HONING OF HOLES

I had a job in inserting a steel sleeve (bush, hole 25 mm) into a nozzle head of an injection molding machine. My worker used a hard steel bush and finally when I mounted the contraption on a cnc mill and bored it , even after many adjusting of the boring tools, regrinding the carbide tool, I found the bore tapering down at the bottom. Finally I reduced the rpm to 120 and did a very low feed and managed to get the bottom almost parallel.

Now I needed to hone it. I turned out a wooden short pole 100 mm long, 23 mm dia, used a hack saw and split one end (made a slit) in the center to a distance of 50mm.

inserted a strip of water proof abrasive paper strip, 3 inch long 50 mm wide into the slit and wrapped clockwise looking from the slitted end. The other end of the wooden pole was turned to a dia of 15 mm so that end could be held in a chuck of a drill.

kerosene was used as the lubricant and after some time starting the drill, moving it up and down many times,, I got a perfectly honed polished surface. YOU CAN USE A PVC rigid water pipe slitted at one end and do this too provided the chuck end is made of a tight fitting plug of nylon, alu , brass, or steel plug with a reduced dia at the stem to fit into a chuck.

For big bores , I have use several 90% bends of PVC piping and straight pieces, glued to gather just like a honing tool with four limbs, slit the limbs in middle and inserted water proof abrasive paper with rubber pad glued to the limb.

the rubber pads helped in applying honing pressure . I turned the contraption with a drill, reduced speed, using kerosene as lubricant.

I have honed 12 inch, 15 inch old Ruston Engine sleeves with this. Hope some on can pick up this to do some interesting work. With love from Sri Lanka.

You could try a car brake cylinder hone, available at auto part suppliers or internet. They are not expensive.

Paul

Thanks for the useful notes, Vasantha

MichaelG.

Good tips on honing, thanks. I bought a simple honing jig on Ebay (made by Sealey I think) to hone the cylinder on oir Stuart no. 1. As already said, very inexpensive.

I question the use of the term, honing, for the operation described. In a real hone the stone is forced against the work and held rigidly in that position until it is re adjusted. Anything spring loaded, like a brake cylinder hone or ball hone is merely a surface conditioning device and gives no control of diameter.

A real hone will establish a straight hole of uniform diameter.

True John, but the term cylinder hone as used in the automobile industry is common place.

The spring loaded type do not produce a hole to a specified, uniform diameter and requires a bit of user skill. I use a bore gauge in conjunction with the hone to check the hole diameter at multiple places to make it uniform. Good enough for our home workshops.

Paul.

As far as I recall, when a large engine is overhauled, after a rebore the next process is the vertical honing machine, which gets the bore dimension to the desired size and with the correct crosshatch pattern. The 3 legged spring hone maybe will be sufficient to get the crosshatch pattern on the cylinderwall again on a polished bore, but think it will be difficult to maintain a parallel bore and work up to a specified dimension. For sure it will be very time consuming.

When I was over hauling aero engines, if a cylinder was within spec we used to break the glaze on a 2000hr cylinder with a quick wipe round with some wet and dry, about 600 to 800 grit, those cylinders usually lasted another 1000hrs at least, then some times, if the head was OK the unit would be rebarrelled.

Ian S C