Ah. I see the problem. We are talking at cross-purposes. The original question I posed was about how critical the grooves were on the pulleys for the *3M* belt (on the Taig). At that point Don N. and I were discussing how to reduce the speed of the Taig. I quoted the wooden pulley as an example of my next-to-nothing experience with making pulleys and wondering how difficult it would be to make a custom pulley for the Taig.
The RedNeck lathe is a separate issue (coming along nicely, just got its own stand and I have just semi-designed a toolpost for it).
BTW the belting on the RedNeck is part 4L (link belt - my best friend!) and the part K-profile purely because those were the pulleys on the original drill press. Given the choice they would all be 4L.
"Lenin called them "useful idiots," those people living in liberal democracies who by giving moral and material support to a totalitarian ideology in effect were braiding the rope that would hang them. Why people who enjoyed freedom and prosperity worked passionately to destroy both is a fascinating question, one still with us today. Now the useful idiots can be found in the chorus of appeasement, reflexive anti-Americanism, and sentimental idealism trying to inhibit the necessary responses to another freedom-hating ideology, radical Islam"
Bruce C. Thornton, a professor of Classics at American University of Cal State Fresno
Enough to handle sewing through leather to make thumbstraps for English system concertinas. (Granted, you are part of the feedback, adjusting the pressure as needed to maintain the speed which you can work with.
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At absolutely the lowest speed, yes it is easy to stall. If you have a foot pedal, you are adjusting the pressure to maintain the speed you want, so it is no problem.
And remember that you are also *first* using the maximum *belt* speed reduction to keep the motor's speed up a bit.
Just 13.6V or variable voltage all the way down to zero? If the latter, you can use it with a 12V drill motor to get variable speed.
A TRIAC based speed controller will need AC on the input, but a DC motor is normally also a Universal motor -- unless it has a permanent magnet field -- which you are more likely to find in a good servo motor, which is overkill for the task. So -- with a TRIAC based controller (which could include something as simple as a lamp dimmer) you want 120 VAC input, and a 120V DC/universal motor.
Likely too slow for that small a machine -- especially if you don't have a threading setup with halfnuts and a dial to say when to engage the halfnuts.
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Look at the hub diameter in the pulley data. You should be able to bore it out to fit the existing spindle. I would *never* consider turning down the spindle to fit the pulley -- always modify the least expensive and easiest to replace part.
And you won't want to be stepping up speed to the spindle, so the larger pulley will be on the spindle, thus with the largest hub diameter too.
Or -- go for the taper-lock type hubs where you can change hubs to fit the shaft once you have the right pulley.
:-)
How about 18" swing or larger? :-) It all depends on what you want to make. In this case, how large a dial do you want for your sundials? You *could* use a gap-bed lathe for that -- but there can be problems getting the gap insert back in precisely enough so it does not affect accuracy of turning close to the headstock.
I do know that I occasionally find projects which would go better with a larger lathe -- but I don't really have room for one.
Perhaps stiffer than a Variac rated to match the load, but if you have a 7A Variac or larger (I've worked with 20A 240V ones) I challenge you to get stiffer. :-)
Hmm ... that could be helpful as feedback.
O.K. That might be about the HP range needed for the Taig.
It is standing on one leg while turning I am a bit concerned about :-)
The whole thing (Singer, foot pedal etc.) has a certain attraction to it. A sort of Kalashnikov feedback. When the time comes I shall explore this concept.
It is fixed but making a solid state voltage controller is no problem. Others have put me off doing that because of the feedback issues discussed earlier.
I somehow asumed that it was not a done thing to bore out the *finished* pulleys as they make the plain pulleys that *are* meant to be bored to specs. Looking at the 57105K3 the hub is 7/8" which after boring to 5/8" ID would leave walls 1/8" thick. You think that is all right? The 6495K733 is steel and has a 1.5" hub.
The other issue I thought was that using the exisiting Taig step pulley on the countershaft together with, say, 6495K713, would lead to an ID mismatch which could not be corrected by boring alone (this one has a hub of only 1/2"). Some sort of bushing for the Taig pulley perhaps?
Presumably you are referring to something like this: 6495K222. The cost is getting up there.
Oh, about 12 feet I guess:
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But one has to walk before one can run. Also one must consider the size of the etching bath, how many gallon bottles of Ferric Chloride one would need, etc...
You put it on a lower surface, and sit down so your foot is more comfortable. :-)
O.K.
Given the current involved, you probably want to make it a switching regulator instead of a linear one to reduce the power lost as heat -- and the size of the heat sinks needed.
The larger the machine the more feedback you need -- or the stiffer a motor to start with. In this case, you are going through quite a bit of speed reduction, so you may be surprised at what the motor can handle -- especially if you go with a timing belt and pulleys for the last stage.
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You mean 57105K33? That is acetal with an aluminum hub, which would be too weak to handle that kind of treatment -- or the kind of loads involved. Steel would be better (and more expensive, of course. :-) Perhaps Acetal for the smaller end pulley, and steel for the larger end on the lathe's spindle.
Put more information about the pulleys. I'm going to have to go back to McMaster Carr's web site and print out that page.
Anyway -- even if pinned, that one is acetal on aluminum. No, go for the steel -- you get more hub to bore and to hold the setscrews.
Or -- start out with a shaft which fits the Taig pulley, and turn one end down to accept the smaller pulley.
No -- those are cylindrical bores. Look at "57095K11" -- and in particular "57095K112" which is for a 5/8" shaft. But the problem is one of finding the right timing pulleys to fit. These are for larger belts ('H' (heavy) series, not 'L' or 'XL'.)
And I would not worry about boring out the larger pulley to fit. You'll need means for measuring your bore to know when you are at the right size -- which probably means making up a sample shaft with a step
0.010" too small, one 0.005" too small, one the right size, and one about 0.002" too large. Stop before the too large will fit in. And be sure to remove the setscrews before you start boring. Hold it by the hub in the 4-jaw, and take a lot of time tuning it to on center before you start boring.
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Hmm ... I'll bet that was not made on a lathe, but rather formed up from stainless steel, and welded into shape. If it were solid enough to turn on a lathe, the supports probably would not hold it. :-)
The markings on that one were welded onto the stainless steel surface, not etched into them. As the scale goes up, the production means must change.
I thought the 57095K11 is a bushing used with a sprocket, not a pulley per se. The 6495K222 is used with 6086K14 quick disconnect bushing which is available with a 5/8" bore. But the bushing and pulley combo is close to $100. The small pulley that should match it (L series) is 6495K23. This one is steel, the bigger one is cast iron.
A telescopic gauge?
Please! I do not just copy other people's work! Well, not too often. Also, if you have a hammer suddenly there is an awful lot of nails about.
1) I *can't* run Explorer of any version on my Sun Workstation, which is what I use for browsing, newsreading, and for e-mail. I won't allow a Windows system to touch the outside net from my network. It is too easy to have one get a virus and then start spewing out spam to the world, giving my network a bad name.
2) Tabs (which I do have in the Opera browser which I use by choice) would only help if I were doing both the catalog checking and the news editing on the browser at the same time. I *don't* and *won't* use a browser as a newsreader -- I use a *real* newsreader (better than any implementation in a browser) and don't use Google for accessing news.
3) Scrolling around on the catalog page using a browser is not as easy nor as quick as printing out the catalog page and scanning it beside my keyboard. (Among other things, in the browser, I have to scroll back up to find out what the column headings are, and sometimes all the way to the top
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I've seen the same type of bushings used on timing belts, and actually *have* some on my CNC Bridgeport.
I didn't find the bushing itself, and could not see how well it would work for this task. I *wish* that McMaster Carr would make their catalogs more readily available.
O.K. Cast Iron is fine for the task. It is the softer metals like the aluminum hub, and the softer plastics like the acetal (Delrin) body which are likely to be problems for your job.
Do you have one which will go small enough? I forget whether that or a split ball-end gauge is the better fit for that size. I've got both -- plus some Tesa/B&S Tri-Mikes for more accurate bore readings.
But accurate reading of either the split balls or the telescoping gauges with a micrometer takes some experience to get accurte and repeatable readings, which is why I suggested that you make a gauging fixture which will be quick and easy to use, and especially to tell you when to start sneaking up on the final dimension.
A good stainless steel won't etch with the Ferric Chloride anyway, so you'll need some other way to attach the number markings to something of that size designed for outdoor exposure. I was talking about how it made sense to make it -- not how to copy someone else's work. You could form the letters with weld markings, or rivet them in place, or any of a number of other possibilities.
But when the workpiece is the size of Big Ben, nails don't do much good, even if you have the best hammer in the world. :-)
You can check if the tool will shave off a fraction of a thousandth while you're still a few thousandths out and can safely remove and hone it.
When I have difficulty with a fit I make the start of the bore or the shaft slightly tapered by filing or cutting steps, press the parts together enough to make marks, then cut down to almost remove those marks. Candle flame soot or marker ink makes them easier to see.
Presumably this is possible only with a QCTP without removing the toolbit from the holder? If you took it out of a lantern or a rocker you will never be able to re-insert it in exactly the same way. Or am I missing something?
OK. I have done something similar with a Sharpie pen but not in this context. Thanks.
If you hone it, you will need to re-set it anyway. The honing will change the dimensions at least somewhat. This is where carbide inserts are nice -- if you can find a sharp enough one to start with, which is a problem. You take the tool holder (with a QCTP) out, loosen the screw securing the insert, rotate it to a fresh sharp corner, reclamp and replace. This makes the change without changing the dimensions.
Grinding or honing the bit moves the edge away from the cut. You would have to reset it if you were making multiple parts but not when sneaking up on the finish dimension of the first or only one, after roughing them all.
You don't have to reinsert it exactly the same way, you remove and sharpen the bit while there is still enough extra metal left to take a fine trial cut and measure.
One of the things I was not fully aware of is that if one does three passes with the same (sharp) tool over the same area without changing anything, the first pass produces sort of peaks and valleys. The second pass will not follow the path of the first pass exactly and will flatten these peaks. The third pass will do so even more especially if done at higher speed. Thus the first measurment would catch the peaks which will not be there after the second and third pass and the measurment will be less.
I assume this is true even in a perfectly rigid system with an infinitely sharp tool. Thus the trick is to find out how much the tool will remove between the first and third pass. Was this what you were referring to in your first response?
That depends. If the feed is coming through the carriage drive or hand fed, yes it will pretty much improve things -- if the tool nose is too much of a point for the feed. If you have a sharp tool point, go for a finer feed. If you need a faster feed, round the point somewhat.
But -- if your feed comes from the leadscrew and half nuts (not present on your Taig, so that does not matter) then it will take precisely the same path and not cut the peaks left by a previous pass, but rather move through the existing valley. Your experience with the Taig involves hand feeding of the carriage by necessity. There is no other option present, so the path of the tool is going to be somewhat unpredictable no matter how closely you attempt to feed at precisely the same rate.
Note that some of the less expensive lathes do not have a separate carriage feed in addition to the leadscrew and half nuts (which
*should* be reserved for threading, not turning to minimize wear on the leadscrew and half nuts which can reduce the precision of subsequent threading. An example of this is my ancient Atlas/Craftsman 6x18" lathe.
I believe that he is assuming a slow enough feed for the geometry of the tool tip, and is assuming that you are adding a little more infeed for each pass -- especially for the next to last pass (just after honing the tool) and the last pass (also with the freshly honed tool).
I see the same effect but the reduction in diameter is well under a thousandth.
My 1965 lathe is very far from perfectly rigid. I haven't turned anything critical since I ground the wear off the bottom of the compound. Previously the compound was loose in the middle of its travel and jammed near the ends. In that state carbide often chipped and repeated passes removed fine chips randomly and changed the surface finish, using either manual or automatic feed. I thought the patterning came from wear in the feed gears.
I usually get the most even finish when the bit takes off a fairly thick chip at a slow automatic feed rate. I think the greater cutting force removes all play from worn, roughened bearing surfaces. However I can't control the diameter as closely as when alternately measuring and shaving off most of the difference.
The old books recommend a wide tool and fairly coarse feed for finishing. Apparently the long contact line stabilizes and guides the cutting edge. On my lathe a narrow point leaves a rough finish even at the slowest feed rate of 0.00078" per rev.
You could experiment with a slanted cutting edge such as the one back rake creates on the end of a right-hand turning tool. In my limited experience it may do a good job if the clearance angle below the edge is small enough to keep the bit from digging in. I don't know the proper angle, I try for about 5 degrees and then raise or lower the bit until it cuts smoothly.
Despite its problems the 10" lathe has served me well. 9" to 12" seems to be a good size for making machine parts for repairs and experiments. The controls are light and sensitive enough to make tiny things like #0-80 screws and it's capable of roughing a few inches of steel off a bar at a reasonable hobby shop rate. The 15" lathes at work are considerably less pleasant for delicate tasks. The 6" lathe I bought first was a mistake.
The concept of perfect rigidity was used purely to illustrate the point. Like the concept of an infinitely fat man it does not exist in reality I am sure.
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I think I have to learn to distinguish when to switch to such "finishing tool". I have had some bad experiences with tools that took too much of the metal.
Now I have a proper grinding set up I can have a go at making all sorts of different shapes.
Two days ago I saw a dream - 30" Russian lathe. Slightly bigger than our living room.
The 6" Sears / AA lathe's 1/2"-20 spindle isn't stiff enough to turn steel. When I got it I only intended to make small aluminum and brass parts for electronics, but then I bought a wood bandsaw that needed a new lower shaft and discovered that the lathe couldn't handle the job. If everything went well it cut the steel, however if the bit dug in from too large a cut, meaning about 0.010" deep, the whole lathe would twist and I'd have to pound the bent spindle straight again. The fix is said to be a 3/4" spindle nose like your Taig's. Maybe someday I'll finish the new spindle I started and bore out the headstock. It isn't a priority, the small lathe spins faster for polishing but otherwise doesn't do anything the South Bend can't do better, including make very small parts.
At MITRE I had a copy of the small Prazi in my lab. Again it was good enough for electronics or probably small engine models, and stiffer than the Sears, but someone before me had stripped the plastic feed gears trying to turn steel on it. It's main fault was the lack of half nuts, I had to crank the damn feed screw to move the carriage.
Lathes basically make power transmission components. A small one can do shafts and bushings but not gears and pulleys large enough to transmit more than muscle power. I think you are beginning to see how much of a limitation that is.
The jobs that push the capacity of my machines are mostly large wheels and pulleys, unplanned repairs, and special tools rather than the small stuff I originally bought them for. The money spent on machinery has come back as a front end loader and a sawmill nearly for free, also the abilities repair for $5 instead of replace for $500, to own things I can't buy and to strengthen the weak failure points of the current value-engineered commercial products. Often these are plastic pivots that I replace with stainless steel TIG rod, turned down to fit and threaded for retaining nuts.
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