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The Offcial Machinist Thread: Revised 01/04/2014

A place to ask general spud cannon related questions.
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Unread postAuthor: DYI » Sat Aug 25, 2012 10:06 pm

Sorry Dewey, you seem to have estimated his situation a lot more accurately than I did :D
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Unread postAuthor: inonickname » Sat Sep 01, 2012 3:08 am

I recently made some of these in half scale (about 20x25mm) as a keyring puzzle. They aren't too hard to machine- though need to be made accurately to function smoothly and look good (and not reveal too much). They can be done on a lathe/mill or even a lathe/drill press if you consider the order you make your cuts in carefully.

They're much, much harder to solve than you would expect. With one ball loaded the process is simple. 2, fairly easy... 3 and 4 gets a bit ridiculous. What makes it so hard is that with more balls loaded you have to unlock it very, very carefully or they have a tendency to relock the mechanism. And that's assuming you know exactly how to do it as you made it :wink:

Drop me a PM if you'd like the plans.

Anyone else have any "fun" machining puzzles or things that can simply be made for shits and giggles?
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Unread postAuthor: jmez1996 » Wed Sep 19, 2012 2:55 am

bought my first lathe last week!
sieg c6
550mm between centres
250mm swing over bed
been great so far. haven't had any trouble with it at all.
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 19, 2012 3:06 am

welcome to the fray :D

You've done well without the benefit of machine tools so far, I expect you'll be churning out even better things now :)
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Unread postAuthor: jmez1996 » Wed Sep 19, 2012 6:41 am

cheers :D yeh i've been practising on some aluminium and steel.
is ali strong enough for airgunning purposes? like valve bodies and things. I have heard its strength can be limiting for some applications... and have found it doesn't produce the neatest threads compared to steel. but steel rusts :?
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Unread postAuthor: inonickname » Wed Sep 19, 2012 9:59 am

jmez1996 wrote:cheers :D yeh i've been practising on some aluminium and steel.
is ali strong enough for airgunning purposes? like valve bodies and things. I have heard its strength can be limiting for some applications... and have found it doesn't produce the neatest threads compared to steel. but steel rusts :?


Depends on the purpose... and the aluminium. Aluminium you get from diy stores is junky, not real tough and is gummy to machine. 7075 properly tempered on the other hand is very respectable. Still depends on the application and how it's designed.

Playing with lubricant, speeds and feeds will yield better results (also, if you're using cheapo aluminium better results will be had with better materials).

To combat the rusting steel you can powdercoat, varnish, blue (rub on cold bluing looks nice done well but needs to be varnished to prevent rust). Obvious alternative is stainless steel. Not as nice to machine and not as cheap but finishes up well and is rust resistant. Beware of work hardening, it's a good way to kill drills.

Are you using carbide or HSS? Carbide should be run hot, fast and with heavy feeds if your lathe and tooling is up to it. Be aware that carbide is bad at taking very light cuts so you need to take that into account when doing your final passes. Also, if you're running the work hot remember that your workpiece will change size and throw out tolerances.

Brass is a reasonable machining material, most grades machine very nicely, are easy on tools, finish up nicely and have fair strength (though, heavier than steel and not as strong). While it's not rust prone it will tarnish.

Stay away from hardened steels until you've got some practice (you definitely want indexable carbides for them too), they put a lot of load on your machine. Right c*nt on cutting tools too. You need a fair bit of power and rigidity to cut them effectively. Run them hot with no lube, the surface where the cut is needs to be hot to reduce the strength of the steel where it's being cut. For hard steels carbides don't really cut it, PCBN bits are really needed. Big $ but can have good life and run quicker than carbides (which run fast and hot as it is)

Titanium is a bit pricey but it's not as bad to machine as people think. If I had a viable source I'd think about making some rings/jewelry. You just need to be aware that it work hardens super quick, and chips ignite pretty easily. If you treat it right it's really not worse than stainless steel.

Hmm what else... copper isn't too bad, a bit gummy. Crappy steels tend to appear torn when cut and aren't fantastic to machine. Getting a feel for what speeds and feeds to use for given materials will come naturally eventually.

Anyway, nice little lathe. Good size too, you shouldn't have many problems with fitting a fair sized workpiece. Not sure how the rigidity and power is on those lathes but you shouldn't have an issue.
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Unread postAuthor: ramses » Wed Sep 19, 2012 11:51 am

I find you can usually get a decent finish with crappy steel if you hog it out with carbide, then use an insanely slow feedrate, large radius, but sharp HSS bit with about zero top rake. The Hogging can technically be done dry. If you don't have flood coolant, it will probably vaporize off.

6061 aluminum machines very easily dry.

I hate machining copper. Milk works well as cutting fluid, but smells aweful as it burns. I ended up using diesel fuel and water. The general consensus is large tool radius, but extremely sharp and about 0 top rake.
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Unread postAuthor: inonickname » Thu Sep 20, 2012 2:21 am

I just use indexable carbide with water soluble oil (special cutting oil) for copper and it works fine.

Generally, if the part I'm doing is unimportant enough to use crappy steel then it's not important enough to need a nice finish.
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Unread postAuthor: jmez1996 » Thu Sep 20, 2012 6:18 am

cheers for the advice inonickname,
yeh i'm using some basic HSS tools to start off but ill get some carbide insert holders later when i know im not going to be destroying them. haven't damaged anything yet :D

i cut some threads on pvc and aluminium using the change gears and made a simple bolt for a motorbike seat pivot from aluminium. i got the ali from a special aluminium dealer and the steel from a special steel dealer but im not too sure what alloy it is.

i might try salt bluing (using saltpetre) or oil bluing on steel coz i have had success with that in the past.

would carbide tip insert holders off ebay be good enough quality? i would like to get knurling tools and other accessories off ebay but i can imagine the precision may be poor
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bolt which acts as an axle for the seat of a motorbike to pivot on when it is opened. lost the original while restoring the bike
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Unread postAuthor: inonickname » Thu Sep 20, 2012 6:50 am

jmez1996 wrote:cheers for the advice inonickname,
yeh i'm using some basic HSS tools to start off but ill get some carbide insert holders later when i know im not going to be destroying them. haven't damaged anything yet :D

i cut some threads on pvc and aluminium using the change gears and made a simple bolt for a motorbike seat pivot from aluminium. i got the ali from a special aluminium dealer and the steel from a special steel dealer but im not too sure what alloy it is.

i might try salt bluing (using saltpetre) or oil bluing on steel coz i have had success with that in the past.

would carbide tip insert holders off ebay be good enough quality? i would like to get knurling tools and other accessories off ebay but i can imagine the precision may be poor


You can just heat the part with a blowtorch. That's probably what you call oil bluing.

Hmm personally I wouldn't, you don't want to skimp on cutting tools. Expect to spend at least $100 for a pack of 10 inserts and $50 for a holder. HSS is still good to have around for making custom tools. I've got a r/h and l/h 16mm holder, boring bar, 16mm internal and external threading tools, and a parting tool in indexable carbide. Pricey tools, but they cut awesome and last. While an insert is expensive it can be used multiple times (rotated) and lasts a very long time. Carbide will even machine HSS.
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Unread postAuthor: jmez1996 » Thu Sep 20, 2012 8:55 am

Okay then fair enough some decent tools will be my next purchase
havn't had any problems with the lathe so far. i havnt been able to get a great finish on steel yet but im sure that will be down to the quality of my tools
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Unread postAuthor: inonickname » Thu Sep 20, 2012 11:05 am

jmez1996 wrote:Okay then fair enough some decent tools will be my next purchase
havn't had any problems with the lathe so far. i havnt been able to get a great finish on steel yet but im sure that will be down to the quality of my tools


Could be the steel too. I've had some steels come up lovely with no effort, and others take a bucketload of sanding or grinding to get a nice finish.
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Unread postAuthor: Crna Legija » Fri Sep 21, 2012 11:26 am

get a clamp on style knurling tool don't think the pushing ones will be very kind to you lathe

edit: do you put a little radius on the end of your hss tool? that help get a better finish.
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Unread postAuthor: inonickname » Fri Sep 21, 2012 7:56 pm

Crna Legija wrote:get a clamp on style knurling tool don't think the pushing ones will be very kind to you lathe

edit: do you put a little radius on the end of your hss tool? that help get a better finish.


Yeah the clamp on styles are a better idea, I use a push style but I've got a very large, rigid lathe.

Knurling takes a bit of practice to do well, but once you figure out how to find the correct diameter it's easy (you can also use trial and error)
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Unread postAuthor: inonickname » Mon Sep 24, 2012 12:57 am

Got asked to machine a part by my (ex) boss today, a collar/support from hardened steel. Simple part, but needed tight tolerances, hard steel and a good surface finish (plus, lots of boring).

After it was done (4 hours) he was wrapped with the job and with how much money he'd saved by not getting it air freighted (would have been a $600 expense total). Told me he'd put it through the books as 5 hours work on my old rate (just regular work not machining stuff, $20 or so an hour after tax) to do me a favor. :lol:

I told him that no, he wouldn't.

Hmm, materials supplied (hardened steel), 4 hours hard machining, for $100? Seemed to think he'd stumbled upon the worlds cheapest machine shop :lol:
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