Hardware Questions

Technical Technical Discussion
#1

I’ve been poking around various hardware suppliers, and haven’t been able to find a couple of things that my team will likely need for the offseason. I was wondering if anyone around here knows where I might be able to obtain the following:

  1. Hex shafts which are turned down to fit into circular bearings on their ends. AndyMark sells a couple of these for use in their gearboxes, but they’re made of steel and they’re too short - does anyone know if any supplier sells these in either 6061 or 7075, or would we need to just buy a hex shaft and lathe it ourselves?

  2. 3/8’’ hex-bore 5mm-pitch HTD belt pulleys.

The idea here is that we’re designing something in which we’d like to keep as many parts off-the-shelf as possible, so lathing our own parts, or broaching our own hex bores, is unattractive.

#2

I’m sorry to say that you probably won’t find such custom parts available off the shelf. This is a good time to look into buying that lathe, and that broach set and press.

#3

Is there a reason you cannot use a hex bearing on the end instead of round?

#4

That second item is a prime candidate to be a 3D printed part. Once you start looking, it is surprising how many parts you find could be made this way. We had at least half a dozen unique parts in our robot this year which were 3D printed.

#5

Sounds like you’re just going to have to buy a .5" hex shaft and turn down the edge yourself. Shouldn’t be too difficult if you do have a lathe.

#6

Would like to use flanged bearings and a construction in which the shaft holds the bearing in place. Construction would be more complicated, otherwise; it’d require shaft collars, and shaft space is at a premium.

#7

We did that with our Vex Pro Ball-Shifter by taking out the short shaft and buying the stock from vex to lathe down the end to fit in a bearing. We could not find any prefabricated shafts to use. Hope this helps.
http://www.vexrobotics.com/vexpro/shafts-bearings-and-hardware/shaft-stock.html

#8

If they are short, McMaster has threaded hex standoffs, in aluminum & steel. Then you could use a bearing on a bolt threaded into the standoff. Not cheap or easy, but no machining.

http://www.chiefdelphi.com/forums/newreply.php?do=newreply&noquote=1&p=1271391

#9

You can also tap the end of the hex shaft and sandwich a thrust washer between bolt head and the flanged side of a hex bearing. It’s not pretty, but could work in a pinch.

#10

There are many ways to get out of buying a lathe, but there is so much more you can do when you finally get one, why keep putting it off?

#11

We have access to a lathe; I was simply wondering if anyone sold the things so we wouldn’t have to make them ourselves. Off-the-shelf parts are a huge benefit. It’s not that we can’t do it otherwise, it’s just that one of the things we’re going to be shooting for with this design is simplicity and ease of construction, which custom-lathed parts don’t really fit into.

Ultimately, though, we’ll likely end up lathing the things ourselves. That’s what machine shops are for. I just wanted to make sure that we don’t go with that if there’s a way to avoid it.

#12

Why avoid using the machine shop you have in house?

#13

It’s not in-house.

#14

Sorry for the off-topic post:

A lathe is a machine, it is used to Turn parts, not lathe them.

Very unlike most other machining terms. Can anyone think of another machine where the work it does is not the name of the machine?

#15

For our 2012 robot (and I want to say 2009, but it’s been a minute since I saw it), we took hex shaft from McMaster-Carr and had our machine shop turn down the last little bit on each end (plus some E-clip grooves, but that’s not relevant to your task). Since the bronze bushings we used were 1/2" and the shaft is 1/2" across the flats, all they had to do was round off the hex. Easy and fairly quick on any respectable lathe, so much so that I wouldn’t try any quick-and-dirty techniques except in truly dire circumstances.