# Drilling 1inch hole in 1.5 inch thick A36



## Submachine (Feb 13, 2019)

I am drilling a hole in A36.  It has been difficult with multiple sharpenings per hole.  I don’t mean the final hole, I mean per step I need to sharpen 2-4 times.  I am using a Silver and Demming set of bits.  Using lathe is not an option due to the length of the piece.

Details
Final diameter 1inch
A36 alloy 1.5 inches thick
Using small manual mill
Turning at minimum speed which is 315 RPM

Two questions 
What is the proper way to drill, how many bits to use to finally get to 1 inch?
What is an easy way to get a pilot hole drilled all the way through?


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## COMachinist (Feb 13, 2019)

Wow that is kind of a crap shoot in A36 which is a mystery mix. It can go from soft easy drilling to Hss bit eating monster in a 1/8” of cutting. I use coblt drills when working with A36. Start at 1/4” and increase by 1/8” if you have them, 1/4” max and use a lot of lube and peck drill don’t just plung through, with lite to medium pressure. Let the drills do the work. You don’t say what size the mill is, or if you have a drill press. Which ever one has the most power is what I would use.
Good luck
CH.


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## Submachine (Feb 13, 2019)

The mill head is a Smithy, but it has been converted to mill only with 10x10 yuasa xy table.  I think it is 3/4 horse.  

I am taking smaller steps and it is working better(1/32 steps in many cases).  I need a keyless chuck.


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## cathead (Feb 13, 2019)

315 rpm is too fast to drill a one inch hole in most any steel.  Do you know anyone with a mill that will turn at a slower speed?
Usually I drill  a 1/4 to 3/8 inch hole all the way through and then drill with the one inch bit and use lots of cutting oil at 60 or so RPM.
I would use a keyed chuck myself as they usually have stronger gripping power than a keyless chuck.

edit: and I would use a cobalt bit if I had one...


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## mmcmdl (Feb 13, 2019)

What is your maximum collet size ? Carbide insert drill could handle the 315 rpm .


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## benmychree (Feb 13, 2019)

Yes, what cathead said; when possible it is good practice to drill a pilot hole that is the thickness of the web of the final drill.  In production, a RPM of over 300 would not be too fast in soft steel; using 80 ft./ min. as a starting point, according to my machine shop teacher, you take the cutting speed and multiply it by four and divide the result by the diameter of the moving part ( this is not exact, but a person can do it in their head), the result in this case would be 320 RPM.  I wonder if you are using cheap import drills?


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## Cactus Farmer (Feb 13, 2019)

Does the mill head have a back-gear function? 315 is was too fast!!! Figure the surface feet at the edge of the bit. It's cooking ,ie getting very hot! I have a very old flat belt machine with #4 Morse Taper. This beast has a back gear and auto down feed. I drilled a hole 2 1/4" thru 1" A36. Very slow but a pretty hole. Not reamed quality but better than you would have thought. I watched it and applied cutting oil as needed. 1/4" pilot and then full size.


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## hanermo2 (Feb 13, 2019)

Suggest relief holes like for hole cutters.
About 1/4", 2-3 spread around the perimiter.
They make a huge difference.


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## mmcmdl (Feb 13, 2019)

Most hardware stores sell carbide tipped drills also . Not very expensive when compared to multiple sharpenings . And then you can re-use it too .


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## benmychree (Feb 13, 2019)

If a person in the shop where I apprenticed drilled at such a snail's pace as has been suggested, he would have had a very pointed conversation with the foreman, along the lines of "speed that up!"  60 rpm is only about 15 feet per minute cutting speed, that would be slow even for carbon steel tools.  As I previously said, about 80 FPM is a starting point for HSS tools on mild steel.


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## pstemari (Feb 13, 2019)

Sounds like the OP is hitting a lot of inclusions, etc, in the material. An inserted spade bit or a carbide toothed hole saw might be better.

Sent from my Pixel XL using Tapatalk


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## westerner (Feb 13, 2019)

cathead said:


> Usually I drill a 1/4 to 3/8 inch hole all the way through and then drill with the one inch bit and use lots of cutting oil at 60 or so RPM.


That is the technique I was taught. Pilot hole slightly larger than the web of the drill for finish size. Pilot hole, finish drill, no steps in between. The finish drill employs the majority of its cutting lip to get the job done. Going in small steps focuses the cutting forces on only the far outer edge of the cutting lip, and dulls it quickly.


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## P. Waller (Feb 13, 2019)

Feed rate.
Not enough of it., use a minimum of .006" per revolution feed rate, such a hole would take less then 3 minutes each to drill in that material.
300 Rpms @ .006" per revolution = 1.8" per minute X 1.5 through = 2.7 minutes, this does not include starting at the chisel point and passing entirely through, a conservative 4 minute cycle is about right.
If you have the power do not drill a smaller pilot hole, just spot it and drill straight through in one shot to size.
Use flood coolant or flood cutting oil.

There is no reason that a 1" twist drill will not produce 50 such holes between sharpening or replacement.

I have posted this in the past.
How to drill.
1 5/16" hole through 3" of A36/1018 hot rolled steel rounds.

Place parts in chuck if a lathe or vice if using a mill
Place drill in spindle or turret, a plain old HSS twist drill is used here
Turn spindle on, engage feed and let it eat, no spotting required here as the finished bore is 1.75"
.008" feed per revolution at around 80 FPM cut speed or 250 Rpms
32 parts drilled at about 3 minutes each using one used bit.


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## COMachinist (Feb 13, 2019)

Jesus I can tell all you old crotchety experts have never done any thing with a smithy any thing. Well I have used to and old 1220 XL smithy for years before I got my current, the op is not an apprentice of any thing he has what he has, no carbide indexable drills or end mills. Just a deasent drill set. The smithy realy was not really a versitile machine. It was an entery level, and not much better than a drill press. Just go slow and use small steps. If you want a set aaof MT 3 collects I have a set I used on my Smithy. Hardly used some not used at all. The smithy will do it just not at production speed.
CH


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## mmcmdl (Feb 13, 2019)

No , we all don't have 50 hp at the spindle , but what we try to give is advise . Good advise . We do understand that time is not of the issue in most instances to many of the questions , but the correct tooling is well worth the expense . You could drill that with a 18 volt hand drill and 1" bit faster than the progress being made here . Just saying , his rpms are too high .

Too many people are injured trying to do things half ashed . I see it at work everyday . I f you can't afford a 10 dollar drill to do it safely , I understand . And no , we all didn't start out as fully tooled machine shops . We learned the hard way and not on a computer . 

Best advise I've ever gotten and passed on . " Work smart , not hard " .


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## Submachine (Feb 14, 2019)

Cactus Farmer said:


> Does the mill head have a back-gear function? 315 is was too fast!!! Figure the surface feet at the edge of the bit. It's cooking ,ie getting very hot! I have a very old flat belt machine with #4 Morse Taper. This beast has a back gear and auto down feed. I drilled a hole 2 1/4" thru 1" A36. Very slow but a pretty hole. Not reamed quality but better than you would have thought. I watched it and applied cutting oil as needed. 1/4" pilot and then full size.


No backgear.  Yeah it is smoking.  I might try the drill press.  It’s at 200RPM.


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## Submachine (Feb 14, 2019)

COMachinist said:


> Jesus I can tell all you old crotchety experts have never done any thing with a smithy any thing. Well I have used to and old 1220 XL smithy for years before I got my current, the op is not an apprentice of any thing he has what he has, no carbide indexable drills or end mills. Just a deasent drill set. The smithy realy was not really a versitile machine. It was an entery level, and not much better than a drill press. Just go slow and use small steps. If you want a set aaof MT 3 collects I have a set I used on my Smithy. Hardly used some not used at all. The smithy will do it just not at production speed.
> CH



I hate the Smithy.  I really don’t use it for much.  I made the mill slightly better by putting the xy table on it at the expense of the lathe. I have another lathe.  Send me a note on the collets letting me know what you want for them.  Thanks


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## cathead (Feb 14, 2019)

As a hobby machinist, I do not have to run at production speeds.  Manual feeding is the best choice on my mill for a part
that I can't turn in the lathe with feed .   As long as I am making curls, I am advancing in the hole.  I'm gonna watch the process
carefully and if she quits drilling, I will stop and put a new edge on the bit, maybe even take a coffee break, refill the oil can.......


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## john.k (Feb 14, 2019)

Drilling at 006 feed is just eating up bits.,drilling an extra 1/8 at a time is wearing off the margin,and eating up bits...........for harder steels ,reduce the speed ,never the feed.......my Richmond radial drill isnt a powerhouse ,but will easily drill 1" holes thru wearplate.with ordinary HSS drills....and plenty of suds.......you got to keep the heat down,if the chip blues with suds,slow down a bit


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## Submachine (Feb 14, 2019)

john.k said:


> Drilling at 006 feed is just eating up bits.,drilling an extra 1/8 at a time is wearing off the margin,and eating up bits...........for harder steels ,reduce the speed ,never the feed.......my Richmond radial drill isnt a powerhouse ,but will easily drill 1" holes thru wearplate.with ordinary HSS drills....and plenty of suds.......you got to keep the heat down,if the chip blues with suds,slow down a bit


I am seeing a lot of smoke/vapor..using a ton of tapomatic.  I reduce speed but it is hard to keep the smoke away (manual feed).  Is the smoke/vapor ok?


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## macardoso (Feb 14, 2019)

Saw a recommendation for using an annular cutter for large holes in steel.


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## mksj (Feb 14, 2019)

I would use a 1" diameter 2" long annular cutter, they work quite well and you can drill the hole in one pass. You need to run them at low speed (typically around 150-200 RPM for this diameter, but varies by material), use cutting oil, use continuous pressure when feeding, do not peck at the material. You want nice even strings of chips. I use a modified 3/4" end mill holder to hold the annular cutters, I drilled/ tapped two 90 degree holes for the cutter securing screws.  The end mill holders are hardened, so my drill bit wasn't too happy.


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## P. Waller (Feb 14, 2019)

mmcmdl said:


> No , we all don't have 50 hp at the spindle , but what we try to give is advise .


I gave excellent advice, If the machine or process that one is using can not support sufficient feeds you will simply be rubbing the tool on the work.

This always ends in tears.

Slow down the spindle speed to the point that the tool will cut with the feed that you are able to apply, this may take a good deal of time however.

Patience is a virtue, stopping the operation many times to either change or sharpen tools is slow at best.

Good Luck


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## Submachine (Mar 4, 2019)

Final result for those still watching.

I couldn’t get enough power for 1 inch...got up to about 7/8th.  Took to local machine shop and he knocked out for me no charge.  The rest I could get on my lathe and they drilled easy enough.


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## mattthemuppet2 (Mar 4, 2019)

developing an ear/ eye for these things is a good idea. You're after a nice spiral chip. If you get alot of shuddering and small flakey chips, slow down the spindle speed and/ or increase the feed (probably both to begin with). If you can't slow down the spindle, increase the drilling pressure. If you still can't get a nice spiral chip, you're SOL on that machine. One thing I would caution about, and this is from someone with light duty machines, is step drilling in too small steps - 1/8" step at a time is the minimum I would use or you'll be busting the tips of the corners of the drill and maybe getting the drill chattering as it doesn't have enough material to "bite" into. Holesawing is an option, but I doubt you'd be able to go slowly enough if your minimum is 300rpm. Likewise with annular cutters, which are even less tolerant of flexy machines in my experience. I drilled a 1" hole 2 1/2" deep into some stainless (400 series?) over Christmas and that took a looong time on my 6x26 mill, step drilling up from 1/2" to 1", though I can't remember the steps I used. Lots of cutting oil, 60-100rpm speed, need to touch up one of the S&D drills.

I do find it funny reading the advise of those with industrial machines. Drilling a 1 5/16" hole in one go on a Warner Swasey turret lathe  (4-5000lb? 10hp+?) is VERY different to drilling a 1" hole on a light home shop machine. I'd love to drill a 1 5/16" hole in steel on my Atlas 618 in one go, but it just ain't gonna happen.


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