By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by allandale

What did you do Today 2018

All Topics | Latest Posts

Search for:  in Thread Title in  
mechman4814/02/2018 00:09:25
avatar
1751 forum posts
309 photos

Completed the swing arms for my Vertical cross engine... see workshop progress thread...

George.

John Haine14/02/2018 08:59:45
1694 forum posts
97 photos
Posted by Muzzer on 13/02/2018 17:54:24:

Most limit switches on pukka machines are "just" microswitches, allbeit decent quaity ones. Possibly a quicker solution - and just as repeatable.

Murray

Not sure about quicker. I've got some precision microswitches embedded in a Euchner limit switch. They are very nice and have a repeatability of 20 microns, but rather delicate. The Euchner device has a very clever plunger system to make sure the switches themselves don't get smashed if the limit isn't sensed properly, but is too big to easily fit on the lathe. I considered using one of the switches but would need to make a housing as well as a protective actuator. And I'd have needed a similar bracket and actuating rod. So in the end it was easier using something I already have, which is reasonably protected against overtravel.

image.jpeg

The silver disc in the middle is a tungsten carbide plate spring-loaded against the underside of the top, which has a couple of mm travel before the spring compresses. Not visible is the 4mm socket for a wander plug, but you can see the plug in the side. On the bottom the steel base has a strong magnet embedded to stick the whole thing down (or on the vertical face of the saddle in the case of the lathe).

Neil Wyatt14/02/2018 10:01:13
avatar
Moderator
12517 forum posts
557 photos
66 articles
Posted by john carruthers on 13/02/2018 08:29:10:

Sunday I unpacked the lathe and a few tools to do one last 'just job' before we move.
A mate bought a camera for his scope, the guys in the states got the adapter wrong so it wouldn't fit.
Bored out the adapter to 3.5"
Now packing tools away again.


monkton camera.jpg

That's a mighty serious looking camera! Any details for AP nerds?

Neil Wyatt14/02/2018 10:08:27
avatar
Moderator
12517 forum posts
557 photos
66 articles
Posted by V8Eng on 13/02/2018 16:23:51:

This might be of interest to some:-

Apparently it is World Radio Day today (13th Feb) and BT has a history page on their website.

Something of an ‘I remember that, or was it really that long ago?’

Linky thing to same:-

**LINK**

Edited By V8Eng on 13/02/2018 16:26:17

I saw radios in the early 70s with the licence gummed inside the case (as a boy I used to help out in the shop and one of the jobs was fitting batteries to customer's radios). I suspect they were bought with the radio and never renewed

Neil

Robin14/02/2018 10:31:14
avatar
173 forum posts

I bought 3 Omron precision switches from that auction site. I beat the poor chap down on the price because I was the only interested party. They do North, South, East and West with 1 um repeatability. I realised that what I actually needed was up down so I had to add an extra lever. Then I realised I would have to remake the entire mill controller and it has all sat on the shelf ever since dont know

j

Mike14/02/2018 10:36:47
avatar
621 forum posts
5 photos

Neil, I recall, from the same era, that you had to have a separate licence for a car radio. I refused to buy one, because we had a licence to cover radios at home, but my mum was horrified that I was breaking the law, and she bought one for me. Until the need for a licence was removed, I got a renewal reminder every year, so had to keep buying them. My late grandfather had the first radio in my home town of Spalding, Lincs, and my mum could remember listening to the BBC's predecessor, Station 2LO. Listeners had to wear earphones, but several people could listen together if the earphones were put in the bottom of a large pudding basin to reflect the sound.

Mick B114/02/2018 16:21:35
297 forum posts
15 photos

Finished a cap/top bearing/gland for the trim valve on the Polish tank engine:-

polish tank trim valve cap 1 small.jpg

Inside and outside threads were total bastard sizes, O/d random in either Metric or Imperial, but both a perfect fit to a 14 TPI thread gauge. Only way to do them was successive cut & try. For the outside thread that meant taking it out of the chuck, because the valve body casting - which was the only practical gauge - weighs 40 or 50 lb; but if you mark the jaw positions on the holding diameter, it'll go back properly pitched-in for the next cut.

The rotation shaft of the valve is a bit bent, so I needed to put a bit of clearance in the 'ole. I thought about trying to straighten it, but the rotor (1 3/4" diameter) has such a big aperture in it to let the water through that I dursn't try to true it up wiv an 'ammer. I think the packing in the gland will probably seal it anyway. Should see the engine puffing up and down the line in a week or two, I'm told.

Muzzer14/02/2018 18:20:34
avatar
2528 forum posts
422 photos

I see you can buy Metrol switches online. Down to 0.5 um if you seriously believe you have a machine that precise. The low cost 5um ones start at about £30.

Lots of Youtube warriors like to claim they "work to tenths (of a thou)" ie 2.5um but studiously avoid actually loading their machines when making any kind of visible measurement. My Shizuoka CNC machine claimed 10um work precision when brand new but that must have required meticulous adjustments of the myriad gibs and ballscrews and a following wind. The original NSK ballscrew factory test reports showed initial accuracy of +/-1-2um, which is pretty impressive. Achieving anywhere near 1um final tolerances requires temperature controlled rooms and machines and eye watering capital expense.

Murray

john carruthers14/02/2018 18:52:24
avatar
515 forum posts
171 photos
>That's a mighty serious looking camera! Any details for AP nerds?<

It's an SBIG STXL-6303E
FW-8G filter wheel and AO-X adaptive optics fitted to an LX2oo 16" at the remote operating obs at Monkton Nature reserve. (the smaller white dome).

**LINK**


 

Edited By john carruthers on 14/02/2018 18:52:56

Edited By john carruthers on 14/02/2018 18:54:35

Robin15/02/2018 10:17:33
avatar
173 forum posts

I have a Roland, wax chopping, desk top mill that I have been hacking. It has microswitches for the limit switches and a dinky co-ordinate display on the Z head.

I have a home command to bounce it off the limit switches and set X, Y and Z. Repeated homing starts off okay for the first few times then it starts to creep.

I expected a bit of plus minus but not a creep. Seriously weird but never more than one click difference from one home to the next on a 5um step.

John Haine15/02/2018 16:53:29
1694 forum posts
97 photos

Have now measured the homing repeatability for my system. Best DTI in mag base holder on lathe bed, homed X axis, placed plunger agains end of X-slide to get convenient reading, then moved slide by a varying distance and for each move re-homed. Photos below show DTI face for 4 separate tries.

dti1.jpg

dti2.jpg

dti3.jpgdti4.jpg

All well within the same 10 micron window, and probably within 5, so I'm quite pleased. Should do the job OK I think. Now to puzzle out how Mach 3 tool offsets work...

mechman4816/02/2018 19:08:33
avatar
1751 forum posts
309 photos

Bought a meter of 5mm od brass tubing, plus a meter of 10mm aluminium rod for stock shelf, not cheap

​George.

roy entwistle16/02/2018 19:55:54
765 forum posts

George Are you sure you didn't buy a metre of each ?

Roy cheeky

martin perman16/02/2018 20:41:57
avatar
1091 forum posts
39 photos

John,

Standard practice on machine tools etc is to fit an industrial version of one of these, http://uk.farnell.com/omron-electronic-components/d3v-16-1c5/microswitch-v3-pin-plunger/dp/8774579?mckv=HXNyRh3W_dc|pcrid|78108377589|&gross_price=true&CATCI=pla-131288271909&CAAGID=14989732149&CMP=KNC-GUK-GEN-SHOPPING-OMRON_ELECTRONIC_COMPONENTS&CAGPSPN=pla&gclid=CjwKCAiAn5rUBRA3EiwAUCWb213hek9Rw9KxL1RpZCpmdbYFTvH2VDBWBPPBxnt41c4BUE5tM8vuIRoCnL8QAvD_BwE&CAWELAID=120173390001364401

it sits at the end of your axis in a fixed position and is operated by a linear cam with a rising edge, I assume your positioning is by encoder, the axis is driven to the home position until the switch is operated and stops the axis and the encoder position is recorded, this then becomes your zero position. Do you have an over run switch in case it misses the home position to shut the drive down.

Martin P

Michael Gilligan17/02/2018 12:56:50
avatar
10585 forum posts
469 photos
Posted by Michael Gilligan on 06/02/2018 20:33:57:

What I did today was well-intentioned but foolish:

[ ... ]

Today, I decided to do my bit to help protect the oceanic wildlife; by shredding the whole of the last three MEW wrappers. [shredding goes to landfill] ...

The shredder jammed solid, and I am still trying to remove the strips of thin plastic that wrapped around, and between, all those cutters. ... The machine looks like a lunatic plumber has run amok with a reel of PTFE tape.

.

What I posted on 06-Feb. was intended as a cautionary tale, rather than a request for advice; but in the spirit of 'completion' ... here are some pictures:

shredder.jpg

shredder gearbox.jpg

shredder_mewwrappers.jpg

.

The first two are just to illustrate that it is a substantial little beast.

The third shows that, as I had surmised, the jam was caused by the thin plastic getting between the cutters.

On disassembly, I had to lever the two cutter units apart ... What you see is the contents of the 'overlap' area, where the cutting takes place.

MichaelG.

Swarf, Mostly!17/02/2018 13:37:25
411 forum posts
41 photos

Not today but two or three days ago - it being a cold and wet afternoon I decided to dismantle some ancient computer hard drives ready for submission to the scrap metal man.

Depending on the particular model, some of these have black synthetic rubber sleeves round steel pillars. One of the drives in this latest batch had such a buffer sleeve but when I tried to remove it I discovered that it had changed with age to a sticky black glutinous consistency that abandoned its sleeve-like shape the moment it was touched. The resulting messy fingers needed copious applications of meths/IPA/surgical spirit/vodka with kitchen roll and I still had to lose most of the clippable part of one thumb nail!!!!!

I post this as a warning to other would-be HDD recyclers. Has anyone else encountered this pitfall? This type of deterioration isn't universal, some sleeves still behave like rubber. I wonder if it is a cause of hard drive failure? The drives I was dismantling had all their gaskets and seals intact until the moment they came 'under the knife' .

While I'm posting this, I'm surprised that there doesn't seem to be any recycling channel for the Neodymium/Iron/Boron magnets. Comments welcome.

Best regards,

Swarf, Mostly!

John Haine17/02/2018 13:49:45
1694 forum posts
97 photos

Martin, those microswitches appear to have no spec for repeatability, they may be fine as limit switches but not for precision homing. These is no encoder, like most smaller CNC systems I'm using stepper motors. The switch only gets activated when homing, during which the axis is moving very slowly. If it doesn't stop it will hit the end of travel but that doesn't have disastrous consequences, it just means you lose datum and have to set up again. The switch itself is designed so that it can accept a few mm over travel and shouldn't be damaged even if it bottoms. When the switch is activated it tells the Mach3 controller which is doing a homing operation and the controller then stops the axis movement and remembers the position as "home". I did consider using precision micro switches but the ones I have are only spec'd at 20 micron repeatability and would need careful mounting and protection.

martin perman17/02/2018 14:09:33
avatar
1091 forum posts
39 photos

John,

That's why I suggested Industrial types, I couldn't find the ones we used for work, why would the switch bottom are you passing over the switch or pushing on the switch.

Martin P

Joseph Noci 117/02/2018 14:16:28
247 forum posts
590 photos

Don't get rid of those magnets!

Wrap each in some foam rubber, with insulation tape around, ie, make a sort of tennis ball size foam ball, wound stiffly with tape. Place a largish Sandwich type plastic bag into another, and place the ball within. Wrap the outer bag over, as you would a sandwich, and place the ball in the Swarf Tray..For steel swarf, it works a treat - just unwrap the outer bag, stretching it inside out, keeping all swarf within, and empty in the Swarf Bucket, and refit the bag, or replace if it has big holes..

The foam keeps the swarf from direct magnet contact, which makes it difficult to remove the swarf otherwise..

On the subject of the rubber gumming up..I have similar issues here at home - I suspect it is salt/humidity due to the proximity to the sea - 50meters from the ocean's edge, but not sure.

All the 'tactile' feel ( maybe a silicon based ) covering on the knobs of my oscilloscope have become sticky and can be squeezed off of the knob, between ones fingers. Ditto the rubberised coating on my Wine Corkscrew, and some pens, as well as the rubberised handle of my Bosch battery drill.....Very odd. First I thought it was maybe my sweaty hands ( can't be oily hands, least not on the 'scope and corkscrew!) , but parts of the drill body that are not in hand contact are even muckier..

Joe

edit - spelling..

Edited By Joseph Noci 1 on 17/02/2018 14:17:40

Edit - Sheesh! more spelling...personal note - engage spell checker before brain in neutral..

Edited By Joseph Noci 1 on 17/02/2018 14:18:54

Muzzer17/02/2018 14:35:05
avatar
2528 forum posts
422 photos

The actual position and accuracy of your home switch plays no significant part in the accuracy of your machine operation unless you plan to remove and replace your part between operations. Bottom line is - if you machine a reference part (start with a circular profile perhaps), how does it measure up? For various reasons, you are unlikely to do very well with a hobby machine conversion (or an old industrial machine, for that matter), no matter what limit switch you fit (lipstick and pigs?). I'd be happy indeed if I managed 10um.

Martin - look at suppliers like Omron for "proper" switches.

Murray

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Email News - Join our newsletter

Love Model Engineering? Sign up to our emails for the latest news and special offers!

Latest Forum Posts
Support Our Partners
Ausee.com.au
Expo Tools July 14
Eccentric Engineering
TRANSWAVE Converters
Sarik
Allendale Electronics
emcomachinetools
Warco
ChesterUK
SPG Tools October Seventeen
Shapiro
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

Visit the Model Engineer
Exhibition website

Model Engineer Exhibition