Sorry if my writings are little clumsy. Metalworking is new for me especially in English ;)
I'm trying to achieve plain (smooth) alloy after turning threads. I've made special knife with carbon plate so that I can cut as near side as possible. The problems is in surface quality. My alloy is 2H13 (0.2 C and 13% Cr and maybe small amount of Ni). Is it possible to get good surface without polishing?
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
O.K. Let me see whether I understand you properly -- and offer some terminology in English in the process.
Given the fact that you *can* communicate in my language, and do a rather good job of it, but I cannot communicate in yours, that shows that you are *interested* in communicating. I do have at least one other language, but not yours, unfortunately.
"special knife" -- threading tool?
For most applications, you don't want to use carbon steel for the task, but rather at a minimum, HSS (High Speed Steel), or for some alloys, (tungsten-)carbide inserts. Carbon steel can work with care with mild steel, but I think that your alloy, with 13% Cr would be rather tough, and would rapidly dull the carbon steel. For that, I would prefer to use the special carbide inserts in the proper shank (holding tool) for the threads which you wish to cut.
Note that the size of the lathe, and the rigidity and power will determine whether you can use carbide tooling to get a better finish. Your "2H13" appears to be one of the European steel designations, and I am not familiar with it. But 13% Cr would probably make that a rather tough steel. Perhaps Ed Huntress could pop up with a close equivalent in US steel grades?
It may even be that it would be better to grind the threads instead of to try to cut them -- but this will require a rather expensive setup.
Are you doing this as a hobby, or are you in a commercial machine shop? The tools which would be standard in such a commercial shop are less likely to be found in a home shop for hobby use.
You'll find mostly hobby metalworkers here -- though there are some who do it as a job. We really need to know some things about the task and the equipment. How big a lathe? What thread diameter and pitch? (I would expect them in metric units given your e-mail address.)
As an indication of the sizes of lathes, Mine is an old Clausing which will swing 12" (300 mm) diameter over the bed, and somewhat smaller (at least 6" (150 mm) over the carriage. I consider this on the large end of hobby lathes, though there are others here with larger machines. Mine is sufficiently rigid to be happy with carbide tooling and reasonably tough jobs.
Carbide tools can give a smoother surface to the cut, but they often require higher speeds and more rigidity from the lathe than equivalent HSS tooling can.
Carbon steel requires *much* slower speeds or the tool overheats and looses its temper.
Yes - terminology through communication is what I need far away. So I should use cutter not the 'knife' for turning tools right? I'm studying Materials Engineering and turning is my temporary hobby that allow me to realize some projects. For example integral spheres for photometrical measurements.
2H13 is an old Polish label. Now we use European but they are not intuitive for me so far. Do you know any site that deals with US. Alloys nomenclature?
The carbide inserts are the only usable. Maybe ceramics can be right too. There's something weird with turning speed for threads. Let consider pafana.pl carbide inserts. Average turning speed for stainless steel is 100 m/min. Now having 42 diameter I should set my machine to:
n = 1000*Vc/pi*D = (1000*100)/(3.14*42) = 758 [turn/min]
This is some speed! Stopping the machine will cost some time :) Oh BTW how you name this small distance (synonym is paddock) where you must set your cutter and turn on machine. This distance has smaller diameter than thread.
My lathe is rather powerful enough (1800 turns/min) and my spindle handle 100 mm rollers. Take a look:
formatting link
2H13 can be toughened so that 60-70 HRC is possible but I don't think it was toughened. I can check with Vickers hardness test after cutting my work. The surface is struggled because of hard shavings fall (I don't know if 'fall' is good here, maybe flow down or something).
Yes however in my city, a common pitch is >1.2 and I need 1.0 with 42 diameter (mm). Also the length of thread is small - max. 5 mm.
As I wrote this is a hobby for University purpose. Imagine that we have Technology Hall. They have digital lathes from Sandvik but they don't know how to cut thread with good surface for right price. It is also some relation problem. I did ask first can the chief do it for me. He told me he doesn't have a time and went away to a tools room. I did ask another guy. He shook his head. Now all the peoples (it was vacation time) staying and looking at my work. It looks like (I can't put drawings on my server for a while): ------------------ | | | 70mm dia ---- | |---------- | | | | | /xxxx | | A |
---------------- |--------------------- ---- | | ^ | |- | | -----------------------|-| which will swing 12" (300 mm) diameter over the bed, and somewhat
I would say the same instead of threads :)
That is so. I will try to use ready thread cutter (carbide soldered to the grip) and grind it so that it can be used with that flange.
With Kind Regards, ______________________________________________________________________
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
"Cutter" or "Turning tool" or "lathe tool" all would work. "Knife" implies a kind of cutting not normally found on a lathe. Actually, "threading tool" applies specifically to what you are using.
Hmm ... for that, perhaps spinning of thin sheet metal, instead of machining. Make two pieces (one with an access hole and one without) joined at the "equator" (if you were talking about the planet instead of a man-made sphere.)
I'm sure that such exist, but what I currently use are two books. One is _Machinery's Handbook_ (pretty much any recent edition), and one is an older Jorgensen steel catalog. Since both are in English, they may be hard for you to find. I don't know how available English-language technical books from outside the country may be.
It is rather fast, given your need to cut a short thread, and the lack of clearance. One thing which might help would be to turn the tool upside down (adjusting to set the height of the point correctly) and to cut in reverse, so you cut away from the shoulder. However, I don't see provisions for a "runout groove" (where the metal is cut away completely, to provide a space where the tool's motion can be stopped (or in this case started) without messing up the thread which you are cutting. Can you introduce such a groove into your design? It will make the job a *lot* easier.
I think that this must be the runout groove which I mentioned before.
Note that you should not need to start and stop the lathe spindle if you have a runout groove to place the threading tool in to start, and a threading dial which will allow you to close the half-nuts at the same reference point each time. (With metric threads, I understand that the threading dial has a sliding gear with four different sizes to engage the leadscrew, depending on the particular thread to be cut. I've not had to work with this style before.
Anyway, with the spindle turning, you crank the point of the threading tool (the one which you have illustrated would be for threading towards the shoulder right-side up, you would need a different one for the upside-down threading, given how little clearance you have. (Note that I am not accustomed to using the brazed (silver soldered) tooling, but rather the style with the removable inserts, where a special pocket exists on the tool shank, and a clamp to hold the insert in place. These are cheaper to replace inserts on, but what you have is probably cheaper in initial purchase price.
Anyway -- you move the threading tool into the groove, and set it to a very shallow first cut, lubricate the workpiece (I would probably use "Molly-Dee" a molybdimum disulfide based cutting oil for this, but I don't know what you have available. Once it is in to the desired depth, wait for a mark to line up with the index on the threading dial, and note which one you use (probably should just use the '1' mark -- at the speed and pitch you are working with, the mark will come around fairly quickly. Then, just as the '1' mark approaches the index mark, quickly close the half-nut lever. This will start the thread cutting -- hopefully away from the shoulder if the gear setting is right, and the spindle is running backwards. Once it clears the end of the thread, pull back up on the lever to disengage the feed. Then crank the cross-slide back enough to clear the workpiece, and crank the tip of the tool back to the runout groove. Then crank the tip back in to the previous depth, and (just this once) stop there, and re-engage the half-nuts lever as before. The tip should travel in the same groove you just cut, without removing much (if any) metal. This is helping you to be sure that the thread dial is at the right setting.
Once that is proven, crank the tip back out again, and move it back to the runout groove. Then crank it in and go just a little deeper. (I won't suggest absolute depths, as you will have to find out what works with your material and your tool. However, as a starting point, try 0.10 mm. It is a bit shallower increment than I would use at the start of the cut, but not much. (I would normally be working in inches, not mm, though I sometimes work in mm.) As you get deeper, you need to make the increment a bit less, as you are removing more material per cut. The final cut, you should repeat at the same depth a couple of times, which will produce a smoother thread. Then take a file and clean up the crests of the threads.
Note that US practice while threading usually has the compound set to feed almost along one flank of the thread, taking most of the cut off the other side. A common setting is 29.5 degrees, though 29 degrees will work as well. With this technique, you bring the cross-slide back in to the same depth and then add a bit more feed using the compound each time. This means that you will have to correct the compound's feed for the angle to get the right depth -- but you should also have some way to measure the thread depth directly -- thread wires and a micrometer, or if you have access to one, a thread depth micrometer with the right anvils for you 1.0 mm thread pitch.
Normally, the angle of the compound is to feed it in and a bit towards the headstock side. With the reversed spindle you would use the same -- or with no reversal, you would need to shift it to the other side. Apparently, UK practice is to just feed in square, which would give you a little less to worry about, but which might not produce as good a thread. Certainly, cutting towards the shoulder would require a lot faster reflexes if you want to get the maximum speed out of the carbide tooling.
Speed is only one point. There is also the power of the motor. I am used to it being expressed in HP (horsepower), but European motors tend to express it in KW instead. My motor is 1-1/2 HP, which should be somewhere around 1.2 KW or so.
Hmm ... I see the brazed (silver-soldered) carbide threading tool. I was sort of expecting the lathe, instead.
Now -- if you really *have* to cut to the shoulder and not have a runout groove, what I would suggest using for the machine would be a CNC lathe -- as that can cut and withdraw the tool at precisely the same point each time, so the end of the thread just lifts out of the groove.
I'm not quite sure what you mean by "fall" above.
However, one consideration, even if the material starts out annealed (maximum soft state), it may work harden -- and I suspect that a steel with that much chromium will do so. This may require you to make deeper threading cuts than I would otherwise like to make.
So -- at most 5 complete threads, and probably less. Certainly less if you make a runout groove.
"digital lathes" are probably what I would call "CNC lathes". "CNC" stands for "Computer Numerical Control" in English.
O.K. Are you using a live center on the tailstock to support the free end of the workpiece? That would reduce chatter (vibration of the workpiece as you cut). I *think* that 'B' is supposed to be a hole, though it appears to stick out a bit. Is the 'A' part a circular groove? If so, is the inner diameter of that the same as the 42 mm of the other end? If that is the case, and if the part does not need to resist lots of twisting force, I would think that it would be easier to start with a workpiece just big enough to cut the threads on the OD, and turn the 42 mm parts on each end. Them make the 70 mm diameter piece with a hole just slightly below 42 mm (perhaps 41.94 or so) and heat the
70mm diameter piece to expand the hole, and slide it onto the other part after the threading is completed. It will quickly shrink and become close to immovable -- how much depends on the actual sizes of the shaft and the hole.
Anyway -- looking at other ways to make something (sometimes of two or three pieces, instead of just one) might make it easier to make.
When grinding carbide tooling (you will need something better than the typical bench grinder), you should wear a breathing mask to keep the dust out of your lungs. It can be bad after a time.
It is really late now (about 2:30 AM), and I am going off to bed. I hope to get back to your next message before it is quite this late -- but I will be at a long meeting tomorrow evening, so I may not make it back in time.
The suggestion that reverse tool arranging (upside down) is one of the most important and can be proven using forces analysis. I've never tried that way.
I am not sure but in paragraph "Note that US practice while threading[...]" you describing special cutting technique used in mass production so that the cutter is worn evenly right? I'm trying to figure out all that angles in English used in turning. Now I have *two of 4 (*alfa, *gamma, epsilon, kappa) and a little mess with shoulder and tailstock. Are they synonyms or shoulder is synonym of headstock?
The link I provided so far extract the Java Console installed on your system. Then you certainly will able to see panoramic image of the turning room.
Fall is used to express what is happening with cut material (shavings). It should be able to "flow down" :) Is it correct?
No I didn't. The material is quite rigid (stiff?) so I gave up this idea. Maybe this can be such mistake.
Yes.
No :)
So in summary we have to check two ways: reverse cutting and extra small depth of cutting. In next week I will try this. Thank you so much.
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
A shoulder is a flat surface perpendicular to the axis, adjacent to a smaller diameter, or any similar feature where the part changes diameters. If it is at the end of a part, it is usually just refered to as a face. In the case of your part, it is the section adjacent to the diameter where you are cutting your threads. Threads are much easier to cut when you don't have to worry about where you stop and start the cut because of the rest of the part getting in the way. This is why some were suggesting you make the part in two pieces. --Glenn Lyford
The major benefit is that it allows you to thread in reverse -- which is normally of benefit when threading up to a shoulder. However, you would probably be better off to have a runout groove as a starting point, and thread away from the shoulder in the normal direction. I think that I got this wrong in the other article, and again, I am typing at 1:00 AM, so there may be other errors.
No -- this is also done in hobby work, and the benefit is that the chip is mostly formed on only one side of the tool, with the other side grazing the flank of the thread, and taking very little metal from it.
Another benefit is that this keeps the forces in one direction, so it holds the half-nut firmly against the leadscrew -- even if it is worn badly enough to have significant backlash. As Harold Vrodos would tell you if he were in this thread, this can lead to "drunken" threads
-- threads which wander a bit to the left or right of where they should be.
A shoulder is an artifact of a workpiece. One which prevents you from having free access to both sides of the area. In this case, as you have it mounted, based on your ASCII drawing of the workpiece, the larger diameter gets in the way of your threading to the right of the area being threaded. It is better there, than to the left for normal threading, as long as you cut a "runout groove" (a groove as deep as the thread, and enough wider with a flat bottom so you can either position the threading tool before starting the cut, or (in the normal direction of threading), so there is a wider place to give you a bit more reaction time to pull up the half-nuts lever and stop the feed of the cutting (threading) tool.
While we're here, let me make clear the meaning of headstock and tailstock, just in case you need those.
Headstock: The part of the lathe which contains the rotating spindle, and drives the workpiece by one of a number of means -- holding it in a collet, holding it in a chuck, holding it between centers, and driving it with a lathe dog and a faceplate, clamping the workpiece to a faceplate.
Carriage: The part of the lathe which carries the cutting tool, and travels from left to right under hand control or under power. It also carries the cross-slide, which may carry a compound which may be adjusted to move at an angle to the cross-slide, as when threading.
Tailstock: The portion of the lathe which may be moved from right to left after unclamping it from the bed, and then may be clamped to the bed to drive a drill bit (in a drill chuck or with a taper), or to hold a live (or dead) center to steady the tailstock end of the workpiece to control flex, or to allow turning between centers.
Oh -- I keep Java and JavaScript turned off for security reasons. Are you sure that was not another URL? I backed up one layer and found another one called "panorama" (or something like that), but I could not see the panorama without enabling Java or JavaScript.
O.K. For normal turning, the chips curl up above the tool, and (depending on the geometry of the tool, the depth of cut, the presence or absence of a chipbreaker groove (part of the geometry of the tool), and the characteristics of the metal alloy, the chips will either flow smoothly in a continuous string, curl, or break into short pieces. The last is the best and safest, and is the purpose of a chipbreaker groove in the tooling.
However, with an upside-down tool (either with reversed spindle with the tool in the normal position, or with the spindle running forward, with the tool located on the back of the cross slide, as is sometimes done with a parting tool), the chips fall from the cut more easily. This is probably most beneficial in the parting, where the chips tend to build up and jam in the cut, and is one of several reasons for the upside-down parting tool in the back of the carriage.
It can be, indeed. It is amazing how much flex there is in a workpiece and in the machine tool itself. Anything to minimize that helps. In this case, the fact that you have a larger diameter towards the tailstock (which is what forms the shoulder restricting access to the area to be threaded) tends to create higher forces while turning that part, and the smaller diameter towards the headstock and the chuck (or collet -- I don't know which you are using to hold the workpiece) allows greater flex in the workpiece. So use of a live center in the tailstock to support the free end will help reduce "chatter" and improve the finish in your thread -- as well as in other parts of the project.
Is it smaller, or larger? If it is smaller, then making the part as two pieces and heat-shrinking them together will make it easier for you to turn the threads, as you can eliminate that shoulder to the right of the area being threaded -- at least until after the threads are cut and the other piece is heat-shrunk in place.
I believe that another followup showed your material as being similar to 420 stainless steel in the USA.
If so, the description in _Machinery's Handbook_ says;
420 (S42000) Higher carbon modification of type 410. (followed by a list of typical applications.)
What it does *not* say, and what I would expect, is that it would be likely to work harden, in which case you need to be careful not too make *too* shallow a cut. Once it work hardens, you will have a difficult time getting the cut going again.
I've never used this, but I do use 416 SS, and find it fairly nice to machine. (Though I don't think that I've tried threading it.
I'm sure, there is no another URL. This is just an applet. Nothing more. So all in all I understand you have seen my panorama.
It is smaller. If the "easy way" is concerned then no problem but the case is to make the worst way :) having integrity on axis. Imagine there's such thing you must do it as I do. The end justifies the means :)
The teacher says to student "We have in Poland such a carbon steel which is weldable, but the same steel in US. isn't meant to be weldable :)". This show the technological level differences in general ;)
Stay tuned for part two of this thread. ______________________________________________________________________
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
The original URL showed me only what appeared a brazed insert threading cutter.
When I removed the last element of that URL, I backed up to a page which offered several choices, including one labeled as a panorama. When I selected that, I saw nothing -- but since I have Java and JavaScript turned off, I would not expect to see anything, if it is powered by Java or JavaScript.
You need the thread to be truly concentric to the ID of the hole in the large end. How important are the other features of that end? The ones which come to mind are:
1) The OD of the inner part of the groove.
2) The ID of the groove.
3) The depth of the groove.
4) The OD of the major diameter.
If none of those have to be precisely concentric with the threads and the central hole, it strikes me that the easier way is the best choice.
There are variations of alloys some of which are easy to weld and some are not. I know that 12L14 (a very easy to machine mild steel alloy) is supposed to be difficult to weld, because of the lead content.
1214 (without the 'L') is a bit more difficult to machine, but is easy to weld. You have to make choices based on what you need to do.
I believe that some stainless steel alloys also have additives which make them hard to weld, but easier to machine.
I don't do welding (yet) so I don't know too much about this, but I do know that there are alloys which are designed to be easy to weld, and others (almost the same, but for small changes) which are difficult to weld, but easier to machine.
If you don't want to activate Java then use the following url:
formatting link
All of the items you have listed should be concentric but this is relative. The part I turning is for my telescope so that logically they should be concentric as it's possible. However I wouldn't be surprised if the off axis position that is always there can damage optical quality for standard observer.
What I have in mind telling the story is showing the US. high expectations of the steel quality - the Teacher said that many kinds of steel doesn't appear in my country. Take the Abrams tanks for example.
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
That looks like an impressive lathe, and I *think* that it even has two sets of leadscrews -- perhaps one for metric threads and one for imperial threads -- plus a keyslotted drive rod for the longitudinal feed when you are not threading, but rather looking for a steady feed to produce a nice finish.
I have seen binoculars constructed with an intentionally off-center hole in the front for the lens, and provisions for turning the part containing the off-center hole to adjust the lens to more precisely on-center than normal production tolerances would otherwise allow. So -- sometimes, eccentric parts can improve accuracy.
This is why one should design in means for adjusting the eccentricity, rather than depending on everything to be perfect. It makes it easier to make good products.
Is this to be an astronomical telescope? (For viewing the stars?) If so, there are usually many sources for errors in such equipment -- and I have seen many made with the main housing made of rolls of cardboard, which is not the most stable of materials. (These were made by amateur telescope makers, who also very carefully ground their own mirrors.
You should perhaps be pleased that that particular example does not appear in your country. Where ever it winds up, it is usually because of problems in that area, and presages more problems. (Of course, I have seen places where such things were present for training, not for actual use. :-)
Yes -- there are many specialized steels here, and many in various European countries as well -- and there is not always a precise match between them, but for most purposes, there are many varieties of steel which will serve quite well.
I do purchase some products from your country. An example is lathe chucks, which are sold here under the name "Bison", though I don't know what the factory actually calls itself. In any case, I am quite pleased with the equipment from your country which I have and use regularly.
Were not the tanks used by the Russians built in your country at one time (before the breakup of the Soviet Union)?
Our Polish lathe is rather old - maybe 25 years now. It needs a little tuning. You're right it can turn metric and other threads as well but the minimal pitch is 1.0 mm so for precise mechanics it fails.
Binoculars eccentric mounting - it sounds interesting. In old binos you have to unscrew the lens a little to match two objectives. Otherwise you can get a squint ;)
Yes this is a superb an well known Carl Zeiss Jena Telemntor refractor (objective D=63mm fl=840mm) produced between '88-'90. It has outstanding built quality.
Do you have the company www site who sells "Bisons"?
Yes they were for example casted parts made in Polish stealworks (Katowice) but where was the assembly hall - no doubt a south of Poland (Slask).
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
Hmm ... is it possible to add extra gearing at the left-hand end of the headstock, to cause the threads to be 1/2 or 1/4 of the current ones? I suspect that it is -- but perhaps the gears to do so were optional, or were lost in some move.
This, I first found in some old cheap Japanese binoculars (back before Nikon and Cannon were recognized as high quality optical firms.
Aha -- you are repairing an existing telescope. I would love to see it.
They are sold by several companies, including MSC (http:/
formatting link
and New England Brass and Tool
formatting link
While I buy most things from MSC, for some things (including the Bison chucks) I use New England Brass and Tool. I'm sure that there are other vendors who sell the Bison line as well, but I don't happen to have their URLs handy. I suspect that the "Bison" name comes from an importer, rather than from the factories in your country.
Far better to make them than to be where they are being used. :-)
The design of this old lathe allow only >1mm. Changing internal gears seems to be hard and time consuming. There's possibility using normal feed but you must cut once.
Hmm ... normal feed is usually via a clutch and gear to the handwheel, so yes, it would not repeat well, and it is unlikely to cut a clean thread in a single pass.
I wasn't talking about changing gears within the headstock, but there usually is a cover which can be removed or opened on the left-hand end of the headstock to give access only to the gears used for threading. If this is a gearhead lathe, instead of a belt-driven one, perhaps all of the gearing is internal. But the Jet gearhead lathe which we had at work a few years back brought the feeds out to the cover at the left-hand end of the headstock, so you could at least install the metric changegears for metric threading.
That is why you are doing this work, of course.
O.K. I can't connect this evening, but perhaps another time. So Bison is actually the name in Poland. I find that interesting. Does "Bison" have a special meaning in Poland? Here, it is the name of a species of large wooly animal which once was very plentiful on the plains, and somewhat related to cattle or oxen.
Your last post was not sent to my news server - I've found it using google archives.
Because of final exams at University I would check the gearing at the end of September.
Bison means the same in my language but is written slightly different
- Bizon. There's special breed of Bison called Zubr (Z has dot over self and has really hard pronunciation for you). Zubr is quite rare now and actually inhabit in Polish forests on the NorthEast. There's a vodka called Zubrowka (mostly known abroad) ;)
With Kind Regards, ______________________________________________________________________
Jack Zagaja - photographer, designer, programmer free photoshop plugins, photographic assistance opinions and much more ... snipped-for-privacy@poczta.onet.pl
1) It had not yet gotten there (propagation speed is rather unpredicatable in newsfeeds, as is the path), and my article may show up later.
2) Your news server has a fairly short expiration time on this newsgroup, and you just didn't get to it soon enough. :-)
O.K. So we can wait until you have a chance to look at this. (Not that it matters, unless you need to cut the finer metric threads for the optical parts.)
O.K. So that explains why the factory has that name -- presumably spelled your way there.
As for the vodka -- I wouldn't know of it, because I tend to avoid strong drinks. An interesting beer, ale or Porter from time to time is a different matter -- but not too often for those, even.
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.