Member postings for brian jones 11

I should correct myself guys, when I said VFD wrt ELS it seemed to cause a veer off topic, I meant that when you went to modern electronics control you could jump through to stepper motors with inherent servo motor control, not using an induction motor for the purpose - perish the thought. I must get into that vid series by Clough42 - will it bring me up to speed

OMG there 37 vids, but many thanx for the tip, always good to lean new stuff

will post my stuff on a dirty cheat going metric on compound slides shortly, waiting for some parts

Wow some serious brainz have gone into this topic

Not so Musky at all. However one wonders whether the old ML7 lady is right for this, given the potential expense and time

Quick google didnt show up any ready made cnc screw machines, maybe not looking in the right place

but my knowledge of cnc world is very limited

Ive seen earlier posts on members having brain crumble over metricating a myford - kit costs £190+ just for the combi slides, as for the gears and new yoke etc plus all that work to select gears etc - you know the drill

So I wondered given the marvels of CNC etc is there a means of reading the chuck speed/position and then translating it to a servo motor that drives the lead screw. So no messing with intermediate gears

go onto to a mars landing - if you have VFD then its a short skip for it to become a servo motor driven chuck - then you can do circular index drilling, and maybe make a hobbing attachment to shape gear blanks of your choice

Its getting a bit Elon Musk here?

Well its what we do in lockdown

btw this was inspired by my recent pass thru the day of my mispent youth on a Ward 7A capstan and training up to be an auto setter on those Herbert monsters - anyone remember

I have an original 4" pratt 3 jaw chuck on my ml7 and I wanted outside jaws. some googling and EB gave me serious headache. there are hundreds of different catalog nos http://www.rotagriponline.com/datasheets/Pratt/PrattChuckSpares.pdf

AFAIK you really need the exact match otherwise the jaws may not fit and be a waste of money given that the asking price for spare is 50% of a new chuck with 2 sets of jaws. Not worth the risk as you cant always try it first with EB sellers.

Yes MP I went out to check I hadnt had a" stoopid boy Pike moment" I dont see any oiling holes in either slide

Doing some more digging there are some synthetic greases on the market which are loaded with PTFE particles specially made for "power screws". I saw this on the lead screws used for x-y tables for DRO milling

FYI the pitch on these is generally 2mm but it can have 4 starts giving a lead of 8mm - impressive precision from EB

I came by some 3ft lengths of 1,5 bsw threaded rod cw full nuts. I had in mind to make a screw press (like a cider press)

then I did some digging and discovered how little force you got for your effort . You could lose up to 70% of force due to friction from the threads, which is why acme threads were invented

Then I thought - its easy to make an acme threaded rod - but what about the nut?

3/8" x 10 tpi LH acme die from a well known supplier (but he doesnt offer the tap to go with it) - cant have punters making their own nuts

Now here's a rare sight 1/2" acme 10 tpi

LH of course from EB £10 2u

sorry its an ML7 with a sML7 cross slide - maybe i can add this to a regular footnote

No one suggested drilling an oil hole in the apron casting above the lead nut then?

come to think of it, all those years i never touched the compound slide lead screws in all the machines i used

Well how do you get into the lead screws of the cross and top slide. There are no oiling holes afaik

O and btw  i dissembled my cross slide and was amazed at the flimsy Mazac nut casting which is significantly worn and the lead screw is covered in nasty black oxydised old grease that hadnt been changed for years - bad news

not impressed

Edited By brian jones 11 on 01/07/2021 18:55:21

Hi all

can any of you suggest from experience the best grease to use on my lead screws. Mo2?

It should preferably be non oxydising or dry out long term and should possess qualities that reduce wear on thread and brass nut.

We all used sae 30 in my day but things have changed Im sure

Andy1 thnx 10^6 your tip got me out of my loop and I created a single tee slot post to clamp the mill. it works a treat I will post some pix as soon as I have got the parts 3/8 unf HT bolt and auto car wheel long nut. Of course I could cheat and use an M8 coach bolt but its not HT and might spring under pressure

but for <£5 it looks good

Well done george, my point entirely. I think 10 A is a bit tight as the start current is likely 16A momentarily, I use a 20A DPDT 3 way (centre off) toggle switch. Its only meant for dead ccts use. It is NOT a cct breaker. Your m/c wouldnt notice the difference when you accidentally switched the c/o while running because the motor centrifugal switch would have disconnected the start winding. However I strongly advise against such fooling around. After all you would drive your automatic car at 70mph and then throw it in reverse. Clowns do it and ruptured gearboxes dramatically

Good show AM

One thing Im going to be sure never to raise on this board, is anything to do with electrics. The armchair opinination Ive seen spouted herein - well life's too short.

your right about DOL as opposed to star delta (and soft start VFD etc)

A little knowledge and a smattering of buzz words = plausible conjecture aka BS

I wish I'd never raised the topic

I recommend the Mod close this thread - preferably delete it

Erm so you had a 2,5mm2 wire connected around your workshop with all your outlets tapped off, protected by a 16A mcb

did you complete the cct and turn it into a ring main? which must complete directly at the dis board

I hope thats the case, or you have a dangerous fire hazard installation. your leccy should know this unless hes a cowboy

your insurance would be invalid

You mean the typical old MEM Motor starter. This has a built in thermal trip on prolonged overload. Early ones didnt have a no volt trip feature and should be changed out as the motor could start up again after a trip = dangerous.

Agreed with your fuse breaking chart - its well established

the current of a 1/2hp motor is ca 3A, so the starting (no load) current should be say 20A and indeed a 13A plug can carry this without blowing for a long time

If you have figures to dispute this pls show source and reputable evidence

for now I am simply quoting the rule of thumb

for those who dont want to spend silly money what c/o switch would you suggest

here I am quote Brooks catalog

http://www.brookcrompton.com/upload/files/products/2227e_1phase_v1.1e.pdf

375kW cap start load current 4A, start current 4,1x load ie 16.4 A so I was being conservative and the 6x probably relates to old designs post war stuff. Its what I was taught as an apprentice

Pls quote sources not just opinions off the top of heads, its not helpful or credible.

Edited By brian jones 11 on 25/06/2021 22:26:19

Wow rule of thumb is that motors use 6x steady current on no load start up. Where did you get your figures. surely this would blow a 13 A fuse

any pix pls

The chamfer spigot comes apart from the mill and just need to be bigger dia to 1.75", perhaps i can silver solder a collar onto it made from a piece of 2" round bar

Ill do a drg and post

Yes thats correct but here where it goes awry.

the circular spigot on the top slide that mates with the hole in the cross slide is 1.75" dia and it a snug fit. the dowel pads 39 and 63 mate with the chamfer spigot on the underside of the top slide - see my pix

the same arrangement applies to the mill BUT its is much smaller at 1.25" dia, so a collar and much longer screws would be required

better still a complet new spigot assy needed see pix above

unless i am missing something

My treasured ML& didnt have its Dewhurst capstan switch. Monster thing can cost £75 used on EB. The roller blades would lose their spring temper and become lose with vibration

The cct meant to confuse those not skilled in the arts is actually very simple, it used a DPDT switch to change the polarity (ie direction) of the starter winding,

It must be a break before make design, in fact i got a 3 position with middle = off in the middle to be safe

So I got a chunky toggle switch rated 15A 250v from EB ca £3.50 and the rest was a bit of nifty wiring. Of course the caveat is dont try and change the state while the motor is moving and energised, it must be completely at rest and switched off first, (same applies to the Dewhurst)

i have a 1/2 horse motor 375W so starting current is ca 10A and it only momentary <1 sec. rest of the time the switch is not passing any current or doing any live switching (which is what wears out the contacts) so its quite a benign duty. just dont get it wet with mistic

Ive hardly ever used mine and have note got round to making a chuck clamp to stop the chuck flying off in reverse