Set Screwed

[HO RacePro]

I am getting really flipping annoyed at the all-too-frequent failures of set screws and hex drivers for same. It is not unusual to have the threads strip out in aluminum wheels or the socket of a set screw strip the first or second time out.

My most recent failures have been with Super Wheels SW1710S set-screw wheels. Their set screws have an M2 thread and are only 3 millimeters long. Very tiny. But it isn't just Super Wheels. I have had issues with several different brands of wheels. Super frustrating when you can't get a wheel off because the socket is stripped, or can't get a wheel tight because the threads are stripped.

And it is not because I'm being a gorilla on these things. I have a Slot.It PA72 M2 torque-limited driver, purchased from SlotCarCorner.com. It doesn't prevent stripped threads or sockets. (By the way, it is supposed to be torque-adjustable. It is also supposed to take replacement tool-tips. Damned if I can figure out how to do either. No instructions came with the tool.) I also have Wiha hex drivers, and a Quick Slicks driver. The set screws that come with wheels often won't engage with one driver but might with another. Or the other way around. I can't tell in advance which will work, or if any will.

The Quick Slicks driver has some promise. The tool-shaft is very long and held in a pin-vise. It can be reversed to provide a fresh tip, or cut with a Dremel tool cutoff wheel to do the same. It is nice that it has no shoulder on the tool to interfere with anything.

I have bought M2 x 6mm set screws -- twice as long as the 3mm screws the wheels come with. They happen to fit the hubless Super Wheels. But dang if those don't seem to work any better.

I have been experimenting with drilling out and re-threading the set-screw holes on wheels. I have done that for M3 x 6mm set screws, replacing the comes-with M2 x 3mm screws. Kinda brutal but I've had some success. It is the best solution I have found so far. I had to print special fixtures to hold the wheels aligned for the drilling and tapping operations.

I've also purchased some -- very expensive -- M3 Torx socket set screws and the Slot.It torque-limiting driver for same. Those came from LEB Hobbies. I haven't played with them yet. Might cure the stripped sockets, dunno about the stripped threads. Of course I'll have to drill out and re-thread the wheels because M3 set screws are too large for any 1/32nd slotcar wheel I know of.

I have also purchased a drill and tap for M2.5 set screws. Something else to 'speriment with. Not quite so radical as the M3 screws.

On a recent custom-car build I just gave up and superglued the wheels on. How to get them off again? Not sure. My best idea right now is to cut the axle in half, salvage the gear but replace everything else. Yes I am that desperate.

But I probably could make a wheel-puller tool. Could be the ultimate solution -- use superglue or Loctite and get rid of set screws entirely. Maybe not the dumbest idea I've ever had.

[dinglebery]

Sounds like your problem is you are over tightening the screws and you're not using thread lock.

[Billy boy]

i agree with dingleberry, ive had a few strip out myself but i caused it. sometimes the set screw will have a little debris in it so you need to make sure the tool fits well in the socket. i start the set screw counter clockwise till i hear or feel the click then start going in. if you feel resistence- stop.im in no way saying you dont know what your doing but it seems like over tightening is your enemy. just snug is usually enough.

[HO RacePro]

Can anybody point me to instructions on how to adjust the Slot.It PA72 M2 torque-limited hex driver, and replace its tool-tip?

And I disagree it is me overtorquing the set screws. I've seen failures on the very first application, even before I try to tighten things down.

[Kevan]

NSR have the right idea with their wheel grubscrews.

[HO RacePro]

Um, care to expand on that comment?
Ed Bianchi

[chrisguyw]

NSR have always used M2.5 (4-40) set/grub screws.......a more coarse thread and a larger dia. drive (.050) than the most all of the other plastic car manufacturers use.

[Kevan]

What Chris said, much less likely to strip.
What I said a while ago, once your driver skips in a grubscrew...get that grubscrew in the bin. If the driver is badly worn let go of that too.

[Slot Car Corner]

Can anybody point me to instructions on how to adjust the Slot.It PA72 M2 torque-limited hex driver, and replace its tool-tip?

There is a small cap on top of the handle that you can very CAREFULLY pry off. Once the cap is removed, you'll see a small adjustment screw.



I don't think the tip is replaceable (if it is, I've never seen a Slot.It part for the replacement tip).

[HO RacePro]

Thank you SCC for the torque adjustment instructions!

I worked on my Slot.It driver, and was able to pry off the end cap easily with the edge of an X-Acto knife. The adjustment screw is deep inside the tool, but easy enough to get to and adjust. I backed off the screw several turns. I don't really know if that will be better, but it will be easy enough to make additional adjustments if necessary.

I notice that Slot.It claims to have a new, harder material for the tool-tip of this unit. So now I am thinking it might be worthwhile to buy a new one. Of course I have nothing better to do with my money than buy more tools!

I've tried to find where it was claimed that the tool-tip of this hex driver was replaceable. I swear it was advertised as such, but now I can't find it. My guess is you could back the adjusting screw all the way out and replace the entire head. But I've never seen that part for sale anywhere.

I have invested in a 2.5 millimeter tap and the 2.05 mm diameter drill to go with, plus printed out the appropriate fixture to allow me to drill and tap those Super Wheels for a M2.5 set screw. And I suppose I should buy the Slot.It adjustable hex driver for that size screw.

Geeze, what am I going to do with all my money? What a conundrum...

[Kevan]

Would it be easier to adjust if you drilled a hole in the cap so you don't need to remove it?

...no wonder I couldn't find it with that part number, it's a PA76

[HO RacePro]

Actually it is very easy to remove the cap. Now that I know it can be done I've found I can remove it with a fingernail. 'Course if you want to you can just leave the cap off. The tool works fine without it.

Also, I have found I can disassemble the whole thing by completely unscrewing that adjusting screw. In theory you can replace the tip that way, if you could ever buy the tip separately.

Ed Bianchi

[Mikeinclover]

Ed use this to remove CA glue it works great.

https://cloverleafracing.com/product_info.php?cPath=193&products_id=2278

[HO RacePro]

On the continuing topic of set screws, and ways to improve or avoid them...

I have, in desperation, actually superglued wheels onto the axles of a couple of my cars. The advantage? Not ever coming off. The disadvantage? Well, that too.

So I have invested in a puller designed to yank automotive windshield wiper arms off of their knurled posts. I'm hoping said tool will be the right size and power for pulling 1/32nd wheels off of axles I have glued them thereto. I suspect I'll need to modify it some, but y'all know I love a challenge.

Could be blue Loctite will be a better compromise than superglue. Might hold enough while still being decently pull-able. And then there's that green penetrating Loctite. You can apply it AFTER everything is assembled. Very, very useful sometimes.

Also, today I have placed an order for Slot.It brand plastic wheels. Advertised as sized to press-on 3/32" diameter axles. Purely for experimentation. I may end up truing them on my Professor Motor Tire Truing machine. I may try using them strictly press-on or perhaps with some superglue.

Why am I interested in plastic wheels at all? Well for starters they cost like a quarter what aluminum wheels do, so if I end up throwing them away when their tires wear out, not so big a loss. And if I can true them they might be every bit as good as the aluminum. Are they a bit lighter than aluminum, or even magnesium? I think so. Will they stay put, but come off when I want them off? TBD.

Maybe they'll inspire me to print my own wheels. I'm already printing my front wheels and making them true. Rear wheels shouldn't be that much harder.

Stay tuned buckaroos -- more entertainment ahead!

[HomeRacingWorld]

Ok....let me see if I have this right.

Because you can't use a wrench and simple set screw....the answer is to glue them and create a tool to get them off when needed. Or go back to plastic?

Personally, never had much issues with these screws. The advantage of adjust the wheel on the axle alone is worth it, let alone the performance increase of quality aluminum wheels.

Purchase a decent wrench and learn not to over tighten. Replace the screws over time if need be. Simple.

Guess it's just me...but this seems the opposite of "easy".

[HomeRacingWorld]

Oh I read it all.

Good luck.

[dinglebery]

Ed, how many other racers had a wheel come off during those races?

[HO RacePro]

The wheel didn't come off. It just slipped far enough along the axle my sidewinder gears disengaged.

Don't pretend tiny set screws aren't an issue. If they weren't torque-limiting hex drivers wouldn't exist. The sockets strip. The threads strip. It's a known nuisance and it shouldn't be. It's bad design, poor manufacture, or both.