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JS540 Hydraulic Cylinder Repair

Themanualguy

New member
Hey Gents

After searching for this information myself, and concluding I just needed to get stuck in and find out myself, I wanted to share my info I learn't today re-sealing the table cylinder on my JS540.

I could have ordered the genuine kit from Andmar Machinery UK, and doing a one day swap out, but I was a bit worried about international shipping at the moment because of spicy cough, and with some injection mold parts coming up in my schedule for grinding, I just wanted to hook in and see for myself what the seals were, and if I could source them locally. The answer is yes you can, and likely you can do it in one day if your local hydraulic/bearing supplier has the seals.

Removal of table:

Remove Magnetic Chuck

Wind Head up almost the entire way up

Remove the 4 screws holding the splash guard on, and lift off the splash guard.

On each end of the machine, you will see a plate, with a set of jam nuts in the centre, and 2 hex head bolts on either side. Remove the jam nuts that are on the end of the cylinder rod - the back nut is a long spigoted nut that locates inside the hole in the plate. Remove the 2 bolts on either side.

Before removing the table, I recommend you clean and wipe all dust and grit and oil as much as you can before you expose the ways.

The table is now ready to lift off, a bit of stiction will make it difficult to break the wringing effect of the ways, but I promise there is nothing else holding the table down than the 2 ends of the cylinder.

I was able to lift the table off myself and set down on a nearby bench, but I am 28 and don't recommend doing it alone for even blokes my age, but my cranes didn't reach the machine.

You will see 2 long blocks and they are connected by a centre tube. The long 3/8" hydraulic rods protrude from each end.

Remove the 8 bolts holding the blocks on, and pull the 2 x dowel pins out using a slide hammer (I was able to tap the dowel pin jacking holes out to M5 so I could use my small slide hammer, but you yanks and poms might have imperial slide hammer heads)

The blocks may need a bit of help to pry up off the ground mating surface. There is no O rings, there is no gasket. It is 2 ground surfaces that seal on each other - so you must avoid damaging either with pry bars etc.

The cylinder assembly will pull apart very easily, as the central tube is only held in by a close fitting spigot bore with an O ring. You can pull the long blocks off each end of the cylinder tube using no tools. Leaving you with 2 long blocks with honed bores, and a central cylinder tube with matching honed bore. The piston between the 2 x 3/8" hydraulic rods will have cast iron piston rings. Your call if they need replacement, mine were fine so I reused them ( I also needed the machine back in service and didn't have the time to make them - and besides I believe piston rings probably need to be bedded in I assume.)

Remove the 4 small screws on one end of each of the blocks using a small flat head screwdriver, and you will be able to remove a thin retaining plate with the rod sticking out the middle.

After the retainer plates are off, you will see a white teflon wiper seal, remove that and you will see a black oil seal. You may need a small screwdriver to pry this out. Be careful you don't damage the bore diameter of the bronze gland that houses the seal and teflon wiper.

The teflon wiper may be able to be re-used. If not, machine a new one with a neat sliding fit on the rods.

The oil seals can be replaced with a single lip oil seal - 3/8" bore, 7/8" OD, 1/4" width. Your machine could possibly have metric seals.

Lubricate the new seal and bump into place in the bronze gland bore, and follow up with the teflon wiper and retainer plate.

Your cylinder tube bore and block bores need to be cleaned, and I recommend you scrape off any gasket sealant on the mating faces of both the blocks and the saddle of the machine where the hydraulic oil is pumped up into the blocks. I honed by surfaces to get them in tip top shape for a good seal. You must clean all oil passages and faces before assembly.

Pre-assemble your cylinder loosely, and replace back onto the saddle of the machine - including the cylinder rod inside.

If you bolt the cylinder down and install the 2 dowels and 8 x bolts, you can actually turn the machine on and test your hydraulics, however you don't have reversing dogs to reverse the reversal valve without the table on, so set the traverse speed to slow, and hand actuate the reversal valve to test your cylinder back and forth.

You will also be able to see how much oil is being pumped to your slideways with out the table on in this way.

Clean clean clean!!!!

Oil Oil OIl!!!

The slideways.

Install table, and you will be able to hand operate it back and forth and see how smooth it is without the cylinder connected.

Put your mag chuck back on, using a thin film of neversieze and thin oil mixture between the chuck and grinder table (as per recommended by Cash Masters)

Now with your mag chuck on, use a dial indicator on the top surface to detect if your grinder is dropping or jumping up as it approaches the end of the table travel - it shouldnt move at all (disregarding a gradual movement due to a possible out of shape chuck surface - you are just looking for any speedbumps when traversing side to side.

Now this is the trick, install your screws and jam nuts on the end of the cylinder rod, but don't tighten up the rod jam nuts tightly, you want a tiny little bit of radial float.

What this will do is, remove any effect caused by bent cylinder rods (yes they bend very easily if people try to remove the table improperly) as it approaches the end of table travel. I had 0.05mm lift on one side caused by this issue when I had the cylinder rods tensioned. Having the nuts justtttt nipped up, but lock the jam nuts onto each other - I have no lift as my cylinder rod bend in one side cant influence the end of the table as it is drawn into the gland bore inside the blocks on each end of the cylinder. The end of the rod can float around inside the end plate.

Re-install your splash guard, and re-grind your chuck and enjoy not mopping oil up that drips off the cylinder rods anymore.:)
 








 
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