Regrinding Twist Drills to drill Brass.

[gus]

Hi Members,

Just wondering is Gus the only/lonely stubborn guy who tried very hard not to regrind rake angle to eliminate drill snatch.Reason was fear of the unknown.
Took me more than 15 mins inserting and retrieving snatched drill while drilling the brass cam and getting no where.Gave up and grind rake to 90 degrees.
Finished drilling the 9mm thru hole in 2 minutes. Just felt like kicking myself for being so stubborn for last 52 years.

 

[bb218]

I grind as normal then slightly dull the cutting edge to eliminate grabbing.

Mike

 

[Herbiev]

I also grind as normal then drill a brick to dull the edge.

 

[Wizard69]

Hi Members, Just wondering is Gus the only/lonely stubborn guy who tried very hard not to regrind rake angle to eliminate drill snatch.Reason was fear of the unknown. Took me more than 15 mins inserting and retrieving snatched drill while drilling the brass cam and getting no where.Gave up and grind rake to 90 degrees. Finished drilling the 9mm thru hole in 2 minutes. Just felt like kicking myself for being so stubborn for last 52 years.

You are not the only stubborn one here so don't feel bad about being stubborn.

As to brass, sometimes it pays to keep a separate set of drills that have the rake adjusted. The same drills come in handy for plastics and other materials subject to cork screwing. If not a whole set at least a keep the common sizes you use separately sharpened so that you reach for the right tool as required. At least at work I'm often in a hurry and try to get buy with conventional rakes, which can lead to the problem you describe. Being able to reach for the right tool is a big help.

 

[gus]

You are not the only stubborn one here so don't feel bad about being stubborn.

As to brass, sometimes it pays to keep a separate set of drills that have the rake adjusted. The same drills come in handy for plastics and other materials subject to cork screwing. If not a whole set at least a keep the common sizes you use separately sharpened so that you reach for the right tool as required. At least at work I'm often in a hurry and try to get buy with conventional rakes, which can lead to the problem you describe. Being able to reach for the right tool is a big help.

Hi Wizard,

Thats a good idea. Will buy a box of 3-----------13mm drills and grind the popular sizes to drill brass/bronze. In fact these modified drills will still drill mild steel though a wee bit tough to cut well.Sick n tired of drill grabbing.

Trust this tip will be useful to new HMEM members and the obstinate members too(Gus included).:hDe:

 

[gus]

Clamping brass plates to drill press table is difficult with ''G" clamps. Brass plates must be held down firmly to prevent drill snatching and plate coming loose and go into a wild spin and caused serious hand/finger injury.
While shopping in HongKong last year,came across these quick action snap clamps. With fixtures done,drilling brass/copper plates no longer hazardous.
With drill press sitting on top of Tool Chest, access to drill bits and chuck key now a breeze.
No longer have to run to the main ToolMakers Chest to get drills.
Tool Chest Drawer will have room to store these quick release clamps.
Clamps are M.I.T. aka Made in Taiwan.

 

[Krutch]

All one needs to do is stone the cutting edge to keep the helix from "screwing" in. A .010" to .015" flat on the edge of the drill cutting end will suffice to stop burying the drill in the brass and other soft materials. No need to alter the heel or angle. The flat alone does the job.
The idea of a set of drills for brass and such is a good idea. The cost is overcome by the convenience of a "ready" set.

 

[gus]

I have very bad experience drilling copper pipes.The drill snatch/grab would ruin the hole meant for socket mounting on mini steam boilers. Spent so much time to DIY and soft solder on the end caps,I decided to play safe. Regrind drill bit. No grabbing/snatch and good hole. Soft soldered the filler socket. Foto shows Fuel tank done.

 

[gus]

Quick Action Clamp put into the act to hold down engine crankcase cover to drill 1/2 hole.Poor hold down would mean a ruined piece. Happy with clamping power .For the 1/2 tapping, two clamps required.

Bought the clamping device in HongKong while walking thru Canton Road where all the hardware stores are. You could buy all your cutting tools from here. No need to bargain since price is so cheap compared to sellers' market on Singapore.Being able to speak your own mother dialect(Cantonese) helped. The Chinese National Dialect is not preferred.

 

[bazmak]

I keep a set of cheap blunt drills for brass.I built a set over the years of well used worn drills.Regrind the rake if you must.I have a full set of metric high quality drills used only for selected jobs.Main drilling is done with a 3rd set
of well used drills built over the years.If im drilling fence posts in the garden
i usethe main set,i only use the quality set for model engineering etc
Makes sense

 

[gus]

Hi Barry,
Just ground a set of old drill bits for Brass and Copper. Gus been very stubborn/obstinate and had jobs 99% completed except one last hole and job piece ruined beyond salvaging by a drill bit not ground for brass.:wall:

 

[bazmak]

I sympathise its hard.I just broke my 1/8 reamer doing what i shouldnt
just lazy,one last hole etc etc

 

[gus]

Its very painful when the last cut/pass and the last hole went wrong and the job piece dead!!!
Gus by now immuned. Go for a tea or pea break. No point rushing.:rant:

 

[Omnimill]

I'm disappointed that one of the dealers like Chronos or Arceurotrade don't sell sets of bits ground for drilling brass. I'd buy a set.

 

[mcostello]

If a person bought a commercially made set, the grind would only be there till the first sharpening. Then they would be in the same old boat as before. Better to learn how to make them Yourself.

 

[goldstar31]

I'm disappointed that one of the dealers like Chronos or Arceurotrade don't sell sets of bits ground for drilling brass. I'd buy a set.

I get a bit lost here. I'm old grumpy and frankly, have seen it all.

Time after time I see something like this and wonder why the question.

Brass is and was always the favoured metal of the 'greats' and they bored millions of holes. So why not do as they did and either do 4 facet grinding or use spade drills?

My reply flies in the face of present practice but brass hasn't changed.

Regards

Norman

 

[Omnimill]

You might be getting on a bit Norman but you're not grumpy. I very rarely sharpen drill bits as I'm not very good at it and quite frankly it's not worth the time learning when drill bits are so cheap, I'd rather drill holes with my time. Having said that I've read time and again that the standard grind on drill bits we buy leave something to be desired and four (and more) facet drills are much superior for most applications. The answer for me would be a decent (foolproof!) drill grinding jig.

 

[goldstar31]

Another Forum has been deeply involved. Might I mention Model Engineering Clearing House- and escape in one piece?

OK, They went off in all sorts of tangents because no one seems to teach that there is little or no difference to grinding a lathe tool and grinding an end mill or a slot drill or a conventional ( as we know it) twist drill. Believe me, if you square the end of a scrap twist drill you have an end mill of sorts.

What no one will tell you is that a 4 facet drill doesn't need a centre or Slocombe drill. No one will tell you that you can do the secondary clearance on a twist drill and it doesn't really matter whether the angles on both lips are - a bit different. What does matter is 2 lips of EQUAL angle and EQUAL length.

Am I right? Within certain bounds, grinding a conventional lathe tool might have three angles but it the one at the cutting edge that does the fine cutting- or NOT? The same applies to your drill or , bluntly(?) an axe or knife.

No body seems to be able to get through the grey matter and say, it is all so similar. It may be different in a factory where cost and time and heaven knows what is important but not in my little wooden shed.

I'm being grumpy- but I'd be happier if the concepts were there.

Norman

 

[Swifty]

Great to hear from you again Norman. Drilling the first hole in brass is no problem with ordinary drills, just be careful when you break through. It's the follow up drills that are the problem, these need to be ground with a slight negative relief or have the end of the flute ground square, negative top rake on a brass turning tool, same on a drill.

When I'm drilling the first hole in brass, I use the quill to get close to the bottom and then clamp the quill and raise the table slowly until the drill breaks through. Of course, this can only be done on mills with knee tables.

Paul.

 

[goldstar31]

Apologies for delays in replying but most of my time is helping my wife to slowly recover after a paralysed leg following bursitis after a hip operation.
Yea. yea some consultant fellow drilled a hole in the femoral nerve.

So I would like to distinguish what should be obvious but there is a marked difference between a blunt tool and a tool that that remains sharp but has a different cutting edge which is more efficient for brass than steel. If you follow it through the angles for wood change with what sort of wood that is involved and so it is with the type of metal and secondly the thickness as well as the material used in the tool itself.

Trying to simplify what is a mouthful, I would suggest that you use a felt tipped marker on whatever you are using on a cutting tool and literally touch the work and get out a loupe or a eye glass or a microscope to see where the thing has cut- or not cut. I use either a surgeon's binoculars or a £3 child's toy microscope. I also use a dentists mirror if the thing is awkward to see.
As you will discover, there are surprises. It's very old stuff- I didn't invent it.

Cheers

Norman