|Dave Jones 1||11/01/2018 21:00:06|
|78 forum posts|
Does anyone know if it is possible to buy drills bits with a zero rake for drilling brass? My previous attempts to grind drill bits have failed miserably and I would prefer to buy something ready made off the shelf. Ideally I am after an imperial set. I fell out with my normal drills bits today when I was enlarging a hole on a piece of brass in the lathe. The drill bit grabbed on the brass and tried to pull the drill chuck out of the tailstock.
|Phil P||11/01/2018 21:04:46|
|400 forum posts|
Just stone a tiny flat onto the cutting edge by hand to reduce the rake to zero.
I have a set of drills modified like that for brass use only and they never try to grab.
1718 forum posts
+1... any drills I use that are multiples I stone the cutting edge & put them in a separate box...'brass only'
|Chris Trice||11/01/2018 23:04:44|
964 forum posts
Dormer do very slow helix drills for brass. I've got an imperial set going from 1/16th to 1/4 in 1/64th steps.
|Russell Eberhardt||12/01/2018 11:10:57|
2116 forum posts
Me too. It takes no more than one minute to rub the drill a few times on a credit card diamond sharpener with a splash of water. Much cheaper than buying slow helix drills.
1916 forum posts
Brass is just awful stuff in general to machine,
I don't know why people don't prefer copper or bronze in that regard, the swarf is a lot easier to clean up.
|Neil Wyatt||12/01/2018 12:35:57|
12250 forum posts
I've never had problems with brass. Just keep it securely clamped when drilling, even sheet. I did get through ten 1/32" drills making rivet holes in Southam, but I was having to drill through the unsupported folded-up bodywork.
|2417 forum posts|
That's intriguing - Brass is my favourite metal because it machines so well! I agree the swarf is a pain. Apart from that I wonder if Michael and I are using different alloys?
In my experience as a junior machinist Bronze and mild-steel are OK. Leaded mild-steel is good. Copper tends to tear rather than cut, avoid. Aluminium can be sticky, Cast Iron sometimes has a skin harder than a file and is filthy. Many (not all) Stainless Steels work-harden, and some steels are gritty or otherwise obnoxious when you cut them.
I've read that Magnesium alloys machine best of all, but are no fun if it catches fire!
Does anyone else have favourite or hated metals and if so why?
1916 forum posts
It's mainly the spray that I don't like and cleaning it up. It is interesting though how people come up with different experiences, I was always told how bad silver steel was to machine, and I actually much prefer it to stainless.
Stainless hands down, 304, is the absolute worst, 316 is supposed to be bearable in comparison but I've never used it.
|David Lindquist||12/01/2018 18:31:11|
|9 forum posts||
11895 forum posts
Michael if you don't like the fine spray of swarf when turning brass use some CCGT tip and even CZ 121 comes of in nice ringlets.
If anyone wants some slow helix drills at a good price MSC have some imperial Guhring ones at about 1/3rd list price in their clearance section
Edited By JasonB on 12/01/2018 18:55:44
|Dave Jones 1||12/01/2018 21:32:00|
|78 forum posts|
Guys, thanks for the tip I will get some duplicate drill bits and give them a once once with the sharpening block. Interesting discussion on the metals preference. I really couldn't get on with silver steel (I was threading it for a valve and had some real issues getting a nice thread so I used stainless 316 which worked like a dream). I find that steel swarf burns the back of my hand that is turning the cross slide handle. Brass requires a pair of tweezers on the bench to pull out the small splinters, aluminium sticks to the lathe tool.... maybe I should move to plastics!
|David George 1||12/01/2018 22:04:28|
256 forum posts
Hi Dave I have a few brass drills one is a slow helix type but the rest are ground to have no top rake and never grab and as I need a different size just grind one and keep it with the other brass drills.
A ground drill and a slow helix drill.
1916 forum posts
Thanks, you know I think I already have tons of those tips! I always used them for plastic but I instinctively turned to the uncoated carbide ones rather than those polished ones. I'll have to remember for future reference now.
Luckily I don't have a lot of brass to do at the moment, but it does seem to be a messy affair. I like it when I can just dump the swarf in one clump that doesn't mess up all the lathe ways and manages to get into every crevice and still finding it manages to fly atleast 10 feet away from the lathe somehow.
I used to use a big hardinge collet chucking lathe and always held a sheet paper near the tool when doing brass so I didn't end up with tons of it in my face and hair.
I wonder why Brasso manages to polish brass so well?
Edited By Michael-w on 13/01/2018 07:14:42
|Martin Johnson 1||13/01/2018 09:28:07|
|35 forum posts|
I can add another member to the "stone a zero rake flat" school of thought. Only needs a tiny flat; one of those diamond files or laps will do the job in seconds, then there is less to grind out if you need the same drill for steel.
There is another point though - plan the job so you avoid opening up holes, especially if you are opening up by a small amount. For small holes a pilot drill is a waste of time, and for large holes keep any pilot hole SMALL.
For drilling mating parts, drill the bolted part clearance, clamp parts together and just dimple through with the clearance drill. Dismantle, then drill tapping size starting into the dimple.
|Mark Elen 1||13/01/2018 10:41:42|
|10 forum posts|
Heres a video detailing the procedure:
|Gordon W||13/01/2018 11:26:28|
|1870 forum posts|
I just run a small oilstone along the cutting edges and the flutes. Seems to work well and does not seem to affect drilling steel etc.. Also seems to work well for opening holes / reaming, see earlier thread.
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