J&S 540 Carriage Lock ????

[awemawson]

I'm sure that a lot of you have J&S 540 surface grinders or have used them when working. Do they have a carriage lock 

I was setting up today to grind a JT33 taper on some tooling, and as the cylindrical grinder is currently set up nuts on to grind parallel I didn't want to disturb it. So as the JT33 is only a short taper I thought that I'd use the 'Unigrind' sat on a sine table on the J&S 540.

The sine table gets tilted to the 'half angle' of the taper. The part is set in the Unigrind V block and adjusted for zero run-out. Then the assembly gets put under the wheel of the surface grinder with the table locked, so no X movement, and the part is rotated in the Unigrind forming the taper.

ALL VERY WELL IF YOU CAN FIND THE TABLE LOCK 

Then I went searching for my copy of the manual - yes you guessed - lent it to someone and it's never come back. Diligent search on the machine revealed a useful looking mystery tapped hole in the sliding carriage - looks to be 1/4" UNC. Tentative gentle screwing of suitable bolt ...... did nothing 

Surely there must have been provision for locking the table in the long movement  Blowed if I can find it if there is

[j1312v]

Hi Andrew,

For what I can see in the images your machine doesn't have the small bracket to attach a "stop block" (first picture).

I don't have the block, so I improvised a stop with a small vice (second picture)
 
To lock the table you have to set the dogs against the stop and voilą.

Hope that helps.

Best, J

[awemawson]

Thanks for that j1312v.

I must venture out to the workshop and see what there is in that area. Do you think that that bracket is  original, or something a previous owner has improvised ?

[j1312v]

I have seen lots of 540s and that bracket is mainly in the recent models(70's 80's), perhaps J&S have something else for the early models.

Best,

Joe

[awemawson]

Ah ... I think that mine is 1957 ... so quite modern really   

[awemawson]

OK had a look see - no bracket!

It seems that they've just extended the 'top plate' that the controls poke through to give a base for it. What is the 'round knob' that sits on / through that plate that sits over the Y travel trip - is it just a reset?

[awemawson]

Well thanks to Joe I've done a bit of cogitating and believe that it's feasible to fit a carriage lock using the 'trip dogs' by mounting a mounting block on the horizontal surface that surrounds the controls.

This surface is a piece of 1/8" steel plate covering the innards, and has the controls protruding though. I've removed it years ago when I titivated the grinder, but I cannot remember how much clearance, if any, there is under it for screw heads to hold the mounting block down. If needs must I can use counter sunk headed screws, but they are not very secure in thin plate.

When time permits I'll pull the plate off but mean while I've cut a mounting block and a stop block as 'proof of concept'. The idea is that the mounting block is screwed to the horizontal plate in a place where it doesn't interfere with the carriage movement. Then two horizontal cap screws will mount a temporary 'stop block' to the rear of it that can be pinched between the adjustable 'trip dogs' thus locking the carriage. In normal use the 'stop block' can be removed, but fitted when the carriage needs locking, as in my case of grinding the taper using a Unigrind fitting.

I'll hold off drilling and tapping the two blocks until that cover is off incase things need moving about a bit.

[j1312v]

Well thought Andrew

I only remember seen the table being lock a few times at my last workplace and mostly it was on a different surface grinder specially set-up to relief punches.

The 'round knob' is a stop bottom to the cross feed, another rarely used feature 

[awemawson]

OK a bit of spare time today so I was able to get on and finish the carriage lock 

First I removed the cover plate, which involved removing the operating levers. All very easy except for the little one that controls the cross feed force. It's retained with a taper pin, and due to it's limited rotation I couldn't get a punch on it's smaller end in a direct line. Ended up warming it up a bit with the torch and out it came.

This proved that there was masses of room for the block retaining bolt's heads. After a bit of cleaning up inside I put the cover and levers back temporarily to let me surface grind the blocks I'd made

[awemawson]

So then I drilled and tapped the mounting block and drilled corresponding holes in the cover plate, and put it all back together temporarily so that I could surface grind the bits.

The "feed speed lever" and "trip lever" are mounted on splines, and each has a peg pointing downwards into a brass cut out that limits their arc of travel, so putting them back and getting the phasing correct is a bit of a faff. The spline shafts will turn a full 360 degrees and presumably has hydraulic oil ports cross drilled to perform the needed functions.

Unfortunately the tin work that surrounds the table only just lets the levers come off their splined shaft, and even so they need tilting at the last moment to remove them. This means that you can't look down onto the (pretty fine) splines to select just where you want it to go (I'd marked the shaft with a pen) - so it was an iterative process, having to take them off and on a few times before I got it right 

[awemawson]

Then it was a case of dismantling it again, fixing the mounting block in place, fighting the levers once more, and proving that the automatic traverse and speed controls did what they should without fouling the mounting block.

Glad to say they were fine.

So - try it out - does it work 

Yipee - yes it does 

... so now I can get back to grinding that JT33 taper perhaps ... mm slight interruption:

Blossom the Sow has presented me with a litter of eight piglets - ten but two still born - mother and babies doing well - I suppose I'll have to go and buy her a bunch of flowers and a box of chocolates