Centre punch

Hi,

When using a centre punch to produce light pop marks I sometimes have trouble hitting the centre cross of the scribed lines, I'm using a jewellers loupe.

Just wondered if anyone had any methods to produce a accurate centre mark every time?

Les

The standard method is to "drag" the point of the centre punch along one line. A slight nick will be felt as the point drags over the second line.

Frank

Some will tell you that they can feel the point "drop in" if you have a light touch. I wouldn't disagree but I've never managed to get consistent results using this method (but perhaps I'm just ham fisted). So for many years, I've used an optical centre punch for any 'fine' work and I get good results using it. It does need a reasonably wide area to rest on (or a similar piece to help 'balance' across) so it is not always usable in every circumstance. Generally however, it is my preferred way to get good results.

Other methods include co-ordinate drilling (using some form of compound table or the milling machine) or if you really need accuracy - especially useful when you need the relationship between your 'holes' to be exact - then toolmakers buttons can be very useful.

Hope this helps.

IanT

Edited By IanT on 03/12/2014 10:04:05

Spot on Frank but Les you may also want to consider an optical centre punch, just google it there are plenty, they work well as the eyesight dims with age !

You should be using a dot punch first which is more pointed, inspect the mark and if its off then lean the dot punch and hit it again to pull the mark to where you want it. When happy use the centre punch to deepen the dot punch mark.

J

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It's worth keeping a very fine-pointed [and nicely balanced] punch specifically for "locating" the position by feel ... Hand pressure, or a very light tap with a Watcmaker's or Toolmaker's Hammer, is enough to produce a pinprick spot; which can then be enlarged with a regular Centre Punch or a Spade Drill according to taste.

MichaelG.

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Edit: Jason beat me to it.

P.S. ... I find the spare points for Eclipse 220 Pocket Scriber very suitable as a fine punch. I bought a few at a good price, and keep three specifically for punching.

Edited By Michael Gilligan on 03/12/2014 10:25:55

Edited By Michael Gilligan on 03/12/2014 10:48:48

Like John F said, try one of these, **LINK** or perhaps a cheaper version from eBay.

Problem solved.

Many thanks to all of you for the advice, the optical centre punch looks interesting, its also down to practice and technique.

Cheers

Les

Les,

That's the problem that THIS FREE PLAN helps solve - get making!

Neil

Or consider a good quality automatic centre punch which doesn't involve hammers. I use mine all the time. Quick, simple and consistent.

Ditto automatic centre punch... have it set for the lightest impact setting then check with loupe, adjust accordingly & follow up with heaviest setting ... check again, then drill with #1 centre drill ...

George.

Tubal Cain recommends a little Archimedes drill with spear point bits for accurate centre marking. I've got a drill but no bits . I second (third?) the use of an automatic centre punch with a sharp point.

Cheers,

Rod

I use a scriber as a centre punch to very gently mark the point - using a 12x loupe to ensure I've hit the right spot - and then bop it with an automatic centre punch prior to drilling. Use a small drill to start and open it up.

Obviously the scriber isn't one of those bent-end ones - or Tungsten Carbide tipped! - but a Priory PR127

They're on Fleabay (usual disclaimer)

**LINK** (I forget where I got mine now, but for under a fiver it's not expensive!)

My centre punches...

Tend to use auto punch as stated or the slim pricking punch underneath it.. if on black steel then will revert to short stubby 1/4" underneath that... the large one hasn't seen a hammer in years.. but it's there if I need it. As for use I hold it at an angle & feel for the tip to 'drop' into the crossed lines, raise it vertical, then press 'till it clicks or a light tap with a 8 oz. hammer if it's the prick punch.

George.

Edited By mechman48 on 03/12/2014 13:02:12

Edited By mechman48 on 03/12/2014 13:03:41

.

I've never seen an automatic centre punch with what I would call a sufficiently sharp point.

MichaelG.

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P.S. ... Nice illustration of a spade drill [luxury Tungsten Carbide job] here.   [Similar geometry in Silver Steel should be adequate for marking-out]

Edited By Michael Gilligan on 03/12/2014 14:52:17

The joy of most auto centre punches is they come apart easily allowing you to put the tip in your lathe and sharpen the point with a diamond lap although my one still has the original (sharp) tip.

I also do what Nigel does which is use the sharp scriber I'm marking out with and push it hard into the metal to make the tiniest locating mark for the auto punch to key into.

I made an additional point out of silver steel, which I sharpened to a nice point.

<<From JasonB...You should be using a dot punch first which is more pointed, inspect the mark and if its off then lean the dot punch and hit it again to pull the mark to where you want it. >>

I seem to recall someone posting a link to a paper written decades ago that covered centre punching, including rectification of initial mistakes (to which, I think, the above is not recommended - something to do with what the drill does when it meets such a rectified punch mark) to an almost anal level of detail. It was actually quite interesting reading

But I can't find it - maybe a fellow forum elf can recall it?

My auto-centre punch very definitely seems to have a mind of its own - but perhaps I need to take a good look at it's point (and give it some TLC as Chris suggest).

IanT