17 replies to this topic

[Jimbolina]

Is it fairly common for some new wheels to not fit properly onto an axle?

 

For example, I have a few newer Pro-Track 1/8” wheels (with tires) and some relatively older Parma wheels that simply will not slide onto their respective 1/8” axle.

 

A couple of other sets of the Pro-Track seem to want to go on, but it took some force to do so. Not cool.

 

That bothers me as it would seem that aspect should be an easy dimension to get correct. I also feel one should not have to ream a brand new set of wheels, after the fact, to get them fitting properly. Anyway, just curious how frequent that irritating dynamic is.

[Bill from NH]

I'd try polishing down an axle rather than reaming the hubs, Chuck it in an electric drill and use fine sandpaper.

 

Do you have the same fit problem with new crown gears? It's always possible that your axle is a couple thousands bigger than 1/8" and the wheel bores are more exact.

[John Luongo]

Often, before assembly, I would use a 1/8" drill bit to dress the axle bore of new wheels, using my fingers to spin the drill bit to remove tiny manufacturing imperfections in the hub. Polishing the axle with 600 grit sandpaper also helps when you are trying to change wheels "under the green."

[Dave Crevie]

If other wheels (and gears) fit then I would call it a wheel problem. If all wheels are too tight, then the axles are a taste oversize. You can't put a .125 inch diameter axle into a .125 inch diameter hole. So production tolerances were developed so that the two would fit together. Generally, since tool steel rod, and axles are usually made of tool steel, is sold as .125 inch diameter plus or minus .0003 inch, a slightly oversize reamer must be used to finish ream the axle hole. Reamers are sold as plus or minus, that variation being dictated by the machinist when he purchases the reamer. If I were making wheels, I would ream the holes .1255, and hope that the user of those wheels would buy quality axles that fit the + - .0003 tolerance rule. (How the reamer is used can effect the size of the hole. Overheating the reamer by forcing it will make a bigger hole. Different coolants will also effect how the reamer cuts.)    

[blkdout76]

IDK what it is with the Mid America axles, but I bought some 1/8 axles, and couldn't get gears or tires on them. Money well spent 👍

[Jimbolina]

Often, before assembly, I would use a 1/8" drill bit to dress the axle bore of new wheels, using my fingers to spin the drill bit to remove tiny manufacturing imperfections in the hub. Polishing the axle with 600 grit sandpaper also helps when you are trying to change wheels "under the green."

Excellent recommendation!

 

Thanks!

[Dave Crevie]

IDK what it is with the Mid America axles, but I bought some 1/8 axles, and couldn't get gears or tires on them. Money well spent 👍

 

If you have a micrometer that reads in tenths, measure the diameter of the axle. Measure in several places. It should not measure over .1250 inch at any of those places, ( .1247 to .1249 ideal. )

 

If that checks, you need to measure the inside diameter of the axle bores on the wheels and gears. This is a little harder, and requires a set of pin gauges. The .125 inch pin should fit in easily, the .126 pin should not. (make sure the pin gauge set is NOT marked PLUS or MINUS.) 

 

OK. So with all this done, if the axle measures .1250 with no "fat" spots, the .125 pin gauge fits easily into the bore of the wheel and the .126 does not, this is an ideal fit for slot car use. At most you will end up with .0005 clearance per side, which will be what we consider "no shake". But most likely, the clearance will be nothing to maybe .0003 per side. 

 

Before we condemn a product, let's be sure we know where the problem lies. For the most part, slot cars are produced by cottage industries. They may not be well versed in quality assurance procedures. So if you find a supplier that meets your needs with no issues, stick with them.   

[Mark Onofri]

Listen to Dave.

[MSwiss]

Between owning a raceway and having people bring in their 20-year-old cars, sleeving a 1,000+ 1/8" Parma gears in the early days of Retro, and racing hard bodies that required 1/8" axles, I can tell you with 100% certainty, when something labeled 1/8", measures 0.1250" in diameter, it's not good for slot cars.

 

Whenever they bring in those old cars with dried out tires, I know it's a 50-50 chance the JK replacements will go on without drama.

 

It doesn't matter if you have a 1/8" reamer, if the axle is .1250" you will most likely have an issue. It might go on with some effort, but it will be a pain to adjust.

 

As soon as you twist the wheel on a bit, it will gall the axle and then it will be hard to get off.

 

The problem lies in not buying shafts specifically made for slot cars.

 

They try to save a few pennies, or go for that drill blank BS.

 

Buy a Koford M418  and your problems are over.

 

They  were $1.49 retail  for years, went up to something like a $1.54 for awhile, and recently went up to $1.98.

 

JK and Protrack tires will always go on easily, but without slop.

 

I don't have a micrometer, but I would guess they are .1235 in diameter. 

[Jimbolina]

Between owning a raceway and having people bring in their 20-year-old cars, sleeving a 1,000+ 1/8" Parma gears in the early days of Retro, and racing hard bodies that required 1/8" axles, I can tell you with 100% certainty, when something labeled 1/8", measures 0.1250" in diameter, it's not good for slot cars.

 

Whenever they bring in those old cars with dried out tires, I know it's a 50-50 chance the JK replacements will go on without drama.

 

It doesn't matter if you have a 1/8" reamer, if the axle is .1250" you will most likely have an issue. It might go on with some effort, but it will be a pain to adjust.

 

As soon as you twist the wheel on a bit, it will gall the axle and then it will be hard to get off.

 

The problem lies in not buying shafts specifically made for slot cars.

 

They try to save a few pennies, or go for that drill blank BS.

 

Buy a Koford M418  and your problems are over.

 

They  were $1.49 retail  for years, went up to something like a $1.54 for awhile, and recently went up to $1.98.

 

JK and Protrack tires will always go on easily, but without slop.

 

I don't have a micrometer, but I would guess they are .1235 in diameter. 

Thanks! I will Oder these Kofords ASAP.

[Dave Crevie]

I've been using Koford axles for, well, forever. Never had a problem. Just measured one, checks .124 and maybe a tenth. (.0001 ) Checked with a mechanical mic. with a vernier tenths scale. I only use it for fine measurements, and was calibrated a year before I retired. So I trust it. ( When I retired I left the supermic with the company, so I no longer have it. It reads .00000 places. That would be overkill in this case. )  

 

Way back when, mass produced slot car companies always went with undersize axles. It cuts assembly time, the worker not having to "fiddle" to get the wheel/gear on. Of all the 60's era cars I have, I don't remember any of them having axles over .123. (assuming they were set screw wheels) Typical, since QA generally was not known in the hobby industry. Set screw wheels were a big improvement over thread-ons. A little wobble was much better then the wobble you could get with the threaded wheels. 

 

Plus, back then I don't think any wheel manufacturers knew about oversize reamers. They probably used on-size .125. And as I said a .125 dia. axle will not fit in a .125 hole. So they had to use undersize axles.   

[Mark Onofri]

Dave, years ago I purchased some drill blanks, in 3' lengths.
I found out the following:
1) buy HARDENED blanks!!!!,if you choose to go this route.
2) yes, yes they come in .ooo dimensions. Here's something you can do for kicks, try any make of Axel on a dozen assorted bearings. Both bb and oilites. One size does not fit all.
Further more, I have encountered this issue and,a quick pass on the bench grinder with scotch bright.... Presto..
It fits. If all else fails, ⚒️ 😶

[Dave Crevie]

I keep a selection of undersize HSS drill blanks in my box to use in an emergency. Normally, I will use these where the ball bearing bores are U/S, and I don't have time to unsolder the offending bearing and solder in a new one. I seldom use them with oilites.

 

I don't encourage polishing down axles for a couple of reasons. It's too hard to hold a dimension polishing by hand using a Dremel or power drill to spin it. Secondly, there is a specific grade of finish on the axle. They are precision ground to attain that finish. When used with oilites, that finish is important. Too rough a finish will prematurely wear out the bore of the oilite. 

 

Centerless grinding. This is a non-throughfeed centerless grinder. 

 

https://youtu.be/Ntf8CnvsIgM?si=Y4f209Zycn8gFHj4 

[Bill Seitz]

This problem can be caused by both oversize axles and undersize hubs. I have some old 3/32 axles that will not fit in a ball bearing. They'd be fine in an oilite and even take up some wear in the bushing. Certain hub brands are always undersize. I now keep a 3/32" drill bit handy to open up the hubs to the correct size first time I use them. Am sure same condition probably exists in 1/8 stuff.

[Mark Onofri]

Dave, I don't think that they nitrate the axels, only the cranks🙄.

[Ramcatlarry]

If an axle is too snug, check for two areas:

1) is there a burr on the end that need to be chamfered - especially if you cut one end off.

2) Sometimes you need to chuck one up in a dremel or drill and polish the length with Scotchbrite or emery paper to clean up that 1/2 of  thousanth of an inch.

[priscilla]

Generally, it’s ideal that wheels fit easily onto an axle without force. However, some racers or enthusiasts do lightly ream or sand the inner bore of the wheel to ensure a smooth fit. While this isn’t ideal for brand new wheels, it's a common practice when minor fitment issues arise. In terms of ball bearings, make sure that the bearings in the wheel are also well-matched to the axle diameter. If the bearing doesn't fit snugly on the axle, it could cause alignment or fitment issues, even if the wheel bore is correct. If you have to ream or modify the wheel for a proper fit, ensure that you're also checking the bearings to make sure they are properly seated and aligned.

[stoo23]

I can also concur and heartily recommend Koford axles !!

 

Have also been using them for YEARS, without issue.

Quite simply, ... Excellent