Centre punch

[edinthecloudsParticipant @edintheclouds]

[edinthecloudsParticipant @edintheclouds]

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

[frank brownParticipant @frankbrown22225]

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

[IanTParticipant @iant]

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

[JohnFParticipant @johnf59703]

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 !

[JasonBModerator @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. When happy use the centre punch to deepen the dot punch mark.

J

[Michael GilliganParticipant @michaelgilligan61133]

Posted by IanT on 03/12/2014 09:52:51:

Some will tell you that they can feel the point "drop in" if you have a light touch.

.

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

[FMESParticipant @fmes]

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

Problem solved.

[edinthecloudsParticipant @edintheclouds]

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

Cheers

Les

[Neil WyattModerator @neilwyatt]

Les,

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

Neil

[Chris TriceParticipant @christrice43267]

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

[mechman48Participant @mechman48]

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.

[Roderick JenkinsParticipant @roderickjenkins93242]

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

[Nigel BennettParticipant @nigelbennett69913]

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!)

[mechman48Participant @mechman48]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Roderick Jenkins on 03/12/2014 12:38:12:

I second (third?) the use of an automatic centre punch with a sharp point.

.

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

[Chris TriceParticipant @christrice43267]

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.

[Chris TriceParticipant @christrice43267]

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.

[Gary WoodingParticipant @garywooding25363]

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

[MM57Participant @mm57]

<<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?

[IanTParticipant @iant]

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

[Ian PParticipant @ianp]

Whilst were on the subject of centre punches, can anyone direct me to a source of a replacement tip for an Eclipse heavy duty automatic (Model 172)?

When I acquired mine the (screw-in) point had been sharpened many times and is now only about 8mm long (I imagine it should be about 30 or 40mm long originally) I suspect that only a few mm of the tip was hardened because when I sharpen it now it gets blunted after a few operations.

Ian P

[Neil WyattModerator @neilwyatt]

Hi Ian,

At about £16 all-in I doubt they do spares.

I had the same problem with my 'cheapie', so I annealed the tip then rehardened and tempered it, but its getting a bit temperamental – due for replacement, methinks.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 03/12/2014 22:02:40:

At about £16 all-in

.

… unless you buy from Farnell

.

I guess you were probably thinking of the 171, Neil

172 is a much more interesting device [see the PDF on the Farnell link]

MichaelG.

Edited By Michael Gilligan on 03/12/2014 22:33:19

[Ian PParticipant @ianp]

I did a search and found tips for the model 171 (about £7+) but I'm not sure they are identical. I'm sure in theory the tips are meant to be replaceable, but its possible the manufacturers did not go to the trouble of making them available.

The one I have is ball shaped at the top and seems much less common than the cylindrical versions.

Ian P

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