Auto centre punch

[Bob]

I've just been given one of these. I have no idea how it's supposed to work! It has a brass barrel with an unscrewable top and ditto point end, both ends contain springs. The point partially retracts into the barrel but doesn't lock Can someone please tell me how to use it? Thanks MrsB

[Jim Gregory]

The best-made auto centre-punches were produced by Eclipse and Moore&Wright. It may be a Taiwan cheapo. Has it definitely got an internal compression spring and a clicking centre-pointed "anvil"? There should be two knurled, threaded parts that you fine-rotate to set up to get it to operate percussively after down pressure. Try it out on a "copper" coin. Jim

[mindesign]

try pushing it down on a piece of metal - you should hear a click which indicates the indent has been made

[Palindr☻me]

How it is supposed to work is:

You carefully align the point where you want the mark.

Push down gradually against the spring. The point will move in and lift an equivalent of a little hammer inside. The hammer is pushed up compressing a spring. The more you push down, the harder it gets, as the spring is compressed.

However, there is a release mechanism inside, set to release the hammer when the spring pressure is great enough. Normally that tripping point can be set by rotating the knurled bit at the top, from practically nothing (tiny dent) to a heck of a lot (big dent - maybe even a hole). However, at that extreme you have to be really pushing down really really hard..

The hammer comes down and hits, well, basically the other end of the point, much as if you had hit it with a hammer. BANG.

When you lift the tool from the work, the springs reset everything back ready to do it again. The point never locks in the "pushed-in" position.

Now, if you have it set really high - you may not be pushing down hard enough to get it to trip. Indeed, with some, I am not physically strong enough to push down that hard.

The answer is to play with the knurled top and try it at one extreme and the other and places in between.

Typically, you try it with a scrap piece of the material you want to mark, adjusting it and trying it until the punch mark is the depth you want. It should then punch mark after mark, all to near enough the same depth.

Personally, I prefer a real hammer and a real centre punch..

[sponix]

Push down hard as some require quite a bit of force to operate

Unscrewing the top a bit will reduce the force needed to operate but will also reduce the dent it makes.

sponix

[Bob]

Thank you all for your assistance, with your help I've finally figured it out! It does take quite a bit of pressure to make it work but now I know the principle I can experiment til I get it right.

Thanks again

MrsB