What size milling tool

[Garry Smith 7Participant @garrysmith7]

[Garry Smith 7Participant @garrysmith7]

I have a piece of 3 mm steel plate that I want to practice milling on to straighten the edges. Is there a rule of thumb for the diameter of the mill in comparison to the thickness off the stock material. I will initially be using my mini lathe with a mill attachment fitted and a ER32 collet chuck

[not done it yetParticipant @notdoneityet]

Side milling or end milling? HSS cutter?

Side milling uses more of the mill cutting surface and not the most expensive part. Only need to end mill on thicknesses that cannot be easily side milled. Choose your standard surface cutting speed (material of cutter) and the spindle speed will depend on the cutter diameter.

Feed will depend on the number of flutes and depth of feed will depend on power, after that lot has been determined ( but not more than a third of the cutter diameter).

Don’t try to climb mill unless minimal cutting depth as a finishing clean-up cut.

[David George 1Participant @davidgeorge1]

Hi Gary what size is the plate. If the plate is small I would drop it into a vice maybe with a parallel to give enough sticking up to cut nicely and would use a 1/2 inch end mill, conventional milling, cut other side to be parallel. Lay flat in vice on vice on parallels with a small amount sticking out and using the same cutter use the side of the cutter to clean up the third and flip and cut fourth sides. If it is to big to fit into a vice I would put it on parallels and clamp down and use the side of the cutter clocking up as nessesary for each side and rotating the plate for each side.

David

[Douglas JohnstonParticipant @douglasjohnston98463]

Once the end of an endmill has become blunt, a lot of cutting is still possible using the side edges of the cutter. Straightening the edges of plates is a perfect example of this. All you need is some way of holding the plate flat so the edges can be machined. It is also useful to use different parts of the cutter sides to even up the wear.

Doug

[Garry Smith 7Participant @garrysmith7]

Thank you gentlemen for the tips and method. I’m still looking to find a rule of thumb for the diameter of the mill compared to the width of the stock. I am assuming you would want to have as little passes as possible. Therefore your mill diameter should be wider that the width of stock you are cutting. Is this a fair assumption (Assumming your using the side of the mill to cut) If cutting with the end of the mill does this still apply ?

[Keith LongParticipant @keithlong89920]

Garry, in the"Model Engineers Handbook" by "Tubal Cain" (T D Walshaw) for profiling with an end mill he states that the best results are when the cutter – diameter D is cutting a vertical depth (plate thickness ) of D and a maximum width of cut into the material of D/4. He also suggest that the minimum vertical depth of cut should be 0.006" and the maximum width of cut should be no more than engages 2 teeth on the cutter. The cutter diameter that you will use is more determined by what the mill can cope with in terms of power ,speed and rigidity. I've just been profiling 2 steel plates 6mm thick, stacked on top of each other (12mm total thickness) so that they came out the same sizes and my small mill was happy with 3mm passes (vertical height) and 1mm width of cut at 1000 rpm using a 6mm dia, 3 flute carbide cutter.

Keith

[old martParticipant @oldmart]

I recommend getting an indexable milling cutter such as this 16mm diameter type advertised on ebay UK 401828258237. It takes APMT11 and APGT11 size inserts. There are alternative sizes such as these 12mm diameter ones 123850739467 which include inserts for steel. APGT11 inserts for aluminium 273401110660. If the holders are too long, just cut them down with a hacksaw.

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