Cutting thin slots in 2mm mild stee

[Peter Simpson 3Participant @petersimpson3]

What is the best way to cut a 1/2″ long x 1/16″ wide, full depth slot though 2mm mild steel strip. I have a 1/16″ slot drill and a 1/16″ end mill. I have though about chain drilling most of the metal away then using the slot drill to clean the slot up to a finished dimension. Not sure if the slot drill will cope with even the lightest sideways cutting force.

[Michael GilliganParticipant @michaelgilligan61133]

It should probably be a job for a slitting-saw … but the problems associated with those have exercised the forum a lot recently !

MichaelG.

[Nigel Graham 2Participant @nigelgraham2]

Chain drilling is likely to create problems, not solve them.

Milling cutters, especially in these small diameters, are much better in homogenous material. Chain drilling leaves lots of “teeth” that could snatch the flutes, possibly breaking the cutter.

You don’t say how precise the slot has to be, but if it is critical, e.g. a keyway, it may be better to use an under-size cutter first along the centre-line then gently take the sides out to finished width.

 

 

[JasonBModerator @jasonb]

The cutter should certainly withstand the correct cutting forces other wise there would be little point in them being made.

Stitch drilling such a small slot can cause as many problems as it solves as the cutter moves from little load to no load it can snatch.

Try drilling each end a little undersize say 1.4mm so that you can feed the cutter downwards without it having to ctr cut. Don’t try it all in one go say 10-15thou depth per pass. Run fast 2000rpm and feed gently but constantly. Keep chips out the slot so they don’t get recut or deflect the cutter. Use the slot drill for a more accurate width

 

[HOWARDTParticipant @howardt]

Slitting saw will be the easiest but you may have to do a bit of reshaping when it is cut. The forces within the sheet may well cause the material to spring apart either side of the slot, it may also widen. Do a test on the material before cutting your final piece.

[Peter Cook 6Participant @petercook6]

Clamp it down on something sacrificial – bit of MDF for example. As Jason says take shallow cuts, and run it fast.

[JasonBModerator @jasonb]

I had assumed the slot was not open ended, maybe the OP can confirm?

[Peter Simpson 3Participant @petersimpson3]

The slot is not open ended. Will go for the slot drill with holes drilled at both ends, thanks your views.

[Neil LickfoldParticipant @neillickfold44316]

If you are cutting a slot and the end is not open, then only drill a hole at one end. Running into a hole can be the cause of damage o the cutter. Cut with a small depth of cut and having a vacuum cleanser or some other suction device to draw away the swarf will make the cutter last a lot longer. Having the material clamped is also important. A cut depth of 0.1mm to 0.2mm id being realistic at a fine feed. Only feed in 1 direction, as if you feed in both directions, you can have an oversized slot. If the end if open, no need for a drilled hole. Ideally to make a 1/16 slot, would cut with a 1.5mm cutter first, and then finish each side, or finish with the 1/16  cutter at full depth with a slow feedrate. Slow being at a rate of 0.01mm to 0.02mm feed per tooth. So at 1200 rpm, the feed rate will be 24 to 48 mm/min or 0.5 to no more than 1mm per second feedrate. You can use this rate for the roughing out too but at lower depths of cut.

[MikeKParticipant @mikek40713]

I would be inclined to use my bandsaw, or grind the set off of a hacksaw blade and set it up between two blocks to keep it perpendicular.  Testing the methods on scrap first, of course.

Mike

 

[Clive Brown 1Participant @clivebrown1]

Since the slot is only 1/2″ long and closed-ended, I’d have thought that slitting saws, bandsaws and hacksaws seem rather ruled out. A slot drill, as opposed to an end mill, should cut to accurate width if that is important. A 1/16″ end mill might cut a trifle over-size.

[JasonBModerator @jasonb]

Clive, I don’t think we have established if it is open or closed. Some have assumed it is open and 1/2″ in from the end, others like you and I that it is closed.

[Michael GilliganParticipant @michaelgilligan61133]

Clive

The usefulness, or otherwise, of a slitting-saw [in the ‘closed slot’ version of the job] would very much depend upon its diameter.

MichaelG.

[John Doe 2Participant @johndoe2]

8th post in:

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The slot is not open ended. Will go for the slot drill with holes drilled at both ends, thanks your views.

[JasonBModerator @jasonb]

Thanks John, I missed that.

[MikeKParticipant @mikek40713]

I missed that too.  Sorry.  I need to pay attention more.

[Peter Simpson 3Participant @petersimpson3]

Sorted with a 1/16″ end mill and a hole drilled at on end of the slot.

[Author]

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