Cutting thin slots in 12mm mild steel

[Peter Simpson 3Participant @petersimpson3]

Hi All,

 

I need to cut two narrow slots in a mild steel block. This a plan view of the item, The steel is 12mm deep. The central hole is 7mm diameter and runs right through the 12mm block. The two slots are 1.5mm wide they also run through the block. A 1.5mm end mill is not long enough to cut the full depth. Any tips would be appreciated.

 

 

 

hol

[Julie AnnParticipant @julieann]

If you want square ends to the slot an endmill will not cut it, so to speak.

Could drill some holes to remove most material and then file to finish. Alternatively make a slotting tool or a broach; again it would help to remove material by drilling first.

Julie

[Robert Atkinson 2Participant @robertatkinson2]

What accuracy is required?
The sketch shows square ends on the slots is this correct? An endmill will leave a radius.

[cogdobblerParticipant @cogdobbler]

Junior hacksaw and file at one end of the scale. EDM at the other.

Hacksawing could be enhanced by making a simple jig out of square bar etc clamped to the job to guide  the blade. Blade may need ground down to fit through the 7mm hole.

A lot depends on what the application is and how precise the slots need to be. More info needed really.

[DC31kParticipant @dc31k]

Does the item have to be one piece?

Cut it on a vertical centreline, make the slots, sellotape it back together and then finish the hole in the correct place.

Similarly, it could be cut on a horizontal line and some 1.5mm steel used to make the two tabs extreme left and right.

What is the standard cutting depth for an endmill in multiples of diameter? You only need 4 x d to reach halfway.

[IanTParticipant @iant]

I would do this with my hand shaper, which is very useful for small jobs like this. However, assuming you do not have a hand shaper, you can do this in the lathe with a bit of effort.

Centre the work in a 4-Jaw and drill/ream your 7mm hole.

Make a holder to grip the end of a small (1.5mm) parting tool horizontally/flat and on centre. My small ones are 1.5mm x about 8mm I think, so they would need reducing slightly in depth for about 12-14mm (to fit your hole). Grind some relief on the front cutting edge. If I’m not beiing clear, the tool holder doesn’t enter the hole, just 12mm of the cutting tool. It works if everything is set correctly…

You can then slot the work using the lathe rack to work to and fro, putting small cuts on using the cross-slide until you reach depth. Then index the chuck around 180 to do the other slot. There are ways to do this simply with the chuck jaws…

So it will take some time to make the holder/tool and set it up but the actual work will take just a few minutes…

Hope this helps.

Regards,

 

IanT

[JasonBModerator @jasonb]

As IanT says but may not even need a special holder, just get one of teh 1.5mm parting blandes and clamp it in the toolpost and away you go. I’ve done similar with a 3mm bit of HSS

[FatgadgiParticipant @fatgadgi]

If accuracy is required that’s a bit tricky, Peter, although plus one for Jason’s suggestion.

Classic question – what is its function, ie if more accuracy is required, is there another way?

Cheers Will

 

[old martParticipant @oldmart]

Jason has the easiest solution using a lathe and either a faceplate or four jaw independent chuck. The plate would have to stand off the mounting surface where the cuts are. Also you would have to find a way of locking the spindle. It would take time setting up and in taking tiny cuts, but doable.

[JasonBModerator @jasonb]

The 4-jaw would probably be the best bet then it is easy to index with a block between the bed and the underside of a jaw. That is how I did this one . 4 x 3/16″ slots 1″ long in steel though I did have room for the typical boring bar set  up.

 

[Peter Simpson 3Participant @petersimpson3]

Many thanks for all you suggestions, I have a Boxford shaping machine but my experience on it is very limited. The lathe method with a parting off blade looks the favorite.

[JasonBModerator @jasonb]

The shaper would do a better job and not put any strain on the lathe which this method can do.

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