Those wretched cross-holes

I tried to drill a 3/16" cross-hole in a small steel cylinder (0.3125" diameter,

0.400" length). I clamped the cylinder by the ends (faced-off and therefore parallel) in a fairly substantial drill press vise, lined up the center and center-drilled first. Then I tried drilling the hole with a new 135 degree split point drill. The whole assembly started shaking, squealing and in spite of much cutting oil a lot of smoke developed. The drill run at appx. 800 rpm ( a big floor drill).

I made it through by gritting my teeth and closing my eyes. Afterward I examined the drill with a magnifying glass and found what I think are small pieces of steel welded on.

An identical drill from the same vendor has no difficulty drilling into steel otherwise.

This is not the first time I have had a problem cross-drilling holes. The clamping arrangements were different but the ensuing effects were pretty much the same.

I cannot understand why this is happening given the solid nature of clamping and all the other factors. I cannot see where flex would occur to produce the extreme form of chatter and subsequent rubbing (which is surely where the smoke and welding effects come from).

It was suggested to me that the part gets distorted as the drilling progresses. It is certainly possible however, the noise etc. starts almost as soon as the drill hits the piece.

I has occured to me that drilling round stock is essentially an interrupted cut until the drill has a chance to sink into the piece fully and engage the flutes 360 degrees. In that case, however, I would have expected the noise etc. to abate which did not happen. Perhaps by that time the drill is too damaged?

What is it about drilling cross holes in small parts that causes these things to happen?

I have tried different clamping arrangements in the past with essentially the same result. I could not really see any other way to clamp this piece differently considering its size and the size of the hole.

To solve this I can only think of drilling with progressively increasing drill sizes (for 3/16" !!!?) or clamping the piece in a 4-jaw chuck and drill it in a lathe.

Any other explanations or suggestions?

Reply to
Michael Koblic
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I conjecture that the material is work hardening. What would happen if you used a stub length drill, pecked, and (importantly) used more feed pressure on the quill?

Think Cole Drill Mode. :)

--Winston

Reply to
Winston

Winston fired this volley in news: snipped-for-privacy@news3.newsguy.com:

And... turn the drill clockwise!

LLoyd

Reply to
Lloyd E. Sponenburgh

Lloyd E. Sponenburgh mentioned:

*Clockwise* you say?

Thanks Lloyd, you may have saved me some time.

--Winston

Reply to
Winston

How cheap are your drills? I tend to use PTD most of the time,

My other thought, are you using 'mystery metal' ?

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Reply to
Wes

Ummm ... that leaves only a 1/16" "wall" to resist the clamping force. Maybe the part is collapsing a touch & binding on the bit. Just a WAG.

Try this: clamp with the axis parallel to the vise jaws. 90 degrees to what you're doing.

Bob

Reply to
Bob Engelhardt

What direction is that? All my clocks are digital...

Reply to
Michael Koblic

Cheap. But I thought even a cheap drill should last one hole - this was a new drill! However, you may have a point: I have stub drills bought from KBC Tools which I keep for the use with my Taig lathe. Nothing fancy, 118 degrees points. Cut way better than the Canadian Tire drills.

The metal should have been mild steel but I am beginning to wonder...I shall re-run the procedure with a certified mild steel and a stub drill as Winston suggested. I did peck and push...

Reply to
Michael Koblic

We've all been in the situation where it becomes clear that the cutting lips have turned into a 'bearing'.

Occasionally, one can rescue the situation by applying more force to break through the glasslike surface and the tool begins cutting once again. It's that large pressure which allows a Cole Drill to cut through stainless and tool steel using regular HSS bits.

If you have sufficient force on the quill, the cutting lips always stay below the work hardened area and it never binds up (for that reason).

You might be surprised how much force you can put on the quill with great results.

--Winston

Reply to
Winston

"Michael Koblic" fired this volley in news:85eum.211754$ snipped-for-privacy@newsfe19.iad:

That's the opposite of Widdershins.

LLoyd

Reply to
Lloyd E. Sponenburgh

Just go opposite of the NASCAR drivers.

Reply to
John Husvar

Hmm ... about 39 SFM. What was the material you are drilling? And was it hardened steel or mild?

Sounds like hardened steel.

The *same* steel?

[ ... ]

Note that the clamping may not be that solid. You are sure that the ends of the cylinder are parallel -- but the jaws of the vise may not be.

A quick-and-dirty way to get more grip is to put some cardboard (not the corrugated stuff -- what used to come in shirts from the laundry) between the workpiece and the moving jaw, leaving the fixed jaw to define the position of the workpiece.

Oh yes -- and the 3/16" drill bit is quite flexible too. A screw machine length drill bit would be shorter and thus less flexible.

And who made the drill bit? If Chinese, it is a pure guess as to how good a steel is in the drill bit. If a US manufacturer like Cleveland, you are going to be more certain of the quality of the steel, and if you need it, you can go to a cobalt steel which is tougher (and more expensive).

Can you identify what was shaking relative to what? In a drill press, there is flex in the column itself, the mounting of the table to the column, the mounting of the vise to the table, and usually the fit of the quill in the headstock casting.

Was the vise firmly bolted to the drill press table?

A milling machine is typically more rigid.

And some floor standing drill presses may as well be made of freshly cooked noodles. :-)

Again -- what steel were you drilling? A hardened mystery metal can be anything.

It doesn't -- for me. But I know what metal I am drilling.

Find out what the metal is which you are trying to drill, and how hardened it is. (How does a file do trying to cut it?) For some exotic metals, you should talk to the drill makers to see what they suggest.

Good Luck, DoN.

Reply to
DoN. Nichols

A mystery metal which I was probably wrongly lead to believe was mild steel.

A different one.

Ah! That is useful...Thanks.

Yes, that appears to be the consensus.

I cannot imagine that Canadian Tire sells anything but Chinese. They look pretty though...

In the end everything was shaking including myself. It is worth noting that I had a similar experience with a similar shape in my mini-mill but the details are now obscure, especially the nature of the metal.

I should remember but I do not. Somehow I think it was as I would normally clamp this sort of work but I do not always bolt the vise for a straightforward small hole. This, of course, was not it.

It is what it is. Bridgeport it ain't.

The experiment is to be repeated with some changes and bona fide mild steel.

Reply to
Michael Koblic

On Sep 24, 2:50=A0am, "Michael Koblic" wrote: ...

In my experience scrap-yard mystery metal and some hardware store CRS machine considerably better after annealing. Often the quickie 'water anneal' is enough; heat it red, quench when the glow disappears.

Milling or filing a flat makes cross-drilling easier, at least until the bit breaks through and grabs. A few times I've used a center drill beyond its intended depth to make a parallel-sided starting hole.

jsw

Reply to
Jim Wilkins

BTW -- if you want a really nice steel to machine (as long as you don't need to harden it), look for some 12L14 (very free turning leaded mild steel, and it produces a beautiful finish.

[ ... ]

Pretty as in "gold colored". This means that they have been TiN coated (Titanium Nitride, not the metal tin). If the surface appears to be somewhat frosted under the coating, it is likely to be a very poor metal. If the surface appears to have been polished before the TiN coating, it is more likely to be a good steel -- which they took the time to work with properly when fabricating the drill bit.

[ ... ]

Some things can be checked by touch. For example, with one hand, touch one finger to the vise and another to the table. This makes it fairly easy to tell if there is motion there. A similar test can detect motion of the workpiece in the vise -- but be careful in case the workpiece comes loose and starts spinning.

Also -- touch one finger to the headstock casting, and another to the side of the quill to see if that is loose.

[ ... ]

But something like a radial drill press is almost as rigid as a Bridgeport -- but much larger and heavier.

[ ... ]

Try 12L14 if you can get some. You will find it a true pleasure to machine.

Enjoy, DoN.

Reply to
DoN. Nichols

A quick look tells me the local supplier carries only 1.5" diameter rods in

12L14. evryone sells them in various diameters and lengths for peanuts. Including Amazon! But nobody ships to Canada. Some more local research is called for.

More doughnuts..

I kind of gathered they were TiN. however, to my untrained eye they look shiny. I do not have anything high quality to compare - those are covered with black oxide.

I will pay attention next time I run this test. I hope to eliminate this kerfaffle with a clamping jig. Sounds like clamping by the ends and leaving

1/16" inch to support the hole is probably not a thing to do.

Well, it ain't that either...:-)

There is a Zen-like quality to making steel wool on the Taig. When things go badly elsewhere, I try and turn something on the Taig. Like a security blanket. Funny, the mill does not have the same effect. I still experience a child-like wonder when I center drill a rod and the hole is...in the center!

Reply to
Michael Koblic

Whatever you do, do not resort to using the 1"- bar from someone's disused weight set. That is some of the worst machining material I have ever encountered - worse even than re-bar from Mexico. Gerry :-)} London, Canada

Reply to
Gerald Miller

Ummm ... I've used one of those weight bars & it was OK. Thinking that maybe it was an exception, I just went down & cut off a piece of another one that I have.

On the lathe with an HSS bit & 100 fpm or so it *was* crappy. Bad tearing. I tried a carbide bit at 400 fpm & it was pretty good:

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That's a finishing pass of about .003 DOC & .003 feed (the ruler is mm).

Once again it goes to show that YMMV, Bob

Reply to
Bob Engelhardt

Hmm ... 1.5" diameter is probably a pretty good size for some projects -- especially lathe ones. You'll want to get as long a rod as you can afford/(transport home) and have some way to cut it. The typical 4x6" horizontal/vertical bandsaw works well for this. I've got both 1-1/2" round 12L14 and whatever the hex size is which just barely fits through the 1-3/8" spindle bore. Grips nicely in the 3-jaw chuck.

Of course, for smaller projects, having something closer to the desired size is helpful -- in spite of a machinist friend at work who always used to claim "the best metal is in the middle" as he took a 3" chuck of round brass stock to make a 1/2" diameter part. Lots of chips. :-)

[ ... ]

O.K. Yes the finish varies with the intended function. Black oxide is nice for some materials, Polished parabolic flutes nicer for others, TiN coated for letting the chips flow out from yet others. My usual bits (the 118 piece set of number/letter/fractional and the cobalt steel set of number-size screw machine length bits are both polished, though not parabolic flute. The two sets which make up my stock of metric sizes are black oxide, and I don't use them often enough to have an opinion for my usual materials. My metric tap-and-drill set has everything TiN coated, but Cleveland brand bits and taps, so I know that they are good.

The 61-80 number sized set is polished -- if I examine them in a microscope. Otherwise, they hard enough to even see. :-)

[ ... ]

Was the workpiece hollow or solid metal? If solid, check whether your drill press vise has a horizontal V-groove, ideally with a Vertical one meeting it in the fixed jaw. These give a good grip, and the vertical V-groove gives access to the area which you want to cross-drill. (For that matter, you can take a short piece of material the same diameter, face off the ends and drill through the center just the size to accept the drill bit which you intend to use, and drop it down the vertical V-groove after inserting the workpiece in the horizontal V-groove. Then Tighten the vise and drill guided by the existing center hole. (If you're going to drill a lot of holes like this, make the guide out of drill rod, and harden it after machining (facing and drilling), so it will last longer. Probably a good idea to use a countersink to chamfer the hole at the upper end at least -- and probably both ends so you don't have to worry about which end is up.

[ ... ]

What you want for the Zen quality is a small shaper -- say a 7" one. You sit there watching the ram move in and out, with the workpiece moving sideways just a little during each backstroke. And the tool is a simple HSS lathe bit which you can grind as you wish.

Enjoy, DoN.

Reply to
DoN. Nichols

Hacksawing is one of the ways I get exercise.

However, even with such exemplary lifestyle I doubt I shall live long enough to machine anything out of a 1.5" bar on the Taig, 0.005" at a time. I made further enquiries with that wonder of a company, Fastenal. Their catalog shows only the 1.5" round in 12L14. A phone call to the branch here in town revealed that they could get 3/8", "but 10 feet length would be below the minimum order". The same company, branch 50 km away, can apparently sell single 3 ft rods of 3/8" just under $8.Which in US sells under $3.

It's back to the doughnuts!

I got a black oxide set of 118 degree point stub drills specifically for the Taig. They cut incomparably better in steel than the CT TiN. The chips come out of the holes ever so easily even if the hole is quite deep. The TiN cut for about 1/2" and then the chips stop flowing and the rubbing starts (I am talking certified mild steel now). No amount of lubricant seems to change that.

It was solid. Yes, there is a horizontal v-grove but the 5/16 diameter cylinder all but disappears in it and the vertical groove is not large enough to allow 3/16 drill through. Also, I am not sure how one would center the drill if the piece were held this way. Can you be certain that the vertical groove always centers automatically on the diameter of the piece held in the cross-grove (which would be mandatory if one used the guide made as you suggested)?

I used to drill similar pieces held in the horizontal v-grove *before* I cut them off. I tried to let them stick out to the side of the vise which allowed for proper centering and center drilling. Even then, the problem was that one had to let the piece stick out quite a bit to be able to get the chuck down to the piece without the top of the vise interfering. This was all well and good for center drilling but when one came to use the twist drill more chatter and rubbing resulted. I tried making an improvised machinist jack to support the end sticking out but it did not seem to help all that much. Mind you, it was a pretty miserable excuse for jack !

With the advent of Taig I was hoping that these problems were a thing of the past now that I could face off the opposite ends of the cylinder. Apparently not so.

Due to recession I shall have to stay with the Taig and chanting a mantra. BTW I wonder if one can make a mandala out of the steel wool and assorted chips.

Reply to
Michael Koblic

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