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Jimmy Nichols 06-02-2017 11:07

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jon Stratis (Post 1641036)
Personally, I think dealing with Thunderhex being a little oversized is a lot easier than dealing with regular hex being oversized. At least with Thunderhex we can toss it on the lathe and take a couple thou off, and once you dial in the amount you need, it's pretty easy to run down an entire shaft. Heck, in the few cases where we feel a need to use solid hex (instead of Thunderhex with the hole in the middle), we turn it down to fit in thunderhex bearings. It's just easier to slide the shafts in and out of thunderhext than it is trying to get the shaft prperly aligned with the inner race of a hex bearing.

I agree

Chris is me 06-02-2017 12:05

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641018)
Isn't that an old warning from last year? When our bearings and shaft first arrived we checked the fitment and it was smooth. So thats why we suspected the tapping operation.

Just throwing this out there - when your shafts arrived, were they left outside in the cold before opening? The tolerance is so close that a shaft below room temperature will smoothly fit, but they will be too tight if you don't do that.

Anyhow, for us it's now a standard practice to take some emory cloth and shaft stock and run it on the lathe for a second or two before fitting into bearings. Just enough to strip the anodize layer off should do it. (We also use the "tight press" bearings because they are so cheap in 11-packs)

ThunderHex is way, way, way better than regular hex. I'll never go back to regular hex bearings - they are a pain to fit, a pain to align, and they are far harder to fix the shaft for if they fit too tightly.

Jimmy Nichols 06-02-2017 12:08

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Chris is me (Post 1641080)
Just throwing this out there - when your shafts arrived, were they left outside in the cold before opening? The tolerance is so close that a shaft below room temperature will smoothly fit, but they will be too tight if you don't do that.

Anyhow, for us it's now a standard practice to take some emory cloth and shaft stock and run it on the lathe for a second or two before fitting into bearings. Just enough to strip the anodize layer off should do it. (We also use the "tight press" bearings because they are so cheap in 11-packs)

ThunderHex is way, way, way better than regular hex. I'll never go back to regular hex bearings - they are a pain to fit, a pain to align, and they are far harder to fix the shaft for if they fit too tightly.

They were not left outside.

Thanks for the feedback. I'm leaning this way myself. Hearing confirmation from others is re-assuring.

RoboChair 06-02-2017 12:29

Re: Thunderhex and Thunderhex Bearings
 
I have used shrinking to fit thunderhex into bearings before. I used liquid nitrogen(-320 F) to do it, but dry ice(-109 F) should do just fine and a lot of grocery stores carry it.

Aluminum shrinks/expands ~0.001"-0.0015" per inch per 100 degrees F, which you can get about 1 thou shrink with dry ice or about 2 with liquid nitrogen.

BumblingBuilder 06-02-2017 12:32

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641031)
Have you found another option when using hex shaft? We bought some from McMaster-Carr last year and had issues with the tolerance on it vs. the tolerance of the Hex Bearings and had an extremely difficult time installing the shafts on our climber. So we decided to go with the Thunderhex this year.

Andymark offers 7075 hex shaft that our team now uses for drivetrain axles (but works for anything else). If anything, however, this shaft is a little too thin. There's a small degree of play in our wheels that are mounted on it, but we haven't noticed a loss in performance as a result.
It could even just be our wheels too. I've been too busy with other parts of the robot to address the seemingly trivial problem that is axle size. We're just happy we didn't need to slice of faces of the shaft on a mill this year

We also get hex shaft from a local metals warehouse, Discount Steel. They may or may not ship to your area... but if you have a local metals warehouse I'd imagine they would have hex shaft. If you do have a shop nearby bring hex bearings and test them on the shafts before you buy them

Jimmy Nichols 06-02-2017 12:50

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by BumblingBuilder (Post 1641113)
Andymark offers 7075 hex shaft that our team now uses for drivetrain axles (but works for anything else). If anything, however, this shaft is a little too thin. There's a small degree of play in our wheels that are mounted on it, but we haven't noticed a loss in performance as a result.
It could even just be our wheels too. I've been too busy with other parts of the robot to address the seemingly trivial problem that is axle size. We're just happy we didn't need to slice of faces of the shaft on a mill this year

We also get hex shaft from a local metals warehouse, Discount Steel. They may or may not ship to your area... but if you have a local metals warehouse I'd imagine they would have hex shaft. If you do have a shop nearby bring hex bearings and test them on the shafts before you buy them

We bought hex shaft from McMaster-Carr last year and the tolerances were horrible the hex bearings wouldn't fit at all and we machined and/or sanded the surfaces. We switched to Thunderhex and decided to use it again this year. We Metal Supermarkets locally, but I haven't tried to source any hex from them before. May try that in the off-season to see what kind of pricing we can get.

Thanks!

ClockworkGold 06-02-2017 13:12

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by BumblingBuilder (Post 1641113)
We're just happy we didn't need to slice of faces of the shaft on a mill this year

Hate to break it to you Matt, but I spent all of yesterday flycutting our intake axles ;)

To all the teams struggling with hex shaft and bearings, here are some tips I've accumulated over the past year on the subject:
  • According to our civil engineer and machine shop specialist mentor, "0.002 inches isn't a press fit, it's a miss." Physically go to your local metal supplier with a caliper, a few new bearings, a rag, and some carburetor or brake cleaner to wide off any excess dirt or grease that may be on the stock. Hex is cheap, about $0.80/foot so loading up on up to 60 feet is a great idea if you're building two robots like a lot of teams are. Just remember, if it's not perfect, then it's absolutley not worth the hassle.
  • ThunderHex does indeed work with half inch hex applications, except post 2015 hex bearings. If you want to power ThunderHex in a live axle scenario without an assembly headache, you need P/N: 217-4006 or 217-4270.

Mr. Mike 06-02-2017 14:03

Re: Thunderhex and Thunderhex Bearings
 
This will be our 3rd year using thunderhex. All of our old stock had to be polished to fit bearings. The new stock from this year seems to fit fine.

If the bearings fit before tapping then don’t after tapping, the tap needs thrown away. The tap is deforming the material not cutting it. Anodize is very abrasive on cutting tools.


Mr. Mike

Jimmy Nichols 06-02-2017 14:08

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Mr. Mike (Post 1641171)
This will be our 3rd year using thunderhex. All of our old stock had to be polished to fit bearings. The new stock from this year seems to fit fine.

If the bearings fit before tapping then don’t after tapping, the tap needs thrown away. The tap is deforming the material not cutting it. Anodize is very abrasive on cutting tools.


Mr. Mike

Interesting. I wasn't involved in the making of the parts. only hearing about it since I am the person who orders the parts and was warned they may want to replace all the bearings we just ordered. So I will bring this up also. Thanks Mike!

Cory 06-02-2017 14:16

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641128)
We bought hex shaft from McMaster-Carr last year and the tolerances were horrible the hex bearings wouldn't fit at all and we machined and/or sanded the surfaces. We switched to Thunderhex and decided to use it again this year. We Metal Supermarkets locally, but I haven't tried to source any hex from them before. May try that in the off-season to see what kind of pricing we can get.

Thanks!

You are never going to find hex at your local metal supplier that will be toleranced such that you do not have these issues.

Jimmy Nichols 06-02-2017 14:25

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Cory (Post 1641181)
You are never going to find hex at your local metal supplier that will be toleranced such that you do not have these issues.

Based on our experience last year, this year, and reading others. I think you need to use the Thunderhex bearings, always. You can always throw any hex you have on the lathe and turn it down or sand it down to the 13.75 or 13.73 mm you need.

krtanjek 06-02-2017 14:33

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641043)
Yes it is 1/4-20. No issues seen before tapping, but was found after.

Out of curiosity, did you drill the thunderhex prior to tapping 1/4-20 with a #7 Drill bit?

We have old and new Thunderhex and if you do not drill out prior to tapping we have seen it expand, but not if we drill out with #7 before tapping.

Jimmy Nichols 06-02-2017 14:45

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by krtanjek (Post 1641191)
Out of curiosity, did you drill the thunderhex prior to tapping 1/4-20 with a #7 Drill bit?

We have old and new Thunderhex and if you do not drill out prior to tapping we have seen it expand, but not if we drill out with #7 before tapping.

I wasn't directly involved but was only brought in after the fact. My assumption is they did not drill it out for a number 7 but instead tap it since the website advertises the hole as being ready to tap.

All the Thunderhex being used was purchased this season.

krtanjek 06-02-2017 14:56

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641198)
I wasn't directly involved but was only brought in after the fact. My assumption is they did not drill it out for a number 7 but instead tap it since the website advertises the hole as being ready to tap.

All the Thunderhex being used was purchased this season.

I would drill it out with #7 and compare, we like to make sure all holes are at least #7 before using the 1/4-20 tap. Good luck.

TD78 06-02-2017 15:03

Re: Thunderhex and Thunderhex Bearings
 
Quote:

Originally Posted by Jimmy Nichols (Post 1641198)
I wasn't directly involved but was only brought in after the fact. My assumption is they did not drill it out for a number 7 but instead tap it since the website advertises the hole as being ready to tap.

All the Thunderhex being used was purchased this season.

We broke 2 taps before realizing that the hole on the new TH was not to size. Serves us right not checking before hand. The last few axles we did drill out with the correct drill bit before tapping and it was a breeze. While this year's TH shafting has the issue with the center hole, the outer dimensions are perfect so far...the flats fit to 1/2" width and the rounded corners fit inside the TH bearings without needing to file.


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