Centre punch

[Ian PParticipant @ianp]

Oops, I've now looked at Michael's Farnell link, where the PDF states spare points etc are available 'on request'

Maybe I should request one!

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

Perhaps one of our Australian members could advise.

… Spear & Jackson, Australia, lists them.

MichaelG.

[Roy MParticipant @roym]

Any body out there familiar with a "drill bush bar"? These work on a similar principle to the optical centre punch,(but are easily made). A suitable bar 6" x1" x1/2" has a 1/2" (12mm) hole reamed at one end. This is positioned over the scribed lines using the cylinder lens, but instead of punching and then picking up a centre punch mark with a drill, the bar is clamped in position and the hole drilled using a drill bush or home made bush. Large holes are made using a series of drills or reamers and bushes. By using two of these bars with close fitting pins, exact hole centres can be achieved with the use of inside mic or callipers. These bars are commercially available in the U.S.A. And are used in the aircraft industry for jig making etc., I could post a photo if there is any interest.

Roy  M

Edited By Roy M on 03/12/2014 23:22:14

[Neil WyattModerator @neilwyatt]

Michael,

Martin Lewis would despair at you!

eclipse-spear–jackson-large-automatic-centre-punch-e172

£15.99

Neil

[IanTParticipant @iant]

Yes please Roy – I'm familiar with drill bushes but haven't seen one with an eyepiece before. Should be easy to make except perhaps for the actual 'centreing' eyepiece itself – Perspex rod polished in some way?

IanT

[Michael GilliganParticipant @michaelgilligan61133]

1. Posted by Neil Wyatt on 04/12/2014 09:33:42:

Michael,

Martin Lewis would despair at you!

eclipse-spear–jackson-large-automatic-centre-punch-e172

£15.99

Neil

.

Neil,

Why would he ?

• I wasn't suggesting that anyone should buy from Farnell without looking elsewhere

Incidentally; although the box is clearly marked 172 … the punch illustrated is not the heavy "ball-headed"model that Ian was asking about. [perhaps it has suffered "product improvement" at the hands of the Bean-Counters]

MichaelG.

Edited By Michael Gilligan on 04/12/2014 10:24:01

[Anonymous]

I find that by lightly dragging a small centre punch over the marked out surface it is easy to determine when the punch drops into the scribed line(s). Personally I've never got on with automatic centre punches, but that may be because mine is an el cheapo one. It seems to bounce when operated and leaves the mark in the wrong place.

Having said that my use of centre punches is mainly limited to sheetmetal items, and non-precision work where I will be drilling the holes with a hand drill. For machined items, using the mill for drilling, centre punching is simply not needed.

Regards,

Andrew

[pgk pgkParticipant @pgkpgk17461]

I suppose if you really wanted to get silly with visual accuracy you could play with some of the rigid endoscopy I had in my past life. Smallest scope I had was 1.7mm (they do go a bit smaller) and the newer ones have the camera at the tip onto a large monitor. But then a DRO would work out cheaper

[VicParticipant @vic]

The standard price for the Eclipse E172 is indeed over £40. They paid £42 for one at work about 10-12 years ago.

I paid £8 for mine at one of the shows.

You can make your own points for them easily enough, I think the thread is around M4. I made around half a dozen different shaped ends for mine for punching wood for Ukibori. Don't ask, I haven't got round to trying it yet!

[VicParticipant @vic]

Forgot to mention, there was an article in one of the magazines about accurately drilling holes. After punching each location the writer scribed boxes around each one and used these to check accurate progress of each hole as he went up through drill sizes. Each box was a fraction larger than the required finished diameter. The scribed boxes showed if any holes wandered so they could be "brought back" to centre. I believe the writer called it "boxing" or something similar. Those of us with mills take accurate hole drilling for granted I guess but it's all to easy to get it wrong even with a decent pillar drill. Just a thought.

[Neil WyattModerator @neilwyatt]

Sorry Michael,

Your post made me think you were suggesting I'd got the wrong item because the price I quoted was a third of Farnell's.

As £16 is such a good price I'll add it to my Christmas list!

The picture is a dreaded 'for illustrative purposes only' but the larger punch does look identical to the farnell one.

Neil

[NobbyParticipant @nobby]

Hi Vic and Guys
Yes when marking out in 1960 ish we used to box in to see how the drilling was going it off center you could pull the hole over using a round file . Another method was to use a sticky pin running true to pick up the cross lines .
To use the jig borer we had to sign in to use it in case you drilled the table . No trouble these days using the CNC mill with the canned cycle's for drilling, pocket milling.and 3D etc.
Nobby

Edited By Nobby on 04/12/2014 13:37:22

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 04/12/2014 12:27:12:

Sorry Michael,

Your post made me think you were suggesting I'd got the wrong item because the price I quoted was a third of Farnell's.

As £16 is such a good price I'll add it to my Christmas list!

The picture is a dreaded 'for illustrative purposes only' but the larger punch does look identical to the farnell one.

Neil

.

No problem Neil … Perhaps I chose the wrong emoti-thing [it was meant to express surprise]

It looks like both of the current E172 offerings are the same ["improved"] version, so it's worth looking at the PDF on Farnell's page, to see the original style … and note that they used to sell number and letter punches for it [a set of those would be a real treat].

MichaelG.

[Author]

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