I was getting a little worried this month about finding a suitable subject to take as this month's article. Winter restoration projects among the Northern Hemishpere members of the ATIS stationary engine internet mailing list have been reaching completion, with wonderful stories of engines coming back to life after decades of silence, while those in the Southern Hemisphere have been bringing home their new projects ready to work on over the winter 'down under.' There didn't seem to be much I could pass on to the readers of GEM, until this little question appeared:
What type lubricant is the best to use for honing?
The first set of answers were brief, but with a little prompting, I was soon swamped with information, and back to the old problem of reducing the quantity to a manageable size! To deal first with advice on lubricants for honing:
I was taught to use a light oil like power steering or automatic transmission fluid. It's cheap and you've always got some on hand.
I just use the lightest oil I have sitting around. Usually 30 weight.
It all depends on the hone type. My old Sunnen says dry on the first two sets of stones and lard on the finishing or polishing set. I would imagine each hone manufacturer has its own preferences.
A rule of thumb I was always taught was, 'use what ever fluid normally runs in it.' i.e., brake cyl = brake fluid, engine cyl = engine oil.
On all the hundreds of cylinders I've honed over the years, I've always used plain kerosene and lots of it. When operating the hone I always had an open top tin half full of kerosene next to the job with an old paint brush in it. Before starting I'd brush some fluid around the top of the cylinder and start running the hone through, reapplying the brush whenever it started to look a little dry or squealed.
We got the best results just with ordinary WD40 or another make-it loses rust particles, it smears and helps the dirty fluid flow away quickly. While honing you can easily spray any amount you like. To inspect the results, just a blow with brake cleaner and the facing looks bright and shiny. Then you can decide whether to stop or start honing again.
I was always told that Kero was the way to look after the stone; kero would lubricate it but not clog the stone. Never use engine oil.
Yes, kerosene is what most machinists use to clean their sharpening stones. It will float the swarf out of the stone pores. It is also why people use it for honing as the stones are basically cleaning themselves during the honing process.
Also Kero here, and in its absence, Marvel Mystery Oil...
I am quite amused that no one has mentioned diesel fuel. It is cheap, flushes the grindings from the stones, and is easy to clean up afterwards.
Sunnen puts out its own cutting oil which appears to be about a 15w grade. It seems to leave a smoother hone pattern than Kero. I'd still use kero as a more cost effective alternative.
My dad was a small engine mechanic; I have both of his Sunnen hones. I don't know how old they are. We always used the roughing stones dry for quick stock removal. The finishing stones use a light oil. I have a five gallon bucket of Sunnen honing oil that looks like hydraulic fluid. This is kept in a squirt can and applied continuously while honing. When using dry stones it is important to have the cylinder clean and free of oil or grease. These roughing stones will remove stock very quickly and accurately, but if you use oil once, you must continue. I recently bored an Aermotor .060 over in about 30 minutes from start to finish. I trued a 2 HP Famous cylinder, removing .012' in about the same amount of time.
Clean out the bore thoroughly with detergent after honing. It must be clean and dry. If you leave any film of the honing oil, it will contain particles of abrasive and swarf, which will damage the rings.
After I have finished honing with kerosene, I wipe everything out and then run my hones over the cylinder dry to put on a very lightly scratched surface which helps in seating the rings. At least, this is my theory. Also, after honing, clean the cylinder with kerosene till white paper towels come out clean. This makes sure all the swarf that has been ground into the cylinder walls has been washed out. Some people will wash the walls with soap and water. What ever method used, it is imperative to wash out all the honing dust (swarf) from the pores of the cast iron. If not, the swarf will act like an abrasive and wear the walls/rings/piston.
With the use of brake cleaner, the facing and the pores of the cylinder wall becomes very clean and free of any grease. Then I use a 'Raagbol,' it's a tool that lookes like a dandelion seedhead, but instead of the seeds at the end there are little abrasive balls. I run this tool just a few times up and down (dry) and this puts on a lightly scratched surface with crossed diagonal lines which helps seating the piston rings. After cleaning again, I put some cylinder oil on the surface to prevent it from rusting until the moment of finishing the job.
A lot depends on the type of engine the cylinder is on. Meaning, is it an open crankshaft type or an enclosed one with a crankcase like an automotive engine. If it is of the open type, there is no oil control ring and seating is not as important. With a closed crankcase, you are concerned with ring leakage or blow-by. If the cylinder is out of round, start with a course set of stones and bring the cylinder dia. to within .0005' per inch dia. Then use a finer set of stones and bring the finish to polished surface. Crosshatching the finished bore with a dry stone does help seat the rings. If the bore is too smooth, the rings and cylinder wall will glaze over and the rings will never seat correctly. When using a hone of any type, never run the stones more than 1/3 of the length of the stone past the end of the cylinder. If too much of the stone is allowed to exit the cylinder ends, you will end up with an hourglass shaped cylinder.
I have, over the years, honed a lot of cylinders from ?' diameter to as large as 48', and have used everything from cleaning solvent mixed with a little oil to lard. I have found that lard, (Crisco) works about the best for all sizes of cylinders. With Crisco the grit and grime collects in it and can be wiped out as you progress, and you don't have the run-off that is a problem with oils. Clean up is easier. You still have to get everything super clean, as with any honing operation.
Once again, I hope some GEM readers will find this information useful -maybe next winter, when there are new projects on the 'to do' list!
Helen French firstname.lastname@example.org http://www.insulate.co.uk http://freespace.virgin.net/french.bros/