Thread milling is done all the time on three axis machines, it's just a simple helical toolpath using a "thread mill" which is ground to the thread form, 60 deg. included for common US threads. It is the preferred method for anything too large to conveniently tap; 3/4" or bigger.

Today, yes, but it would have been rocket science 30 years ago. At a minimum, it requires continuous sinusoidal movement on two axes, timed with continuous linear movement on a third axis. This would have been inconceivable before the age of stepper controlled lead screws.

The only possible mechanical option I can think of would be a rotating table, but that would not be much different than "milling in the lathe", and would seem to not be an effort saver.

I did not trust myself to describe the set-up thought up by our machinist, but it involved a big horizontal boring mill, and I'm sure it's the same approach as in the C&TS photo.

Regarding the idea of a plumb bob, I have seen an "Ashcroft Quartering Gage" that consists of an arm of adjustable length with a rounded point at one end that you stick in the axle center, and at the other end a V that goes over the crankpin journal. Mounted on the arm is a plumb bob that points at a scale. This device will tell you if your cranks all have the same quarter, before or after your work.

If the axles flex as much as the spring travel suggests, then how do the side rods accomodate that much flexing? I can't imagine that much clearance in the bushings to accomodate massive flexing between axles. I still don't see anyway around quartering the crank pins within the bushing tolerance. You'll never get the second side rod on. My logic tells me that exact quartering for piston timing is not necessary, I doubt the locomotive would tell the difference if they were out a few degrees, but you'll never get the second side rod on unless they are all off the same amount within the bushing clearance.

Using a plumb bob - unless you can eyeball within bushing clearance, I doubt you'll get it to assemble. A human hair is .002" and assuming .001" clearance per inch of crankpin diameter and just guessing that is 6" - you're at .006" total bushing clearance. Three human hairs - you're not going to eyeball to within three human hairs. The plumb bob string is probably .030" diameter alone.

(we used .001" clearance per 1" crank dia. on punch press rebuilds)



This is a Minster punch press (60 ton) crank that I ground for a rebuild. Van Norman crank grinder.



The assembled press.

Steve

From the 1947 Locomotive Cyclopedia.

Steve

When machining fits for steam locomotive motion work, the old rule of thumb of .001 clearance for each inch of diameter usually does not apply, especially for side-rod and main pins. the minimum clearance is a 64th and usually .018/.020 else the pin will run hot and be destroyed. This is because allowance has to be given for the wheel moving up and down and twisting in the frame as it travels over the track. The FRA and formally ICC has maximum limits of clearance (wear) and it approaches .100 and larger, check your part 230. A good source of wear limit and clearance info can be found in the American Machinist Seventh Edition-Railroad Chapter.

Even spring rigging pins and bushings have .005 to .010 clearance on pins of 1.25 to 1.50 diameter. This is to aid assembly and provide the needed flexibility for average track.

Another option:



From the 1947 Locomotive Cyclopedia.

Steve

The Niles 90", above, might have trouble doing NG wheels set. The flange is held on the bottom of the tire and there apears to be no adjustment relative to the other flange.

Since we are on the subject I'll edit and add quickly;

Do any of you know what; brand, make, model, anything, about the Quartering machine that is in the D&S shop, that came from the Republic of South Africa's SAR?

Side rods aren't one long rod that runs rigidly to all axles (unless we're talking a 4 coupled.....). They are a joined assembly of rods that each in turn couples to each wheel and through a knuckle pin joint flexibly to the stub of the previous rod......so yes, there's provision made for each wheelset to move up and down within the pedestals seperately relative to the others to compensate for the condition of the track. And, if you read closely, I not only suggest but completely spell out the need for whatever error your setup provides (and none are perfect) it must be set up the same way on each wheelset so the same error is provided to ALL the wheelsets. I also make a point that the problem comes in to play if each are different from the others.....

So, I'm not sure where you're coming from apart from perhaps unfamiliarity with the hardware.

Nice grinder.

Niles machines quarter the holes for receiving the pins. That strategy works when the pins need to be replaced anyhow, and when you have access to a Niles machine. I never have, but have trued up worn but not condemnable pins with a portable and once it is set up properly, it works very nicely.

My old friend Harold assures me that the pits in the pins are for carrying the hard grease around in the bearing.

dave

Thank you. That makes perfectly good sense to me. Pretty amazing the .100" max - I'd be afraid of some severe pounding of the bushing with that much clearance.

I have a 14th edition (1949 and about 1900 pages) of the Machinery's Handbook and there is no railroad chapter in it. By then they must have felt it not worth creating even more pages with what could be found in other publications.

Steve

As more than one old-time steam mechanic told to me, "It's better to hear the rods than smell them."

That is exactly where I'm coming from.

I've never touched a locomotive other than to climb on them. That is why I'm here. You have taught me what I didn't know before. Thank you.



Quite the learning experience running it - especially in winter and very little building heat. It was old and only marked off to .001" (I'm used to smaller O.D. grinders and increments of .0001" - Brown & Sharp #5 for example). We would get cranks that had been worn so badly that the presses would make the most God-awful pounding in their cycles. U.S. stamping industry is getting killed by cheap overseas competition and these U.S. companies would run their presses to the point of cracking frames before rebuilding them.

I'd have to guess what the stroke used to be before the ram journal had been so worn out that indicating them was like indicating an egg - wear was on the thrust side of the ram journal. I'd zero the grinder heads (head stock and tail stock had adjustable heads with chucks and about 8" of travel) and indicate the main journals (this crank grinder came with adjustable 3-jaw chucks like a Buck chuck for lathes) to zero and then run the heads out to the approximate stroke of the crank.

Indicating the egg-shaped ram journal involved a combination of rotating the crank (wack it with a lead hammer) back and forth in the chucks (leave the jaws snug until the journal was indicated in) and dialing the chucks in or out until I got the least indicator travel. If too much wear we couldn't save the cranks. We could only chrome plate them something like .060" - shoot for .020" oversize and then grind back to original size. The max we could grind undersize was like .040". If any pitting were still there after .040" we couldn't get the chrome to stay. It would flake off during use where the pitting was.

After the ram journal was indicated in came lead counterweights to offest the unbalance of the crank. Then start grinding initial passes until the journal had enough ground surface to find what direction and how much taper was in the setup. I usually had about .015" to play with to get the taper out before I was in danger of going undersize. Taper adjustment was on the tailstock end and I had to rigg up an indicator against it to measure how much I had moved the head. By simple math and ratios I could get the taper out before my stock was gone - if .003" taper in 6" of journal then .015" in 60" adjustment if the crank were 60" long.

My hair started getting pulled out when the crank would slip in the chuck during grinding. I'd periodically would double check the journal and if it had rotated on me I'd have to re-indicate the monster back in - re-touch off the grinding wheel and reset my zero. Also, grinding wheel would load up from the chrome extremely fast. I'd only leave .001" for a finish pass since anything more and the wheel would load up and my journal would measure out of round. The cold temperature was the other headache. I could literally watch the grind get heavier on a single pass (more sparks coming off the wheel) going from one end to the other of a 6" long journal. As the heat built up and the coolant/machine expanded I was chasing taper and dimensions at the same time.

There is a reason why these operations are done in temperature controlled rooms and why if they aren't - as in Mom and Pop machine shops - it can take a bit longer to do.





In the bottom photo you can see the dial indicator set up for taper adjustment on the tailstock end. The dial just below the chuck is to offset the chuck which slides on the dovetail ways visible here.

Also is the spindle lock. Both head and tail had spindle locks to orientate the heads in the verticle. If I could get both heads to lock then I knew the crank had not slipped. If I could lock the headstock but not the tail stock I knew one end had slipped and I would have to indicate the mess back in.

Also note at the very back are the half-moon shaped counterweights.

Steve

No problem. You sounded as if you knew a lot about machining, so it didn't make sense otherwise.

If you want to help rebuild one, can you move your shop to North Carolina in the next year or so? I guarantee you'll end up knowing one inside and out intimately.

dave

In the last years of steam operation at Northwestern Steel & Wire in Sterling, when an engine would come up from the scrap yard or out of the cast house, you could hear the clanking loooong before you could hear the exhausts.

You worked at Northwestern Steel & Wire?

You're not too far away from me - I'm in Rochelle.

When did they end their steam locomotive usage?

Sad state of affairs for Northwestern.

Northwestern used to employ something like 2,000 and after the bankruptcy they are down to something like 400?

Steve