Drilling a square hole

[crazyal]

I debated if this belongs here or in the welding section but here goes. The wear bar on my Kubota snow blower needed replacing. For $80 (with new bolts, nuts, and tax) I figured it was a little pricey but an easy solution. I just ordered generic grade 5 plow bolts vs buying the much more expensive ones from Kubota so maybe this had an impact on the problem. The problem was the countersunk hole isn't deep enough and the head of the plow bolt is slightly above the surface of the steel. The square part of the hole is a lot deeper than that the bolt needs. I just used the drill press with a 3/4" countersink to fix the problem.

This has me asking myself why not make it myself. I quickly looked into it but it seamed like a punch was an expensive option and the wobbly drill bit would require work and if not accurate enough the square hole wouldn't keep the bolt from spinning so I passed and just bought the part. It's just 1 1/2" x 3/8" mild steel. But now that I'm deepening the countersink holes anyway maybe I should rethink giving up on the idea of making my own.

The bolts are 3/8". I'm thinking that drilling a 3/8" hole then finding a way to make it square would probably be easiest. But I would like to hear what others have done. Here's a before and after.

 

[texasranger556]

You could try this

Machining 101: How to drill a square hole at home without special tools. - YouTube

Ave has tons of interesting videos, one of the few channels I keep track of on YouTube.

 

[4570Man]

I'd probably skip the square hole and weld the bolts in. Having to replace the bolts is way cheaper than an over priced edge.

 

[crazyal]

Some of the options I though of were:

1)I could just drill a 3/8" hole and countersink the steel on one side. I then could insert the bolt from the other side and weld it in place using the countersink to keep the weld flush with the steel. Once welded I would use a grinder to cut the heads off.

2) I could make the steel bar with threaded holes. That would require not too much work. A grinder would easily cut off the protruding bolts on the bottom of the steel wear bar making it flush.

Things to remember are:

1)The steel wear bar needs to sit flush on the steel edge on the bottom of the snow blower.

2)The steel bar does hit rocks frozen into the gravel driveway.

So if the bolt is welded it will need to have enough penetration to handle the sheer stress. If threaded in there needs to be enough material to handle any impact. Since this will be in the middle of winter I really don't want to find out that the edge broke free. Last spring one of the plow bolts on the end wore down enough so it pulled through. I knew it was close so when it happened I was ready. The steel edge snapped at the next bolt hole in. I just welded the bar back together but it was still a pain. I could always make the bar out of thicker metal, say 1 1/2" x 3/4" and replace it before it wears down too much. But it may not make sense price wise.

 

[flyerdan]

Punching a square hole would necessitate using carriage bolts, square heads would just go on through. I would probably opt for countersinking and welding in pieces of all thread cut to length. If that would be an acceptable permanent solution, maybe put a few extra holes in the blower itself so you can put a few more studs in for better support. Doing it that way, the materials should be cheap enough that you can make up an extra one while you're at it for a spare.

 

[chim]

For mine, I plug-welded pieces of stainless allthread into the bar, then bolted it on. That gives a smooth bottom for the wear bar. The nuts on the inside of the bucket don't interfere with anything.

 

[davedj1]

How about some snowmobile track studs? they come with an allen key head and they come in different lengths, you could grind off the tips once installed.
http://cdn3.vnexttech.com/snowmobiletrack/catalog/lg/204/signature-series_36493.jpg

 

[Oldpath05]

So why does the hole have to be square, I see a round bolt head, one's to high ones to low.

 

[GLyford]

I am guessing some of you are not familiar with plow bolts:

Similar to a carriage bolt, but it sits down inside a conical hole instead of protruding like a carriage bolt.
Commonly used to mount plow shares onto frames, etc. where a flush surface is desired.

My thoughts on the OP's problems are how much metal would need to come off to simply grind the heads flush to start with?

Since the square section is so short, it may take less time than you think to simply rough out the hole with a coarse square file.

 

[mnr60]

Have you thought about drilling round hole then squaring it out with die grinder?