BEST cutter for highly machinable brass

"Lloyd E. Sponenburgh" wrote in news:Xns9FC4A710DBE8Blloydspmindspringcom@216.168.3.70:

I've had very good luck with "slow twist" drill bits. I bought a set years ago, and they are wonderful for brass & plastic. The ones I have were made by Chicago Latrobe.

One size went missing (25/64ths?) a while back, and I tried to replace it. I ordered a slow twist drill bit from McMaster Carr, and received a C-L drill bit, but the twist rate is about half way between normal drills & the ones in my set. I originally thought they had sent me a regular bit by mistake, but they checked their stock, and I compared to both drill types. It's slow, but not that slow.

I don't know if C-L has decided to change the design or what. MSC also sells slow twists, and the next time I place an order, I will probably see what theirs look like.

Doug White

I needed to make some clean holes in brass and happened to mention it to my retired tool and die maker dad. He asked if I knew how to make a scraping edge on a bit. I'm hoping someone else here can give you more technical terms. In essence take a whet stone and flatten the lead edge of each cutting flute so that the bit is scraping chips rather than cutting curls. It hurt my soul to "dull" a brand new bit, but the project worked well. I also modify bits the same way for plexiglass and aluminum. It seems to radically reduce the tendency to grab/lift the material and the burr on the back side.

I wasn't expecting to find much about it, but google "modify drill bit" and "brass drill bit" and there are many articles: here is one with pictures:

another from the dropbox:

[ ... ]

Probably even better with the straight flute drill bits like were made for Yankee push drills.

You know how to "dub" the cutting edge on a drill bit? This does the same thing that the slow twist does for you -- it minimized the rake where the cutting is happening. Take your "sorta slow" bit, or a regular twist bit, and dub it (grind the first 1/16" or so of the rake to a surface parallel to the drill bit's axis.

Check this out and scroll down to the first non-atavar photo. (It is large enough to get your attention anyway. :-)

Enjoy, DoN.

"DoN. Nichols" fired this volley in news: snipped-for-privacy@Katana.d-and-d.com:

No binaries get through, Don. Can you just list a link? Lloyd

Most machinable brasses will have lead in them. I hope you're not in California. ____________________________________________________________________ Gardner Buchanan gbuchana(a)teksavvy(dot)com FreeBSD: Where you want to go. Today.

You probably have the idea by now that you want to avoid positive rake. That may not be a problem anyway, drilling in thin plate, but the idea behind purpose-made cutters for brass is to avoid any significant positive rake that would make the cutter dig in. In the case of a drill bit, a positive-rake cutter can start self-feeding, tear up the hole, and possibly break the bit.

Someone described stoning the lip so the cutting rake is zero -- parallel to the axis of the bit. That's what I do. It only requires a very small flat. If I had to cut a lot of holes, I'd just buy a purpose-made bit for the job. But you really don't need it for brass.

If you want a better finish and you're going to make a lot of holes, consider a drill/reamer combination tool, and nub off the drill-lip rake with a small slipstone.

I didn't see Lloyd's posting for some reason -- perhaps in the killfile in part if not the whole name?

I didn't post a binary, so of course it did not get through. :-)

I thought that I had posted a link, but apparently forgot to cut and paste it into the article.

Here is the URL which I had found before:

Indeed so.

Indeed so.

Hmm ... an interesting product. I don't have any of those, though I do have the combination drill bit and tap which work nicely in a tapping head in the drill press. (Not tried on brass, yet. :-)

Enjoy, DoN.

I would choose a lead free brass alloy for food service!

1. drill then ream
2. Dreamer ( a totally useless tool unless you already have one, I inquired once and it was several hundred bucks and an 8 week wait to get one.)

Remove 333 to reply. Randy

From a brief investigation.. under what looks like the relevant NSF rule-- 4.2.3.2 (FE-2009-12), leaded brass is only permitted in food zone applications when tea, coffee or water are involved, and then only to a maximum of 8% Pb content. No arsenic, cadmium or mercury content is permissible.

Best regards, Spehro Pefhany

You guys presume WAY too much, and are being didactic while not helping.

I have a contract which clearly spells out using freely-machinable brass for the perf-plate. The customer has already spoken on the issue of lead. HE specified brass, waived the lead content issue, and I have it in writing.

So, why would you tell me not to do it? _I_ am not making food with leaded brass -- I am building a machine to the customer's specs, and have made sure he's educated on it. There's no more I need to do.

I cannot predict what he'll do with the device or even if "pasta" is what he's extruding. HE called it a "pasta extruder", and after suitable warnings, that's where my responsibility ends.

Lloyd

In a drag race shop I used to deal with, my buddy Sparky had a sign over his bench that read, "Give the customer what he wants, even if it kills him."

OTOH, you want to make sure it's spelled out very carefully that there is lead in the material, and have him sign something that says that he has read the specs (even if they are his specs).

I usually deliver my electronic and electro-mechanical prototypes and designs with a disclaimer that says that we have tried our best to adhere to the customer's specifications, but we make no warrantee that the device delivered is suitable for any purpose. During our warrantee period (10, 30, 60 90 [or sometimes longer] days, depending on the complexity of the job), it is up to the customer to demonstrate that what we built is not what he asked for. In writing.

HTH

If it were my contract, I'd want to check with them damn revenuers to make sure they wouldn't come after me for doing precisely what the customer wanted, especially concerning lead. In Govspeak, that's the L word.

-- [Television is] the triumph of machine over people. -- Fred Allen

[ ... ]

What size and what material? Looking on MSC's web site, I find a bunch of them in different sizes, mostly HSS.

In HSS ranging between

1/8" $38.05

and

5/8" $129.97

And one which came up in the search in solid carbide.

10mm $116.35 Shank size is given, but not ream diameter.

Enjoy, DoN.