Hex Axle- How to

Technical Technical Discussion
#1

We are looking to switch to a hex axle system this year, and I honestly have no clue how it works, is hex as simple as slide a hex-broached wheel/sprocket on and then snap ring it?

We are looking at WCD style for next year, and were thinking of using super shifters/tough boxes (repacked with our own plates) with a hex output. We want to have it layed out as such:

gearbox–>Sprocket–>Tubing w/ bearing block–>Wheel. Can we use the long hex axle that AM sells or do we have to machine our own? We are using performance wheels, for the time being…

#2

You can use the hex shafts from AM if those dimensions work for you, or you can machine your own. A very inexpensive ($50-$100) tool that makes this extremely easy is a hex collet holder such as this. Put your stock in a lathe collet of the correct bore and clamp the collet into this holder. The holder can be clamped into the vice on a manual mill. Then run down one side of the stock with the end mill, rotate the collet holder in the vice, and repeat until you have six identical sides.

You can also buy hex rod from various metal suppliers, but I am unaware of specifics there.

Another thing you’ll want to think about is the pieces that go on the shaft. Many you can get with a hex bore, but if you ever need to do it yourself, you will need a hex broach, or a sponsoring machine shop with one, since they are significantly more expensive (~$800 for rotary).

#3

Our team has been using the WCD style for a few years now. you may want to check out our cad files on it here. We have had our drive shafts out sourced to a sponsor but it was possible in house by one of our teammates.

#4

We bought our holder for $17 on amazon. Love it.

#5

Wow, that’s awesome.

#6

As a side note to this, in my experience Fastenal has the absolute worst prices on anything metalworking related.

#7

Haha, ok, good to know. I hadn’t really done much research on the best prices, mostly just how to find them and to be able to show what they are. We’ll definitely stay away from them then.

Also (to the OP), this thread has more about where to buy hex shafts and hex stock.

#8

You can get a 1/2 hex broach for just over $100. We bought one and a 3/8ths broach and it’s one of our more useful investments. Certainly not the most vital, but it’s good that we have it.

We have just bought hex stock from McMaster or other cheaper sources rather than machining our own shafting with no problems. We don’t step hex, but we never have found a time when that’s been necessary thanks to AndyMark hex bearings.

All you should need to run a hex based anything are snap rings for retention and the occasional spacers. No keys or awkward retaining rings to get lost.

#9

Are these rotary broaches? If not, have you been in many situations where you wish you had one?

#10

No and no. I don’t see what we’d need a rotary broach for?

#11

I guess I was under the impression a rotary broach gave you more options (which it still does: not cutting all the way through, using it on more standard machines…), but on reading more about it it looks like they’re actually worse in some cases. It all works out since it sounds like normal ones are cheaper…

#12

Blind broaching isn’t terribly useful for what we do, you’d need to retain the part axially in some other operation.

We have a full set of push broaches, and use them for hundreds of holes a year without issue.

For frc, I see the only real advantage of rotary broaches being the ability to run them on a cnc mill for the teams that have an in house machine.

#13

I got a chance to use a 5C hex collet at school, and it was very nice. I would highly recommend one.

http://www.cedar–rapids.com/Industrial-Equipment-/Hardinge-5C-hex-collet-3-8-adpic.PHP.jpg

#14

We seem to have 5C collet at our small school shop and we seem to have the set linked above. How do you use this on the mill or lathe? We have a very very very small shop with 1 mill and a lathe. So this would be very handy!!!

What is the tool to the right of the picture?

Thank you!

#15

Specifically the standard machines part… Could you elaborate on that? Personally, every shop I’ve ever worked in had an arbor press in house and that is how we always broached. Is this not standard equipment for most teams?

#16

Eh, there’s no “recommended big tools for your shop” section anywhere in a manual or update (etc) from FIRST. So I doubt it’s ‘standard’ unless there’s a mentor or sponsor who knows what they’re doing.

#17

Perhaps ‘standard’ was the wrong word. Perhaps ‘common’ would have been better.

#18

Quick suggestion if you’re looking to play with hex shaft:

Contact a local metal supplier and ask if you can look through their scrap. We have a supplier down the road that has dozens of random pieces of stock that are left over from cutting down 20’ lengths. We got quite a few short (smaller than 3’) pieces of hex last year for nothing.

#19

Be aware that if you do this, you might end up with 6061 hex axles. Then you’ll suffer months of mockery by all of your friends because of a silly drivetrain failure.

…just a heads up.

#20

There are no silly drive train failures except for those that are consistently repeated, but it’s a very good point about 6061 for use as cantilevered axles.