Here is a list of all the postings Andy Carlson has made in our forums. Click on a thread name to jump to the thread.
|Thread: Multimeter recommendations|
I was looking at buying a new multimeter myself recently. My 30 year old analog one (Maplin own brand) is still working but accuracy is pretty suspect. The rotary switch is a recurring cause of problems on this and many other meters. I've had mine apart for cleaning on at least one occasion... and need to do it again.
Personally I found the Fluke vs china cheapie question left me thinking that I was really missing something in between these extremes - surely Fluke is not the only decent brand?
I found this article helped to shed some light on the 'middle ground' more than most. It's US based though but some of the brands are readily available on our side of the pond.
I haven't made a decision and the circumstances that prompted the question have now passed so my purchase has been pushed down the priority pile.
... and yes an analog one is nice when you want to look at a moving value... and yes a cheap one is good for use where you don't want to risk damaging your nice one... plus there are circumstances when having two meters on the job can be very useful.
Edited By Andy Carlson on 09/09/2021 08:45:49
|Thread: Stringer EW lathe|
Most people do gears like that but you need several cutters if you want a range of gear tooth counts...
... you could also do it like this ...
|Thread: Corbetts Little Jim Lathe restoration - newbie needs advice|
Sounds like you are progressing in leaps and bounds Andy.
I have made some ally bits of tooling for my lathe and they are fine but I'd be looking for something ferrous for the tailstock clamp if it were me.
The carriage stop is a handy thing and I see you have already discovered why it is a good idea to have a stop screw rather than bumping into the whole stop.
For 'T' nuts I think you need to think about how things will bend and at what points the clamping forces will be applied to the 'T' slots. Having 'T' nuts which occupy most of the height of the slot is a good thing because you have more thread engagement and they are less likely to bend. You may need to make them because the off the peg ones may not fit your slots. Thinking about it the opposite way... the last thing you want would be thin, flattish things that can bend and then try to rip the flanges out of your slots. It's also better if there is a solid block of metal (toolpost etc) directly on top of the slide to oppose any force trying to rip out the slot... not always achievable though.
Your oilers look good. I would not be too stressy about oil feed rate (aka.... I dont know what it should be) - as long as the bearings keep a film of oil they should be OK. My (small) cups do run out during longer cuts but I don't think it's a major problem. I top them up whenever I stop the lathe to check measurements etc.
I like to be sure that I can reach the off switch in an emergency or a lesser panic like a dig-in. On the Faircut I have the NVR on the front of the bench next to the headstock and also have an emergency stop button at the tailstock end.
|Thread: BR Leader class Steam engine|
I've always been fascinated by the Leader ever since reading a few sketchy details about it as a teenager and eventually finding a picture of it in a library book.
More recently I've discovered a couple of other attempts to modernise the breed from Union Pacific in the States... Firstly a prewar steam turbine loco with electric transmission... in what appears outwardly to be a diesel body style. This was a failure but preceded the better known postwar oil burning gas turbines which were successful enough to be made in three incarnations.
The final one was a turbine loco running on pulverised coal. That one was a failure too. Apparently pulverised coal is not good for turbine blades. Who'd have thought?
|Thread: Corbetts Little Jim Lathe restoration - newbie needs advice|
Seems sensible. FWIW I did a quick check on the wall thickness of my worn shells before putting them away again. My first impression was that it was 1/8 in but looking more carefully I think it was less than that - around 2.7 to 2.8mm so not a very convenient number... even allowing for the loss due to wear. YMMV as they say in the States.
Forgot to say...
Motor bearing lubricant... can be oil or grease depending on the motor. Of the three I've opened up the ball bearing one uses grease and the plain bearing ones use oil.
... which probably doesn't help much.
If the oilite bearings are not expensive then I think I'd be tempted to get hold of some and experiment a bit. You can always bug out and put the old shells back in.
Have you figured out how the off the shelf bushes compare on OD to your old shells?
If it were me then my first strategy would be to forget that they are oilite and try to reproduce the old shells as closely as possible - i.e. cut the slot and drill the oil hole. Personally I don't see much of an issue with using them as a replacement for solid PB or gunmetal bearing shells. If it's going to need a lot of accurate machining then it's probably best postponed but I don't see any harm in finding out.
Sounds like you do indeed have some bearing play.
I have a spindle and bearing shells from a high mileage scrapped Faircut lathe stashed away so I decided to dig them out and do some measurements. Your spindle and bearings may have a different design but this should give you a few ideas...
One thing that I had not thought of previously... the front end of the spindle bearing area protrudes by a few mm from the bearing. This part of the spindle surface is unworn so it provides a way to get the original diameter. There is also a smaller ridge inside the rear end of the front bearing shell but this is less useful.
As expected, getting repeatable and reliable measurements inside the bearing shells is difficult without any proper internal measurement kit. It's possible to get some measurements with calipers but inevitably they will be wrong. I was able to detect some degree of ovalness in the front bearing shell.
I think the best approach is to figure out the nominal diameter of each bearing and work from there. You should be able to get an accurate idea how much diameter has been lost from the spindle. For the bearing shells... a not very accurate idea.
My front bearing has a nominal diameter of 1 1/8 ins (28.575mm) and the rear one 3/4 ins (19.05mm).
I dont have a 1-2 ins mike so can only use calipers on the front bearing.
On the rear bearing I got 19.00mm on the shaft with the calipers and 18.99mm with the mike. I got 19.10-19.14 using calipers inside the bearing.
The wear on the rear bearing is numerically less severe... but that's the one where the bearing housing snapped and resulted in the lathe being scrapped. The failure is due to the smaller amount of material in the rear bearing housing along with weaknesses arising from the oil holes (modified to take bigger oilers in this case) and any imperfections in the (not very brilliant) casting. Basically you can't predict the point at which the casting will fail but if it happens it's pretty much 'game over'... so tread carefully.
If you want to go down the oilite route then you should be able to figure out which ID to buy. Likely you will have some work to do to match up the OD. You will also need to figure out a way to provide any thrust flanges that exist on the originals. This approach would eliminate the bearing shell wear but you'd still have the lost diameter on the spindle itself.
The saga of my Cowells GEC motor bearings may help https://www.model-engineer.co.uk/forums/postings.asp?th=138249&p=1
Another option would be to get hold of some bearing material (there are whole threads on this topic - I decided on LG2 for my cross slide nuts) from M-Machine or elsewhere and machine new bearing shells. Buying hollow bar would be less wasteful than solid. You could make these undersize on the ID to compensate for the wear on the spindle. Measurement will still be a challenge. I did this by making my own plug gauges. As well as the required diameter, the gauges have a taper or a set of steps with slightly smaller diameters so that I know when I am getting close to size.
... but I still think that the bearing play is not the cause of any bad finish when turning so close to the tailstock centre. I'd put any work on the bearings some way down the queue until you have more experience of lathework.
To answer your question about runout, 2 or 3 thou measured near to the chuck jaws on the OD of a bar held in the chuck is pretty average for a 3 jaw but it could be a lot more with an old chuck. You'll probably get a different answer with a different diameter workpiece because you will be at a different place on your chuck scroll.
Moving further along the bed and with a bar held only by the chuck... anything could happen due to the jaws being out of true. It will probably run out more but it could even run true at some point along its length.
If the job moves when you lean on it then I'd suspect bell mouthed chuck jaws before wondering about play in the bearings.
I'm not sure where you had the clock gauge on the backplate. If it was on the OD then that's pretty unimportant. If you took the chuck off the backplate and clocked the OD of the register then a few thou of runout is not ideal because this will be added to any error in the chuck itself. Thinking about fixing an inaccuracy in the backplate would probably not be a good idea until you have gained some more experience though.
I can't see how far away your work area is from the chuck but I'd say that being so close to the tailstock the finish is telling you very little about the state of your bearings or chuck. The tailstock is providing most of the support here, so the potential causes are the tool, workpiece material, the support of the job (i.e. the tailstock in this case) and the rigidity of the tool holding and everything beneath it.
The HSS tool doesnt look terrible - a bit sharp though - you should very slightly round off the corner of the cutting edge which will make it last longer and probably cut better. Check that the tool is exactly on centre height. If it's EN1A from a trustworthy source then that should be OK too. Check that your toolpost can't wobble in any direction (play in feed screws can be a cause), lock everything that doesnt need to move, keep the tailstock barrel 'stick out' to a minimum and nip up the tailstock barrel clamp (but no need to go mad).
I'd avoid power feeding TBH - most of these lathes don't have a fine enough feed to give you a nice finish - that's why you sometimes see some quite Heath Robinson fine feed contraptions attached to them. Another observation I'd make is that if you want a very smooth finish then you'd be better off with a round nosed turning tool rather than a general purpose pointy one.
Carbide... not something I have much experience with TBH. I use HSS for 99% of my lathe work. I don't think these old lathes will derive any benefit from carbide.
But mainly... keep at it, I don't think your results look too awful and with practice and careful checking of all of the variables your results should improve. You won't get perfection every time though so don't get too stressed over it.
There are loads of reasons for bad finishes - the material and the tool amongst others.
If you want to eliminate the bearings from the equation then take a long piece of bar that will go through the spindle, centre drill it, entend it a long way out of the chuck and turn the OD using a tailstock centre for support.
Bell mouthed chuck jaws are another thing to check for before deciding that your bearings are the problem. TBH most old chucks have this issue to some extent. It comes from being overtightened on short workpieces in the past. Some shim around the workpiece at the outer end of the jaws can compensate for this, albeit that it's a bit of a faff to set it up each time.
Apart from the measurements I mentioned in my previous post you could use your DTI at a point on the spindle close to each bearing in turn. Then you should be able to figure out if the play is coming from one bearing, both or (hopefully) neither.
|Thread: Spikes from Hifi speakers when switching lathe off|
Thanks. It did occur to me that washing machines and tumble dryers are more likely to have the sort of motor that we use for lathes and therefore might offer some useful opportunities for copying or reclamation.
I've never looked into this aspect of any of our previous large appliances. Once pronounced dead, they generally have to be taken away immediately to make room for a new one so I've never had chance to look for potentially salvageable bits.
Thanks Robert. I'm about 90 minutes from Cambridge so hardly local.
TBH I thought when I asked the question that there would be a commonly used and simple answer that I just wasn't finding... after all I've seen plenty of capacitors wired next to switches when I've dismantled old power tools, hoovers and so on in the past and even transplanted one to replace a fried one in some hedge trimmers.
Alas it seems that there isn't a well known answer (like... for 1/4 HP use this capacitor and that resistor) for lathe motors.
I will be seeing a friend of mine who does electrical and electronic design for a living later in the week so I will pick his brains on the subject. In the meantime the popping speakers will continue.
Thanks Noel. I have plenty of experience of mains wiring but I know enough to know that I don't know the answer to this particular question.
... and thanks Robert too. The NVR is indeed double pole.
Thanks for the answers so far. I've found some info on X and Y rated capacitors... So X is line to line (i.e. live to neutral) and is split into X1, X2 and X3 with different spike voltage ratings.
I'm unclear what is meant by 'across the switch' because the NVR has 4 line terminals. Do we mean between the live and neutral output terminals? ... or between the live input and output terminals? I'm guessing the former but I'd rather not guess.
Then there is the question of voltage and capacitance required. Is there a way to figure out what is needed for a 1/4 HP motor? Or maybe copy the ratings chosen by a reputable manufacturer.
We've noticed that we sometimes get an annoying 'pop' from the hifi speakers when the lathe is switched off and less frequently when switching on.
I was thinking that wiring a capacitor across the motor switch might cure this... as well as protecting the switch contacts.
The snag is that I've not been able to fnid much specific advice about this such as...
I've seen plenty of them used on appliances with brushed universal motors but am not 100% sure whether there are any different considerations for a (more powerful) squirrel cage motor.
To be clear... we're talking about switch spike suppression here, not start or run capacitors.
|Thread: Corbetts Little Jim Lathe restoration - newbie needs advice|
Looks like you have made great progress with resolving your issues - excellent ingenuity so well done!
Used DTIs crop up on fleabay from time to time... or...
Given your proven levels of ingenuity you could look at some more old school 'project' ideas and make something to do the job - basically a sprung pointery thing with a very long pointer to magnify any movement. Back in the day there was no fleabay and perhaps not a lot of ex industry clock gauges to be found easily so people had to make their own. You don't need accurate measurements, just a sensitive way to tell if something is runnning out and which side is 'high'. IIRC there was one in a Unimat projects book by Gerald Wingrove... I know you dont have a Unimat but worth a look anyway. You will probably need to join the group but it's free... and then look at the Rex Tingey projects book for some seriously ambitious Unimat projects.
To assess your spindle and bearing wear... you'd need to take it apart again but if it's working then I'd leave it be...
The spindle can easily be measured, preferably with a micrometer. You will probably figure out that the nominal size is a convenient fractional inch measurement. Then you will have a rough idea how much has been lost.
The bearing shells are more tricky but you could use the internal jaws of a caliper to find the smallest and largest diameter. Unlike the spindle, the shells will wear very unevenly. In the case of the bearing nearest to the chuck the wear will happen on the rear and top faces because the cutting forces push the job and spindle backwards and upwards. The caliper likely won't give a great internal reading but comparing the min and max should give you some idea.
Oilite... I'm not so sure that you will find one with the correct internal and external diameter to match the original. They can be turned although this does tend to cover up the pores. To turn the OD you would first need to make a mandrel with a shallow taper on it... time to practice some tailstock offsetting.
My tailstock clamp is a similar design - it's just a small iron casting with 60 degree face and a stud that goes up through the lug on the top part of the tailstock. It's just cast iron on cast iron but it's not really a bearing.
Hmm - that looks pretty terrible trying to squeeze a female thread in where there isn't room. I wonder if maybe someone fitted a larger diameter screw at some point in its history because designing it like that would be shocking.
In terms of repair I think I'd be looking at somethinng with a flange and screws into the face of the casting because you dont want anything forcing that dovetail angle open - it might end badly. Several prewar lathe designs have compound slides pivoting on a single bolt like that and they do crop up for sale from time to time. The heights may differ between lathes though so it might be a bit of a lottery.
Take your time, applying additional coats of thinking is usually a good plan.
No particular thread form is necessary provided that the screw and nut match. Each form has its pros and cons of course but a new thread of any form will work better than what you have now. Plenty of lathes are designed with vee form cross slide screws - the Stringer/EW 2 1/2 inch for example.
Both square and ACME tend to be quite a coarse pitch in order to achieve a sensible thread depth. All types will work... you just need more turns on the handle with a finer pitched thread.
M10 would work but the usual pitch for M10 is 1.5mm which would be less convenient for mental arithmetic when using the lathe. You can get finer pitches (i.e. 1mm) but they are less common (and probably more expensive). It's also 0.5mm bigger diameter than 3/8 inch so you will be losing some wall thickness on your nut... plus it will be 0.25mm more likely to foul the retaining pin. On balance sticking to 3/8 might be better. I've been trying to remember where I saw someone who had metricated their (worn out) cross slide screw but I can't find it now... probably one of the many lathe restoration videos on YouTube.
Can you turn something (anything) yourself ? Maybe... it depends on whether you can get this lathe working at least in a basic way so that it can mend itself. You could perhaps lock the cross slide by tightening the gib screws and then set the compound to 90 degrees and use that to put the cut on... just while you get the cross slide screw fixed up.
Glad you have the nut out.
I'd be a bit cautious - the cutout for the retaining pin has broken through into the bore so you may not have much room to play with if you want to carry on using the pin to secure the new nut.
I'm sure there are plenty of folks on here willing to help once you know for certain what you are going to do with both the nut and the feed screw.
Whereabouts are you located BTW?
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