Dormer A002 Drill bits in sheet metal

[andeep]

I bought a set of Dormer A002 drill bits after years of buying cheap drill bits.

Having an odd problem when drilling sheet metal only experienced when using these Dormer A002 bits.

Initially it drills fine into the sheet metal, but as it gets to the end of drilling when the drill bit is about to cut fully through the metal to the other side, the drill bit seems to get caught and suddenly pulls the drill with it as it turns through the metal and ends up twisting and ruining the metal.

It doesn't do this if using a wood backing when drilling, but sometimes you can't use a backer.

It's just odd as I've never had this problem before, would it be better to get a good set of step drill bits for sheet metal?

 

[Welderpaul]

I have a set of drill bits that i have reground to a very shallow cutting angle - this stops the snagging.

If your Dormer set is anything like mine, the cutting angle is very steep - steeper than normal HSS bits

 

[dan.taylor.1]

All mine do that, you learn to feel when it's going to do it I'm thick stuff, can't say I've drilled much thin with mine really thinking about it!

Dan

 

[andeep]

My problem is the same as this, and is more accurately described by this video:

http://www.youtube.com/watch?v=iFlHLi9uW7s

It would seem a step drill bit would be more suitable for my steel metal drilling needs.

Any recommendations on the best brands of step drills?

Thanks

 

[dannyp]

last few sets of dormer drills i've had have been better after been resharpened, much more agressive than usual and lost there edge disapointingly quickly even with cutting oil.

for lts of holes in really thin sheet i have used spot weld drills to good effect in the past.

 

[madkayaker]

Use step drills quite a bit at work rs brand ones work very well on stainless switch boxes. The 4mm tip goes blunt as well as first step after a while never tried to sharpen as we just get a new set with each big order of boxes (there £300 each so £20 of drill bits doesn't make much difference)

 

[andeep]

Just tried the Dormer bits on some 4mm mild steel plate and its the same problem. If it breaks through it just runs along the flute of the bit and pulls the drill towards the material being drilled. Other times they just catch and the drill bit spins in the chunk.

Not having much luck here!

 

[brightspark]

Just tried the Dormer bits on some 4mm mild steel plate and its the same problem. If it breaks through it just runs along the flute of the bit and pulls the drill towards the material being drilled. Other times they just catch and the drill bit spins in the chunk.

Not having much luck here!

slow down the pressure when its about to cut through . with practice u can get the feel before it does. but not allways

 

[andeep]

slow down the pressure when its about to cut through . with practice u can get the feel before it does. but not allways

I will give letting off the pressure when its going to cut through a go.

When I'm widening a pilot hole the drill bit sometimes instantly catches when just starting to drill and the bit just spins in the chuck, any advice for this?

Thanks

 

[Welderpaul]

When I'm widening a pilot hole the drill bit sometimes instantly catches when just starting to drill and the bit just spins in the chuck, any advice for this?

Thanks

Don't use 'close sizes'. Start with say 6mm, then go 8mm, then 10mm for example.

If you go 8mm-9mm-10mm, it will bite everytime.

Don't do what i see some do - put the drill bit in the chuck, then press hard against the pilot then pull the trigger..It's going to snag.

Helps to start the drill on slow just above the pilot before gently pressing onto the pilot. Once it starts smoothly cutting it won't snag.

 

[brightspark]

I will give letting off the pressure when its going to cut through a go.

When I'm widening a pilot hole the drill bit sometimes instantly catches when just starting to drill and the bit just spins in the chuck, any advice for this?

Thanks

make sure the drill is the full way in the chuck and tight and use a small ish pilot drill about the same size as the chissel point in the middle

 

[gordon stephenson]

As already mentioned, Develop more of a "feel" for what the drill is doing, Pilot hole,if any not too large and east the drill in with a light but steady feed. Same coming to the exit,ease off the pressure a little but keep it drilling, Drills like to cut and not rub,thats the way to lose the cutting edge fast.

 

[Lawnmowerboy]

We run a002 s in all of our cnc machines if not carbide. The a002 drills out the box have a sharp rake for deep hole drilling with a lot of backing off and are good on stainless whilst the coating is still good. Once the coating is gone we regrind them and let the sheet metal monkeys muller them =) there's no hard and fast guide to drill grinding. It takes patience and practice to do to get it cutting even and not one sided as if it is ground off center it leaves a centre pip as it is drilling pushing the drill to one side. This can be useful getting a drill to cut a few thou up to get a fit in a hole if you don't have a ream to suit.