Need to drill a hole...

[Ron JD670]

Guys, I need to drill a 1 1/8" hole in 4 pieces of 3/8" thick mild steel. I don't have a plasma cutter or a torch...all I have is a good drill press.

What would you use to do this job with given my lack of equipment? I've looked around here and there are no bits that large for sale anywhere that I've seen, but would a step drill do it? I have drilled up to 3/4" holes around here but I've never had to do one this size and I was wondering what would be best to use in my situation.

Thanks!

Sounds like the hole does not need to be perfect. Here is a cost effective approach with tools most of us probably have.

Scribe a circle 1&1/4 inch in diameter.
Then center punch on the scribe line every 3/8 inch.
Use a 1/4 drill to around the circle. The 1/4 drill, if sharp, should punch through relatively quickly.
Once you drill out the circle cold chisel the 1/8 remnant between the holes.
Then with a dermal tool or file etc. finish rounding the hole.

Unless you need a 1&1/2 drill bit in the future this is more cost effective. Also, compared to drilling a 1&1/2 at the requisite low speed this may take about the same time.

My shop teacher showed me how punch a big hole this way as a project. Wondered when I might use this again.

Good luck and best wishes
RoN

 

[JoelD]

Sounds like the hole does not need to be perfect. Here is a cost effective approach with tools most of us probably have.

Scribe a circle 1&1/4 inch in diameter.
Then center punch on the scribe line every 3/8 inch.
Use a 1/4 drill to around the circle. The 1/4 drill, if sharp, should punch through relatively quickly.
Once you drill out the circle cold chisel the 1/8 remnant between the holes.
Then with a dermal tool or file etc. finish rounding the hole.

Unless you need a 1&1/2 drill bit in the future this is more cost effective. Also, compared to drilling a 1&1/2 at the requisite low speed this may take about the same time.

My shop teacher showed me how punch a big hole this way as a project. Wondered when I might use this again.

Good luck and best wishes
RoN

nice work around

 

[HiTechTed]

It doesn't have to be NASA perfect. My problem now will be getting my drill press to go below 250 rpm.

For the chips, I always just back off and vacuum them out, and clean off the bit or in this case the hole saw. I only need to do 4 holes and I'm on my own time.

 

[SPYDERLK]

It doesn't have to be NASA perfect. My problem now will be getting my drill press to go below 250 rpm.

For the chips, I always just back off and vacuum them out, and clean off the bit or in this case the hole saw. I only need to do 4 holes and I'm on my own time.

With a hole saw I think 250 rpm would be OK, altho I sure would like the option to slow down as conditions indicate. Be sure to use care at the start because the normal saw pilot isnt usually rigid enuf to prevent an orbital wobble on entry.
larry

 

[GuglioLS]

For large holes when I do not have a bit, hole saws work but I prefer 60 RPM or less. This one is 1-5/8 through 3/8 thick



I think H/F sells a 5 bit set something like 1", 1-1/8", 1-1/4", 1-3/8", 1-1/2" for around 50 bucks.

Larry

 

[Den1952]

I have used the hole saw for this scenario lots of times.(with a drill press) I find it works best though to have a 1/8" weep hole drilled through the kerf itself. I usually start the cut to get it established, then can find precisely where to put the weep hole, then continue with the hole saw.
then it is non-stop cutting with no worries. I go with about 60 rpm and hand feed the pressure.
It seems to me that going faster, with no weep hole, the materiel
surface- hardens , anyway, it doesnt cut well even with cleaning it out in progress.
what I would like to point out however is to be extremely carefull of the plug when removing it from the hole saw afterwards. the lower edge of the plug has a razor sharp burr around the perimeter and it'll slice you open like a scalpel. forewarned is forarmed.

 

[SPYDERLK]

I have used the hole saw for this scenario lots of times.(with a drill press) I find it works best though to have a 1/8" weep hole drilled through the kerf itself. I usually start the cut to get it established, then can find precisely where to put the weep hole, then continue with the hole saw.
then it is non-stop cutting with no worries. I go with about 60 rpm and hand feed the pressure.

A single 1/8" hole does it for the chips ? Nice. Introduce coolant at the hole and let it carry all the way round to exit with the chips.
larry

 

[Den1952]

yes , thats correct. I usually use just one hole drilled through the kerf. for something like a 5 inch hole, I would put another weep hole on the opposite side too. just dribble cutting fluid down the side of the hole saw while boring and if you were to look underneath the piece while cutting you will see the crud oozing out via the weep hole. non-stop cutting then, no need to back out and clean out.

 

[Travelover]

I had to drill a 2 5/8" hole through a 1/2" plate of mild steel. I used a bi-metal hole saw and 55 rpm on my lathe. Lots of oil, not too much force and backed off occasionally to clear the chips. After two holes, the blade still looked like new.

I was surprised, as I thought the bi-metal saw would self destruct.

 

[JohnDeere4300]

Amazon sells some nice hole-saw sets!

I use large Bi-Metal hole saws a lot when I need a nice clean round hole!! ... Just have the drill-press on the lowest RPM and use plenty of cutting fluid!!!

I have some large drill bits, But they won't fit in my Drill-Doc'... And they can be a pain at times to sharpen on a bench grinder!

If I don't need a perfect hole, Then I use Oxy' & Acet'... I use a marker to mark my circle, and drill a hole through the center... Then use a center punch and go all the way around the circle... That way when I cut out the hole I can still see the mark from the center punch!

Also, When drilling large holes it's good to have some large round ''Nicholson Files''!!!

Bill