Member postings for Robin Graham

A (possibly final) update on progress with this.

First, thanks for your contribution Neil and apologies for not responding. This project started because a fellow forum member was looking for continuous knurled bar to slice up in much the same way as you have done.Your work looks enviably good.

After some experimentation I managed to make this (at least sort-of) work with the cheapo floppy scissor tool:

Those are details of 250mm lengths.

The pictures are not flattering to either my machining or photography skills - the bars look better in real life - but they do show that the diamond knurls are reasonably crisp and even, and the straight ones are - well, at least straight. And not ragged as in the in photo in my opening post.

I think the main reasons for the improvement were using flood coolant (there were visible amounts of swarf carried away) and not attempting full depth in a single pass. I ended up putting 'a bit of a cut' on at the tailstock end at 200rpm, traversing to the headstock at 0.2mm/rev, then putting 'a bit more cut' on on and reversing to the tailstock. Quite possibly I could have gone faster, but it was working and I'm not on piecework.

The devil in the detail is 'a bit of a cut' perhaps - I don't know what that means, and neither do you .Just what felt right after many trials. Which isn't helpful!

Anyhow, thanks to all for advice.

One day I shall make a Marlco type tool perhaps and see how that goes. I do like a crisp knurl I have to admit.

Robin.

Edited By Robin Graham on 08/02/2022 00:46:49

Edited By Robin Graham on 08/02/2022 00:57:49

I was browsing for rubber tubing (to connect suds pump with through coolant tooling) tonight and ran across The Lab Warehouse. I had nose about their site of course and came across this:

You can get one of these for a mere £812.40. Just thought I should give a heads up on this excellent deal.

Seriously though, would anyone pay that much? I suppose some must, or they wouldn't be selling them.

Robin

Thanks for further advice and anecdotes. To wind this up (I hope) I heard a piercing shriek from the cellars the other day - it was from my wife who had been poking around in search of further evidences. She'd uncovered a nest in the "old tarpaulins, bits of rope and other cr*p I'm to tight to throw away - you never know when it might come in useful" corner of the workshop. Complete with waterlogged ex-rat. Presumably it had gone to meet its maker during or shortly after the deluge.

Since then, and after having plugged holes with a mixture of cement and stainless steel swarf (like razor wire) which I happened to have to hand, there have been no further incursions into the house or any evidences of nefarious activity in the cellars. So maybe it was just the one rat. Touch wood!

A good thing that has come out of this is a resolve to clear out the workshop. Does anyone want 7kg of of miscellaneous wood screws, 10 feet of rusty cast iron pipe (very retro) , six broken clocks, some 1970's speakers, a water bath which only needs some blown triacs replacing, a potentially lethal tube furnace driven by a transformer with naked windings etc etc.

No, I thought not.

Robin

Edited By Robin Graham on 22/01/2022 03:00:23

Edited By Robin Graham on 22/01/2022 03:01:27

Edited By Robin Graham on 22/01/2022 03:05:59

Here you go mate, Burgess bandsaw manual . Took me a full 5 seconds to find that!

I have one:

and it might do what you want, but I've never tried cutting anything as thin as 1mm with it. It's a light enough machine, I can lift it with one arm and I'm not a beefy chap.

Best, IfanJones42

Joe - many thanks for taking the time to explain in detail the two circuits I linked to. My knowledge of practical electronics is rudimentary but I have enough general physics to follow your explanations and I think I now understand how they work. Following your suggestion (sort of) I stuck a 250mm length of self-adhesive copper tape (just because I happen to have a roll and it was easy) to one of the sensor pads, and touching the strip anywhere works fine - despite the layer of adhesive. I'm now pretty confident that I can make this work.

John - thanks for the link to the Adafruit site. Very interesting, but as as Joe guessed I'm not, at the moment anyway, planning to replace the control board, just redistribute the sensors on a new frame. It's a tempting prospect though! My reason for starting this was just curiosity about how these things work.

I'll probably have further questions when I get the animal 'on the slab' to extract the processor.

Robin.

Edited By Robin Graham on 20/01/2022 00:24:33

Thanks for your reply Joe. I knew about the RF oscillator thing, but I doubted that this toy was that sophisticated. I didn't know about the AC hum thing though.

Before posting I did a bit of research and found a circuit which uses a simple voltage divider and a Schmitt trigger. I wondered if that might be the way it worked - it is here . I also found a recipe for an Arduino based sensor here . Both of these are DC as far as I can see.

Can you shed any light on how these work?

Best regards, Robin.

Edited By Robin Graham on 19/01/2022 01:11:55

I have had an unusual request from a 'performer' in my town. She wants to adapt a sort of robotic toy horse for a piece of theatre. If interested you can see the toy horse doing its thing here and an example of the proposed theatre here.

The toy responds to sensors on various parts of its body. These are simply aluminium foil patches connected by single wires to the control board in the body:

I assume that these must be capacitive sensors. For practical purposes it probably doesn't matter too much, as I can just move the sensors to where the client wants in a new framework. But how do they work? Can any of the electronics boffins on here explain?

Robin.

Edited By Robin Graham on 18/01/2022 00:51:43

Thanks for replies - I'm glad I'm not the only one who has had this problem! There is something about a rat invasion which shouts 'Unclean!' and makes me think I should paint a red cross on my front door. Irrational I suppose (pun only noticed on typing).

Some progress has been made, but it's becoming a bit of a nightmare. One of the cellars has stone 'thralls' (the house was a pub in times of yore) around three walls:

These are shelves made from substantial limestone flags mounted on a random limestone base.

The night after the flood my wife made the first positive sighting of one of the little blighters - it disappeared between the flag stone and the base:

and yes, those black bits on the floor are rat droppings.

I don't know how to tackle this yet - I have about 70 metres of loaded shelving resting on the thralls, built in situ, and it would be a big job to strip it all down, take off the flags and see what's in there.

On a positive note, we've bunged up the holes between cellar and house and (so far) there has been no further evidence of intrusion into living quarters. Maybe they can be gently squeezed out without resort to poison or traps. But I worry about what's going on beneath the thralls. Not Lovecraft stuff I hope (the Rats in the Walls).

Thanks for shared experiences and suggestions,

Robin.

Edited By Robin Graham on 14/01/2022 00:51:14

That's a good tale Bill. I'll have a look in the attic. My daughter, who knows about these things, suggests that it's a very small monkey, because two bananas have also gone missing. Peel left in the fruitbowl, nourishing matter neatly abstracted. No fingerprints though.

Robin

A few days ago there was a minor domestic mystery in my house - I had left an opened packet of out of date sausage rolls on a kitchen counter for disposal, and when I saw that they had gone (but packet still in place) I assumed that my wife had chucked them. She assumed that I had. We dismissed it as just one of those things. Maybe the dogs ate them.

Yesterday I got up in the middle of the night (as men of a certain age sometimes do) to find that all the house lights were out. Down to the cellar workshop ( where the consumer unit is), and it was like a steamy tropical rainforest - at first I thought it was smoke and something had blown up.

It turned out that it was a leak in the hot water feed hose to the dishwasher in the kitchen, which is above the cellar. And when I extracted the machine from its housing what did I find? Apart from a strangely punctured hose, sausage rolls!

It's a rat, or rats I reckon. It would be fairly easy for them to get into the cellars, but how into the house? Both stairways are securely closed, but maybe via pipe ducting? This is the gas/electricity feed from the vaulted cellar ceiling to the kitchen:

For scale, that's a 15mm pipe.

First question - do you reckon a rat could get through that? I have no idea - I know mice can get through tiny gaps though.

Second - what to do? My instinct is to get Rentokil or someone in, but my wife reckons that we can discourage it/them without extreme measures. Has anyone had a similar problem and can advise as to likely cost of getting it sorted out by commercial enterprises? Or suggest other strategies? Maybe I just need to buy some sand and cement. I'm OK with mice in the workshop - they don't seem to any harm and have never ventured upstairs - but not rats if they're going to chew though things and get into the house.

Luckily the only machine to have taken a direct hit from the deluge is an ancient Multico morticer, and then only the table - the lovely Hoover motor escaped. One must get priorities right.

Sorry for this rambling post - it's been a long day. If I see that rat, well, I'm going to give it a piece of my mind!

Robin

Thanks for replies, and apologies for not getting back sooner - rich tapestry of life and all that.

I think I've cracked it. I've discovered that I'm not as dependent on cookies for convenient logins &c as I thought - I can use Firefox's 'forget' without any terrible inconvenience.

Perhaps I shouldn't be concerned. I don't know. It's just that I don't understand the technology properly and I'm of a nervous disposition.

Robin

The computer things I mean, not the things that pass for biscuits in some parts of the world.

Some sites refer you to a third party and you can click 'reject all' (excepting 'essential cookies' without which the website can't function) , others give a list of organisations (sometimes 100's of them) who might want to deposit a cookie and you have to refuse each individually, which somewhat vitiates the usefulness of the web as a quick and efficient tool for searching out things one might be interested in. Others present a banner saying 'We use cookies' and invite me to click on a button saying 'I get it' without any other options.. That sounds almost like a threat, and I retreat. But they do say that I can manage this stuff via my browser preferences.

I had a look (Firefox running in Ubuntu) and it seems that I have 1.2GB of disc space occupied by these things. That's a lot of information! Some things are useful ( stored logins mainly ) but most are not.

Is it possible to set up a filter which allows cookies from the three or four sites which I visit regularly without 'breaking' access to the wider web? I can't really understand why some sites claim that they won't work unless they are allowed to stamp their imprint on my disc.

Robin.

Edited By Robin Graham on 02/01/2022 00:36:09

I have DRO's on lathe and mill - luxury on lathe, massive advantage on mill. Not sure that it unsharpens my mind - just saves time.

I do have a belief that doing crossword puzzles gives the 'leetle gray cells' some beneficial exercise though, as well as being fun.

Here's something to cheer those of us stuck in isolation over Christmas with only reading matter for consolation:

Hobby magazine surprisingly redeeming Noel (5,8)

Robin.

Edited By Robin Graham on 23/12/2021 01:56:52

Thanks for further comments.

Clive - your explanation of how knurling actually works and how swarf forms makes sense to me. I think I now understand the process better - thanks.

JasonB/MichaelG - I too had wondered if if it was an 'eye' thing with long straight vs diamond knurls. Despite having vowed not to get distracted from my primary objective of producing straight knurls I succumbed to the temptation of trying my current technique with diamond pattern wheels:

Length of knurl is about 2" so ~8 times wheel width. It's obviously much cleaner than previous examples, but one wheel is cutting deeper than the other - so yet  another mystery to be investigated.

Robin

Edited By Robin Graham on 22/12/2021 00:43:52

Edited By Robin Graham on 22/12/2021 00:57:40

Thanks for replies. One of the ideas I had was that I was going too deep, and as that was reinforced by JasonB's and Tony's comments I had a go with a lighter cut and two passes:

That was going right (tailstock) to left for the first pass, then cranking a quarter turn on the tool before reversing power feed and running back.

Still a long way to go, but a definite improvement.

Another thing I had thought about was the use of flood coolant, which has also been mentioned in comments. Although 'pressure' knurling is regarded a a deformation process, that's clearly not the whole story as significant amounts of swarf are produced. I'm sure that trapped swarf is responsible for some of the deficiencies in the knurl pictured above. Not only does it cause scarring, but I suspect it builds up and deflect the wheel as as well. Flood coolant is the next thing I shall try.

On speeds/feeds, the reason I go so slowly (65 rpm) is that someone somewhere once told me that it was good to go slow and feed hard so that the pattern was well enough established on the first turn of the work to force the wheel to track. My belief (at the moment!) is that the established pattern on the work dominates the 'natural pitch' of the wheel, so the wheel slips to accommodate. But maybe that's wrong? Certainly it seems folk here are going a lot faster and getting good results.

Emgee - the wheels have only a very slight bevel. That's something I could change and shall bear in mind - thank you for pointing that out.

MichaelG - can you unpack your logic (or unpick your intuitions) about the relative difficulties of making long diamond and straight knurls? My intuition was exactly the opposite to yours - but I have no logic. I did look at the Dorian tools, but £s....

I'm unlikely to get back to this in a practical way before the new year (by which time Santa might possibly have dropped a Marlco kit down the chimney, who knows?) - but I'm not giving up on this.

Hope you all have as good a festive season as possible in the circumstances - stay safe!

Robin.

Yes.

Robin

I normally get along OK with knurling, either scissor or bump, but have never needed to produce a knurl longer than about 1.5 times the width of the knurling wheel.

However, in off-forum discussions with another member, the possibility of making continuously knurled bar came up. This is my first (disastrous) attempt:

It's obviously horrible in many ways, but I'm not ready to throw in the towel yet. I have some ideas myself but would be interested to hear any suggestions for improvement. Bar spending £100's on a fancy cut-knurling tool of course!

Some data:

- 1/2" EN3B.

- Cheap and floppy scissor tool with good quality 3/4" diameter x 1/4" width 75 tooth wheels.

- Full depth wound in at start of cut, lathe running at 65rpm, power feed from right to left in the picture at a tedious 0.01mm/rev.

- The periodicity, most evident near the head stock end, is about 1.5 - 2 times the wheel width.

Some of the problems I think I can address but at the moment I don't understand the mechanism behind the tearing of the ridges which results in them becoming whiskers pointing against the direction of tool travel. So that may a place to start understanding what's going on. Or maybe not.

Any advice/discussion would be welcome.

Robin.

-

Edited By Robin Graham on 19/12/2021 00:36:22

Interesting further replies. I perhaps didn't make it clear in my original post that the 'self feed' was severe enough to pull the taper from the tailstock bore, so nipping up the quill wouldn't have helped.

Mike Poole - thanks for your explanation of the relationship between helix rate and rake angle. Now you've pointed that out it seems obvious, but for me it was a wood and trees thing. Drills seemed so complicated I couldn't see it.

John Reese - thanks for the pointer to half round bits. I couldn't find them on MSC's UK site. Drill Service do them, but at £50 a pop that isn't going to happen. Are these like D-bits but with a 118 degree tip rather than a round end?

Since reading replies I have stoned the tips of the rubbishy Screwfix drills (which have been sitting on the shelf for 10+ years ) and now they go though brass like butter. No grab even on break though. Never throw anything away!

I'm OK with quick and dirty for now - it works!

Robin

Brilliant! Thanks to all for replies. As a result of this I think I understand the way drills work better than I did. They have always been a bit of a mystery to me, there are so many angles involved.

By luck (or perhaps I'm developing an instinct?) my 'random swipes' on the Screwfix bit were pretty much as in JasonB's pic and the Clickspring video he embedded. I was wrong to say 'blunting' - I probably actually sharpened the bit, but with a different geometry. I certainly noticed the difference in the chips coming out - more like normal brass turnings.

I had heard of dedicated brass bits and assumed they were terribly expensive, but looking at the slow spiral bits from Tracy tools it seems not. Thanks for the pointer MadMike.

I agree that pilot drilling is, in general, not the way to go. I have found that in steel I'm better off going straight through with the final diameter bit (17mm is the largest I have - used to make space for a boring bar) to avoid snagging. But I was at my wit's end and thought I'd give it a go. I accept that it wasn't a good idea.

The problem is solved I think - thanks again for advice.

Robin.

Edited By Robin Graham on 14/12/2021 23:35:32

I'm sure this has come up before in general, but here is my particular problem.

I work with brass (CZ121) a bit and haven't had any problem drilling small holes (below 6mm) on either the lathe (drill in tailstock chuck), mill, or pillar drill using normal jobber bits. But last night I tried to drill a 9.7mm hole through a 10mm thick brass disc on the lathe in preparation for reaming to 10mm and it was a bit of a nightmare. A 6mm pilot went through OK, but the following 8mm just took off on its own and dragged the chuck from the tailstock. It felt a bit like climb milling when the tool takes charge over the feedscrew.

I was going at 330 rpm.

I ended up digging out a old set of Screwfix drills (useless for drilling steel) and further blunting the cutting edges on the 9.5mm by more or less random swipes with a diamond slip. It actually worked well - beginners luck maybe! And the hole reamed from 9.5 to 10 mm without problems.

I got away with it, but I'd like to know how to do it properly, so any advice would be welcome,

Robin.

Edited By Robin Graham on 14/12/2021 01:58:10