Taping A 6x32 Hole In Stainless Steel Round Rod Help

[gregg]

taping a 6x32 hole in Stainless Steel round rod. I'm breaking new taps left and right? 303 SS rod seen to cut well with a HHS lathe tool but hole drilling and tapping is not going well. Should I be using different SS or different tooling? Want to do a order for more SS round rod but will wait see what you all have to say.
Thank You for your help ahead of time

 

[Franko]

You might try a slightly larger drill bit for the hole.

 

[kd4gij]

Did you use plinty of coolant when you drilled the hole? 303 and most ss will work harden quick when drilling.

 

[ScrapMetal]

What kind of taps are you using? I've found there is a huge difference between a quality tap and the ones you get from the hardware stores.

-Ron

 

[Doubleeboy]

Sharp drill, like said above don't go for 75% thread, maybe 60% or a bit less. Peck at the hole but dont be shy once the bit starts cutting. I only dwell long enough to start pulling a chip then put some pressure on the feed handle, if it starts cutting easy, go for it, if not peck. Practice in scrap till you get the hang of it. Even cheap import HSS taps from Enco are better than the stuff they sell at hardware store, those hardware store taps are barely usable for retapping a hole and worthless for tapping a new hole for 75% thread. I was told when I was young that 6-32 was a weak screw for some reason and that going to fine thread in that size was a better call or go up to an 8. I don't remember why but the chap who told me ran a 50 man shop for decades so must have known a thing or three.

michael

 

[RJSakowski]

6-32 taps are particularly fragile. I should know, I broke two of them in work myself in the past month. Are you tapping the end of the rod or cross drilling and tapping? If end tapping, I would use a lathe and support the tap wrench with the tail stock center. As said above, use a fresh good quality tap and cutting oil. Lock the headstock and carefully turn the tap wrench, advancing the tailstock as you go. If you have a spring loaded tap guide it makes the job easier. Watch the tap as you work. If you see it twisting, back it off. Clean any chips, relube, and continue. So and steady! If a blind hole be careful as you reach the bottom. Something has to give and it is usually the tap. USE A TAPER TAP! I run the taper tap first and follow with the plug tap and finally the bottoming tap if necessary. If your drill depth is deep enough to provide clearance for the taper tap for the desired thread depth, you can forgo the latter two provided you have enough thread depth. If you are cross drilling and tapping, use a Vee block. center the drill in the bottom of the vee and clamp the block to the table. Place the rod in position and clamp it as well. Drill your tap hole and without removing the rod put a tap guide in the chuck and as as for end tapping.

 

[randyc]

I've not machined stainless regularly in a while but for 10XX series carbon steel I like spiral fluted taps a lot better than the normal straight flutes. RJSakowski suggested using successive taps, from taper to bottoming and that's about the safest way to go, IMO.

And as noted by Scrapmetal, work-hardening is common with this alloy and you must be more aggressive with feeds when turning and drilling to prevent it. Make sure that your drills have a nice, sharp edge - a dull edge will set you up for failure. Same thing applies to taps ... a well-used tap works fine on non-ferrous family perhaps but for 303 ? NOT - use a sharp, new tap if possible

The worst sound you can hear is a "squeal" when drilling 303 !

 

[Lucky 13]

I have tapped thousands of 6-32s in 303 rod .500"+ deep manually, power tapping full depth in one shot. I use a .125 drill, a Balax or OSG brand GH3 roll form tap and Rapid Tap or Moly Dee cutting oil. Form taps are much stronger than fluted cut taps and produce no chips. I almost never use cut taps in stainless. 303 in my opinion is very easy to machine (like 1018 but better finish). I typically machine 316 or 304 SS everyday.

 

[chips&more]

You did not say what kind of tap you are using? I would strongly suggest a gun tap. And I would suggest all your taps be gun taps. Use plenty of cutting fluid. Keep a constant tool pressure, do not let the cutting action stop or you could easy work harden SS…Good Luck, Dave.

 

[Lucky 13]

303 is free machining and does not work harden like other types of stainless. I would rather machine 1,000 lbs of 303 to 1 pound of 304. 304 work hardens if you look at it wrong.