Having Trouble with Drilling, stabbing Stainless 420

[Chrisg84]

I am having trouble on this 420 material. First of all I didn't have a carbide drill. Finished hole is like .124" I am using an hhs #3 center drill then a .104 drill hhs then a carbide stabber with a radius that is like .117" in diamter. I might of had some other issues going on besides feeds and speeds but when I got to the stabber and it broke. I am not at work right now. But if you have experience with situations like this it would be great. I am going like .300 to .400 deep. For the carbide stabber what rpm would you use and feed and would you g81 it or peck it and would you use full retract. The hole is being spotted before the drill .
What rpm would you use for the HHS Drill that is .104 in diameter? on my FS wizard app its gives me two options .
(moderately difficult stainless steels ) 135-325 HB)
RPM 1030 F1.43
(free cutting stainless steels (135-375HB)
RPM 2354 F 3.6
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I think originally the RPM in the program was around 3 or 4 thousand something with a feed of 8.

Hopefully I might get a carbide drill but dont want it to break. I don't have extra stock to have drills breaking. Even though the part is just a 1" square block basically. If you have recommendations for rpm and feed of a .104 carbide drill as well that would be greatly appreciated.

 

[implmex]

Hi Chrisg84:
I'm unfamiliar with your terminology.
What's a "stabber"?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[Booze Daily]

Plunging with an endmill?

 

[Milland]

Given the numbers involved I would guess he means "reamer". But I'd use a touch bigger drill to establish the hole, leave .005"/side for the reamer.

Hmm - "carbide stabber with a radius that is like .117" in diamter", sorta confusing. A countersink? But then why not take it to a touch over .124?

Or maybe it is a stabber - I've never used a dagger when machining, but hey, always something new to learn...

 

[JasHarvey]

I'd go as big as you can get away with with your pilot hole. Then take it easy on the carbide drill or whatever it is. I like two flute straight flute drills when drilling with carbide. The helical carbide drills break much easier. I'd definitely peck everything except maybe the center drill. If your center drill is dull it will work harden the material so use a sharp center drill. I use 50 SFM with HSS in stainless and 85 SFM with carbide. Peck maybe .030 at a time with the carbide and maybe a little more with the HSS drill. I always start at 80% feed rate when testing a new program. You can kick it up as you see fit. Hope that helps.

 

[Chrisg84]

Plunging with an endmill?

Yes so at our shop we drill with a drill but plunge with and endmill in between to make sure hole is straight and like 5 or ten thou under what the reamer is going to do. Never did this at other shops. I guess it helps the hole be that much more straight. because reamers can follow a crooked hole.

 

[Chrisg84]

Yes so at our shop we drill with a drill but plunge with and endmill in between to make sure hole is straight and like 5 or ten thou under what the reamer is going to do. Never did this at other shops. I guess it helps the hole be that much more straight. because reamers can follow a crooked hole.

I'd go as big as you can get away with with your pilot hole. Then take it easy on the carbide drill or whatever it is. I like two flute straight flute drills when drilling with carbide. The helical carbide drills break much easier. I'd definitely peck everything except maybe the center drill. If your center drill is dull it will work harden the material so use a sharp center drill. I use 50 SFM with HSS in stainless and 85 SFM with carbide. Peck maybe .030 at a time with the carbide and maybe a little more with the HSS drill. I always start at 80% feed rate when testing a new program. You can kick it up as you see fit. Hope that helps.

Given the numbers involved I would guess he means "reamer". But I'd use a touch bigger drill to establish the hole, leave .005"/side for the reamer.

Hmm - "carbide stabber with a radius that is like .117" in diamter", sorta confusing. A countersink? But then why not take it to a touch over .124?

Or maybe it is a stabber - I've never used a dagger when machining, but hey, always something new to learn...

the stabber is a .117 carbide endmill, so like a drill to bring it up closer to size but to make the hole straighter.