Please, Jim, can you fix so that I can drill...

[Warthog]

I am building stuff for my Ural outift. So far I have angle-ground and filed and then had things welded. So far so good.

Recently I have fashioned a bracket for my folding trenching tool. It will be welded on Monday. However, I am also drilling it full of holes for mounting to the bike and for hinges etc...

The material is regular 5mm x 30mm steel flat bar, not hardened in any way. However, my drill bits keep going yellow then blue then not drilling anymore, only making a very annoying squeal!

What's the knack? Never had problems before, but then never drilled 5mm thick before...

Drill speed is correct, but should I only drill for a few seconds then let it cool? Its starting to cost me if its one bit per hole...

[Lutin]

Some lubrication on the drill bit will work wonders. You can get proper cutting fluid, but just try any old stuff you can lay your hands on. Some old, or even new, engine or gearbox oil maybe??

And, if you're into that sort of thing, it makes a nice smell when the drill bit heats up. Well, I think so. Wouldn't go inhaling huge lungfuls of it though as it's probably bad for you.

Give it a go and see what you think.

[Warthog]

Hmm, interesting. However, does this mean my yellowy-blue bits are still unuseable? Or could this reverse the situation and leave me with 32, 5.5mm drill bits to work with...?

[Lutin]

I would think that the bits may be beyond use, but there's no harm trying them. If they have got that colour then they have got VERY hot, but I don't need to tell you that do I?

GIve your existing bits a go, and if no joy try a new one.

Another thought just occurred to me - are you drilling the holes 5.5mm straight off?? If so, then a smaller pilot hole will definitely make the job easier. Do you have a 2mm drill bit??

[Warthog]

If they have got that colour then they have got VERY hot, but I don't need to tell you that do I?

Oh yeah... I knew that!! Honest, guv'...!

No seriously I did....

Another thought just occurred to me - are you drilling the holes 5.5mm straight off?? If so, then a smaller pilot hole will definitely make the job easier. Do you have a 2mm drill bit??

I'll try that. Failing that, next time, I'll just drill for 10 seconds then leave for a minute etc... with lashings of first cold pressing, extra virgin olive oil.... If its going to smell it may as well smell sophisticated....

[stageonesimmo]

'sophisticated' - mental!

[Lumiya]

The yellow-blue is overheating, the problem when you overheat something made of hard material like HSS drill bits is that you actually make them softer and they go blunt very easily.

As Lutin says you definately need some form of lubricant when drilling anything but small holes in thin steel. A cutting oil comes as a spray and all you do is just squirt a bit at the tip when you need some. It's something though you can use your old engine oil for after your last oil change...

One word of warning if you do as suggested drill a pilot hole before using a larger bit, If when using the larger bit in a small hole and you press to hard then the bit will snag and dependant on the power of the drill the work can be snatched/spun around and that's the easiest way of getting a nasty cut. Wear gloves and/or hold the work piece in a vice.

Kymmy

[j]

As Kymmy has said when drilling any metal you need to use a pilot drill and then slowly move up to the correct hole size. If you dont you will prematurly wear out the the drilling surface by over heating. You need to keep you feed constant and your speed as slow as possible, The cooler you keep the drill tip the better the cut and the longer the drill will last. use pen oil.

[Warthog]

Well, its been a while since I started this thread and I have put its advice to good use today. 13 holes, 3 sizes no busted bits. Some scottoil, low revs and plenty cooling breaks. Top stuff guys!!

Thanks for the advice: very low aggravation levels and very satisfactory outcome. Get some!

[davsato]

i know youve done your project now, but a word or two of advice for people in the future,
1/once youve burned out a drill in steel the drill is now useless but the heat generated has also work hardened the metal around the hole. this could lead to cracks in the future radiating out from the hole. HSS drills are ok on monkey metal but for S/steel, carbon steel etc you can get good drills like TCT or cobalt that will go like a knife through butter without much heat. they cost more but good tools always do, and last a lot longer.

2/a pilot drill should be only barely bigger than the web of the final drill (the little flat bit at the tip between the flutes) and if you are putting big holes in thick material you should step up the drill sizes, not try and do a "one'er"

3/if youre drilling sheet and you cant afford a decent set of rotobors or the like then i recommend a 'stepped drill', they are brilliant and quite cheap these days.