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Tooling to reliably drill Tubing

DethloffMfg

Cast Iron
Joined
Sep 22, 2018
Location
Portland, OR
I have a family of parts that I am moving from hand drilling into the CNC now that I have one. This is saving me a ton of time but I need to figure out reliable tooling to drill the holes all the way through both sides of the tubing in one setup. I have about 500 holes at a time to put through DOM tubing.

Hole diameter is 7/16", tubing is 1.5"x.095" and 1.25"x.120".

Right now I am using one of the Maritool reduced neck endmills because I had it on hand. It works but it really sucks, I'm at 6 minutes for 4 holes doing a helical interpolation, any faster and it starts getting unhappy quick. I am going to get new tooling to do this and want to get the right choice. I am thinking of using a regular drill around 3/8" diameter to punch all the way through, then using the long end mill to open the bores up. That should speed things way up and take care of the drill burr inside.

I've also looked at flat-bottom drills as those seem ideal for the top hole on the tube, but I'm concerned with process reliability once it gets to that bottom hole. Is the thin 'plug' that drops through the drilled hole going to be an issue when the drill gets down to the second hole?

I want process reliability more than anything.
Flat bottom drills?
Annular cutters?
Plunge with end mill?
Keep the helical interpolation with endmill?
Drill with normal drill and then clean up with an end mill?
 
The best way is to do it on a 4th axis,but since you don't have one, if you want a procedure that is bulletproof, then I suggest drilling the 1st hole, then switching to an extended center drill or extended spot drill for the 2nd hole and then back to the drill to continue the hole thru.
In other words:
c/drill or spot drill the 1st hole
drill
c/drill or spot drill the 2nd hole
drill thru
 
I think the tube is flat enough that a drill could do it ok. I really dig that burraway, I’ve got a few applications for that. Thank you for sharing that!

I think the burraway is too long for the tube jaws I have (looks like it needs a lot of clearance under the tube) so I might just use a 7/16” drill and then touch another .010” off with an end mill
 
Someone gave me a set of the Cogsdill tools. I wasn’t overly impressed.
They might be ok for a small edge break on a sharp edge, but I don’t see them chamfering the burr left from drilling thru steel tube.

It might be faster interpolating a chamfer with a 90 deg. double angle cutter necked down far enough to reach to the far side.
 
Standard drill and long-hand the code so you drill in, rapid down, drill, rapid out. Any good quality drill won't need a spot.

Then run a Burraway from Cogsdill through and you're golden. Should be quite fast.

This is what we don on some Ø1.25 x .125w DOM
Drill through with a screw machine length drill, and chamfer OD/ID with a Burr-away (cogsdill) tool.
We hand coded it to drill through side 1, rapid to within .05" of the bottom (ID) and G01 through the bottom.
This is a low quantity run for us though.

If I had your quantity of holes, I would look for a coolant fed, 5X Dia, Ø7/16, carbide drill.
Follow that with a burr-away.
No spot, no muss, no fuss.

The ONLY drawback I can think of is the thin wall. Carbide might not like the low penetration feeds that thin wall tubing will stand up too.
Drilling through 0.095" wall, is the work of a sheet-metal drill (custom grind on end)

Doug.
 
I'd go with an inexpensive carbide drill, and program long-hand like others have mentioned. A Walter DC-150 drill would be a good place to start. Inexpensive, and should perform well. Your Walter rep could probable suggest one of their other 500-drill lines as well.
 
7/16” rotabroach with the spring loaded pilot pin on an extended arbor. The pilot pin will pop the core from the first cut off the tool and clear the second one as well. Nice clean hole faster than a twist drill, very little burr. Like a round cold saw.
 
7/16” rotabroach with the spring loaded pilot pin on an extended arbor. The pilot pin will pop the core from the first cut off the tool and clear the second one as well. Nice clean hole faster than a twist drill, very little burr. Like a round cold saw.
I’ve considered this except that method worries me for reliability in a CNC. Those plugs could either not eject, or could drop right in the way of the lower hole. Both of those scenarios could destroy the tool if not more. I’d rather make chips than slugs unless I’m positive the slug won’t be an issue.

helical bore it with a high speed/feed endmill..

Thought about that, do you know where to get one that meets those dimensions? I’d want it to be 1/4” or 5/16” and it would need to reach down 1.5”. Jabro? Garr?
 
This is what we don on some Ø1.25 x .125w DOM
Drill through with a screw machine length drill, and chamfer OD/ID with a Burr-away (cogsdill) tool.
We hand coded it to drill through side 1, rapid to within .05" of the bottom (ID) and G01 through the bottom.
This is a low quantity run for us though.

If I had your quantity of holes, I would look for a coolant fed, 5X Dia, Ø7/16, carbide drill.
Follow that with a burr-away.
No spot, no muss, no fuss.

The ONLY drawback I can think of is the thin wall. Carbide might not like the low penetration feeds that thin wall tubing will stand up too.
Drilling through 0.095" wall, is the work of a sheet-metal drill (custom grind on end)

Doug.

Yeah I’m leaning towards this method. I don’t have TSC coolant and I want to stay away from using coolant on these (some of the stick 4’ out of the machine and go to welding).

Would a cobalt drill handle the thin wall better than carbide?

Or drop the coin on a flat bottom drill and just go for it?
 
7/16” rotabroach with the spring loaded pilot pin on an extended arbor. The pilot pin will pop the core from the first cut off the tool and clear the second one as well. Nice clean hole faster than a twist drill, very little burr. Like a round cold saw.

Years ago I made sample tubes of 2" x .062 wall tubing. I used a 2 flute cuter made by Jancy Engineering. It had a spring loaded pilot similar to an annular cutter. I never had a problem with the ejected disc fouling the tool when drilling through the second side. Unfortunately Jancy is no longer around or I would have recommended it. I say go with the annular cutter.

The Jancy cutter produced very little burr. I believe the same would be true of the annular cutter. I deburred with a Cogsdill tool.
 
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Thought about that, do you know where to get one that meets those dimensions? I’d want it to be 1/4” or 5/16” and it would need to reach down 1.5”. Jabro? Garr?

Mitsubishi solid carbide 6mm in stock with that much neck length. I run them in Titanium and get great life.
 
I’ve considered this except that method worries me for reliability in a CNC. Those plugs could either not eject, or could drop right in the way of the lower hole. Both of those scenarios could destroy the tool if not more. I’d rather make chips than slugs unless I’m positive the slug won’t be an issue.



Thought about that, do you know where to get one that meets those dimensions? I’d want it to be 1/4” or 5/16” and it would need to reach down 1.5”. Jabro? Garr?

We use a german company... Here is the link for them..
Metal Cutting Tools | WNT
 
I have another approach that I have used in volume production, you have a hollow plug that fits inside the tube with a pair of holes that line up with the holes in the tube. With a suitable bush in line with the top hole it is possible to drill through the top of the tube withou trouble, the lower hole in the plug becomes the drill bush for the second hole.
After drilling the plug can be withdrawn and the holes bought to size with a reamer, drill or endmill.
 








 
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