How do you drill an un-drillable hole ????

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dobro1956
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How do you drill an un-drillable hole ????

Post by dobro1956 » Sun Mar 03, 2019 7:53 pm

I have been working on repairing my KR Wilson pan jig. There were two places broken on the top of the table at a couple of the pin holes. My plan was to weld up the broken area and then re-drill the 5/16 hole for the locating pin. I found some speciality cast welding rods. The description said they were designed to weld oil soaked , dirty, heat affected cast iron. Since the iron in the pan jig appears to be high sulfur content to the steel and has not responded well to other rods, I thought this rod may work. So today I welded the broken chipped out area, and welded the hole shut. It welded great. I could not ask for the weld to go any better. So I ground down the weld and flattened out the table top area where I needed to re-drill the hole. It ground great. Next I located the hole and drilled a 1/16 inch pilot hole. It drilled OK. Next I drilled a 1/8 inch pilot hole, It destroyed the first bit, so I found a new bit and was able to drill a 1/8 inch hole. I tried to go to a 5/32 drill and no luck so I tried a 3/16 and no luck. I have destroyed all my bits. After looking again at the welding rod package the name of the rod is NOMACAST and in the fine print it says "non-machinable cast iron" OOPs now is a good time for me to read the fine print.... It is also a hardness rating of RC 39. I really hate to grind the weld back out and start over with another type of rod. The iron in the pan jig is a "rotten, high sulfur, core" with a "hard surface" overlay on the top 1/8 to 1/4 inch thickness. This thing is a bi%@# to weld. I have been welding over 30 years and this is the hardest thing I have ever tried to weld ... So today after finally getting a good weld, I can not drill the Da## thing ARagggggggggggg. OK Im done venting ...... Any suggestions as how to drill it ... If not I guess Ill grind the weld back out ........................................................................... :cry:


JEC
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Re: How do you drill an un-drillable hole ????

Post by JEC » Sun Mar 03, 2019 8:02 pm

Since you were able to drill the first hole the area around the hole may have work hardened and you can try
annealing the area with an oxy/acetylene torch.


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Re: How do you drill an un-drillable hole ????

Post by Farmer J » Sun Mar 03, 2019 8:05 pm

I would get a magnetic base drill or position the table in a drill press, a hand held drill won’t work. Then use a carbide drill or end mill


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Re: How do you drill an un-drillable hole ????

Post by Billdizer,Spencer In » Sun Mar 03, 2019 9:17 pm

Snap On, and I would guess others, sell drill bits that will drill out broken drill bits and taps! They should handle your problem.

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Re: How do you drill an un-drillable hole ????

Post by dobro1956 » Sun Mar 03, 2019 9:29 pm

I thought about annealing it. Its such a thick area it may be hard to do. But I still may give it a try. I think it just got to me.... after trying so hard to make a good weld, and then finally, I have a good weld. Then I can't drill it. I think I need a break .... :| I only have to make two little welds, both about a inch to inch and a half long ... Im supposed to be a professional welder, after all I was a Boilermaker welder for over 30 years, I have welds inside a nuclear reactor for crying out loud ... and this thing is kicking my a$$............... it time to go to bed ...

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Re: How do you drill an un-drillable hole ????

Post by Ruxstel24 » Sun Mar 03, 2019 9:45 pm

I have some snap-on cobalt bits, not quite as hard as carbide, but pretty hard. Design for low speed and high pressure. Possibly with lots of oil, I use gear lube.
Good luck :)


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Re: How do you drill an un-drillable hole ????

Post by Scott_Conger » Sun Mar 03, 2019 9:57 pm

I really think the advice to get a magnetic drill and carbide bit will do the job. If for some reason it will not, then I'd call around to find someone with a portable EDM "hole-popper". Likely have to go to a decent sized city with the table in the back of your pickup...
Scott Conger

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Re: How do you drill an un-drillable hole ????

Post by Adam » Sun Mar 03, 2019 10:24 pm

Setting it up on a mill or precision drill press and using a solid carbide drill or end mill is the easy solution. Wish you were close by, could probably do it inside of an hours labor.


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Re: How do you drill an un-drillable hole ????

Post by Kevin Pharis » Sun Mar 03, 2019 11:58 pm

At RC 39 there aren’t many options outside of carbide. HSS CO drills will only live a short life, and only if the RPM is kept under strict control (maybe 20 SFPM?). I have found that drilling a pilot hole in situations like this will cause the following drills to “suck in” and over heat the cutting edges. Without zero backlash equipment it’s very difficult to keep the feed rate under control.

Your welded surface also presents material inconsistencies that will be tough to machine. Point tools like materials that are consistent, and when it’s not... they like to wander or break.

At the point you are at, with the pilot holes, I agree that your best bet would be a mag drill with a carbide endmill. You will need to have fine control over the RPM and feed rate to prevent an even bigger mess. You may even look at a slightly undersized endmill to drill with, and a carbide reamer to take to final size. If you have any runout in the tool, or slop in the machine quill, you could get a sloppy hole and all this work would be wasted


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Re: How do you drill an un-drillable hole ????

Post by Raoul von S. » Mon Mar 04, 2019 12:25 am

Drill an undrillable hole ? Use an anti-drill ! :lol:

Do you have access to anyone with a water jet cutter ? Precise to the micro-degree,
and the solution don't care what sort of material it is or inconsistencies within.
"Working today, for a seamless tomorrow"


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Re: How do you drill an un-drillable hole ????

Post by otrcman » Mon Mar 04, 2019 12:34 am

I'm with Scott on the EDM suggestion, Donnie. Here's why:

Your weld filler material is probably harder than you-know-what due to the rapid cooling rate of the weld. As you already know, it took a ton of heat to do the weld in the first place because of the massive size of the jig. So when you completed the weld, the surrounding material sucked the heat out of the filler material for the world's fasted quench. Just like tossing a red-hot piece of metal in a bucket of water.

So now you've got an extremely hard spot and it's just where you want to drill. A cobalt of a solid carbide might do it, but there's a big chance of breaking the drill off in the hole. Now what ? Well, it's back to the EDM machine after all. Even if the drill doesn't break, you may well run off into base material on one side of the hole in the drilling process. Then your finished hole will probably be slightly oval and the center won't be in the right place.

You might be able to anneal the welded spot. But it's going to take a bunch of heat to get the jig hot enough and then prolong the cooling rate. It'll take a really big torch set and lots of gas to get the job done that way. Probably a job for a furnace rather than a torch.

Dang ! I hate it when things like this happen !


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Re: How do you drill an un-drillable hole ????

Post by Kenny Edmondson » Mon Mar 04, 2019 6:47 am

Before you get carried away and spend a lot of unnecessary money, go to Harbor Freight. They sell a set of Glass Drills for $10 that are sharp carbide tipped drill bits. I used them to drill out a broken off easy out in an Isuzu glow plug recently.


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Re: How do you drill an un-drillable hole ????

Post by Allan » Mon Mar 04, 2019 7:21 am

I have an aversion to welding cast iron, born from previous failures. I leave it to experts in the field. This reluctance has led to repairs to cast items using mechanical means. Before I discovered 'Threadserts', I have repaired oversized holes by drilling, tapping and plugging them with bolts and re-drilling the required hole in the steel plug. Donnie's broken out bits may not have allowed this, but if such a method could be used it will not lead to heat related warpage, cracking and the necessity for preheating of the item to be welded.

I have a spare block put aside for my 1912 van. Very early in its life, it suffered a broken con rod, resulting in a hole in the block skirt and a slot up the bore where the rod attempted to escape. The god of welders in the city was consulted on the necessary repairs. I volunteered to supply cast iron patch pieces from a donor block, but he would have none of it. Instead he had me form patch pieces in 3/16" steel plate. He did not weld the pieces in place. Rather, the block was preheated in a firebrick kiln he has. Once up to temperature, he removed firebricks from the side and brazed the patches in place, replaced the firebricks and turned down the gas flame to its pilot setting, and allowed it to cool overnight. With a handful of sawdust thrown on the wet primer I applied over the repair, it looks just like the rest of the casting. We lost a good one when he retired.

Allan from down under.

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Re: How do you drill an un-drillable hole ????

Post by dobro1956 » Mon Mar 04, 2019 9:38 am

otrcman is correct about the pan jig being a giant heat sink. I did preheat the whole jig to the required 325 degrees required for the rod I used. But the weld still would have cooled very fast. The main thing that got me in this mess is I did not see that the rod is considered un-machinable. The name of the rod "NOMACAST" is even a clue that it is non-machinable. At first I also considered installing a threaded insert made from a 1/2 inch bolt. Then weld the exposed side of the bolt in place, and finally drill the 5/16 hole for the locating pin in the 1/2 inch bolt. But since the table is broken at the hole and I have 1/2 a hole to try and drill a hole in, drill wander would be a big problem. I could do it on a mill, but my mill is broken at this time and its a long way to any machine shops in the Hills of Arkansas. I have to be carefull about pre heat, as the top surface is hardened steel and the core of the pan jig table is soft steel. The pan jigs are made just like an anvil is made. The top is hard enough that a file will barely scratch it. That also creates another weld issue. Part of my weld is on the soft core and the other part is on the hard surface. So I am welding two very dis-similar metals at the same time .. The NOMACAST rods are designed to do that ... Most rods that will weld the hard surface will do fine on the hard surface, but they will not tie into the soft cast core. If I use nickel rods, They will tie into the soft core, but will not tie into the hard surface. I have welded for many years, and the two most aggrivating issues to overcome is "rotten metal" and "dissimilar metals" The pan jig has both .......

Im going to check around today and see if I can find a machine shop who can do the surface grinding of the top. Maybe Ill get lucky and I can get the two holes drilled at the same time ... So far this NOMACAST rod is the only thing I have found to tie into both parent metals .....

Thanks for all the input ...


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Re: How do you drill an un-drillable hole ????

Post by Altair » Mon Mar 04, 2019 11:38 am

I managed to drill out a broken tap using a Dremel tool with a diamond cutting tool.

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Re: How do you drill an un-drillable hole ????

Post by dobro1956 » Mon Mar 04, 2019 10:26 pm

Success :) :) I found a 5/16 cobalt drill bit at tractor supply today. So I thought I would give it a try. I used the torch and did the best attempt at anneling the weld area as I could do with a torch. Then I used a cast iron hogs head located with 5 of the remaining pins, as a drill guide. I made a drill guide bushing to fit the hole in the hogs head and also fit the 5/16 drill bit ... With some cutting fluid in the hole and using a hand drill at a low RPM and as much down pressure as I could. I was able to drill the hole. :) :) .... It was tough going and I was afraid of breaking the bit, but I had success.

The second broken place that needed welded was one of the front holes. So I had no good way to locate it from the top, but that hole went all the way thru the table. So by removing one leg I could use the remaining part of the hole as a drill guide from the bottom. I really did not want to go thru the hard as he## drilling again. So I decided to call the people at Weld Tech. They were the folks I used to work with on the big construction projects when I was still working as a Boilermaker. I was hoping someone would remember me, and I could use an "old favor" . Well one of the younger ladies that was starting to work for them, about the time I retired was still there. We had a nice talk, and then I gave her all the details about my "problem child weld" About a hour later she e-mailed me a full "nuclear grade" weld procedure. Since I have high contaminated cast iron core I was correct with the choice of the NOMACAST rods, since it is designed for contaminated metal and dissimilar metals. I was to use the NOMACAST rods to "butter" the contaminated core cast iron with a "root" pass. I had to maintain a 750 degree pre-heat while welding, and peen the welds after each pass. Making sure to cover all the old metal as well as be sure to cover the tie in between the hard surface and the core cast iron with the NOMACAST. But do not get any of the NOMACAST in the 5/16 hole. Then continue building up the broken area with narrow stringer beads till all that was left to weld was a shallow depression with the 5/16 hole in the bottom of the depression. Then make sure a 5/16 drill bit will still fit in the hole. Then I could weld up the hole and the depression with either 55% or 95% nickel rods. They both would machine OK so I chose the 55% as it is harder than 99% nickel. After welding I needed to "step down" the pre heat from 750 degrees to 450 degrees over a two hour period. So with the wife (welders helper) operating the "rose bud" on the torch we reached temp in about 20 minutes. I made the weld while she checked the temp with "temp sticks" re-heating as needed. After about 30 minutes of welding I was done. Then I made sure everything was still at 750 degrees and wrapped the table top in insulation and my leather welding covers... With the insulation I only had to re-heat one time to achieve the step-down ... For folks who have not been around a "hot weld" 750 degrees is hot enough you can feel your face burning when you raise your hood. It will also burn you thru your clothes while welding if you get closer than a foot to the piece. It will burn you thru your gloves if you hand is against the piece for more than a few seconds ... 750 degrees is the limit for using temp sticks. This weld was the full extent of my abilities to do it at home ...... After cooling for about 4 hours I was able to drill out the pin hole from the bottom side. I had no problem drilling thru the 55% nickel.

Sorry for no pictures of the welding process, we were pretty busy at the time ....

When the Weld Tech lady asked me if I had "buttered" the weld zone, I felt like an idiot. I should have know that... That would be a common practice to do in a problem weld ... I guess I have been "retired" way too long .... But the pan jig now has 10 locating pins and is one step closer to working .......... Thanks for all the input, I needed the support ...... and a shoulder to cry on .....
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dobro1956
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Re: How do you drill an un-drillable hole ????

Post by dobro1956 » Mon Mar 04, 2019 10:29 pm

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Re: How do you drill an un-drillable hole ????

Post by Allan » Tue Mar 05, 2019 2:16 am

Donnie, is buttering a bit like tinning for soldering? I presume you used the hard rods to make the weld good to the contaminated original material and this then allowed you to make the nickel rod weld to the hard rod weld.

Allan from down under.

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Re: How do you drill an un-drillable hole ????

Post by dobro1956 » Tue Mar 05, 2019 7:58 am

Allan, yes "buttering" is similar to tinning in the sense that you are coating the entire weld (or solder) zone with something special to promote bonding. In my case the NOMACAST is designed for welding rotten, contaminated, dissimilar cast iron metals, so it was a good choice for the "buttering rods". One pass totally covering the parent metal (pan jig) is all that was required. But you can also completely weld out the weld area with the "buttering" rods. It just depends what you want the filler material to do. Since the NOMACAST is the better filler material and it cost about the same, I used it to fill out the weld zone. Since I did not want to drill it I paid close attention to not getting any NOMACAST into the 5/16 hole. I did have to make sure that The first "buttering pass" went right to the edge of the hole. Any exposed parent core material would cause a bad bond at the hole edge when filling the hole and depression with the nickel rod. The final fill rod must be compatable with the "buttering rods" In my case the 55% or 99% nickel rods were compatable, and suitable for the final filler at the pin hole .

There is way more involved to making a good weld than just, "weld-er-up". I feel a little dumber forgetting to use the "buttering" process as a solution to this welding issue. But I guess that is what comes with getting older. :oops: :oops: I don't know how many more "favors" I have to use in the future.


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Re: How do you drill an un-drillable hole ????

Post by otrcman » Tue Mar 05, 2019 10:12 am

Well done, Donnie. Part of being a smart guy is knowing how/who to ask when you don't have the necessary information ready at hand on your own.

As far as not knowing how many favors you have left to use in the future, ask yourself how many favors you have done for others. I bet you're still on the strong positive side.

Dick

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