Sharpen a dull holesaw (YES it works!)

[Thomas]

Hmm... worth try.

 

[MossRoad]

I've had very good luck with Milwaukee brand bi-metal hole saws. I was cutting about 50 - 1" holes in 1/4" and 1/2" mild steel and only used two of them. I was pretty amazed they cut that many holes for the price. I used cutting fluid and not a lot of speed on a cheap harbor freight table top drill press. They are worth a try.

milwaukee bi-metal hole saw - Google Search

 

[aczlan]

when cutting a 2-1/2" hole horizontally to install a transfer switch, i cannot use lube or drill vertically. My holesaws were drilled at slow speed, but sometimes never made it thru one hole without dulling. the carbide bits dont seem to have that issue.

Why not use a knockout punch tool?
The electrician at work has a older Greenlee one like this: https://www.homedepot.com/p/Eclipse-Tools-Hydraulic-Knockout-Tuff-Punch-Kit-902-482/20630329 that goes from 1/2” up to 2 1/2” and works like a charm to punch holes for conduit...

Aaron Z

 

[wheelbuilder]

This works on bandsaw blades too...
I hadn't thought about it for this though. Good idea!

 

[chim]

Been making holes in things since 1968, especially sheet metal. Vast majority have been in sheet metal up to 16ga. Hole Saws are still used in some cases, but are not the first choice. For holes in electrical enclosures, KO punches are the first choice. In recent years we've gone to battery powered Gator or Milwaukee punches for most of the work. The ratchet punch in the photo was a freebie from work when we went batter powered several years ago. Handy for home and easier than the old manual punch set I bought 40-some years ago.

When we do use hole saws at work, they are generally used at low speed and dry. Lifespan isn't that bad. It helps if the saw isn't pressed against the material so the entire saw makes contact. A slight rotation (orbit?) of the drill so the saw only makes contact in a small area works best. The blade seems to run cooler and the slug doesn't get stuck in the saw. For smaller conduit holes, the DeWalt Impact Ready hole saws are sometimes an exception to the KO punch usage. They're super for doing pilot holes for the big KO punches. With any hole saw, we need to be conscious of chips around electrical equipment.

For thick materials, the weapon of choice is an annular cutter. A little of the special lube (that looks like ear wax) and the bits last almost forever. At home I've had to make up to 1" holes in 1/2" thick steel. I used a battery drill and a gentle stream of water from a garden hose to flush chips and keep things cool.

This assortment takes care of most of my homeowner needs.

 

[grsthegreat]

Why not use a knockout punch tool?
The electrician at work has a older Greenlee one like this: https://www.homedepot.com/p/Eclipse-Tools-Hydraulic-Knockout-Tuff-Punch-Kit-902-482/20630329 that goes from 1/2 up to 2 1/2 and works like a charm to punch holes for conduit...

Aaron Z

I have a hydraulic punch kit. But I'm installing the transfer switch recessed in next stud bay and drilling 2 of the 2-1/2 holes thru both panels and the stud. Punch kit wont work. My greenly hydraulic kit punches up to 4 inch holes, but the panel would have to be removed from wall to operate punch

 

[aczlan]

Ah, it's that pesky two-by-four in the middle that makes the punch unworkable.

Aaron Z

 

[muddstopper]

I have used hole saws in metal up to 6in dia in my drill press and in metal 1in thick. I have managed to drill multiple holes with the same saw bit. The secert to getting life with a hole saw is to drill a hole just inside the cutting edge of the metal you wish to saw. This gives someplace for the chips to fall out of. Slow speed and generous cutting oil, not wd40.. Steady pressure so the bit will bite. Light pressure leads to more dust than chips. Also use a air nozzle to keep the chips blowed out. Chip build up is what dulls the saws, not cutting the metal.

 

[Industrial Toys]

I wrecked a 6" Milwaukie Bimetal blade cutting SS, but kept it in case it might still work for drywall. Should give this a try.

 

[PILOON]

I have used a Milwaukie "hole saw' in low and have cut up to 4" IN 1/2" steel with no problems as long as I lubricated the blade.
Slow, cool and lube is the way to go.