Author Topic: New Drills  (Read 1142 times)

Offline PaulR

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New Drills
« on: January 16, 2025, 09:51:09 PM »
What's the best way to take the edge off new drills so they don't grab in brass? I bought a new set today and despite having everything locked down, a firm elbow and working up in small increments, two of the larger bits on the way to a 7mm hole grabbed badly.

Online crueby

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Re: New Drills
« Reply #1 on: January 16, 2025, 10:04:34 PM »
Are you using a drill press with lever feed, or mill with dial feed? I have only had that issue in a drill press. Also, is it 360 or 260 brass? Slow speeds can also make it worse. I've  never done anything  to bits.

Offline uuu

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Re: New Drills
« Reply #2 on: January 16, 2025, 10:07:24 PM »
I use a diamond file and just put a small flat on the cutting edge, in line with the drill shaft, to take away the angle of the helix.  My friend John has a full set of drills modified in this way.  So you grab a drill from the set in the red box or the blue box, depending on the material you're drilling.

Wilf
« Last Edit: January 16, 2025, 10:18:34 PM by uuu »

Offline uuu

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Re: New Drills
« Reply #3 on: January 16, 2025, 10:13:22 PM »
I found this picture online - the one on the left is modified:



Wilf

Offline john mills

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Re: New Drills
« Reply #4 on: January 17, 2025, 01:14:50 AM »
that picture looks right put a small flat so the cutting edge has a neutral rake is still needs to be sharp but no rake slightly negative wont hurt
an oil stone will do it or if you have diamond file that will be good there are straight fluted drills but you might have trouble finding where to get them
the small flate works.

Offline paul gough

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Re: New Drills
« Reply #5 on: January 17, 2025, 01:51:39 AM »
Chris’ video covers how to deal with this. Go to YouTube then, Clickspring,spare parts, 7 Modifying a twist drill for drilling brass. Regards, Paul Gough.

Online crueby

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Re: New Drills
« Reply #6 on: January 17, 2025, 02:13:32 AM »
Comparing your pics to my drills, they came with a second grid right up by the point, more vertical than the flute ends. Maybe thats why I  dont have the grab problem. They are cobalt steel ones made for the aircraft market, where the do a lot of aluminum  drilling, so set up for softer materials?

Offline Jasonb

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Re: New Drills
« Reply #7 on: January 17, 2025, 07:18:27 AM »
Don't work up in increments as that is far more likely to cause a grab.

If doing the drilling on the lathe then nip up the tailstock clamp, if on the mill don't use the quill but lower the head or raise the table though both really only needed for large holes.

I've never stoned the edge of a drill and am still here with a pile of completed models.

Offline PaulR

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Re: New Drills
« Reply #8 on: January 17, 2025, 07:47:27 AM »
Thanks everyone for the information.

Things I forgot to mention: It was a piece of brass angle (not sure exactly which type of brass) and I was using the pillar drill as it was only a clearance hole to accept a part for soldering so more convenient than spending time setting up on the face-plate (I don't have a mill).

Jason - after the first grab I reduced the speed as the bit size increased. Trying to take it easy, I think I went centre drill, 3.5, 5, 6.5, 7mm - probably not the best idea then!
Wilf - this is what I was thinking of doing, running a whetstone across the cutting edges to blunt them a little. The picture is very helpful - thanks.
Chris - Yes, I don't recall ever having this issue when drilling on the lathe in the past, only on the pillar drill - a machine I never enjoy using as it seems to cause problems too often for my liking.

I bought two sets of drill bits so maybe I'll keep one for brass and soften the edges a bit either by stoning the ends or maybe just drilling a load of holes in some scrap steel to 'break them in'!

The part suffered some minor surface damage and the hole isn't very clean and it's a tad off-circular but both can be fixed.

Offline uuu

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Re: New Drills
« Reply #9 on: January 17, 2025, 09:23:41 AM »
I wouldn't recommend blunt drills as a solution to the grabbing problem.  Yes, they won't dig in initially - but if you then increase the pressure on the drill, they might dive in and grab quite badly.

Sharp drills are a joy to use.

Wilf

Offline Tin Falcon

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Re: New Drills
« Reply #10 on: January 17, 2025, 02:37:14 PM »
drill dubbing works, we used it for preventing chip out/ dig in with plastics at a shop i worked at.
the other considerations are tip angle and rake angle I highly recommend some type of multi
 facet sharpening system . I have a drill doctor and a tormex drill attachment.
dubbing is not dulling it is simply changing the rake angle . and yes keep tools sharp.
And always remember proper speeds and feeds .

This is in my opinion a must-read classic sound document for anyone doing serious drilling or drill sharpening.
https://www.sharpeninghandbook.info/Images/Drill_Point_Geometry_nt.pdf

As always your time your dime do what works best for you.


tin Falcon
« Last Edit: January 17, 2025, 03:02:50 PM by Tin Falcon »

Offline PaulR

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Re: New Drills
« Reply #11 on: January 17, 2025, 03:07:20 PM »
This is in my opinion a must-read classic sound document for anyone doing serious drilling or drill sharpening.
https://www.sharpeninghandbook.info/Images/Drill_Point_Geometry_nt.pdf
Thanks for the info and the interesting link.

Offline Tin Falcon

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Re: New Drills
« Reply #12 on: January 17, 2025, 03:54:21 PM »
this gives a good idea of how the Tomek jig works.
dbs 22 manual

https://www.carbatec.com.au/documents/manuals/Tormek/TOR-DBS-22.pdf

Offline PaulR

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Re: New Drills
« Reply #13 on: January 17, 2025, 05:08:50 PM »
this gives a good idea of how the Tomek jig works.
dbs 22 manual

https://www.carbatec.com.au/documents/manuals/Tormek/TOR-DBS-22.pdf

Oof, that's quite a bit of kit... not sure I have the time to dedicate to it!

Offline Jasonb

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Re: New Drills
« Reply #14 on: January 17, 2025, 06:26:03 PM »
Or you can buy a few "slow spiral" drill bits which are intended for materials like brass. The slow helix has much the same effect a sstoning the edges.

 

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