Use horizontal mill as saw for metal?

[ell81Participant @ell81]

I have just purchased a horizontal mill with an arbor and it obviously has spinning cutters similar to a circular saw, but can it be used to cut through thick metal? I assume you would have to do it in passes like a normal milling operation. Thanks.

[RobinParticipant @robin]

Bit shy on information…

“Thick”? “Metal”? You can probably go a lot deeper than you could with a slitting saw.

Choice of side and face cutter can be limited by what arbours you have and their keyways.

Sounds like fun 🙂

Robin

[noel shelleyParticipant @noelshelley55608]

As Robin says, we need more info ? Noel.

[Andrew CrowParticipant @andrewcrow91475]

Even without more information, using a sitting saw on a horizontal milling machine to cut through plate material is quite normal practice. How big obviously depends on the size of the machine and the cutter. I would recommend using slitting saws rather than side and face cutters for this operation. They cut better with several teeth in contact with the material that you are cutting.

Andy

[BazyleParticipant @bazyle]

Slitting saws are relatively expensive so not the best choice for bog standard hacking off metal. Look at the correct speed and feed for the slitting saw you are considering as you need to ensure each tooth is actually cutting an appropriate amount or it will break or rub then melt if not correct. The correct speed for a decent diameter is far slower than you expect and most mills cannot go very slow.
There are metal cut-off saws bit like the wood ones so look at the blades they use and the parameters that go with them.

[old martParticipant @oldmart]

Sounds like it could work well, using slow speeds. You may have to make an adaptor, but at the museum, we were given a number of slitting saws up to 8″ diameter with 1″ bores in widths of 1/32″ to 1/4″. I have used some on a custom R8 arbor successfully, but only have vertical mills, a horizontal spindle would work better.

What mill do you have and what spindle fitting doe’s it have?

[Roderick JenkinsParticipant @roderickjenkins93242]

Bazyle’s got it right.  When I bought my Sharp MkII milling machine, which has a horizontal milling option, I bought  a couple of 4″ diameter slitting saw blades thinking that they would go through steel bars like a knife through butter.  Wrong!  They blunted almost immediately.  You need to be  very aware of the correct feeds and speeds, which are much slower than you might think- a 4″ blade has a long perimeter.  A cheap bandsaw is much better.

Rod

[vintagengineerParticipant @vintagengineer]

You can use small T/C blades meant for circular saws.

[FulmenParticipant @fulmen]

You don’t even need a horizontal spindle:

 

No, I never turned it on *shudder*

[ell81]

On 7 April 2025 at 15:53 ell81 Said:

…can it be used to cut through thick metal? I assume you would have to do it in passes like a normal milling operation.

In a word yes. I regularly use slitting saws on a horizontal mill to slice off long lengths of hot rolled steel and extruded cast iron that won’t fit in the bandsaw. Maximum material thickness is around 75mm.

As stated above, I run the slitting saw slowly, usually 30/60rpm as they are the slowest speeds on my mill. Depth per pass is 10 to 15mm and feedrate is set by a chip load of around 0.1mm/tooth. Flood coolant is used, even on cast iron.

Good quality slitting saws are hollow ground so there shouldn’t be much rubbing of the cutter faces.

Julie

[RobCoxParticipant @robcox]

Yes, you can do it and I have a few times to cut sheet steel more accurately than using a shear.

BUT, it takes a deal of care. Using a conventional milling technique, the cutter tries to lift the material away from the mill table, so it must be well clamped down all along the length of the cut. If you try climb milling the cutter will push the material down but the backlash on my mill makes this a non starter as it feeds in fits and starts and threatens to break the saw.

If you’re going to cut thicker stock beware the cutter gullets filling up. You’d need fewer teeth with deep gullets for this.

I avoid doing this unless I have no better alternative.

Rob

[PeteParticipant @pete41194]

As others have said, the correct rpm is going to be much less than what most might think. I’d calculate that rpm from the recommended speeds for any metal type, and then drop down to at least 20%-30% less that that for what blade tip material your using. Maximum rpm is calculated for production and most you might find probably assume flood cooling. Tool replacement costs for us are a lot more important, so a bit slower is cheaper. Feed rate is also going to be much faster than most might think with any high tooth count saw blade. I’d start with about .002″-.004″ feed rate per tooth. So those cutting rpms verses the blade diameter, the exact tooth counts, and the correct feed rate are going to be pretty important to be 100% sure of what your doing.

I’ve read that for the thinner slitting and slotting blades it’s better to take multiple cuts for slicing the metal right through so that’s how I do it. Something like screw head slots I’d do in one pass at full depth. As the blade cutting width increases, the saw blade becomes much more rigid, so deeper depths of cuts are possible if the machine has enough HP. Depending on the blade type and width, that machine HP and rigidity, it’s probably something that can’t have any real recommendations for the optimum depth of cut for saw type blades. I try to be fairly conservative, and especially so for rpm. Heat and abrasion from any cutting tip rubbing is what destroys cutting tools the quickest. Deeper in softer metals, less for harder. Brass and cast iron because of the small chips are in my opinion much easier than steel. Thin slitting saws are extremely delicate, and your going to ruin some before you learn what they won’t do. I can’t prove it, but making an initial light cut first seems to help keep the thinner slitting blades tracking in the same saw kerf better for the next cuts. Cutting oil also reduces the abrasion and helps to lower the heat build up. Oil is cheap, cutting tools aren’t.

I see the mistake made often on YT videos, but sawing or even drilling unneeded material away so it’s still slightly oversized whenever possible, and then making the last few finishing cuts to size is usually multiple times faster and cheaper than using an end mill to slowly do the same.

[BazParticipant @baz89810]

Myford used to offer a circular saw attachment for metal cutting to fit the ML / Super7 range the stock could be either hand fed or clamped down with a bridge clamp.

[Julie AnnParticipant @julieann]

Slitting saws come in two basic forms, coarse tooth and fine tooth. Here are a selection of slitting saws:

The slitting saws are all coarse tooth apart from bottom right which is fine tooth.

Fine tooth slitting saws are intended for shallow cuts only, like slotting a screw head. For deeper cuts use a coarse tooth saw, otherwise the gullet will get full of swarf and jam the saw.

Julie

[Alistair Robertson 1Participant @alistairrobertson1]

For many years we cut 100 x 50 x 5mm Wall RHS at a very acute angle. We cut about 50 a day and the cutter was sharpened ( or swapped over) about once a month. Absolutely no problems for years. Far better than trying to cut in a band saw!

This was on an old east German mill that had been in the Chrysler factory at Linwood machining out the Hillman Imp blocks for fitting the Main Bearing Caps. I was really sad to see it go for scrap when our factory closed down!

[Howard LewisParticipant @howardlewis46836]

One warning re Slitting Saws!

Do NOT use a key!

Just rely on friction to drive the saw.

If the saw jams, and a key is used, the saw can shatter and send debris flying everywhere.

I had a narrow escape, when just that happened as I walked past a mill, despite the operator having been told not to use a key!

Howard

[Dave HalfordParticipant @davehalford22513]

The OP does have a motor hacksaw, but without the motor at the moment. Thread has now slipped to page 2.

[HOWARDTParticipant @howardt]

Use a circular saw blade intended for cutting steel if you can meet the cutting parameters.  Slitting saws are constant thickness and swarf does get trapped in the slot as the saw goes through so are more suited to thinner materials as the trapped swarf causes the cut to deviate from square.  Production sawing machines for cutting metal are often circular saws as they keep a square cut.

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