Oiler pistons

[Jack Innes]

I am about to rebuild a mechanical oiler that has pitted pistons. The device has six pumps, each with a 5/16 diameter piston that passes through a fine cup packing arrangement & pumps oil by simple displacement. The pumps are submerged in the oil while working.

The pistons look to be mild steel that has been subjected to water at some time under the packing material. They still pump well but oil siphons by the packing when at rest. It took a while to figure that out. The crank case would fill up over night.

My question regards the best material to make the new pistons from. They are simply a 5/16" rod about 2" long, pressed into a brass holder & pinned with a tapered pin. There is minimal heat & no steam near the system & it will be pumping #30 regular motor oil.

Stainless steel comes to mind but is there a danger of it galling under the packing. I value your opinions.

Thank you,
Jack

[fredrosse]

I would suggest standard "drill rod", cost is about $5.00US for a 3 ft length at supply houses (Enco, McMasterCarr, etc.) This is hardenable (higher carbon content) steel, with a surface finish and precision diameter tolorance appropriate for this application. For this service no heat treatment is necessary, and in the unhardened state, ordinary tools can be used to cut/drill/mill this material. Simply cut the drill rod and drill as required, it will last in oil pump service forever, provided water is kept out and no corrosion.

[Lopez Mike]

Exactly. It's so accurate that you can use it to calibrate your common measuring tools.

I wouldn't bother pinning it though. Just Locktite it in.

[artemis]

The current issue of The Smokestack magazine has a nice article by John Winn entitled "Lubricator for the Hasbrouck Twin". In it John uses an internal piston metering pump (the pump is used in many chasis lubrication system, pumping a very precise amount of lubricant per stroke, and for this reason should be readily available). Interlube Systems http://www.interlubesystems.co.uk/ has a US branch at Interlube, 4696 Wadsworth Road, Dayton, Ohio 45414.