Thread: Drilling holes in steel ... small then big?

Originally Posted by TassieKiwi

Sheesh. The bloke's just drilling a wee hole guys. Tie the ladder off at the top, have someone hold the base if you need to. Drill as close to the center of the ladder as you can - Take it nice and easy - if the drill bites, drop the bas1ard.

Den

Drop it onto the poor bugger holding the ladder

One thing I have found invaluable with drilling steel is firstly start with a sharp drill bit and use the moly cutting lubricant stuff (what ever it is called properly) fantastic for keeping the bit sharp and quick ease of cutting. Also don't set the drill speed too high - it will just heat up the bit, take out the temper and make it blunt. The Moly stuff helps heaps I have found.

Cheers

I use Rocol RTD as a lubricant on drill bits. It makes a huge difference in the performance and the life of the cutting edge. Worth having a look at it.

Originally Posted by 2Shane

However one can drill a small hole, say perhaps at 5 or 6mm and then one can oversize the hole with a 8mm drill.

Your pilot hole should never be more than half the size of the inended drill size and is normally about 1/4 the size. Drilling a 5 mm pilot for an 8 mm drill when working up a ladder... You might as well just climb to the top of the ladder and jump off.

Dan

BTW if you look at the centre of a drill bit tip, you will see a small flat bit in the centre of the tip, where the two cutting angles meet. Your pilot should be a clearance for that part.

Dan

Originally Posted by TEEJAY

One thing I have found invaluable with drilling steel is firstly start with a sharp drill bit and use the moly cutting lubricant stuff (what ever it is called properly) fantastic for keeping the bit sharp and quick ease of cutting. Also don't set the drill speed too high - it will just heat up the bit, take out the temper and make it blunt. The Moly stuff helps heaps I have found.

Cheers

We use to use stuff called " treferlex" I think is the spelling a green compound with a most distinctive odour a must for tapping steel espically with small taps but also for good for turning and drilling

[QUOTE=Barry_White;256388]Stinky

I find the best way to drill larger holes in thin metal is to first punch them with a pressure centre punch as shown in the first pic. I find these ideal <SNIP> because you only need one hand to centre punch.
<SNIP>

Barry.
I have what looks like the same type of Centre Punch. It is identified as: Eclipse No. 171. The problem is that while it still operates and the end cap is adjusting the spring tension I can no longer get the punch to do light marks. It is obviously softer than the full setting but not like it used to be when I can remember being able to make light 'witness' punches with one hand.
Do you know how it operates and what may be wrong and need repairing? Having taken it apart several times I am thinking that the top pin (connected to the adjusting cap) may be worn short and so it needs further spring compression to 'trigger' the punch.
If you or anyone else can supply any information I would be very grateful.

TIA Cheers, Peter.
***************

Trefolex is for use with hand tools such as taps and dies ,not meant for power driven tools .
I don't know if it the same formula as it was years ago , but a warning was issued many years ago about using this lube on powered tools .The smoke that is generated from the heat is proven as carcinogenic.
We were stopped form using it in the toolroom where I worked for this reason.

Kev.

Ok, If I may squash everybodys toes, here's my answer to the original question. You're up on a ladder, right? Use what you can to center punch the position of the holes, be it an automatic C/punch or a two handed job. marking the holes is the easy part. You have to hang on with one hand and use the other for drilling. You need a pilot hole of no bigger than 4mm and no smaller than 3mm. Forget what was said about what sizes to use being a percentage of the diameter and do what I would do. The 3 or 4mm drill is easy to put pressure on it with one hand and drilling the pilot hole will be easy. As someone described earlier, the pilot hole is to take away the force (pressure) required to make the 8mm drill penetrate. Run the drill at maximum speed for the 3mm or 4mm hole. Any slower and you are bound to break the drill. The cutting speed for HSS drilling mild steel is 100 feet per minute (about 30 meters per minute). You do the maths for the correct RPM.
Grind the 8mm drill with the minimum amount of lip clearance. If it wont cut, increase the clearance gently untill it cuts cleanly without grabbing. With the correct lip clearance, the drill will be very easy to use with one hand. The speed for running the drill with the 8mm HSS drill is 1100 to 1200 RPM. The RPM for the 3mm drill is 3000 and for the 4mm drill is 2400. You can drop these RPM's to (8mm drill)1000, 4mm drill, 2000 rpm but no slower. Use a good lubricant and go for it. You will not burn the HSS drills at these RPM's and if you use a good quality HSS with Cobalt the drill will last for all the holes. Do not force the 8mm drill thru the steel. Let it cut at its own rate.
If the 8mm drill is shaped carefully with the correct clearance angles, it should not grab and be out of control when the drill breaks thru the 3mm steel. However, be very careful and dont hurt yourself.

Kody

Hi Kody

This thread is over three years old and I gather by now Stinky has drilled his holes and moved on. He never said how he got on anyway.

I gather from a lot of the replies to this thread that most have never seen a step drill let alone used one because to drill a large hole in thin metal with a normal drill will usually produce a hole the shape of a triangle with curved sides even by drilling a small pilot hole first.

I have been using step drills for forty years and had to get them specially made by a engineer long before you could buy them off the shelf.

Peter

My punch still works fine so I couldn't really say what is wrong with yours. They are really cheap enough to buy a new one.

Originally Posted by Ashore

We use to use stuff called " treferlex" I think is the spelling a green compound with a most distinctive odour a must for tapping steel espically with small taps but also for good for turning and drilling

Woodlee is correct, the Trefolex paste (as opposed to the liquid) that you refer to is not meant for use in drilling. If you look at the label on the container it goes to great pains to warn against using with power tools or in a situation where its use would generate fumes (ie drilling, turning etc). It is only meant for use with hand tools.

But surprisingly enough given the above I have seen it used in TAFE workshops with no safety warnings whatsoever - go figure!

Good news .... I finishes the holes last weekend

Nahh just kidding. Can't remember what I did but most likely used a centre punch and then just the 8mm drill. It was to mount some eye bolts for the shade sail and was drilling through recycled fire sprinkler pipes.

Sorry that I didn't previously post a thank you and follow up .... quite unlike me I like to think!