Tips for drilling holes in stainless

[Charlyipad]

I need to make some big washers for my rudder posts. I have some 316 stainless that is 3/16 inch thick, and a drill press.

Sheesh. I need a two inch ID hole, that needs to be fairly accurate the OD doesn't,t matter as much. Not much success so far. I have spent over an hour and still am only about half way through the plate. I am using one of those dewalt hole saw bits with a quarter inch pilot. it has worked fine for aluminum but this stuff is a different story. I have oiled and oiled. it gets hot quick. I changed bits to one of those of the same type like Lowe,s sells. No Luck. is there a different bit I should be using? is there some kind of abrasive or something that would help? Any other tips? Thanks!

 

[yofish]

http://www.practicalmachinist.com/vb/search.php?searchid=4019207

The Russian boat builders around here do what you are doing with the part and cutter submerged in a pan of water.

 

[KnottyBuoyz]

I think the trick with stainless is to go slow. Adjust the belts on your drill press for the slowest speed. Try that. If not I'd look in the phone book (or Google for you younger folk) for a shop that can waterjet the part for you.

 

[Nick.K]

I have a friend in his seventies who has built many small steel boats. When he needs a large round hole in heavy plate he goes to his local scrap yard to look for a hole which he cuts around and welds in to his structure.

 

[AndySGray]

... goes to his local scrap yard to look for a hole which he cuts around and welds in to his structure.

This is not a common technique and for good reason - welding holes in place is extremely difficult and requires perfect technique by an experienced welder - the base metal must be very clean. If the weld fails and the hole falls out and lands below the waterline the consequences are dire.


Thank you Nick, brilliant post - keep up the good work

 

[waikikin]

Charly,
when I've done rings like that, & I'm assuming that they're the thrust rings that the weight of the rudder transmits to a top hat bearing at /under the tiller head, I've put the metal in a lathe, punched a drill through the plate with the tailstock & then skimmed out the hole to size with a cutting tool. If you dont have access to a lathe find a machine shop or some one who works in one... that might like to do a small foreign order over lunch....

Also it's possible to buy off the shelf flanges typical for pipe joining work & you can get them without holes in, could offer a head start on making
Here's a typical catalog.. http://stirlingsaustralia.com.au/ap...steel/flanges/352-poly-pipe-backing-ring.html

Jeff.

PS: a mate was making lots of cross bollards in staino, he invested in some tipped hole saws that cut heaps of holes, used some soluable oil flow too i think.

 

[Charlyipad]

Thanks guys, Monday I will check out some local macine shops. it can,t be that hard to find someone to do it, and probably will be the lest xpensive route for such a small quantity.

 

[Charlyipad]

hey I just thought oF something else... if I drill a pilot hole in a small piece of plate and chuck it into my Milwaukee hole hawg, I would have a slow turning lathe. so what would make a good homeade cutting tool ??

 

[AndySGray]

Are you welding these to the hull?

If not you may be able to source Bronze ones off the shelf, which will cost less than machining 316 ones?

 

[Charlyipad]

bronze would work. I looked around for stainless and couldn't,t find any that size, and since I already had the plate...

 

[cgoodwin]

Plasma cut

 

[JRD]

Plasma cut

True, though laser cutting has all but replaced plasma for thin gauge stainless work in NZ. Laser cutting tends to transfer less heat to the metal, causes less distortion for small gauge and requires less cleanup. When you get above 12 mm (1/2") plasma starts to come into its own.

It is quite accessible and affordable here in NZ and I assume the situation is similar elsewhere. You can send dxf files for whatever shapes you want.

If you stick with a hole saw make sure its sharp and you use a good cutting oil and as started above make it real slow, you would want to be less than 100rpm. Most small general purpose drill presses are way too fast. Think of the tip speed at the circumference, at the same RPM your 2" hole saw is trying to cut the metal 10 times faster than a 1/4" drill bit and its just skidding over the surface work hardening it and making it hot.

For smaller holes in 316 a cobalt drill bit is the ducks nuts. They cost a lot more, but last a heap longer and slice through it like cheese. The only rule is never let anyone borrow it as you will never get it back

 

[Kevin Morin]

RotoBroach bits

Charlyipad
not sure if your drill press will take the torque required of one of these bits but they do cut very nice, high quality holes. In SS you'd need to use that alloys cutting solution to avoid gauling up, http://www.schaefferoil.com/synkool-lubricant.html but if you can turn them slow and with adequate power not to chatter, they cut or machine a nice bore.

http://www.amazon.com/Blair-CUTTER-...=2025&creative=165953&creativeASIN=B00063VUX2

This link is not the brand I'm using, I use the Hougen brand bits and mag drill but the type is the same. I've only done holes up to 1-1/2" and the ss wasn't 0.187" only 0.125" but they came out like I'd had the pieces turned on a lathe.

Cheers,
Kevin Morin
Kenai, AK

 

[MikeJohns]

I need to make some big washers for my rudder posts. I have some 316 stainless that is 3/16 inch thick, and a drill press...............

You probably have HSS cutters and burned the tips off in the first 30 seconds.

Use a carbide tipped hole saw in 3/16 . That's probably what Kevin's cutter is ?? (For thin sheet SS work use a carbide grit ).

As everyone has said get the speed down and use water or cutting fluid to keep the heat off water works fine. Pre-drilling a hole in the waste material at the cut line to allow the swarf to drop out helps a lot too.

 

[essenmein]

Maybe not the cheapest, but handy for one offs etc delivered to your door:
http://www.emachineshop.com/