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mini lathe and non aluminum cutting
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Since I purchased my mini lathe, I've cut aluminum successfully. The other day I decided to cut a bolt. I needed to reduce its diameter .050". Boy, I thought the machine was going to explode. There is just too much play, despite the fact that when I move the carriage by hand it's pretty solid. What should have taken me a couple of hours, took me one day--just to remove .050". I kept removing some metal dust for each passing, until I got to my target diameter.
I know that some folks advocate "tightening" or modifying the carriage as well as the compound. My jibs(gibs?) are pretty tight, at least I thought they were. I am not sure whether it's worth all the work involved. I joked with a buddy of mine, saying that a .10 screw cost me one day of work. I am fairly new at this, but I didn't know about the famous "play" until I tried cutting some non-aluminum stock. I'd like to hear from others and their experience with non aluminum, specifically steel. tc |
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Jamie Cunningham
I had something similar and MY problem turned out to be a loose leadscrew nut, not the gibs at all, once I tightened up the leadscrew nut I had no problems (I have an Enco 3-in-1 but the application should be similar on any lathe i think) :)
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Jamie
Check out my CNC projects (and more) at On Fri, Sep 30, 2011 at 10:07 AM, cervonetony <tonycervone@...> wrote:
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开云体育I wonder if the bolt was something that was fairly
hardened.? I would think that even a sloppy lathe could still cut.?
And even a great lathe will be seriously challenged.
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Try turning some piece of mild steel, that you know
is mild steel, and see if things are still that bad.
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Chuck K.
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Look at the head of the bolt. Compare it to this chart:
What grade is it? There may be a real good reason that bolt didn't want to be turned. On Fri, 30 Sep 2011, cervonetony wrote: Since I purchased my mini lathe, I've cut aluminum successfully. The other day I decided to cut a bolt. I needed to reduce its diameter .050". Boy, I thought the machine was going to explode. There is just too much play, despite the fact that when I move the carriage by hand it's pretty solid. What should have taken me a couple of hours, took me one day--just to remove .050". I kept removing some metal dust for each passing, until I got to my target diameter. Vince. -- Michigan VHF Corp. |
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What type of cutting tool are you using?
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--- In 7x12minilathe@..., "cervonetony" <tonycervone@...> wrote:
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开云体育?It's probably a hardened bolt. Torch it cherry red and then drop it into a bucket of ashes so it cools down as slowly as possible. After it is thus annealed, try machining it again. Are you using nice & sharp HSS tooling to actually cut or are you trying to snowplow/bulldoze your way through with cheap carbide insert tooling, or the worst of the worst, that flat topped carbide tooling where the tips are brazed on? The cheapo zero-back-rake brazed on stuff doesn't play well with small machines and harder metals. Good quality carbide inserts are available to replace the crap inserts that come with the import tooling. Seeand read through all the styles that are available for whatever type inserts yours takes, assuming you have indexible carbide tooling. You can even buy HSS inserts, if you haven't gotten set up to grind your own HSS (High Speed Steel) blanks and such like all the old timers do. ?Even the cheapest of the cheapest bolts are at least somewhat work hardened when the threads are press & roll formed in less time than it talks to talk about it. Generally speaking you'll need to cut your way through about 1/16"-ish or better of that hardened "skin" before you start getting into more machinable metal underneath, if you don't or can't try annealing it first. (Some steels are just plain argumentative no matter what you do, so to speak.) ?If you are going to play around with scrap "mystery metals" you probably want to get set up for hardening and annealing metals a bit. A good torch to get the part cherry red and then some ashes to drop it in so it slows down the cooling process as much as possible (I use fireplace ashes in a metal bucket), and of course be aware that zinc coated / galvanized stuff can really mess you up if you breath in the smoke - so do this torching stuff either outside or under a good exhaust fan. (Google or Yahoo a search on "" minus the quotes). ?You may want to remove the carriage off of the right side of the lathe bed altogether (disconnect the leadscrew mount on the right.). The inverted "V" grove that rides on the front prism of the lathe bed can be left with rough machining marks from the factory, so flip the carriage upside down and have a look to see if you have some very careful scraping/filing/sanding to do. The back carriage gib (that rides under the backside of the lathe bed) can be sloppy as well. Some folks have found that shimming is a good idea in this area. A lot of people have put in some serious work into the carriage to get their machines tuned in for making much deeper cuts without so much flex and movement. ?Another common option is to remove the compound slide altogether and replace it with a simple block of metal for the tool post to mount on. (I once tried this with a simple block of plastic that was big enough to mill to size and it worked surprisingly well, I suppose since it has good compressive strength). ?You bought a "preassembled kit" lathe that will require some patient, repeated disassembly and fixing up to get it to just where you want. This is much better for us poor folks than not being able to get a machine at all, and you learn a lot about the machine itself in the process, so it's all good for a hobbyist. Someone trying to run a business on light duty little hobby machines is certainly taking a more challenging route, in any case. :-) ?Cheers ?John Z. On 9/30/2011 10:07 AM, cervonetony wrote: ? |
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If it's a high strength bolt, it can be difficult to machine. There should be markings on the bolt head to identify its material type. It's more likely that your tool had a problem with either shape or height. Aluminum is soft enough to tolerate pretty sloppy tooling, although the surface finish will suffer. Most ferrous metals are a bit pickier.
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Roy --- In 7x12minilathe@..., "cervonetony" <tonycervone@...> wrote:
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I almost always use cutting oil (lard oil or sulphur threading oil for steel) when cutting steel but not so much with aluminum. Often a sharp tool will help considerably. Part of the 'theory' behind single tool cutting is to cut in one direction so that the 'play' is removed. Chatter is an issue and related to geometry (angles), stiffness, and 'play'. Certainly, trying to machine a hardened piece of steel will be very difficult.
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--- In 7x12minilathe@..., "cervonetony" <tonycervone@...> wrote:
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Wow weird. I use triangular kennemetal carbide inserts on 3/8 inch tool holders - widely sold, but you have to replace the chinese carbide with say kennemetal ?TIN 2151 type sold on ebay. The tool hoilders typically come in a box with about 5 different angles. I believe you can get them for 25$ on ebay.?
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This setup wiil cut that bolt iike butter. I just got finished removing .150 on an interrupted cut on a 3/4 hardened steel shaft. It took about 10 minutes to do. The triangular inserts can chew their way through any nasty steel work piece and keep doing it a long time. Ive had my k850 inserts in for 6 months with no sign of wear. And if you get chipping or wear, just rotate the insert! ?I estimate my carbide tools will last 100 years. But avoid the generic "C6" chinese carbide and get your carbide from Kennemetal or equivalent US makers. (Iscar is Israeli. Good but expensive.) If you dont have a QCTP you will need to shim the toolholder.? jb On Oct 1, 2011, at 8:12 AM, stantonleman wrote:
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Roy,
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Nice guide from LMS. I would recommend the toolholder on page 32 with Kennemetal inserts. I just looked them up on ebay, and they are 5$ ea. The kc5025 are the best, but cost 8$. Worth every penny. The Kc5025 good for cutting ss 316/304. JB On Sep 30, 2011, at 9:45 PM, Roy wrote:
If it's a high strength bolt, it can be difficult to machine. There should be markings on the bolt head to identify its material type. It's more likely that your tool had a problem with either shape or height. Aluminum is soft enough to tolerate pretty sloppy tooling, although the surface finish will suffer. Most ferrous metals are a bit pickier. |
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I have had no problem with any steels, and use carbide inserts practically 100%.
I buy industrial inserts and holders, and find that both the triangular and the rhomboid inserts work well, as long as they are positive angle. The ccmt inserts and holders will work well, and wont have any problems turning steels. About 6-900 rpm for a bolt, and 0.1 mm - 0.2 mm depth of cut, depending on size and hardness and chips. Any ebay sellers who sellers any brand carbide inserts work fine, ime. Of course, I have maybe 300 inserts, for a variety of purposes, and have had good to excellent success with all of them. I have not experienced this "chinese carbide" problem, myself. The key is, you MUST use positive insert geometry for a 7x. And the speeds need to be in the ballpark. In a busy month, I might use 4-8 inserts, and produce100 litres or 20 kg of tool steel swarf, some of it with the 7x, and some with other tools. |
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Yes, I bought the tool holders sold by LMS or HF for the triangular 2151 inserts. Theinserts that the TH came with were not nearly as good as the Kennemetal ones sold on ebay. I HIGHLY recommend upgrading to the US carbide.
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Could you explain why positive geomettry important? I take it that positive means the cutting edge has a hump right behind it? Thanks JB On Oct 2, 2011, at 7:09 AM, hanermo - CNC 6-axis Designs wrote:
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开云体育?Positive inserts work like a knife. They slice the metal. Negative rake inserts work like a bulldozer. They push the metal off. You cant really tell by looking at it, the rake is in the insert and holder together. Industrial users use negative and zero rake inserts, for better tool life and much faster metal removal rates. It takes a great deal of power, and the rigidity needed is an order of magnitude higher than a 7x. A positive rake insert might use 300W power for the bolt, at 0.2 mm and 900 rpm, in steel. A negative inserts might use 2-3 kW (at 10 times the metal removal rate, and double the tool life). The problem is, you need say 3 kW power to plow through the metal for the insert to work. Inserts work well when the chips are hot. Slightly dicouloured, straw, is best, blue is too hot, black is way too hot (reduce rpm). Too hot wont matter otherwise, the inserts just wear faster. No oil is needed, but can be used, in flooded condition. Many people try carbide inserts, and get poor results. The problem is that the inserts they use are wrong for their machine, (and or workpiece, ie the metal) and then conclude, erroneously, that the inserts are "bad". I have a very good 12x industrial lathe. 1.5 kW (industrial power, not "little chinese horses"). I dont use negative inserts, even though I maybe just might. The 5 degree and 7 degree inserts are the right choice on small lathes, and leave excellent finishes even on 316L stainless, effortlessly. The inserts I use work fine on my 7x, and on my 12x, and on my mill. I am sure than Kenci (kennametal) carbide inserts are good .. but so are iscar, seko, and many many many others. I buy whatever is cheapest, of the right type, shape and material. Industrial manufacturers ONLY manufacture good inserts. Their client know the difference (and you get freebies to try). The trick is for you to use inserts that are right for your application. An easy choice is to just buy ccmt inserts. These are 7 degree, positive, diamond (rhomboid) inserts well suited to lightweight lathes. They are generic, meant for semifinishing and finishing apps. A finishing cut at 0.1 mm is about as much as a 7x can do, anyway, in steel. Holders exist for boring, facing etc. etc. Inserts are about 3-4$ each, packs of ten, bit less for nos pack of 100. A pack/2 of 10 lasts about a year for a hobby user, for 30-40$. A lot longer in alu (tool lifetime is about 7-10x longer in alu). Good to great finish, in steel, alu and stainless 303, 304, 316L. When doing negative boring, undercuts, blind internal and negative bores etc. it gets harder. Most hobby guys dont need to do these. |
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MERTON B BAKER
Usually, you will find the screw still stuck to the magnet if you pull the
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swarf off with the pliers, carefully. Do not ask how I know this. Mert -----Original Message-----
From: 7x12minilathe@... [mailto:7x12minilathe@...]On Behalf Of Jim Good Sent: Sunday, October 02, 2011 11:39 AM To: 7x12minilathe@... Subject: Re: [7x12minilathe] Re: mini lathe and non aluminum cutting Any of you guys ever lose the tiny little screws for attaching carbide inserts to the tool holder? When you drop one of those into a pile of swarf, it's worse than looking for a needle in a haystack. Since I'm normally cutting steel, finding the screw with a magnet is right out. Jim ------------------------------------ Yahoo! Groups Links |
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Chris Bailey
Paint the head with hot pink or flourescent orange fingernail polish. ?Makes 'em a LOT easier to find when the inevitable happens.?
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Chris On Sun, Oct 2, 2011 at 10:38 AM, Jim Good <jagness@...> wrote:
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Jerry Durand
开云体育I was going to suggest using a non-magnetic screw so your magnet takes everything but it.??? :)I was also going to suggest the color as a serious suggestion, but Chris beat me to it. Nail polish is good for quite a few things, used it for attaching guides to fishing rods all the time when I was younger.??? Made regular trips to the cosmetic counter which probably didn't help my reputation any.??? :) On 10/02/2011 08:55 AM, Chris Bailey wrote: Paint the head with hot pink or flourescent orange fingernail polish. ???Makes 'em a LOT easier to find when the inevitable happens.??? -- Jerry Durand, Durand Interstellar, Inc. tel: +1 408 356-3886, USA toll free: 1 866 356-3886 Skype: jerrydurand |
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If you put your magnet into a plastic bag first, then pick up all the bits and remove the magnet whilst over a hard surface you will be left with a pile of ferrous bits but it will be much easier to look through
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Gerry Leeds UK ________________________________ To: 7x12minilathe@... |
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this is a great idea that i constantly keep forgetting. thanks !!
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george
From: gerry waclawiak To: 7x12minilathe@... Sent: Sun, October 2, 2011 12:28:17 PM Subject: RE: [7x12minilathe] Re: mini lathe and non aluminum cutting If you put your magnet into a plastic bag first, then pick up all the bits and remove the magnet whilst over a hard surface you will be left with a pile of ferrous bits but it will be much easier to look through Gerry Leeds UK |
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Rob B
I just bought a box of 100 of them and store them with my tools. From: george curtis To: 7x12minilathe@... Sent: Sunday, October 2, 2011 2:02 PM Subject: Re: [7x12minilathe] Re: mini lathe and non aluminum cutting
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this is a great idea that i constantly keep forgetting. thanks !!
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george
From: gerry waclawiak To: 7x12minilathe@... Sent: Sun, October 2, 2011 12:28:17 PM Subject: RE: [7x12minilathe] Re: mini lathe and non aluminum cutting If you put your magnet into a plastic bag first, then pick up all the bits and remove the magnet whilst over a hard surface you will be left with a pile of ferrous bits but it will be much easier to look through Gerry Leeds UK |
gerry waclawiak
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