# hard bit when drilling mild steel



## wallace (23 Aug 2013)

I am attempting to make a lantern tool post for my RS lathe. I have some 40mm round bar which I am drilling a row of holes to make the slot for the tool to go in. All has gone well by starting with a small drill and gradually going up in size. I have one hole that will not drill, it has eaten three HSS drill bits. Is it possible to have a piece of steel with a much harder portion buried inside? Any advice would be great
Mark


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## flh801978 (23 Aug 2013)

Depends what the steel is

mild steel should be ok
stainless work hardens like mad
tool steel can work harden easily
what size hole you doing?
can you drill from the other side?
use a cobalt drill?

Ian


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## wizard (23 Aug 2013)

What make of drills are you using
Are you using a pillar drill? 
What speed are you drilling at?


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## CHJ (23 Aug 2013)

In the past, (post war period) it was not unusual to come across so called mild steel full of hard impurities.

This was due to less than perfect inclusion of scrap, including tool bits etc. in the furnace.

Have you by any chance acquired a sample of this low grade stuff?

The alternate is as mentioned is that it is a higher carbon content "mild steel" and you have managed, due to blunting drill perhaps, to locally work harden the metal.

This summary of specifications may be of interest (My PDF)


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## wallace (23 Aug 2013)

I am using my wadkin pillar drill which is a fixed speed of 2000rpm, I could do with a vfd. The bits are HSS of various makes some new some ancient. The steel is from a local fabrication place so I don't think old stuff. By the comments so far I think my problem may be hardening of the steel. I tried to make the holes bigger and when it was not cutting I gave up before I ruined all my bigger drills. I did not know the heat would affect the steel so much I was only going up in 2mm increments, I was using oil as well. I think my speed must be too fast and I've created to much heat? Any ideas how I can progress, I need to get to 16mm and I'm at 11mm and then join all the holes together to make a slot with a file.


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## flh801978 (23 Aug 2013)

Blimey
you need to be perhaps at 200 rpm drilling a 16mm hole with lots of coolant.

Start again with a slow speed ( on a different machine)


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## wallace (23 Aug 2013)

Thanks I thought I was pushing my luck, that's why I was going up gradually. So is the lump of steel I have no use to work with without better quality bits. I think I'll try with a new bit of steel, Whats good as a coolant for drilling


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## CHJ (23 Aug 2013)

wallace":1t6vtb5n said:


> .. So is the lump of steel I have no use to work with without better quality bits. ..



If you have a decent blow torch or a barbecue you could heat the piece of steel to cherry red and cool as slowly as possible (leave in fire) to anneal it.


Trying to work it with drills at that speed and diameter will only result in a similar experience regardless of drill quality.

If starting again, drill a series of small holes around the hole periphery and join them up with needle file/hacksaw blade.


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## wallace (23 Aug 2013)

Thanks Chas, that makes more sense than trying to drill a 16mm hole through 40mm steel (hammer)


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## wizard (23 Aug 2013)

The first thing you need to do is sort out the pillar drill, it’s the most useful tool you will ever have then get some dormer drill bits of eBay and learn how to sharpen them


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## wallace (23 Aug 2013)

That's the type I was using, I'm ok at sharpening freehand as well. Everything was going ok until I got to 9mm mark then it went pear shaped. I think I have a vfd but I'm sure its only upto 1.5hp


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## wizard (23 Aug 2013)

Drilling at the right speed i use a 3/16 then ½ inch or whatever and will cut through in seconds and a drill motor should not be more than 1 ½ hp


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## Graham Orm (23 Aug 2013)

What about annealing the steel? Is there any way you can get it cherry red and let it cool slowly that should re-soften any thing that's become work hardened. Then start again with the right speed and a new drill bit as that too will have been heat damaged.


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## wallace (23 Aug 2013)

I think I'll just get a new chunk of steel, it was only a couple of quid. Wizard the motor on my drill is the usual wadkin beast being 2.5hp and came from the wharfdale speaker manufacturers


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## AES (23 Aug 2013)

@Wallace:

CHJ has, IMO, posted the best "do it today" solution to your current problem BUT ..... although I have no idea about your Wadkin pillar drill, you really do need to sort out some way of slowing it down if it's going to be any good for "general" metal working long term. 2,000 rpm is high for all but the smallest of drills but that's about as fast that you should ever be running, and as soon as you get above, say quarter inch dia (as a max, ideally an eighth) it'll be much more useful in the, say, 600 or 700 down to 100 or lower rpm ranges.

As you've now found out it's the peripheral speed at the "outside point" of the cutting edge of the drill that really counts and as you go up in size this gets to really very high linear speeds indeed (high for HSS drills and mild steel anyway).

Has that Wadkin really not got any pulleys (I know the name of course but have never seen one of their pillar drills)? How is the drive taken to the quill? Is an electronic controller a possibility?

These comments are intended to help, not criticise.

Krgds
AES


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## wallace (23 Aug 2013)

This is my little drill, as you can see the quill goes on the end of the motor shaft. Its a lovely drill with a geared table rise and fall and the drill is controlled by a handle or by a foot lever. When I find a vfd it will make this a lot more usefull.


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## flh801978 (23 Aug 2013)

What's the speed on it?
It should be 1440 or 2800 ?

If you put a vfd there will be no usefull power at the slow speeds you need for larger holes in steels


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## wizard (24 Aug 2013)

That’s not a drill, it’s a very nice router


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## wizard (24 Aug 2013)

Before anyone says otherwise it’s an overhead router, and I am green with envy. There is no way that will be any use as a drill. There are three things you can do with that. 1 use it as a router 2 sell it on eBay 3 give it to me

https://www.google.co.uk/search?q=w...yMaLB0QWbrIHwDw&ved=0CC0QsAQ&biw=1327&bih=579


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## Inspector (24 Aug 2013)

Rather than burn though a bunch of drill bits there must be someplace in England that you could buy a tool post like this one either new or used and come out ahead.
http://www.grizzly.com/products/Rocker- ... the/SB1345
Pete


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## CHJ (24 Aug 2013)

wallace":1f86im8d said:


> ..... When I find a vfd it will make this a lot more usefull.


I assume it is 3Phase then, a VFD will be of little use if it is single phase.


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## wallace (24 Aug 2013)

Hi the speed is 2800rpm, and 3 phase wadkin did make some of these with different speeds to order. Wizard this is not an overhead router it is a drill or the correct name is a borer. I cant find the link to the original catalogue. But I don't see why it couldn't be used as a router especially if it ran through a vfd so the speed could be cranked up beyond the 2800. Pete I was wanting to make one as similar to the original one as possible. This machine is one I restored a few years ago heres a link to the thread if your interested.
wadkin-pillar-drill-resto-t56790.html?hilit=wadkin pillar drill&start=45

Chas just by shear lack of knowledge I thought you could put a vfd on a single phase motor. I wanted to change the speed on the feed of an old planer thicknesser and guess what it worked. Mr nine fingers was alittle bemused by my re writing the laws of physics or the laws of stupidity. :shock:


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## flh801978 (24 Aug 2013)

Just out of interest how did you connect a vfd to a single phase motor?
the 3 output wires how did you connect these?

and is it still running?


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## wizard (24 Aug 2013)

you are right it as a borer and there is no way you will drill metal with that.
this is a drill


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## wallace (24 Aug 2013)

Wizard, now that is a big boys drill what make is it. I likes it. I think the LM borer maybe designed for non ferrous metals?
Heres how I connected the vfd


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## wizard (24 Aug 2013)

its a Meddings A10 articulated head pillar drill


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## CHJ (24 Aug 2013)

Although I can't see the actual connections well enough to draw out the circuit diagram of what you have done, I suspect you achieved a form of 3ph drive by utilising the start winding as a pseudo third phase.

I would not expect this to give you maximum torque but many lower budget 1 ph motors use a permanent start/run phase shifted winding connection to provide additional torque.

Only concern I would have for anyone trying this would be the ability of the motor windings to carry the full blown current supplied by the VFD on the start winding. Maybe something old school motors may be able to absorb better than a pared to the bone hot running far eastern produced item.


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## wallace (24 Aug 2013)

I think the motor is one those cheapy Clarke ones 1.5hp I did try a very nice little 0.5 hp old motor but it never had the balls to use on the feed. I also had a 6hp old beast but I thought that was a bit much. It works pretty well, I have just been thicknessing some 16" jointed oak boards.
Mark


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## graduate_owner (24 Aug 2013)

Hi Wallace, 
You could save yourself a lot of work in drilling and filing if you could find someone locally with a milling machine. It's no good asking me because I'm hundreds of miles from Durham but it's the sort of job my milling machine would do easily and neatly. Why don't you ask around in this forum - there is after all a metalwork section?

K


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## wallace (24 Aug 2013)

I think half the fun is trying to do stuff yourself  . So I've tried and failed  . So does anyone fancy making me a tool holder if I provide all the measurements. How about you K? I don't mind paying for postage and any expenses incurred.


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## graduate_owner (25 Aug 2013)

PM sent

K


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## woodfarmer (17 Sep 2013)

wallace":1ongrf82 said:


> Thanks I thought I was pushing my luck, that's why I was going up gradually. So is the lump of steel I have no use to work with without better quality bits. I think I'll try with a new bit of steel, Whats good as a coolant for drilling



Going up gradually is not good practice. there is not enough mass in the swarf to cool the drill. plus it can attempt to screw into the hole. ie the drill tries to behave like a self tapping screw.

If you can, heat the steel in a bbq, and when nice and hot embed it in the coals then cover the lot with enough dry sand to starve it of air. Wait 2-3 days for it to cool. by then it may well have annealed. 

You really need MUCH slower drill speed.

SORRY CFJ, DID NOT SEE YOUR POST BEFORE I HAD POSTED.


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