WallerZero
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| posted on 9/11/15 at 11:06 AM |
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Counterbored Holes
Hi All,
I'm looking at doing some adapter plates and I need to do some counterbored (or flat bottom/dowel) holes in aluminium/steel - yet to be
decided... anyway, I am trying to find something that fits into a power drill rather than a lathe or mill but struggling to come up with anything
yet...or if anything like that even exists?
Cheers
http://zachsgbszero.blogspot.co.uk/
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redturner
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| posted on 9/11/15 at 11:30 AM |
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Depending how large you are looking for maybe you could get away with an end mill, if the work is securely fastened down. Alternatinely, ground a
drill to the shape you require....
[Edited on 9/11/15 by redturner]
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Myke 2463
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| posted on 9/11/15 at 11:30 AM |
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Re sharpen the same size drill without the normal angle to give flat bottomed hole.
Be Lucky Mike.
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WallerZero
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| posted on 9/11/15 at 11:53 AM |
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Thanks for the quick responses guys. I'd be looking at doing a couple from around M6 to M12 bolts so even with the allen key type bolts
I'd be looking up to around 20mm I guess? Unfortunately my drill only has a chuck that accepts up to 10mm shanks and struggling to find anything
that suits...
The aim was to do it myself rather than have a machine shop do everything (time and money etc)
http://zachsgbszero.blogspot.co.uk/
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gremlin1234
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| posted on 9/11/15 at 11:53 AM |
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this is hss, so should do ali, drill hole, then use this for counterbore
http://uk.rs-online.com/web/p/counterbores/5089266/
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HowardB
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| posted on 9/11/15 at 12:04 PM |
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I'd get a drill ground, there are various other options,. end mill in a router, wood bits used carefully, forstner cutters, etc, but a step
drill is the easiest. As you have a 10mm chuck you'll require blacksmiths drills, they have a reduced shank for smaller chucks.
The issue maybe that a large drill reground will cost more than getting someone else with the correct kit to do the job,..
hth
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again  and goes zoom)
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WallerZero
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| posted on 9/11/15 at 12:14 PM |
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Yeah I'm putting together a CAD model and using scale paper print outs to help validate my measurements. Only worry I have is going from CAD to
finished part...Looks like I'll be taking the plunge with a machine shop and have faith in my own work haha
http://zachsgbszero.blogspot.co.uk/
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owelly
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| posted on 9/11/15 at 12:25 PM |
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I've used these sort of things in a pillar drill.
http://uk.farnell.com/ruko/102411/counterbore-hss-m6/dp/282390?mckv=WUEAIbrX&CMP=KNC-GUK-FUK-GEN-SHOPPING-RUKO&categoryName=&CAGPSPN=pla&a
mp;gclid=CM2Y3-Oqg8kCFVOZGwod-oYJ0A&gross_price=true&ost=282390&categoryId=&CAWELAID=120173390000304974
[Edited on 9/11/15 by owelly]
http://www.ppcmag.co.uk
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MikeRJ
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| posted on 9/11/15 at 12:48 PM |
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You can fairly easily turn a standard HSS drill bit into an acceptable counterbore bit on a bench grinder.
You can either make the end completely flat (even easier if you start with a wood bit) and just use it to flatten the bottom of a hole drilled with a
standard bit, or grind a spigot of appropriate diameter in the middle, in which case you can just drill the clearance hole for the bolt, and then
drill the counterbore.
[Edited on 9/11/15 by MikeRJ]
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coyoteboy
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| posted on 9/11/15 at 12:53 PM |
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Hmm a re-ground drill in anything other than a mill will end in chattery nightmares from hell at best - snatching and demolished workpiece and tool at
worst.
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Rosco86
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| posted on 9/11/15 at 01:20 PM |
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quote:
Originally posted by gremlin1234
this is hss, so should do ali, drill hole, then use this for counterbore
http://uk.rs-online.com/web/p/counterbores/5089266/
nothing wrong with this method
My Build Thread
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redturner
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| posted on 9/11/15 at 01:43 PM |
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I have used my method putting central 10mm plugs in bike cylinder heads. Just make sure it is clamped down tight and use a slow feed.....
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MikeRJ
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| posted on 9/11/15 at 06:53 PM |
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quote:
Originally posted by coyoteboy
Hmm a re-ground drill in anything other than a mill will end in chattery nightmares from hell at best - snatching and demolished workpiece and tool at
worst.
It works perfectly provided you grind the spigot to the correct diameter for the hole. Needs a careful touch on the grinder but it's not
difficult.
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Rich J
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| posted on 9/11/15 at 09:28 PM |
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6 piece counterbore set on special offer here 
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02GF74
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| posted on 9/11/15 at 10:38 PM |
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Almost all of the time we use drill bits for holes to put bolts through or to tap to screw bilts into so it doesnt need to be as precise as for
holding dowels, no idea if this s an issue for you.
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phelpsa
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| posted on 9/11/15 at 10:57 PM |
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quote:
Originally posted by Rosco86
quote:
Originally posted by gremlin1234
this is hss, so should do ali, drill hole, then use this for counterbore
http://uk.rs-online.com/web/p/counterbores/5089266/
nothing wrong with this method
I've used this method for counterboring inserts in a composite monocoque. Was a bit of a risk but actually worked just fine.
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