Has anyone found a source for 3/8" and 1/2" hex shaft stock? Preferably in the 4140 steel or 7075-T6 Al?
Andymark has aluminium ( http://www.andymark.com/product-p/am-2290a.htm ) but is out of stock.
McMaster has some but the smallest size in 4140 is 5/8", they have down to 3/8" but only in low carbon steel or 6061 Al.
Even onlinemetals.com doesn’t have any 4140 steel or 7075 AL in hex either.
The vexpro 1/2" Hex and Thunderhex is 7075
Vex has both hex and thunderhex in stock, in 7075-T6, for both sizes.
Thanks guys!
VexPro has 3/8" and 1/2" hex shaft in 7075 Al.
McMaster has other steel alloys in 1/2" hex, just not 4140. I’ve heard of teams using these, but honestly, I don’t know enough about steel alloys to be able to recommend them or not.
McMaster also has other Al alloys should you want them for whatever reason.
Edit: double sniped on VexPro
In a pinch you can use a 1/2" T-Handle allen wrench for shorter length axles. Quite fun to machine.
-Aren
Not to mention trying to explain why the wrench set is missing the 1/2" tool.
Now I’m curious what FRC team has ever used a bolt large enough to require a 1/2" allen wrench.
Seems like there should be a cheaper solution. How well does a wrench shaft fit to bearings and wheels?
Online Metals carries 7075 1/2 hex, the T7351 temper. It’s a slightly different heat treat than T6 that has improved stress corrosion properties. It’s simply a more involved precipitation aging profile.
We’re spoiled with their Seattle Warehouse having almost everything in stock. We pickup several of the 8 foot lengths of 7075 before build season.
I’ve been looking for some time for 4140 .375 hex and haven’t found it. It must be out there somewhere because AndyMark uses it on their AM Shifter cluster shafts. (http://www.andymark.com/product-p/am-0302.htm) unless it’s a mistake on their website or they got a custom mill order (which I doubt since they switched to 1018 and 12L14 on their other cluster shafts). I can find 4130, so that might be just fine.
My metallurgist mentor tells me for FRC purposes, and he was mentoring the team for a number of years before moving on, that 1018 is an acceptable alternate alloy for 4140. We’ve used it with no issues for drive train axles.
I highly recommend NOT buying hexshaft from McMaster. Unless we were not purchasing the correct shafts, they were all out of tolerance and often required a lot of filing to get it to work properly. The best hexshaft we used was the AM, but that is out of stock like you said. Best other option would be Vex.
As others have said, Vexpro is a great source for 3/8 & 1/2 7075 hex stock.
If you need any in a pinch, feel free to reach out to 1058 we usually have a few pieces of 1/2 on hand and are right up the road.
I sometimes buy hex stock from McMaster on purpose with the expectation that it’s slightly oversized for situations where I’d want low-backlash in my gearboxes. Some teams will machine their own custom oversized hex, but if you don’t have the machining resources you can get a similar effect with oversized mcmaster stock and some patience with the sander.
1018 yield strength is somewhat comparable to 4140 (12% less)
4140 has nearly 2x the ultimate tensile strength of 1018 though.
I would be looking at 4340 if using steel for some sort of axle (though not many applications in FRC require steel axles over aluminum).
1018 is a straight 18% carbon steel. It’s really lower than 7075 in strength (55 KSI) Fairly easy to machine.
4140 is a Chromium-Molybdenum (Cromoly) high carbon steel that is quite strong. Same with 4130 as well.
For any steel hex shaft or round you want to buy “Cold Rolled”. These have been run through a second rolling operation to give them the correct dimensional shapes and better grain structure.
I think you mean **.**18%
My experience is that aluminum hex stock, bought online or locally, tends to be oversized by a few thousandths. Steel hex stock on the other hand is typically just the right size, around 0.498 or 0.499 for the 1/2" hex size. What are other peoples’ experiences with steel vs. aluminum hex stock?
The only hex stock we bought other than from AM and Vex was half-inch 1018 cold-rolled steel from Online Metals, which was great; fit the bearings easily but didn’t wobble. We didn’t buy it for superior strength, but because it is stiffer than aluminum. We used about a 13" span of it for our 2017 climber, and even before we had a full robot weight, the deflection was worrisome as we thought of the angular stresses on the bearings. In retrospect, we should have used this on our 2015 lift as well; the flexing shafts were not kind to our chain runs.