Member postings for Martin Connelly

The same bracket on two different Chester mills. A VMC style and the Super Lux.

Martin

I often have ear defenders on when using my belt driven machine, the covers over the belts can ring quite well.

As for the difference between the VMC and the Super Lux styles there is a big difference in the size of the table and the best way to compare them is to see them side by side. If you can, get to a showroom. or somewhere else where you can compare them easily.

Martin

If they make it too efficient we will have to devise new ways of heating the interior of vehicles when the weather is cold.

Martin

This is the sort of job where mounting a piece of metal in the lathe and then machining it to create a mounting fixture would be good practice. As long as you do not dismount it it will have theoretically zero run out. The actual amount of run out may be tiny or immeasurable but there is always some give in the spindle bearings that varies with the pressure on them when something is cut.

Alternatively have you got soft jaws for a chuck that can be bored. Once again this will give a low tir bore to mount things in.

A third option is to mount your existing fixture in a 4 jaw independent chuck. Do you have one or is there some other reason why this is not an option?

Martin

**LINK**

This video shows a Vardex M6 milling cutter being used to cut an oversized thread for an insert. The material is an aluminium alloy and the G-code for the cutter movement was generated by a program downloaded from Vardex. You tell it the tool part number and a few other parameters and it produces the code. This can then be used on its own or cut and pasted into a program. In this case there was a PCD wrapper around the Vardex code so that the holes were each at x=0 y=0 for the threading process so the Vardex code could be used at any point designated as 0,0.

The code has a circular approach and retract from the centre of the hole to the cutting radius and uses two passes. I did not check the code but I suspect that it was cutting equal volumes at each pass.

Martin

You can use FM radios in the workshops where I work but DAB is useless. Lots of metal in the walls, roof and stanchions is probably why the big difference.

Martin

Drawing of a drive part.

**LINK**

Item 6 being machined. Ø33mm 16tpi UNC thread. I know it is far from standard but that is what was required, using 316L stainless pipe as raw material. The tool is home made using Horn inserts. Hand written Gcode with G03 as the code.

**LINK**

The finished item between the two parts it joins.

**LINK**

The drive is driven from one end and braked at the other and a left hand thread was required to ensure it tightened rather than loosened because of the applied torques.

The issue of helix angle and internal thread milling has been covered in the past by manufacturers and users of tooling and the figure quoted as a rule of thumb for not causing a problem is that the tool is 70% of the finished thread size as a maximum. This fits in closely with the 2mm thread being cut with a Ø1.55mm tool.

Martin

I have just (between Christmas and the new year) turned a dumb-bell test bar between centres. The reason was to have a bar purely for setting the tailstock correctly and also to play around with a vertical shear tool. It also allowed me to use a newly acquired centre for the lathe headstock. After centre drilling I used a rusty old piece of steel about Ø25mm turned down the ends and centre sections to about Ø22mm with a carbide tipped tool (rough finish on this unknown steel). This left two 15mm bands for the fine machining. I cleaned these off with an ordinary HSS tool then used a HSS vertical shear tool to give a very fine finish. Measured the diameter difference of the test bands, adjusted the tailstock set over and repeated until the bands were about the same diameter. The biggest problem was adjusting the tailstock with worn slot ended grub screws. I have ordered some hex grub screw replacements (Colchester lathe spares!) to make it easier. I found that tightening the barrel clamp had to be done to the same point each time and the clamping of the tailstock to the bed was also able to change things noticeably. I found the best way to get the screws for set over adjusted was to calculate the adjustment required (half the difference on the test bands) as a degrees of turn for the screws and try to move them this amount.

I ended up with two test bands that are within 0.005mm of each other and a very smooth finish. I stopped at this point as I think that will do for what I want. I suspect the vertical shear tool or some fine abrasive will take off the difference if I wanted it better but this was an exercise in setting the tailstock more than anything else and the slot head screws made fine adjustment hard.

For the vertical shear tool machining was done at 400rpm 0.005mm per rev feed. I held a 1" paintbrush against the band when cutting, with suds applied to the bristles as required, This gave a thin film of cutting fluid and at the same time collected any fine particles that were being carried around the band. When the band was done each time there was a layer of very fine metal dust gathered on the brush looking like a silvery paste.

Martin

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

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

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

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

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

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

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

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

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

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

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

Martin

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