Here is a list of all the postings norm norton has made in our forums. Click on a thread name to jump to the thread.
|Thread: Bridgeport Circuit Questions|
There have been some very helpful comments on this subject before, so I do hope that a few of you can help me with three specific questions. I have a Leicester made Bridgeport (1984 I think) with pancake motor and belt drive, fed from a Transwave static converter of 2.2kw. It has been fine for a couple of years and I only ever run the motor at slow speed.
But, I was switching between forward and reverse, probably did not wait long enough for the motor to stop properly, and now if I press 'run' no contactors are latching so it will not spin up.
I have checked the three feeds from the Transwave arriving in the cabinet and I am getting 420v, 420v and 0v across the three pairs (which I think is correct), the six fuses (FU1-3, SFU1-3) all test ok, and if I manually press contactor C3 the motor runs but does not latch.
Q1: could anyone let me have a detailed circuit diagram for the cabinet please? I have the 1979 drawing from the manual but it tells me nothing I can follow. I want to be able to trace from the 'run' button to contactor C3 that I would guess is not firing.
Q2: anybody have an idea what may have blown/tripped if I did reverse the motor too quickly?
Q3: A year ago I did have in mind fitting a 90L frame motor on an adapter plate in place of the pancake motor with a Newton Tesla inverter and remote handset; maybe this problem might spur me to do it. My question is how to keep the 6F long feed working if I take all the three phase out of the cabinet. I think the 6F control board only needs 110v, so is it sensible to rewire the input to the big transformer from 420v to 220v and use a new 220/240v fused supply? Will the contactor for the long drive still work so that I can isolate it still from the front panel?
Edited By norm norton on 17/02/2016 14:42:04
|Thread: Rotating Centre Problems|
Andrew - no nothing like that speed, I dare not with the lathe dog and a fixed centre! It is a 0.2mm radius finishing insert. The literature says that EN8 tears on machining but polishes up well and that is just what I find. But thanks for the info - I might try a piece in the chuck and run it up to 2,000 to see any effect.
Jason - thanks for your support
(p.s. previous post typo, bearing journals are 1.156" long not 0.625"
Mike, sorry if my descriptions do not add up, it's difficult describing everything. Turning EN8 leaves me a fine but still rough surface. The final 0.0008" (or so!) I removed CAREFULLY with 240 and 400 grit paper, measuring as I do so, then 1200 to polish to a shine. I agree, it is not a precision ground surface, I don't have that sort of equipment. But I now have two of my three axles finished and each journal is 0.7880" +/- 0.0002" and within 0.0002" along the 0.625" journal length. Good enough for a plain bearing surface sitting inside 0.7888" bronze axle boxes. Goodness knows how precise the axle boxes are after I lapped them but the plug gauge tells me that is what size they seem to be. 0.0008" is what I want for the oil film clearance (0.001" per inch)
But never mind precision discussions. Happily my MT3 live centre readily came apart and it has a nice expanding taper sleeve around the rollers with an adjustable front screw. So after cleaning I can adjust it to make a good useable centre.
Many thanks for the comments. Nice link back to 2013, thank you Andy.
Agree with what is said and today have done it properly with a carbide tipped fixed centre. You do have to try to leave 'a quarter thou' clearance between tip and socket or the grease is pushed out and it starts getting warm. I decided to run it with the 'quarter thou' slack for all but the final cuts when I removed all play. I do wonder if a high performance grease will be better, moly grease as you suggest Ian.
Last night when posting I was pretty miffed at finding the £50 multi-tip live centre was out and wondered what you thought. Checking today, swapping tips, ensuring all is clean, it clearly shows a run out of some 0.0008". I have had it for more than a few years but never used it for a precision task. I suppose one might be lucky and buy another £50 one and find it reasonable, but I now realise this is the too-cheap end of the market. I see that Bison and Rohm items are around £150 and even budget Vertex are £80. I have come to the point where I have stopped using the hobby suppliers for tooling. Not sure that I will afford a Swiss Gepy with its 1 micron precision though…..
My Czech MT3 item looks like it comes apart so hopefully I will find a taper bearing in there and can shim or adjust it. The other cheepie one is going in a bin!!
Mike, I have got a reground Super 7, but more precise is my Harrison 140. I am machining the axle journals down to 0.0008 - 0.0010" over size and then finishing with 240/400/1200 grit paper. Knowing where you are for sizes all becomes quite straightforward with a good digital micrometer - the Mitutoyo has been one of my best second hand purchases. You are right about the difficulty of trying to get tenths of a thou along a job. Bed alignment with the head, and/or tailstock alignment with the axis, means that I am well aware that we are always cutting tapers!. Several tenths of a thou in a couple of inches is the best I can manage between centres. The Harrison is reasonably good from its headstock though. When I set it up a couple of years ago an alignment test cut of a hefty bar in the chuck gave 1.1094" at one end and 1.1092" eight inches away.
I am making some axles, appx. 6" long by 3/4" diameter, from EN8. After facing and centre drilling each one I am mounting them between centres on the lathe and turning the journals at the tailstock end.
Now, I am measuring the finished and polished journal diameters with a Mitutoyo digital micrometer and so know what is happening to 0.0001". I was going to use a solid centre in the tailstock but decided to try an older MT3 rotating one. The journal ended up exactly where I wanted it but I then noticed the rotating centre had about 0.003" free sideways play so replaced it with a MT2 modern but unbranded item bought recently.
The turning seemed to proceed well but I had a few problems measuring the diameter as I got to the finish. When I took the work out to see what was going on I was amazed to find that the journal was OVAL with the peaks some 0.0014" larger in diameter than the waist. This had happened on two separate journals with the same result.
To test each centre, I put one of my satisfactorily round journals between centres and measured the total run out at the tail stock end with a dial gauge at the top journal point.
Solid centre = <0.0001"
MT3 worn centre = 0.0002 / 0.0003"
MT2 modern = 0.0008"
Since the MT2 modern one has replaceable centre tips I figure that the tip I am using is not in line with the bearing axis. But what I cannot understand is when I cut with it how does 0.0008" TIR out of true result in an oval piece of work that is effectively 0.0014" out of true.( i.e. twice as much assuming my measurements are all +/- 0.0001" ) . Or has the tip gone further into its socket and aligned better as I have swapped things around?
Any engineers with experience of rotating centres please? Am I expecting too much and should I stick with a solid centre? I will try and get the MT3 one apart to see if I can replace the bearings perhaps.
Edited By norm norton on 29/12/2015 19:56:55
|Thread: Grinding a four-jaw chuck|
Usually, you only need to remove a few thou from the tips of the jaws to get them aligned. I have successfully ground a couple of three jaw chucks by the established method of: place a centre in the headstock spindle, remount the chuck, support a MS bar of around 3/4" between centres, apply grinding paste to the bar and gently apply jaw pressure between rotating the chuck under slow rotation, hold the bar in a leather glove. This way you are closing the jaws on the scroll and will hopefully get a TIR of 0.0010"-0.0015". All the usual warnings of grinding paste and thinking how you CAREFULLY go about this apply.
If your jaw tips are very bad, then perhaps they could be reprofiled out of the chuck? I don't think you you want to end up with jaws that have a large convex contact face.
|Thread: useful info|
Who remembers being taught SOHCAHTOA at school?
It gives you all the formulae for the right angle triangles in that chart.
Sine of angle=Opposite/Hypotenuse; Cosine of angle=Adjacent/Hypotenuse; Tan of angle=Opposite/Adjacent.
|Thread: Bridgeport twin speed motor phase converter or vfd?|
Dave - thank you for the idea of mounting using the four end cap bolt holes on a foot frame motor. With a 90L frame size that possibly gains around 15mm of shaft extension compared with a flange mounting. The mounting is probably not 'manufacturer recommended' but should be strong enough into the main body.
JS - thanks for all the shaft extension info. Could you give me an idea how you would modify the motor to have a longer, imperial shaft? If it involves taking it apart, and welding on a new shaft while the rotor is red hod and spinning in a lathe, I think I will leave that to you and your special skills
With the 2.2kW Transwave I run it at No.4 for Bridgeport slow speed, and it needs maximum No.8 to hold the high speed. Boost will kick in when you first start, but you are supposed to select the lowest number that will sustain drive without boost when a moderate cut is applied. Apparently there are trim resistors inside the Transwave that sometimes need adjusting. The 2.2kW model is only just big enough for the pancake motor. I think it is not recommended to run the coolant pump or the table drive unless the motor is running first, because the Transwave will not supply a proper waveform at lower current loads. The purpose of that switch is to optimise the internals to match the load.
By 2-speed I guess you are referring to the 'pancake' motor which is so called because it is wide and not very tall. They run at 2700/1420 RPM and need 380/440V. According to what I have read and been told, they cannot be run from a VFD as they are and neither can they be re-wired internally to let them run from 3 phase 240v. They are also energy inefficient apparently.
I have one also, and a static Transwave 2.2kW. It will only drive the higher speed if I switch over the motor while it is still running at the lower speed. But, I find I have no need for the higher motor speed in all the cutting I do.
Perhaps your solution is the same as the one I toy with. I would like to fit a metric, flange mounted motor with a nominal 1400 RPM running from a VFD. What is needed is a thick steel adapter plate to mount the motor flange and replicate the pancake motor flange to bolt down on the Bridgeport.
Perhaps JS has been here before and could supply an adapter plate? Otherwise I might get round to measuring it and getting one laser cut. The motor pulleys will need modifying for the metric spindle, and you need a separate supply for the table feed and coolant.
|Thread: Bridgeport mill too tall|
Clive - Your comment is interesting for me. I appreciate that a horizontal attachment for milling will have limited use, but do the same negatives apply to the stand alone right-angle head if you light mill with cutters up to 10mm? I am considering the Vertex one at some £350 because I have had a need to drill into jobs that are quite long/thin, when clamping horizontally will be best. Anyone have a view on the quality of these heads? they are a bit cheaper than the US imported ones.
I did not appreciate that the drawbar attachment might/will be different? Never mind as I can pull mine out.
Chris 3 - tramming is a lot easier if you make a twin dial head; it has been discussed here a little while ago.
|Thread: TIG welding|
Geoff - Like you I wanted to build a smidgeon of ability with TIG. For me it all goes well down to 1mm thickness then you need to start using heat sinks to stop the holes! My limit was 0.7mm thick stainless, and that was not pretty. I then wanted to repair rusty motorcycle mudguards and just failed using TIG. But, I went back to the cheaper MIG and was able to fill holes, build seams and so on. Several hours later with the grinder and the mudguards were strong and ready for the filling/painting stage.
Muzzer - thanks for the TIG-Sifsilcopper suggestion, I was unaware of that. I had read that TIG-Sifbronze did not work. Sifbronze is actually BRASS (copper/zinc) so a very confusing trade label. But the copper braze might be ideal for repairing rusty cars?
|Thread: Rotary Laser centre finder|
The commercial one I have has the trade name SDA on the side and is made by a firm at lasercenteredgefinder.com - a few UK companies were selling them.
With its polarising cap to reduce the spot to its smallest, and projecting over a useful 12", I estimate the spot diameter to be 0.008" at most, by traversing it across a line and noting the mill DRO. I usually recon to position it on a scribed cross to around +/- 0.002". Similarly you can quickly find an edge, with the spot half on and half off, to +/-0.002". With effort perhaps that precision can be +/- 0.001" and I think the manufacturers suggest that, but the limit is calibrating it on the centre line in its holder; i.e. when rotation causes no deviation. Mine has not moved out of alignment after a couple of years use and a battery change, so it has been good.
I often use an electronic edge finder in preference, but the laser pointer can be very handy for fixing a coordinate on certain jobs.
|Thread: Gunmetal castings|
The lead embrittlement is interesting to note. LG2 also contains around 5% zinc, whereas the phosphor bronzes PB1 and PB102 do not have any zinc present. Would anyone give their view, or refer to study, on whether the zinc content is beneficial or detrimental when it comes to steam engine parts?
|Thread: identifying brass from bronze|
A year ago, I spent some time researching bronze composition when I found there was little written about the subject. At the risk of criticism for errors I offer the table below. I gathered the information by searching the web for many worldwide manufacturers/suppliers, and came up with this. Please note that some suppliers may vary the composition by several percentage points, and there is potential for the use of added nickel in some bronzes.
The true phosphor bronzes are PB1 and PB102; although Colphos 90 contains phosphorous the addition of lead and zinc makes it quite different from PB102. People call bearing bronzes phosphor bronze, which I think is wrong.
For beginners in bronze I would stress the use of PB102 for anything attached to a steam boiler. There is a thought that the zinc in other bronzes could be leached out (as with brass) leading to a weakness, but I have not read of any proof of this. It was this issue that caused me to look at the compositions when I realised that some of our suppliers were not fully clued up on the subject.
Having said the above about suitability with steam, I presume that bronze castings are a simple gun metal and its use in cylinder castings works without problems. Colphos 90 and SAE 660 are regarded as bearing bronzes and you can see that their composition is similar. I understand that the aluminium bronzes are potentially hard, have come about from aerospace technology and are probably best avoided by us.
LG2, PB102, SAE660 and Colphos 90 are commonly available. PB102 machines ok and silver solders nicely, but it can be fussy about drilling and is difficult to ream. Colphos 90 and SAE 660 will also silver solder well and are that bit easier (softer) when machining.
|Thread: Vintage motorbike|
Well, I'm intrigued by just how many ME people on this forum have motorcycles in their past or current blood.
I know some motorcyclists, and perhaps 30% would be interested in a lathe. I know the people from my local SME and perhaps 30% had a motorcycle at some time.
What causes some of us to progress from motorcycles to proper machines with coal and steam in them?
|Thread: an anyone help with drawing for stania black 5|
Ron, the Don Young 5" Black 5 drawings are only available from Reeves; go to their website. I am not aware that there are any other 5" drawings available anywhere else.
|Thread: protecting from rust|
Just to add a thought to the desiccant vs. refrigerant discussion - I had a desiccant unit in my workshop for two years and it worked well; the background few hundred watts of heat seems to help. Then it all gummed up with stuff contaminating the silica gel and the removal of water stopped. I sent the unit off and they replaced the silica gel cartridge and all worked again, for two years, then guess what… My workshop is pretty clean but the silica gel cartridge is too a good filter.
So that went in the bin and I have had a refrigerant unit working now for fours years and it is just as effective. I note the relative humidity every now and again and measure the condensate coming from the pipe that I have pushed through a wall to the outside. When the workshop temperature drops to 5degC then water removal virtually ceases but, and this is the important bit, the outside air at 0deg is carrying much less moisture and if your workshop heats during the day the dehumidifier will keep the relative humidity low, ready for the next cold night.
At 55% Rh I never see rusting, even on freshly cut metal left out for a week, and a dry workshop atmosphere is much more pleasant on a cold morning.
|Thread: Water guages|
I bought a few sizes (EBay - medical/food supply) and cut thin o-rings. The problem is that the silicon tube wall is around 1.5mm thick and would not go into the fitting. I successfully made it work by stretching a smaller bore, but it was a fiddle. Much easier are the 1mm thick o-rings from Reeves, and they are only about 30p. I used two at each end with a touch of silicon grease. I also agree with the PTFE tape and Foliac (steam seal) solution.
|Thread: Do aliens make this stuff?|
I know it is fun to get excited about hazards, but as engineers (or hobbyists) we shouldn't replace science with sensation. Rik probably has a magnesium alloy and these have been extensively used in high performance engines and aircraft, where weight is a premium, without undue hazard for many years.
Magnesium powder is a very different hazard from solid magnesium alloy. When magnesium is combusting it will react with oxygen, CO2, water and even nitrogen, which is why only a dry sand will extinguish it.
A thin piece shaved off an alloy can be ignited in a hot flame because you have taken it beyond its melting point, but it is difficult to ignite a solid lump because even if one corner is molten the larger portion will take the heat from any combustion. It can be cut with machine tools but grinding is not sensible as the fine dust is the fire hazard. Welding and casting are for experts, but I think it is TIG welded with a normal argon gas shield.
Lots of materials go bang if you make them fine enough or hot enough.
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