Slotting/end Mills Question

savarin

savarin

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I have some milling cutters that I think are called end mills or maybe end/slotting mills.
They are flat on the end with one cutting edge passing across the mid point with sharp sides like a twist drill.
I need to mill a 12mm wide slot in a chunk of mild steel (on my lathe of course) 90mm long and 20mm thick.
I've drilled a series of 12mm holes along the centre line but really do not want to file out the remainder (too lazy)
The chunk can be mounted firmly for cutting but I think I have read somewhere that using these cutters to cut both sides of a slot at the same time is bad practice.
It would have to be done in multiple passes till half way through then flipped to finish for full depth.
My question is:- can they be used this way?
 
Yes. BUT.... The primary reason people don't like to use full size end mills on slot work is because they tend to pull off to one side from the cutting forces generated. If you then run the cut back to the origin, you will get an oversized slot. Also, they tend to not give as smooth finish as you could get going with an undersized mill and milling each side of the slot with an offset. You will find that cutting from one hole into the next to be a little bothersome, as it tend to grab as it breaks over the "hump". The dept may or may not be a problem cutting in one depth setting. That is going to depend on the rigidity of the setup and your milling attachment.
 
Yes, done every day in machine shops across the world, rough it as fast as your machine will allow with a smaller tool, change tools and walk off a light finish cut. If you insist on the typical hobbyist +- .0005 tolerances you are doomed.
 
Sounds like it will work fine. ;)
 
What I would do, now that you have the 12mm holes, supposedly on location at each end, is run a 10mm end mill down the middle, then move over 1mm and run back, move over the other 1mm off center and run back to the other end. It won't take as long as you think, and you'll have a decent slot. If you can climb cut the 1mm cuts, so much the better, but you don't have to. If you want to get fussy about it, leave about 0.2mm per side and climb cut. Semi-lock your travel so the climb won't get you in trouble. That is, if in your judgment, your mill attachment can handle that.
 
There is no milling attachment yet. This is to be the new middle of the vertical slide, I can bolt it in place but only centered so I cant move up or down.
Its suddenly come to a halt anyway as I've snapped a 4mm tap in a deep hole:mad: so now I have to re-wind the coil for the spark eroder.
You would think I would have learnt this lesson by now:bang head:
 
Charles,
I appreciate you probably want to do this yourself on your lathe, but if you get stuck my mill is always here.

Cheers Phil
 
Thanks Phil, much appreciated, yes I wish to see just what can be done with only a lathe.
Masochistic me.
Finished re-winding the coil for the eroder and hope to get it running tomorrow.
 
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