Mag drill line boring guide
How to Line Bore with a Mag Drill
You can line bore with the magnetic drill press you already own. The mag drill turns the boring bar, a portable line boring set keeps the bar straight and centered, and you feed the cut by hand. This guide covers the setup, which mag drills work best, how to get a clean cut by hand, and when it makes sense to step up to a power feed.
- Use the mag drill you already own
- Works with IRM Set A and Set B
- Written by the Chicago shop that builds IRM line boring sets
How it works
How mag drill line boring works
In mag drill line boring, the mag drill is only the drive. It mounts on a plate at one end of the setup and turns the boring bar. The line boring set does the precision work: bearings on each side of the bore hold the bar in line, centering cones line it up with the original bores, and the plate or channel ties it all together. The tool bit in the bar cuts the bore as you feed the bar through by hand.
What you need
- A mag drill to turn the bar
- A portable line boring set with bearings, centering cones and a plate or channel
- A mounting plate for the mag drill base. The plates on IRM sets are interchangeable.
- A line boring bar long enough to span both bores
- Tool bits with replaceable inserts, plus a way to measure the bore
Choosing a drill
What to look for in a mag drill for line boring
Line boring cuts slowly and puts a steady load on the drill. A mag drill that is great for drilling holes is not always the best drive for a boring bar.
- Low speedA low-speed gear or variable speed lets you run the bar slowly, which is what boring needs.
- TorqueEnough torque to keep the bar turning steadily under load, especially on larger bores.
- A base that fitsThe magnetic base needs room on the mounting plate. Send us your drill model and we'll confirm the fit.
- Room to workCheck there's clearance around the bore for the drill body and your hands while you feed.
Setup
How to set up a line boring bar with a mag drill
- Center and mount the setUse the centering cones to line the boring bar up with the existing bores. Fix a bearing on each side and level the plate or channel. Adjustable legs handle uneven surfaces.
- Attach the mag drillMount the mag drill on its plate and connect it to the boring bar so the drill turns the bar. Set the tool bit for a light first pass. BoreRight makes small adjustments easier.
- Start by hand, then feed steadilyAlways start the cut by hand to feel how the machine is cutting. With a mag drill you keep feeding the bar yourself through the whole cut.
The full process, from centering to final size, is in our step-by-step line boring guide.
Hand-feed tips
Tips for a clean cut when feeding by hand
With a mag drill, the finish depends on you. These habits make the biggest difference.
- Keep pressure evenPush at the same steady rate the whole way through. Stopping and starting leaves marks in the bore.
- Take light passesSeveral light cuts are easier to control by hand than one heavy cut.
- Measure before the last passCheck the bore size before the finish cut so you don't go oversize.
- Keep a sharp bitA dull tool bit takes more force to feed and leaves a rougher finish. Replaceable inserts make this easy.
Compare
When to use a mag drill, and when to use a power feed
Both can drive the same IRM line boring set. The difference is how the bar moves through the cut.
Mag drill
- Use the drill you already have
- You feed the bar by hand
- Finish depends on keeping steady pressure
- Good for lighter or occasional jobs
IRM Power Feed
- Automatic, consistent feed
- Runs on a standard handheld drill
- Smoother finish and easier size control
- Better for long bores and everyday line boring
Doing line boring every week?The IRM Power Feed fits Set A and Set B and takes the hand feeding out of the job. Starting at $3,990 with a line boring set.
See the Power FeedVideo
Watch: line boring with a mag drill vs a power feed
We run an IRM line boring set with our Power Feed, then swap in a mag drill on the same setup so you can see and hear the difference in the cut.
- 2:00 Cutting with the Power Feed
- 9:31 Swapping in the mag drill
- 10:45 Our custom tool bits with replaceable inserts
FAQ
Mag drill line boring questions
Can you line bore with a mag drill?
Yes. A mag drill can drive a portable line boring bar. The line boring set keeps the bar straight and centered, the mag drill turns it, and you feed the cut by hand.
Do I need a special line boring kit for a mag drill?
You need a line boring set with bearings, centering cones and a plate the mag drill can mount to. IRM Set A and Set B work with a mag drill, and the same set takes our Power Feed later.
Will my mag drill fit an IRM line boring set?
Send us your mag drill's make and model, your bore size and the distance between bores, and we'll confirm the setup. Call (224) 435-6999 or use the form below.
Is a mag drill as accurate as a power feed?
The set controls alignment either way. The difference is the feed: by hand, it is harder to keep steady pressure, so finish and size control are not as consistent as with a power feed.
What size boring bar do I need?
It depends on your bore size and the distance between bores. IRM line boring bars range from 0.875" to 1.75" in diameter and 21" to 100" long.
Line bore with the mag drill you already have
Tell us your bore size, the distance between bores and your mag drill model. Anguel will help you put the right setup together.
Questions about line boring with your mag drill?
We’re ready to start as soon as you are. Fill out the form below, and a representative will be in touch shortly to kick off your next line boring project.
- Prefer to talk? (224) 435-6999
- Helpful to include Bore size, distance between bores, and the equipment you're repairing.
- Built in Chicago Designed and manufactured by IRM. Works with standard handheld drills.