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Member postings for gerry madden

Here is a list of all the postings gerry madden has made in our forums. Click on a thread name to jump to the thread.

Thread: Mag chuck dismantling
21/11/2021 12:53:48

As Mark Bolan said 'all I want is easy action' and that's what I now have on my mag chuck. It was a bit of a struggle to get the beast apart. I had to clamp the base-plate to my bench and get a crow-bar on the top-plate to separate it, but once apart it was really just a clean-up operation. A wire brushing and a dunk or two on a bucket of white spirit was mainly all that was required.

There were a couple of points worth mentioning for anyone else attempting this often frowned-upon task. The first one is that I found the epoxy fillings between the poles were protruding quite significantly above the inside surface for the top plate. Suspecting that these could be part of the cause of the operational stiffness I cut them back with a blade until they were absolutely flush. The chuck couldn't have been made like this so my guess is that the epoxy has swelled a little over time from oil absorption. In the pic below the 'white bits' indicate where the epoxy was cut back. This pic by the way was taken in the almost-finished condition. There was much more protrusion beforehand.


The second point was that the aluminium frame came with only one oil lubrication hole in it. This didn't make any sense to me as its just as important to let the rubbish out as put new oil in. So I drilled and tapped 3 additional M10 grub-screw holes so that there were two on each side.. I can now add oil and drain simultaneously whilst operating the chuck.


I have to say that this was a job well worth doing and I'm astounded at the improvement its made. I can operate the on/off handle easily with one hand now where as previously I needed two arms and an extension tube. Of course some might say that this improvement is because I have lost all the magnetism. I suppose I might have lost some, I can't actually prove it either way, but I honestly can't tell that the chuck is any different to before. If I put a rough cast iron plate 3" x 5" on the chuck I simply cannot move it by hand and that's good enough for me.


Edited By gerry madden on 21/11/2021 12:56:34

Thread: Paint question
20/11/2021 13:47:04

Good morning each.

I might have made another mistake. I bought some paint from Paragon and requested a semi-gloss version of the J & S surface grinder blue. The choice for semi-gloss seemed like a good idea at the time.

Unfortunately I painted the first part today and as its drying its already starting to look far too matt for my liking.

Silly question really but no harm in asking... but is it possible to 'gloss it up' with T-cut or metal polish once its dry, or should I just fork out for another tin of gloss and use this one as an undercoat ?


Thread: J & S surface grinder - refurbishment
17/11/2021 00:13:26

Thanks all for your additional thoughts.

I really thought I had cracked all this thread identification business, especially as I now have the benefit of my OMT complete with its oculars for thread angles. But this one gave me real trouble. After a lot of humming and haa'ing and endless perusing of tables I decided it had to be a 5BA and bought at tap and a die. When I got them I put the tap in the hole and like every other tap I tried it was a wobbly fit. Well perhaps the hole was just on the top of its tolerance range, I thought....., I therefore turned up a screw using the new die opened out to its absolute maximum hoping this would sort it. Sadly it didn't as even this was also a rubbish fit.

Time for drastic action. Whether it liked it or not this hole was going to become a 4BA. Somewhat surprisingly the 4BA tap didn't create a mangled mess and in fact made a nice job. I made up a screw to Chris C's dimensions but with a 4Ba shank and it fitted beautifully.

I'm sure some people think I'm nuts but when finally something goes just as you want it to isn't it a nice feeling ?!


10/11/2021 03:30:42

Hi Chris,,pm sent. Yes it should be a simple job to do.

Re the thread, I did think I knew what it was, but that 'thought' somewhat fell apart when I checked more thoroughly. I expected it was a 1/8BSF but this is far too floppy. Currently the best fit screw from my tray of miscellaneous is an M3.5 which makes no sense at all ! All good fun!


08/11/2021 12:29:34

Chaps, my 540 should have a little locking thumb-screw on the dial for the height adjustment but it seems to have gone walk-about sometime in a previous life.

I could of course re-invent the wheel with my own design, but if anyone can send me a picture of the real thing please, or even just a length/dia/knurl-pattern/brass/steel description please if that's easier I would sleep easier at night (I'm ok on the thread size.) Thanks in advance.


Thread: Restoring the scale on engineering tools
06/11/2021 15:58:18

Thank you Robert for the pointer. I'll give this a try.


Thread: spindle bearings
02/11/2021 17:40:50

Lee, I have sent you a pm.


02/11/2021 12:06:28

Dont worry too much by the use of radial ball bearings. Essentially radial ball bearings and angular contact are same internally. When an axial load is put on radial ball bearings them they become angular contact. The size of the angle simply depends on the radial clearance within them. Typically for a 'C3' clearance bearing you will get 10 degrees or so of contact angle and this will increase depending on the load. When preloaded they run at about 15 degs contact angle. So provided these radial bearings are 'precision' made, they are just a lower cost arrangement than an angular contact set-up. But since radial bearings have fewer balls that ACs, they have a lower load capacity. This isnt a problem on a surface grinder though.


02/11/2021 11:44:46


I have just had a look in the parts manual for the 540 machines and the cross-sectional diagrams here show the spindle supported on two angular contact brgs, one at each end. The spring box arrangement is there to maintain a constant preload through the outer rings, regardless of thermal differentials.

You must have a bigger machine ?

Two bearings at one end is the sort of arrangement one might use if axial positioning of the shaft was critical. In theory since the use of a paired unit is there to provide preload, then only one of the bearings needs to have the shaft going through it in order to get the required radial support. This arrangement 'might' also save one having to worry about some aspects of matching the two bearings, but I have to say I have never seen such an arrangement in my life so I am intrigued. Inner rings should normally be clamped to the shaft by a nut. I cant see how this would be compatible with your arrangement though.

Can you make some kind of sketch ?


Thread: Mag chuck dismantling
23/10/2021 19:31:22

Brian, its probably the latter. My wife tells me that all the time I'm pretty sure its not just the shaft that's seizing up. There something pretty foul-smelling inside this contraption which I found when removing the screws. Baz describes it as 'crud'. I'm not sure that's quite how I would describe mine! I think a large animal has got inside and died.

Dave - thanks for the links. Very useful info. I must remember to do a bit more searching on here before posting As regards losing magnetism there seems to be some debate about that on the internet. But if I do, I'll just have to find out for myself how limiting that is for my tasks. I might be able to live with it. If not then I'll buy a new chuck.

Baz - thanks for your experience. I'll give that a go on the handle. After that I'm not sure mine is going to come apart as easily as yours did. But let me play a bit more and see what happens.


Edited By gerry madden on 23/10/2021 19:32:57

23/10/2021 16:54:20

Afternoon chaps, just trying to dismantle my mag chuck as the handle is much stiffer than I think it ought to be.

Does any one know how the handle is retained on the shaft ? It's not a roll pin or a screw, at least that I can make out, in fact it looks more like a rivet. What I do know is that both ends are a bit of a mess suggesting I'm not the first to try to remove it. It presently looks like this:-



Also, in terms of the separation of the two halves of the chuck itself I'm struggling here too. I have removed 11 long countersunk screws from the base and I can see that there are four locating dowels which must be keeping the two main sections together as seen below.


However, quite a lot of hammering on the overhanging ends of the top plate wont budge it off these dowels. I'm thinking of using a press to force a wedge between the upper an lower plates but thought I better check with the experts on here before getting too aggressive in case I've missed something


Thread: What to drive a J & S with ?
20/09/2021 21:23:28

Gentlemen, thanks again for your advice which i can assure you was all carefully considered, perhaps too carefully but there you go

This morning I had a very interesting discussion with someone who I was certain would try to sell me something and had he done so I might well have bought it. But after assessing the machine and its motors he actually said he could not recommend his products and that fiddling with the motors was not a sensible option either. In fact he directed me to a company I had previously spoken to. I'm still taken aback by his candidness. Its not often you get this these days.

So rotary converter it is. As Buffer so succinctly put it "The only downside was the cost but now I'm set up for life"


19/09/2021 12:46:20

Right chaps, I've had some time to consider all the good points made and really appreciate your guidance. I'm probably 80% convinced that a 'non-mechanical' device is the type I should go for.

My 20% of doubt centre around the fact that :-

1) I don't want any compromise in machining quality (This was the very reason to get a J&S instead of f a Warco)

2) I don't want any loss of torque

3) want essentially plug and play, no motor modifications, splitting circuitry etc. I have enough to do without adding the the 'to do' list

Im sure if I keep researching I will eventually find what I need but its a jungle out there, at least for the electrically uninitiated. In the meantime I have a few questions that I hope someone can answer for me:-

A) Power rating - My motors name plates give mech output power (kW) and input power (from VxA). Should the drive be sized on the input or output ?

B) Cost aside, is it best to match the drive power closely to that of the motors or significantly exceed it ?

C) There are a very limited number of drives that say "1ph240V input and 3ph400V output". What is the reason for this? If I were to get a 240 > 240 converter, this WOULD be a torque compomise wouldn't it ? Or am I missing something ?

D) Some say one should switch the largest motor on first (the wheel head) followed by the smaller. In my case the name-plate rating of the two motors are 1.5kW and 0.55kW respectively. What I'm thinking here is that the wheel isn't under any load until its cutting metal so its current consumption might actually be lower than that of the pump motor that will be operating under full load immediately. So does it really matter which goes on first ?


Thread: Type 2 precision vice from Arc euro
13/09/2021 18:06:22

I bought one of these at the price in the flyer. The toggle thing is a little wobbly but I'm shocked at its precision. I've been running over it with a micron DI and a surface plate and every feature seems to be less the 5um. Many are less than 2um and that seems to include the 'chatter'. Really good. Thanks for the heads up.



Thread: I dont think its 3phase but what is it ?!
11/09/2021 22:04:19

Thanks again all respondents for your comments and good advice. This is such a useful group of experienced people always ready to help !

I 'think' I might have solved the mystery. This birds nest of a junction box is likely be a feed to the garage plus a feed to an electric gate system on the far side of a plot adjacent to my house. The latter have never been used since we moved in 8 years ago and for that reason I had completely forgotten about them! They weren't used partly because I have no need for such impediments in my life and partly because they didn't seem to function well when the builder tried to demonstrate them to us. I think we see why now The data cable/ telephone wires probably go to a control box which is on the wall inside the house. Not only have I not used this, I haven't even seen it for years due to the growth of a large plant in front of it !

One wrinkle in my theory is that when I trip the RCD for the 'outbuilding' on the consumer unit, the garage electrics are non-functional but the gates control box inside the house and the camera on the gates 100 yards away are both still functional !!! Clearly further investigations are needed to establish the the ins and outs of the junction box outside and to find a way to isolate the gate part of it.

John H, my iboost has been excellent with no trouble since it was installed just under 7 years ago. I actually had the control box installed next to my consumer unit in my in-house workshop so that I could easily keep an eye on proceedings. So far its dumped about 17MWh into the hot tank since installed. I was actually expecting to have got through a few heating elements by now but this has survived too. I suppose that shouldn't be a surprise as most of the time its operating at low power levels.

Thanks again all for your thought provoking stuff.


11/09/2021 01:29:30

Gents, connected with my thoughts and questions as to how to power my J & S 540, it suddenly occurred to me this evening that since my house was originally an industrial building, it may already have a 3 phase supply. A quick check of the meter cupboard suggested not.


But then I saw a separate galvanised box on the wall with 3 big cables going into it. Could these be the other phases, just terminated I wondered .....


I took the cover off and found this,,,,



The first thing to occur to me was that the cover has no seal - hardly suitable for an outside junction box. But what were all the wires ? I didnt want to pull them all out as it looked pretty fragile. What I could see though was that the cable entering on the righhand side is comprised of thick cored red-sheathed wide and a thick black sheathed wire only. These go into the two screwed connectors wrapped up in blue and brown tape. After that I could not make out where they go but they 'may' go off to the left hand cable. This 'might' be a connection to my garage consumer unit but without untangling the mess I cant be sure.

Filling the rest of the space in the box is what looks like telephone wiring which appears to come from the central black cable, Some of this 'telephone wiring appears to disappear into the wall behind. The strange thing is there is already a telephone junction box just to the left of this one. I mystified.

To me this looks wrong on a number of many levels - unsealed, mixed wire sizes, crammed in like sardines... even the cover lip has been bent to help it accommodate the thick cable sheathing on the right side.

I think I need to get this investigated and tidied up. Your thoughts ?


Thread: What to drive a J & S with ?
09/09/2021 18:44:28

I nearly pressed the button on a Warco surface grinder recently but at the last minute a J&S540 came up for sale very close to me. It ran well and the main spindle was perfect so I paid up and took delivery.

In time this might become a restoration project but right now and for the foreseeable I'm just going to play with it and make some dust at minimum. The first thing I need to do is get myself some 3phase. I called a company today that specialises in drives and, based on the fact that the machine has two motors, recommended a 3HP/2.2kW rotary converter.

I'm most definitely not an expert on 3ph electrics and have only recently read up on drives. However I'd managed to convince myself that a RC wouldn't be necessary.

The machine has two motors, one for the spindle (plated 2HP/1.5kW) and another for the lube system for which there is no plate. The manual suggests 0.5HP though).

So chaps, what do you think ? Is the RC the right solution or is there a more popular and cheaper one, albeit perhaps with some technical compromises or limitations? Your thoughts would be appreciated.


Thread: Lathe Move
08/09/2021 20:29:31

You could try:

He is based in Tring but travels. I used him recently and he knows his machines and how to handle them.


Thread: optical mystery parts
04/09/2021 16:33:42

John, you are right ! Your first comment got the cogs turning as I remembered from geology evening classes I did many years ago about the double refraction properties of calcite.

On the same course we went on to slice up rocks into thin wafers and look at them through a polarising microscope. As soon as I saw your reference to Nicol Prisms it all came flooding back.

And picking up on Bazyles point, whilst watching the news last night I found could peer through the prism and rotate it. At a certain point the telly screen went black as if had switched it off, but everything else in the room was normal. I then found that I could hold a clear plastic disc at arms length to restore visibility of small sections of the telly's screen to its normal appearance, albeit with some fringes due to the stress in the plastic.

All fascinating stuff indeed. But the question remains, is there any use for a Nicol Prism in the context of a toolmakers microscope ?


03/09/2021 14:11:54

Martin, good thought. I was about to go and find some old polarising sunglasses but then for no sensible reason put the thing in front of my computer screen instead. I didn't know these lcd screens were giving off polarised light, but surprisingly when I rotated the block the image of the screen went from clear to black every 180degrees. So you are right !


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