Member postings for Andrew Tinsley

Depends on how much milling you do! Simple as that! Work out how many times you chuck away blunt cutters. It is then easy enough to see if it is worth it.

I am building a Quorn, just for the hell of it, I have access to another completed Quorn and I don't think I could manage without. I don't quite know where all these cheap cutters are on Ebay. Every time I bid, I lose out to what I think are silly prices. Maybe I just strike unlucky.

Andrew.

It takes me forever to do things! My worst trait, is when faced with an operation that looks awkward. I spend hours working out what could go wrong and how to avoid those problems. I usually find that once started, the operation goes quickly and smoothly. Then I wonder why I took so long thinking (and avoiding!) doing the job.

If you enjoy what you are doing, then who cares how long it takes. I have multiple projects on the go and I shall never finish half of them, having a very limited lifetime left! But the enjoyment is in the travelling, not getting to the destination.

Andrew.

Thanks Michael,

I will do that and send them a photo of the inverter. Dave, that Is a very interesting piece of information. I too remember a problem with bearings on normal single phase motor which was traced to high voltage pulses on the mains supply.

I am a little non plussed by the ABB paper. I was under the impression that the "3 phase" out of an inverter was in fact a square wave, so the leading edge would produce such a high voltage spike when applied to an inductance such as a motor winding. So the problem would be endemic. I may well be very wrong about the square wave bit. there may well be some attempt at wave shaping in modern inverters.

I had to develop a chopped DC "3 phase" supply maybe 40 years ago plus and my simple solution was to use chopped square waves. I hope things may have moved on from there. I am sure someone will put me right!

Andrew.

Hello Andrew,

I think your concern about the energy stored in the motor coils and what happens when it is switched off, is something of a red herring. This scenario occurs when any motor is switched off, be it a single phase or 3 phase motor. There is no problem with high voltage spikes that can ruin the motors insulation. If it were true, there would be an awful lot of motors that self destructed!

The real problem is the voltage spikes that are fed back to the inverter. I always put a good quality mains filter in the power line of any motor that I install, be it 3 phase or single phase! the reason I do this is to ensure that any voltage spikes do not get onto the household mains supply. OK the filters do not eliminate spikes altogether, but they certainly reduce the amplitude.

Andrew.

Hello,

This seems to have caused some "discussion"! The inverter that I am talking about is an ABB unit. It was used in a small air conditioning system. Unfortunately I can't find the model type, I suspect the adhesive label with the details has come adrift (there is a sticky oblong patch on the inverter, where I think it might have been). Closer inspection of the remaining label says that it is rated at 2,2 kW (not 2.0kW as I first stated). Now if this is input or output power I don't know. It is obviously an industrial unit and built like a tank, so not a tiddly hobby unit! I suppose I could try and browse through any published ABB information to see if I can find the model

There were two of these units being replaced, so I may well see if the other is still available. If so I will buy it and test it to destruction or not as the case might be. I would usually try and find the manufacturers info , but not knowing the model type, I was a bit stymied. It was installed new, about 10 years ago.

Apologies as I seem to be in the dog house asking a generic question, when I should have worked it out from ABB published data. However the above explains why I didn't go that way in the first place.

My only other experiences of inverters was a single phase in / single phase out dodgy ABB VFD. The second experience was with a new Fuji inverter. I tried to read the very thick book that came with that one. Now I do have a fair bit of knowledge about electrical and electronic matters. Even so I found the Fuji instructions to be almost incomprehensible. If that is typical of inverter instructions, I would be in severe difficulties. Sorry about the off topic comments on instructions, but I was very disappointed with a quality product's instructions. It assumes you are an inverter expert from page 1!

Andrew.

Thanks Joe,

A very interesting summary of the does and don'ts. It certainly puts some myths to rest.

Thanks again,

Andrew.

Hello,

I didn't find the Harold hall book, or indeed the Arnold Throp title to be of much use, unless you are an absolute beginner. Both concentrate on vertical milling, so there is a gap to cover in the Workshop series.

I perhaps sound a little harsh, but already having a fair bit of experience on the mill, both titles didn't give me much illumination into the finer points of milling. Both books are an excellent introduction if you are starting from ground zero.

I don't know what the last title in the workshop series is like. This is titled "The Milling Machine" so maybe I should buy it and find out.

Andrew.

Edited By Andrew Tinsley on 01/11/2017 12:40:20

I have used a similar product called Lumiweld if I remember correctly. It works and works well. BUT it needs some skill to perform. You have to scratch through the melted material to get rid of the oxide layer on the aluminium. A stainless rod with a point is needed. So you need 3 hands for a period. Once the "solder" takes, then there is little need for further scratching.

Beware that if there is a slope away from the weld site , then the solder very easily runs off! I tend to use a V preparation (like arc welding prep). The molten solder then will be retained.

You need to practice, most people that say that aluminium eutectic rod doesn't work, don't have much patience! It does work and is both strong and effective, but you need to practice in order to get the knack. All that has been said in previous posts should be headed, cleanliness, sufficient heat etc.

The eutectic rod is quite expensive, but that is because it is a niche market, I tried some from Ebay, which was a lot less than most, not quite as easy as Lumiweld, but not much difference overall. I would use that again for economy.

Andrew,

Hello John,

My friend wants to run the 110watt motor together with one of the 750 watt motors. The 110 watt motor is powering a small grinding attachment which goes on the tool post of his lathe. I suppose they could be switched on simultaneously via the single phase "power in" to the inverter, but it isn't an ideal solution.

I too, suspect that a lot of myths are floating around concerning electronic inverters. Like you, I wish that someone that has a lot of practical experience would put us straight!

Andrew.

Hello Dave,

It was indeed a solid state type. I have just been speaking to a local fellow, who does exactly the same thing with his electronic inverter. So that appears to two people who do this sort of sabotage to their inverters, without any apparent harm. Makes me think that maybe they are right!

If it were my inverter then I would not hesitate to follow their example. However I don't want to damage someone else's kit.

Andrew.

Interesting responses! I have had an email from a gentleman who has been running his 5HP inverter for 10 years. He uses it to run motors in parallel AND switches them on the 3 phase output! These are serious motors, one on a Schaublin mill a second on a Chipmaster and the third on a Startrite drill.

He simply treats the inverter output as genuine 3 phase and never has a problem. So in the real world, it would appear to be rather different than most model engineers appear to think.

Andrew.

Thanks for the point about not switching on the output of the 3 phase. I did wonder about this. I suspect that if the 110 Watt motor was switched on (on the 3 phase side) while one of the 750 watt motors was running. It should not be too much of a problem. But maybe totally wrong on that one!

Andrew.

Hello Chris,

Thanks for your input. I should have made clear that the inverter in question is of the electronic type. i.e. full wave rectification of the incoming 240 volt single phase supply, then smoothing and finally chopping into 3 phase output. So your experience with a static inverter isn't really applicable to this particular query.

Andrew.

I now have a good quality 2kW single to 3 phase inverter for sorting out a friends electrics.

He has 3 items he wishes to run on this inverter. Two have 750 Watt 3 phase motors and the third has a small Parvalux 3 phase motor rated at 110 Watts.

Now he doesn't want to do anything clever like soft start, feedback, and variable frequency. He wants to treat it as if he had 3 phase mains, full stop!

He queried me on running one of the 750 Watt machines at the same time as the 110 Watt machine. As far as I can see there should not be a problem, as he doesn't want any fancy implementations. The only thing I would do is to have a current limit on each phase.

So tell me that I am wrong! Please don't go on about the fancy things that can be done, he is quite adamant that he does not want anything except raw 3 phase at 50 cycles!

Andrew.

I really don't care a tinkers cuss what people think of me or my hobbies! Water off a duck's back!

B###s to the lot of them,

Andrew.

So all I need are a pair of outside jaws to complete the job. I have found them on the Thame website and they are expensive! I shall keep a lookout over the next few months and see if I can get them on the bay, or similar.

Having got the inside jaws cheaply, at least I can pass on the second chuck to a needy fellow engineer. So job almost done. Well worthwhile, as the chucks are in near new condition. People say the jaws are expensive, but I wonder what a new chuck would cost if they were made today? I bet you would not get much change out of £500!

Andrew.

Thanks Clive!

just got the NOS 3.25" inside jaws for £45, Considering what a new 3.25"Griptru would cost if the made them today, they are a bargain!

Andrew.

Thanks gentlemen,

I will give those leads a try.

Andrew.

I have what appear to be two small Pratt Burnered Grip tru chucks. The diameter is 3.25 inches or about 83mm. The name plate is missing, but they look to be a smaller version of my 4 inch Grip tru chuck in every respect.

Now I salvaged these off an experimental glass lathe which had hardly been used. The only snag is that one is fitted with inside jaws and the other, outside jaws! At least I have one set for both chucks!

Is it possible to buy another set? Or is Pratt Burnered no longer interested in supplying spares for these chucks? Anything else that would fit? or does anyone have any to sell?

I would like to get another set of jaws, then I can pass one of the chucks to a friend who could make good use of it.

Andrew.

P.S. The Pratt Burnered website is totally unhelpful when it comes to spares, at least I can't find a useful page!

Thanks everyone,

It looks like the thick lino material that I am thinking of is unobtanium from normal retail outlets. I will try Ebay for some roll ends as suggested.

Andrew.