3/4" Raritan 2-4-0 build.

[NP317]

With what slipping?
Not a clear question.
RussN

[Greg_Lewis]

Shild:
As to rigidity, not a problem. Use a live center on the tailstock and a dead center on the head end. It's as rigid as the late is. I'm also not sure what you mean by slipping. You would make up a lathe dog like the one in the photo below to drive the axle assembly.

external-content.duckduckgo-1.jpg (16.03 KiB) Viewed 5149 times

[Harold_V]

If the bore is off so wheel wobbles side to side a couple thousandths, doesn't that clean up since the wheel tread and flange is done on the arbor?

Yes, it most likely will clean up, but that's not the point. What you're proposing is poor practice. Once mastered, doing things right generally takes no longer than doing them wrong, plus you lower the incidence of making scrap immeasurably. Beyond that, lets assume that you've spent a great deal of time aligning the wheel face so when it's finished, the cast surface relates properly to the machined surface. If you alter that condition with an irregular bore (and you most likely will), you may lose the appearance you strived to perfect. That may or may not be a big deal, but it's important that if you're trying to learn to do work like this, that you learn acceptable procedures. That was one of the most difficult things I had to overcome as an apprentice. There are proper ways to do most any operation. They are considered proper because they yield reliable results, they are safe, and they are cost effective. That is not to say there's only one way to do things. There may be many, but you shouldn't concentrate on those which yield questionable results because, in your mind, they're faster. Try to avoid the trap whereby you don't have enough time to do a job properly, but you have all the time in the world to do it again when the first attempt fails. Said another way, practice being a winner, not being a loser.

I've seen engines with wheel wobble and thought it might have happened when the wheel was pressed onto the axle.

That's certainly one of the possibilities, and it is greatly exacerbated by home shop types who use poor practice. In many cases, the bores have been reamed. A reamed hole is often not straight, and can be off location. Why would you expect perpendicularity from the wheel when it's not made that way? What makes sense is to use procedures that yield exacting conditions. Minimize the number of errors, so, when assembled, the chance of being correct are improved. It makes no sense to make parts which are not properly machined, then to expect the assembly to be proper.

In regards to pressing finished axles in finished wheels. It can be done, and with excellent results. Trouble with doing them in the home shop is that all too many use a reamer instead of boring, so the bore is neither round nor straight. Couple that with a press fit that is generated on a lathe by a less than well talented individual, where the size is irregular and often excessive. The final nail in the coffin is when the axle is pressed in to the wheel without taking necessary precautions to align the axle vertically, then to press at an exact right angle. One does NOT rely on the hole to straighten the axle. By contrast, a bored and round wheel and a precision ground axle with the precise amount of press fit, coupled with a proper press and some means to align the axle dead vertical, there's no reason why the assembly can't be true. They generally aren't because the home shop has few, if any, of the capabilities required.

I've got another question about good shop practice. I'll want to make a hole with the mill/drill so after I've marked a part with a caliper and put the part in the vice I'll lower the mills head with a center drill until it just barely touches it then raise the head back up so I can see it better and check. I'll usually be satisfied but when I lower the head again to drill with the center drill much deeper, as it loads up the head nods up under load a little so hole ends up a few thousandths closer to me than I had hoped. The gib for the head is tight. What can I do about this?

Wow! So many things I wouldn't do!
I won't bother commenting on the use of a caliper for marking location. However, it does bring to mind the idea of using sand paper to clean the dirt from the paint on one's car.

Are you familiar with edge finders? Do you have a DTI (dial test indicator)? Either can be used to locate a position on a part, although a DTI may be restricted to smaller parts. An edge finder is quite convenient, not expensive, and, in the proper hands, very precise. One hell of a lot more precise than scribing a line with a caliper, then picking it up visually. In fact, there is NO need to scribe a line in the situation you described. Machinists rarely work to layouts. They use dials or DRO's, assuming they are manual machinists. If you MUST work to a scribed line, a wiggler is a much better tool at picking up the line.

Machine deflection under load. Not a lot you can do about that. It's best avoided by not using a light machine, or using a machine better suited to the assigned task. If you have nothing else at your disposal, and no prospects of improving what you use, then you must modify how you do things. When location is critical, you must use light pressure, which you can do by step drilling, so each drill removes little metal, lowering cutting pressure, or, even bore after opening up a small hole. Boring pretty much eliminates any deflection due to the light cuts involved, plus boring will correct errors, much the same way boring corrects bores in wheels before reaming.

You may wish to explore methods of improving the rigidity of your mill/drill. Entertain ideas like adding supports so the head can't nod. Such devises were commonplace on horizontal mills.

You commented that this forum is your "night school". That's well and good so long as you are asking the right questions, but, more importantly, getting good answers. As much as it pains me to say this, learning procedures from those who are self taught can be troubling. Likewise, learning procedures from one who has experience in the machining trade, but is poorly skilled, can be equally as troubling. It's up to you to determine who amongst those who offer guidance are offering acceptable procedures. That includes me. You have no way of knowing if I'm a blowhard, or a well talented and qualified individual, and there's likely no shortage of folks who would openly disagree with many of the comments I make. The casual observer (folks with little experience) have no way to know which one is correct, or if either one is.

Many have mastered the home machining process and have turned out exceptional work. It can be done. Just make sure you're source of information isn't leading you astray. Many delight in doing so. Promoting questionable practices? I'd avoid 'em!

H

[Bill Shields]

That is the idea of a proper press fit and light truing cut

[NP317]

shild:
We are most fortunate to have a Master Machinist share his knowledge with us.
I keep learning from Harold, because he chooses to offer us his advice, from decades of proper shop practice.
Thank you Harold.
RussN

[Greg_Lewis]

I think I've mentioned this before, but it's also important to know when accuracy to .001 is important and when it's not. I remember when I was about 17 and had no shop tools. A friend had a small bench vertical mill and I needed something done. The first question he asked was, "How accurate does it need to be?" I've never forgotten that. There are lots of parts I've made that are just cosmetic and thus no need to be closer than eyeball good. I zoom lots of this kind of stuff out on my bench disc/belt sander. OTOH, when it's time to get out the edge finder or the tenths mic, I do that, too. And when I was beginning, I often worked to .001 even when not needed just for the practice. And it does take practice. (I just found an old box of shattered end mills hiding under the workbench. )

[Harold_V]

I often worked to .001 even when not needed just for the practice. And it does take practice.

I couldn't agree more. For those who think that fine work is no different from hack work, you are in for one hell of a surprise when you are first called upon to hold a tight tolerance. Success comes only by chance with that approach, and is often a compromise of the desired target. As an example, when a dimension is held to tenths, surface finish becomes critical, as one does not hold tenths tolerance with a 125 surface finish. It simply can't be done, because the measurement has no value due to the irregular and easily disturbed surface.

Working to a thou demands a totally different approach to metalworking, and tenths even more so. As crazy as it may sound, one can't even touch the table on a grinder in operation for fear of altering size. That's all a part of knowing and applying good shop practice.

Those who (successfully) do critical work have a totally different way of working from those who do not. If you don't practice working in that fashion, you'll struggle endlessly when called upon to do so, and you can rest assured, that day comes. NO ONE can do shop work and not eventually have to hold a tight tolerance. Bearing fits come to mind, as do proper assembly fits (press or slip? ------A half thou makes a HUGE difference in either).

Installing a drill bushing? A couple tenths too much press and the bushing will now be too tight for the drill or reamer. Get the idea?

I encourage those who are trying to learn to hold all dimensions to nominal. Needless to say, I am not suggesting everything be polished to a tenth tolerance, but work to the nominal dimension as habit--so when you must do so, the procedure is routine, and you'll achieve success by design, not chance. Funny thing is, when you work this way, with time you become just as fast as the hack is---but your quality is far superior, and your rejection rate is much smaller. A win/win situation if there ever was one.

H

[Harold_V]

shild:
We are most fortunate to have a Master Machinist share his knowledge with us.
I keep learning from Harold, because he chooses to offer us his advice, from decades of proper shop practice.
Thank you Harold.
RussN

Careful, Russ. I may be one of the blowhards I mentioned. You can't really tell!

Thanks, anyway, for the glowing remarks. I just hope some of my ravings help those who struggle, or hope to better their ability on the machines.
I'm just trying to repay the good that was given to me by those who went before me.

H

[NP317]

Harold:
I have worked professionally with several suburb machinists.
Your advice is directly in line with theirs. I am listening.
Point made.
RussN

[RET]

Hi shild,

Being a relative newcomer, you don't have a history on chaski. Since I have been watching and contributing for at least 15 years now, I can tell you that Harold is definitely one of the ones to listen to. As has been said, we are all fortunate to have him as a moderator and contributor. If he ever decided to go elsewhere, we would ALL lose.

I have been a member of TSME (Toronto Society of Model Engineers) since the 1960's. I have been interested in making things all my life, but when I joined TSME and saw what the members did, I figured the best thing I could do was to say nothing and just learn how to do the things they did. Over the years, I learned a lot from the other members. Without exception, they were always quite willing to show and tell how they did things and later on I felt that some of the things I was doing were worthy of demonstrating and talking about.

One of the things from the TSME meetings I remember is a setup that Bill Huxhold brought to a meeting in the '70s. It was a jeweller's lathe to which he had added a carriage, cross slide, tailstock and a binocular microscope so he could see the little nozzles he was machining for a customer.

Bill's work was always very precise and everything worked just the way it was supposed to. He made working models of marine engines, mill engines, a working electric torpedo with counter rotating propellers complete with a submarine to fire it by compressed air and would research his projects for a long time before building anything. With the submarine, he made the torpedo first (cigar sized) and then he figured that he needed to make a radio controlled submarine that submerged and surfaced to fire it from.

He made his own fasteners (nuts and bolts) and the biggest ones were #0-80 (the size you have in eyeglass hinges). We were always impressed by his work, but when he told and showed us how he did things, he made it sound SO simple!

One of the things I'm always conscious of is that chaski isn't just a local meeting place for "a bunch of the guys," but that anyone anywhere in the world can view anything that is said, so I for one always try to make sure that what I say is always correct to the best of my ability.

Harold is correct, don't worry about speed, it isn't important. Spend your time learning how to do things the right way and try to work accurately. If you try to rush too much you will find that as your skill level increases, you will find yourself going back and remaking the first parts you did because they aren't good enough.

Something else you need to think about. Harry Hawkins (another TSME member I learned a lot from) told me that if you know what you are doing and don't make many mistakes, it takes about 2,000 hours to build a generic steam locomotive and if you want it to look like a particular locomotive, you can more than double that time. Over the years, I have come to the conclusion that he is pretty close to being right.

I guess that's enough for the moment.

Richard Trounce.

[shild]

Thanks for the replies guys! Going to take me a while to digest all that. Anyway here is where I'm at now, ground down the high spots on the chassis from the spot welder, about to put several coats of primer on it, will probably get a can of "High build primer" and brush paint it into the low spots caused by the spot welder then block sand it. Made the mistake of not making enough clearance in the frame for the coupler to turn enough, but Waushakum doesn't have sharp curves so I'll live with it for now and glue the end piece on incase I ever need to go in and file it.

[NP317]

I would correct that slot clearance now while it is easily accessible.
I've tried to shortcut some things in the past and paid for it later.
Not a recommended way.
Grab a proper file and have at it now.
RussN