Tail stock - what's safer/better?

[PerryRT]

So I've been wondering something tonight. Tonight, I was cutting a 1/2" hole 3" deep in aluminum (for a tailstock die holder).

My 9x30 lathe has a tailstock with a little over 2" ram. I have drill bits longer than that and like tonight, I occasionally need holes deeper than that. This puts me in the situation where I can't finish cutting a hole to depth without making adjustments.

So I've got a choice. I start by advancing the drill into the workpiece as far as the tailstock ram will go, then either:

1) stop the lathe, retract the ram, then loosen and advance the tailstock so that the drill bit is in the hole, tighten the tailstock back down, start the lathe, and finish the cut.

OR

2) leave the lathe running but otherwise do the same as the above.

My impression is that the first method is more accurate, as advancing the drill bit/ram when the tailstock is loose rubs the sides of the hole, but the second is safer, as it doesn't have a cutting tool in contact with the work on startup ...

... but I'm really not excited about either method.

Anyone have a tip/better method for this?

 

[bronson]

The hole this time is 1/2 you could drill with the above method with 3/8 drill and then use a 3/8 boring bar with very light cuts. I personal do it both ways. I too run into this problem my tail stock only has a 2 1/4 reach. When adjusting tail stock be careful i do it running it does have a slight pucker effect. ;D Hopefully some way more experience people will chime in here.


Bronson

 

[n4zou]

Mark the depth of cut by wrapping some tape around the drill.
Drill as far as your tail stock allows then retract the drill bit.
It is safe to leave the motor on and the work turning.
Unlock the tail stock and move the drill deeper into the work, slowly.
Don't jam the drill into the work. Until you get the hang of it only slide
the drill/tail stock half way in before locking the tail stock down. With practice
you'll begin to naturally push the drill/tail stock in and lock it down just a
few thousands from the work face. Drills remove slightly more material than
it's diameter so moving the drill while the work is turning is safe. Any chips
remaining in the work will be scooped out by the drill as it's advanced in the
work to start another cut. Stopping the work can actually lead to problems.
Chips can get jammed between the work and the drill as the drill is pushed forward
when the work is not rotating. Always fully retract the drill from the work so chips
can be cleaned out every time the tail stock is unlocked before advancing the drill
into the work for additional cuts.

 

[Ken I]

Even when I have enough stroke on the tailstock I will cycle the tailstock back and forth for swarf clearance rather than wind the quill handwheel - (when drilling deep holes, deep meaning 4-5 times diameter).

My orignal tailstock locking mechanism was a PITB for this purpose so I modified it.

Can't say that it has any effect on diameter - as the previous post mentioned, drills tend to cut a little oversize anyway.

What you do need to be careful of is drill "wander" - a hole can go surprisingly awry.

Your drill needs to be properly sharpened and you need to get the start spot on - if your centre drill or spot drill wanders slightly - this will become greatly amplified during drilling.

If in doubt drill and bore the start of a deep drilling to ensure the drill gets off to a good start.

I recently discovered that some barstock can have a corckscrewed grain structure which plays havoc with deep drilling - it will not drill straight even when best practice is followed.

See my thread "I can't drill straight".
http://www.homemodelenginemachinist.com/index.php?topic=17258.msg177208#msg177208

Regards,

Ken

 

[Swede]

Here's a handy tip I "discovered" for tedious tailstock drilling...

Let's say you need to drill a deep hole 3/16", and we know that the flutes must be cleared a number of times before you get to depth. Most of the time, we count turns, so when we re-enter the hole, we can "hurry" up to where the virgin metal is. Sometimes we miss, and slam the bit into the hole bottom, with bad results.

Take a small o-ring that will cling to, but still slide, on the cutter. As you progress, the o-ring gets pushed up the drill bit to the right. When you retract to clear the flutes, the o-ring marks where you're at, and you can hurry the drill in right up to the o-ring. The o-ring can also be used to mark a depth target. Works better than tape and is easier to manipulate and remove.

As far as the OP, I have had good success by turning off the lathe, retracting, loosening the tail stock, then bumping with the heel of your palm to move the drill into the existing hole. Power back on, and you can then go deeper. It's not a bored hole, but works fine for roughing with little to no danger.