Newbee questions

I will receive soon a 8x12 minilathe.
I have junk stock for practice and like to know if it is suitable for
turning.
Do not laugh please
Re-bar
Galvanized plumbing pipe, should be OK since it is threaded.
Galvanized Plumbing Fitting, cast.
Pressed powder objects.
Also, when is a collet a better tool than a chuck? What kind of situations?
Thanks
Mauro Gaetano
Reply to
MG
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Ouch!
Rebar can be almost anything left over at the mill. Typically it is at least .40% carbon, it can be much higher. Uniformity is poor. This is nasty stuff to cut.
Galvanized pipe is not much better. The only real spec on the material is that it hold 300 psi and be somewhat round with a hole in the center. It usually has a tough weld seam that will bounce your tool bit around. It also suffers from a lack of uniformity, in the same piece, from side to side, and between pieces.
Cast plumbing fittings might be somewhat softer. Not much else to say.
Powdered metal can be most anything. The sintered bronze bearing material cuts nicely with very sharp tools. A powdered stainless would be miserable.
Some one else mentioned getting REAL materials: -6061-T6 in 1/2", 1", and 1-1/2" -some leaded steel rounds ie some 12L14 is perfect -some brass rounds, maybe some hex
You can get any of these from
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you should be able to get some locally for half that.
Use a collet when you can for accuracy, use a chuck when you have to.
MG wrote:
Reply to
RoyJ
It would be worthwhile investing in a small stock of metals intended for machining. Go to a place which sells metals and buy some brass and free machining aluminium. If you want to machine steel, you can also get free machining steel which (I think) contains a small amount of lead. Any of these will machine much better than plumbing fittings and re-bar. Trying to machine bits of junk will be frustrating: you'll get problems with odd-shaped items slipping out of the chuck, poor surface finishes, and might even damage your cutting tool or machine. I'd say a small investment in materials is well worthwhile.
Best wishes,
Chris
Reply to
Christopher Tidy
I was planning on getting an assortment of stock but the wisdom here is to stay away from the junk pile. Thanks, appreciate the good help.
MG
Reply to
MG
Mild steel(like rebar) will generally not give satisfactory results because it just doesn't machine well. Gummy is one word that comes to mind.
Pipe is ok but you'll need a pipe center to machine the outside and a steady rest to machine the inside. Pipe tends to be not dimensionally accurate and not at all round.
You later made a comment about junkyard finds. Actually there is some very nice steel laying around in scrapyards. Look for shafting and such. Again, mild steel will be in structural shapes and probably should be avoided for lathe practice.
Reply to
Gary Brady
If you're not located where there are metal suppliers handy, don't forget eBay.
Check out the listings under "Business & Industrial > Manufacturing & Metalworking > Metals & Alloys"
Example; Here's some 3/4" diameter by 36" long 6061 aluminum bar stock with FREE shipping:
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There are some pretty good bargains available that way, and I've received some weighty quantities of short lengths of stock (bar ends) securely taped together and mailed to me in a USPS $4.05 "Flat Rate Priority Mail" cardboard envelopes. They let you put up to SEVENTY POUNDS into them. Sounds almost too good to be true, but that's what they offer:
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HTH,
Jeff
Reply to
Jeff Wisnia
Get some CRS or free machining material (with lead). It is the easiest to work and learn with.
You will cry of you use the material you intended. :-)
Nick
Reply to
Nick Müller
You need to get a "better" junk stock pile. As other have said, trying to learn on "bad" steel/metal will make your experience miserable. If you have "good" steel/metal and can produce quality work, then you know that you aren't doing something wrong (most likely) when you do the same operation in the same manner using junk steel and it turns out bad. Get a couple of chunks of 12L14 for practice and then maybe some brass. Different techniques for each. Good luck and ENJOY making chips. Ken.
Reply to
Ken Sterling
MG,
Good advice is offered herein on material. As you get better with your machining skills you can then utilize the "crappy" stuff for things where it doesn't matter.
As to collets: These are the ultimate in precision work holding and are used only on finished part surfaces when these surfaces are required to be concentric with the diameter to be machined.
Do not use collets on as-drawn / rolled material surfaces since this would destroy the collet's accuracy. Always use a chuck or face plate for un-machined surfaces. If the material surfaces are seriously uneven it helps to protect the chuck jaws if cardboard or soft metal is placed between the jaws and the work. Although the chuck jaws are heat treated and quite hard, they will wear in time. This can be slowed down by use of protective material between the jaws and rough work surfaces.
Collets may be used on commercial ground stock such as drill rod, but the diameter of the stock should be within +/- .002" of the collet's size. The exception are ER collets and rubber flex collets, each of which has a greater size range than do the more usual spring steel collets. If the work piece diameter is slightly out-of-range of the nearest collet size the difference may be made up with shim stock wrapped around the work forming a sleeve.
How to tell the difference? If the collet jaws are separated by rubber, it's a rubber-flex collet. If the collet has slots running from each end of the collet, and each end of the collet has a closing angle on it, it may be an ER collet or similar.
It is worthwhile for you to do a little reading on the use of collets. It will pay off in spades as your machining ability becomes more sophisticated!
Wolfgang
Reply to
wfhabicher
MG,
Good advice is offered herein on material. As you get better with your machining skills you can then utilize the "crappy" stuff for things where it doesn't matter.
As to collets: These are the ultimate in precision work holding and are used only on finished part surfaces when these surfaces are required to be concentric with the diameter to be machined.
Do not use collets on as-drawn / rolled material surfaces since this would destroy the collet's accuracy. Always use a chuck or face plate for un-machined surfaces. If the material surfaces are seriously uneven it helps to protect the chuck jaws if cardboard or soft metal is placed between the jaws and the work. Although the chuck jaws are heat treated and quite hard, they will wear in time. This can be slowed down by use of protective material between the jaws and rough work surfaces.
Collets may be used on commercial ground stock such as drill rod, but the diameter of the stock should be within +/- .002" of the collet's size. The exception are ER collets and rubber flex collets, each of which has a greater size range than do the more usual spring steel collets. If the work piece diameter is slightly out-of-range of the nearest collet size the difference may be made up with shim stock wrapped around the work forming a sleeve.
How to tell the difference between collets If the collet jaws are separated by rubber, it's a rubber-flex collet. If the collet has slots running from each end of the collet, and each end of the collet has a closing angle on it, it may be an ER collet or similar.
It is worthwhile for you to do a little reading on the use of collets. It will pay off in spades as your machining ability and requirements become more sophisticated!
Wolfgang
Reply to
wfhabicher
All very true, and certainly the advice appropriate to a world-class machinist who can't bear to work to mere thousanth's, sneers at tenth's and is only comfortable with 1/100 thousanths, precision or better. For the rest of us mortal home shop machinists who routinely work to within a few thousanths and especially for newbies, some clarification is in order.
First of all, as to how close the collet should be to the stock. A typical collet, such as 5C collet has a range of holding power. 5C collets can be had by 1/64" increments, which allows you to work to clamp a piece that is within +- .008". The 1/32 series collets have a wider (double) clamping range, and the 1/16"series collets have four times the clamping range. That is, the 1/64, 3/64, 5/64 etc. collets have a range of +-0.008 (actually a trifle better), the 1/32, 3/32, 5/32, etc. have twice that clamping range (0.0156) and the 1/16, 3/16, etc. have double that. This means that when you're starting your collet set you can first buy a set by 1/16", then fill in with the 1/32" range, and finally, when you're really flush, fill out with the 1/64" range collets. Note that you need to buy twice as many collets for each upgrade. I don't know how to buy commercial 5C collets that are with +-0.002" of an arbitrary diameter piece of work, except by machining a machineable collet to that size or just working with odd diameter stock. Now granted that this is not the ultimate in accuracy, but holding to within a thousanth is routine. You can also buy an adjust-through (also called set-through) type of collet chuck that allows you to indicate your work to within a 1/10th (thousanth) if you need that, and assuming that your lathe spindle has less than that in runout, that your tool post has less than that in slop and give, not to mention the accuracy of you bed, ways, etc. The point is that accuracy is a cumulative process and every part of the machine and setup must be up to the same standard or else you are just throwing money away and fooling yourself. Now as to the use of chucks rather than collets. A chuck is accurate at only one diameter. And at other diameters it can be off by several thousanths. Ideally, you would have to put a spacer into your chuck of the right diameter, and then precision grind the jaws for that specific diameter. Alternatively, if you're not too fussy, is to have a set-through chuck which you can adjust for that specific diameter with the work in place. This is time consuming and requires the use of dial indicators (or precision test indicators for the 1/100th thou purists). An experienced precision machinist will often choose to use a four-jaw independent chuck which can be adjusted very precisely. When you do need (rarely) to have a very precise fit of the collet to the work, you can use a machineable collet. This is made of brass and is easily bored out the exact diameter you need, as possible as it is to do on your lathe. Always good to have a few of those machineable collets around.. I have several, and have yet to use them. As for "ruining" the accuracy of the collet by having it too far away from the work diameter... yeh, certainly the case if you were in production, making thousands of parts. For the typicaly home shop machinists this isn't an issue because:
1) The wear and tear on the collet of one week of production work in a commercial shop is likely to be greater by an order of magnitude than the typical home shop machinists is likely to put on in a lifetime. This, by the way, is one reason that when you buy used collets, you should not buy the popular ones (1/4", 1/16" ranges) used. Such collets are often beat and close to worthless.
2) The typical home shop machinist is not going to buy super accurate collets such as Royals at $30 each (more for square and hex), but a good quality generic Chinese set at $6.00 each or less on sale.
3) The accuracy super-pros I've met keep their collets in their individual little plastic cases and would be horrified at the very thought of having them out in the open air in collet racks. Us poor slovenly home machinists like to have them in racks where they are handy but where their accuracy probably deteriorates by a few millionths of an inch every week or so. If I had a set of Royals comparable to my 5C set, I'd have them in a large, humidity controlled, glass-fronted case, with each collet in it's own gently cushioning felt-lined holder. And I probably wouldn't ever use them, but I would certainly pray before that collet shrine five times a day.
Now should a home shop machinist invest in collets? Certainly a three-jaw scroll chuck and a four-jaw independent chuck have priority. But beyond that?
I admit that I am a collet freak. It has taken me many years, but now I have a full set of 5C collets by 1/64", a square set by 1/16th, a hex set by 1/16", a dozen inside collets of various sizes up to 4", pot collets up to 6", and if they made 3 sided, 8 sided, and 7 sided collets, I'd probably buy those too. Because my milling machines require different collets, I also have MT-2 collet sets, 3C collets, and B&S #9 collets. Like I said, I am an admitted collet junky.
I've got a lot of different chucks, face plates, and all that other stuff, but I keep my 5C collet chuck on my 12" Clausing lathe and use that for 98% of my work. The collet is more convenient, easier to use and set-up, more accurate for routine work, holds better, gives you a less obstructed view of your work, and is less dangerous than a chuck.
Collets are a distinct advantage in machining very thin, flat pieces (done in a pot collet) and for machining something that must be held on the inside. Collets are also superior to chucks when working with very small parts. I do ship models, so I am often working with really small stuff and only a collet will do the job. I've often thought about buying a watchmaker's lathe for the really small work, but what's kept me from that is the difficulty in finding one with a full collet set on the used market at a price I can afford. Small lathes like that are often used only with collets, it is the chuck that is the exception.
The main limitation of collets is the limitation on maximum size. 5C collets have an upper limit of 1.125" (more with pot collets if the work is flat and more for inside holding). The smaller 3C collet only goes up to 1/2". Another disadvantage for some collet set ups, is that when you use an collet chuck on an older or smaller lathe, you can't mount the collet directly in the lathe's spindle nose. For example, a classical South Bend 9" and my Clausing 12" have only a 3/4" spindle bore, so they can only take 3C collets or MT#3 collets. For the bigger collets (e.g., 5C) you use a collet chuck. Well it takes a lot of turns of the chuck key to put the collet in, tighten it, or remove it. But hey, we home shop machinists usually have the time... especially when we spend more time looking for the chuck key than tightening the chuck. When you have a through-the-spindle collet set-up opening and closing is done by turning the collet drawbar wheel which is much faster. (yeh! I know all about Sjogren chucks, but what newbie is likely to buy a chuck that costs twice what his lathe costs?). Boris
------------------------------------- Boris Beizer Ph.D. 1232 Glenbrook Road Huntingdon Valley, PA 19006
TEL: 215-572-5580 FAX: 215-886-0144 Email bsquare "at" earthlink.net
------------------------------------------
Reply to
Boris Beizer
Correction:
Of course I thought of another, very important thing you can do with collets that is difficult, expensive, or almost impossible with chucks. I often have to work with small-diameter, thin walled, brass tubing ... from 1/8" diameter to 1/2" diameter. I have to cut this tubing off to make small brass rings from 1/32" to 1/16" wide. These are used for bands on masts and other spars. Can't do that in a typical chuck because the chuck only grabs at three points, while the collet grabs all around. With a 1/2" tube in a chuck, the point at which the chuck starts to hold and the point at which the chuck crushes the tube are very close. You can use a six jaw chuck, I suppose, but that's expensive and not as good as collets.
I'm sure that other fellow machinists out there, professional or amateurs, will provide even more examples of where a collet is the holder of choice, as contrasted to a chuck.
Boris
Reply to
Boris Beizer
I'm barely ahead of you but i stumbled into an amount of 3/4" buy 16 to 18" long peices of brass that were being sold for $1.80 each at lee valley tools (Spares from their tool factory next door)
Basically to me its learner metal and easy to work
I wuould suggest picking up something similar like round bar brass as a "student metal" especially in small amounts
HTH
Reply to
Brent Philion
According to Boris Beizer :
[ ... ]
How about a chuck with two-piece jaws, with Pie section soft jaws? Those could be machined to size for your tube, and would hold contacting almost all the way around, with only fairly narrow gaps.
Or machinable soft collets could be made to fit what you don't have a precisely sized collet to fit.
Well ... I consider soft jaws to be a good alternative to a collet, as above. But one nice feature of a collet vs a regular chuck, at least, is the ability to put a work stop to set each of a batch of workpieces to the same depth (length). (Of course, with soft jaws, you can turn the socket and the stop in a single setup -- with the exception of workpieces which are longer than the depth of the jaws, but shorter than the range of collet stops.
That said -- I use collets more often than soft jaws, because they are convenient. :-)
Enjoy, DoN.
Reply to
DoN. Nichols
I could do that, of course, but then I'd either have to have a whole bunch of them, or a whole bunch of machinable jaws, or be constantly remachining the jaws for the next ring size. Putting in the right size collet is sooo much easier and faster than swapping jaws.
As I said, I have a bunch of those machinable collets and I've never used them. However, last week I did get a situation in which my collets didn't work... not the round collet, but the square collets. Too small for the 3/16 and too large for the 1/8. Obviously I needed 5/32, but I've never seen those around .. or I could have ground out the space between the jaws to provide additional grap range. I just changed the stock I was using. Yeh! Yeh! I know, I missed a royal opportunity (excuse) to spend several hundred on a set of broaches.
Good point. For the newbies, a caution. When you buy used 5C collets, make sure that they have the ***inside*** threads for the collet stop as well as the regular outside threads for the drawbar. Many older 5C collets do not have the inside threads.
Boris
Reply to
Boris Beizer

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