Elliot 8-18 Surface Grinder

[simonl]

I understand where you're coming from Pete.

In between replacing the timing belt on the SWWMBO Subaru I took the lid off the hydraulic tank.

Its similar to what I expected. 2 baffles creating a triple intercepter and the pump has some filter system on the inlet as can be seen





Last pic is the lid of the return system

While the tank has a fair amount of sludge and sediment, the fluid that I drained off was very clean. Well clean to the look anyway.

Simon

[simonl]

While I haven't had much time to do anything on the machine last couple of days, I have managed to eyeball parts of it in an attempt to understand some of it's workings prior to further disassembly. I was looking at the leadscrew and nut for the height adjust and it occurred to me that it surely must suffer backlash similar to any other system of similar nature. I understand that backlash is only a problem when you change directions which is not an issue with a SG since successive grinds will always be in the same direction, i.e. when the grinding wheel is lowered. My question for those who know is this:

How does the system keep the loading on the nut in the same direction? Does it rely on the shear weight of the head assembly to always be pushing down? Or are the gibb strips kept tight enough so that lowering the head works against that instead?

I can't work it out, It can't be resting from gravity on the nut because any potentially heavy grinding may have the tendency to lift the head by the backlash amount. It can't rely on the dovetails being tight because any potential loose spot and they would drop by the amount of backlash. While the backlash maybe small on a machine in good condition, given the tolerances that these machines are designed to grind to, even a small amount of backlash would render the machine useless.

Any ideas?

Cheers,

Simon

[Michael G]

I had thought about that and decided that gravity was the main assistant here - if the head does lift slightly it will still grind but there will come a point when it grinds no more - that is, there is no more material under the wheel to grind. Referred to as "sparking out" I believe.

Michael

[simonl]

Hi Michael, so for future reference I will need to make sure this assembly is loose enough to slide freely with gravity if I disassemble it and put it back. I also notice (as with yours) that the nut turns and not the leadscrew. This must be common practise with these machines.

Cheers,

Simon

[Michael G]

... for future reference I will need to make sure this assembly is loose enough to slide freely with gravity if I disassemble it and put it back.

I'm not sure the term "loose" should be used. It needs to be able to slide but at the same time you don't want it so it can appreciably move side to side or cross ways. It should be a similar fit to any other machine tool part - it must be able to move freely in the desired axis but only that axis.

Michael

[simonl]

Yes, I know what you mean. I used the term "loose" for want of a better term!

Simon

[Steamwhisperer]

Would there be any backlash eliminators on the screw?
I must have a look on the Jones and Shipman at work.

Phil

[simonl]

Hi Phil. Cant be sure yet. I wouldnt know what one looks like! Its caked in grease ATM so until I take it apart I dont know. Only part I can see is a thrust bearing. Come to think of it, the thrust bearing is on top not underneath as I would expect. Maybe it has two? Speculating ATM as im on school camp with my son in Portsea.

Cheers

Simon

[simonl]

Well I have had some time to myself today and so wasted no time doing more work on the SG. While I am slowly and systematically striping down the machine, cleaning, inspecting and replacing (if needed) worn of defective parts I had no real interest in dismantling the hydraulic valve group that sit under the table. The exploded parts diagram that I have in the owners manual is enough to scare me into not touching it. I did feel the need to at least inspect, clean and replace any seals in the piston and rams for the feeds since it seems pretty straight forward. Anyway, one thing led to another and on closer inspection I noticed a fair amount of crud in the output to the saddle piston. Of course the only way to totally remove all this crud was to dismantle one thing after another and next thing you know, yep you guessed it! It's all in pieces on the bench.

It's actually not quite as bad as I thought. The exploded diagram paints a more complex picture than is reality. I have since triple washed all the parts in turps and at least they are now all clean. I have ordered an imperial O ring kit from ebay and so await it's arrival before re-assembly along with a couple of oil seals and a couple of replacement piston rings which fell apart apon removal. It's interesting to note that the piston rings on the table traverse are some sort of polymer while on the cross feed they are hardened steel.

The machine must have sat unused for a while at some stage, there was rust and some heavy pitting on the bottom of the ram at both ends. Luckily it appears to be beyond the normal travel of the piston in operation and so will not affect operation. Both hydraulic return lines are heavily perished and so will need replacing. I plan to use just regular braided hose for this since it will not be high pressure.

After much thought, I have no plans to re-paint this machine. I have been slowly cleaning the exterior of the main body and the paint looks quite OK. It does have parts where the paint has worn off back to bare metal but when cleaned up it will just look like a well used (but well looked after) machine.

Cheers,

Simon

[simonl]

Well I have ripped down all the hydraulics, cleaned, flushed, replaced the seals and in the process of putting all the parts back together. I have also replaced about 1/2 dozen gaskets, as for the sake of a $15 sheet of gasket material it seemed the logical thing to do while I was there. A question without notice: I have always wondered, when using gasket material in an application such as mating two surfaces together (in a hydraulic system) do I need to use a jointing compound or is it deemed sufficient just to rely on the gasket material? My thoughts are that if the two surfaces are good, clean and the gasket material is of good quality, then that should be all that's needed. I'm asking because (1) it's something I have always wondered and (2) I can't afford to get this wrong as replacing some of these gaskets would require another complete tear down of the machine, table, saddle & hydraulics. So, I'm only planning on doing this once! Thoughts would be much appreciated, Thanks! Simon

[Michael G]

Just gasket material should be fine - it's been done like that for years. I generally just use liquid gasket materials myself but just as you have noted, they also rely on a clean dry flatish surface.

Michael

[simonl]

Just gasket material should be fine - it's been done like that for years. I generally just use liquid gasket materials myself but just as you have noted, they also rely on a clean dry flatish surface.

Michael

Thanks Michael.

[simonl]

Well, for anyone still following this thread, I have reassembled the hydraulic system and re-attached it to the saddle. I have also stripped down the hydraulic pump, motor and the reservoir and converted the motor from Star to Delta for testing.

I plan on bench testing the hydraulics on the saddle before putting it back together on the base. While it won't have the table attached and the rams will not be moving the saddle or table so may not produce the required back pressure for a true leak test, it will still give me an indication of any obvious problems before final assembly. Since every nut, bolt, seal, gasket etc. has been stripped down and re-assembled, I wait with both excitement and neverousness to test all the hydraulic functions.

I will post some pics.

Simon

[simonl]

[simonl]

Leadscrew nut

Is this a mirror image of a date, maybe date of cast or batch? 30/12/63?