Reaming out holes in thick steel?

[workinonit]

About the cleanest tractor I've seen on here in a long time.. Most are cruddy and loaded with filth. Myself, I don't like getting greasy from the grease hanging all over a unit if I don't have to...

I was always under the impression that bi-metal hole saws are only for light gauge materials (I have a set of Blu-Mol's myself), but for thick steel hole drilling I use my Mag drill and a Roto-broach bit. Not cheap but not a wrist breaker either.

I love my Roto Broach kit. I just bored CAT III holes for my homemade Landplane style blade I'm building. Bored the holes in 1" material. Drilled a pilot hole through, bored half the hole and flipped it to bore the other half. But I'm pretty sure you couldn't use them for this application without doing something sililar to what was mentioned above.

 

[stuckmotor]

That's interesting. Unless the smaller saw protruded beyond the larger saw to act as a pilot, I guess the path of least resistance for the combined saws would keep them on center?

That's interesting. Unless the smaller saw protruded beyond the larger saw to act as a pilot, I guess the path of least resistance for the combined saws would keep them on center?

My aggravating tablet won't paste a compete link.
I found several presentations of how to center the larger saw by putting "Centering hole saw in large hole" into the YouTube search box. AVE did his enlargemet in metal and told what to do if the larger saw had a larger arbor.

 

[5030]

I love my Roto Broach kit. I just bored CAT III holes for my homemade Landplane style blade I'm building. Bored the holes in 1" material. Drilled a pilot hole through, bored half the hole and flipped it to bore the other half. But I'm pretty sure you couldn't use them for this application without doing something sililar to what was mentioned above.

Bought my mag drill used on CL a few years ago and grabbed the broach kit on MSC while it was on sale.

 

[Xfaxman]

How do you stay true center with the hole saw w/o use of a pilot hole? I remember somebody on youtube showing a neat trick for that, but don't recall exactly what he did.

Sberry's picture in post # 31 shows one way that I have used. Clamp the right size hole over the too small hole:

 

[jmc]

My aggravating tablet won't paste a compete link.
I found several presentations of how to center the larger saw by putting "Centering hole saw in large hole" into the YouTube search box. AVE did his enlargemet in metal and told what to do if the larger saw had a larger arbor.

Maybe this is it. He did get the inner saw to stick out.

 

[fried1765]

How do you stay true center with the hole saw w/o use of a pilot hole? I remember somebody on youtube showing a neat trick for that, but don't recall exactly what he did.

There is a mandrel kit available for centering a larger hole saw on a smaller existing hole.

 

[Seven Gables]

Sberry's picture in post # 31 shows one way that I have used. Clamp the right size hole over the too small hole:

View attachment 703870

I think sberry got the best idea

 

[chim]

I've done that. (sberry Post #31) You can even use a scrap of 1/2" plywood for the template. It also enables you to change the location of the center of the hole if needed by clamping the template where you want it.

 

[BukitCase]

Another trick I've used (may not be possible depending on accessibility) -
if there's room -
1 - Drill a 1/4" hole in a piece of scrap material - this will be clamped BEHIND the material (but not yet)

2 - Set up the ORIGINAL size hole saw in its arbor but don't put it in the drill yet

3 - REMOVE the pilot drill bit from the hole saw - REPLACE it with a piece of 1/4" drill rod or possibly a VERY long 1/4" bolt with the head cut off; also cut off the threaded part. This will minimise the (no longer there) flutes of the (no longer there) pilot drill bit.

4 - Hold the scrap piece up against the hole to be enlarged, insert the protruding 1/4" rod in the hole you drilled - slide the backing piece around until the OLD size hole saw slips into the OLD size hole (the one you're going to enlarge)

5 - Now clamp the backing plate FIRMLY in place - then REMOVE the hole saw from the old hole and replace the hole saw with the NEW size one (KEEP the 1/4" smooth pilot ROD - BTW, you'll thank yourself for putting a SLIGHT taper on the end of the pilot rod)...

6 - Finally, mount the LARGER hole saw on the arbor with the SMOOTH 1/4" pilot, making sure the pilot rod is LONG ENOUGH to engage the pilot hole in your scrap piece; then mount the hole saw in your drill and enlarge the hole - if you follow ALL the above steps, it should result in a clean/larger hole that is on the SAME CENTER as the original hole. It also keeps an even load on the hole saw, and lessens the chance of wandering/jumping around while (re)drilling.

7 - All proper PPE is assumed, especially eye/face protection - I've also found that a fairly competent HELPER keeping a stream of compressed air aimed at the hole saw's teeth can make hole saws last longer AND cut better.

Or, if you were ALREADY too impatient to have bothered to READ this, grab your "gas axe" or plasma and WING IT ... Steve

 

[GeneV]

Nice, yeh! I mean both using a smaller hole saw as guide, and also clamping on a sacrificial piece of wood or stock to have something for the drill bit to bite into...I believe that's what the fella did in the youtube thing I saw.