Occasionally I have to elongate by about 6mm an 8mm diam hole in 2-3mm thic k mild steel. A round file would do it but none of my usual sites define th e diameter of their round files. A stepped drill bit would just enlarge the hole which is not what I need. A power tool option would be nice. Any sugg estions ?
hand tool - a punch? Or a nibbler?
I have a small set of what look at a glance like twist drill bits but whilst they have a conventional hss bit to start with, the rest of the bit is more a power file / burr / arbour.
The best use is for drilling a hole in thinner / softer material and then being able to open the hole up or take it in a slightly different direction.
Because it is rotating, if you were trying to extend the hole in just one direction (to turn it into your slot for example), you have to make sure you are applying the side load in the right direction (which may not be the obvious angle).
You might be able to make this work if you had the bit in a pillar drill and pushed the job between guides?
Cheers, T i m
hick mild steel. A round file would do it but none of my usual sites define the diameter of their round files. A stepped drill bit would just enlarge the hole which is not what I need. A power tool option would be nice. Any s uggestions ?
Yes I wondered about those but the description says " Use in wood, plastics , aluminium etc. No mention of steel. Besides I'm slightly chary of Axminst ers tin coated drills as in the past I didn't find them great.
But thanks for the suggestion any way.
Axminster no longer put an email address for technical queries on their si te. When I used an old email address for this query I had it was ignored.
thick mild steel. A round file would do it but none of my usual sites defi ne the diameter of their round files. A stepped drill bit would just enlarg e the hole which is not what I need. A power tool option would be nice. Any suggestions ?
cs, aluminium etc. No mention of steel. Besides I'm slightly chary of Axmin sters tin coated drills as in the past I didn't find them great.
site. When I used an old email address for this query I had it was ignored.
WHOOPS Sorry Axminster. The contact details are under Contact Details. Doh !
Easy as peas. You want a standard cut tooth pattern, 6mm shank, 8mm head carbide burr. Ideally used in professional cylinder head porting equipment at up to 15,000 rpm like mine but they'll do quite nicely in an ordinary drill albeit taking a bit longer.
Part number C081906 in the pdf would suit.
I was thinking of suggesting similar. I have a set of straight versions that are very good at creating odd shaped holes in steel.
This is one of them
Mike
Isn't there some risk that the bearings in an ordinary drill might not be up to taking the side loading if this was done too often?
Chris
OTOH an angle grinder with an 8mm tungsten carbide mortar rake....
I'd think manual filing with a coarse round file might be faster, if you only have normal drill speeds.
In my experience, one problem with trying to make slots using "drills with side-cutting teeth" is cutting in the direction you want to go, because the rotating tool deflects you sideways. Not an issue with Dave's high speed cutters for two reasons, first the power tool is designed to be easy to hold and stabilise, second at very high speed you need little applied force, so the sideways force is small compared to the mass of the tool and they are therefore easier to keep "on track".
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