Hard spots in mild steel

One way would be to sharpen a tipped masonry drill up, run slow and with coolant on I have drilled many hard item, may be worth a trying.

Alan made no mention of the steel type,was it black or bright,? mild steel does not work harden,so rule that out,its probably some hard material possibly slag rolled into the metal during manufacture. in recent times i have come across en1 a bright bar with internal laminations due to poor rolling,centrifugally cast,cast iron with internal cracks,all from good suppliers, and the wrong material delivered, No mention was made of the material thickness,it would be interesting to try drilling in the exact spot on the other side of the material to see if the hardness was right through the material or just under the skin on one side.

You can get an effect that feels like the steel has work-hardened part-way through drilling a hole if you get swarf trapped under the drill point which spins with the drill and prevents the point from cutting.

That doesn't seem to be the case here but you can get a similar situation if you have some material that has cold-welded itself to the drill point. I wonder if that's the case here.

Dorma drills and Dormer drills are not the same thing. I would suggest that 3.3mm drills at GBP 0.15 may only be suitable for drilling holes in plasticene.

cheers

Bill

drilling to fast may be the problem

Hi everyone, thank you for your replies. For a start, the steel is 12mm thick and black, not machined up.

My drill set up is a 750watt Makita fixed in a drill stand and has two speeds, High and Low, and I always use the low speed except for when drilling aluminium. I have never had any trouble with this set-up and the power of the drill is more than enough for drills up to 16mm as long as I have drilled a pilot hole first.

I came across the same problem in the same piece of steel, late yesterday using a drill of a similar size, and I then used another new Dormer drill, of the same diameter size, that I used earlier in the day. This time It drilled through the plate ok so my conclusions are that although they were all new drills, the very first one I used earlier in the day had not been sharpened properly.

Just to be clear about the drills, I have the box in front of me and the following information is on the box with the correct spelling.

DORMER

HSS TiN Coated Jobber Drill

Tin Tip

Din338

Brazil

As some one suggested that there are two drlils dormer and dorma, which is the more superior drill to buy?

Dormer are generally considered to be world leaders in drill bit manufacture.

Dorma make windows and I think the ad Michael found had a typo in it.

Neil

Edited By Neil Wyatt on 16/08/2015 11:37:05

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Alan,

When Dormer drills were made in England, they were excellent quality.

I cannot comment on those made in Brazil, because I have never tried one.

As for Dorma ... I have no idea whether it's a brand or a typo ... but [as you may have seen on another thread], I don't trust manufacturers that use 'omage brand names !!

MichaelG.

> I cannot comment on those made in Brazil, because I have never tried one.

I have several split point ones, they are excellent.

Neil

I suspect a typo as this site lists lots of Dormer long series drills, a few 'Dorma' and all at eye-watering prices!

Neil

I only use Dormer drills A002, made in Brazil AND have never had a problem with the drill quality. Greenwood tools are my preferred supplier.

Inadequate level of applied and consistent pressure is often a cause of drilling problems, S/S is a good example of where this is all important.

Architectural feature, "Dormer" window, is spelt the same way and is not a "brand" rather a style.

.

Useful to know that the Brazilian drills are O.K. ... Thanks

It therefore seems reasonable to assume that Alan's steel is the source of his problem.

Sorry, I don't really understand why you mentioned the architectural Dormer ... My objection was to "passing-off" [which generally presumes some similarity of product].

MichaelG.

**LINK**

What's the opposite of passing off?

Neil

Edited By Neil Wyatt on 16/08/2015 15:43:07

What's the opposite of passing off?

Original and unique

.

Nodding off ?

**LINK**

MichaelG.

Dorma is Latin for sleep.

Mornington Crescent

Neil

I would blame recycled steel. I dont think they stir it much :O)

I've drilled a 1950's era 3" U section girder that had soft bits and hard bits with the same drill so it's not a modern problem