Drill holes in stainless tube


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Old 04-01-15, 01:59 AM
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Drill holes in stainless tube

Hi,

I'm doing a Half-pipe / skate ramp. I have to drill holes in a stainless tube but I wasn't able to with HSS Drill tips last night (I've followed youtube video tutorials). The stainless tube is this one: Stainless Steel T304 Tube Multiple Sizes and Lengths For Exhaust, Tube Repair | eBay

Today I'm thinking about picking new drill tips ( Erbauer HSS Drill Bit Set 13 Pieces | HSS Drill Bit Sets | Screwfix.com ), but not sure if this will work ?

Can someone experienced give me some advice ? I'm using a driller ( Energer ENB463DRL 710W Percussion Drill 230-240V | Percussion Drills | Screwfix.com ) and I also have a screw driver ( Titan TTD272DDH 14.4V 1.5Ah Ni-Cd Cordless Drill Driver | Cordless Drill Drivers | Screwfix.com ).

The steps: Lubricate, do it slowly, etc.
 
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Old 04-01-15, 04:23 AM
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Welcome to the forums!

Not all of your links work so I'm not sure what you are using but when I drill stainless, I like to use cobalt bits and even then if you are drilling a lot of holes you may need to sharpen or replace the bit before you are done. To drill round pipe you need to have it clamped down and use a drill press.
 
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Old 04-01-15, 04:55 AM
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As Mark said, round pipes will be difficult to get started, so a drill press would help. If you are using, say 1/4" drill bits, you could use a grinder to create a small flat spot.

Let us know if getting started is your issue, or if once started it still won't drill through. And what is the wall thickness of the SS pipe?

Now, drill bits need to be configured for the material they will be cutting. There is a lead and tail differential (I'm sure those are not the correct terms) on each cutting edge and the angle between them is set to take out a specific thickness of material. If you have ever worked on a drill press you have probably seen a continuous spiral of cut material coming out as the drill advances downward. The thickness if that spiral is determined by the above differential and for SS it needs to be rather thin. Drill bits will often be sold with a universal setting more for softer materials up to mild steel. But when you get into very hard materials, you will do better with a drill bit pitched specifically for that material.

Now, I'm not the machinist, he was a very good friend of mine and would quickly re-grind my bits as needed. The above explanation is what he told me 45 years ago when I was trying to drill a piece of SS. Once he changed the pitch and added a little lubricating oil, out came a perfect spiral and all of the holes were simple.

You may also have to start with a smaller drill bit to create a pilot hole. If you look at a 1/4" bit, there is a flat space across the end between the two cutting edges. A pilot hole that diameter will allow the cutting edges to bite into the material instead of trying to force in the flat spot, which works on soft materials but won't on hard materials.

I have never looked to see if I could buy a drill bit specifically for SS as that old friend taught me how to re-grind mine as needs, but in today's internet world i would guess something should be available.

PS, the drill press and clamping of the pipe holds everything secure so you can get that spiral going and keep it all the way through. The slightest wiggle and it breaks off and has to restart by digging in over and over.

Sorry for the long winded,
Bud
 
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Old 04-01-15, 05:08 AM
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The correct drill bits help but it can be done with average HSS bits if they are sharp.

1. Make a dimple on the tube with a punch and hammer where you want to drill. This will help prevent the drill bit from walking off.

2. Start with a small pilot bit about 1/8". Put a drop of oil on the dimple you made to lubricate and cool the drill. Push hard and turn the drill at a medium speed. If you get two continuous strips of metal coming off the bit you are getting the pressure and speed right.

3. Then move up another size in drill bits to 3/16" or 1/4". Put some oil around the hole and drill with your next larger size. Keep repeating until you get to the size hole you want stepping up about 1/8" each time. As you move up to larger bits turn the drill slower and press harder and don't forget to keep the bit lubricated. For larger holes you may have to stop and dip the tip of the drill in some oil. If you hear a screeching, or fast "tick, tick, tick" or clicking sort of sound stop right away and apply more oil and try going down a drill size and try again.
 
 

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