[How do I?] Help Me Build My Bogies

[Robo_Pi]

Hi everyone, I'm starting out on a new project to build railroad bogies in #1 or G scale. I'll need some help from experienced machinists.

This is my drawing of what my finished bogie will look like:

The Bogie



I'm going to start by making the wheels and axles. The axles will be 0.125" stainless round stock. The wheels will be made from 1.5" Aluminum round stock as shown in the drawing below:

Wheels and Axles


My FIRST QUESTION on PRESS FIT HOLE SIZE:

What size drill will I need to use to get a nice "press fit" for the 0.125 axles?
I want the axles to just press into the aluminum wheels and stay put. Also will I be able to just drill this hole, or will I need to buy a reamer too? The aluminum wheels are 0.250" thick and 1.5" max outside diameter.

I'm planning on cutting a recess on the face of the wheel for cosmetic purposes as shown in the photo below:

My SECOND QUESTION on HOW TO SHARPEN LATHE BITS:

What angles should I use on a H.S. steel lathe bit?
I'll be grinding my own tool bits from scratch using 1/4" tool bits. I'm planning on using a round-nose to do this concave recess, but I'm not sure how to sharpen this bit for best efficiency at cutting aluminum?

Recess


Finally I drew up a picture of how I'm currently planning on doing this whole operation.

1. First I'll drill the center hole.
2. Then I'll cut the cosmetic recess
3. Then I'll cut the flat on the wheel that will actually ride on the tracks along with the angle for the flange at the same time.
4. Finally, I'll use a 1/8" cut-off tool to cut the finished wheel off the aluminum bar stock. The back side of the wheel can just be flat.

My Machining Plan


Just wondering if this sounds like a good plan and if anyone has any suggestions, especially for how to sharpen lathe bits for cutting aluminum. This is 6061 Aluminum.

My THIRD QUESTION on SET UP:

I also may need some help on how to set this up in the lathe. I just ordered the aluminum bar stock. It's not here yet. But it comes in 12" long bars. So I'll need to chuck up a 12" piece in the lathe. My lathe will easily chuck this, but the hole in the chuck is not large enough to allow the piece to go back into the head of the lathe, so this means that in the early going I'll be doing this operation at the end of a 12" long piece of stock.

Is that reasonable? Or should I cut these bars in half first so I'm only working with 6" stubs?

This is my first serious attempt at getting back into machining. I used to do machine work many years ago. But I haven't done anything lately.

By the way my lathe is an Enco combination lathe and milling machine very similar to this one, but not this precise model. They don't make mine anymore but this one looks extremely close in every detail I can see:



Lately I haven't been having much luck sharpening tool bits. I could use a lesson on getting the angles right.

Thanks

 

[mikey]

I'll take a shot at this and the other guys can pile on.

For the axles, I would use an undersized reamer. For a 0.125" axle I would suggest a 0.124" reamer. Before purchasing said reamer be sure to mic the axle stock to be sure it actually is 0.125". Stainless is usually sold in nominal sizes and is typically a thou undersized. If you need 0.125" then drill rod is a better bet. Lightly chamfer each end of the axle before pressing the wheels on. Another option is to use an on-size reamer, heat the wheel and freeze the axles. It will press on and won't come off unless you take it off. Yet another option is to simply drill on size and knurl the ends of the axle; this option will result is a very tight fit that should hold well.

The radius on the front of the wheel can be cut with a form tool but it is a big cut and may result in chatter. Personally, I would do this with a graver. You might be able to rough out the middle with a standard end mill and use a ball end mill for the radiused parts. Of course, you need a rotary table for this. If you must use a form tool I suggest you use the largest blank you have and grind in 18 degree relief angles. Top rake would be zero and the corner radii would be about 1/16".

Personally, I would cut the stock into manageable pieces so I could machine it without a steady rest. This would mean using maybe 3" long pieces, skimming one end round and then chucking that end for the rest of the work. Aluminum is relatively cheap and it is far more accurate to do this without using a steady rest. You should be able to get two wheels from each 3" long piece, I think.

For the rim shape that will ride on the track, a knife tool will work fine as the finish is not primary. I suggest 15 degree relief angles, 12-15 degrees of back rake and about 35 degrees of side rake. With a small (1/32) nose radius that tool will shave off the 6061 nicely and still leave you with a tiny radius in the shoulder. If you need some guidance on tool grinding, PM me.

For parting, I would use a P-1-N, P-1 or at most a P-2 parting tool. 1/8" is way excessive. Use WD-40 for lube, make sure your tool is sharp and is on center and perpendicular to the work. Piece of cake.

 

[Robo_Pi]

Hi Mikey, thanks for the tips on the press fit for the axle. I can actually try a few different methods on some scrap aluminum to see what works best for me.

The radius on the front of the wheel can be cut with a form tool but it is a big cut and may result in chatter. Personally, I would do this with a graver. You might be able to rough out the middle with a standard end mill and use a ball end mill for the radiused parts. Of course, you need a rotary table for this. If you must use a form tool I suggest you use the largest blank you have and grind in 18 degree relief angles. Top rake would be zero and the corner radii would be about 1/16".

I don't have a rotary table for the mill. This is just a hobby project, so I'm trying to keep cost as low as possible. I do have some 1/2" blank lathe tools though. I can try grinding up a forming tool from one of those. This is just for cosmetic purposes instead of having a bland flat wheel. So it doesn't need to be too fancy. Even just a couple of grooves would make it look interesting. I'm planning on then painting that part of the wheel and leaving the flat parts of the face aluminum. This way my rolling stock can have some interesting looking wheels.

Personally, I would cut the stock into manageable pieces so I could machine it without a steady rest. This would mean using maybe 3" long pieces, skimming one end round and then chucking that end for the rest of the work. Aluminum is relatively cheap and it is far more accurate to do this without using a steady rest. You should be able to get two wheels from each 3" long piece, I think.

I like working with shorter pieces too. I also don't have a steady rest. All I have is a tailstock center and that would probably get in the way. I haven't even been out to the lathe lately. I just now came up with these ideas to make these model railroad bogies and decided to go ahead and order some aluminum. So it's on it's way and when it gets here I'll see what I can do with it. I would also like to get as many wheels as possible. Aluminum may be cheap, but costs add up pretty quick when making a lot of bogies. So I'm going to be shooting for operations that get the most from the material.

For the rim shape that will ride on the track, a knife tool will work fine as the finish is not primary. I suggest 15 degree relief angles, 12-15 degrees of back rake and about 35 degrees of side rake. With a small (1/32) nose radius that tool will shave off the 6061 nicely and still leave you with a tiny radius in the shoulder. If you need some guidance on tool grinding, PM me.

I think I understand what you are saying here. But a picture always helps. I looked up a picture on Google and modified it with your suggestions. Just want to see if I'm understanding this correctly.



Did I get that right?

For parting, I would use a P-1-N, P-1 or at most a P-2 parting tool. 1/8" is way excessive. Use WD-40 for lube, make sure your tool is sharp and is on center and perpendicular to the work. Piece of cake.

I just went out and looked in my tool drawer. I have a bag of P-1-N parting blades and tool holder, so I'm all set with that.

 

[mikey]

I'm sure are many other ways to attach the wheels to the axles. Even permanent LocTite would probably work.

For the scalloped area, it might work if you ground a round nose tool and fed it in a bit, then fed out with the cross slide while leaving the tip at depth. If you make repeated passes I bet you could do exactly what you originally intended. I hope that's clear.

Remember that you want to keep your stick out at no more than 2 diameters max. If it had to be longer than that then you need a live center or steady rest. We all exceed this recommendation at times but accuracy does suffer and the occasional flying object does occur. I know material can cost but safety and accuracy are important. By the way, an ebay seller called 6061 Dude has good prices on aluminum and is a sheer pleasure to work with. He ships via Priority Mail and I buy from him all the time. Amazon also sells round stock, sometimes at stupid prices and if you have Prime you get free shipping. Most of my tool steel comes from Amazon - check them, too.

You have the tool angles absolutely right except that I screwed up. Back rake should be about 35 degrees and side rake should be about 15-16 degrees instead of the other way around. Aluminum likes a ton of back rake - this will reduce cutting temperatures and cutting forces while focusing most of the cutting forces at the tip of the tool. In essence, you are creating a very positive geometry on this tool and it cuts very, very well. If you have a 3/8" HSS blank that will work better for a machine of your size.

Edit: These tool angles work well for most tool shapes for aluminum. It will work for a knife tool but a general purpose shape would work as well or better. By general purpose, I mean a tool shaped half way between a rougher and a facing tool, with an end relief angle of about 80 degrees. This will allow you to rough, face and finish with the same tool by changing your lead angle and that 80 degree end cutting edge angle will let you get into corners. If you put a 1/32" nose radius on it it will produce a mirror finish on your parts at anywhere near 1200-1500 rpm. If the corner radius on your part has to be sharper then a 1/64" nose radius will work nearly as well.

I use a P-1-N for stock up to 1-1/2". If you get your set up right you should sail through 6061. Put a 7-8 degree relief at the nose of the cutter and grind the tip straight across.

 

[Robo_Pi]

By the way, an ebay seller called 6061 Dude has good prices on aluminum and is a sheer pleasure to work with.

That's exactly who I ordered it from. I was looking around all over the place for aluminum at decent prices. Some places have it fairly cheap, but then they want a ton for shipping small quantities, or they add additional "Cut Fees" that just about double the price. So I looked on eBay and found 6061 Dude and he's got them all beat. Definitely the best prices I've found so far. And it's even free shipping on the pieces I bought. I just bought two pieces of 12" aluminum round stock. They should be here next week. So I'll be looking into making some wheels. I didn't order the 1/8" stainless rod yet though for the axles. I was going to order that from OnlineMetals.com along with a bunch of small brass pieces I'll need for building the rest of the bogie in the first picture of the OP. I'll be building these bogies entirely from scratch including the couplers. So I'll no doubt be back for more machining advice.

In fact, while I'm at it maybe I should pass this thing by you. It's a small metal saw. I'm hoping to use it for cutting thin pieces of brass and aluminum. It's a really cheap tool I know, but this is just a hobby for me and I don't really want to invest a ton of money in expensive machines. But then again I'm not sure if this will work. I found it on Amazon.com and some reviews didn't sound to bad, evidently gun enthusiasts use this for cutting brass cartridges.



I realize this is just a little flimsy tool, but at $29.97 and free shipping it's hard not to give it a shot. I'll be cutting brass tubing only 0.032" thick wall. In very tiny pieces. And maybe small pieces of aluminum C-channel only 1/4" to 1/2" with 0.125" wall. So it's all going to be pretty tiny stuff. I'd like to get something a little better, but it seem like any "real tools" are significantly more in cost. If this thing would actually work for $29.97 it's hard to pass up.

If you care to look it up on Amazon it's called,
TruePower 919 High Speed Mini Miter/Cut-Off Saw, 2-Inch

The price is really attractive. Like I say, any "real tools" are significantly more expensive.

I'm certainly open to any suggestions in this area. I actually have this thing in my Amazon cart, but I haven't checked out with it yet. I'm still looking around for a potential better quality saw that won't cost me an arm and a leg.

 

[TommyD]

Check axle dia. and as mentioned, order an undersize reamer. Freeze the axle and warm up the wheel and assemble, a shrink fit, the wheel will expand from the heat, opening up the hole. The cold will, somewhat, shrink the dia of the rod. We men know about cold water and shrinkage

You COULD cut the alum. into slugs after taking a small chip off the OD. Face the back side flat on all slugs then do tour face work and reaming.

Note: Make sure the jaws on your chuck run true, put something that is trued in the chuck jaw you will be working in and check TIR with an indicator. IF there is run out, use the pinion above the chuck manufacturers badge for ALL your opening and closing of the jaws. Before you do any wprk, take a magic marker and make a line on your part running from jaw to jaw under the badge. This will keep any run out the same.

We used to make hundreds of bearing seal compression mold cavities at a time in bored soft jaws. We had to inspect set up and in production parts and had to keep any error in TIR concentric. Properly bored soft jaws kept our seal cavity blanks running dead nuts, as long as nothing got in the jaw space.

 

[mikey]

For $30.00, its worth a try if you think a 1/2" max depth of cut is acceptable. Harbor Freight sells the exact same thing that might be cheaper with a 20% off coupon.

There are many options for saws but for stock preparation its tough to beat a bandaw, even the Portaband type. If you plan to stay in this hobby then a 4X6 horizontal/vertical bandsaw may be in your future. This type of saw will cut off your 1-1/2" aluminum stock in about 20 seconds and produce square ends with minimum waste. It is one of the best and most used tools in the hobby shop so you might consider it.

 

[stupoty]

I would be tempted to cut blanks for the wheels from the bar stock and make some sort of fixture with a centre pin to posibly glue or tape the wheel blanks to.

Parting off that far from the chuck might be "interesting" in a bad way I personaly always find parting things with a large centre hole easier that near solid parts.

Stuart

 

[stupoty]

TruePower 919 High Speed Mini Miter/Cut-Off Saw, 2-Inch

Found a vid of some one using a similar saw,

Looks like its quite low powered but might be handy for mitres, are blades a reasonable price for it?

I lust over and keep an eye out for proxon branded small tools on ebay as they look to be amazing for the small intricate things (their list price has put me off purchasing them new) .

Stuart

 

[Robo_Pi]

There are many options for saws but for stock preparation its tough to beat a bandaw, even the Portaband type. If you plan to stay in this hobby then a 4X6 horizontal/vertical bandsaw may be in your future. This type of saw will cut off your 1-1/2" aluminum stock in about 20 seconds and produce square ends with minimum waste. It is one of the best and most used tools in the hobby shop so you might consider it.

I actually have a metal cutting bandsaw pretty much as you've described. And it would indeed cut the 1-1/2" aluminum bar stock down to size real nice. So I'll use it for that. But I was thinking on these other tiny brass and aluminum parts for the rest of the bogie chassis a little table top cut-off saw might be more convenient to work with. I watch the video Stuart, and looked up a couple more videos on Youtube. It seems to be a pretty popular little saw and people seem to be fairly pleased with it for cutting cartridge brass which most people seem to be using it for. It should work for the small parts I want to make. No cuts should be more than 1/2"

The thing I don't like about it is that when the tiny part is cut off it goes flying across the room. That tiny part will be the part I want. I'll have to make a way to hold those tiny parts when they are cut off so they don't go flying around.

Here's an exploded view of some of my bogie chassis parts:



The two end blocks that will hold the ends of the axles are 1/4" square brass bar stock. The center box tht holds the coil springs will be cut from from 0.375" square brass tubing with 0.032" wall. So those are the three parts for this assembly that I would need to cut off. I could do that on the bandsaw but the bandsaw seems a tad bit huge and clumsy for these tiny parts. Although I'm thinking in terms of using it horizontally. Actually if I turn it up vertical (something I don't do very often), I suppose I could make a jig to hold the part and just run them through the bandsaw blade by hand. That might actually work better. I never really thought about using the bandsaw vertically. I'm so used to just using it in as a horizontal cut off saw.

So maybe doing these on the bandsaw will work pretty well. The $29 might be better spent on new bandsaw blades. I was thinking that high-speed cut off saw might actually make cleaner cuts. But after looking at some of the videos of people cutting off brass cartridges the finished cut doesn't look all that clean. A bandsaw might actually make a cleaner cuts after all.