Machinists, anyone ever make a push broach?

[lil_Blue_Ford]

So, I’m not sure I’m really much of a machinist with never having run a CNC, mill or lathe. I do have a couple basic machinist and blacksmithing books though and I have a grasp of the basics to a minor degree.

That said, I have a problem that I think can be solved with a push broach or whatever you want to call it. I bought a replacement stump jumper for my brush hog awhile back and it doesn’t exactly fit. It has tapered groves for splines on the shaft to fit in like this \_/ and the problem is they are too narrow. A family friend took it to two of the machinists he knows and neither was able to solve the problem. I don’t see why one couldn’t fashion a push broach and holder and just scrape the grooves wider one at a time. There’s 12 grooves to widen and I want to say it’s a 1.25” hole in the middle of them.

I’ve never attempted anything like this however, so I’m looking for some input, otherwise I’m just going to take my best guess based on my limited knowledge and hope for the best.

 

[franklin2]

First thing to do is take a file and run it over the splined area. Nothing dramatic, you do not have to push very hard, but see if it wants to cut the splines, or is the file just vibrating over the splines and not doing anything. If it's not wanted to cut, then the splines are hardened and any modifications will have to be done with a grinder or stone of some sort.

 

[lil_Blue_Ford]

First thing to do is take a file and run it over the splined area. Nothing dramatic, you do not have to push very hard, but see if it wants to cut the splines, or is the file just vibrating over the splines and not doing anything. If it's not wanted to cut, then the splines are hardened and any modifications will have to be done with a grinder or stone of some sort.

It’s powder coated and the file doesn’t seem to like that, which I think is a decent part of my problem

 

[pjtoledo]

how 'bout a pic?
splines on the male or female need enlarged?

for enlarging a hole you would want a tight fitting stud with only 1 groove and rotate it. grind a tool bit to fit the groove.
the hardness of the splines will complicate things. hardened parts can be softened by annealing, then machined, then re-hardened.

disclaimer, I'm not a hard core machinist.
try these guys:
hobby-machinist.com

 

[85_Ranger4x4]

It’s powder coated and the file doesn’t seem to like that, which I think is a decent part of my problem

Wire wheel the powdercoat away before you do anything. Nothing will like dealing with that crap.

Then try a file or whatever, decent chance the shaft will be at least surface hardened though.