# Two ?s



## Naiveambition (Mar 15, 2016)

When boring is it to your advantage to use cutting fluid.?  Never really paid attention while boring as all of mine have been done dry

And when tapping is it wise to countersink every hole before tapping. Broke another tap. Though I tried using power tapping it didn't go well. Admittingly I think I wrongly grabbed the bottoming tap as my other hole went great.  Just wondering if csinking is better.


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## 10K Pete (Mar 15, 2016)

Naiveambition said:


> When boring is it to your advantage to use cutting fluid.?  Never really paid attention while boring as all of mine have been done dry
> 
> And when tapping is it wise to countersink every hole before tapping. Broke another tap. Though I tried using power tapping it didn't go well. Admittingly I think I wrongly grabbed the bottoming tap as my other hole went great.  Just wondering if csinking is better.



The use of cutting oil depends on the material, cutter, etc. and doesn't depend upon
the process, drilling, boring, turning, etc.

One of my pet peeves is sharp edges. They should always be removed.

One of my sharp edge pet peeves is tapped holes that aren't c'sunk. The right
way is to c'sink the hole to at least the major thread diameter BEFORE tapping. This eliminates the weak part of the partial thread and because it is
done first the c'sinking doesn't roll a burr into the finished thread.

My dos centavos,

Pete


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## tornitore45 (Mar 15, 2016)

Since aluminum tend to stick to the tool is rather rare I cut aluminum dry. WD40 or kerosene is the cheaper stuff I can find in my neck of the woods.


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## Wizard69 (Mar 15, 2016)

Naiveambition said:


> When boring is it to your advantage to use cutting fluid.?  Never really paid attention while boring as all of mine have been done dry


For most materials cutting fluid of some sort improves the result.   Does that mean I use cutting fluid every time - nope but it is smart to consider it.   


> And when tapping is it wise to countersink every hole before tapping. Broke another tap. Though I tried using power tapping it didn't go well. Admittingly I think I wrongly grabbed the bottoming tap as my other hole went great.  Just wondering if csinking is better.





Pete above covered this fairly well but I might go on to say a counter bore or counter sink can be a requirement.    You don't want the weak thread or material pulling up and distorting a machined surface.   So yeah it is a good idea to counter sink though I really doubt that it will stop broken taps.


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## 10K Pete (Mar 15, 2016)

I didn't answer the broken tap question did I? 

It's my opinion, based on decades of tapping holes and quite a few broken taps, that the following list will give you a good start. Flog me if I'm preaching to the choir. Or the Queen. Whatever.

1) Are you using the correct tap for the job?

2) Is the hole the correct size for the material and the type of tap. And    also the method of tapping (hand, power, etc)?

3) Are you using the proper lubrication and application thereof?

4) Is the tap in proper condition- sharp, relieved and generally OK?

5) Are you guiding/supporting the tap properly?

 Assumptions in any of those areas, without supporting experience, can easily lead to broken taps. If you don't know the answers, ASK !!  Even just ask yourself then look up the answers.

Pete


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## Naiveambition (Mar 16, 2016)

Yes to all ?s except for using a designated tapping fluid like tap magic etc...  I've used wd40 for this one and most times pbr, as it has a very oily nature. 

This tap was, I thought my last 4-40, and I'm sure most issues are from mistakenly using a bottom tap first then afterwards finding the taper tap.    Although plans call out .086, my tap drill chart  lists .089 for 4-40.  On my second hole I jumped up to .089 with the countersink and was perfect. I'm sure it would of easily power tapped using the machine without issues. 

And can I weld my hole shut using a mig welder and retap the hole. When removing the old tap the hole opened up a little. I've read some web responses on the subject and there are many different views.  The material I'm using is .125 sheet steel, so hole is rather small an shallow.  Or with the risk of breaking another tap off in the weld , just move up to the next thread if I can?


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## Swifty (Mar 16, 2016)

Naiveambition said:


> And can I weld my hole shut using a mig welder and retap the hole. When removing the old tap the hole opened up a little. I've read some web responses on the subject and there are many different views.  The material I'm using is .125 sheet steel, so hole is rather small an shallow.  Or with the risk of breaking another tap off in the weld , just move up to the next thread if I can?



Welding would most probably work, however if it happened to me, I would make a bigger hole and silver solder in a plug, then redrill and tap.

Paul.


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## goldstar31 (Mar 16, 2016)

I suspect- I said suspect- that your tapping on 1/8th material is also suspect. Unless you have something to keep your tap truly vertical, you stand a big chance of breakage. Recall that you are probably only getting 5 threads- at best.

I'd be using my drill/tap/staking tool to avoid drunken threads and- as you comment- breakage. Oh, on a sharp tap!!!!!!!

My thoughts- others may differ.

Regards

Norman

NB- I'd mig but I'd be crafty. I'd build up a thicker plug, drill/tap and then grind down level.  

I've done a fair amount of 'tin bashing'

N


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## 10K Pete (Mar 16, 2016)

Naiveambition said:


> Yes to all ?s



Not quite....



Naiveambition said:


> except for using a designated tapping fluid like tap magic etc...  I've used wd40 for this one and most times pbr, as it has a very oily nature.



#3 rule followed: WD-40 is OK on thin steel. Tap Magic is way better.



Naiveambition said:


> This tap was, I thought my last 4-40, and I'm sure most issues are from mistakenly using a bottom tap first then afterwards finding the taper tap.



#1 rule broken. Didn't use the correct tap.  Never start with a bottoming tap.




Naiveambition said:


> Although plans call out .086, my tap drill chart  lists .089 for 4-40.  On my second hole I jumped up to .089 with the countersink and was perfect. I'm sure it would of easily power tapped using the machine without issues.



#2 rule broken. Tap hole too small.



Naiveambition said:


> And can I weld my hole shut using a mig welder and retap the hole. When removing the old tap the hole opened up a little. I've read some web responses on the subject and there are many different views.  The material I'm using is .125 sheet steel, so hole is rather small an shallow.  Or with the risk of breaking another tap off in the weld , just move up to the next thread if I can?



As long as the weld is soft, you should be able to re-tap there without problems.

You don't mention rules 4 or 5. Even on thin material those are important.

Post back when you've followed all the rules and let us know how it went. Best wishes on your efforts!

Pete


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## tornitore45 (Mar 16, 2016)

#4-40 tap is the weakest tap considering the relatively high lead for the tap size.

The ability to align the tap perpendicular and keeping it that way is an absolute requirement for all sizes.
Also, when tapping by hand is important to apply a true (balanced) torque without any lateral force.


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