drilling hole in 1" 304 stainless steel rod

[Rickk]

I aquired some 1" diameter 304 stainless steel rod that I plan on using as axles for my carronade.  At frist I thought about threading the ends and using nuts to retail the wheels but I am having second thoughts about threading 1"" stainless with a threading die, and don't have access to lathe. I have threaded 1/2 inch with a hex threding die, and I think that 1/2 inch is hard to do, and I am thinking that 1" will be even harder.  On top of that, I am having problems finding suitable nuts (1 inch square stainless would be preferred).

So, I talked myself out of threading it, and have switched to plan B, which would be to drill thru the side of the rods on each end and put a retaining pin of some sort. This may be closer to traditional anyway. I'm not sure yet, but I would think the thru-hole would be something like 3/16 to 1/4".

Does anyone know how easy or hard it is going to be to drill thru this stuff? I have no idea if 304 is soft or hard.

I have drilled holes in round things in the past and know that drills tend to wander when you try to start them. Will I get a drill to start in the right place by just punching a dimple with a hammer and center punch, or is there a better way? Maybe I should grind a little flat spot and center punch that?

I have a reasonably large drill press to work with... nothing fancier.

HSS, or Cobalt drills? I can resharpen them, so I don't care if I wear them out. Cobalt drills I seem to be able to break easier, so if I don't need to use one I prefer not to.

[Smokin Joe]

300 series is a ---   Use a cobalt bit and slow speed.

[Cat Whisperer]

Long bit will be more likely to break; start with the shortest bit you own, switch to longer as needed.

Using a center drill will help locate the hole accurately for drilling.

[Thunderpaw]

Mill a small flat first, spot drill, then drill. Use cutting fluid, coolant, or even a spray bottle of ice water, just keep things cool.

[GGaskill]

There are two kinds of drills designed to drill where you start them.  The common one is the "COMBINED DRILL & COUNTERSINK" which looks like this:



It is used for starting holes and cutting center countersinks for lathe centers.

The other is the "SPOTTING DRILL" which looks like this:



It is used in CNC machines to start holes. 

I have frequently used the combined drill and countersink (normally called a center drill) and it works well and is not excessively expensive.  It does come in strange sizes.  I have not used spotting drills so I can't give any personal experience with them.  Once you have started the hole, switch to a normal twist drill without moving the work piece (which should be clamped in place.)

[irishman]

Rick-
We all have different approaches to these problems.  Here are my thoughts: 
First, I think you can get through this with nice results.
Second, strictly from the standpoint of a drill wandering as it cuts through, I would recommend 1/4" over the 3/16ths.

My opinion about finding the center is this:  use the smallest, shortest drill, with the highest spindle speed, no fluid.  Stand looking down the rod after having measured, aligned, realigned, so you know it is in the center. Touch that drill to your axle, and if it is in the center, it won't walk to the left or right, leaving a polished trail behind.  If the drill point walks off center, recenter the rod.

Using cutting fluid, reduce the spindle feed by one if you have a four speed and two if you have more.

You are ready to start cutting.   Visualize the drill cutting through the stainless and concentrate on cutting, feeling continual movement as the drill cuts.  When the drill is cutting, it is cooling itself to some degree.  When it is not cutting, it is heating and destroying its ability to cut.  The continuity of the feed/cutting speed is important.  Once you feel it cutting, force it to maintain the same rate, until it fights you.  Then pull the drill out, add more cutting fluid, and let it cool down if necessary.  HSS drill should be fine, easily resharpened as necessary, but I would always start with a new one because if it isn't sharpened perfectly, it will walk and not come out 180 degrees from where it went in.

The next ghost waiting to bite you is at breakthrough/  Set your stop to make you stop and re-oil before you go for the final cut, and take that real easy from a feed standpoint.
I think you will get through this with good results, and the heavier than average drill press, is a major factor, gives rigidity.

Michael

[Cat Whisperer]

Agree with all of the above, I'd just add:  use a good vice.  (Should be obvious.)

[irishman]

CW, I second that.  The ultimate luxury would be to have a chunk of that 1" 304 to "learn" through about 10 holes. By then, you would know when it is cutting right and when it's not...just like learing to ride a bicycle!
     Michael

[Rickk]

I have 2 pieces, each 24 inches long. They will ultimately be only about 20 inches, so there was room for a screwup.

That being the case, I simply "went for it". I used a 3/16 inch drill because I had a couple of shorter ones that were freshly sharpened.

I punched a dimple with a center punch. That may or may not have been a good idea. I am assuming that the drill started in the dimple, but it apparently wasn't eactly unter the center of the drill chuck. Before I got in to far I saw the drill wobling, telling me that it was not properly centered unter the chuck. I loosened the vise from the drill table and moved it to relieve tension on the drill.

I continued drilling. I had the drill speed set as low as possible, and I gave it quite a bit of musle on the press. Once it got itself burried fully into the metal I was gettting a single continuous chip, which in my mind meant it was cutting nicely. I stopped every time I had about a 6 inch length of chip and backed out, cleaned the drill off, and filled the hole to the top with 30 weight oil out of my oil can. The metal didn't seem super-hard... the drill was pretty much cutting as well at the end as it was in the beginning.

Micheal, you were right about the "break thru". I stopped just shy of it and eased it thru with less pressure. I felt it bind as it exited. I was pretty sure I was going to break the bit, but luck was with me and it survived.

I am not 100% positive about the hole size I want. I am going to Tractor Supply in the next couple days to find some pins that will work for this, and drill to fit that. I am thinking something maybe like this for now... untill a better idea comes along:

Am I better off drilling a 3/16 inch hole first and then enlarging it to whatever I decide is the final size or should I go for it all at once? I could tell the drill was working pretty hard making this 3/16 hole. I am not sure what would happen if I used something like a 9/32 inch drill and made a single pass with it. I hate it when the drill spins in the chuck.



On the other hand, I seem to think that there is sometimes a chance of breaking a bit when enlarging a pilot hole. I think that it is just to easy to go too fast maybe and then it grabs more than it can hande.

What do you experts recommend... drill it to final size in one pass or step up with two different drill sizes?

[Rickk]

I am answering my own question, at least partially. Drilling in two steps sucked. The second drill kept grabing.

I have settled on a pin, and it is .230 diameter. It is not the one in the previous picture, but rather this one:


I will try a second hole with a single pass of a 1/4 inch drill and see what happens.

[Cat Whisperer]

You're doing it RIGHT!

Asking, trying, coming to your own conclusions from EXPERIENCE.

Good choice on the pin - FUNCTIONAL.

[Rickk]

I went to the hardware store down the street (the one that hires 18-21 year old cute college girls) this morning and looked in the drill isle.

What I found was a drill intended to be a "pilot drill" for a holesaw. It is a 1/4 inch drill that is only 2 3/4 inch long, 135 degree split point, and has a triangle ground shank to fit in a drill chuck without slipping. You need that for a holesaw because of the tremendous torque needed to turn the saw. It is a Century P/N 05307 if anyone cares to know that much detail.

It was only HSS, not cobalt, but worked like a charm.

I took the side of a flat file and spent about 30 seconds making a small flat spot on the side of the 1" rod where I planned on drilling. There was no drill wander at all.

One thing I realized yesterday while drilling in two steps was that once the first drill broke thru there was nothing to hold the oil. With a single pass you can back the drill out every 0.10 or so, fill the hole with 30W oil, and keep everything cool and lubricated.

This drill didn't make a long continuous chip, but rather many smaller chips. I worked great anyway. It only took about 2 minutes to finish the hole with no smoke or drill discoloration.