Making core plugs for marking out.

**thehomeengineer** · Nov 12, 2022, 12:22 PM

Hi All
Following on from the cradle I made for the cylinder block for my 3” scale Foden steam wagon I need to plug the cylinder bores to aid the making out.
To plug these un-machined bores aluminium plugs were made.

An average size of each bore was measured and blanks turned and tapped in to the casting. Each end was slightly different due to the flank angle on the pattern which aids the removal of the bore pattern core.

The smaller bore diameter (high pressure bore) was simply machined from aluminium bar stock and parted off.

The plug for the larger bore (low pressure bore) was pressure turned from off cuts of 4mm plate blacks, cut out from another project. The blanks were machined at the average size diameter and a taper machined to help the plug engage in the bore. This same taper was also machined on the smaller plugs.

The photos show the core plugs being manufactured and installed.