost involved, and if one day I get the mill/drill sorted then it could be money wasted.

Actually, writing the above and previous messages, has had one big advantage in that it is now making me think of other ways of getting accurate setting up. As usual, there will be nothing new, but adaptations of existing methods.

So a big thankyou to all who have made me think about it.

Peter G. Shaw

[JasonBModerator @jasonb]

For the last few years I have hardly ever used a ctr drill for starting a hole, I now almost exclusively use a spotting drill which is even more rigid than a short ctr drill and you don't have an end to break off. Mostly used straight into the metal when setting out holes with the DRO on the mill, drill hardly gets used for drilling.

Sized correctly they will also put a small chamfer around the hole, handy for tapping as you don't get a burr thrown up by the thread or have to go back and deburr.

[Clive HartlandParticipant @clivehartland94829]

I have in my possession an adjustable double pin punch, this is used for stepping out equally spaced punch marks when chain drilling. I will take a photo later and put it up for you to see.

Clive

[martyn nutlandParticipant @martynnutland79495]

I'm still waiting, here in Paris, to 'split my sides' on the dot punch joke, whatever it is.

Why doesn't Peter Shaw refer to General Engineering by R L Timmings (Longman 1995) and on page 158 he can discover exactly what a dot punch is.

Maybe he should 'try harder'; at least at being funny.

Martyn Nutland

[Neil WyattModerator @neilwyatt]

Posted by martyn nutland on 18/11/2015 18:40:10:

I'm still waiting, here in Paris, to 'split my sides' on the dot punch joke, whatever it is.

Martyn

I've sent you PM before I saw this second post; I thought you had been offended buy something I couldn't find.

Peters' original comment was moved here as it started a serious discussion that was out of place in the original thread. In being moved, the humour was lost.

This is always going to be a hazard now we have decided to be a bit stricter in keeping the forum organised.

Neil

[martyn nutlandParticipant @martynnutland79495]

Neil

Totally understand. Guess I'll never now get the joke! Not to worry.

Joking apart. Maybe I was being over sensitive and venting my spleen inappropriately. But you can imagine what it's like here. The atrocities were our side of 'town' and the drama and desperately sad outpourings continue hour by hour. Not many laughs!

I thought it might be nice if somewhere in the ME firmament – forum, magazine, whatever, we could have just a sentence expressing solidarity. We are, after all, a global community and this is the land that gave us all Isambard Kingdom Brunel, Eiffel, Bienvenue and dozens more, including – although I've forgotten his name – the man who invented the steam injector!

All the Best. God Bless.

Martyn

[V8EngParticipant @v8eng]

It has been truly harrowing to see the events in Paris on our TV, my sympathies go out to all in that great city.

Unfortunately I think that the world is becoming hardened and common humanities reduced by all the reports of:- bombings, shootings, knifings and attacks that seem to be beamed at us daily via the media.

All the best to you and yours.

Edited By V8Eng on 18/11/2015 20:58:52

Edited By V8Eng on 18/11/2015 21:00:16

[Ian WelfordParticipant @ianwelford58739]

Sympathies to all effected by these sad events.

[egaParticipant @ega]

KWIL:

"You can indeed buy long centre drills"

Mine don't have a maker's name – any idea where one can buy them?

[JasonBModerator @jasonb]

I get mine from MSC (J&L) do them upto 6" but have picked them up at ME shows

Page 138 of Virtual catalogue

[mark costello 1Participant @markcostello1]

We are All saddened by the recent events. The antidote is more shop time. Chips away.

[Ian S CParticipant @iansc]

Gifford, steam injector (I think).

Bourdon, Montgolfier, Carnot.

Thinking of all in Paris at this time, its almost beyond belief.

Ian S C

PS, I was on a tour of Europe in 1977, we arrived in Paris two days before Bastille day, riots were expected, the streets were lined with portable steel fences, and the Police carried machine guns.  No riots.

Edited By Ian S C on 20/11/2015 10:58:01

[egaParticipant @ega]

JasonB:

"I get mine from MSC"

Thanks for the link for long centre drills. I see that both 82 and 90deg varieties are available in addition to the normal 60 degs. Have you any view as to whether the M42 drills are worth the considerable premium over vanilla HSS?

[JasonBModerator @jasonb]

I've only used the HSS ones, for something that may only get used a few times a year I can't see much need to go to the M42.

[egaParticipant @ega]

Posted by JasonB on 20/11/2015 19:51:06:

I've only used the HSS ones, for something that may only get used a few times a year I can't see much need to go to the M42.

Yes, although I suppose that a long series centre drill that solves the old problem with a round column mill/drill of losing position would get used more often and that the M42, if more durable, would then be easier to justify. I find I wear centre drills out quite rapidly and the small points are relatively difficult to sharpen.

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