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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: Machining a female MT1 taper
12/05/2021 02:07:44

I've been asked to make a spindle with an internal MT1 taper. I'm pretty sure that I can do it, at last resort by trial and and error with a slender boring tool, but it's a challenge because MT1 is only ~ 9.4 mm at the thin end and about 54mm deep. It'd take a long time and much blue (Stuarts and language) I expect.

Looking for an alternative approach I came across these reamers:

mt1reamers.jpg

The top one is 'roughing' and the other finishing. But I don't know how they are meant to be used. Could I get away with step drilling or boring, then use the rougher to take off the corners and finish with the other? They are cheap Oriental offerings made from carbon, not HS, steel, but it's a one-off in EN1A so maybe it could work.

Has anyone used these tools and can advise? Or any suggestions for other methods?

Robin.

 

 

 

 

Edited By Robin Graham on 12/05/2021 02:17:04

Edited By Robin Graham on 12/05/2021 02:22:13

Thread: First attempt at trepanning.
09/05/2021 22:29:13

Thank you Jason and Nigel for further info. Some more ideas to try - as I have several to do it is worth my time experimenting to get this technique under my belt. Apart from the pleasure of learning something new!

In my first (successful) attempt I went through until I saw a bit of a bulge emerging on the back of the work, then turned it over and took off the bulge with the trepanning tool. I then knocked out the centre piece and finished by boring. I can see that trying to go all the through without a centre support as Nigel suggests would be a surefire recipe for disaster.

Thanks again for all the suggestions , Robin.

09/05/2021 00:08:14

Thanks for replies. I confess that I didn't think this through too well - I just ground a 4mm square bit with enough clearance on the outside edge. As I (sort of) got away with it the first time I thought, pending arrival of a more suitable piece of HSS, I'd try another disc and experiment with speeds and feeds. The tool broke.

I haven't got Mason's book, but Andrew's comment that the tool should be half the width and twice the height (ie 2mm wide by 8mm high) made me think - surely that would foul on the outside edge? So I calculated:

trepanningformula.jpg

 

It seems that for my 100mm hole a 2mm thick by 14mm high tool in that geometry would (just!) clear if I've got it right. Obviously that might not be the optimal tool geometry, it was just to give me a starting point. If any kind soul has a pic of Mason's tool shape to share, that would be interesting.

Hopper - I had to read your point about the notch about six times, but I think the penny has now dropped. Possibly!

Robin.

 

 

 

 

 

 

Edited By Robin Graham on 09/05/2021 00:10:16

Edited By Robin Graham on 09/05/2021 00:11:46

06/05/2021 23:49:53

I have a job which involves making 100mm holes in 150mm x 6mm discs of black plate:

150mmring.jpg

As I have a few to do, and the cutouts would be more useful than a bucket of swarf, I thought I would have ago at making a trepanning tool.

As you can see, it worked - but there is room for improvement.

I made the tool from a piece of 4mm square HSS:

treptool02.jpg

treptool01.jpg

treptool03b.jpg

I locked top and cross slides and fed manually using the saddle handwheel. Spindle speed was 65rpm giving ~20 m/min cutting speed.

What I found was that sometimes the tool chattered with a low grumbling sound, sometimes it squealed, and sometimes it went like a hot knife through butter. The discs were bought off eBay so I don't know how consistent the metal is, but my gut feeling is that the variation in behaviour was more likely to do with my inability to maintain a steady feed - especially as I've never done this before, so was perhaps overly hesitant. Something I've learned about parting off is that hesitancy is not good!

If so, I suppose power feed might be the way - but I have no idea what feed would be appropriate.

Or maybe the tool geometry is wrong. I used 4mm square because I had it - but perhaps that's not rigid enough and I should be using rectangular section, more like parting tool geometry.

Sorry that this is a bit rambling and unfocused - any education about this technique would be most welcome.

Robin.

Thread: Protective film for polished metal.
05/05/2021 00:11:50

Thanks for suggestions.

I had tried clingfilm - I couldn't get it to stick reliably. It is also quite thin at ~ 10μm.

I've used Renaissance wax for metal finishing, and it's good stuff I agree - but not really what I want here. Corrosion isn't the problem, it's a need to protect the work from the scratch demons which seem to inhabit my workshop. Or to put it another way, to protect the work from my sloppy and inconsistent practices.

I have MetalGuard from ARC - it's great for what it's meant for, but it's not what's needed here.

I had thought about painting or spraying with some sort of protective film, but then it has to be removed with a solvent, which would give further scope to the scratch demons.

It sounds like the vinyl transfer tape which Adam suggested might work. I had a look (I wasn't aware of the technology) and have ordered a roll. I went for the brand which had the most negative reviews for the intended purpose - 'not sticky enough'. It won't need it to be in place for more than a few days,

Many thanks to Pete and Adam for offering samples - very much appreciated, but I succumbed to the lure of 'Free delivery: Tomorrow. Order within 14 minutes'. So the stuff should be with me tomorrow - or later today, looking at the clock now.

Robin

Edited By Robin Graham on 05/05/2021 00:13:55

Edited By Robin Graham on 05/05/2021 00:14:43

Edited By Robin Graham on 05/05/2021 00:35:32

Edited By Robin Graham on 05/05/2021 00:50:23

03/05/2021 23:39:44

I've been spending some time polishing brass lately. I would like to be able to protect finished parts (flat surfaces, nothing complicated) pending assembly. I had a look for protective film - the sort of stuff that you peel from metal sheets supplied as polished - but found only industrial-quantity suppliers.

Does anyone know where I could get small quantities? Or are there any suggestions for DIY alternatives? Obviously it's important that the film leaves no discernible residue when peeled off.

Robin.

Thread: Interesting old chisels
01/05/2021 23:59:39

Chris, I doubt that you have created anything like Prussian Blue by sticking a chisel in a lump of lime wood. I think it's more likely that what you are seeing is the result of the reaction of iron with tannins in the wood - the complexes which form can be anywhere from blue to black.

For example, here is a pic of rust treated with 'tannic acid' -

blueirontannate.jpeg

Robin (who was once a chemist).

Thread: Holders to use the obtuse corners of C* inserts.
30/04/2021 23:10:37

Hi Neils. My lathe is of the generic Chinese 12x36 design - there are many variations, but the particular variant I have came from Axminster Tools. You can find a manual which gives some info about the headstock / screwcutting gearbox internals here . In the US Grizzly used to sell a very similar machine, marketed as a gunsmith's lathe - the (rather more detailed) manual for their variant can be found here . The Grizzly headstock spindle and gearbox arrangements appear to be identical to those in my machine, but the threading / power feed box is somewhat different.

[Edit] I had a quick look and it seems the CJ0625 - if that's the one you're looking at- is an entirely different animal, so the above might not be of much use!

If I can help further it might be better to continue discussion by private message, as its a bit off-topic here.

Thanks for the link to the discussion of carbide parting tools on HMEM. Your step parting technique is interesting - as well as the Greenwood tool (which uses 2.2mm Sandvik Coromant inserts I think) I have an ARC tool which uses 3mm GTN inserts, so it could be a useful method for me in some circumstances.

Robin.

 

 

Edited By Robin Graham on 30/04/2021 23:11:42

Edited By Robin Graham on 30/04/2021 23:15:04

Edited By Robin Graham on 30/04/2021 23:18:17

29/04/2021 23:32:15

Thanks all - just what I needed. I have bought inserts from JB (and had excellent service), but didn't think to look there. An order will be winging its way to JB.

Niels - thanks for the link to your ultra-rigid holder. That looks good. Apart from your holder, the thread is informative in general about the use of carbide tooling in a home workshop.

It's sad to hear that Greenwood is closing. I have a KIT-Q-CUT parting tool which I bought from them years ago at a show (remember shows?). It's a wonderful tool - zips its way though pretty much anything.

Robin.

29/04/2021 01:17:06

I have quite a few CCMT/CCGT inserts which are worn or chipped on the 80 degree corners but pristine on the 100 degree. I can't find holders to use the 100 degree corners though - probably not using the right search terms. They must exist!

Can anyone advise?

Robin.

Thread: Machining titanium.
27/04/2021 00:23:13

Thanks for replies - I think my questions have been answered. Neil Lickfold's detailed report on speeds, feed &c is especially useful.

It seems that I shall have to don my bio-hazard gear and crawl under the lathe to inspect the suds sump. I rarely use flood coolant (messy) but it sounds like I should for this task.

 

Posted by SillyOldDuffer on 25/04/2021 10:17:28:

...

Doesn't seem likely Titanium soaked in water coolant would catch fire, but a bucket of sand in the workshop would be sensible, just in case.

What fun. Please report what happens Robin. Although my money is on success, failures are educational too!

Dave

I don't intend to invest in a class D extinguisher, but might run to a tub of finely-powdered salt which might be better than sand in the event of an emergency. Apparently that's what's in the extinguishers - the salt melts and make a crust over the blazing inferno. And presumably sucks out some energy in the latent heat of fusion.

Something in the article Dave linked to confused me at first:

"Use of relatively high speeds of travel. Temperature is less influenced by speed of travel than by cutting speed. Travel speeds should therefore be as high as compatible with efficient working."

I initially read that as the statement of a general principle, which I couldn't understand. On reflection I think it's to do with the low thermal conductivity of titanium. Presumably the high rate of travel just distributes the heat over the work more rapidly than thermal diffusion, and therefore results in lower local temperatures. Is that right?

Mick - I had thought about carbide drills but was put off by the cost. Nearly £50 for a 5mm drill from RS! But Ive found that Zoro list a 5mm Dormer carbide stub drill, which will do me fine, for £5.99. I don't need to drill deeper than 8mm  so I'll probably go that way.

Robin.

Edited By Robin Graham on 27/04/2021 00:25:39

Edited By Robin Graham on 27/04/2021 00:26:11

25/04/2021 00:58:18

This is not the first thread on this forum with the title above I know - I found a discussion dating from 2011 (it ran for four years in fits and starts!) but it doesn't give me the info I want. I think the OP in that thread wasn't specific enough in his question, so I'll try to focus:

I have a piece of 20mm diameter Grade 5 (Ti 6-4) round bar which I want to cut, turn, and drill.

  • Q1. Can this stuff be cut with a 'normal' bandsaw? Mine has a 14tpi bimetal blade with M42 teeth. The blade speed given on the plate is 45/min, but it doesn't say if the 45 is in nanometres, parsecs or somewhere between.
  • Q2. If I use carbide insert tools for the turning, should I go for CCMT or CCGT? Or would I be better off with HSS?
  • Q3. I've looked about for advice on drilling the stuff and the recommendation is solid carbide. But that's from suppliers of industrial tooling. I need to drill three holes. Can I get away with HSS drills?

Any advice would be welcome.

Robin.

Thread: Pins for a knurling tool - how hard should they be?
22/04/2021 22:43:24
Posted by Neil Wyatt on 21/04/2021 16:33:55:

I used an HSS drill shank as a 'temporary spindle' for a knurl, it wore badly!

Make bronze pins

Neil

But aren't the shanks of HSS drills much softer than the business end? I've certainly scored drill shanks when I've not tightened the drill chuck enough. And is bronze really hard/strong enough for this sort of thing? The numbers (hardness / Young's modulus) suggest not. But it's never that simple I suppose. Or maybe the smiley means it's a joke. I don't know - I'm a tyro, you could probably send me to the store for a metric monkey wrench.

I did get eventually get a half-decent knurl with my improvised tool:

knurltrial.jpg

but it's not sharp.

I think I have to make a clamp-type tool. David George has kindly sent me detailed plans for his version - thank you David.

Robin.

21/04/2021 00:36:24

Thanks for replies. I actually have a cheap clamp-type tool, which works OKish in brass, but I've never got the thing to produce clean knurls in steel. I think it's partly to do with the arms being too floppy and partly to do with the difficulty of twiddling the wheel fast enough to get a deep enough cut on the first rotation of the work to give registration on subsequent turns. Minimum speed on my lathe is 65rpm.

I'm looking at better designs for clamp tools, but the reason for my post was that I wanted to make a lash-up push knurler for a job in hand an wasn't sure how hard the pins needed to be. I'm confident that the the lathe bearings are up to it.

I ended up buying a 'single point' diamond wheel from Zoro and, as the consensus was that I didn't need to harden the pin, I lashed up an ugly tool with an untreated silver steel pin:

knurlingtool.jpg

The good news is that the pin seems fine. Bad news is that I can't put enough force on using a QCTP - so I need to make something more in line with the cross slide screw. Or make a proper clamp tool. One lives and learns!

Robin.

18/04/2021 01:55:23

I want to knock up a knurling tool along these lines:

kkmoonknurler.jpg

I have wheels and am reluctant to cough up £18.60 for a tool which I could make from offcuts in an hour or so.

What I don't know is how hard the pins should be - I assume that they should be hardened to some extent, but obviously not to the point of brittleness.

My experience of hardening high carbon steel is limited to making cutting tools. Maybe here I should deliberately not heat for long enough to through-harden?

Any advice woud be welcome.

Robin.

Thread: Replacing a Canon printer with a Brother Laser?
10/04/2021 02:04:03

Having got fed up with inkjets with their insatiable demands for ink and tendencies to clog up if not exercised regularly, I have just bought a Xerox B205 mono laser from printerland .

I've had it for only a couple of days but it seems like a nice machine, and a bit of a bargain at £130 including a 1500 page toner cartridge.

Good things are that it has support for WSD and AirPrint protocols, so should be OK with any recent Microsoft or Apple operating system.

I use Linux and the only bad thing I've found so far is that the Xerox Linux driver is a step or three behind the printer's capabilities. But that can be fixed!

Oh - and it prints, copies and scans well!

Might be worth a look?

Robin

Edited By Robin Graham on 10/04/2021 02:06:06

Edited By Robin Graham on 10/04/2021 02:16:25

Edited By Robin Graham on 10/04/2021 02:32:32

Thread: Call me cynical / Call me thick ... but
07/04/2021 01:49:21
Posted by Michael Gilligan on 06/04/2021 11:05:16:

Someone please explain how the length of a second can be measured more accurately than its definition

**LINK**

https://www.smithsonianmag.com/smart-news/new-atomic-clocks-hone-length-second-180977387/

dont know

I guess the answer lies in the semantics ... and that “Time” is not quite the same thing as our defined method of measuring the second.

MichaelG.

.

Note: I haven’t yet read the published paper ... it may make more sense when I do

Michael - as I suspect you suspect, the author of the Smithsonian mag article is a bit woolly in his thinking and reporting. He somehow seems to suggest that 'the second' is an objective entity which can be measured, but he doesn't make a clear distinction between definition and measurement. His background is in is in biology/ecology, so perhaps that's not surprising.

The article in Nature on which his report is based is certainly interesting, - thanks for drawing attention to it.

Robin

Thread: Can Loctite 638 really be this good?
04/04/2021 00:30:43
So the Posted by not done it yet on 02/04/2021 17:53:06:

A further couple of questions: As I’m not conversant with the action of this extruder, is the ring likely to be pushed further on or off the tube? What is stopping an increased surface area of the tube being utilised?

Hi ndiy. To clarify, here's a sketch,extrudersketch.jpg

 

which maybe I should have posted in the first place! So the 'ring' is being pushed off the tube.

There is no reason in principle why an increased surface area shouldn't be used, but the bloke I'm doing it for is cost conscious and 6mm black plate is cheap.

Anyhow, I have glued the flange (as I shall persist in calling it) in place and it seems rock solid. We won't know until it's tested in use, at which time I shalll report back.

Interestingly (perhaps) soft solder (tin/silver/copper) has roughly the same shear strength as 638 for this type of joint, under lab conditions at least. I discounted that possibility for this job because I was worried that if it failed residues might compromise future silver soldering.

Robin.

 

Edited By Robin Graham on 04/04/2021 00:37:34

Edited By Robin Graham on 04/04/2021 00:52:19

02/04/2021 00:56:51
Posted by Brian Wood on 01/04/2021 12:49:35:

Hello Robin,

I should apologise to you really, I made the classic mistake of not reading the question fully and then answering what I imagined it said ! I wish you well in whatever route you chose to follow and will be interested in the outcome.

Best wishes

Brian

Thanks Brian, but no apology necessary - as MichaelG said we all make mistakes. The internet is a wonderful thing in allowing nearly instantaneous communication with people you've never met, but it brings problems - stuff you'd sort out in an instant in casual conversation over a pint can result in misunderstanding when rendered in casual reading/ writing.

I'll certainly report back - it's an interesting experiment, whichever way it goes.

Hopper - you may well be right! But the bloke who brought it round, with touching faith in my abilities, wants it repaired. It's a bit more complicated than just replacing the tube:

clayextruder.jpg

I'd have to remake the sticking up bit or redesign, which I could do, but at a price.

Ken - I'd be surprised if Henkel would warrant anything for this application. But thanks for the suggestion - good to know that they are amenable to technical questions from small scale users.

Robin

01/04/2021 01:12:55

Thanks for replies.

Brian - I'm sorry if the pic was misleading! I did in fact give an estimate of the force involved (about 5000 N) which would give a shear of roughly 2.8N/mm^2 for this joint - well within Henkel's claimed 25N/mm^2. The reason for my post was that I was surprised by my calculation, and thought that I might have got the decimal point in the wrong place, or that the Henkel number was under lab conditions and someone with real world experience would say I should derate that by a factor of 100 maybe. It seems not.

Encouraged by anecdotal evidence and MichaelG's bold prediction that 638 (I assume that 338 was a typo Michael?) I'll give it a go and report back. The worst that can happen is that it fails and I have to resort to 'brazing' - I take your point Mike - or welding.

Some interesting (to me at least) things I learned in my researches for this job are:

  • If I soldered with Silver Flo 55 the joint would (theoretically) be good for 25 tonnes - the tube would burst first.
  • Epoxy resins (including JB weld) are weaker in shear than cyanoacrylates .
  • There is a significant difference between the tensile and compressive strengths on a joint of this type. In this case it's tensile, which is weaker than a compressive joint. But Henkel specify 25N/mm^2 tensile, so it might work!

Robin

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