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Drilling 5/16" holes in 4130 steel tube - jamming/binding issues

skiffe

Plastic
Joined
Feb 17, 2013
Location
Atlanta
I have been drilling 5/16" holes in 4130 steel tube (1/16" wall) for many years with HSS bits and a Harbor Freight drill press set at 920 RPM. There has been occasional binding, but nothing to problematic. Now, however, even brand new bits are binding when it punches through every time. I've tried cutting oil, and other speeds (though I'm open to speed suggestions). I cannot figure out what is suddenly different about my setup/technique that is causing the binding. I feed slowly (but not too slow), and back out to clear debris (though I didn't need to back out in the past). The belts aren't slipping. I've also tried a new parabolic bit without success, as well as a few different bit coatings.

I'm open to anything, including buying a nicer drill press (though the Harbor Freight drill press has been a workhorse for many years). This is a big part of my livelihood and I do have a self-imposed deadline (creating new stock before I run out of old stock). I'm at wits end and much appreciate any ideas. Thanks!
 
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surplusjohn

Diamond
Joined
Apr 11, 2002
Location
Syracuse, NY USA
I have been drilling 5/16" holes in 4130 steel tube (1/16" wall) for many years with HSS bits and a Harbor Freight drill press set at 920 RPM. There has been occasional binding, but nothing to problematic. Now, however, even brand new bits are binding when it punches through every time. I've tried cutting oil, and other speeds (though I'm open to speed suggestions). I cannot figure out what is suddenly different about my setup/technique that is causing the binding. I feed slowly (but not too slow), and back out to clear debris (though I didn't need to back out in the past). The belts aren't slipping. I've also tried a new parabolic bit without success, as well as a few different bit coatings.

I'm open to anything, including buying a nicer drill press (though the Harbor Freight drill press has been a workhorse for many years). This is a big part of my livelihood and I do have a self-imposed deadline (creating new stock before I run out of old stock). I'm at wits end and much appreciate any ideas. Thanks!
By binding. Do you mean you are stalling the drill press? Is the motor stalling or maybe the belt is slipping on the pulleys? If the belt is slippin you may need a new belt or it needs cleaning and or tightening or some belt dressing.
 

kenton

Hot Rolled
Joined
Dec 15, 2015
What happens when the drill "binds"? Does it break?
Have you recently changed drill brands?
Have you tried drilling some of your old stock to see if the drill "binds"? If it doesn't then you might have a material issue.
What is your fixturing to hold your pipe? Has it recently changed or started to wear out allowing the material to shift and "bind" when the drill break through?
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
Are the drills dulled during this process? I would drop that RPM down some. Got something closer to 615? Next you need to identify where the slippage is occurring. Try that and report back.
 

FamilyTradition

Aluminum
Joined
Feb 24, 2018
Location
Greenfield, Mass
When was the last time you put a new drill chuck on/replaced the jaws (if your chuck is equipped to do so)? If the belt isn't slipping I would say your chuck is worn and not gripping the drill properly anymore.

When the drill breaks through is when it experiences the most force, as it is trying to push through that last bit of paper-thin material.

If you opt to get a new chuck, I would definitely look at one with diamond -impregnated jaws. More expensive, but will dig in if the drill tries to slip.
 

skiffe

Plastic
Joined
Feb 17, 2013
Location
Atlanta
By binding. Do you mean you are stalling the drill press? Is the motor stalling or maybe the belt is slipping on the pulleys? If the belt is slippin you may need a new belt or it needs cleaning and or tightening or some belt dressing.
The bit jams in the tubing and stops the chuck/spindle/motor. The belt isn't slipping.
 

skiffe

Plastic
Joined
Feb 17, 2013
Location
Atlanta
What happens when the drill "binds"? Does it break?
Have you recently changed drill brands?
Have you tried drilling some of your old stock to see if the drill "binds"? If it doesn't then you might have a material issue.
What is your fixturing to hold your pipe? Has it recently changed or started to wear out allowing the material to shift and "bind" when the drill break through?
When it binds (jams), the bit/chuck/spindle/motor stops. Nothing breaks. Same drill brand, same stock - but maybe a new bit brand now that I think of it which is a huge possibility. The tubing is clamped down in a self centering jig and doesn't move. I'll try my older bits in case it is a new brand - thanks.
 

skiffe

Plastic
Joined
Feb 17, 2013
Location
Atlanta
Are the drills dulled during this process? I would drop that RPM down some. Got something closer to 615? Next you need to identify where the slippage is occurring. Try that and report back.
I tried dropping the RPM without success, but will gladly try again. There is no slippage, it jams and the bit/chuck/spindle/motor stops turning. Nothing is dulled.
 

eKretz

Diamond; Mod Squad
Joined
Mar 27, 2005
Location
Northwest Indiana, USA
I tried dropping the RPM without success, but will gladly try again. There is no slippage, it jams and the bit/chuck/spindle/motor stops turning. Nothing is dulled.

That is a different matter. It sounds like you're losing your drive (sheared pulley drive key? Probably not if the motor is stopping) or that your drive motor is toast.
 

kenton

Hot Rolled
Joined
Dec 15, 2015
I agree, it sounds like your drill press is crapping out. You could try reducing your feed pressure as the drill breaks through to try to keep the drill from grabbing. You could also try dubbing your drills to keep the drill from sucking in as you break through.

I think the main solution is to get a different drill press. You might start looking for a used industrial machine instead of replacing with another cheap import machine. There look to be some decent options on New York City's Craigslist.
 

FamilyTradition

Aluminum
Joined
Feb 24, 2018
Location
Greenfield, Mass
I didn't realize it was stalling the motor as well - I agree that you may want to look into a better drill press. As kenton pointed out, plenty of good used ones for cheap.
 

RODELU

Aluminum
Joined
Dec 31, 2010
Location
Uruguay
There´s an area behind the edge in twist drills that can be at different angles; the bigger that angle, the more aggressive and more "digging" the drill will be; making that angle as close to zero as practical might help. You don't need to grind the whole area, grinding a facet behind the edge should be enough.
Mntndew asked about the angle in the cutting edges, (118 deg. is most commonly used) I wouldn´t know about that but making that angle the ideal one might also help.
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
What is most likely happening is the drill press spindle is falling down when the drill is almost finished breaking through. This is a result of to much backlash between the rack and pinion. The best solution is a better drill press. A bodge might be to either weight the spindle enough to drill on its own, or a heavy spring return on the spindle itself, not through the rack.

You can test this idea by tightening the quill lock sufficiently the spindle moves rather stiffly.
 

4GSR

Diamond
Joined
Jan 25, 2005
Location
Victoria, Texas, USA
You might grind a slight flat on the face of the cutting edge as you would on a drill bit for cutting brass. The might reduce the chance of the cutting edge from digging in. I agree with every one else, get you a real drill press!!!
 

surplusjohn

Diamond
Joined
Apr 11, 2002
Location
Syracuse, NY USA
A better drill press is the answer but adding mass in the form of a flywheel is something to think about. Maybe find a heavy pulley or gear that can be added to the spindle
 








 
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