I bought a cheap hand vacuum pump from china and the gauge did not read zero at rest.

The gauge is cheap and not designed to be serviced, it does not have an adjustment screw like other gauges have.

To repair it, I pulled the bezel out with force, then removed two screws behind the gauge that hold the outer metal cover around the gauge, it was still captured unless I removed the gauge from the pump but I didn't need to as it gave enough room to move it back and access the gauge internals.

There is a large curved copper piece inside, I bent it down little by little just enough to make the needle stay at zero when at rest.

The correct way to do it would be to take the needle off the shaft with a special tool or 2 flat bladed screwdrivers and then re install it in the correct position. By bending the bourdon tube you may have altered the calibration. However as it is a cheap Chinese gauge I doubt that it would read accurately anyway.

What are you using it for that needs an accurate vacuum reading?

Thanks for your advice, I didn't think to try to remove the needle.

I don't have an accurate use for it, I just wanted it to zero out properly when there is no vacuum.

By the way, do you know how the adjustment screw on other gauges work?

Edited 23 April23 Apr by flat-earther

You are best Googling for pressure gauge adjustment and calibration as there is more than one way to do it.

22 hours ago, flat-earther said:

Thanks for your advice, I didn't think to try to remove the needle.

I don't have an accurate use for it, I just wanted it to zero out properly when there is no vacuum.

By the way, do you know how the adjustment screw on other gauges work?

Ones I have seen appear to adjust the link between the bourdon tube and the needle gearing.