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Member postings for Robin Graham

Here is a list of all the postings Robin Graham has made in our forums. Click on a thread name to jump to the thread.

Thread: Voltage feeding DRO "usb" digital scales?
30/06/2020 23:17:32

Hi Norman. The potential between pins 1 and 4 on my unit is 1.7V. I think that's the supply with pins 2 and 3 clock and data.


Thread: Inherited Lathes and Milling Machines
28/06/2020 22:24:48

Shaun, have a look at - the guy who runs it (Tony Griffiths) is very helpful as about identification/ value of older machines. Ads on his site are paid for, but get a wide audience,


Thread: An internet irony
24/06/2020 22:26:30

I was fishing about tonight - subject was Apple's move to ARM, not that it it matters, and an ad for DuckDuckGo came up. Followed the link and got info about Google's tracking activities. Wondering about how DuckDuckGo makes money I clicked on 'how our business model works'. Screen greyed out and invited me to login into my Google account if I wanted to proceed. Didn't even know that I had such a thing as a Google account!


Thread: EN42J heat treatment
24/06/2020 21:58:37

I've been thinking about using spring steel for knife blades, but I don't know much about the stuff. My local ME supplier stocks EN42J , but searches haven't revealed anything better than 'consult your heat treament specialist'. Has anyone here worked with it?


Thread: sievert gas torch
16/06/2020 23:38:55

I got the same regulator as Geoff shows with a Sievert kit from Hamilton Gas Products (sorry Keith!). The kit came with a 7.7kW 2941 burner:


Worst that happened was was that yellow flames shot out of the air intake slots when I had the regulator pressure set too low. What I do now is open the torch valve fully, crank up the regulator until the flame is nice and roary (but not blowing itself out) then throttle back on the torch valve. Seems to work!


Thread: Ultrasonic toothbrushes
15/06/2020 21:48:56

Thanks Michael. Pretty impressive technology. It looks like Dr Vyas is still working at Birmingham Uni - I may contact her to enquire about the influence of cavitation media. As she works in Dentistry it must be something that they have considered. I'm sure there must be funding opportunities from toothpaste manufacturers!

Dog owners might be interested to hear that the ultrasonic brush/toothpaste combination appears to have worked - the animal is munching happily again. However it's possible that she may have had had a rotten tooth which fell out in the course of nature. Perhaps stimulated by ultrasound - we'll never know.


15/06/2020 20:25:50

Dan - I recently made an ER40 lathe chuck. I bought a couple of 'no name' collets from RDG and one from ARC to suit the work I had in hand. Checking them out in the 'as turned' chuck (so effectively zero runout on the chuck taper) I got better than 0.01 mm TIR at 50mm on all three collets. Maybe I struck lucky - I'll be interested how you fare as at some point I'll be wanting to buy or build up a full set.


Edited By Robin Graham on 15/06/2020 20:26:32

Thread: Ultrasonic toothbrushes
13/06/2020 23:04:59
Posted by Michael Gilligan on 13/06/2020 09:42:13:

I think it’s time to revive this thread:

The Royal Microscopical Society has launched a YouTube channel, and the videos include this ultra high speed video of cavitation bubbles : **LINK**


That's amazing Michael. I see that the work dates from 2015 - have further advances in speed been made since then?

Apart from the astonishing microscopy it's interesting to see how the cavitation pattern changes with distance between the active and 'passive' elements. Maybe I should send these guys a sample of dog toothpaste!

Do you have any references to the original research? Couldn't see anything on the (obviously fledgling) RMS site.


Thread: Questions about lathe power feeds.
13/06/2020 22:30:04

Thanks (belatedly) both.

Jason - I no longer have the manual which came with the machine, which was pretty useless anyway (inaccurate even when comprehensible) but somewhere I have a much better Grizzly manual which JS gave me. Grizzly sold the same machine as a gunsmith lathe. I'll try to dig it out, but I'm pretty sure that there was nothing as exotic as a low helix skew gear in the apron. I suspect that might well be the reason for the difference.

Andrew - thanks for the pic of the M300 threading/feed plate. For comparison this is the threading chart from my machine:


1.1 mm is conspicuous by its absence - C2/M2 would give 1.125 mm which wouldn't have fitted in the box wink

Although the tables only show changing over the 24/48T gears to go between ranges (the change between the 120/127 T idlers is purely to do with clearances) the lathe came with some extra, undocumented, change wheels, so maybe it can play more tunes if I can figure out how to use them.

Interesting that your 3HP machine is power limited - I have never slowed the 2HP motor on mine. Assuming the machines are similar in rigidity (they are similar in weight, but that may not be the same thing) I can push harder.

As I think I said earlier, the reason for trying to clear this stuff up in my mind is that I want to get the best I can out of carbide insert tooling. Surprisingly for me - I'm hard put to remember something that happened 9 minutes ago let alone 9 years - I remembered Andrew's Cambridge Turning Trials . Not very relevant to me at the time as I had only a small benchtop lathe, but I'll be looking at those experiments again now that I have a similarly sized machine.





Edited By Robin Graham on 13/06/2020 22:32:26

Edited By Robin Graham on 13/06/2020 22:33:39

09/06/2020 22:09:25

Thanks for replies to my questions, and also for the interesting general discussion of lathe power feed. The reason I asked is that I am trying to make better use of carbide insert tooling than I have been, and thought I should try to understand the whole business of speeds and feeds better than I do.

It seems that it is normal for surfacing feeds to be slower than sliding feed for a given gearbox setting, but not by as much the factor of five on my machine. I'm glad that there is no suggestion that surfacing is fundamentally different turning - that would have worried me! It seems that it's just fitting gears into the available space.

The comparison with Andrew's M300 was especially interesting as (according to the late John Stevenson who installed the machine for me) the Far Eastern 12x36 lathes are (loosely perhaps) based on the M300. There are clearly big differences though - Andrew's machine has a factor of two rather than five between the sliding and surfacing feeds.

This is the plate on my lathe's headstock:


A somewhat bewildering array of possibilities!

I had a look at the article on the M300 and am now wondering if if the difference is to do with the external gearing between the spindle gearbox and the drive box. On my lathe it looks like this:


That's with a 48T on the output from the spindle box and 24T on the input to the feed box - the upper half of the chart above. The alternative is to reverse them, which slows the feed by a factor of four. Maybe this is something to do with it - it seems different from the arrangement on the M300 as far as I can tell from

It was also interesting to hear that Andrew's lathe is 'power limited' at 3HP (if I remember right - apologies if not). My own machine is 2HP, so even more so, but I've never felt close to slowing the motor. So perhaps I can push harder.


05/06/2020 21:32:11

My lathe (a generic Far Eastern 12x36) has surfacing (X-axis) and sliding (Z-axis) power feeds. According to the plate on the headstock the gearbox allows a range of surfacing speeds from 0.011 to 0.276 mm/rev and sliding feeds from 0.053 to 1.291 mm/rev.

I don't understand why there is a factor of (roughly) five between the two ranges. Is it perhaps a 'feature' of these lathes resulting from economies in the design of the apron gearbox? Or is there an 'engineering' reason why surfacing feed should be so much slower than sliding feed?

If anyone can shed light I'd be grateful.


Edited By Robin Graham on 05/06/2020 21:52:53

Thread: Mains outlets with USB sockets - safety?
25/05/2020 20:51:24

To update on this old thread, today the household power went down. I was a bit confused at first, because when I looked at the consumer unit the MCB's for one of my workshop power circuits, as well as the house power MCB and the RCD for that half of the CU had tripped. I tracked the workshop fault down to the beer soft drinks fridge quickly enough, but after unplugging everything in the house with no joy it took a while for it to dawn on me that it could be one of the integral USB sockets. Which, of course, it turned out to be.

I guess the workshop fridge must have failed earlier in the day without my noticing, taking out only the workshop power MCB, then coincidentally the USB outlet failed later taking out the house power MCB and the RCD.

Anyhow, I don't trust these things now - the one in my daughter's bedroom has started making a high-pitched buzzing noise as well - and shall replace all that I've installed with conventional outlets.


Thread: Yet another parting-off question
20/05/2020 22:05:20

Thanks for replies - it's been an interesting discussion, for me at least. My thanks to all who contributed.

I think that the short answer to my question is given by:

Posted by JasonB on 17/05/2020 11:58:20:

Posted by thaiguzzi on 17/05/2020 10:55:32:

Guys, the OP's lathe is a generic 12x36.

That is Colchester Student/Triumph, Harrison M300 territory.

All the above lathes inc the OP's should comfortably part off 3" OD Ally. And more.

We are not talking flat slideways Myford S7's here.

If i can do it on my weedy Boxford either with HSS or 3mm carbide tips from the front, there is plainly something wrong with the OP's tool, tooling or technique.

The lathe is comfortable with it but the OP is using a tool best suited to a smaller machine and smaller diameters, I note you are using 3mm and probably 26 or 32mm deep which as has been shown will be upto the job and already suggested by others

His question was "can I part 3" with the right tool", answer is that 3" can be parted with the right tool unlike the wrong tool he has, rest is up to him.

Edited By JasonB on 17/05/2020 12:00:40

So I shall buy a 3mm tool and see how I get along with that.

At the moment I don't want to go for a rear toolpost. The lathe doesn't have a slotted cross slide, so some surgery would be involved. It could be done of course, but given the size of lathe I have it seems that I should be able to do this conventionally with the right tooling and technique.

I'm iffy about parting under power - I had a phase of doing that, and it was wonderful when it worked, but catastrophic when it didn't. I like having the manual feedback. I've avoided some catastrophes (not the present one obviously!) by just 'feeling' how the tool is cutting and adjusting feed rate accordingly.

Ketan at ARC - thanks for the link to the previous thread about the parting tools you sell. Interesting reading. I'm sure that I'm not alone in welcoming 'inside info' about the way you test products before marketing - and I accept responsibility entirely for destroying the tool by pushing the NCIH 19-2 beyond your advertised limit. I'll order up a 3mm tool and try to break it.



Edited By Robin Graham on 20/05/2020 22:05:54

17/05/2020 00:21:57

It's a well-worn topic I know, but...

After breaking a couple (or more) tools I have developed some sort of 'feel' for parting - I don't understand things well enough to be confident with power feed, but by hand I can usually tell when the tool isn't happy, withdraw and adjust things.

My weapon of choice is the NCIH 19-2 carbide insert blade from ARC which I've found fine for parting up to two inches in steel, brass and aluminium, although the spec on ARC's site gives 38mm as the maximum diameter for the work.

Today I pushed things even further and tried parting a disc from three inch diameter alumimium bar - the rule marks on the blade give 47mm as the maximum protrusion, so - why not give it a go?

The reason for the (perhaps inevitable) bang was that despite my best efforts to square the tool up, it wandered towards the headstock - when I sawed the piece off it was square for about an inch on radius, but then 'dished'.

My question is - can I part 3" diameter with the right tool and technique, or am I wasting time trying?

Lathe is a generic 12X36 - I lock the saddle so I'm pretty sure that's not the problem.




Edited By Robin Graham on 17/05/2020 00:25:25

Thread: Sort of a Straw Poll
13/05/2020 01:14:55
Posted by Hopper on 12/05/2020 23:36:59:
Posted by Leslie Rix on 12/05/2020
... the purchase of a new lathe and a mill (Chinese likely) to replace my Myford S7 and Dore Westbury mill both in good working order.


If they are in good nick they are likely better machines than some of today's low cost Chinese replacements that are known to have ahem widely varying levels of quality control. Some perform faultlessly for years. Others not so much so.

Maybe the OP wants some 'new toys'? I'm 64 but still haven't outgrown my boyish need to play with stuff. Both old and new. Home engineering isn't always about efficiency I think. Sometimes you just want to have a new toy and play! It's a bloke thing I suppose.

I'm with the majority in saying that the OP should go for it - I, like others bought my first house at 15%, but I worked, payed it off and shall bequeath enough to make my daughter secure. She'd get the sharp side of my tongue if she complained that I was wasting money on my workshop follies though!


Thread: Oscilloscope kits - any recommendations?
13/05/2020 00:02:05

Thanks for replies - too many to respond to individually, but all appreciated and I've followed up on suggestions..

I was asking about 'kits' (in the sense of DIY soldering etc) because I thought they were the only alternatives to 'proper' bench scopes. Much as I'd like a proper scope, I can't justify the cost for what I do.

From the discussion it seems that there is a middle ground - pico etc. But for the mo it seems that the KKmoon offering that Neil recommended will do what I want for not much money.

Duncan - many thanks for your kind offer. Your old pico may well be good enough for what I need to do. I'm typing on an ancient computer with a parallel port! All my ancient computers run Linux though - maybe that would be a problem. I'll PM you.

Les - thanks for your post giving data on the various protocols used by different manufacturers - it should be made a sticky.


09/05/2020 22:11:31

OK, a bit of a 'what lathe should I buy' question I know. It depends on what you want to do...

The reason this has cropped up that I would like to be able to look at the data output from various capacitive DRO scales I have. From what I've been able to discover these are likely to have a 10kHz clock - so I guess I don't need anything too fancy.

I'm pretty much at sea here, so any practical advice would be welcome.


Thread: Cutting down a linear glass DRO encoder
05/05/2020 00:13:30
Posted by Les Jones 1 on 04/05/2020 13:08:28:

Hi Robin,
After reading this thread I have bought one of these scales from Arc Euro.(500mm) I notice from your other thread on the subject that you made an adapter cable. I thought at first that the connector on the scales was a 7 pin DIN but on checking I found the pin layout was different. I assume that you must have found a source for a 7 pin socket to match the scale. Could you please tell me what it is called and where you managed to obtain it. I think I can fit mine to my Seig X3 without having to shorten it.


Les- my adapter cable was a lash-up. I found a 7-pin female DIN socket in my bit-box which fitted the plug on the ARC scale and wired it to a 9-pin D plug to fit my readout following the pinouts Dave gave in my other thread. I wanted be sure it would work before doing any mods. I can confirm that the pinouts and wire colours given in Dave's post are correct for the ARC scales . I ended up cutting the cable and soldering directly to the new plug, but if you want to make a proper adaptor cable it looks like this should mate with the plug on the ARC scales.


Edited By Robin Graham on 05/05/2020 00:29:26

Edited By Robin Graham on 05/05/2020 00:31:52

Edited By Robin Graham on 05/05/2020 00:41:53

04/05/2020 23:39:01

Some measure of success. First attempt wasn't good - this is the test cut-off piece:


I cut the case as near to the glass as I could with a junior hacksaw, then tried to open the kerf with a carbide hacksaw blade (the red bit) with the intention of working round to get the blade flat on the glass and at least make a score line. The grit on the blade was far too coarse and it all broke apart before the blade got to the glass.

On the plus side, (a) if that had been the final cut it wouldn't really have mattered because the read head doesn't get that close to the end, and (b) the glass didn't shatter. On the minus side - well, it's not nice.

Attempt two - this time I cut as before, but went went into the kerf with a diamond wheel on a Dremel type tool , nicked the glass, and with my heart in my mouth and my bowels in my trousers I snapped the end off:




01/05/2020 21:53:08

Thanks Paul, but after taking the read head off and removing the wipers it's clear that the scale is glued along its whole length, so no chance of getting it out.

I too have watched YT videos - at least one person has got away with just chopping through the ali extrusion and glass scale in one go with a standard metal cutting bandsaw. I reckon the blade must have chipped the glass which then broke in the right place. The blade cannot possibly have actually cut the glass. He got lucky I think!

Being a scaredy-cat I've been making experiments on mock-ups and have come to the conclusion that it's probably best done by hand, so I've ordered up some carbide tipped hacksaw blades.

What can possibly go wrong? Watch this space and you'll probably find out....


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