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Member postings for Andy Carlson

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: Spikes from Hifi speakers when switching lathe off
31/07/2021 21:20:28

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.

31/07/2021 17:53:06
Posted by noel shelley on 31/07/2021 17:32:31:

Andy, If you have little or no experience of mains voltage work I would just put up with the click or noise on the speaker ! You could do more harm than good. Noel

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.

31/07/2021 16:54:23

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.

31/07/2021 14:02:45

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...

  • whether it will work
  • what capacitor would suit a 1/4 HP single phase motor
  • whether it will be OK with an NVR switch which switches both live and neutral and where to wire it.

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
22/07/2021 21:17:59

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.

07/07/2021 21:00:40
Posted by Andy Thompson 3 on 07/07/2021 19:22:49:

Andy - a while ago I bolted up the cross slide and used the top slide to turn some wood and a brass ferrule. So I could try again, however this is the thread that keeps on giving. I just checked the top slide thread and eek - see picture.

This is the same 3/8x10 screw but this time the casting is threaded. And the casting is cracked and the threads are nearly gone. I guess I can try the same approach for the topslide, maybe turn down a M6 stud connector and make a new screw.

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.

07/07/2021 17:09:08
Posted by Andy Thompson 3 on 07/07/2021 15:20:38:

Thanks Andy. Not sure the best way to go.

The simplest for me would be get someone to make a nut, I could send them the rod. 10 tpi does sound like quite coarse contol - 3.6 deg for a thou

I like the idea of 20tpi but can the slide be driven by any thread form. I thought square or ACME was necessary.

Could I use an M10 rod. I see GWR have M10 stud connectors - apparently with an OD of 13mm? Perhaps I could file/turn this down to fit 1/2" hole. I think it is still OK to use the pin. Need to drill through with insert in (or maybe mark insert take it out and file a groove. I think the pin penetrated the bore because of my mangling - even if it does then just run a tap through it. Perhaps a grub screw would be better?

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.

07/07/2021 13:28:39
Posted by Andy Thompson 3 on 07/07/2021 13:16:10:

So the sucker is out.

Now - any idea where I could get a nut 3/8 -10 nut made. O.D. from my vernier is 12.8mm. Don't think I need huge accuracy, just something to get me going. The hole is off centre slightly but I think centred would be fine - surely I could just drill the faceplate hole larger if necessary.

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?

07/07/2021 13:18:46

Hi Andy,

I would not suggest that you go down the same route as me - I had a working lathe to make the nut and tap and it was still a lengthy job that took multiple attempts. Square threads are a pain to get right. Hopefully some of my posts will still help you though.

Another option you could consider would be to use a vee thread form. If your feed screw is 3/8 diameter then you could use 3/8 BSF which has 20 TPI so every turn would be 50 thou. That might make it easier/cheaper to source threaded rod - GWR Fasteners do it in mild steel for example. Going metric would expand your options further but you may wish to keep things Imperial.

Some folks have approached this job by making a flanged nut and drilling and tapping a couple of holes on either side of the nut to hold it in place - this will allow you to side step any questions of press fit tolerances and that retaining pin. The downside is that you will lose a little cross slide travel to accommodate the flange thickness.

07/07/2021 08:16:21

Hi Andy,

I've been following this thread over the past couple of days. Looks like you are getting some good advice.

On the subject of the cross slide nut, I replaced the one on my Faircut lathe last year. Mine looks like a very similar design to yours. With the Faircut I did find it necessary to finish the job by tapping in situ.

Mine was a square thread which made life more tricky - I had to do most of the cutting with a single point tool on the lathe and also make my own tap to do the finishing cut. If you don't have a working lathe you will need a different approach to mine but if you intend to replace the feed screw too then you can pick whatever thread you like so that should help.

It was a fairly long job with a lot of uncertainty along the way. The words are on a couple of threads on here...

Good luck!

Thread: Gidday All
11/06/2021 08:56:59

Posted by Damien Fisher 1 on 11/06/2021 00:18:05:

Would a standard MT1 dead Center fit in though? this machine having a shortened tailstock?

I dont know that machine but if they have shortened the thick end then a standard one will stick out too far.

If they have shortened the thin end then the chances are that the bore wont have enough room for it to fit in.

From your pic the I cant quite work out if the thick end is the standard size (should be a little over 12mm) but it is close so likely the thin end is shorter.

It might be possible to cut the thin end off a centre but if it is hardened (which it probably is) then you will need to use a thin grinding wheel (with appropriate precautions).

Do you have a tailstock chuck that fits the lathe?

Thread: Complete newbie
09/06/2021 08:14:01

Hi Alex and welcome to the forum. It's worth browsing and searching some other threads - materials suppliers are a recurring topic. The general advice is to buy material of a known spec that will play nicely on our machinery. I've used M Machine and College Engineering myself and a couple of 'real' engineering suppliers local to me. Macc Model Engineering Supplies have been recommended on here and may be handy for you but I haven't used them myself.

I'd say that the most basic tools that you need are hand tools - a decent bench vice firmly bolted to a decent bench, files, hacksaw and so on. Buy a small number of good quality tools rather than a large number of bad ones.

A lathe will be the minimum that you will need if you want to build steam engines. Again you will find plenty of threads about choosing machine tools and some lively debate on the merits of used British lathes vs Chinese imports. The space you have avaiilable and the size of project that you want to take on will be major considerations.

Start with small projects that you can complete in a day or a few days while your are learning. One of my first projects was a centre height gauge for my Cowells lathe based on the one under 'maiden voyage' here . Easy to make and I use it regularly.

There are indeed model engineering clubs and you will be well advised to join one. I don't know your area so I can't offer any specific suggestions.

Do come back with more specific questions on here... but pleeease try not to ask 'Myford or Mini Lathe'?.

Good luck!

Thread: Celestron Telescope with issues?
08/06/2021 17:01:25

Probably fairly entry level but still capable.

I'd check that the mirrors are in good order before going further - i.e. no bad cracks or chips and the adjusting screws are working.

Fixing the counterweight issues should be plenty doable for a member of a model engineering forum - more so than most prospective purchasers. Mine (not Celestron) has a knurled safety screw at the end of the shaft - this is slightly bigger diameter than the shaft and stops the weights falling off the end even if their clamp screws lose grip.

It will probably need collimnating before use but that is something that you can do yourself without forking out on special kit if you read up on it.

And then try using it... you might find that you enjoy it... although mid June is not the ideal time of year.

Thread: In search of the ‘reverse algorithm’
03/06/2021 22:05:43
Posted by Michael Gilligan on 03/06/2021 00:13:24:

Blender seems to have very good facilities for ‘making’ an isometric camera ...

Blender frequently crops-up in my searches ... when I am trying to find definitive confirmation of my belief that a [physical] technical camera can produce a true isometric image.

I'd have thought that perspective is a fact of life and (to quote Mr Scott) 'You cannae change the laws of physics'. Tilt and shift lenses can distort things but presumably there is a price somewhere else... which may not be be visible if the object is simple, solid and the right shape... but if you take the extreme case of a wireframe... maybe not possible?

To minimise perspective you'd need a long focal length and put the camera far away. With the right camera position it should then be close to isometric.. but never quite reaching it.

Thread: Unimat sl with high tailstock
03/06/2021 08:59:29

The more modern one I was referring to is the 'Basic SL' about which there was a thread on here some time ago. Also a round bar bed but thicker bars than the old SL. Having found it again it's actually less red than I recall - just the tailstock. Apparently refer to it (or a very close cousin) as the 'Unimat PC Basic'. It was news to me at the time.

Hopefully the OP's question has been answered. My guess would be that the headstock and tailstock started out on different lathes.

Thread: In search of the ‘reverse algorithm’
02/06/2021 08:17:28

I've tried something not entirely dissimilar when trying to find dimensions for railway vehicles and buildings that are no longer with us.

My first attempts involved measuring the photo and trying to use trig to determine the unknown dimensions from the one that was least uncertain. I thought it should be simple but I could not make it simple or get it to produce sensible results.

My approach now is to take advantage of the fact that I need to make a drawing anyway and then create a 3d model in whatever tool, export it to STL and then import that to Blender. With Blender I can then guess the relative position of the camera and the subject, guess the focal length of the lens and attempt to reproduce the perspective in the photo. The photo can be imported as a background and I can move the opacity slider to compare the two. The same model can be used to overlay multiple photos from different angles if you have them.

Blender takes time to learn but overlaying a photo onto an existing STL is using a tiny part of its features so you only need to learn those parts.

See below for an example of a building. It's the Steam Packet Inn in Hayle and was demolished in the 1960s.

I have not tried to use isometric projection as an interim step TBH.


Thread: Unimat sl with high tailstock
31/05/2021 18:16:50

Mine is OK... never measured it but have not noticed an issue anyway.

Do you get the same height difference with the tailstock barrel fully retracted as with it fully extended? - just wondering if the tailstock is sitting level or not.

Are we talking the ols Unimat DB/SL here or the more modern (red) thing similar to the 'Unimat PC'

Thread: Strange mini "turret" lathe?
31/05/2021 09:33:22
Posted by Michael Gilligan on 31/05/2021 09:28:41:

Well-spotted, Andy

But what a shocking presentation by the Seller surprise


Yep. My theory is that his logic was... 'I have no idea what this is... so I will pile stuff on top of it, call it a mini lathe and hope that nobody notices'

31/05/2021 09:20:24

Me neither. I did have a punt on this one a week ago but was outbid...

Did anyone else have a look at that one? Some sort of small gear hobbing machine as far as I can see but doesn't look like the Jacobs to me.

Not sure I needed it, but I think everyone likes a hobbing machine... in the same way that everyone likes a shaper.

21/05/2021 23:06:39
Posted by Dave S on 21/05/2021 22:17:55:

SWMBO is quite certain I don't need it...

So you must have asked whether you need it then?

need? - not sure that is relevant

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