Recommended RPM for 5/16” solid carbide drill in 304 SS?

[aliva]

I've polished SS starting with 120 grit working my way up 400.Then onto a buffer wheel on the pedestal grinder using red Jewlers rouge, next, green buffing compound for SS. The finish was like a mirror.

 

[Skippy]

I've polished SS starting with 120 grit working my way up 400.Then onto a buffer wheel on the pedestal grinder using red Jewlers rouge, next, green buffing compound for SS. The finish was like a mirror.

After polishing seal with Shark Hide. I used it on my aluminum trailer and it has held up well. Available at Amazon.

 

[stupoty]

If you want a specific kind of finish you can buy abrasive sets, they are good to look at for ideas of how to finish for different levels of buffing.

Gives you the steps to work in for different outcomes of shine , lot of us probably have the elements of the kits hanging about

for example.

Fein WSG17-70 Satin Finishing Kit - Protrade

Fein WSG17-70 Satin Finishing Kit - we stock a huge range of tools & consumables for professional trades. Free delivery on orders over £50!

www.protrade.co.uk

The buffing mops and some sort of paste / wax are very good for the mirror finish look.

Stu

 

[projectnut]

I think I'd use a water based coolant to keep the hear down, or perhaps TapMagic, I second or third the motion about using a split point cobalt drill and no pecking, which would invite work hardening.

The company I worked for made most of its own food processing and packaging machines. The go to materials were primarily 316 stainless and 6061 aluminum. The machine shop foreman was too cheap to buy carbide drills, so everyone used either standard HSS split points or those with some cobalt. TapMagic was the preferred coolant with speeds in the 200 to 300 rpm range and lots of down pressure.

 

[Shotgun]

My understanding is that stainless doesn't work harden as much as the newly exposed chrome oxidizes. The chrome isn't so hard until it oxidizes. but it then forms an extremely hard but thin barrier. You want the leading cutting edge of the bit to get under that oxidized layer, and stay under it. It is better to go one IPM and have a single curly piece of swarf than to try to get sixes out of stainless.

But, I could be wrong.

 

[Huub Buis]

I have well over 100 holes yet to drill in .125” 304 stainless. I am using 5/16” solid carbide drills. Machine is a 3HP, 3 phase knee mill. I am liberally using dark thread cutting oil on both the work & drill. I peck and I do not get aggressive.

What worked best for me was 1000 RPM with a hand feed, using the quill. The only problem is that the drills aren’t lasting as long as I would like.

I give the drill *a lot* of time to cool. One has to do this in this case; I was really surprised how hot the drill was getting.

I know that stainless work hardens.

These are brackets to connect hardwood fence slats to hardwood 4” X 4” posts in the ground.

View attachment 423757

From what I have read on other forums, for drilling and tapping in stainless you need a special tapping/drilling fluid. These are quit expensive but really saves your drills and taps. "Tap Magic" is the only fluid I know off but there are others.
304 is work hardening so don't be gentle, don't rub but make chips.

A link to feeds and speed: https://www.tru-edge.com/wp-content/uploads/2019/11/Feeds-and-Speeds-Drills.pdf

 

[tq60]

Stainless hates heat.

So get a strong. Short drill.

Also get a good center punch with a good hammer, heavier is better with solid bench or concrete floor.

Scribe mark then solid whack of hammer to get a good dimple.

Shorter drill but can take higher pressure.

Speed creates heat so the trick is a slow speed with high pressure, experiment, you can place a vise on the table to hold the stock, put a lot of weight on the feed with slow speed.

Correct combination will result in the drill peeling through and not getting hot.

Do not Peck, one pass.

A squirt of atf or other oil helps.

Yes, there will be a nasty burr on back side.

A step drill at slower speed cleans them up, they are self piloting but most folks are too fast and ruin them.

Only needs to remove a burr so the harbor freight 1/4 hex drive in an impact driver pulsing trigger to just wipe off the burr will last.

Sent from my SM-G781V using Tapatalk

 

[erikmannie]

Thank you everybody for all the very helpful tips. I work long hours at my day job M-F, but I will be drilling all of the holes this weekend.

 

[pontiac428]

Why would you want to put a protective coating over polished stainless steel? First, it's polished stainless steel, it doesn't need protecting. Second, and perhaps important, is clear coatings filter light and alter the natural luster of the metal. It will cut the specular radiance and make the part look plastic. Something to think about while you're out earning bread for the week.

 

[Aukai]

In my climate, and salt atmosphere SS does dull, the ShineSeal (formerly ZoopSeal) I have been using SO FAR has not changed the surface it is protecting, and does not mask the metal shine. These pictures are of aluminum as machined no further polishing other than the aluminum polish applied with a cloth, and buffed. One is direct light the other is indirect lighting, and flash. The sealer is not visible, has not changed the shine, at least to me anyway.