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Author Topic: Lathes and stuff  (Read 20985 times)

xyzer

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Re: Lathes and stuff
« Reply #15 on: May 30, 2009, 05:36:17 AM »
Carbide needs 3-4 times the surface feet and a good feed rate. If you use carbide the same as high speed you won't be happy. Diamond inserts can really be spun up with a red chip. There are many grades of carbide designed for hardened dies to cast iron. At work we use all carbide on old beater machines to big new heavy CNC turning centers. I use carbide at home on a cheap Taiwan import no problem. I'll never go back........
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mobile_bob

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Re: Lathes and stuff
« Reply #16 on: May 30, 2009, 06:01:44 AM »
nobody asked but i will throw in my .02 worth :)

automotive machine tools are very specialized and developed to fit a specific need that is going to be near impossible to
replicate with either a lathe or a milling machine.

not saying it can't be done, but the results are seldom as good as a purpose built machine can accomplish in a fraction of the
time.

for instance

cranks are almost never turned in a lathe, most always ground in a crank grinder
while you can turn a crank in theory in a lathe, it is very difficult to get the fillet done correctly
and that is a very necessary element of a crank journal.

cylinder boring machines have much finer feed rates that most all lathes, it is this fine feed rate that imparts
a finish that doesn't take forever to hone into proper condition to accept piston rings.

there is more, and if you wanna get into the nitty gritty go to a machinist forum and ask around
practicalmachinist.com has had various discussions on this very topic.

btw,, you guys think this place can be rough at times, that place makes this place look like a preschool playground
so be advised you better know your crap before you call anyone out over there,, they are very good with newbies
but very aggressive when it comes to bullcrap..  and they absolutely will not tolerate discussion of chinese import machines.

other than that a weath of machinist info over there.

also

southbends book, "how to run a lathe" is about the best book on the subject for the newbie getting started
copies are commonly available on ebay and other sources.

bob g
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mobile_bob

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Re: Lathes and stuff
« Reply #17 on: May 30, 2009, 06:06:32 AM »
also you might have a go at that cylinder with a bead hone and see how it ends up
even if it has little pits it likely would be ok to run

might also have a go with some emery cloth and light oil on the crank journal and see how it turns out.

you might find it to is usable?

bob g
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(useful forums), utterpower.com for all sorts of diy info

xyzer

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Re: Lathes and stuff
« Reply #18 on: May 30, 2009, 07:12:51 AM »
Jens,
I also have blanks and the "I'll never go back" statement should have been "I'll never go back! Only if I have to"  ;D
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GuyFawkes

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Re: Lathes and stuff
« Reply #19 on: May 30, 2009, 11:02:20 AM »
It looks like I've scored a nice Harrison L5A lathe from the workshop next door, for reasonble money (they only use it for winding reels of welding wire!) - so now I'm looking forward to getting into a whole world of machining ;D

First job will be to do something with my extremely dodgy exhaust system which is currently held together with an oily rag... but I'm hoping I'll be able to use it to renovate the bore & crankshaft on my 2nd engine (both are rusty), and I'll probably need to machine an entire new shaft for the startomatic alternator, as the current shaft is badly bent.

Also, as it's a fairly old machine ('50s to '60s vintage), I'm hoping I can cut Whitworth screws/nuts with it, if needs be...

So... I'm looking for a good "learn to lathe" resource - any recommendations from the panel?

come into this late, and been busy elsewhere...

basically a lathe is a machine that rotates the work while keeping the tool fixed, and basically a mill is a machine that rotates the tool while keeping the work fixed.

Before you go any further, take a look at
http://picasaweb.google.co.uk/fasand.words/LathesCanKill#
make yourself look at it at some length

now, a small hobby lathe or mill can't do that to your body, but it can do it to hands, fingers and eyes.

spend an hour or two with thumb and first two fingers of your main hand gaffer taped to the palm to simulate losing them.

*EVERYONE* who has NOT had or been present at a machine tool "accident" will think I am exaggerating the safety aspect.

OK, that out of the way.

1/ carbide / HSS debate.

Carbide is for production environments with very rigid machines, loads of spindle torque, where high material removal rates are the difference between trading and going bust.

HSS can cut anything carbide can, plus you can sharpen or harden it at home, it is NOT great for high material removal rates, but so what in a hobby environment. HSS can be posted out and CNC sharpened and posted back for a couple of bucks a tool if you don't have a suitable tool grinder and skill.

HSS is homogenous, the whole thing can be ground to be a tool, no brazed tips, no screwed in inserts, nothing to break and fly off, nothing to buy, nothing to go wrong.

2/ the lathe chuck key is something that exists in one of two states, it is superglued to your left hand, or to the tool rack, it is never, ever, ever left in the chuck.

3/ emergency stop bar triggered by your hips, plus the button.

4/ never ever ever do any chuck adjustments when the lathe is rotating OR has power going to it.

5/ set up the things that can go wrong FIRST, eg the trip to stop the tool feeding into the chuck.

6/ don't forget on a lathe the crossfeed is adjusting radius, not diameter, if the object is 4mm too large you only need 2mm of cross feed radius to get 4mm diameter.

7/ ensure the cutting edge of the tool is bang on centre height, and at the right angle to the work.

8/ if you get juddering "more feed, less speed" eg slow down the RPM and / or up the feed rate.

9/ go and look at that video again

I *HIGHLY* recommend you splash the cash on these
http://smartflix.com/store/video/574/Professional-Machine-Shop-Course-Vertical-Mill

HTH etc
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compig

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Re: Lathes and stuff
« Reply #20 on: May 30, 2009, 11:13:15 AM »
If that link is to the pictures I think they are I don't want to , can't , look at them again !!  I'm pretty impervious to horror films , car accident pictures etc , but those pix totally grossed me out. Just about the worst thing I've ever seen.
Good lathe info in the above post.
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GuyFawkes

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Re: Lathes and stuff
« Reply #21 on: May 30, 2009, 11:27:34 AM »
About '85 I saw a guy dragged into a (ship) shaft lathe running at 12 rpm, synthetic (not cotton) overalls so they didn't tear, thing was, it was powered by a big geared down flywheel weighing mebbe 5 tons, to get perfect steady feed RPM, so you couldn't just stop it in microseconds.

That's where I learnt the principle that while "accidents" may take several seconds to run their course, there is literally one thousandth of a second to change state from avoidable to inevitable. Once that thousandth of a second event has come to pass nothing can stop it.

To the OP, if you are in the UK I have those videos on DVD, mill and lathe sets
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Current status - project / standby, Fuel, good old pump diesel.

compig

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Re: Lathes and stuff
« Reply #22 on: May 30, 2009, 12:20:19 PM »
Mate of mine has a workshop unit located the site of a huge Automotive Forging works. They forge con rod's , suspension components etc. Was a very big company once but the shift in component production to Asia has massively reduced their business. There were maybe 100 BIG forge hammers there 10 years ago , now about 8 are still in use !! These hammers are about 15 ft high , lord knows how many tons , driven by compressed air now instead of steam at one time. Couple of months ago we were in the shop , 25% working , 75% chatting shit , as you do, when we noticed a BIG commotion in the hammer shop opposite. Apparently , one of the hammer operators had been hit in the thigh by a piece of shrapnel off one of the die's which had hit his leg like a hand gun round !! His thigh was broken and the fragment went straight through and out the other side !!  All we could see was him on a stretcher and LOTS of blood on the floor !!  The paramedics struggled for about 20 minutes to stabilise him before he could be moved , they were on the verge of calling the air ambulance. Guy survived but there is a possibility he may lose his leg due to complications.
When I first started going to my mates shop I used to go  stand watching this hammer at work as I'd never seen one working before , I  don't anymore !!
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AdeV73

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Re: Lathes and stuff
« Reply #23 on: May 30, 2009, 01:02:20 PM »
About '85 I saw a guy dragged into a (ship) shaft lathe running at 12 rpm, synthetic (not cotton) overalls so they didn't tear, thing was, it was powered by a big geared down flywheel weighing mebbe 5 tons, to get perfect steady feed RPM, so you couldn't just stop it in microseconds.

That's where I learnt the principle that while "accidents" may take several seconds to run their course, there is literally one thousandth of a second to change state from avoidable to inevitable. Once that thousandth of a second event has come to pass nothing can stop it.


Agreed. Those pictures are pretty gruesome; and, as you say, once the chain of events has started, there's no stopping it. I like to think I'm pretty clued up about safety around machinery - and whilst I've never owned my own lathe before, I've used them in the dim & distant past. No loose clothing/long sleeves around rotating machine parts!

Quote

To the OP, if you are in the UK I have those videos on DVD, mill and lathe sets


I am indeed - are you proposing to loan/sell/copy them? If so, please PM me with details... ta.

Andre Blanchard

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Re: Lathes and stuff
« Reply #24 on: July 03, 2009, 02:01:20 AM »
OK, that out of the way.

1/ carbide / HSS debate.

Carbide is for production environments with very rigid machines, loads of spindle torque, where high material removal rates are the difference between trading and going bust.

HSS can cut anything carbide can, plus you can sharpen or harden it at home, it is NOT great for high material removal rates, but so what in a hobby environment. HSS can be posted out and CNC sharpened and posted back for a couple of bucks a tool if you don't have a suitable tool grinder and skill.

Hello Guy, I have not been checking in here very often, good to see you are back.

If you really believe HSS can cut anything carbide can you should get yourself into a modern punch & die or mold shop.  Carving on 60Rc tool steels with coated carbide tooling is getting to be old news.
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Re: Lathes and stuff
« Reply #25 on: July 04, 2009, 08:13:25 PM »
AdeV,
As mentioned earlier, South Bend's book, "How to run a lathe" is good.  Also, Craftsman had a "Manual of Lathe Operation and Machinests Tables" if you can find a copy.  I believe you fit into the "amateur machinest" category as I do, so here is my 2 cents.  Start with HSS tool bits.  The above books cover how to grind them and it's not that hard.  Later you can experiment with carbide and draw your own conclusions. 
Best luck,
RH

oliver90owner

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Re: Lathes and stuff
« Reply #26 on: July 05, 2009, 12:32:11 AM »
I'm  certainly not a machinist but my 'hobby sized' lathe and milling machines do come in handy at times.

I like these hard and fast rules people keep banding about. 

Carbide tooling is ideal for the hobbyist if you can find the cutting tools and tips at a reasonable cost.  HSS is perfectly good enough if you are OK at 'tickling' them to maintain a sharp cutting edge at the correct angle - and not trying to cut carbide!  Cooling is much more important with HSS and very important with heat-hardened cutting steels. 

Free-cutting steels are ideal for turning if the duty is OK.  Makes operations so much easier.

Depends what materials you are working with and whether the cutting is cooled or not, etc etc.  Hobbyists get by with what they have.  The most important thing for a beginner is safety, safety, safety.  Until safety is automatic - and never compromised.

One thing I will say is that there is/are a lot of carbide rubbish out there.  I never buy the cheap stuff.  Usually either brittle or blunt - or maybe just inappropriate for my little lathe!

All that said, I mostly use carbide inserts.  I then know it is me, not the tool, that should be blamed for the poor workmanship!

Regards, RAB

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Re: Lathes and stuff
« Reply #27 on: July 06, 2009, 12:14:10 AM »
I will add that an important reason for me to usually go with HSS is the low cost, as well as being able to make a special cutter on the spot.  Either way, AdeV, when you get familier with your lathe, you'll probably wonder how you got along without it before.  They're really great for working on lister(oid) type engines, and a whole lot more. 
RH

xyzer

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Re: Lathes and stuff
« Reply #28 on: July 06, 2009, 01:27:57 AM »

My thinking is much the same as RAB only I went through high school then to collage trained as a machinist and all of my projects were done with HSS tooling. Then went and got a job in the real world and it was carbide from then on. HSS will work fine and so will carbide. HSS can be ground fairly easy to use as a form tool and so can carbide with the proper grinding wheels. Carbide turning inserts are ready to go where as HSS needs to be ground with the proper rake and clearance to cut proper for you. I will say with HSS you will need a proper grinder with the correct wheels and a bit of patients. You don't want to lean on it and burn the cutting edge and ruin it. So with HSS which is just fine you will need a good grinder with a roughing and finishing wheels and also be able to dress them properly. 
« Last Edit: July 06, 2009, 01:30:15 AM by xyzer »
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12 gauge

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Re: Lathes and stuff
« Reply #29 on: July 08, 2009, 03:29:12 AM »
xyzer,
Agreed, in the professional world it's got to be carbide. 
I got my start on a lathe in high school also, but I didn't pursue it as a career.  They taught with HSS so I've stuck with what I know.  Some carbide I've tried was pretty disapointing, but as RAB said maybe it was junk.  On the other hand I've borrowed a friend's brake lathe occassionally which uses a carbide cutter with excellent results.  So I guess, you pays your money and makes your choice.
All the best,
RH