large hole boring

[rampa room artillery]

 what would you recommend for large hole boring I want to use a 4.5 in spade but i have a number 2 morris taper in the tail stock.
  and all the large spade bit holders are like number 5 MT   ,  will a number 2 MT handle the bit? or is that too much to turn. ?

 rick bryan

[GGaskill]

You might make a #5 holder that would bolt to the cross slide.  It would be easier to use, too.

[Cat Whisperer]

Don't forget to get a good grip on the other end of the tube as well!

(I too am interested in hearing of folks that have done such LARGE hole drilling.)

[Zulu]

Don't forget to get a good grip on the other end of the tube as well!

(I too am interested in hearing of folks that have done such LARGE hole drilling.)

5" diameter!
Oh wait, you mean in steel not wood.
Zulu

[armorer77]

I have had problems holding a 2.5" drill in a 4MT tailstock . I got 6" deep before it hung .

[GGaskill]

One thing that is really important in drilling holes using Morse taper drills is to thoroughly clean both the drill and socket.  ALL oil needs to be removed or you will not get maximum grip from the system.  Use a solvent several times, especially in the socket.

[rampa room artillery]

any thoughts on drilling a hole in the tailstock so you can put a removable pin in the MT connection??

rick bryan

[GGaskill]

any thoughts on drilling a hole in the tailstock so you can put a removable pin in the MT connection??

I've never heard of anyone doing something like that so I wouldn't recommend it.  The question would be if the taper grip fails, is the torque so high that a cross pin wouldn't be able to carry the load?  It's been too long since I took the course for me to be able to calculate this.

[Cat Whisperer]

any thoughts on drilling a hole in the tailstock so you can put a removable pin in the MT connection??

rick bryan

Hmmm.  Seems to me that (at least it did a month or so ago) the serious bits with a morse taper have a flat blade to prevent them from turning by fitting into a slot deep inside the morse taper in the tailstock.

[dan610324]

doesnt all drill bits have that blade ??
here in sweden I never seen one without it

[GGaskill]

You are referring to the tang at the rear of a Morse taper drill?  All my references say the drill is never driven by the tang, and my tail stocks do not have a tang slot.  Supposedly it is for removing the drill with a drift (a wedge shaped piece driven in from the side.)

[rampa room artillery]

well i guess they do, i was using a old dead center to make into a boring bar  and it does not, i guess i need to get some more tooling and play with it.  wait, another trip to richmond va. tool store this weekend with more money this time.

rick bryan

[Cat Whisperer]

You are referring to the tang at the rear of a Morse taper drill?  All my references say the drill is never driven by the tang, and my tail stocks do not have a tang slot.  Supposedly it is for removing the drill with a drift (a wedge shaped piece driven in from the side.)

That sounds good.  BUT IF the taper were to slip, the tang would not turn much.

And in this case, simply cranking the assembly back would pop the bit out (if it had a tang).

[Victor3]

what would you recommend for large hole boring I want to use a 4.5 in spade but i have a number 2 morris taper in the tail stock.
  and all the large spade bit holders are like number 5 MT   ,  will a number 2 MT handle the bit? or is that too much to turn. ?

 rick bryan

You'll have 90% chatter, 10% material removal with a spade drill that large.

[dominick]

A friend of mine who built full scale cannons for many years used to take the drill bit and chuck it in the lathe spindle and had a large fixture for clamping the barrel to the carriage.  He fed the barrel into the bit with the carriage. When he gave me all of his shop inventory, I got the 5 foot long drill bits and the barrel clamping fixture.  The drills were a regular large diameter bit that had a heavy pipe slipped over the straight shank and welded.  The machine shop that recently bored and sleeved the Revolutionary war cannon barrel used a boring machine which turned a 2-7/8" spade bit. They then bored it to 3" on a lathe using a boring bar.

[sseib]

We use Allied Machine & Engineering Corp spade drills at work. I did a quick horsepower requirement for a 4-1/2 inch spade in 1018 steel.
AMEC recommended 130 sfm and .022 ipr assuming thru tool coolant and no peck you need a 30 hp spindle.
I recently drilled a 2/3rd scale Mt. Howitzer 2.75 dia approx 22 inches thru and took almost an hour due to we peck drilled with a full retract.
That was on a CNC horizontal boring mill, I would guess close to one hour per inch to manually peck on a 2hp lathe.

         constant                        (3.82*sfm)/dia   mat constant               
hp =    0.6283 x    ipr x      sfpm      rpm x             Km x           dia sq      hole dia      depth/min    min/10 inch
29.04   0.6283     0.022     130      110.36            0.94            20.25         4.5             2.43          4.12
20.30   0.6283     0.02       100       84.89            0.94            20.25         4.5             1.70          5.89
2.03    0.6283      0.01       20        16.98            0.94            20.25         4.5             0.17          58.90
4.55    0.6283     0.015      80        67.91            0.94            7.5625       2.75            1.02           9.82

In my early days I used up to 8 inch dia spades in a radial arm drill press. Once the drill was drilling full dia I couldn't hand crank the feed, I had to use the power feed to push the drill. You may encounter the same problem with your tailstock, the screw may be too small to generate enough force to get the drill to bite. Depending on your equipment you may have to step drill out to diameter and even use multiple length drills to get the depth. I am sure it is possible with-in the capability of your machine, how long will it take? It may be quicker to drill small and bore big.

Steve Seib

[Cat Whisperer]

Here is a fixture that I made from some existing parts.

The major diameter is 1-3/4 - and there's lots of scrap rounds and drops at work.

I've made a bunch of adapters for drills, boring bars, and spade drills.  All fit into the one fixture.

Here it's shown holding a cutter for making a bullet mould.

One to three setscrews hold the bit, two big bolts in the fixture to retain the adapter.  (The two shims under it center the axis of the tool with the axis of the headstock.