Spare Parts #12 - Heat Bluing A Set Of Steel Clock Hands
Тәжірибелік нұсқаулар және стиль
Heat Bluing A Set Of Steel Clock Hands, by Clickspring.
In this video I go through the process of bluing a set of steel clock hands.
Heat bluing of small steel parts is a key element of traditional clock and watchmaking. It can transform the appearance of even the most mundane parts, and is also believed to afford the parts a small measure of corrosion resistance.
If you would like to help support the creation of these videos, then head on over to the Clickspring Patreon page: / clickspring
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A very special thank you to patrons Dan Keen, and Rob Shearing.
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You can also help me make these videos by purchasing via the following Amazon Affiliate links:
Cameras used in this video:
Panasonic GH5 - amzn.to/2rEzhh2
Panasonic X920 - amzn.to/2wzxxdT
Tools & Shop Products:
"Hardening, Tempering and Heat Treatment (Workshop Practice Series)" - amzn.to/2KbZo6l
Norton 1-by-2-by-8-Inch Fine/Coarse India Combination Oilstone, Red: amzn.to/2tTEPb0
Kaowool 24" X 12" X 1" 2400 F Ceramic Fiber Insulation: amzn.to/2pfsM3d
Blue Matador Abrasive Paper - amzn.to/2IAFiBT
Saint Gobain (Norton) - 4 Arkansas Stones + case: amzn.to/2HCOAMX
Abbreviated Transcript:
00:17 Generally its presented as 4 steps - Harden the part, Heat temper it to Blue, Polish the surfaces, and then Heat again for a cosmetic blue. But first things first, what is it about heating steel that makes it turn blue?
00:50 When full spectrum light strikes the surface, some is directly reflected by that oxide, and some passes through and is reflected by the underlying metal, and so travels a tiny bit further. The two waveforms are now slightly out of phase, and interact as they leave the upper surface.
01:06 Depending on the thickness of the film, some colors are cancelled, and what we see are those colors that remain. When the film is thin, we see a pale straw color. As the film gets thicker other colors are removed, and color we see gradually shifts from brown through purple to a rich blue.
01:24 This is known as thin film interference; its what causes the rainbow of colors in soap bubbles, and a very similar effect generates those fantastic iridescent colors you can see on some birds and insects.
01:37 In our case if we get everything right, the result is a magical deep blue color on our steel part, that no other process can quite match. And I should also mention that the result is not just a pretty blue color, but also a very reliable proxy for determining temperature, which we use during the tempering process in a moment.
01:55 So with a bit of the science behind the process in hand, we can make a few statements about what factors will affect the quality of the final blue color we're pursuing. For one thing it seems reasonable to expect that a uniform oxide thickness would give a uniform color, so it follows that we'll want to heat the part as uniformly as we can. I've made a dedicated set of bluing tools.
02:31 Any sort of contamination will not only affect
the way the oxide forms, but also the light reflection, so we want the work to be meticulously clean just before we start heating. Hardened steel will take a mirror polish much more readily than a soft steel. So the first step is to harden the work.
03:52 Once finished, that boric acid coating comes off very easily with a little boiling water. Now at the moment, the parts are glass hard, and much too fragile to be safely handled without risking breaking them, so I need to temper that hardness.
04:43 As it happens the temperature we want to temper
the work to, corresponds to the blue oxide color, a little over 300 degrees celcius, which is why you see the steel blued twice - once is for this tempering, and the second time at the very end, is just for the appearance. And you can see with this hour hand, just how sensitive the bluing process is to a temperature differential.
06:38 The final surface finish comes from using diamantine powder on a tin lap. Again with short moves to maintain the flat surfaces.
07:51 It pulls the last of the solvent residue from the surface, and leaves the parts quite clean. And you'll notice that I don't touch the parts with bare hands from here on, until the bluing is finished, to maintain that clean surface.
08:40 If the color has any sort of flaw, like for example you can see that the very tip of this hour hand doesn't quite go fully blue, then the part must be taken back to the previous polishing stage.
09:11 There are also several other factors that can affect the outcome too, beyond what I've mentioned here, including the composition of the steel, the ambient conditions, as well as the nature of the light being used to illuminating the part. All of this can be experimented with to further improve the final result.
Heat Bluing A Set Of Steel Clock Hands, by Clickspring.
Пікірлер: 911
Seeing the metal getting blue is just magic. Amazing work!
@Clickspring
8 жыл бұрын
+johnnyq90 Thanks mate, appreciate you taking the time to watch :)
For not being a channel about physics, you did an EXCELLENT job of explaining thin-film interference to the layman. Can't wait for the next build video!
@Clickspring
8 жыл бұрын
+Brad Reardon ha ha! Thank you Brad! Physics was my favorite subject in school :)
@BradReardon
8 жыл бұрын
+Clickspring since I'm not sure it has been brought up before, what is your background in?
@Clickspring
8 жыл бұрын
+Brad Reardon A bit more info here: www.clickspringprojects.com/about.html
I must have watched this a million times. I can't get over how perfectly you polished those radius. I have spent hours polishing metal punches at work to mirror finishes with horse hair and all types of compounds and stones. Your blueing finishes are stunning and look like they were clear coated.
@Clickspring
8 жыл бұрын
+adam cain Thank you Adam, very much appreciate your encouragement :)
Awesome video. It would be cool to see the some of the heat processes with an IR camera.
@Clickspring
8 жыл бұрын
+Practical Engineering Yes it would, great idea.
@alexanderpolivka6475
6 жыл бұрын
i doubt it would be successful as all the parts are really, really shiny
@ricardomaggiore5518
5 жыл бұрын
Wow! Nice idea!
@neut1121
4 жыл бұрын
i don't see how that is cool
@neilharris2896
4 жыл бұрын
@@Clickspring Please do this?? :)
Another AMAZING video from Clickspring. The level of craftsmanship, the quiet enthusiasm in Chris's narration, the quality of his video production. Little wonder this video has already been viewed over 55 K in just 24 hours with 4,374 likes. But who in their right mind would watch such a video and dislike it? Those 15 people must be crazy.
@Clickspring
8 жыл бұрын
+Mark Fryer Thanks for the encouragement Mark, very much appreciated :)
Damn it Chris, it's the third time I watch all your vids about clockmaking. Stop being that skilled!
@johnellison3030
5 жыл бұрын
Andrea Quadrati Yeah, true ah.
@ft7397
5 жыл бұрын
yeah true and in the beginning it says amateur clockmaking. its more like proffetional
@narcoleptic8982
5 жыл бұрын
I'm on my third as well haha
In 30 years from now, kids will be watching these videos in metal shop class thinking, cool, let’s try this, and it will be just as good then as it is now. These videos are the definition of timeless.
Your voice has an unbelievably soothing quality to it. You should narrate children's stories
@Clickspring
8 жыл бұрын
+Daniel Areson Thank you Daniel, very pleased you're enjoying the videos :)
I'm just going to come out and say it. Chris, I want to personally thank you for making and showing us these outstanding projects/videos. No other artist in the world, with such talent would show anyone, their exact process of working on a piece of art. But you sir, show us, in detail, in DEPTH, what you learn, the best technique you find to do something while working on your projects. It's truly amazing, not only how high quality you videos are, but the quality of your work is. just....AMAZING. I love your videos, and you have an outstanding talent at what you do. I currently, do not have the money nor tools to make things like this, but one day, when I do, I will be using your methods. Again, no other artist would be willing to tell, yet alone SHOW, their process of creating a masterpiece. I thank you for actually teaching and showing us, your ways.
@Clickspring
8 жыл бұрын
+SlowlyLosinIt Very much appreciate your kind words mate, thank you.
YAY! Clickspring Video! , I'm a welder/mechanical engineer by trade and I absolutely love watching these videos! Your a true craftsman!
@Clickspring
8 жыл бұрын
+Kieran Jones Cheers Kieran, very much appreciate your support
What you are seeing here, is not only knowledge, it´s also talent
You would perfectly fit in Switzerland !! At our machining class we had to file an entire C clamp to shape, watching you filling with so much care, our instructors would have like you very much !! Keep the great content coming !!
@453421abcdefg12345
8 жыл бұрын
+Ben's things & thoughts : I think this man is a bit above student level !
@bensthingsthoughts
8 жыл бұрын
He definitely is... That was my point ;)
@Clickspring
8 жыл бұрын
+Ben's things & thoughts Thank you Ben, very high praise indeed! I appreciate you tuning in for each release :)
@TrevorDennis100
5 жыл бұрын
Yes it took me back as well. One of my Apprentice Training sections was called Basic Fitting, in which we had to file a 1" steel cube that fitted into an 1" square hole we filed in 1/2" steel plate. I can't remember what tolerance we were allowed, but I am sure it was way looser than Chris is working to,
Omg i love when these clickspring videos are uploaded!
@radioactivewaste4756
8 жыл бұрын
+wyldeman0O7 yeh but u have to wait for a month b4 the next one comes out :(
@justgonnastay
8 жыл бұрын
Quality takes time.
@darthcookie4096
8 жыл бұрын
+Chris Moore very true
It's such a sad comment on our society that idiots pulling stupid pranks have millions of subscribers, while truly talented content providers like Chris receive only a fraction of that.
Do you know how a little kid feels when you show then a bag of lollies and then tell then they cannot have any? I had that feeling when the video hit the 10 minute mark and I thought, 'the bottle is empty' but I want more, I need more... Wow! Chris, you work is AMAZING!
@Clickspring
8 жыл бұрын
+Frank Acosta Thanks very much Frank, I appreciate you taking the time to tune in for each release :)
The dictionary people should replace "perfection" with Clickspring. what can I say, absolutely clickspring!!!
@Clickspring
8 жыл бұрын
+Paul S. Cheers Paul, very much appreciate your support :)
"yay! new clickspring video!... oh.. i've already watched this through patreon. damn!"
@Clickspring
8 жыл бұрын
+Everfalling Ha ha! More for you soon!
Beautiful parts, beautifully produced video. Why can't the mainstream broadcasters produce programming to this standard? Thanks for sharing.
@Clickspring
8 жыл бұрын
+Mark de Barr Cheers Mark, appreciate your support :)
I'm glad you post videos a few weeks apart. If it was any more frequent, I wouldn't be able to leave the computer. I'm looking forward to seeing the finished clock!
@Clickspring
8 жыл бұрын
+Tom Linsenmeier Cheers Tom! New clock episode out on YT in approx a week :)
Your clockmaking videos make me think I'm watching How Its Made, and I loved that series, and now I like this one!
@Clickspring
8 жыл бұрын
+Jarrod “Cal/Rusty” Ellis Terrific Jarrod, great to have you watching
@JayEllis76
8 жыл бұрын
No problem ^^
Chris your cinematic talent of making your shop feel so much bigger than it is is really amazing. Keep up the good work!
@Clickspring
8 жыл бұрын
+eli douek Cheers Eli, thanks for the support mate :)
that was a great explanation of the effort to blue with heat, I had no idea that level of prep was involved.. Cool
@TrevorDennis100
5 жыл бұрын
Yes, it was most enlightening. I learned to blue small steel parts at the Ford apprentice training school just over 50 years ago, and were not taught half the detail that Chris has shown us. I will be trying the bluing techniques out very soon, and hoping to impresses my buddies at the Menz Shed.
Clickspring videos are always outstanding. How could anyone give one a thumb down?
@Clickspring
8 жыл бұрын
+John Ratko So long as you like 'em John, I'm happy :)
@KowboyUSA
8 жыл бұрын
Clickspring You can be happy, 'cause we love 'em!
Chris, outstanding example of heat bluing! Once again you outdid yourself. Su Amigo Siempre
@Clickspring
8 жыл бұрын
+KillerKane Thank you mate :)
Best explanation of thin film interference I've heard! Amazing video content produced, as always, Chris!
@Clickspring
8 жыл бұрын
+EngineerGunter Cheers Gunter :)
It is always an exciting moment when a new Clickspring video appears. Another great video. Thanks for all the work this must be to create.
@Clickspring
8 жыл бұрын
+Daniel Wahl Cheers Daniel, thanks for being patient :)
I wish there was a way to give your video, and this series, a higher rating than just liking and subscribing. It's special interest, so the subject matter is never going to reach critical mass and become a video phenom. But for people interested in clockwork, machining, science, DIY and others I can't think of, should really know that these videos are of the utmost quality in content, videography, editing, and sound. Absolutely everything is perfect. I mean, he even transcribes the video for the hearing impaired, or if you just want to go to a specific spot! I have shown these videos to many of my friends and all of them comment how impressed they are with the quality. A couple of them now look for things on youtube because of these.
@Clickspring
8 жыл бұрын
+Marvin Rock Terrific to have your support Marvin, and very much appreciate you going the extra mile to share with friends
Your work is unimaginably good
Спасибо вам огромное за ваш труд! Впервые вижу настолько технически грамотное объяснение причин появления цветов побежалости. Продолжайте обязательно!
Your attention to detail is phenomenal. I am envious of that alone, beautiful clock parts not withstanding. Always a great respite in my day when you upload a new segment. Fantastic production value as well. Thanx again
@Clickspring
8 жыл бұрын
+Darren Laberee Cheers Darren, very much appreciate you tuning in :)
Thanks for the mini Science lesson, really interesting. Great video too, Cheers Chris.
10 minutes of total Sunday Relax !!! thank you !!! greetings from Poland :)
@Clickspring
8 жыл бұрын
+DonDomel Cheers! Greetings from Australia :)
Amazing work as always!
I love to see progress made on this project! Part of me wants you to finish so I can go back and watch all the videos in a row, and part of me never wants it to end! Keep up the great work!
@Clickspring
8 жыл бұрын
+Crimson13 6 more episodes to go in this build, and the next project to follow this one is well into development too, so plenty more to come :)
Exquisite. I could watch this meticulous sort of workmanship all day long.
@Clickspring
8 жыл бұрын
+Ralph L. Baer Thanks for watching Ralph
You managed to get what looks to me like a flawless polish on those hands! Really beautiful work, I cant wait to see them doing their job.
A pleasure to watch, as always.
@Clickspring
8 жыл бұрын
+Andrew Rouen Cheers Andrew, thanks for watching :)
@Clickspring
8 жыл бұрын
+zumbazumba1 The shavings are there for heat conduction, so I'm guessing that the alloy composition probably doesn't have a significant effect
Sure beats the heck out of the lousy cold chemical blue from a bottle - beautiful hand work ... softening the edges of the hands was the finest of details! Thanks for sharing these videos - the whole end product is fantastic.
Another excellent tutorial, heat bluing is indeed a "Black Art", at least now the viewers of this video will be able to see just how much effort goes into achieving this. Many thanks for posting this!
@Clickspring
8 жыл бұрын
+Englishman French Ha ha! So true! I appreciate your support EF, cheers
Great to see you back, I've missed watching your fantastic videos. I find them very relaxing to watch. With your attention to detail and producing parts that look like fine jewellery. How could anyone dislike this is beyond me.
@Clickspring
8 жыл бұрын
+TheDutyPaid Thanks very much for watching :)
@chrisstephens6673
8 жыл бұрын
+TheDutyPaid The simple answer is, jealousy.
The man. The myth. The legend. Clickspring has returned!!!
I love that you explained the way the blue appears, with the oxide layer thickness and all that information, very good!
Worth the wait. Thanks Chris, fantastic video as always. Looking forward to the next one.
@Clickspring
8 жыл бұрын
+Nakul Verma Cheers Nakul, another spare parts video out next Sunday
Great video as always. I really enjoyed the explanation of the bluing process and why oxidation reflects the different wavelengths.
i was going through withdrawals not knowing how the clock was coming! awesome videos every time.
@Clickspring
8 жыл бұрын
+j If there should be a long gap again in the future, be assured video making is still happening. Thanks for watching J :)
there's something beautiful about perfectly polished and finished metal. And that blueing looks unreal!
Chris I'm a machinist buy trade and make some cool things but this is next level so glad I found clickspring on utube ,please keep these great videos coming .
@Clickspring
8 жыл бұрын
+Trueenglishgent1 Will do TEG, thanks very much for taking the time to watch :)
So nice to see you back with a new video, Chris. Appreciate showing a do-over of the bluing, too. I often learn more from my mistakes than I do when all goes to plan.
@Clickspring
8 жыл бұрын
+Thomas Utley Cheers Tom, no shortage of do-overs at my place :)
This is just too good. I would watch this all day if I could. Great Video Sir
@Clickspring
8 жыл бұрын
+SmokyFrosty Cheers, thanks for watching :)
When I first saw the clock hands my heart skipped a beat. I love your clock making series!
I love all of his videos for educational and machining is interesting reasons, so I don't want to be reductive of either their value or his work, but I swear I could just listen to him talk for days.
Chris! I've missed you and this series! :O Happy weekend! :D I'm still blown away by how beautifully crisp and precise all the corners and edges of all the parts are. It's immaculate!
Another great video Chris. :) Beautiful result.
Was having a pretty lame morning until this popped up. Thanks
@Clickspring
8 жыл бұрын
+Michael Melton Cheers Michael, very pleased to be part of a better Sunday morning :)
Those hands are absolutely beautiful!
Love your work, great explanation on bluing and hardening.
@Clickspring
8 жыл бұрын
+david macglashan Cheers David, thank you very much for watching
Cant get enough of your videos, have watched all of them. Didn't realize you had a Patreon, just became a patron.
@Clickspring
8 жыл бұрын
+Jensen567 Thank you for the Patreon support, very much appreciated :)
Hi,i think ive watched most of yr vids twice or more,the old techniques you try and wish to achieve is nothing less than amazing,your the type of guy that I'd love to be taught by and work beside as most of us trades people are slowly disappearing and being replaced with the electric mechanical revolution which i think it is a real shame,thankyou for all your hard work and progress and wish you the best for the future.cheers chris
I watch a lot of KZread documentary type of videos (replaces nearly all of my TV watching) and it is rare that I am blown away by something new. Truly impressive mix of knowledge, precision, and camera work. Thank you for making these videos. They are a joy to experience.
@Clickspring
8 жыл бұрын
+Jeremiah Mort Terrific to have you watching Jeremiah :)
Well, time for another Clickspring binge
Didn't know Tubal Cain wrote books. He's a living legend. Learning from the best I see :)
@KosmosHorology
8 жыл бұрын
The author of that book is NOT Tubal Cain on KZread (aka Lyle Peterson). It's an older British man (deceased years ago).
@kagi95
8 жыл бұрын
Kosmos Horology Gotcha!
@mark314158
8 жыл бұрын
+Kosmos Horology That man was the legendary Tom Walshaw who wrote hundreds of articles and books including the Workshop Practice series. I am deeply uneasy about Lyle Peterson adopting the same name. Perhaps it is the American attitude that anything that happens outside the USA "doesn't matter". But it does genuinely cause confusion.
@juanrivero8
8 жыл бұрын
+Kosmos Horology You must forgive our American insularity (and we're not even an island!). But I have a great many of Tom Walshaws's books. Unfortunately there is no trademark on the name; it is a bibllical reference. T.D. Walshaw would have really enjoyed the KZread Model Enineering (not to mention clockmaking) community.
@illmnts
8 жыл бұрын
+mark314158 Tubal Cain is metal worker mentioned in the bible. It's likely a coincidence but it's not like it's an unusual alias for a metalworker to adopt. It's used a lot be Freemasons as well. If you ever see a guy wearing a pin with a stick and two balls on it it's a inside joke for masons.
Hands down the most interesting channel on KZread. Thanks so much, Chris, you've done a fantastic job.
@Clickspring
8 жыл бұрын
+conflagrationTuesday Thanks for your support, much appreciated :)
A new Clickspring video always makes my day! Thanks Chris.
@Clickspring
8 жыл бұрын
+Ian Whittinghill Cheers Ian, appreciate you tuning in mate :)
Listen, you can throw all the science you want at me, this still feels like magic. And I really don't mind that.
Chris - the finished hands look like a rendering. Absolute mirror finish. Great work mate :)
@Clickspring
8 жыл бұрын
+Jess Neal Cheers Jess :)
This is a very special blue tone, it is marvelous!
Every new video you put out Chris just amazes me. I don't know how long you have been doing this sort of work, but you are very skilled at it. Thank you for taking the time and dealing with the hassle of filming to make these videos for us.
@Clickspring
8 жыл бұрын
+The Betrayer Very much appreciate you taking the time to watch :)
remarkable! i love watching these videos. what you make look so easy and flawless is obviously the result of numerous mistakes off-camera. a lot like juggling. no one sees the HOURS of practice these performers invest, only the 30 minute show where they look amazing. i generally thumbs-up your videos before i've even finished watching :-)
@Clickspring
8 жыл бұрын
+KingTesticus Bluing larger parts like this is hugely time consuming, and you are correct this took several attempts to get the desired result. 3 attempts per hand, with still some small imperfections in each. But by then I had had enough, and decided I was happy to live with it :)
The clock is going to be stunning when finished!
that deep blue looks so good it is equally blued everywhere very nice
Between watching Clickspring, Alec Steele and Real Engineering, I dont have time to make anything. all amazing work.
Mr. Perfectionist 👌👌👌👌👌👌
Awesome! Your videos are sooo calming and peaceful :) Please make vids more often, if possible.
always worth the wait thanks again for the watch
I always get excited when I see a new Clickspring video in my sub box. Even at 5am local time. Its just so satisfying to watch this amazing piece of precision come to life.
Thank you for a very clear explanation of the tempering colo(u)rs. I also thank you for the reference to "Tubal Cain" AKA the late and great T.D. Walshaw. I have the book, Workshop Practice #1, and use it frequently. I also recommend to all hobby machinists you look at all the titles. There are about 20 of them and available (amazon.com) today. I have about 5 of them and plan to acquire a few more! Professional machinists know it already, but we amateurs have to start somewhere.
@Clickspring
8 жыл бұрын
+Juan Rivero Thoroughly agree, the Workshop Practice Series of books are excellent. Cheers Juan :)
Missed you and your gogeous videos. Nakul is right : worth the wait... Still amazed by your work and the quality of the editing.
@Clickspring
8 жыл бұрын
+Alain Gaillard Thanks for watching Alain :)
Never ceases to amaze me the number of clever tools and materials that clockmakers have! That cleaning putty looks really neat stuff - I see we can get it in the UK, so I'll maybe try some.
Amazingly beautiful. Much worth the wait.
Very cool Chris
@Clickspring
8 жыл бұрын
+lbcustomknives Cheers Lee :)
Oh dear god this is perfection.
@Clickspring
8 жыл бұрын
+Aleksandar Kospenda Thanks for watching Aleksandar :)
The greatest reward for a job well done is to have it done...
Always looking forward to another video by you, its wonderful to see the process unfold
Love the close up cutting veiws so hipnotic watching these vids😀
Your vids are simply a piece of art!
Love video's like this.... sitting back and watching, and learn at the same time.. great job!
I really missed your videos, you are doing an incredible job, and the attention you pay to details is amazing ! The quality of the video is really impressive too
@Clickspring
8 жыл бұрын
+Vincent Dieleman Cheers Vincent, I appreciate you taking the time to watch
Sodium Bisulphate (sold as pool ph minus) will take the oxides off cleanly.
@Clickspring
7 жыл бұрын
Thanks for the tip, will check it out :)
These videos are like meditation. Moar videos!
seeing every new video pop up of clickspring makes my day always better! Love your videos and explainations!
This channel is great for teaching me all sorts of things I never knew I never knew.
Finally!!!
@TheOherik
8 жыл бұрын
+psychofmse I was worried something had happened, I creeped on everything.
YOUR VOICE IS MORE SOOTHING THAN MORGAN FREEMAN!
@JustinAlexanderBell
8 жыл бұрын
+Sonicbolt Freeman
@BEFEGE
8 жыл бұрын
+Sonicbolt And also, the Australian accent is a icing on the cake
@blkhemi3925
4 жыл бұрын
I just commented that I want a pillow made out of his voice
Incredibly deep colour, amazing!
Extremely well done as always Chris.
I can only imagine how many “Oh S&$t!” moments are behind these videos. You only get this good by screwing up and learning!
that really is my favourite colour
@scorinth
8 жыл бұрын
+Absinthe Agreed. He mentions that no other process can get that color exactly right, and I think that's half the reason I like it so much. It's not something you see every day.
Wow! Your attention to detail is awe inspiring!
A true artist at work. Stunning work.
Horay! I love your videos!
@Clickspring
8 жыл бұрын
+Daniel Warfield Cheers Daniel!
@prdoohan
8 жыл бұрын
+Clickspring Hi Chris, Do you mind if I use a couple of your videos before my classes start to inspire my entry level engineering students? It's great to show them what they are capable of producing if they put in the time and effort. I am a toolmaker myself and recently took a tutoring role at a NZ polytechnic. I've been following you for a little while and really love the way you explain and film/document the processes you use. Cheers Paddy
@Clickspring
8 жыл бұрын
+Patrick Rebecca Doohan Absolutely paddy, please do :)
@prdoohan
8 жыл бұрын
+Clickspring Thanks Chris, its great to break up the monotony of theory classes. The students have a wide range of ability and potential, Even AvE's video of him turning a potato in the lathe came in handy! Cheers and keep up the good work :)