If you force fabric through the machine while the needle is still going up and down the needle can be pushed out of the vertical and can hit the throat plate.  Result, burrs on the plate and a bent or broken needle.  Don't do it, is my advice!  A hump-jumper is your friend if you're planning those sorts of shenanigans.

Other than that, I switch needles at the end of a big project.  I am not too fussy about needle makes - Schmetz, Organ and the manufacturer-branded ones work for me.  Wouldn't use no-brand needles from Amazon, though, for all the well-known caveat emptor reasons. 

When I take a needle out of the pack to do a small job (eg, taking up a hem on jeans, say), I return it to the pack with the shank turned around so the flat side is outwards.  That way, I know it's been used a bit and if I have another small job to do at a later date, I can use the same one.  I keep empty needle packs (you could use match boxes if you use matches, of course) for old needles so they can be disposed of safely when the pack is full.

I used the technique of moving the dart to the hem and it results in the front hem dipping (at least on my t-shirt it did).  I'd suggest you split the dart into two separate darts and then lose one of them only.  Which one might take some toile-ing to get right, of course.

@AnthonyExmouth - your mum has clearly never read the Discworld novels!

“The reason that the rich were so rich, Vimes reasoned, was because they managed to spend less money.

Take boots, for example. He earned thirty-eight dollars a month plus allowances. A really good pair of leather boots cost fifty dollars. But an affordable pair of boots, which were sort of OK for a season or two and then leaked like hell when the cardboard gave out, cost about ten dollars. Those were the kind of boots Vimes always bought, and wore until the soles were so thin that he could tell where he was in Ankh-Morpork on a foggy night by the feel of the cobbles.

But the thing was that good boots lasted for years and years. A man who could afford fifty dollars had a pair of boots that'd still be keeping his feet dry in ten years' time, while the poor man who could only afford cheap boots would have spent a hundred dollars on boots in the same time and would still have wet feet.

This was the Captain Samuel Vimes 'Boots' theory of socioeconomic unfairness.”

:-)

Second top-loading bobbins - those front-loading ones will do her head in if she's not used to them (she might be but I couldn't get on with them).

I have an electronic machine with more stitches than I use but the handy ones that the old '70s Singer didn't have are stretch zig zag (great for reattaching elastic to underwear, say), stretch straight stitch (good for taking up sweat pants), blind hem (good for hemming curtains - subject to the fabric tolerating it); incremental needle position (good for getting close to the edge when piping, especially when used with an adjustable zipper foot).

Will she be using the machine to take up hems on trousers with flat felled seams (eg, jeans), if so, does the machine have enough heft to get through up to nine layers (count 'em) of denim?  Machines around the £100 mark will have nylon chassis that will flex when they encounter challenges like that - my SiL had one that DB bought sight unseen and it didn't last long!

That brings me onto the next point, which is weight.  Sturdy machines have metal chassis but they bring another problem - if your mum is getting on in years she may struggle to lift a machine, particulary if she's showing signs of spinal degeneration (don't ask me how I know  ) so it might not get much use unless it can be left set up on the work table permanently.

I'd recommend you test-drive some machines and take, eg, multiple layers of denim or canvas to see how the machine copes.  Take some medium-weight fabric and test blind hemming.  Check how heavy they are compared to your mum's current machine.  Check how well it does a straight stitch - you would be amazed how poor some modern machines are at this compared with machines of half a century ago.

So my crochet fox hat is done.  Not up there with fully tailored winter coats but it is the first formal crochet pattern I've followed since I made this in around 1975!

https://www.etsy.com/listing/232829387/crochet-pattern-1970s-waistcoat-laced

Anyway, here is my fairly modest offering - the addition of a tail was my idea :-)

Ooohh!  I'd never heard of this place but its location, bang in the middle of Reading, is an odd choice for a museum of rural life ;-)

Coo!  I've just embarked on a hat for great-niece.  It was in January's Inside Crochet magazine and is made in russet, white and black wool to resemble a fox.  Great feed line for a gag: "We're taking the baby to visit her great granny in Monifieth" "Wear the fox hat"

Arf!

Hello from me too.  I'm from a wee bitty doon the Tay from you but have been dahn sarf for over 4 decades now.