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Member postings for Martin Connelly

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

Thread: Free sources of materials.?
11/01/2016 10:07:08

The auminium disk in hard disk drives can be cut up to make small mirrors with no ghosting from a layer of glass over them. I know welders who cut them up and mount them on a piece of welding wire for weld inspection down small holes and in pipes.

Martin

Thread: Change Gears on Myford ML7R
11/01/2016 09:50:08

Swapping change gears must be one of the jobs where throw away latex gloves could be used then. I know what you mean about messy. People who have Norton gearboxes and have never changed the headstock gears don't know how lucky they are. Feed rate changes were more likely than screw thread changes for me. If made me tend to leave the feed rate at a low value and suffer the time delay this resulted in. It is part of the reason I put CNC on my machine. Not to be wonderfully clever with what I could do but to be able to thread and feed without changing gears. I also was missing some gears from the set required to do all common threads (no 127 tooth amongst others so approximate metric was the order of the day). I did make some aluminium gears when I really needed them. Not running change gears even when perfectly set up is also quieter but that is just a pleasant by-product.

Martin

Thread: Neat cutting oil. (recommendation)
11/01/2016 09:37:21

We used to have a trike filled vapour degreaser in one of our departments. Worked great on outside surfaces but not so good on the inside of things like pipes as the part heated up before any vapour condensed inside it. The spray lance did not give enough flow to clean inside larger pipes. One of the guys decided to clean off a bending machine using some trike as the machine was covered in very sticky drawing oil. After using it he stopped for a smoke and promptly collapsed. He seems to have recovered with no ill effects. I think the breakdown products from heating trike included phosgene gas.

The vapour degreasing process was replaced with a pumped floew, filtered, heated light oil tank (similar to paraffin/kerosene without the smell). The oil is only clean until it is first used and after that is contaminated with whatever oil is washed off parts (including the sticky drawing oil). The reason for change was the Montreal Protocol as trike helped with ozone depletion. It was also used as propellant in some aerosols and has been replaced in some cases with flammable butane which causes other health, safety and environmental problems.

To keep on topic, I use Rocol Multisol "soluble" oil.

 

Martin

Edited By Martin Connelly on 11/01/2016 09:38:54

Thread: What Did You Do Today (2016)
11/01/2016 08:54:41

Some of the routes that the Flying Scotsman will follow in the summer have been published. One of them is on the train line I can see from my house. However it is about a mile away and even with binoculars is not a great view due to trees. The local garden centre car park is right up against the railway line and on a level with though and the four lines of wire that make the fence are not going to hinder the view at all. It might be a case of get there early for a good spot.

Martin

Thread: How do I make this ?
08/01/2016 19:17:01

You can use the vertical stub method you ask about but you need an extended arm to control it. I think there are YouTube videos of it being done but do not know what search terms will find them.

Martin

Thread: Problem with electric motor
08/01/2016 19:08:51

There is probably a start capacitor, a start coil and a centrifugal switch to switch the start circuit off when the motor is up to speed. Two possible problems that can occur with motors left in storage for a time is the capacitor degrading for some reason but possibly more likely is the centrifugal switch jamming. This is a mechanical operation and dust and grease can jam it up. It is often possible to hear a click as the switch makes contact after power is switched off when the motor is spinning down. Since you can get the motor to run I suggest running it then turning off the power and listening for this click as the motor slows. If you hear nothing then the next step is to open up the motor casing (with power disconnected) and seeing if the switch is jamming and can be cleaned and put back into use.

Martin

Edited By Martin Connelly on 08/01/2016 19:09:55

Thread: Do you finish every project before moving on ...
08/01/2016 19:01:19

If you are in the middle of a project an find you need to make a tool or jig for that project does that count as two projects or just one?

Martin

Thread: Unwanted Taper on Big End Bolts
06/01/2016 21:14:51

So what is needed is a perfectly made centre drilled end in a perfectly straight bar mounted in a perfectly made chuck or collet perfectly mounted in the headstock with the end located by a perfect centre in a perfectly aligned tailstock and all this done by a person asking questions as a beginner. Perfect!

Martin

Thread: What do i need for my new setup
06/01/2016 18:58:45

A lot of lathes have morse taper spindles but certainly not all. Also morse taper tool holders for a mill do not have a tang, they have a threaded hole for a drawbar. This means that some tooling such as a drill chuck may be used on lathes and mills but are not necessarily easy to remove compared to a tailstock that ejects tools when retracted or spindles with a slot for putting a drift in. This is where the comments about banging on a draw bar or other length of rod comes from. Do not put milling cutters in a drill chuck, the cyclic side loading can loosen the chuck with unhappy consequences. If you have a choice between morse taper and R8 on a mill the cost of tooling to fit it should be something to consider before making a choice.

Martin

Thread: Unwanted Taper on Big End Bolts
06/01/2016 18:40:53

Tony, I have used a centre with collets and chucks as well, I was referring to a discussion here http://www.practicalmachinist.com/vb/south-bend-lathes/turning-between-centers-vs-chuck-130393/

If the centre is not aligned to the spindle axis of rotation it can move the part off the centre of rotation and so cause problems, that was why I was asking if the tailstock alignment had been checked. The original question is under the heading of beginner questions so it seemed to me to be a legitimate query to the op.

Martin

Thread: Rotary Table
06/01/2016 14:59:34

Not quite true Nicholas, see the message at 13:35.

Martin

Thread: What do i need for my new setup
06/01/2016 14:08:32

Ega, maybe that's something to check for then when looking at mills. If it is a morse taper spindle does it have an easy release mechanism?

Martin

Thread: Rotary Table
06/01/2016 13:35:16

Are you planning to put chucks off your lathe on it? This thread rapidly followed the assumption that that is what you will be doing. If not then the answer is possibly whatever fits other criteria such as size, weight, height and cost.

Let us know how you intend to use it and if there are any specific things you have in mind for it or if it is a "need to get at some point item" that you are putting some forward thinking into.

Martin

Thread: Unwanted Taper on Big End Bolts
06/01/2016 13:16:25

There are a lot of people that will take the view that if you are using a collet or chuck you should not also use a centre in the tailstock. Any slight error in the tailstock alignment will introduce a distortion in the bar and result in odd errors such as you are reporting.

As Andrew said you should be moving the saddle and with power feed if you have it.

Have you either bought or made an accurate test bar to check tailstock alignment? How did you align the tailstock or have you ever checked it in any way?

How accurate is the 1/2" diameter of the bar and is the collet an exact match to it. Is the collet and its seat perfectly clean and free of damage?

What rpm are you running at? Carbide inserts work best at high speed and the speed for a diameter like this with carbide inserts may need to be as high as 2000rpm for a good finish. They also need a high feed rate to get the best from them otherwise they can rub since they are relatively blunt compared to a well sharpened and honed piece of HSS.

If you have a plain bar to put a thread on you could turn it between centres. This gives the option to measure the thread and put it back in the lathe with the correct positioning to cut some more depth in the thread. Once again this requires that the tailstock is properly aligned but that can be checked as you start to reduce the bar, it should be parallel after each cut, A steady rest can be used if the bar is going to get a high slenderness ratio as its diameter reduces.

0.1mm cuts on a Ø7.6mm workpiece may be a problem for carbide inserts. The centre of the workpiece will try to move away from the tip and so cut less than at the constrained ends, have you any HSS to use for these finishing cuts? It will be probably be sharper than a carbide insert and the force pushing the workpiece away will probably be lower as a result.

Martin

Thread: What do i need for my new setup
06/01/2016 10:36:44

Consider power feed for the mill. If it is not an option for the one you look at you may soon finding yourself wanting it. It is easier to get a mill you know can have it added in the future without a lot of messing around. Power feed does help with finish as well, it also frees up hands for other things such as brushing away swarf and spraying coolant or wielding a vacuum hose.

As Bazyle said when looking at mills bigger is usually better, you can do small things on a big mill, the other way round does not work. A lot of people have bought the 6x26 (Warco VMC or Chester 626 for example) milling machine and found they need to make a riser for the head to get acceptable clearance. This is just an example of what happens if you get a mill that seems big to someone new to mills.

As Tractor man says DROs make life with a mill much easier. If you buy a mill ask if there is an option to have them fitted at the time of purchase, you do not have to buy it but it will tell you if it is possible to add yourself if required in the future.

Clamping kits and/or vices are something you will need to use the mill as well as some end mills or other cutters.

I would suggest you avoid a morse taper spindle if possible, some may disagree, because of the number of posts I have seen asking for suggestions on removing ones that are stuck. I also think that having to bang away on a drawbar if one is a bit tight to remove does not do a lot for set up when trying to maintain position between tool changes.

Martin

Thread: Lathe tool geometry for threading aluminium
06/01/2016 09:48:51

I agree with Hopper, the backgear is only going to drive the motor train if it is engaged for hand powered threading on my lathe. I would disengage the backgear and leave the drive pulley on the spindle unlocked so the motor was not able to drive the spindle, much safer when a crank handle is sticking out of the back of the spindle and no effort going into manually turning the motor.

Martin

Thread: Recommended material suppliers
05/01/2016 21:40:54

No, Speedy Builder5, he works for a Peterborough engineering company but they have a small workforce embedded in the place I work. He has to buy his materials through the Peterborough purchase department but what we are doing is not a formal setup. He has a regular requirement to supply a short piece of 1/2" diameter phosphor bronze so just wants to cut a piece off a bar with a hacksaw and file it flat on the ends. Almost all the machining done in the place I work is now done on CNC machines and anything else is put out to sub-con. The last manual machining department was closed last year. Add on the £70 an hour labour cost for in house work and you can see why he wants to use an informal system to keep his costs down.

I am buying the 1/2" diameter personally and so keep the larger diameter personally. He has already paid out for the large diameter bar but gets what he wants without any further cost reducing its diameter. I get the large diameter bar for the cost of the small diameter bar. Hope this makes more sense now. 

Martin

Edited By Martin Connelly on 05/01/2016 21:47:20

Thread: Emco Compact 5 Motor Problem
05/01/2016 20:00:00

Can you mount the motor on electrical isolators to see if that stops the fuse from blowing? That would confirm if there is a short to earth from the motor. If you put a low wattage incandescent lamp in series with the motor to restrict the current you will also find out if the fuse is blowing due to an internal short in the motor.

Martin

Thread: Recommended material suppliers
05/01/2016 19:45:09

I've just ordered some pb102 phosphor bronze from Maccmodels. Some one asked me today to turn a 350mm length of 26mm diameter pb102 down to 1/2" diameter. I had to check twice that I had heard him correctly. He has to buy from approved suppliers for his stock material and he asked for 1/2" diameter and got the 26mm at the price for 26mm bar. I said it seemed stupid to throw 3/4 of it away as swarf. We struck a deal instead, I keep the 26mm diameter bar and supply him with two lengths of 200mm x 1/2" which is what I have ordered. It saves him from having to pay for the machining (some bottles of beer in my case) to get the size he wants and I get a nice piece of raw material.

Martin

Thread: Warco BH600G Modifications (clutch, gears, 3 phase)
05/01/2016 18:33:17

Use a pound coin. It is very similar to aluminium bronze and the only part that needs to be in the correct material is the face in contact. There are plenty of forgeries in circulation so if you use one of those you are not breaking any law if you destroy it.

Martin

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