Will a 5mm shaft fit a 8mm pinion

[Colinwarburton]

Hi everyone, wondering if a 5mm shaft will fit a 8mm mod1 pinion?

 

[Mikeeeeeeeeeeeeeeeal]

 

[fish]

Hi everyone, wondering if a 5mm shaft will fit a 8mm mod1 pinion?

 

[Hammer Down]

I’m gonna go out on a limb and say, no…

 

[Tex Koder]

 

[Neelis]

It will fit, but the shaft will not be centered in the pinion, which is not okay.

 

[Diem Turner]

You guys are way too quick to say no. C'mon fellas, get gud!
Yes, it's definitely possible and it works. It will require a tiny bit of fabrication, but no special tools or machines will be needed beyond things you find in most of your typical home workshops and sheds.

What we need is an adapter. The problem is that, ideally, you'll want that adapter to be made of the same type of material the pinion is made from. Mod1 gears should be made from hardened steel if they're to be of any utility. Working hardened steel is a right pain in the buttox but we can try to keep it to a minimum. What I did was the following: I took a 12T 5mm pinion gear that I had no use for. It was the smallest gear I had which helps with the aforementioned issue. I affixed the pinion to my Spektrum 4074 motor, connected it to an ESC, battery and radio gear (only the Tx/Rx are needed). I revved up the throttle channel to a moderate speed with the trim adjustment, fired up the bench grinder and proceeded to remove the excess material from the pinion gear until I had something resembling the item below left over (proceed slowly and cool the gear down periodically with a dip in water to avoid annealing the hardened steel - if you see the steel changing color at all during the grinding process, quench it immediately and continue grinding...as I said, hardened steel is a PITA so, slow and steady wins the race). Once you get down into the 8.5mm OD, check with either a set of calipers or a micrometer as you remove material to avoid overshooting the goal. As you near the end, some test fitting with the actual pinion is a good idea as well.

I then bored out the hole for the grub screw to accomodate the straight through passage of the M5 grub of the 8mm pinion gear.

Here's the adapter sitting inside the pinion.

And here's the pinion mounted to the 5mm shaft of a CC 1717 motor. Having ground down the pinion while mounted to a spinning motor helped to ensure that the outside geometry would follow that of the motor shaft and the 8mm pinion spins perfectly concentric with no signs of a weeble or wobble.

There are surely other (and better) methods to fabricate one of these. If you're a machinist or have easy access to a machinist, I'm certain a little tube like this is something you/he can turn out while sleeping. Then just harden the steel as you normally would and take it to final size. This was just my way of obtaining what I needed utilizing common tools that most people have available (and if you don't, they're cheap to acquire used in the classifieds...every home should have a bench grinder).

Happy grinding

 

[Sandracer_NL]

I was already waiting for the “aha” moment and @Diem Turner a.k.a. Macgyver provided it.

 

[Diem Turner]

Perhaps one other thing worth mentioning (not that there's a way around it, just something to be aware of) will be the appreciable and very visible amount of wear grinding down even one small 12T hardened pinion will put on your grind wheel. Compared to anything else you're likely to ever grind, the wear on the wheel will look excessive. Speaking from my own experiences anyways. When I was done I looked at the stone and on one side it was still square-ish. The other side had been rounded completely off to a radius in the 1/4-3/8" range. I didn't really notice it while I was grinding. All the bigger was my amazement when I noticed the carnage. So with that cautionary tale out of the way, perhaps anyone else that decides to go this route to make themselves an adapter will be smarter than myself and do a better job to distribute the wear across the entire wheel and not just to one side.

Although I will say this...the rounded over corner of the wheel has actually been a useful addition in terms of tool edge when working on carbon fiber. A hard corner closer to 90° isn't nearly as good at hobbing away large bands of material on each pass. The corner just kind of digs in and gets stuck more or less. The gentle slope of the rounded over edge works kind of like flattening Play-dough with a warm, smooth block of steel and you can remove fairly wide strips of CF with each pass and it also mitigates the risk of the grinding stone digging in unexpectedly. So it wasn't all bad. Yes...lots of lemonade 'round this place from all the lemons I've produced.

 

[Surchaufeur]

Its a temporary solution. Until the press fit wears out

 

[Diem Turner]

Its a temporary solution. Until the press fit wears out

I think you misunderstood something because there is nothing press fit here. It's just all within acceptable tolerances.

 

[SrC]

You guys are way too quick to say no. C'mon fellas, get gud!
Yes, it's definitely possible and it works. It will require a tiny bit of fabrication, but no special tools or machines will be needed beyond things you find in most of your typical home workshops and sheds.

What we need is an adapter. The problem is that, ideally, you'll want that adapter to be made of the same type of material the pinion is made from. Mod1 gears should be made from hardened steel if they're to be of any utility. Working hardened steel is a right pain in the buttox but we can try to keep it to a minimum. What I did was the following: I took a 12T 5mm pinion gear that I had no use for. It was the smallest gear I had which helps with the aforementioned issue. I affixed the pinion to my Spektrum 4074 motor, connected it to an ESC, battery and radio gear (only the Tx/Rx are needed). I revved up the throttle channel to a moderate speed with the trim adjustment, fired up the bench grinder and proceeded to remove the excess material from the pinion gear until I had something resembling the item below left over (proceed slowly and cool the gear down periodically with a dip in water to avoid annealing the hardened steel - if you see the steel changing color at all during the grinding process, quench it immediately and continue grinding...as I said, hardened steel is a PITA so, slow and steady wins the race). Once you get down into the 8.5mm OD, check with either a set of calipers or a micrometer as you remove material to avoid overshooting the goal. As you near the end, some test fitting with the actual pinion is a good idea as well.
View attachment 310514

I then bored out the hole for the grub screw to accomodate the straight through passage of the M5 grub of the 8mm pinion gear.
View attachment 310515

Here's the adapter sitting inside the pinion.
View attachment 310510

And here's the pinion mounted to the 5mm shaft of a CC 1717 motor. Having ground down the pinion while mounted to a spinning motor helped to ensure that the outside geometry would follow that of the motor shaft and the 8mm pinion spins perfectly concentric with no signs of a weeble or wobble.
View attachment 310512

There are surely other (and better) methods to fabricate one of these. If you're a machinist or have easy access to a machinist, I'm certain a little tube like this is something you/he can turn out while sleeping. Then just harden the steel as you normally would and take it to final size. This was just my way of obtaining what I needed utilizing common tools that most people have available (and if you don't, they're cheap to acquire used in the classifieds...every home should have a bench grinder).

Happy grinding

We all know you can make a square fit into a hole. And perfectly.
But is it worth all the effort?
Just do it right with the right gear and matching I.D./O.D.'s from the start.

I know they make an adapter for larger pinions to a smaller shaft, but it is not recommended. I didn't like it at all, when I tried it.
For 5mm to 8mm, I would not use any adapter/ or sleeve. Why even chance a high power setup with even a slight Non-Centric shaft/gear alignment.
I wonder if I even understood this OP's question at all.

 

[Diem Turner]

We all know you can make a square fit into a hole. And perfectly.
But is it worth all the effort?
Just do it right with the right gear and matching I.D./O.D.'s from the start.

I know they make an adapter for larger pinions to a smaller shaft, but it is not recommended. I didn't like it at all, when I tried it.
For 5mm to 8mm, I would not use any adapter/ or sleeve. Why even chance a high power setup with even a slight Non-Centric shaft/gear alignment.
I wonder if I even understood this OP's question at all.

Is it worth the effort? Honestly, yes. Personally, I hate the M4 grub screws you find on most 5mm shafted gears. You can't tighten them down as hard, you basically have to replace them every 2 or 3 uses (sometimes less) and they just suck in general. I use M5 flat bottom Torx® grub screws in my 8mm pinions. I just outfitted all of my 8mm gears with them over a year ago and I have yet to replace a single grub screw (I don't put everything I have into it but I do torque them down pretty good, often skipping thread locker).

This also solved the problem of not being able to find pinion gears larger than 34T for 5mm shafted motors and saved me $75-100 that I would have had to spend to purchase the five larger gears that became available for me to use on the 1717 (this is assuming that I would have even been able to procure these gear sizes for 5mm shafts at all).

And just to demonstrate how easy this is to use and how solid the connection is (I attempted to demonstrate concentricity though it probably doesn't really translate give the lighting angle of the shot, etc. but, if you're willing to take my word for it, this gear with the adapter on the 5mm shaft runs just as true and wobble free as the same gear does mated to a native 8mm shaft) I made a quick demo vid. I'll be honest, it turned out and works way better than I had anticipated or could have hoped for, especially in lieu of the fact that no professional machines like lathes or mills were used at all. Just Homer Simpson tools and some SOP trying to ensure that the steel maintained its hardness through the process.

 

[SrC]

I learned something today.

 

[SrC]

I'm a purist. Maybe it's just my OCD.
Adapters make sense. Yes.
Just not my first pick. I would rather just source the correct pinion.
I have purchased a few "Cheap" AMZ pinions that came with adapters that make the pinion quasi universal to 2 size armatures shafts.
I just toss the adapters.

 

[Diem Turner]

I'm a purist. Maybe it's just my OCD.
Adapters make sense. Yes.
Just not my first pick. I would rather just source the correct pinion.
I have purchased a few "Cheap" AMZ pinions that came with adapters that make the pinion quasi universal to 2 size armatures shafts.
I just toss the adapters.

I hear ya. It's not my first pick either. I much prefer 8mm shafts (more robust, larger grub screws on the pinions, etc.). But this adapter solution solved an otherwise insurmountable problem for me: getting pinions larger than 34T for my 5mm shafted motors. There just aren't any to be had here in Europe and I'm not paying $21/gear from SAGA plus outrageous shipping charges, plus VAT, plus import & duty fees.

 

[SrC]

Yeah sometimes you just do what you got to do. And it's good enough.