# I Broke A Tap Near The Headstock Of My 10l!!  Aaaaagh!! (saved It Though)



## itsme_Bernie (Mar 23, 2015)

As far as I am concerned, I was taking a risk DRILLING and TAPPING a hole in the bed of my lathe right by the headstock.  I will explain why:

I recently acquired the OEM South Bend Dial Indicator Carriage Stop CL2795RT (Pg 48 Cat 6601) which houses a Federal Dial Indicator.  There are two 1/4-20 holes already tapped in the bed of my 10L (ca.1965) either due to it's vintage, or because mine was sent with the mount for the CL968R Micrometer Carriage Stop.  The holes are in the side of the bed, by the headstock, to accommodate these accessories.




In use, this is a fantastic accessory that works as a carriage dial indicator stop and a hard stop without damage to to dial indicator inside.  The ONLY problem is that the holes are placed such that it doesn't leave room for close-headstock-collet work.  




My DUMB idea was to use one hole, and drill and tap another one step back, around 2-1/2 inches, giving the perfect amount of room to use this with close collet work.  




I put the dial indicator mount where I wanted it and used a transfer punch to locate the hole center.  I then put a long center drill in the handheld drill to reach over the gearbox.  With the tap guide in place, and used a 
I used a drill/tap guide, in this case the Gator tools guide because it is long and thin and has a v-groove which leaves room for chips to fall out.  I drilled about 1-1/4 inches, tapped with a normal tapered tap, and then was following with the plug/bottoming tap.  I was using more pressure to turn the tap than I liked, in my precious 10L  ,but this is cast iron, so I cringed and continued.  I had tapped all but the very last two threads, about .010 in. when **CLICK** ...  The tap broke!!! AAAAAAAGH!!  NOOOOO!! 
Well, I now the breaking pressure of a 1/4-20 tap in cast iron!  




Arrrrgh now, what to do.  Luckily the tap broke sticking out about 1/4 inch, sort of rounded off piece.  I didn't have much hope, but had nothing to lose but to try to twist that little nub out and save the "broken tap of shame" right at my headstock!  I tried my big side-cutters from my contracting days in college, pushed the tips flat against the lathe, and grab and turn... but it just kept crumbling the nub smaller and smaller.  




Then I remembered my can of "creeping" Kroil!  Two drops on the little nub and I SAW it creep and capillary right into that hole...  Then one last try pushing the side cutter as hard as I could against the lathe, and squeezing as hard as I could, and turning lefty-loosey and I felt something give!  I wasn't sure if I just crumbled the rest of the tap or actually turned it, so I got really close and it finally turned YESSSSS!!! 
Here is the broken piece extracted a minute later:




Trust your fingers when hand-tapping!  DON'T go that extra turn if you have to force it! 

Here is the final new placement, much more useful!  I highly suggest it in this position.

Bernie


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## Mark_f (Mar 23, 2015)

How well I know that sinking feeling when you hear the "snap!" as I recently broke a tap in my tool grinder. I'm glad it worked out.


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## darkzero (Mar 23, 2015)

Nice save! I love that protective indicator case for the carriage dial!


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## rwm (Mar 23, 2015)

That story had me in suspense! I think I broke a sweat envisioning it. I'm am pleasantly shocked you got it out.
R


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## RJSakowski (Mar 23, 2015)

Nice save!  I wish I could say the same.  I recently broke two 6/32 taps, one in a piece of aluminum and another in my lathe bed while installing a DRO system on same.  I was able to remove enough of the broken taps in both cases to salvage the work but it was a chore.  I always cringe when hand tapping and seeing the tap twist slightly. On a brighter note, I have been using a tap guide when tapping work on the mill.  I drill the holes and go back to the same coordinates for tapping and it has been a month of Sundays since I had broken a tap.  BTW, a nice job on the mod too.  It looks like a really useful tool.


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## itsme_Bernie (Mar 23, 2015)

Thanks a lot guys!  It was surely a sinking feeling- especially because I had just said to myself- "oh should just stop here- that's already plenty"... Then *snap* ....  Aaaahh.. Hah hah


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## itsme_Bernie (Mar 23, 2015)

Hey Will I never heard of this accessory before, and somehow missed it in my geeky catalog reading.  The body of the indicator holder acts as a hard stop, and inside is the dial indicator, which cannot bottom out before the hard stop.  Pretty cool, and worth copying folks!  If anyone wants measurements, I will be happy to.  

One mod I would make would be to house a full 1 or 2-inch indicator in there!  8)

Bernie


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## atunguyd (Mar 24, 2015)

RJSakowski said:


> Nice save!  I wish I could say the same.  I recently broke two 6/32 taps, one in a piece of aluminum .



Here's a chemistry tip for you :
A broken tap (or any steel tool)  in aluminum can be removed by submerging it in nitric acid. The nitric acid will dissolve the tap in minutes and do nothing to the aluminum (apart from clean off any impurities on the surface). 

Likewise caustic soda will dissolve aluminum and leave iron (steel)  untouched. 

If you can't get nitric acid you can use pickling lime (allum) to dissolve steel out of aluminium, it will take a week or two though.


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## Franko (Mar 24, 2015)

Great tip, atunguyd!
I just tapped 10 – 10-32 holes in my Grizzly 6019 to install an X and Y DRO set. Fortunately the cast iron was soft and drilled and tapped very smoothly. When hand tapping, I've started using my Milwaukee 12v cordless and turn the clutch down to 2-4, switch to low speed, keep a drop of oil on it, back it out every 1/4 inch or when it feels tight, and blow everything  off the tap and out the hole with compressed air. Rinse and repeat until it's deep enough. Not a scary moment in the process., this time. With the clutch set that low, even on that small tap, I don't see any twist.


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## pineyfolks (Mar 24, 2015)

That's a nice setup. And a good save on the broken tap.


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## itsme_Bernie (Mar 24, 2015)

Awesome tip atunguyd! I need to write these down, and keep these around!  

Bernie


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## Thoro (Mar 24, 2015)

Hey Bernie.  That's a really cool accessory that I have never seen before.  

What a terrible feeling when that little *click* happens.  Especially on something like that !

Glad you fixed it.  

Ever tried these tap extractors?  I have 2 sets.....http://www.mscdirect.com/browse/tn/Tap-Extractor-Sets?searchterm=Walton&navid=12106016+4294950532

Never had to use it yet.  I think the only time I needed it, I couldn't find the damn set!


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## RJSakowski (Mar 24, 2015)

Franko said:


> Great tip, atunguyd!
> I just tapped 10 – 10-32 holes in my Grizzly 6019 to install an X and Y DRO set. Fortunately the cast iron was soft and crilled and tapped very smoothly. When hand tapping, I've started using my Milwaukee 12v cordless and turn the clutch down to 2-4, switch to low speed, keep a drop of oil on it, back it out every 1/4 inch or when it feels tight, and blow everything  off the tap and out the hole with compressed air. Rinse and repeat until it's deep enough. Not a scary moment in the process., this time. With the clutch set that low, even on that small tap, I don't see any twist.


For the most part, tapping the cast iron bed, cross slide and tail stock on my Grizzly 0602 was easy.  When I tapped the casting, I turned clockwise about 5/8ths turn and back off 1/4 turn.  If it starts to bind, I carefully work back and forth to release the binding and back the tap out and clean as you suggest. 
However, the tap that I broke was apparently in an area in the casting that was hard.  I should have realized this when I was drilling as it took much more effort.  The hole was one of five for mounting a DRO cover and in an awkward location on the back side of the bed under the ways.  It is possible that I tilted the tap  in the process.  It is also possible that the hard spot dulled the cutting edge.
I ran into another hard spot on the headstock when tapping holes for mounting a reversing tumbler. 
You can see the twisting on smaller taps, 8-32 and smaller.  I used to tap a lot of 4-40 blind holes in aluminum.  I used a power screw driver in later years and had very few broken taps but the slight twisting of the tap was a sign to back off on the torque.  The smallest tap I have run was an  M1.2 -.25, tapping 304 stainless.  Score: one successful tapped hole, one broken tap.  Twisting was very obvious with that tap.


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## RJSakowski (Mar 24, 2015)

Thoro said:


> Hey Bernie.  That's a really cool accessory that I have never seen before.
> 
> What a terrible feeling when that little *click* happens.  Especially on something like that !
> 
> ...


I had a set of extractors as well. IMO, they work very well in the drawer, not so well removing taps.  Usually a broken tap occurs when the tap is well jammed in the hole and those thin slivers that are supposed to slip down the flutes just twist off in trying to back the tap out.  
I have had mixed luck drilling the tap out with a carbide bit.  The carbide will cut the tap well enough.  The problem for small taps  is that it is a tiny and fragile drill.  Once a central hole is made, I use a small punch to shatter the remaining tap and I pick the broken pieces out.


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## RJSakowski (Mar 24, 2015)

atunguyd said:


> Here's a chemistry tip for you :
> A broken tap (or any steel tool)  in aluminum can be removed by submerging it in nitric acid. The nitric acid will dissolve the tap in minutes and do nothing to the aluminum (apart from clean off any impurities on the surface).
> 
> Likewise caustic soda will dissolve aluminum and leave iron (steel)  untouched.
> ...


This is one trick I will have to try!  My chemistry background tells me that this is counter-intuitive .  Aluminum is a less noble metal than steel and should be the sacrificial metal.  Maybe a pacification process like what happens with stainless?  What concentration of the nitric acid do you use?

Nitric acid may be hard to procure here in the States.  Suppliers are fairly cagey about selling the non business customers.


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## fahrphrompuken (Mar 24, 2015)

There's nothing better than redeeming yourself after snapping off a tap!
The dial indicator stop is a pretty slick idea, have never seen that. Could be a great little accessory project.


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## atunguyd (Mar 24, 2015)

RJSakowski said:


> This is one trick I will have to try!  My chemistry background tells me that this is counter-intuitive .  Aluminum is a less noble metal than steel and should be the sacrificial metal.  Maybe a pacification process like what happens with stainless?  What concentration of the nitric acid do you use?
> 
> Nitric acid may be hard to procure here in the States.  Suppliers are fairly cagey about selling the non business customers.


I have 50% nitric acid in my workshop. I actually bought it for anodising aluminum, it is part of the cleaning stage (remove impurities on the aluminum surface). Only advantage of living in a third world country is you can buy as much of these chemicals as you want with no questions asked.


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## RJSakowski (Mar 24, 2015)

atunguyd said:


> I have 50% nitric acid in my workshop. I actually bought it for anodising aluminum, it is part of the cleaning stage (remove impurities on the aluminum surface). Only advantage of living in a third world country is you can buy as much of these chemicals as you want with no questions asked.


I did a quick check of local chemical supplies and it does not appear that it is available locally.  I did find some supply houses on line however.

A word of caution for anyone who happens to try the nitric acid.  In addition to being a strong acid, surpassing battery acid, it is a strong oxidizer. In concentrated form, it is known as red fuming nitric acid (RFNA) which has been used as the oxidant in some liquid fuel rocket engines.  Mixed with hydrochloric acid , it is one of the few solvents for gold. When the acid reacts with metals it gives off red fumes (nitrogen dioxide) which are highly corrosive and toxic. It can react violently with organic matter.  Wear protective gear (latex or nitrile glove are not acceptable, neoprene works) and only use it in well ventilated areas.   A suitable quantity of baking soda should be handy in case of spills.  Dispose of waste properly.


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## atunguyd (Mar 25, 2015)

RJSakowski said:


> I did a quick check of local chemical supplies and it does not appear that it is available locally.  I did find some supply houses on line however.



As I stated before an alternative is to use Alum, commonly called pickling lime in the US. When I was living in Australia I was unable to source Nitric Acid and had to use this, it is very slow though, after about a week and a half the tap had dissolved to the point where I could shake it out of the part, you also should keep the solution warm for it to work. Nitric acid on the other hand will completely dissolve the tap in a matter of minutes.

Alum can be found in food stores where it is sold to make pickles, or in the swimming pool shops where it is used as a flocculant to remove suspended matter in the water. As a side note when trying to find sources for it I found out that prostitutes in SE Asia still use it to tighten up theirs tools of the trade, as has been done in history in the past. I can see how this would work because if you taste alum it immediately makes your mouth want to pucker up.


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## itsme_Bernie (Mar 25, 2015)

Thoro said:


> Hey Bernie.  That's a really cool accessory that I have never seen before.
> 
> What a terrible feeling when that little *click* happens.  Especially on something like that !
> 
> ...



I need to get a set Julian- I even checked my toolbox to see if I was so lucky to have acquired some in the past, but alas, no...  Hah hah..

Bernie


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## itsme_Bernie (Mar 25, 2015)

Fantastic tips guys!  Wow!  I have a lot to write down and, if I'm lucky, never have a chance to try!  Hah hah

Bernie


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## RJSakowski (Mar 25, 2015)

atunguyd said:


> As I stated before an alternative is to use Alum, commonly called pickling lime in the US. When I was living in Australia I was unable to source Nitric Acid and had to use this, it is very slow though, after about a week and a half the tap had dissolved to the point where I could shake it out of the part, you also should keep the solution warm for it to work. Nitric acid on the other hand will completely dissolve the tap in a matter of minutes.
> 
> Alum can be found in food stores where it is sold to make pickles, or in the swimming pool shops where it is used as a flocculant to remove suspended matter in the water. As a side note when trying to find sources for it I found out that prostitutes in SE Asia still use it to tighten up theirs tools of the trade, as has been done in history in the past. I can see how this would work because if you taste alum it immediately makes your mouth want to pucker up.


When I looked up alum in my trusty Handbook of Chemistry and Physics, I found a number of different alums.  They are binary sulfate salts of aluminum and some other metal.  The one commonly referred to as alum is the potassium salt. I take it this is what you refer to.  I say this because in other locations, some of the other salts are called alum.
Aside from your sources, it is packaged as a styptic pencil, used to close up those shaving nicks.  
I will pick some up and give it a try.  It certainly is a lot less dangerous than nitric acid.  It would be another project saver in the trick bag.  Thanks for the info.


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## rwm (Mar 25, 2015)

Looks like you can buy Nitric acid in eBay fron a US seller. I may get some for the next broken tap.
R


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## atunguyd (Mar 25, 2015)

RJSakowski said:


> When I looked up alum in my trusty Handbook of Chemistry and Physics, I found a number of different alums.  They are binary sulfate salts of aluminum and some other metal.  The one commonly referred to as alum is the potassium salt. I take it this is what you refer to.  I say this because in other locations, some of the other salts are called alum.
> Aside from your sources, it is packaged as a styptic pencil, used to close up those shaving nicks.
> I will pick some up and give it a try.  It certainly is a lot less dangerous than nitric acid.  It would be another project saver in the trick bag.  Thanks for the info.


I will try to dig out the bottle I have and provide you the chemical name. I am sure it is a potassium salt. I can tell you my wife refuses to do any tests with it, even in the name of science ☺


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