[sharkey]

If I get over 3/8 the holes are triangle shaped. I start with a very small pilot hole then step up ( using a drill press) then run into trouble over 3/8. The bits are old but seem to be cutting through the metal just fine. I'm holding the stock with my hands but maby need to secure it better on the plate. Not doing anything critical yet but would just like to make better holes. Suggestions please .


Sharkey!!!

 

[mouse_zzr600]

If I get over 3/8 the holes are triangle shaped. I start with a very small pilot hole then step up ( using a drill press) then run into trouble over 3/8. The bits are old but seem to be cutting through the metal just fine. I'm holding the stock with my hands but maby need to secure it better on the plate. Not doing anything critical yet but would just like to make better holes. Suggestions please .


Sharkey!!!

Gidday Sharkey,
Firstly:-
Some advise from a now wiser man whom will NEVER do it again, holding stock by hand is not a great idea and will eventually cause a major injury (I nearly lost 2 fingers because of it and the only thing that saved them was micro surgery) + it is not going to help as the stock can move.
Secondly:- Drill speed, To slow and the drill will not cut evenly, to fast and the drill will dull due to spinning and not cutting.
Thirdly:- drill bit angle (the cutting edge) needs to be correct for application.
Fourthly:- The pressure applied to the drill press forcing the bit through instead of letting the drill do the work.
Fifthly:- holding the work off centre will not help.
Hope these hints work for you. Take your time and let the drill and press do the work for you and please secure the work in a drill press vice........

 

[zookpr]

You also need to use a reamer if you want a round hole to size. Typically you can drill slightly undersize and finish ream. A real nice job can be obtained using a taper reamer. Also, as stated above the stock needs to be secure as well as a steady drill otherwise the drill bit is going to walk all around.

 

[astroracer]

^^^^Ditto^^^^ On all of the above! Another option to look into are the "step drills". They do a very good job in thin stock. Much better at making round holes in sheet metal then a standard twist drill.
Mark

 

[Old Buzzard]

Either..

Uni bits, or Lawson thin material bits. [Dewalt has a version of the Lawson, too.] Got mine ay Lowes.

They have a small bit in the center, and a outer cutting edge that works like a hole saw. It cuts a rd hole from the od inward.

 

[oldtruckwelder]

Gidday Sharkey,
Firstly:-
Some advise from a now wiser man whom will NEVER do it again, holding stock by hand is not a great idea and will eventually cause a major injury (I nearly lost 2 fingers because of it and the only thing that saved them was micro surgery) + it is not going to help as the stock can move.
Secondly:- Drill speed, To slow and the drill will not cut evenly, to fast and the drill will dull due to spinning and not cutting.
Thirdly:- drill bit angle (the cutting edge) needs to be correct for application.
Fourthly:- The pressure applied to the drill press forcing the bit through instead of letting the drill do the work.
Fifthly:- holding the work off centre will not help.
Hope these hints work for you. Take your time and let the drill and press do the work for you and please secure the work in a drill press vice........

Ditto on all said here, the older I get realize how many shortcuts on safety that I have taken and lucky to all fingers and eyes, slow down and take time to do it safely -- NUff said, have a great day. :shakehands:

 

[Rick_L]

Standard drill bits make a triangular hole in sheet metal - that's just the way things are.

As said, special bits for sheet metal make round holes if that's what you want and need.

Or you can punch the holes. You can use a "Greenlee punch" for this. Electricians use them.

 

[Churchkey]

Old drill bits are ok if they are sharpened properly. The lip clearance angle &
the chisel edge angle must be identical on both flutes. If they are not identical the bore will be out of round. The shank must be true, if the bit has spun in the chuck that bit is toast. Check the spindle on the press if it has lateral movement it will need new bushings/bearings.

Suggest investing in a set of titanium nitride bits. HF has a set of SAE to 1/2"
for 30 bux. A full set including letter & number bits cost less than 60 bux.


Make yourself some "T" bolts to fit the slots in the drill table + tabs & nuts to lock the work.

Good luck.

 

[sharkey]

Thanks for tips I can use them. First I will secure my material, then buy some drill bits, slow my drill press down and try again. They don,t need to perfect but better than they are. They look like a kid drilled then, and I sure am not a kid. thanks.


Sharkey.

 

[Restorit]

Hey Sharkey.....a friend of mine who is a pattern maker always taught me to clamp everything down!! just like everyone has said, then.....if you are drilling through sheet metal on a drill press, to put some aluminum stock (or other softer metal) underneath it....it helps prevent the bit from grabbing the edges of the metal as it tries to push through the last couple thousandths of an inch....making a smoother cut and far less burrs....if any....and reducing the triangulated effect. Even when they drill through wood in their shop, there is always other wood stock underneath it to prevent all the splinters as the bit exits the other side. It works for me.......just my two cents that were passed on to me.....hope it helps.
Eugene

 

[wagzilla]

only thing I can add is center punch and and cutting oil and safety glasses.

James

 

[sharkey]

Restorit! Good 2 cents worth. I think I heard that from way back but had forgotten about it. Thanks.

Sharkey!!!

 

[Restorit]

Restorit! Good 2 cents worth. I think I heard that from way back but had forgotten about it. Thanks.

Sharkey!!!

Hope it all works out for you..........good luck with the project.

 

[fiftyfive210]

I was always confused by the triangular hole made by a round bit also. Just a thought...maybe triangular shaped bits would make a round hole...hmmmm :confused0006:

 

[mickeywestsr]

Hoss, you are wise to start clamping your piece down & using a reamer is also wise. ... :tu
Cowboy :flag6:
:gba:
bowtie-trifive

 

[John McGraw]

All 2 flute drill bits will make a triangular hole, it is just the nature of the beast! Just get a Unibit step-bit from your local Home Depot, and you will have round holes. The unibit is the only tool to use in sheetmetal, as it will not grab the hole like a regular brill bit. One of the greatest inventions ever!:sign0020:


Regards, John McGraw

 

[moses]

2 flutes= triangles 3 flute bits and reamers =round holes

 

[56owner]

Drills

Uni bits, or Lawson thin material bits. [Dewalt has a version of the Lawson, too.] Got mine ay Lowes.

They have a small bit in the center, and a outer cutting edge that works like a hole saw. It cuts a rd hole from the od inward.

Where I worked they called these single sheet drills.

 

[Rick_L]

Where I worked they called these single sheet drills.

They work very nice but not many places sell them. Even some of the machine shop supply houses don't have them.

For the home shop, step drills are a better investment and work just as well.

 

[John McGraw]

Another little tip if you are going to buy a step drill. spend a few extra dollars and get a Cobalt bit rather than a standard high speed steel one. Lowes (about the lowest price on quality step drills) has a Irwin #4 in HSS for $36, and is only $42 for Cobalt. The Cobalt bit will outlast the HSS one by at least a 3X factor, so it makes it an incredible value. I had to replace my #4 bit this week, and it is over 7 years old. I have used it steadily for all this time, so it has served me well. If you are ever going to use it on stainless, a Cobalt bit is almost a requirement.

Of course, I feel the same way about conventional twist bits as well. Cobalt is worth the additional price, if you shop around a little. Even though I have a Drill Doctor, it is still a pain to have to stop and sharpen bits! I drill a pretty fair amount of stainless, and HSS bits go south after just a few holes.


Regards, John McGraw