Tips for tapping stainless rod

[dieselmudder]

I picked up a handful of an unknown grade of 3/16 stainless rod pieces at a local metal warehouse.

I'm wanting to drill and tap the ends 6-32 for studs to attach rod ends. Turning down and external threading is another topic, for later.

Just looking for tips from anyone that's done this successfully. I do have a mini lathe that I can chuck my tooling, and rod into for alignment.

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[BigSki]

In order to be successful, you need to know the grade of the SS. 303 is good for machining, tough to weld. 304 is tough to machine, better for welding.

I made suspension links for my deadbolt last year, I used a lathe to make the tap hole. Don't "peck" the hole ( it will work harden very quickly), I just plunged full depth on one pass and used pink Boelube to help with the drilling and then tapping. I have a thread in this section somewhere when I did it.

[ferp420]

If you heat it up it will soften it up enuff to drill and tap but then you have other issues but it works lol i think turning it down and threading it will be easyer i use a drill and a file to turn down the rod

[dieselmudder]

Originally Posted by BigSki

In order to be successful, you need to know the grade of the SS. 303 is good for machining, tough to weld. 304 is tough to machine, better for welding.



I made suspension links for my deadbolt last year, I used a lathe to make the tap hole. Don't "peck" the hole ( it will work harden very quickly), I just plunged full depth on one pass and used pink Boelube to help with the drilling and then tapping. I have a thread in this section somewhere when I did it.

Good to know. What about tapping? Did you do the forward backward method, or run it all in one shot?

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[CODYBOY]

Originally Posted by dieselmudder

Good to know. What about tapping? Did you do the forward backward method, or run it all in one shot?

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In my experience tapping stainless if you don't clear your tap every half turn you're going to break it from the chips hanging up. IMO if you try to do it in one shot the heat will weld your tap to the stainless.
Ernie

[BigSki]

Originally Posted by CODYBOY

In my experience tapping stainless if you don't clear your tap every half turn you're going to break it from the chips hanging up. IMO if you try to do it in one shot the heat will weld your tap to the stainless.
Ernie

This.

Use a hand tap wrench and Boelube or Tap Magic cutting fluid. You can feel the tap loading up. I also went one drill size larger than the drill chart recommended, it was still around 65% thread engagement, plenty strong enough of a thread for what it was made for.

[Rattzo1]

Old machinists trick... use anti seize I like the brown/copper stuff personally but the silver works just as well. Use it with all tapping it really helps especially aluminum and ss

[ferp420]

Originally Posted by Rattzo1

Old machinists trick... use anti seize I like the brown/copper stuff personally but the silver works just as well. Use it with all tapping it really helps especially aluminum and ss

"like"

[celticsun33]

Originally Posted by dieselmudder

Good to know. What about tapping? Did you do the forward backward method, or run it all in one shot?

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if you're gonna tap stainless you better have a good sharp tap. Use a good cutting oil, go slow, clear out the hole every turn or so, and lastly with a 6-32 hold your breath and pray.

[Szczerba]

Ehhh. Just get a machine tap, throw it in a drill and hammer down.
And some cutting fluid. Been tapping for years with them in the hobby. Just get a few for different materials. Ie I two taps for each size I need. One tap only cuts metal and the other only sees plastic tapping.

Also, there are blind taps, through hole taps, etc

https://www.mcmaster.com/8302a12

[CODYBOY]

Originally Posted by Szczerba

Ehhh. Just get a machine tap, throw it in a drill and hammer down.
And some cutting fluid. Been tapping for years with them in the hobby. Just get a few for different materials. Ie I two taps for each size I need. One tap only cuts metal and the other only sees plastic tapping.

Also, there are blind taps, through hole taps, etc

https://www.mcmaster.com/8302a12

I just ordered a couple to try, thanks for the heads up!
Ernie

[hibbs]

I’m late to the conversation but I just did 2 complete trucks worth of 1/4” stainless links. I was having an awful time but found several things that helped a ton. Several have been mentioned.

-do not allow the rod to get hot. I ground mine to final size with a bench grinder and allowed them to get too hot. They were work hardened to hell and would laugh at any attempt to drill much less tap. Either quench frequently when grinding or file by hand.

-fresh sharp cutting tools make a huge difference. I like TiNi coated drills from McMaster. As said when you drill get on and off quickly. Try to never let the drill rub, only cut. I’d start the drill press and plunge fast and hard. I’d only cut about 1/4” then withdrawal the drill quickly. I’d cool the rod with a wet rag. Again avoid heat / work hardening.

-As others have said look at a tap chart to determine the drill size to use but you can likely go up a size or two with no problem to the threads. It’ll make tapping easier.

-tap magic was my close friend

-I would not cut more than 1/4 turn at a time. Or even less. It takes time but you’ll break less taps. I honestly think breaking taps is just gonna happen when you’re dealing with such a tiny tap. Tapping is a pretty demanding task for tooling and without a decent size to the tap it’s gonna break sometimes. Alignment is key. I started mine in a drill press (your lathe is even better). Not power tapping but just turn the tap with a wrench and using the machine for lining it up. Once in a good ways I’d move to the vice to finish by hand

-starter taps cut gradually, help center itself (lathe setup kinda makes this irrelevant) and are best for your first pass. Bottoming taps should be used to follow up and get threads cut full depth to the bottom of the hole.

-I marked with a piece of tape around the tap to keep track of where I was depth wise to avoid hitting the bottom of the hole.