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Offline wgr

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drill bit not long enough
« on: January 10, 2009, 08:57:32 AM »
i need to drill a hole in a piece of round stock about 3 feet long. any ideas on making an extension for my bit
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Offline GRIMJIM

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Re: drill bit not long enough
« Reply #1 on: January 10, 2009, 09:39:49 AM »
How big of a hole?  That is going to help make a decision.

They have longer length drill bits at home depot, I have a few in my toolbox at work, I think they are 16" long but I could be mistaken. They may be longer, you can try there, but I think they only go to 3/8".

You could get an auger bit that is long enough to go from both ends and meet in the middle. But it's gonna' be pretty expensive and a pretty large hole.

Maybe you can tack weld a bit to a peice of threaded rod.

If it's big enough for a spade bit (at least 1/2") they make extensions for them but you're odds of drilling straight are not so good. Unless you use a drill press and start with the bit only and add one peice of extension at a time. Still it could run off on you, but if you're turning the peice over and only doing 18" at a time it might work out for you.

The same goes for hole saws. I have had six feet worth of extensions on a hole saw before, but that was to drill an electrical access hole thru horizontal plywood ribs in a preexisting panel.
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Offline mirage1988

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Re: drill bit not long enough
« Reply #2 on: January 10, 2009, 11:52:40 AM »
Need more Info:
Wood or metal - you say round stock makes me think you are talking about metal.
If wood-is the hole diameter critical-if not can you cut the piece in half length wise, cut a slot with a router or dado on a tablesaw and glue it back together?
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Offline Graybeard

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Re: drill bit not long enough
« Reply #3 on: January 10, 2009, 11:56:46 AM »
I believe the normal method of dealing with this problem is to take a piece of approriate diameter stock same as your drill bit and then carefully weld it onto the shank of the bit. I say carefully as it needs to be perfectly aligned. I've seen several extended in such a fashion but doing it is far beyond my skill level. If it is indeed in metal or if the diameter of hole is critical then it's about the only way to do it that I know of.
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Offline wgr

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Re: drill bit not long enough
« Reply #4 on: January 12, 2009, 08:56:30 AM »
its metal not to hard' i have a drill press and thinks and all it needs is to be eye ball close
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Offline SHOOTALL

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Re: drill bit not long enough
« Reply #5 on: January 12, 2009, 09:06:10 AM »
try an eletrical supply house some bits are up to 48 inches . they have them for wood and metal . the smaller sizes are used for making holes in existing buildings to run control wires . Can't remember if kline or greenlee make them .
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Offline DalesCarpentry

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Re: drill bit not long enough
« Reply #6 on: January 12, 2009, 05:55:36 PM »
Like Grim said. I also have some 16" drill bits from 3/8" to 3/4". Go to Home Depot and buy one of them. Then look for a 16" or 20" extenion. The drill bit will fit into it and is tightened with an allen wrench. I hope this helps. Dale
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Offline mirage1988

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Re: drill bit not long enough
« Reply #7 on: January 12, 2009, 07:24:56 PM »
I would advise against welding on an extension. Drill bits are tool steel (A2) or harder that is heat treated, welding it will weaken it and it will probably break- (with my luck it would break when the bit is in the middle of the part). Best bet would be a long bit or an extension. You might have to use several 12" extensions because you likely won't have enough travel on the table of your drill press to fit a 36" tall part and a long bit.
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Offline SHOOTALL

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Re: drill bit not long enough
« Reply #8 on: January 13, 2009, 02:21:04 AM »
over the years on the job we have needed long shank hammer drill and high speed drill bits . we have welded every thing from re-bar to drill rod on them and it will work quite well for a hole or two in a pinch. We found that several beads running along the bit onto the rod worked better than trying to go around pipe welding style . we also over welded the seams in the welds . Some one said the heat will weaken the bit , that is true but the bit will not be perfectly straight and the "weak" joint allows the joint to flex and not wobble as it would if more rigid . If you go the bit ext route , grind a small flat on the bit for the set screw to mate to or epoxy it in as they always find a way to come lose in a deep hole . But again try an electrical supply house as it will save time and most likely money.
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Offline bilmac

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Re: drill bit not long enough
« Reply #9 on: January 13, 2009, 03:22:40 AM »
Since you are using a press, I would drill from both ends. You can center the far end of your stock on the table and start your bit in the center of the working end. When you get half way turn it over and you can start on the center of the other end. Chances are the holes won't go straight, but by drilling from both ends the part you can see will have nice centered holes, and the ugly misalignment will be outta sight.
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Offline oldandslow

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Re: drill bit not long enough
« Reply #10 on: January 13, 2009, 04:16:27 AM »
The shank of a drill bit is not hardened. A drill chuck would not grip it if it was hardened. They can be turned down easily in a lathe. Brazing is the preferred method of adding an extention to a drill bit and is very durable.
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Offline mirage1988

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Re: drill bit not long enough
« Reply #11 on: January 13, 2009, 07:20:10 AM »
Bit extensions or not-on my drill press with the table all the way down the distance from the bottom of the chuck to the table is 24"-you must have a very tall drill press to fit a 36" tall part and a 18" long bit.
Is it an option to cut it in half or thirds, drill the holes then weld them back together? Even if you drill from both ends thru 18" or material your chances of the holes meeting are slim to none. It's kind of a one shot deal- if you have two crooked holes there really is no fix. What is it that you're making? As for the hardened shank on a bit oldandslow ill do a rockwell test on one tonite at work-I've just assumed the whole bit is hardened- we use carbide drills all the time at work and a chuck grips them just fine.
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Offline oldandslow

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Re: drill bit not long enough
« Reply #12 on: January 13, 2009, 01:37:29 PM »
I got the hardened deal from a machinest buddy who is pretty knowledge about things like that. I wanted him to turn down the shanks on a couple of large bits and asked him if I needed to anneal the shanks. He explained about the shank not being as hard as the bit part and that it was no problem. All the carbide bits I have used have a carbide tip brazed to a steel shank. I'm not talking about masonary bits although they have brazed on tips also but carbide bits made for drilling hardened steels. It will be interesting what the Rockwell test shows.
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Offline GGaskill

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Re: drill bit not long enough
« Reply #13 on: January 13, 2009, 01:52:01 PM »
Getting the hole to come out the other end of the bar will be an amazing feat using a drill press.  You will need virtually perfect alignment to keep it from coming out the side.  This is a task for a lathe.

Try a real machine shop tool supplier like McMaster-Carr or MSC.  They will have a better selection of drills although they won't be cheap.
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Offline mirage1988

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Re: drill bit not long enough
« Reply #14 on: January 13, 2009, 08:00:08 PM »
Oldandslow-I tested a standard HSS (high speed steel) bit 7/16 dia. you were right the shank is softer. At the cutting tip it measured 63.5rh, up about an inch it measured 62 and up to about 3/4 up the flutes it measured 62 to 61.5rh. It was a used bit so it is possible the tip had work-hardened a little. At the shank It measured 20rh. The carbide drills we use are solid carbide with straight flutes for drilling holes in hardened tool steel. I work in a shop that manufactures punch press tooling. The metals we use are A2 (58-60) and M2 aka HSS (61-63) for punches and S-7 (56-58) for dies.
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Offline mirage1988

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Re: drill bit not long enough
« Reply #15 on: January 14, 2009, 12:08:08 PM »
Good thing I ran that test yesterday-I was #37 on a list of 38 that got laid off today :( -Guess Obama didn't save my job!
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Offline wgr

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Re: drill bit not long enough
« Reply #16 on: January 14, 2009, 04:37:58 PM »
thinks for the help guys
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Offline oldandslow

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Re: drill bit not long enough
« Reply #17 on: January 15, 2009, 02:36:00 AM »
Quote from: mirage1988 on January 14, 2009, 12:08:08 PM
Good thing I ran that test yesterday-I was #37 on a list of 38 that got laid off today :( -Guess Obama didn't save my job!

Thanks for the info. Getting laid off sucks and I'm sorry to hear it happened to you. I hope you find something soon.
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Offline mirage1988

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Re: drill bit not long enough
« Reply #18 on: January 15, 2009, 02:07:26 PM »
Went back to work today at a cabinet shop I used to work at- big pay cut though ($23.00 to 15.50 per hour) but at least i'm not in the unenjoyment line. Might have to let the bank take the house back though-we'll see. Wonder if they would let me just keep the garage?-LOL
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