Mill an open slot in thin material.

[DaveH]

Not really a “How to” but “How I did it”.
I am just showing how I did it, I am not saying it is the right way or the only way – just my way.
These are the parts with an open slot. The material is 25mm x 5mm thick steel (actually it is key steel). The slot is 6mm wide.
   

I cut a closed slot with an ordinary slot mill (drill) with centre cutting. As you can see it is twice as long (plus a bit extra), so I can cut it in half.
   

It is then cut in half and trimmed to the required length.
This shows one half “set in the vice”
   

It can be very temping especially if only one is required to cut it like in the set up shown. One of the main problems occurs when the slot mill breaks through the end of the part. As the slot mill breaks through the work piece, we now have a “tuning fork” which can vibrate with enough force to loosen the work piece, break the slot mill and generally mess everything up.
So beware of cutting open slots in thin materials.
Sometimes it is better to cut a closed slot and trim the material to size thus ending up with an open slot.


DaveH

[EdK]

Dave,

What is "key steel"?

Ed

[DaveH]

(07-07-2014, 06:15 PM)EdK Wrote: Dave,

What is "key steel"?

Ed

It is mainly an English term for a particular type of steel but it is available here and is /was mainly use to make 'keys' not the lock type keys but the ones used on shafts.
Available in square and rectangular sections (bright bar). The main reason I like it is because in machines better than ordinary bright mild steel.

DaveH

[DaveH]

Every Country makes there own particular grade of steel and trying to find equivalents from one Country to another seems extremely difficult.

DaveH

[EdK]

Got it. It's called keystock here.

Thanks,
Ed

[awemawson]

Key steel is pretty well identical to EN8 - medium carbon (0.35 0.45 %) with a bit of manganese

[stevec]

'Round here it depends where you source your "keystock" as to what type/quality of steel you get

[TomG]

That's the way to do it Dave if you need two parts. if you only need one, rotate the part 90º and place a piece of scrap between the jaw and the part to mill into.

Tom

[DaveH]

(07-08-2014, 11:12 AM)TomG Wrote: if you only need one, rotate the part 90º and place a piece of scrap between the jaw and the part to mill into.
Tom

That is the good machining way to do it, because one is machining against the vice jaw. And if you can always try to machine against the fixed jaw.

DaveH

[Dr Stan]

Another trick is to sandwich the material between pieces of plywood.