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Drilling brass

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Bedrock

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Recently, cross drilling a 1-1/2" diameter brass rod, with new drills, the drill bits were catching and jamming, dragging the chuck out of the bench drill column. I seem to recall that there were such things as drills ground specifically for brass. Are they still available? Axminster, etc. don't seem to cater.
Alternatively, I have limited ability to regrind some older, now blunt drills, on an Eclipse guide ( I forget the Eclipse number) which has an asymmetric wheel system to adjust the wings of the drill bit. I bought the Eclipse second hand, without instructions, but cannot see any way to adjust the drill profile.
An advice or copy of the instructions would be very welcome.
 

CHJ

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One answer to a drill snatching in brass is to grind a small negative rake to the cutting edge, not something that can be achieved with a standard drill sharpening jig.

Basically you need clean cutting but not an ultra sharp edge.

Admittedly if you have not developed the skill of free-hand sharpening then a drill sharpening device will give you balanced flute geometry, the place to start in modifying the cutting edge rake.

The art of drilling in various grades of brass was drummed home to me many years ago when drilling holes in 10" cubes of Brass in the assembly of low frequency Radar Waveguide Chokes. One of those spinning round on the end of a 'grabbed drill' is something to be avoided.
 

sunnybob

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I dont see why brass should be a specific problem. If youre drilling round stock, are you grinding or filing a flat for the drill to bite into?
If not you should at least be centre punching for a small pilot drill, and then opening up to the finished size.
Slow speed and a very small amount of lubrication will see the job done.
 

porker

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Brass can be a pain to drill with normal drills but taking the rake off a bit on a grinder stops it grabbing. If it's only a small job I take it slowly and peck it (not easy if you are drilling without a drill stand though)
 

Rorschach

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Brass is grabby. Hone a flat on the cutting edge, you can do it on a stone. It will help a lot.
 

Bm101

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As mentioned above, I just aim to reduce the 'hook' of the bit in the red circle. Few strokes with a sharp file as per the arrow aiming to avoid and leave the centre point sharp. If you have a few spare bits of common sizes it's a 30 second job and basically a free solution. Then put it somewhere safe in a tin labelled 'Specialist Soft Alloy Drill Bits! TM'. and start to build your collection so you don't try to use it on steel later. For 10 non-plussed-daft-as-a-brush-why-won't-it-cut-minutes (Damhikt.) :oops:
 

Trevanion

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I have nothing to add that hasn't already been said except for this excellent 2 minute video by Clickspring detailing the method stated above.

[youtube]pAngKHIZgyA[/youtube]
 

Bedrock

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Thanks for all your helpful replies. It may be that my previous successful attempts have been with slightly worn bits, rather than the brand new used recently.
The brass was held in a small machine vice, firmly held to the table on my small Record drill press. I don't usually put a flat or centre punch, preferring the method I have used for years of finding the centre by pressing a small diameter centre drill on top of a 2 or 3" long shim, pressed onto the top of the piece to be drilled. Any variation in the horizontal of the shim, shows that the drill is not centred. Once the horizontal is found, lock down and drill.
The Eclipse device is numbered 38. Any one have any instructions? - it seems fairly self-evident, but any quirks would be helpful. I will use it to sharpen some older drill bits, add a small negative rake, and set aside.
 

AndyT

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Bedrock":2fohh339 said:
The Eclipse device is numbered 38. Any one have any instructions? - it seems fairly self-evident, but any quirks would be helpful. I will use it to sharpen some older drill bits, add a small negative rake, and set aside.
Are you sure it's 38? I think that was the saw sharpener, with the special non-tapered triangular file, and that the drill sharpener was a 39.

I found this filed on my PC, saved from somewhere:

Manual for Eclipse no 39 drill bit sharpening jig

For sharpening twist drills in a range of sizes from 3mm (1/8 inch) to
13 mm (1/2 inch)

Assembly
Remove small chrome plated screw from strut. Assemble strut
into body. Fit screw and tighten up.

Instruction for use
1 Hold strut with V channel uppermost.

2 Release back stop and slide to end of strut

3 Loosen drill clamping screw

4 Insert drill into V strut with point away from back stop. Hold drill
in V with thumb. Upturn sharpener to bring drill point into view, align
one cutting edge parallel to and flush with front gauge, which is
adjustable for different drill size.

5 Lightly tighten drill clamping screw

6 Swing aside back stop shim and slide back stop into contact with
the drill shank and tighten

7 Swing shim back into V. This will advance drill the required amount
for sharpening.

8 Check that the drill is still correctly aligned with front gauge and
fully tighten drill clamping screw

9 With one hand hold sharpener between thumb and finger in side
recesses and with the other hand hold abrasive paper on a smooth flat
surface

10 Roll sharpener up and down the full length of the abrasive paper
until cutting ceases

11 Fully release drill clamping screw rotate drill 180 and align second
cutting edge with front gauge

12 Ensure drill shank is in contact with back stop shim and tighten
drill clamp screw.

13 Repeat sharpening action

14 If drill is not completely sharpened, repeat from 6

Note
(a) use whole surface of abrasive paper
(b) do not allow wheels to slide
 

Bedrock

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Andy thanks for this. I had to look twice at the no. and opted for "38", as the bottom of the loop seemed to join up.
 
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