Speeds and feeds for Carbon Steel Drills

Fromps · Feb 2, 2019

Hello everyone,
I just found a store that has truckloads of old, but brand new, Taper Shank Carbon Steel Drills from the late 19th and early 20th century. I’m just a hobbyists, so I didn’t want to spend $80 per MT-3 HSS drill so I bought a handful of old Navy MT-3 carbon steel drills for $15 total. My question is - what speeds and feeds should I use on my lathe for a 1” drill? What formula should I use for other sizes? My machinist handbook only speaks on HSS and Carbide.

Any assistance would be greatly appreciated.

Thanks,
Iz

PeteM · Feb 2, 2019

Recollection (?) is that you run plain carbon steel tools around 30 fpm (in mild steel). That's the speed at the periphery of your tool, so you figure the circumference in fractions of a foot (about 1/4 foot for a 1" drill), and multiple by RPMs until you're around 30 -- so up to 120 rpm should be OK. Sounds like you'll be feeding these by hand, so you can judge that by feel . . .

Depending upon your lathe, and maybe regardless, you'll want a pilot hole a bit less than the drill web diameter.

A high carbon steel tool can cut just fine -- but it doesn't want to get hot. That applies to re-sharpening as well.

Fromps · Feb 2, 2019

Do you remember where you read that? I’m hoping to nail down a formula.

Thank you for your response.

PeteM · Feb 2, 2019

Fromps said:
Do you remember where you read that? I’m hoping to nail down a formula.

Thank you for your response.

Sorry, can't even remember where I put my keys some days. Perhaps others will chime in. You might check some old edition of Machinery's Handbook -- my decades old recollection is that carbon steel tools ran around 30 SFPM and HSS around 100 SFPM in plain steel and I pretty much didn't look back after that.

There won't be a formula for recommended SFPM -- that was judged by experience. Well, some modern metallurgist might have a model that predicts some combination of surface feet per minute, for optimal tool life at reasonable production rates, with the bond strength of various materials and tools -- but you surely wouldn't like running the math.

Once you get the SFPM recommendation (and it could and should vary for different carbon steels and high speed steels; in different materials), THEN the calculation is easy. You have it, above (peripheral speed of drill, mill, etc. = recommended SFPM). Feed rate is on each cutting edge -- but for drilling from the tailstock you'll likely be doing that by feel.

swarfless · Feb 2, 2019

According to Brittens Watch & Clockmaker's Handbook, use half the speed recommended for the same size HSS drill .. that agrees with what I was taught as an apprentice. I'm not THAT old, we were told that to show us how lucky we were not to be using carbon steel tools ..

Fromps · Feb 2, 2019

Awesome - thank you for the info, guys. I appreciate the quick responses. I’ll give it a go tomorrow and see how it works out.

Andy FitzGibbon · Feb 2, 2019

My 1913 Dreses radial drill has a factory drill speed chart, which notes to "double speeds for high speed steel drills".

Andy

Fromps · Feb 2, 2019

That makes sense. Does it say anything about feed rates or should I halve that too?

Limy Sami · Feb 2, 2019

Fromps said:
That makes sense. Does it say anything about feed rates or should I halve that too?

Nope, feed rate stays the same, ………...FWIW I was taught 1/3rd to 1/2 speed for HSS, and if in any doubt, go slower.

DMF_TomB · Feb 2, 2019

1/2 sfpm for carbon steel tools, feed depends on tool. generally many hss drills are 75 sfpm and feed ends up in the 2 to 4 ipm range. sure you can push faster if you want to risk sudden tool failure
.
so 1/2 rpm and 1/2 feed you would be 1.0 to 2 ipm feed for steel and cast iron with jobber length drills. longer drills generally got to watch too much feed as they bend and break. got to watch resharpening you turn carbon steel drill blue its becomes soft as you heated too much from grinding

John Garner · Feb 2, 2019

Fromps --

Fifty years ago, I learned a fifty-year-old rule of thumb for cutting "mild steel" with high-carbon-steel tools: 25 Surface Feet Per Minute (SFPM) maximum for external cuts, 20 SFPM maximum for internal cuts, and reduce those speeds by 5 SFPM when cutting dry.

Those speeds were about one quarter of what was recommended for high-speed cutting tools, and from the "war stories" that came with the teaching, I think maximizing tool life was the top priority.

John

DMF_TomB · Feb 2, 2019

i have often used 1/2 sfpm for carbon steel compared to hss but got to watch it machining dry. when tool getting dull it gets more hotter and it can more suddenly turn drill blue where hardness is lost from overheating and then drill can suddenly fail. moderately deep holes generally best to peck or pull drill out of hole periodically to get coolant on it and wash chips out of the flutes. extra extra long drills can have tip whipping around so much at high rpm they can miss a spot drill or center punch mark
.
sure you can go slower. usually sfpm are maximum recommendations. extra long drills are often run slower rpm cause they can vibrate and chatter to the point they break. obviously if noisy and you slow things down and its less noisy use your own judgement.
.
when long drill bends drilling and then bend starts whipping around you generally got a second or 2 and drill will break.

Fromps · Feb 2, 2019

This is all great info- thank you!

Iz

johnoder · Feb 2, 2019

What got done when nothing but high carbon was available like in 1899 when this 85 ton assembly was machined bit by bit at Brooks Locomotive in New Jersey

Robert Lang · Feb 2, 2019

From a 1912 Morse Twist Drill catalog.

The Morse Twist Drill and Machine Co ... [Catalogue] - Full View | HathiTrust Digital Library | HathiTrust Digital Library

Rob

Fromps · Feb 2, 2019

Oh man- that is awesome. This place has truckloads of everything discussed in that catalog. Thank you! I’m trying to download that catalog now. That was exactly what I was looking for.

Again, thank you!

john.k · Feb 2, 2019

The trickiest part of using carbon steel is sharpening.......you are supposed to use a large "sandstone" turning at low revs in a bath of water to keep the stone wet,as well as water flow over the grinding..........otherwise the fine edge will heat and draw the temper....there is no way you can use a common dry grinding machine.......but even turn of century tool steel had high tungsten content to make it more tolerant to heat.......high speed steel was used for some years before the "high speed "properties were discovered.......Robert Mushett and double mushett tool steel.

sandiapaul · Feb 3, 2019

johnoder said:
What got done when nothing but high carbon was available like in 1899 when this 85 ton assembly was machined bit by bit at Brooks Locomotive in New Jersey

Indeed John and what a fine locomotive she is!

excello · Feb 3, 2019

Second the opinion - that is a dandy old locomotive. Those drivers are huge !

Excello

johnoder · Feb 3, 2019

excello said:
Second the opinion - that is a dandy old locomotive. Those drivers are huge !

Excello

You may ave noticed the OLD BULL that had to get in the photo - nowhere near as tall as the 80" drivers

Speeds and feeds for Carbon Steel Drills

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