rack and pinion

The only ones that I have ever seen with the double helical are the Macro-Zoom lenses, and the double action was switched out unless using the macro function.

The reason for the multiple lead is that it holds the lens more square to the body than a single lead of the same lead pitch would. Much closer tolerances are easily held than would be the case with a coarser single lead.

I'm not aware of any photo/visual being made with a helical focuser, if a camera is going to be used, it's normall in a rack and pinion focuser. I don't ever remember seeing a helical in any refractor, other than in the finder scope, almost always rack and pinion. (Even the Yerkes 40" Clark, which I've had the priviledge of having a 30 second peek through it. Absolutely, completely, totally spoiled for life. Open house at their centenial, but only using about 700 diameters magnification. somewhere between 300 to 500 people got to look through it during the course of the night.)

Reply to
Lennie the Lurker
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I doubt very much that there is a telescope that is so bad that I can't learn something from it. Galileo discovered the moons of Jupiter with a much worse scope. Tycho Brahe didn't even have a telescope. Neither did Ptolemy, whose 2 millennium old astronomical contributions are immortal and can still give an amateur plenty of work to do. I may wind up agreeing with you about this scope, but not until after I have made every effort to get something out of using it and examining it.

The person who loaned it to me is pretty competent in astronomy and I have a lot of confidence in him. The manual says one can see cloud belts on Jupiter, the Galilean moons of Jupiter, Saturn's rings and some of its moons and lots of details of the Moon. That's not a bad start. Meanwhile, the scope didn't cost me anything and I'm up for the experience of using it, good or bad.

Even the low level routine of setting up a scope and finding something in a finder scope and training the main scope on it is more than I am currently competent to do. If I only get that much out of it, and even if the images are lousy, I'll be ahead of the game. Part of finding stuff without computer control is having a certain amount of experience with the general layout of the sky without a scope. That's also something I don't have and I expect I'll get a lot of practice with it trying to use the scope. So what if I can't see anything as long as I walk away from the experience stronger for having tried? That's really all I care about.

Which reminds me: is it better to get one dinky Unimat1 now and be able to use all of its component machines, or get the admittedly much better Sherline lathe now and have to wait perhaps several years to get the Sherline milling machine? I'm finding it a tough call, not unlike the issues raised above. If I could get the Unimat1 immediately for free under these circumstances, I would take it and benefit from the experience of using it. It's the same with the telescope.

I already go out with binoculars to look at the sky. This scope's a lot better than that.

Reply to
Allan Adler

Allan, the lens mount you describe rules out a deparment store scope, what you have is a much more expensive instrument. Meade has, and does, import some rather poor scopes, but they also have their higher lines, which are quite good.

Here's a quicky test for the mounting of the lens, pick any star, move the focus until you get a blurry dot. If it's round, the lens is mounted square, it it's an oval, the lens needs to be collumated, and the axis that needs adjusting is 90 degrees to the shorter axis of the image. They will interact, and it can be a long and frustrating process to get the dot round. For visual observing, perfection is not needed.

If you can get one for free, go for it. Don't even think about it, you can learn a lot from the Unimat. For a step up from the Unimat, I would say the Taig, rather than the Sherline. Both have their limitations, but neither of them has an advantage in the quality of the work they can do. The quality of the work depends more on the hands on the machine than on the machine itself. If you can get one with all the attachments, much the better, the only limitation in what you can attempt will be in the size of the work. For small work, and learning purposes, they're excellent little machines.

Reply to
Nobody

That's good to know. The guy who loaned it to me told me that one can scopes like this one for about $150.

I was wondering how one could test for that. Thanks.

Based on my experiences examining the scope, I had to ask myself: "What if I loaned my scope to some bozo who decided to educate himself by taking it apart and putting it back together. How could I develop a set of procedures for checking everything the bozo could have messed with and, in case it has been modified, for bringing it to a "standard" configuration. Every scope is different, and it must depend on the scope. But I'll have that question in mind when I look through the books you suggested.

Thanks for the advice.

Reply to
Allan Adler

I looked in my optics books and didn't find "optical comparator", so I did a google search and found some information about it. Based on that, I'm wondering whether an old microfilm reading machine I fished out of a dumpster could be adapted for this purpose. It's housing is made of wood, the optics are in metal and it is intended for strips of microfilm, but I did manage to look at some crystals with it. It's a piece of junk but I've been reluctant to give up on it. The point is moot at the moment since it is in storage where I can't get at it, but I expect that situation to change. Even so, I'll need to acquire more practical knowledge about optics than I have at the moment before tackling it. This would be a lot cheaper than buying a comparator, I think, which would probably cost more than a new scope. But I'm looking forward to trying out this comparator idea for checking out the rack.

Reply to
Allan Adler

"Kelly Jones" described very clearly and in great detail how I could make a thorough check of the condition of the rack and pinion on the telescope. I just have a few questions:

Is there some kind of common coloring one can mix with with "any good grease" to simulate the stuff the professional gear guys use? For example, how about adding a tiny bit of alizarin crimson or emerald green oil paint to the grease?

Reply to
Allan Adler

Your'e unlikely to find them in an optics book -- but a well-equipped machine shop is more likely to have one.

Those tend to have more magnification, and less depth of field than an optical comparator for machine shop work. Also, the screen tends to be a bit awkward to get to to add a transparent sheet to draw on. The one I have apparently came with optional lenses for 10X, 20X, and 40X, but I only have the 20X lens.

A proper one has a collimated illuminator, a stage on which the object under test resides (with X and Y motion to move the viewpoint, plus Z for the focus. Usually, there is a way to measure the X and Y motion -- either with big micrometer heads to move the stage, or with dial indicators to measure the motion.

However, there are minimal ones which are handheld, including a set of reticles to measure various things including small threads, and angles, an eyepiece, and a tube to join them. eBay auction #3855942073 has a set of reticles, but not the eyepiece and tube. I'm not sure, but I think that the price there is a bit high.

Reliable tools has a nice looking one up for auction #3856418973, but it's heavy (300 pounds), and is certain to go higher, as there are over four days left.

There is another by Nikon which is still within reason, and it suggests an alternative name "Profile Projector" for the equipment. (Auction #3856039570).

I don't see any of the lightweight ones like mine -- it *looks* heavy, but is mostly blown plastic shell and a wood base. The size is necessary to get enough optical length for good magnification. Note that it *will* take up a lot of benchtop space.

Try eBay searches for "optical comparator" (with the quote marks) and one will show up sooner or later. A reasonable price is somewhere in the $200-$300 price range. Unfortunately, this type is not there at the moment. Note that the same comparator shows up in the MSC catalog and in sales flyers for significantly more -- reasonable for a business, but not for a hobbyist. The brand on mine is "Micro-Vu", and the one on the MSC offering is Fowler, IIRC.

If you want to try to make one, the general design involves:

1) Illuminator on one side of the stage (or below it with a transparent stage). (Plan on something like one of the Quartz Halogen projector lamps in their own parabolic reflectors so you have adequate brightness for good visibility in a well-lit shop. Remember that the more the magnification, the less the brightness remaining. 2) Moving stage for the device under test.

3) Lens to focus the image onto the screen.

4) Angled mirror in the back to bounce the image back and up towards the screen.

5) Round ground glass screen with reference lines (cross hairs plus angle lines and radius lines engraved in the glass, and filled with black paint.

6) Ring surrounding the ground glass screen, with a full 360 degree angle scale on it, and a vernier scale adjacent to it to allow measuring to fifteen minutes or so.

7) Spring fingers (similar to those which hold slides on cheap microscopes. These are used to hold the transparent films, either for hand drawing to compare worn and unworn teeth, or printed in a plotter from a computer, or photographically printed, to compare new parts to their designed profile for quality-control inspection.

Good Luck, DoN.

Reply to
DoN. Nichols

Allan, as so often happens in this group, most of them have gone off the deep end again.

You do not have to do a pattern check on the rack and pinion, that is for precision gearing, and precision gearing is not found in focusers under the $250 range. THe pinion is probably cut from extruded pinion wire rather than being a cut gear. The rack, if it's a gray metal as you describe, is die cast zinc, and no degree of precision there either. It simply is not needed. The optical comparator is massive overkill, just looking at the teeth with a good hand lens will show the problem if it's bad enough to cause a real problem. The racks and pinions in my old Edmonds are now over thirty years old, were never the epitome of quality to begin with, and don't cause any problems in use. If I were using one of the remote focusing units, the backlash might be a problem, but as I focus "eyeball to the eyepiece", it is not.

Lube, I lube the drawtube, but grease and oil only attract dirt to cling in the rack, so mine runs dry except for the shaft and the drawtube itself.

My final advice, put it back together, take it out and use it. If nothing else, it will give you far better views than the telescopes of Galileo, Herschel, Newton and others. IF the drawtube moves when you turn the knob, it's doing what it's supposed to do. A lot of time can be taken with technicalities, without looking at practicality. And already has, the prime question is "can I get this thing in focus", and if the answer is yes, going deeper into it is only wasting time and money. Your time would be better spent in a dark place, with the scope, even just sweeping starfields to see what is there that you can resolve with the instrument.

Have fun.

Reply to
Nobody

I have a spare Micro-Vu that Id let go really cheap. Screen is in excellent condition, but the light source was removed for some reason. Power transformer is fine as is the staging. Might be a good place to put on a nice bright LED light source. No dial indicators, clamp your own on.

Gunner

"I mean, when's the last time you heard of a college where the Young Republicans staged a "Sit In" to close down the Humanities building? On the flip side, how many sit in's were staged to close the ROTC building back in the '60's? Liberals stage protests, do civil disobedience, etc. Conservatives talk politely and try to work out a solution to problems through discourse until they believe that talking won't work... they they go home and open the gun cabinets. Pray things never get to the point where the conservatives decide that "civil disobedience" is the next step, because that's a very short route to "voting from the rooftops" Jeffrey Swartz, Misc.Survivalism

Reply to
Gunner

[ ... ]

Or build one around one of the Quartz Halogen projection lamps with built-in reflector. Some of them (usually marked 82 V IIRC) are designed to run from the AC line fed by a single rectifier diode. No big transformer to deal with. But then again, the transformer in the back helps counterweight the optics, stage, and lens at the front.

Of course -- but provisions for mounting them. I've put a 5" travel one on the X-axis on mine.

Out of curiosity, do you know which lens yours has?

Enjoy, DoN.

Reply to
DoN. Nichols

Off the deep end? Perhaps. But the original question was about how to check the rack and pinion, not whether it should be checked. I appreciate you pragmatisism, but it was still fun to describe how to do a pattern check. Whare's your sense of humor? :)

Reply to
Kelly Jones

My sense of humor disappears very quickly when it goes from the realm of the ideal to the realm of the ridiculous. A patten check on the hypoid diff gears that I used to do by the dozens is one thing, on a rack and pinion, where the rack is die cast and the pinion extruded is senseless. I could have gone into the whole nine yards of a gear lab check, but to what end? In this particular application, if the spur gear has .0002" helix, and the involute error is .001", what's the difference? Even pitchline to pitchline makes no difference here, the pinion is crushed into the rack for full engagement by a spring, and the relation of the pitchlines really don't mean squat. DP of the rack and pinion is going to be probably 32 or finer, you're looking for errors that are going to be in ten thousandths, and even if they're found, they won't bother anything. Even my 35 year old Edmonds, the focusing isn't perfectly smooth, but it doesn't make one bit of difference, it still works just fine. There are some focusers out there that are perfectly smooth, or as near as is possible, but at $300 or so per copy. To what end? The mirror in my 10" f8 cost me $350 for figuring and coating, I don't think a $300 focuser is going to make it work any better. It has an off the shelf Boston rack, and the pinion cut from pinion wire. Works just fine, and a hell of a lot cheaper.

Why complicate things?

Reply to
Nobody

Not at the moment. Ill have to dig it out and look. I believe the magnification is 10x IRRC but which lens..no idea. It has the standard MicroVu screen and grid pattern.

Frankly its in my way, and Id like to see someone get it.

Ive a minty 12" Dorsey OC in my back office that I use and I understand that Ive just been bequeathed a Sony (? its orange) floor model with DRO. ("Its in my way..come and get it..we just got new CMMS and Mitys"...click)

Gunner

"I mean, when's the last time you heard of a college where the Young Republicans staged a "Sit In" to close down the Humanities building? On the flip side, how many sit in's were staged to close the ROTC building back in the '60's? Liberals stage protests, do civil disobedience, etc. Conservatives talk politely and try to work out a solution to problems through discourse until they believe that talking won't work... they they go home and open the gun cabinets. Pray things never get to the point where the conservatives decide that "civil disobedience" is the next step, because that's a very short route to "voting from the rooftops" Jeffrey Swartz, Misc.Survivalism

Reply to
Gunner

In all fairness to Kelly Jones, I did ask for how one would go about taking a fanatical approach to the wear on the rack and pinion. And I did find his reply interesting and informative, just as I found yours to be. I'm not really in a position to carry out his suggestions at the moment, and you're probably right that it isn't necessary, but I like to know how to do things, even if they're not appropriate to the task at hand, as long as I'm not under extreme time pressure to get something done (and with the weather the way it's been, there's nothing to look at in the scope anyway for the time being). Similarly, I realized that I probably don't need to buy a comparator, but it was good to learn about it, since I'd never heard of it.

As long as there was one person who was telling me exactly how to handle the specific situation I was asking about, there was no real harm in getting supplementary information from others that was not immediately applicable. In the absence of that specific information, it would have been a different story, but I think I can tell the difference between what is immediately applicable and what isn't.

If you don't mind, I'd like to ask about of your other comments, namely about the Taig lathe. I had never considered it and didn't know anything about it. I just took a look at

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I see that the basic Micro Lathe II only costs $173 (or only $144, if I can assemble it myself, which I'm not sure I can do), and I think I saw somewhere that shipping is free if I buy it online. That's pretty tempting, but I may not realize that there is something else I would obviously need that would raise the price by a lot. I see that their milling machines are a lot more expensive.

I learned about the Sherline by reading Joe Martin's book, Tabletop Machining. I see that the Taig website lists a book by Tony Jeffrey, entitled, "The TAIG Lathe". Would it be a good idea to purchase this book before committing to getting a Taig lathe?

They show it with optional 3-jaw chuck, boring bar, tailstock, drill chuck,

1/4 HP 1725 RPM motor, motor mounting bracket, mounting board and pulleys for $399, presumably with free shipping for online purchase, which is less than the Unimat 1 comes to after taxes and shipping are added. Hmm, the motor is optional, as in no motor with the $144 deal?

Of course, the Unimat 1 comes with the other stuff (notably the milling machine attachment), but one can't go too far wrong for $144, can one, as long as it works, and the other stuff can wait a little while.

It's also probably easier to learn something by taking the Taig apart than a Unimat 1...

I've decided on the first thing I will do when I finally get a lathe: I have a T-connector for my Minolta XG-1 camera (which, even with its apparently broken internal LEDs, is adequate for taking photographs through my microscope), and an adapter to connect it to my microscope. Now that I finally got my hands on a telescope, I tried to see if the adaptor would work with the telescope and, of course, it doesn't. But if I can machine a 1.25" O.D. tube to have a somewhat smaller O.D. near one end, I can use it as an adaptor adaptor, with the telescope eyepiece holder grabbing onto the 1.25" O.D. end and the camera-microscope adaptor grabbing onto the smaller end. This seems like the absolutely simplest first project one can do with a lathe, and I have an immediate use for it.

The following is probably a bad idea, but it would be instructive to try out. I have a few eyepieces for my microscope. They are intended to fit the microscope barrel, but again it wouldn't be hard to make an adaptor that would let me insert them into the telescope. That is another very simple lathe project. Whether these eyepieces would be any good with the telescope is something I could then try out. Probably they wouldn't be, but I'd see for myself. The next problem would be to learn why, from the standpoint of optics, I should never have expected it to work in the first place. But there is a kind of information mismatch. The microscope eyepieces are only marked with their magnifications, such as 5X, 10X, 15X, while those for the telescope are marked with their focal lengths, such as 15mm,25mm,30mm. Even if the viewing isn't good, maybe I could wind up using the telescope to measure the focal lengths of the microscope eyepieces. In the absence of any optical equipment for doing such measurements, the idea of using a telescope as an optical lab bench is rather tempting, even if somewhat ridiculous.

Reply to
Allan Adler

The basic Taig is just that, the headstock, bed and carriage. Everything else is an extra, But it's still possible to have a complete lathe, with all accessories for under $500. IN the micro lathes, between one and the other, everything is different. The chuck for the Taig comes with soft jaws, which means, you have to learn to bore them. Not really a negative, but on the flip side, getting concentricity to where it's almost to little to measure is relatively easy.

By all means. I haven't seen the book, but often a look at what someone else has done makes what you want to do much eaiser.

Maybe Nick Carter will jump in here, he sells them and is very knowledgeable on what people are doing with them.

Right. The package sounds very good, although I bought mine piecemeal, which probably cost me more in the end. The shortcomings of the machine show up, but by that time, you'll probably be far enough along to recognize them, and have an idea of what to do to clear them up. (There is no "perfect" machine for everythng.)

One thing they don't push very much, the collets for it, this is something I bought quite some time after I had the basic machine and enough of the extras to make it work. They are invaluable when you have smaller diameter work, 5/16" is the biggest collet they have. Mine ran dead true and held like a bulldog.

The instructions for assembling the kit sound somewhat simplistic, but that's really all that's involved, it only takes a few minutes, well, less than an hour.

THis would be a very good project, not too much involved, but enough to learn from it. One of my buddies put a University mirror cell in an Oddesy scope, which moved the mirror forward almost 1 1/2", and no focuser has the reach to make up for that. Making an extention tube to move the eyepieces out was a relatively simple job, the Taig did well.

I've always had that idea, but have never acted on it. THe eyepieces are of a much different design from telescope EP's, and probably something is going to have to be done to compensate. IIRC, the focal plane of the microscope EP is between the lenses, but that's looking at older units. I have quite a few 10X and 15X wide field AO eyepieces, but as they're in scopes, I'm somewhat reluctant to risk taking them into the field. I spent hours going through a drawer of hundreds of eyepieces trying to match pairs, losing one of them would mean I couldn't find another to match it. I don't know any reason that they wouldn't work, and probably pretty well.

Reply to
Nobody
[ ... Micro-Vu optical comparator ... ]

O.K. That screen has markings for three magnification ratios,

10X, 20X, and 40K IIRC. Mine has the 20X lens. (No real markings on it, you need to measure something of known dimensions to tell what you have.

Well ... you are a bit too far away to make this practical, or I would be very tempted. :-)

Thanks, DoN.

Reply to
DoN. Nichols

It makes sense that someone would purchase a complete lathe with all the accessories. If they already had accumulated some of those accessories from earlier acquisitions, it would make sense that they might forgo some of them when purchasing a Taig. It would then make sense that Taig might accomodate them by offering lathes without the accessories. But I'm not sure under what circumstances someone (other than a complete beginner like me, who doesn't know any better) might purchase a minimal $144 Taig that doesn't even have a motor. Is there a significant part of the market represented by people who already have a supply of motors?

I've been thinking about this statement and there are two things you might mean by it. (1) You sometimes take your eyepieces apart to scavenge the individual lenses to recombine them in ways you find more advantageous. I know from experience that they come apart, and I also found a website (e.g.

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that tells you how to make your own telescope eyepieces, so this isn't unthinkable. It's another thing I was considering playing with when I get some machines. I'm not sure but it sounds a lot cheaper than buying eyepieces. (2) You have a binocular microscope and you need identical eyepieces for each eye. In the latter case, it sounds like you have all the eyepieces loose in the drawer but not grouped in matching pairs. If you had enough little boxes, you could group together all the ones that have the same magnification and not have to spend hours looking for matching pairs.

Regarding the threads on the threaded metal shells that hold individual lenses in an eyepiece, are these threads that would be easy to duplicate with standard tap and die sets or is there something special about them?

Reply to
Allan Adler

[ ... ]

[ ... ]

The only taps which are likely to be usable for that sort of thing would be the collapsable taps (sort of inside-out Geometric die heads) used on turret lathes or automatic screw machines.

Optical threads of this sort are *very* fine relative to the diameter. The reason for this is because they typically screw into thin-walled cylinders, and fine threads are not as deep as coarse threads.

And you wind up with really weird bybrid threads. IIRC (and I could well be wrong) the standard thread for microscope objectives is

0.800" x 0.5mm (Inch diameter and metric thread pitch).

For production, you would use a collapsing tap to cut the inside threads, and a Geometric die head with custom chasers to cut the outside threads.

For onesy-twosy work, you would single-point it on a lahte, which means (if you get a Taig) that you need to investigate Nick Carter's mod which gives it threading capability.

Normal taps and dies are difficult to start square without some kind of machine support helping you. You *could* have any special tap and die made for you by the companies which make them, but it would cost you quite a bit, and you still have the problem of getting them started straight. And if you don't get them started straight, you have lens elements tilted relative to the axis of the equipment, thus offering optical abberations.

I think that if you are going to be doing much of this sort of thing, you want to look for a dual-system lathe, with threading setups for both Imperial and metric threads. (To do this properly means two leadscrews with matching threading dials, and two quick-change gearboxes to provide the proper ratios for the different systems.)

It is possible (with a set of transposing gears) to cut metric threads on an Imperial machine or vise versa, but it will be a serious pain, as you can't disengage the half-nuts until the thread is complete, with however many passes it requires.

So -- while I have the Metric transposing gears for my Clausing, as long as the size can be handled by my little Compact-5/CNC, I will use it for metric threads, as all I need is to flip a switch to change systems. (And even then, the 0.800" x 0.5mm thread would require setting it up for metric threading, and converting the 0.800" to mm before programming the machine.)

Enjoy, DoN.

Reply to
DoN. Nichols

Taig also sells the motors, but most people just use a scavenged motor from an old washer, dryer or whatever. 1/4 horse is plenty, I ran mine on 1/6 horse until I got tired of having to lift the whole thing, and the old motor was from 1937, HEAVY! Changed it over to a 1/12 horse scavenged from an old Bodine gear motor with the gear broken. If you can get a slower motor, maybe 1140 RPM, it would be better. Don't know if they're available on the surplus market or not.

Bingo. Actually 5 binocs, two trinocs and a whole bunch of monocs. I like old things. Maybe too much. Matching them for power isn't too bad, but making sure they have the same aperture is where it gets fun, you have to hold the pair to your eyes, then swing the fields until they come together, they should be the same. (But usually aren't.) I don't have a good supply anymore, but used to work with J&H microscope on mods and accessories. You can get into some really wierd stuff.

Most of them that were made in the US had an unwritten standard of 40 threads per inch. Sometimes an odd ball of 36 TPI, but usually 40. Metric, I don't know about, I've been out of the attachment making for about ten years now, They're usually not included in the normal tap and die sets, but most of the supply houses will have them. The objectives, with only a very few exceptions, are .800"-36 TPI, 55 degree Whitworth threads. Most of the supply houses also have taps and dies for this as well. Prices are pretty reasonable.

Reply to
Nobody

If I recall correctly, there was something called a Frog which could control a Taig, and would do threads under program control. Yeah, here it is

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I considered trying that, but wound up getting another lathe with threading capabilities before I ever pulled the trigger on purchasing a Frog.

I kept the Taig, and still use it for a lot of little fiddly projects. It is excellent for small work. But threading jobs go on one of the other lathes, or get handled by taps and dies.

Adding a Frog still looks like an attractive way to upgrade a Taig to

1 axis CNC. With 2 Frogs, you could do 2 axis CNC (the Frogs can talk to each other, so interpolated taper and radius turning would be possible in addition to fully automatic multipass threading). At $199 each, that's starting to cost real money, but it is still a lot cheaper than most CNC retrofits.

Gary

Reply to
Gary Coffman

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