# Drilling A Hole Vs. Milling A Hole - Bit In Lathe Tailstock



## BillWood (Oct 9, 2015)

After reading a few posts on the internet I used an endmill to create a 12mm hole in a 15mm diameter piece of steel.

Two flute milling cutter in jacobs chuck in tailstock of lathe.

No Problem - easily and quickly done.

And yet if I had gone the drilling route  ie pilot hole then increasing hole size  with incrementally bigger drill bits in jacobs chuck in tailstock it would have taken several passes increasing the drill size each time, and I can tell that my little lathe (SB 9"  clone - Aussie Hercus doesnt like the larger diameters and sometimes the MT2 taper will start to turn in the tailstock.

Why is it so easy with the Mill Bit and such a hassle with the drill bits ?  I get the impression there is more to it than maybe the mill bit is sharper than the drill bits. 

Reading between the lines of old books and magazines it not uncommon for the MT2 taper to spin in the tailstock when drilling - people discuss different ways of preventing this, with various "handles" sticking out to stop against the ways.

Oddly enough this lathe has no problems drilling small diameter holes yet theoretically it is well underspeed for small drill bits with a top speed of 720 rpm - If I use 100sfm for mild steel cutting speed then my criticial diameter is 0.53"


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## T Bredehoft (Oct 9, 2015)

Out of curiosity, how close to 12 mm was your hole?  And wasn't your Jacobs chuck on a MT2 driver? But it didn't slip?  I have to ask, how hard were you pushing the end mill as compared to a 12 mm drill?


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## Ulma Doctor (Oct 9, 2015)

I have a beautiful little 1976 Hercus ARH 9" lathe, the drill chuck will spin if you are too aggressive with a drill bit.
great, well made machines!!

for the same size tool, a drill bit will have more cutting edge exposed to the work  due to it's cutting edge angle- whereas the 2 flute endmill would have a relatively flat cutting angle and less cutting edge contact
and endmills are usually a lot shorter too, less flex


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## BillWood (Oct 9, 2015)

The 12mm hole was for a rough as guts collett which has how done its job and the original hole size is now impossible to determine - but I will do it again tonight in a fresh piece of scrap and report back.

I was fairly surprised that I didnt have to push the mill bit very hard at all compared to the drill bits, and yes it was on the same MT2 taper tailstock mounted Jacobs Chuck that I use with the drills.

I am too much of a newbie to know whether or not my drill bits are sharp enough and I need to learm nore about how to assess this and how to sharpen them, am currently reading about this. Maybe a good test for me at the moment is  "If a milling cutter is easier than a drill bit then you need to sharpen the drill bit"

I was fairly surprised that I didnt have to push the mill bit very hard at all compared to the drill bits.

But I only seem to have problems with drill bits at diameters around and above 0.5" - smaller than that no problems whatsoever, and I do see these references in the older magazines and books to using drive dogs etc on the tailstock to stop MT2 drill bits spinning in the tailstock so it does seem to have happened to other folk.


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## JimDawson (Oct 9, 2015)

Consider that the endmill has a different cutting geometry than a drill bit.  It doesn't require as much pressure to remove material.  But, a drill bit of the same size can remove material at a much higher rate than an end mill is capable of.


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## Bob Korves (Oct 10, 2015)

It is worth drilling a small hole even when using a center cutting end mill.  The cutting speed at the center of the hole is zero, and the end mill does not have a chisel edge to open up the hole like the drill does.  End mills can plunge like you did there, but they don't like it.  They can also spin in the drill chuck.  Using a dog on larger drills to prevent rotation will stop the spinning in the Morse taper.  It is also a good idea to check the drill tapers and tail stock socket for damage and the fit of the drill in the taper to see how good the fit is.  A hardened Morse taper tool or bushing of good quality and in new condition can check the tapers using Permatex High Spot Blue for marking and scrapers for removing burs and high spots.  It is a bit tedious and can take some time, but those tapers can be tested and repaired for solid seating and for concentricity with the quill.  A Morse taper reamer can also be a good tool to use judiciously.


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## Wreck™Wreck (Oct 10, 2015)

BillWood said:


> Why is it so easy with the Mill Bit and such a hassle with the drill bits ?  I get the impression there is more to it than maybe the mill bit is sharper than the drill bits.
> "


Part of the answer lies in your question, if you can plunge an end mill to size in one shot why do you not do the same with a twist drill?  Unless the part requires a flat bottomed bore which a twist drill can not do. There is no reason to drill a pilot hole then increase drill sizes in steps, spot drill then push the full diameter drill bit in in one operation, pecking for chip control of course. Step drilling is an excellent way to pull the chuck or drill out of the taper.


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## BillWood (Oct 10, 2015)

Wreck™Wreck said:


> Part of the answer lies in your question, if you can plunge an end mill to size in one shot why do you not do the same with a twist drill?  Unless the part requires a flat bottomed bore which a twist drill can not do. There is no reason to drill a pilot hole then increase drill sizes in steps, spot drill then push the full diameter drill bit in in one operation, pecking for chip control of course. Step drilling is an excellent way to pull the chuck or drill out of the taper.



Ive been doing the incremental increase because I'd read about that method before I read about the straight plunge with the mill bit.

What do other SB9 or any other owners of small lathes do ?


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## John Hasler (Oct 10, 2015)

I usually spot drill, drill full depth with a small diameter drill, and then go directly to full diameter.  I find this faster than going directly to full diameter, perhaps because most of my bits are dull.


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## Bill Gruby (Oct 10, 2015)

I use primarily MT2 Tapered shank drills in holes over .500 in the lathe. I stay away from drills wit  altered ( turned down) shanks for rigidity reasons. They tend to chatter loudly in the lighter lathes.

 "Billy G"


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## Charles Spencer (Oct 10, 2015)

Bob Korves said:


> Using a dog on larger drills to prevent rotation will stop the spinning in the Morse taper.  It is also a good idea to check the drill tapers and tail stock socket for damage and the fit of the drill in the taper to see how good the fit is.  A hardened Morse taper tool or bushing of good quality and in new condition can check the tapers using Permatex High Spot Blue for marking and scrapers for removing burs and high spots.  It is a bit tedious and can take some time, but those tapers can be tested and repaired for solid seating and for concentricity with the quill.  A Morse taper reamer can also be a good tool to use judiciously.



I have an SB 9C and a 9A.   I often use a dog when drilling with a large diameter bit on the lathe.

My SB 9A was having some trouble holding on to a drill chuck.  I had an MT2 reamer and that seemed to fix a lot of the problem.


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## Wreck™Wreck (Oct 10, 2015)

BillWood said:


> Ive been doing the incremental increase because I'd read about that method before I read about the straight plunge with the mill bit.
> 
> What do other SB9 or any other owners of small lathes do ?



I have never used a Southbend small lathe but I suspect that it has the power to drive a 12MM drill through many different materials in back gear, try it you may be surprised at the outcome. Keep the feed up and a steady uniform chip forming at all times if possible, this is what twist drills are designed for. Do not expect an accurate diameter, ream or bore after drilling, drills are roughing tools.


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## 4GSR (Oct 10, 2015)

BillWood said:


> ...........What do other SB9 or any other owners of small lathes do ?



The time or two I've done it in my 9" SBL, I do it just like you have done.  I've pushed much larger endmills into a hole to create a flat bottom hole for what ever the reason was.
I will say, the endmill tends to "grab" and when it does, it will pop the 2 MT from the tailstock.  A driving dog won't even help you here.  As others have said, keep a smooth  even feed, not too fast, not too slow, and use lots of your favorite cutting oil in the drilling operation.


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