Template done for a brush gaurd.

[ArdWrknTrk]

Drill presses don't typically have bearings suitable for side loads.
(or tables, or....)

Just a warning not to destroy a tool trying to make it do something it was never designed for.

[ArdWrknTrk]

A broach is a tool that is pushed through a hole to form it to another shape.
These are commonly used to cut keyways or make square, rectangular, or other polygonal shapes.

[Gary Lewis]

I'll let Jim speak to the broach question.  But when you mill you want the end mill's working point to be as close to the chuck as is possible.  So short mills put as far into the chuck as possible is best, and then put as much of the mill through the part as you can so you work at the top of the flutes.  Too much leverage will cause problems, especially when using a drill chuck instead of a collet.

[Gary Lewis]

Jim is right about the mill vs drill press.  A mill's column has bearings designed to take both end and side loads.  But most drill presses have bearings designed for end loading only.  So you have to be very gentle and work very slowly, and with very little leverage.  I've done it, but it isn't ideal at all.

[ArdWrknTrk]

I just googled 'press broach' and came up with a bunch of YouTube videos.

Imagine a square file with single cut teeth and a smooth pilot diameter on the end.
When this is forced into a pilot hole the taper of the broach makes each tooth take a slightly bigger cut.

You can use a arbor or hydraulic press but there are some rules of thumb re: # of teeth engaged depending on material thickness, lubrication, tooth form for CI, steel, red metals, aluminum, etc..

[reamer]

Thanks Guys, All of this will be "kept in mind"

[ArdWrknTrk]

What size is the square part of a bumper bolt?

I went with stainless carriage bolts when I had to replace my bumper.

[85lebaront2]

We had a square drill in the shipyard, it was a hollow square broach with a drill inside it, the drill was the size you wanted the resulting square hole to be and in a drill press or Bridgeport it would allow you to fairly quickly make square holes.

[reamer]

Well that didn't work... 1/2" end mill in my floor-drill press, any side load and the chuck falls out of the "press fit" into the head.
Must either by a bench-top milling machine, or figure another way to cut slotted holes....

[Gary Lewis]

Bummer!  The broach may be a better approach as you can get a square hole.

But, if you are considering going to a mill, let me tell you a bit about my experience with a 3N1 machine - Harbor Freight's #44142.  It worked, but wasn't as useful as I expected.  My learning was that a dedicated machine is better than an one-device-does-all.

Also, whatever the cost of the machine you can expect to double it with the tooling you'll need.  Maybe not right off the bat, but it won't be long.

[ArdWrknTrk]

That all seems like a huge investment and a lot of space taken up for a few square holes.

Would your plasma cutter be able to get a square hole close enough that it would clean up with a couple of strokes of a file?

[ArdWrknTrk]

Most of the 1/2" square push broaches I'm seeing have a minimum depth of cut of 1/2". (remember what I said about tooth engagement?)

I'll have a look at better sources, but a $200 piece of tooling that does just what you want using a press you already have seems like a deal.

[Gary Lewis]

Sometimes it gets down to what you want to do rather than logic.  If there's a way to use a broach for these holes rather than buying a mill then that's the way I'd recommend.  But the minimum 1/2" engagement is a concern.  However, can he stack the parts and broach the hole in two at one go?

In my case I'd always dreamed about having a mill and a lathe, so bought the 3N1 - and was disappointed.  So, in case you are thinking of going that way let me explain my issues.

First, the drill press part of it is poor.  There is just so little stroke on the quill, and no height adjustment on the table, so you have to build up the height of the part on small bits/holes, and for large bits/holes you can't get the part in.

The mill comes next, and it is acceptable for small things.  That's because there's still no height adjustment on the table so you have to shim the part up from the table..  Plus, the design of the machine leaves the head somewhat flexible, and that makes the cuts less than accurate.  I couldn't rely on the machine to cut the amount I dialed in, even on small cuts, and always had to measure and fudge.  On my big lathe it'll cut what you dial in.

Best was the lathe.  Still not as good as a larger dedicated lathe, but it usually got the job done. However, there was still too much flex and cuts weren't as accurate as my larger lathe, even if you made small cuts.

Then there's the room issue that Jim spoke of.  The 3N1 is the best in this aspect of any machine, but you still have to have the machine well away from the wall.  That's because many parts are too long to go on the table left/right and will have to go on front/back.

Anyway, just my thoughts.

[ArdWrknTrk]

If it is angle perhaps you could stack back to back forming a T.
Does this leave room for the ram to push the last tooth out the other side?

As long as the tool's next tooth is fully engaged in the workpiece before the previous one leaves I think you are okay.

We all know that with something like a bandsaw blade you want *more* than two teeth engaged at one time or you are going to strip them.

Chip loading is a factor as well.

Maybe a call to Dumore would be the best way to get an answer.

[Gary Lewis]

You are right, this would be angle pieces.  But maybe the back-to-back approach would work.

As for "We all know that with something like a bandsaw blade you want *more* than two teeth engaged at one time or you are going to strip them."  I didn't know that until ~10 years ago when I took a community college class on metalworking.  (Nor did I know about center drills and lots of other things like that.)  I had lots of hands-on as a kid, and Dad could fix anything, but he didn't have the machine shop training that really helped me - albeit later in life.

[ArdWrknTrk]

Before all the manufacturing disappeared around here there used to be little job shops that were based around one specialized process, or tool.

There were EDM shops, plating and anodizing shops, and one shop that was *literally* built around a 5,000 ton! press brake.

Any ironwork shop or fabricator should have a punch press and a 1/2" square punch & die.....
Or, buy the die for their press for ~$100

[ArdWrknTrk]

Funny, this should end up in my YouTube feed.
https://youtu.be/tc-3rNWcqio

Broaching operation of a crank handle from about 15:00 to 26:00

Anyway, good footage of the tool and how it's used.

[Gary Lewis]

Big brother is certainly watching.

But, I thought Handel was a composer, not something that needs broached.  

Anyway, that was cool.  I'd never seen a broach at work, so I now have a better understanding of the operation.  Thanks for sharing.

[reamer]

1/2" chrome-capped carriage bolt, (1/2" x 1/2" square under the cap).

[ArdWrknTrk]

Gary, I think we need a tinfoil hat emoji too....


It doesn't surprise me at all that Google would push something to me that I had typed into my phone and searched for in Chrome.
Their revenue comes from me clicking a link or having to watch an ad before I can see a video.