Automatic Centre Punches

Has anybody managed to bring back into use any of the cheap Auto Centre Punches currently on the market. I have had two units fail miserably after a short time in use

I used to have a superb M&W punch which failed after many years of use, how do the suppliers come up with replacement prices for the better tools, hence my purchase of the cheapy punches.

Yes I know you only get what you pay for, however the amount of material used in the manufacture of each useless punch hence my query to see if any of our brethren have come up with a repair solution.

Terry,

I'm sure you know this, but: The amount of material used is largely irrelevant ...

The important things are 'what material it is' and 'what the maker does with it'.

The common operating principle for these punches is clearly shown in Laurence Sweet's patent: **LINK**

https://patents.google.com/patent/US2384707

Build that properly, from good materials, and it will work, and will last

Build a rough approximation, from poor materials, and it will serve as a plumb-bob.

MichaelG.

The ones with a shank like a spring are said to work well and there is far less to go wrong with them.

Hi Terry

I have. Wish I had seen Michael G's info. Went all round the houses trying to get it to work.

To me shaft 17 canted over is the key. I put a ball bearing on the left hand side, the right hand side wants to be flat and so does 23.

As the spring is compressed the 2 cones come together and make shaft 17 drop down the hole, this is the hammer action.

On my punches the wear made it drop down the hole to soon.

HTH

Cheers Michael.

I’ve had one of the cheap ones from Halfords and it stopped working after a while. The two Moore & Wright ones I have still work fine. I like the threaded shaft meaning you can make your own points if required.

I've got an unbranded one with a knurled brass body that I bought from I don't know where, I don't know how long ago.

I do remember it was cheap - I think £2.99.

The punch point was too soft, so I made a new one from silver steel.

I use it regularly and it's worked fine ever since, with an occasional touch of the bench grinder to the point.

I'd assumed they were all like that - guess I'd better be careful if and when I come to replace it.

I'v got three old Eclipse automatic punches, one has worn out and died, the other two are ok.

Ian S C

Thanks for the patent link Michael.

I have a couple of Eclipse ones that occasionally go into a permanent mis-fire mode. Usually corrected by winding the force spring tension right down and bringing back to the normal operation point. Sometimes needs tow or three goes tho'. Clearly the part that should tilt over to allow the force to build up when the end is pushed sometimes sticks in the straight up position so the force spring never gets pushed.

Are there any traps for the unwary when dismantling? I assume its wise to follow my usual precaution when dealing with things known to have springs of working inside a transparent container .

The external spring devices are interesting but needing both hands to operate and having to hold the business end in place whilst pulling the other end to stretch the spring looks little inconvenient. I'd have thought there was considerable risk of lifting the push point away from its proper position when pulling he spring out. Nice thing about the common push type is that the point is naturally seated in the right place as you operate it. I'm sure it doesn't happen but one has visions of the external spring flapping around when relased with considerable pinch potential.

Clive.

Proverbial youtube link here might help.

https://youtu.be/0XtsvxzsWf0

Edited By Brian Sweeting on 23/09/2018 19:46:20

They're not brilliant and really they are only meant to make a shallow witness mark.

Edited By Michael-w on 23/09/2018 21:04:34

Tubal Cain has a you tube video **LINK** on the conventional automatic centre punch.

At around 11 minutes in he shows a cheap one with windows cut into it so the mechanism can be seen working. Several sequences of the device being slowly squeezed in a vice clearly showing how the actuator slips sideways when the operating spring is fully compressed.to free the internal hammer to strike the punch proper.

Clive

The automatic centre punch is I think intended for dot punching for split the dots marking out and machining, a rather heavier punch is required for drilling. Eclipse make two sizes of punch and if the dot punch is wound up to provide a full centre punch mark for drilling it is going wear quickly. The larger edition will make a centre punch mark but will be a bit clumsy for dotting duties. As usual it is use the right tool for the job. Maybe we are moving away from precision marking out as the availability of DRO for the home workshop relieves us of this old skill.

Mike

I had never considered it before, but I own a punchdown or Krone tool that I used at work to punch the wires into the back of network and telephone sockets. This has two, selectable, levels of brutality and takes multiple punch heads. I haven't worn one out yet over many years of use, even though I've had two (different departments). It wouldn't be at all a complicated job to make a prick punch and centre punch bit to go into the end of it.

Having said that, I do like to be able to position the prick punch carefully before tapping it with the hammer.

The modified networking tool could do the follow up job of belting the centre punch to widen the prick punch crater, though.

I inherited an Eclipse from my father, (MANY years ago, so it it has to be about 70 years old). It functions well, which is more that can be said of an unbranded cheaper version.. The latter does not function as well, or reliably.

As has been said many times, you get what you pay for.

Howard

I have an automatic centre punch of some quality but unknown maker I suspect Starrett which came from my grandfather so must be the best part of 100 years old (i'm 70). It still works if a little fractiously. However I bought a cheapy of Oriental origin I suspect which was/is only really useful as a marking out tool, the point is far too shallow an angle for drilling but gives a good centre for a proper centre punch.

It stopped working of course in double quick time and was sidelined for a while. By accident I discovered that slacking off the top cap a couple of turns allowed the tool to work pretty reliably from not working at all with the cap tightened to its shoulder hand tight as it was delivered.

regards

Ian