Honing Hydraulic Cylinders

Honing of hydraulic cylinders can be carried out in a number of ways.

A simple flex hone can be used if bores are in good condition.

If however there is scratching or scoring in the cylinder, material has to be removed from the bore, and the best way to do this is by using an expanding hone such as those manufactured by Sunnen Products Company Pty Ltd.

The simplest and cheapest hones that can be purchased for this job are the Sunnen hand feed portable hones.

By using a high torque drill with speeds to suit the diameters that you are honing, material can be removed from the cylinder and a surface finish suitable for hydraulic seals can be achieved.

Sunnen manufactures a range of hand feed portable hones beginning at 1.25" diameter.

This type of honing works well if stock removal is low. Honing this way can be tiring and hard work. If material to be removed from the bore is more than light cleanup work, then you should consider building yourself a honing rig or purchasing a Sunnen honing machine.

If you are intent on building your own machine there are a few things to consider.

Which Sunnen hone will best suit my work?

How much Sunnen honing oil do I need?

What spindle speeds do I need on the hone?

What stroking speeds do I require?

If you are building your own honing machine to remove material from cylinders quickly then you should consider the Sunnen Remote Feed Hones. These hones use a handwheel to feed out the stones against the bore while the machine is running. This eliminates the need to stop the machine and manually feed out the stones, thus speeding up the honing process. These hones will remove material at a rate of up to 12 cubic inches per hour in soft steel.

Your machine will need a good supply of Sunnen MB30 honing oil. A tank holding approximately 150 to 200 litres (depending on the size of your machine) should be sufficient. It is preferable to have some sort of filtering system for the oil. An oil pump supplying around 38 litres/minute will keep your cylinder cool when honing and help to
wash away metal from inside the cylinder.

Your machine can be made as simple as a push / pull manual rig, or you can automate it with power stroking.

Spindle speed is very important in honing. Too slow a speed will wear stones quickly, while too fast a speed will glaze stones, and hence they won't cut, producing heat and little stock removal. A simple calculation for finding the speed to use is to divide 800 by the bore diameter in inches.

eg. 800 divided by 4" diameter equals 200 RPM.

Watson Specialised Tooling sell a hand held digital tachometer, Part no. DT6234B, for checking spindle speed of your drive source. With 5 digit display, range from 2.5 to 99,999 RPM, and using 4 x AA batteries, this is a useful tool which will help improve honing performance.

If your business is honing lots of cylinders and removing large amounts of material, then you should be thinking about buying a Sunnen honing machine. There are several to choose from depending on what diameter and length of cylinders you hone and the amount of material you need to remove.

Sunnen machines use the proven MPS feed system and honing heads. This system can remove material at a rate of 21 cubic inches per hour. The MPS senses a drop in pressure of the stones in the bore and automatically feeds the stones out to maintain the set pressure.

HTB machines are available in lengths of 2, 3, 4, 5, 6, 8 and 10 metres. With a 3Kw spindle motor and 3,2Kw servo drive stroker motor, stroke speeds of 1 to 40 metres per minute adjustable through the operator interface are available.

For heavy duty honing, the HTC machines is recommended. These machines use a 7Kw servo drive spindle motor and a 4.2 Kw servo drive stroker motor. They will remove stock at 50 cubic inches per hour in soft steel. MPS tooling as well as HB tooling can be used on these machines. A comparison of the size difference between the MPS and HB hone heads can be seen here. The HTC machines are also available in lengths of 2, 3, 4, 5, 6, 8, and 10 metres.

The HTC-W series utilize an industrial PC control for all control functions (WINDOWS-System) for stroke position, motion control, stone feed, spindle speed and cutting pressure for optimum control of bore geometry.

A HTH machine is also available. This is a hybrid machine, which is essentially the HTC machine equipped with the electronics, electrical, and operator control panel of the HTB machine, ie. a non CNC version of the HTC.

So you can see that you have many choices of tooling and machines to suit your workshop when it comes to honing hydraulic cylinder honing.