If you insist on really needing several set screws in your pinion take it to a machine shop and have a skilled machinist do it right. That fact that your breaking drill bits says your doing something wrong.

How about you just get a new pinion gear from one of the reputable manufacturers. Then clean the set screw, and threads in the pinion with some solvent. You see any manufacturing oil or contamination will chemically alter the loctite, which renders it useless. Also in all likelyhood the threads on the pinion that is giving you problems are damaged, which prevents the loctite from curing to full strength. The way I look at it my time is worth way more than the cost of a pinion, so to go through all of that effort just to save a few bucks seems stupid to me. So, if you have the right tools, you could add a second set screw, but the overwhelming majority here are going to say replace the pinion, because that is the smart and easy thing to do. If you are dumb, or like doing things the hard way, then by all means, drill that hole.

If the motor shaft does not have a flat section on it, grind one into it, this will give the set screw more purchase on the shaft and make it less likely to back out.

filing the tip of the set screw flat will help it stay on.

I am not familiar with this type of threadlocker. With the liquid blue threadlocker it is best to let the product dry over night. How long does one have to let the "chapstick" type threadlocker dry for?

Okay since I have been made to sound inept I think I need to say a few things about the process I used to drill it...put pinion gear in a vise bolt vise down to drill press platform spray drill bit continuously with cutting oil and carbon steel bit does not stand up to hardened steel well at all...I do work in a manufacturing plant and had an interesting conversation with the Sandvik solutions manager that comes to my plant frequently and we were discussing the flaws in using a single set screw to hold onto something spinning at 60 tho rpm, when I design a process to machine the idea of a part that I am turning I use a drill bit held by a split bushing with set screws because I am spinning the bit at a rapid rpm without the spilt bushing and set screws it does not hang onto it well so as a result I thought well maybe if I reverse the way I am mounting the pinion gear and red Loctite it will work better I have two pinion gears with stripped out threads part of the reason I want to redrill a pinion is so that I may re use some stripped out gears and to make it so that I am grabbing the gear that's rotating about a shaft spinning at 60-65tho rpm in a manner so that it doesn't slip off blue Loctite seems to only work for so long before the heat burns up the bond btwn it and the carbon steel set screw and hardened gear...As far as a reputable gear goes I have a stripped castle and Robinson gear and since I am quite tired of having good gears sit idle because they are stripped I believe there is a way to drill and tap them so that they may be used once again I'm thinking heat the gear and then use a Sandvik coromill drill bit to drill it now that just leaves the hard part of tapping it because after reading through many of the tool supplier catalogs on my desk I haven't found a threading tool that's not carbon steel for doing it by hand I have not ventured down the road yet of writing the code to put it in a milling machine and try threading it with that, if it was not a 40 thousandths hole I was trying to tap I think it would be no problem but since it is it's a little more challenging

That should have said the ID of something and not idea

Also I have drilled out and tapped hardened steel before but it was prolly only 35 not 50 like these pinion gears are I realize pinion gears aren't the most expensive part in the world but it's the bottom line of I know it can be done I just thought maybe someone other than myself might ponder it and have some suggestions on how to do it

I also had the thought of using a boring bar on a HMC to bore it out but that still leaves the issue of turning the threads into the new hole


Another reason why I want to do this...I'm an engineer and I love a challenge

There is only so much time in any given person's life.

For me, I would rather spend the time running the car than trying to rescue a damaged, used pinion.

If you think rescuing a damaged, used pinion is more fun and challenging than running the car, you should probably figure out how to do it yourself. The consensus here seems to be "buy a new pinion."

Well it certainly appears as though you have access to the right tooling, but that still doesn't mean that you can pull this one off successfully. Did you ever stop to think that with something this small that the machine work might need to be done prior to the hardening process? You obviously can't go back in time and un-harden the gear, so maybe it is just one of those things that is beyond the capability of the tooling you have at your disposal. Could something out there exist that could do what you want? Probably, but at what cost? You have to remember, you're not working for Skunkworks, you're playing with a toy car.

By the way, a good engineer would be aware of all this. One that is going to school at Penn State, and has a summer internship at a machine shop might have a difficult time understanding that in engineering, just because you can redesign something, doesn't mean you have too. Here in the real world you have profit margin. If one set screw works, why spend the extra money to have 2?

Set screws or screws have a oval tip use your dremel to bring the end completely flat this will give you better surface grip when torquing down

You should try asking your questions on a forum like practicalmachinist . com
you may get better answers than what you get here.

You say that, " if it was not a 40 thousandths hole I was trying to tap".
I find it hard to believe you are using a set screw that is so small that only a .040 hole is required prior to tapping. FYI a 4-40 threaded hole would require a tap drill in the .090 range depending on the % thread you desired.

Actually I'm not an intern, Im a counstulant engineer because I already have one degree and yes I agree they are typically tapped before hardening but I just felt its silly to have 2 or 3 wasted gears I definitely have the equipment and getting a carbide bit isn't the issue because I figured out I can go up in screw size and i tested the gears 35 and 38 Rockwell so here's my thought process on how to accomplish this corodrill bit rates for up to 50 rockwell so then find a tap and throw it in the mill write the program and have the mill tap it
And I just love the engineering challenge it's kinda why I want to design an RC truck and machine out all the components at some point and I believe I have figured out how I'm going to drill it with the mill too

Hey, me again.
Just wondering if you drill another hole in the collar is there going to be enough 'meat' left so it doesn't just break off after all the hard work?

Boom you have it 100 percent correct the tap I was looking at is .093

That is also an excellent question and I'm thinking that based on the hardness of the gear it shouldn't chatter on the shaft and fail or fail from the weakling however I could probably use inventor and software like deform to see if it will fail I foresee some finite element analysis software in the future and also I'm wondering how hard it would be to just machine my own pinions and heat treat them after