What's the secret to drilling through 1/4" angle iron?

[SPYDERLK]

A drill press with a low speed of 250 isnt made for drilling large holes IMO. Sounds like either a bench top model or benchtop that they just put on a floor stand. If you look at the literature I am sure it may only be rated for 3/4" holes.

Even locking the bed down in all axis' on the mill, drilling a large hole at a lower speed you see alot of movement. Wearing things out.

Mills werent made to drill. (allthough they can). Obviously the larger the mill the more ridgid, but most 1-2hp bridgeports with 9x49 table just arent that solid for large holes IMO. Especially used and wore out some.

Not to mention, with most mill setups with R-8, you are limited to using S&D bits with 1/2" shaft. Forget about using MT3 or MT4 bits, which are WAY more ridgid than a S&D bit. A good drillpress with MT4 spindle for 1-1/4" holes is WAY better than a 2HP bridgeport IMO

Im wondering at what sized drill press you are talking about that doesnt move around when a Bridgeport does. The whole idea of a mill is rigidity in every direction. A drill press only needs it straight down. If the Bridgeport has back gear for providing comparable low speeds I would just cut a big bit down to 7/8 shank and use the appropriate R8 collet tight. I cant see what would be moving around if the slides were locked.
... Course, having a mill it would be special for me to buy a really big bit. Id just pilot with the biggest I have and then bore the hole to final size.:confused3:
,,,larry

 

[LD1]

It's hard to explain just what is moving around. I just know it does. You can see the whole table moving around I. A circular motion. Sure a drill press moves a bit too. But I am less concerned about a little slop in the drill press than I am in the mill.

It's kinda like drilling a hole with and endmill. (Which don't drill well at all as they aren't designed for it.)

Granted, the mill ain't new by any means, but certainly not wore out. Every one of the mills I have used behave the same way drilling larger holes. Each mill has its limits. The 5hp aTrump w/10x54 table that weighed 4600# would run a larger bit better than a 1hp BP w/9x49 that might weigh 2000#.

Anyone who has drilled larger holes (1"+) with a standard bit on smaller BP mills should know what I am talking about.

 

[MossRoad]

I was surprised at 75 responses to a question about drilling holes. I expected some derogatory remarks at the OP and was glad to see only help.

Well, he didn't take pictures! That's about as derogatory as it gets... :laughing:

 

[4570Man]

An end mill sure doesn't drill a hole good. They are designed to cut on the outside edge. They usually don't have cutters in the center. It is kinda surprising, but the table does move a little on the milling machine.

 

[SIMassey]

It's hard to explain just what is moving around. I just know it does. You can see the whole table moving around I. A circular motion. Sure a drill press moves a bit too. But I am less concerned about a little slop in the drill press than I am in the mill.

It's kinda like drilling a hole with and endmill. (Which don't drill well at all as they aren't designed for it.)

Granted, the mill ain't new by any means, but certainly not wore out. Every one of the mills I have used behave the same way drilling larger holes. Each mill has its limits. The 5hp aTrump w/10x54 table that weighed 4600# would run a larger bit better than a 1hp BP w/9x49 that might weigh 2000#.

Anyone who has drilled larger holes (1"+) with a standard bit on smaller BP mills should know what I am talking about.

Even a large radial arm drill will move around when drilling large holes, and that's what they were designed to do, drill holes!!! These machines have locking mechanisms for the column and head. The arm will lift when the power feed is engaged, and if kicked out during the cut,the arm drops and makes an awful bang. As the drill starts to break through,the weight of the arm sort of increases the feed per revolution. This action takes place with drills properly sharpened on center with the proper relief, using drill fixtures with hardened drill bushings. Large horizontal or vertical boring mills will provide the most rigidity. Not something a normal home workshop has.

BTW, ball endmills make great drills for removing stuck socket head cap screws. If done with a standard two flute twist drill, the corners of the flutes fracture on the work hardened hex socket. I've used this method in mills and with hand drills.

Something else, I plunge cut .0625 standard endmills through hardened 420 stainless. Granted the material is only .020 inches thick but it can be done.

 

[4570Man]

I usually don't drill large holes in the mill. If I need do drill a hole bigger than 1.5 inches I usually bore them. Most of my larger hole drilling is making bushings, and I drill those it the lathe to close to their final size then turn out the rest.

 

[LD1]

An end mill sure doesn't drill a hole good. They are designed to cut on the outside edge. They usually don't have cutters in the center. It is kinda surprising, but the table does move a little on the milling machine.

That movement you are talking about is the same movement I am talking about.

A 3/4"-1" drill bit makes the mill table move or "wobble" around about the same as trying to drill with a 3/8" or 1/2" end mill. I don't like it.

On a drill press, I let the movement be between the vise and the table. Sometimes u don't even clamp the vise to the table. And when I do, I do it loosely just so the part and vise cannot climb the bit when breaking through. The handle end of the vise is placed up against the left side of the column to counter the rotating force.

If I need accurate placement of larger holes, I pilot with the mill and small bit. Then hog with the drill press as described above. If its an odd shaped part that needs clamped directly to the table a trick for centering over a pilot hole:

Have the part very loosley clamped. Run the drill slowly backwards and press down like you are trying to drill. Once it self centers, shut the drill off but keep pressure on it. Tighten clamps, let off pressure, start drill in forward and proceed to drilling.

 

[SIMassey]

It's hard to explain just what is moving around. I just know it does. You can see the whole table moving around I. A circular motion. Sure a drill press moves a bit too. But I am less concerned about a little slop in the drill press than I am in the mill.

Anyone who has drilled larger holes (1"+) with a standard bit on smaller BP mills should know what I am talking about.

A Bridgeport style vertical milling machine has many areas that allow possible movement,

The overarm swivels on the column

The overarm move in and out on the column

The head swivels to the right and left along the X axis

The head swivels forward and back along the Y axis

The quill moves up and down along the Z axis

The knee moves up and down

The table moves left and right

The cross slide moves in and out

The last three movements are adjustable with Gibbs but has its limits with wear. All the rest are tightened during cutting operations.

The quill can be snugged with its lockscrew but cannot correct wear

You see, the machine has many connections that can become loose and cause movement under heavy machining cuts. Every machine and cutting tool has its limitations.

 

[4570Man]

The head is solid as a big rock. It is just the table that moves a little.

 

[Mace Canute]

Probably a NMTB40 taper. Surprised it is only a 2HP mill though. And probably has a 10x54 or larger bed.

I am guessing you havent ran small little 1 or 1.5HP bridgeport with 9x49 table and R-8 1/2" collet and 1" S&D bit? Cause if you had, you would much prefer a decent drill press for its rigidity.

Most people, if they are lucky enough to own a mill, dont have a huge one. And on a small mill with large holes.....just dont work well in my experience.

At work, we have a 2hp BP with 9x49 table. It is pretty frowned upon if you are caught using it for anything over 1/2" drill. We do have 3 nice presses. A 5hp clausing with ~8" round column, a 3HP variable speed (powered with an internal VFD), with maybe a 5" column, and a huge 10HP radial arm that must weigh 4 or 5 ton.

Either way, a mill was designed to be a mill, not a drill press. The quill and power feed (if it has it), just arent as heavy, and you are limited by the smallish keyway on the R8 collet.

Bridgeport actually rates their mills at 3/8" maximum drill diameter for power feed, and 3/4" when drilling manually. There is a reason for that.

Most small benchtop drill presses are rated at 3/4". So why would you choose to wear out an expensive mill vs a cheapy press.

The purpose of the small pin that engages that keyway in collets is just to hold the collet from spinning while the drawbar is being threaded in before it is torqued. It is not meant to be a positive drive feature for the collet and if/when you spin a collet in the spindle you will be cursing yourself for not having previously removed it.