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Member postings for John Haine

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

Thread: Only for Myford lathes
13/01/2020 16:53:19

Big bore lathe has MT4 - but beware that it won't take full length MT4 tapers! I bought one from RDG to make a test bar and it didn't fit - you'd think they would know!

And just now tried I think for the first time fitting the faceplate I bought new with the lathe. The bit of bent steel supposed to keep swarf out of the motor fouled the faceplate! Further investigation showed that when it was fitted they had to bend it to avoid it fouling on the cable gland on the motor - presumably a different motor pattern. If I bend it back to how it appears to have been made it clears the faceplate but won't fit over the motor.

Great British Engineering.

Thread: magic 127 TOOTH ?
13/01/2020 09:36:22

Or even more magic, CNC, cut all those threads, tapers, balls, other odd shapes, etc etc....

Thread: Only for Myford lathes
12/01/2020 22:58:20
Posted by Steviegtr on 12/01/2020 11:29:37:
Posted by John Haine on 12/01/2020 11:14:40:
Posted by Steviegtr on 12/01/2020 10:39:18:

Did you put that on youtube, as I've seen one on there.

There's more than one, but I haven't.

So was it worth doing the CNC conversion. I bet it took a while setting up.

Absolutely. Not too much time but done in stages over the years as I learned more.

Thread: What Vice should I buy (2019)
12/01/2020 19:04:50

Boil to remove superglue.

Thread: Only for Myford lathes
12/01/2020 11:14:40
Posted by Steviegtr on 12/01/2020 10:39:18:

Did you put that on youtube, as I've seen one on there.

There's more than one, but I haven't.

Thread: What Vice should I buy (2019)
12/01/2020 09:47:26

"So my first question is what size vice makes sense? Currently I have a 2 inch machine vice and a 3 inch RDGTools vice which looked big on my CMD10 and a bit silly on the new mill."

What does it matter what it looks like? Why not see how you get on with these and consider a larger vice when you need it? I've been milling for quite a long time and probably 70 or 80 % of the work I do I either clamp direct to the table or to an angle plate. A large vice clutters the table and eats daylight under the spindle.

I do have a 100 mm vice for my Myford VMB, which came with the swivel base. I don't think I've ever used the latter! I also have a little old-style Myford vice and a small one that I bought for a vertical slide (never used) from Chronos - it was a pig's ear as supplied though looked nice, ground all over. After re-machining it and making a new moving jaw it's OK. The latter two I find really useful on the VMB and my Novamill.

Bigger is not necessarily better!

Thread: Only for Myford lathes
12/01/2020 08:39:23

Converted a S7 to CNC.

Thread: magic 127 TOOTH ?
11/01/2020 20:15:00

Um. Well originally a metre was some small fraction of the distance from Paris to the North Pole and a millimeter was a thousandth of that. An inch was 1/36th the distance from Henry VIII's nose to the tip of his middle finger (or something like that). When you compared them an inch was about 25.399999.. mm or something similar.

**LINK** actually shows that the old UK inch was 0.0000017 shorter than 25.4 mm!

Later on when they standardised lengths internationally it was hard enough just having a standard metre without having to maintain a standard inch as well, so at some stage (in the 1930s I think?) it was decided that the imperial world would move towards an inch being DEFINED as 25.4 mm exactly, which was pretty close to the "old inch". Had they decided to make it 25.6 mm it would have been nearly 1% different which is a lot in precision measurement. Actually conversion is very easy, 25.6 would only have been useful for some binaary divisions.

Thread: Sent lathe back
11/01/2020 10:11:59

One problem with the early Unimats is that they used a different spindle thread, M12 x 1 IIRC, whereas the later ones and the C0 style lathes use M14 x 1. So it may be harder to find new accessories.

Thread: The cultural status of engineers in the UK
10/01/2020 10:52:52

Please PLEASE don't lets get started on this hoary old chestnut yet again! This has been discussed to death here I'm sure and in publications from the engineering institutions for at least 50 years. And it's not just an issue in the UK. We all know that without engineers society would be nowhere, just suck it up and get on with life.

Thread: Co2 emissions.. Steam or diesel best?
10/01/2020 10:47:55
Posted by flyingkipper3 on 10/01/2020 09:51:47:

And electricity is still mainly from coal fired power stations.

Actually the percentage that coal generates is single-digit.


Thread: VFD Question
09/01/2020 13:55:18

The transformer doesn't do anything to correct the balance. The load current can be resolved as "symmetrical components" which are fwd and bwd rotating balanced sets of 3-phase currents plus equal "common mode" currents which are equal and in-phase with each other on the 3 lines. The same symmetrical components will exist on both sides of the transformer but be differently manifested because there's no neutral. What I think it means is that two of the windings on the transformer supply all the current while the third carries no current. Whether this matters depends on the transformer capacity relative to the load.

09/01/2020 09:33:31
Posted by noel shelley on 09/01/2020 00:03:20:

....In the village I live in they only brought 2 phases in ! even the farms have to make do. Or instal there own generators.

I think there is a transformer arrangement that will generate a 3 phase supply from 2 phases at 120 degrees.

"The Pilons only carry 3 phases, usually up to 133,000 volts then reduced to what is needed. " - Actually I think you will see another cable right at the top of the pylons, which connects them all together and to the neutral/earth at each end. Partly so that stray cows and walkers don't electrocute themselves when they touch the legs if there's an earth fault, but also to carry the unbalance current which otherwise could take an unpredictable route home and cause various problems.

Thread: Have a look at this, view from the chuck
08/01/2020 22:36:57

Just because you can, doesn't mean you should!

Thread: VFD Question
08/01/2020 20:56:59

I regularly use the VFD on my mill at 10 Hz and below for power tapping. Though the power may be low there's plenty of torque. In fact you can drive an induction motor at very low speed or even zero speed and get full torque using a vector drive. Power not necessarily a good indication of usefulness.

08/01/2020 20:56:58

I regularly use the VFD on my mill at 10 Hz and below for power tapping. Though the power may be low there's plenty of torque. In fact you can drive an induction motor at very low speed or even zero speed and get full torque using a vector drive. Power not necessarily a good indication of usefulness.

Thread: Sieg SX2.7 front T slot
08/01/2020 19:46:49

Table stops, probably. Extremely useful.

Thread: Electric motor ratings
08/01/2020 19:45:40

Some confusion may arise because in SI units both electrical power and mechanical power are measured in watts. So a motor could be rated at 1500 W consumption but deliver 750 W at its shaft. So the new mill could "consume" 1500 VA (roughly, watts if it was a resistive load), have a lousy power factor so it actually absorbs 1000 W of real power, and an efficiency of 75% so it delivers 750 watts.

Thread: VFD Question
08/01/2020 16:03:06
Posted by norm norton on 08/01/2020 15:52:14:

Ahh.. Thank you Martin and Andrew - got that.

So I (and perhaps two others in the world) have been misunderstanding the output from the workshop VFDs that we use. It is 240v phase-to-phase, and if there was a neutral it would be about 133v on each phase to neutral.

I guess the rules of physics say that one cannot phase shift 240v AC by 120 degrees and again by another 120 degrees, otherwise we would get 415v quite easily.


You can shift it using a resistor-capacitor circuit, but inefficiently (because of the resistors). To get high efficiency you need at least two power feeds with a phase difference. There's something for example called a Scott transformer that will generate two phases at 90 degrees given a 3 phase supply, or vice-versa.

08/01/2020 15:58:09

To save Andrew doing it. It a simple VFD the mains is full-wave rectified and charges a big capacitor up to 230 x sqrt2 = 325 V. It then has 3 high-voltage push-pull output stages run off this voltage to drive the 3 outputs. Each one is driven by a variable mark/space PWM signal at perhaps a few kHz. At 50:50 m/s the effective average output of one of these is 162.5 V, and it can be varied down to 0 V and up to 325 V. In effect this is +/- 162.5 V relative to an average of zero. If you vary the m/s ratio in a sinusoidal manner with time at 50 Hz you can generate what appears to a motor as a 50 Hz sine wave with a peak voltage of 162.5 V.

Now there are 3 output stages and they are driven to generate waveforms 120 degrees out of phase. If you connect a motor winding between two of these outputs it sees a voltage of 162.5 x sqrt(3) = 281 V peak or 199 V rms. This is not too much lower than the winding would see if it was connected between a line and neutral of a standard 3 phase supply so it will run with nearly the same current and power as normal.

You can also play games where the waveform is not sinusoidal but the peak is "flatter", which will increase the rms voltage and current to compensate for the lower peak voltage. There's nothing particularly sacrosanct about sine waves.

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