# Tapping 10-24 in blind hole SS 304



## Cr23484 (Feb 21, 2019)

Hi everyone,
Need some guidance with SS 304 hex head bolt that I drilled 1.25” with a #20 hss 135 point drill.
Tap worked fine in a steel bolt, but can’t get it started in the SS, even with a chamfer?
Brand new tap, HSS
ANY ADVICE IS MUCH APPRECIATED
C


----------



## P. Waller (Feb 21, 2019)

Machine tapping?


----------



## Cr23484 (Feb 21, 2019)

Cr23484 said:


> Hi everyone,
> Need some guidance with SS 304 hex head bolt that I drilled 1.25” with a #20 hss 135 point drill.
> Tap worked fine in a steel bolt, but can’t get it started in the SS, even with a chamfer?
> Brand new tap, HSS and set up on lathe with out power, tap in drill chuck on unlocked tailstock and bolt in a 3 jaw chuck on an Emco Maier Compact 5 mini lathe.
> ...


----------



## mikey (Feb 21, 2019)

Use a larger driil. A #19 or even #18 will usually work. Use enough feed pressure to keep the drill cutting continuously; do not dwell so you don't work harden the work. Use cutting oil.


----------



## Cr23484 (Feb 21, 2019)

P. Waller said:


> Machine tapping?


Hand tapping on lathe , not under power
Thanks


----------



## Cr23484 (Feb 21, 2019)

mikey said:


> Use a larger driil. A #19 or even #18 will usually work. Use enough feed pressure to keep the drill cutting continuously; do not dwell so you don't work harden the work. Use cutting oil.


Thanks, will try a #19, and try to tap with oil( all I have at this point)
C


----------



## benmychree (Feb 21, 2019)

You should buy some tapping lube, oil will not help much;' I like TapMagic, I use it for all my drilling, tapping, most milling, etc.


----------



## Cr23484 (Feb 21, 2019)

benmychree said:


> You should buy some tapping lube, oil will not help much;' I like TapMagic, I use it for all my drilling, tapping, most milling, etc.


I am using olive oil , is there a non-toxic tapping lube or paste?
Thanks 
C


----------



## benmychree (Feb 21, 2019)

I have made hundreds of parts for food contact machinery; these tapping products wash off -----


----------



## brino (Feb 21, 2019)

Cr23484 said:


> I am using olive oil



smells great, but I'd be worried about flys, mice and rats.....
-brino


----------



## Nogoingback (Feb 21, 2019)

Cr23484 said:


> I am using olive oil , is there a non-toxic tapping lube or paste?
> Thanks
> C








__





						Tap Magic Eco-Oil  - Tap Magic
					

Tap Magic Eco-Oil




					www.tapmagic.com
				




This might be better.   Haven't tried it yet, but planning on it.


----------



## Cr23484 (Feb 21, 2019)

brino said:


> smells great, but I'd be worried about flys, mice and rats.....
> -brino


Thanks, gonna try Tapmagic Pro Tap


----------



## mmcmdl (Feb 22, 2019)

Exotap . Bring the chips out .


----------



## ezduzit (Feb 22, 2019)

Cr23484 said:


> Thanks, will try a #19, and try to tap with oil( all I have at this point)
> C



10-24 calls for a #25 drill (0.1495"). Your #20 drill (0.1610") is already unnecessarily oversize at 0.0115" over, so there is no need to go even larger!

Check your tap. It may be a re-threading tap. Don't start the hole with a bottoming tap. And watch out that you aren't work hardening the material when drilling and countersinking. 

Use tapping fluid or even dark pipe threading oil.


----------



## mikey (Feb 22, 2019)

Might check your chart again. #25 drill is for aluminum and other soft materials.


----------



## Briney Eye (Feb 22, 2019)

Cr23484 said:


> Hi everyone,
> Need some guidance with SS 304 hex head bolt that I drilled 1.25” with a #20 hss 135 point drill.
> Tap worked fine in a steel bolt, but can’t get it started in the SS, even with a chamfer?
> Brand new tap, HSS
> ...



304 is a challenge to tap.  It work-hardens badly and does everything it can to make life miserable.

To begin with, did you use a good, free-cutting drill to begin with (preferably carbide)?  If you had any difficulty drilling the hole then you've already caused some work-hardening that will make tapping more difficult.

Start with a high-quality tap, not something from the hardware store.  A lot of people will suggest power tapping with a spiral flute tap.  Working a low-quality tap in and out will harden the 304, eventually seize, and break the tap.  Then you're looking at burning the tap out or starting over.


----------



## brino (Feb 22, 2019)

I like this thread chart.
https://littlemachineshop.com/reference/tapdrill.php

It's easy to find the drill for either 50% or 75% threads, depending on material, application, etc.

for #10-24 it shows:



-brino


----------



## pstemari (Feb 22, 2019)

Castrol Molly-D and a decent HSS tap.

Not olive oil, not a carbon steel big box store tap.


----------



## bhigdog (Feb 22, 2019)

Best tapping lube is bacon grease. .................Bob


----------



## Cr23484 (Feb 22, 2019)

brino said:


> I like this thread chart.
> https://littlemachineshop.com/reference/tapdrill.php
> 
> It's easy to find the drill for either 50% or 75% threads, depending on material, application, , etc.
> ...


Thanks , that is the exact chart I am using.
C


----------



## Cr23484 (Feb 22, 2019)

bhigdog said:


> Best tapping lube is bacon grease. .................Bob


I found some ultima safe tap from 10 years ago, did not seem to work as well as sae 20 motor oil


----------



## Cr23484 (Feb 22, 2019)

pstemari said:


> Castrol Molly-D and a decent HSS tap.
> 
> Not olive oil, not a carbon steel big box store tap.


Tried a Threadwell 10-24 hs tap brand new,
But only have hss drills.
Tried drilling with a #7 for a 1/4-20, not brand new, and had very little chips when drilling , and the tap would not get started.     
The tap was spinning when I used more torque by hand.
Here are the taps, first the 10-24 and then the 1/4-20.


----------



## ezduzit (Feb 22, 2019)

The tap could very well be dull.


----------



## Cooter Brown (Feb 22, 2019)

McMaster Carr sells food-grade cutting oil...









						McMaster-Carr
					

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.




					www.mcmaster.com


----------



## Liljoebrshooter (Feb 22, 2019)

Those taps on the yellow look pretty rusty.
I tapped a bunch of holes in 304 tubing last year. I could get about 8 holes and the tap would start to squeak.  You could feel the difference in cutting pressure in those 8 holes, then just grab another new tap.


----------



## Liljoebrshooter (Feb 22, 2019)

Each of these collars on these has a 8-32 hole in it.


----------



## Cr23484 (Feb 22, 2019)

Beautiful work!
Are those single point cutters?
What are they used for?
Thank you


----------



## Cr23484 (Feb 22, 2019)

Liljoebrshooter said:


> Those taps on the yellow look pretty rusty.
> I tapped a bunch of holes in 304 tubing last year. I could get about 8 holes and the tap would start to squeak.  You could feel the difference in cutting pressure in those 8 holes, then just grab another new tap.


Thank you and to everyone who gave me advice.
I found a brand new Irwin plug tap, and I was able to get it started , but then the tap wrench loosened up.
Going to try to complete it later, very slow and backing off when it feels tight.
Using Safetap, now seems to work better , having the bolt in a vise.
Thanks again
C


----------



## Cr23484 (Feb 22, 2019)

Cr23484 said:


> Thank you and to everyone who gave me advice.
> I found a brand new Irwin plug tap, and I was able to get it started , but then the tap wrench loosened up.
> Going to try to complete it later, very slow and backing off when it feels tight.
> Using Safetap, now seems to work better , having the bolt in a vise.
> ...


Finally successfully threaded the 304 stainless steel bolt with a 1/4-20 brand new tap.
Thanks again to all


----------



## JimDawson (Feb 22, 2019)

Congratulations C  

Here is even more fun one  2-56 tap, 304 SS, 0.200'' deep, #49 (0.073'') drill, blind hole.  4 holes required.  Made it through 8 holes (2 parts) without breaking the tap.  Power tapped in the Haas.  Just did these about an hour ago.

Sorry, I can't show the part.















Tapping speed 10 rpm






And a bonus, 3/64 (0.047'') end mill in 304 stainless in an ER 32 collet.  We were out of the ER 11 Holders.  The coolant stream dwarfs the endmill


----------



## Cr23484 (Feb 22, 2019)

JimDawson said:


> Congratulations C
> 
> Here is even more fun one  2-56 tap, 304 SS, 0.200'' deep, #49 (0.073'') drill, blind hole.  4 holes required.  Made it through 8 holes (2 parts) without breaking the tap.  Power tapped in the Haas.  Just did these about an hour ago.
> 
> ...


Wow, that is amazing!  Machine taps look very cool!
Thank you for the congrats Jim!
C


----------



## Liljoebrshooter (Feb 23, 2019)

Cr23484 said:


> Beautiful work!
> Are those single point cutters?
> What are they used for?
> Thank you


They are telescoping stands for w
	

		
			
		

		
	




	

		
			
		

		
	
ind flags I use for benchrest shooting


----------



## Cr23484 (Feb 23, 2019)

Liljoebrshooter said:


> They are telescoping stands for w
> 
> 
> 
> ...


Very cool!
Thanks
C


----------



## stupoty (Feb 23, 2019)

Cr23484 said:


> I am using olive oil , is there a non-toxic tapping lube or paste?
> Thanks
> C



I have used vegetable oil as a cutting lube , be careful about mess it can set like a rock 

Stu


----------



## stupoty (Feb 23, 2019)

Cr23484 said:


> I am using olive oil , is there a non-toxic tapping lube or paste?
> Thanks
> C



This is what I use by the way, apparently it is approved for use on water pipes.









						Thread Cutting Oil | RIDGID Tools
					

For use with Steel and Stainless Steel, Low odour, Anti-Mist, Free from Chlorine, Silicon and PCB's, Performs to -18˚C, Water washable, Available in spray cans.




					www.ridgid.eu
				




Stu


----------



## rwm (Feb 23, 2019)

Tangentially, I have been using "machine" taps in my Lassy hand tapper and on the lathe with good results. They seem to clear the chips better. Is there a reason these are called machine taps and is there I reason I cannot use them with good alignment by the lathe etc?
Robert


----------



## Cr23484 (Feb 23, 2019)

stupoty said:


> This is what I use by the way, apparently it is approved for use on water pipes.
> 
> 
> 
> ...


Thanks Stu


----------



## mmcmdl (Feb 23, 2019)

rwm said:


> Tangentially, I have been using "machine" taps in my Lassy hand tapper and on the lathe with good results. They seem to clear the chips better. Is there a reason these are called machine taps and is there I reason I cannot use them with good alignment by the lathe etc?



There are machine taps . Expensive . HSS . All kinds of different grinds for various materials and applications . Gun , plug , bottoming , spiral , exo , coated , non-coated , the list is endless . You can use these most anywhere in the correct application . 

There are " maintenance taps " . Cheap . Sold in hardware stores , the Repot , Lowes etc . Used mostly for reforming a damaged thread . High carbon , NOT HSS . They do cut a thread but not very good . They dull very easily . You will not tap or re-tap a thread in a hardened part . It will sieze and break . Specifically sold to " home makers " not wanting to shell out $30 for a 1/4-20 tap .


----------



## JimDawson (Feb 23, 2019)

rwm said:


> Tangentially, I have been using "machine" taps in my Lassy hand tapper and on the lathe with good results. They seem to clear the chips better. Is there a reason these are called machine taps and is there I reason I cannot use them with good alignment by the lathe etc?
> Robert



No reason at all.  But you do have to use the right tap for the job.  As Dave says above, there are many different styles of good taps, none of them sold at the big box store.



mmcmdl said:


> Specifically sold to " home makers " not wanting to shell out $30 for a 1/4-20 tap .



You're buying at the wrong place, I only pay about $15 for a 1/4-20, but that 2-56 tap was $26


----------



## mmcmdl (Feb 23, 2019)

My account is from MSC or Grainger , neither are cheap !


----------



## Salvor6 (Feb 24, 2019)

How about using a roll-form tap? There are no chips with a roll-form.


----------



## rwm (Feb 24, 2019)

I guess machine tap is not a precisely defined term. I always thought it referred to spiral flute tap that get be hard to keep straight by hand. Apparently this is not the case.
Robert


----------



## pstemari (Feb 24, 2019)

Salvor6 said:


> How about using a roll-form tap? There are no chips with a roll-form.


In a work-hardening stainless? That doesn't seem likely to end well.

Sent from my Pixel XL using Tapatalk


----------

