brass thread cutting help please

[Chubman]

when cutting 2ba threads in brass is the drill size 4mm or is it best practice to drill a few thou under size on brass,many thanks

[Paul D]

4mm sounds right, best to use a pillar drill and clamp the work piece if possible, brass tends to "snatch"

[Watermole+]

The right tapping size for 2BA threads is 4.1mm.

It would be best to clamp firmly, as Paul says, but tap by hand-not under power!

You will get a cleaner thread by sticking to the right size drill and using a little light oil on the tap, even in brass.

Regards,

wm+

[ReelMaker]

Dear sir,the best solution with brass is to use oil stone and put a negertive angle on the cutting faces of the drill,this stops the drill grabbing when breaking though.I am sorry that I cannot put a picture up,I was a skilled instrument/tool maker before I retired ,I hope this helps.Reelmaker.

[Chubman]

Dear sir,the best solution with brass is to use oil stone and put a negertive angle on the cutting faces of the drill,this stops the drill grabbing when breaking though.I am sorry that I cannot put a picture up,I was a skilled instrument/tool maker before I retired ,I hope this helps.Reelmaker.

by that you mean a shallow rake on the drill bit reelmaker?

[Paul D]

Dear sir,the best solution with brass is to use oil stone and put a negertive angle on the cutting faces of the drill,this stops the drill grabbing when breaking though.I am sorry that I cannot put a picture up,I was a skilled instrument/tool maker before I retired ,I hope this helps.Reelmaker.

by that you mean a shallow rake on the drill bit reelmaker?

That can help, Reelmaker is referring to the cutting angle of your drill, hold your drill up to the light and you will see the edge is higher at the front and slopes downward towards the back, ideally this angle needs reducing. I was referring to using a pillar drill to drill only, you should of course tap by hand.

[ReelMaker]

Dear friends,if you look at the drill there is a spiral along its length,if you look at the cutting edge at the top of the drill,what is ideal is to put a flat at the point of the angle where it meets the spiral so as to change the edge of the cutting section.The flat needs to go from the outer diameter to the middle.I am not very good at explaining but I hope you can understand.Reelmaker

[Nobby]

I believe it's called the 'relief angle' sometimes:

http://www.bssa.org.uk/cms/Image/Speeds ... steels.jpg

One needs a shallower angle to stop the bit biting into the brass. As WM+ has suggested, I was always told to use a lubricant for brass as not only does it grab the tool, it can also tend to crumble as a result. A strange characteristic for a metal that otherwise self-lubricates rather well.


That said, I was....and still am...always totally rubbish at re-shaping or re-sharpening a drill bit.


I wonder if these are any good?

http://www.ebay.co.uk/itm/dewalt-elu-ex ... 1730962590

[Chubman]

well ive spent a lot of time drilling 316 grade stainless,so i know how to sharpen a drill bit,so brass should be a piece of cake,oh bugger ive broken another i.5 drill bit, so practice makes perfect

[Nobby]

Yeah, I buy those little bits by the dozen these days.......it's a four hour round-trip or three days for the Postman to bring any otherwise.....