Crappy drill bits?

[VanMarco]

Hi there,

As I needed to drill some taper thread holes and I hadn't very much budget I bought some cheap drill bits off fleabay.
http://www.ebay.co.uk/itm/260958743...49&var=560090560389&ssPageName=STRK:MEBIDX:IT

(got the cheap "rolled hss, which I can't even make much sense what they mean by rolled")
I just drill two holes with them, got the 11.5mm and the 15.00mm. With the 11 mm it chew right thru no problem, the 15mm instead, it kept getting stuck in the chuck of the press drill, at the very end of the hole, I took the bit off and looked at the very tip and one one side, one piece of supposedly HSS steel chipped off like aluminium? very tiny bit but still?
I was drilling brass, and at like less than 300 rpm with minimal pressure applied.
Now I think bits are cheap stuff, and price was telling of this, maybe it's also operator fault for sure too. Usually when I drill metal, i start by doing a small hole like 3mm, and then scale up 4, 5, 6 7, etc, for the 15mm I reached up to 11 and then went straight for 15mm, maybe thats my mistake?
Maybe I should've drilled directly with the 15mm one?

Thanks

 

[Omniata]

Brass work hardens, this could have been an issue...

 

[optima21]

also with brass you need to stone the cutting edges off the drill bit too

 

[Rig Pig]

I would use a smaller drill for the pilot, if you go too big the drill that follows is only cutting on the corner of the cutting edge making it prone to grabbing

 

[cocker]

Get some better drills .
Loads of better quality bits at autojumbles -
You just need to take something for measuring while you rummage through all the kelter .

.

 

[piman]

Hello Van,

don't go up in small increments, it's slow ands doesn't help. I would pilot with something like a six mm then go straight to the fifteen mm. That and the sharpening to negative rake for brass as the number three post shows. (Although I probably wouldn't bother for one or two holes.)

Alec

 

[penfold]

(got the cheap "rolled hss, which I can't even make much sense what they mean by rolled")

The flutes are roll-forged into the drill blank, where as higher quality drills have the flutes ground out.

 

[VanMarco]

Thanks for all the advice, it seems those bits are total rubbish. the ONLY Bits that kept seizing where those ones. I now bought dormer and heller ones, will try but I think I know what will happen. For the record, the bits in the taper set from LIDL (so not super costly brand) went thru everything no problems.

Thanks again

 

[roofman]

Spend as much as you can afford on drill bits with a good branded name,then go home and learn how to shape and sharpen drill bits and you,ll own the same bits for years to come,they just get shorter...Keep buying cheap drills and its money down the drain.

 

[the artfull-codger]

Brass work hardens, this could have been an issue...

stainless steel can work harden if the drills too fast & rubs instead of cutting but I've not heard of brass work hardening[well not all the brass I've ever machined] certain bronzes can be quite tough at times,as roofman says get the best drills you can,I had to buy in roll forged drills work & they were a fraction of the cost of ground drills, you can take it from there why,also "made" by silverline which didn't help.

 

[penfold]

There's nothing wrong with roll-forged for ordinary use, the cost of ground ones is really only justified for high precision or production work.

 

[Rig Pig]

I use Presto as a rule, Dormer are good too. I bought these a little while ago, reasonably priced and good quality.

 

[brightspark]

Brass work hardens, this could have been an issue...

only when u work it cold then have to aneal it as it goes brittle

 

[Omniata]

only when u work it cold then have to aneal it as it goes brittle

I was wondering if the drill could have been "chattering" as it progresses, thinking it could have been like hundreds of tiny hammer blows creating a hardened rim to the hole...

I'll try and dig a few links up from hobby machinists sites where they had similar issues...

Edit:

http://advrider.com/index.php?threads/machining-work-question-brass-260-giving-me-problems.750672/

http://bbs.homeshopmachinist.net/archive/index.php/t-33440.html

 

[VanMarco]

Spend as much as you can afford on drill bits with a good branded name,then go home and learn how to shape and sharpen drill bits and you,ll own the same bits for years to come,they just get shorter...Keep buying cheap drills and its money down the drain.

Oh hell yes. I always sharpen bits, I have a small jig to use with the bench grinder and nice set rig pig!