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Drilling steel.

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New Dexter
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Drilling steel.

Post by New Dexter »

I am sure there are some engineers on this forum who might have the answer. When drilling with larger drill bits I use the slowest speed my pillar drill can provide. 180rpm. However, having drilled a pilot hole, then larger and larger bits but when I try to use the bigger ones they drill through the hole and when they have almost reached the end of the hole they jam. My local blacksmith explained that I was "hitting the flutes". This I understand but how to avoid the bits jamming. It's irritating and time-consuming.
Does anyone have any suggestions please?

Chris_R
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Re: Drilling steel.

Post by Chris_R »

I think the drill bit is turning too slowly so it gets caught.

classiclife
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Re: Drilling steel.

Post by classiclife »

Chris is correct and 180rpm is far too slow to overcome the resistance of the larger drill flute edges - there is insufficient torque at that low speed to ensure a clean and progressive cut.

Once the pilot hole has been completed and provided the item to be drilled has not been disturbed, then the logical step is to increase the drill speed when using larger drill bits. TBH, you can use a fast speed even when drilling pilot holes.

The other issue of too low a speed, is that if the drill bit is not progressing with its cutting action it will generate unnecessary excessive heat which in turn causes the drill flutes to become less effective; in essence it becomes blunt - which can be witnessed by discoloration of the bit.

Regards.

Richard.
1968 Daimler V8-250 Saloon
DLOC East Sussex Branch Secretary
DLOC 2.5L V8 & V8-250 Registrar - https://www.dloc.org.uk/v8-250
DLOC 2024 International Rally - https://www.dloc.org.uk/rally-2024

Stan Thomas
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Re: Drilling steel.

Post by Stan Thomas »

Having drilled a small pilot hole, (and I assume your work-piece is clamped in a machine vice) then use the correct size larger drill in one go, and keep a steady pressure onthe drill. Err to the side of a low speed as you are doing

Ignore the advice to increase the hole in stages with progressively larger drills as a large drill cutting only the perphery of a hole will snag - which is your problem.

Chris_R
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Re: Drilling steel.

Post by Chris_R »

Or use a step drill.

qantasqf1
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Re: Drilling steel.

Post by qantasqf1 »

Stan, I agree. that’s exactly what I was taught.
Steve

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Re: Drilling steel.

Post by New Dexter »

Thank you Gentlemen for all your comments. Usually I use the step-by-step approach but now will adopt the pilot hole to finish hole technique. However, there are times when I have a component which needs to be bolted to something. The hole in the component is just over 16mm while that in the other item is 12mm. Thus I have to drill out a 12mm hole, which is where the problem arises.
I will try using a faster speed.

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