Enlarging a drilled hole, best procedure?

Trying to drill out a 1/2 hole to accept a 9/16 bolt. Im adapting a lower ball joint from a drum to a disk spindle on a Mopar A body and the ONLY difference between the 2 are the mounting bolt sizes. I bought a decent HSS 9/16 drill bit (made in USA even!) and chucked it in my cheap azz drill press. Started drilling with cutting oil and 30 seconds later the drill stopped penetrating, just spinning there. I got about 2mm into the forged piece and the drill bit looks like it already dulled at the only place it contacted the piece, about 2mm into the corner of the leading cutting edge. What gives? Do I need to use a coring bit (looked it up and it is designed to enlarge holes!) or a cobalt bit, or just a more powerful press? I stalled it a few times putting too much feed on it, but it had already stopped cutting. These LBJ's arent made of titanium, why is my HSS bit already toast? Ready to take these to a machine shop and let them do them, but Im all for the DIY approach. My die grinder with a carbide bit broke at the bearing so I cant use that either. Thanks.

 

Probably running too fast. Use low rpm.

 

Cobalt bits and a low rpm range on the drill press. If the drill speed is too fast you'll melt the cutting edge on the bit.

 

yeah, I had it at its lowest spidle speed but I did try a pretty fast Makita cordless when I started to stall it. Oh well, back to sharpening my HSS...

 

Use a reamer.

 

Step bits.

 

I used them when I did not have a reamer, works pretty well.

 

I was going to suggest a step bit, but I think the material is kind of thick for that. Those are the best for drilling sheet metal.

 

C'mon guys, "buy new ball joints"? There $85 a pop, and a drill bit is $17.
Step bit? Find one that ends at 9/16th and is designed to drill through 1.5 inches of forged iron....
Reamer, maybe. The cost of a 9/16 reamer that looks like I may be able to use it? $95...
Where did the frugality go? Keep 'em coming, Im all ears, but a little short on dough....Oh yeah, did a ghetto sharpening of the bit on a grinding wheel and almost got through one of the holes. Seems to be working if the bit would remain sharp for more than about 2 minutes under low speed and cutting oil. Somewhere suggested llubing/cooling with water as it bites "harder"?

 

First, you never said it was 1.5" thick, that makes a huge difference. This is pretty much going to be a case if you cant slow your drill down to the speed it needs to do it right, you will just about have to hire someone that can.

 

An old shop guy I knew reground the cutting faces on a bit to cut tough metal.

The actual "pointed" end looked the same angle, but the two cutting faces were not sharp. Best way to describe it was sort of looking at a masonary bit that has two almost flat cutting edges. He ground them less flat than that, but I hope you get the idea.

It worked good with a drillpress and cutting oil. Takes more pressure, but holds the edge longer.

 

I'm sorry but if you don't have $170 for a crucial parts of your car then I'd wait until you have the money.

 

Where are you buying your bits? I had the same problem because I was buying what I *thought* were good bits, "rated" to cut through steel, "cobalt", the whole shabang. I wound up going to Sears to find a decent set of inexpensive drill press bits that would actually do the job and not get dull. The old guy who worked there told me that all the new bits out there are sh*t for the most part, even though they're telling you they aren't. As a kid I remember going to the Do It Center and buying good ones all day long. Still have them in TN 20 years later. Cheap Chinese crap now. The ones I bought were 20 bucks each and made in the USA. I'll be d*mn if they haven't drilled through their fair share of steel and are still sharp as a tack. Only had to use minimal drilling fluid, too.

*BTW* I've done a good amount of drilling and not on a drill press with these bits and my wireless DeWalt hammer drill. I never use anything *but* a hammer drill when working on parts of my car that I can't remove (not a frame off rebuild). I mistakenly tried a non-hammer drill and almost broke both my wrists when the bit caught on something. Several other guys on here that weren't so lucky have the scars to show for it. Also, I always drill a nice pilot hole so the bit doesn't try and go off track and leave me with a crooked ass hole or one that's too durn big/egg shaped/etc.

 

The key element here is buried deep in your post. You're drilling Titanium. The speeds (RPM of drill press spindle)and feeds (advance per revolution of the drill) are hugely reduce over what you would use for steel. Start at around 220 RPM and a feed of about 1 IPM (25.4 MMPM). Since you're probably hand feeding you need to keep enough pressure to curl a chip but pulling the handle for all you're worth. By-all-means, you need a properly sharpened drill, too. A rigid set-up is also needed. A knee mill would be the best place to open these holes.

That's why Titanium is an "aerospace" material. It's expensive as raw material, nasty to machine (it catches fire - our company's fire department insists that we machine it using water soluble coolant), and only used in the design when absolutely required.

 

I am pretty sure he is beyond the pilot hole procedure..

 

he said.. "These LBJ's arent made of titanium,"

 

Nothing wrong with a little "over enlightenment".

 

Start with the next largest drill in your index bigger than the hole you have and step up in very small increments. That way the drill isn't removing much material with each pass so it won't hang up or twist out of your chuck. Go slow and use some lubricant.

 

Good advice, but all my drill index went up to was 1/2.

OK, let me back up a little The LBJ's on a Mopar A body are integral, they are made into the arm the tie rods bolt up to, not like an upper that is just the ball joint that is screwed into the upper A arm or a Ford that takes 3 bolts. The arm is about 1.25 inches thick where the 2 through bolts go and thread into the spindle. For some reason the drum got 1/2 bolts that were also used to hold the backing plate on so there was a castle nut on the other side. The disk setup used a threaded spindle that the 9/16 fine thread grade 8 bolts threaded into through the lower ball joints. They arent titanium, but sure seem to be when the drill bit is dust.The 9/16 drill bit is made by Norseman, "super premium black and gold", St. Paul, MN.. union made, yadda yadda. I think its burning up because the only part that is cutting and contacting the piece is the outer 1/32 of the cutting edge so all the heat is concentrated on that small area and has no where to go. Ill just go low and slow, and Ill get the bit professionally sharpened Monday...thanks.

 

He's going from .500 to .567, not alot of "next largest" to choose from there....

 

Drill bit speed should be about 125 rpm; use a good sulphur-base cutting oil such as "sulflo" and just enough pressure to see a continuous cutting curling from the bit. Drilling forged steel from 0.500 to 0.625 in one operation should be absolutely no problem - no matter the depth. Sounds to me as though your drill press spindle is running way too fast. If you have to buy a new drill bit, get a German-made bit with a three-sided shank. The bit will never slip in the chuck, but make sure the work piece is firmly held down - don't hand hold.

 

Yup, it a 3 sided bit, and the LBJ is wedged against rotation on the press stand and is C-clamped to the base. I cant get the 5 speed spindle speed under 620. 2 revs per second? Im Too fast...Im getting there..

 

Yes you are to fast. Half that would still be plenty fast.

 

You may ave already work hardened the area already drilling that fast,it real easy to do.Cobalt drill real sharp and slow may get through it or carbide is the next choice.That aint easy either as it will chip or break if its not rigid enough of a set up.Good luck.

 

http://www.monroefluid.com/products/tapping-fluids/cool-tool-ii

 

Best thing since sliced bread.

 

man, if you can't enlarge a simple hole, better find a new hobby!

 

And of course you knew everything from birth.
Better start bottling them genes mate.
Worth gold...

 

Use at least a cobalt bit and get some cutting oil while you're at it. That will keep your bit cool and help cut the metal. If you try to force it through the drill bit will just heat up and dull in a heartbeat. Bet we've all been there, done that, said the bad words.

 

Almost no "hobby grade" drill press these days will turn slow enough for even 3/8" drills, let alone 1/2". And by 'hobby' I mean the cheap imports as well as box-store Rigids and Deltas.

As noted above, you needed about 125 rpm, certainly no more than 200. You were running three to four times too fast, and what happened is the tip of the drill got hot, the corner lost it's edge, and all of a sudden it was just rubbing. That work-hardened the surface, compounding the problem.

At this point, you're going to have to do some damage control.

You're going to need, at the very least, a drill or better yet, a mill, that can go down to at least 180 to 200 rpm- the lower, the better.

Mount the part solidly and align it with the spindle. (or, you know, vice-versa. ) Resharpen the drill carefully, and you might even move the point angle out to 140 degrees. (Flatten the tip.)

Using a lot of good heavy black cutting oil (look for the stuff that says "lard based" and "sulfurized" if you can find it) you're going to have to carefully peck at the hard spot. If you're lucky, it'll still be just soft enough to drill, but even here, expect to only get a turn or three before the drill chips.

Once it does, stop immediately. That's why you'll need to "peck" at it- don't let the drill idle (rub.) Keep an eye on the drill tips- once the points show the least bit of damage, stop drilling and resharpen the bit.

If you're lucky, a half-dozen cycles of this will get you through the hard spot, and you can continue your way through normally.

If you're NOT lucky, and the spot is too hard to drill, you're going to need a carbide drill, or better yet, a carbide endmill. Neither will be cheap, and it may prove easier for you to just take the part to a machine shop, tell them what happened, and have them drill it.

Let us know what happens.

Doc.