Gallery, Projects and General > How do I??

How do I - locate centre and position end mill? - basic milling.

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raynerd:
Hi Guys

I`m after some real real basic milling advice before I make a start. If anyone could suggest a book, website or such that I could learn this, to you, obvious skills, then please do post up.

1. Say I wanted to make the part shown here at the back - partly hidden by the motor. It looks like a simple flat piece -



So I have the plans and if I am being honest, I bet I could have a good go, but I don`t think I would be doing it correctly! So lets consider we have the correct height of material, so it is a case of cutting to shape, and then trueing the edges. Would it be a simple case of taking a sheet, cutting it to rough shape with a hand saw and then mounting it in the vice to true the edges? But with such a big piece how would you hold it in the vice, what orientation? Also, to true the edges of the piece would you hold it vertically so that you were cutting with the end of the end mill or some how overhanging the piece and running the side of end-mill down the sides?


2. Basically if I want to mill a slot as shown below:



What would be the correct way to "locate" the end mill to position. If I used a slightly smaller end mill, I could produce the slot and then widen it to the correct size - would this be OK?  How could I get it accurate if I was using the correct size endmill, so I would need it bang on first time?

Sorry, I know they are the basics but I want to do it correctly.
 

bogstandard:
Chris,

You are asking for a lot of info in one post. You could write twenty pages and still not show how to square up an edge correctly.

The basics are, first get the job held securely and in the correct position to carry out the work. You will have to know your materials, so that you can select the right cutter for the job and the correct cutting lubricant to use. You will need to know what each type of cutter is used for, and how that cutter is set up to do the job. Feeds and speeds and recognising the way the cutter is doing it's job, and the list goes on and on.

You need to get the basics under your belt first, otherwise you could easily have a permanent impression of a tool or piece part in the middle of your forehead. The milling machine is one of the most dangerous machines for a model engineer to work with. The first thing you have to do is gain respect for the machine before you even turn it on.

I put up some links previously that will give you the basic insight into how and why and what if's of machining.

http://madmodder.net/index.php?topic=535.0

http://madmodder.net/index.php?topic=944.0

There are many more sites like these that can give you the basic information to get you started.

With regards to your question about making slots. The flex on a cutter will almost guarantee that it will cut oversized or very roughly if you just go straight in as you show. You would need to relieve the cutter pressure by either drilling away excess material, or remove it with a smaller cutter first. Then using the correct sized cutter to bring it to final size, even then it can sometimes cut oversized. I sometimes use a one sized down cutter and bring it out to correct width using that, but your end radius will be incorrect, so you either have to accept it as it is, or use the correct sized cutter to bring that part to size. That is on my very rigid machine, on yours, it is even more critical that you get the cutter pressures down.

More to it than you think isn't there Chris?, and you will find every job is different in the way it is handled. Reading about it can only take you so far, it is the hands on experience that gets good results.

I know this is a very negative post of mine, but you have to remember that you will be doing these jobs on your own, and away from other people. So god forbid, if something nasty does happen, you might not be found for hours. So unless you can get yourself to a stage where you can safely work by yourself with such a dangerous machine, you have to take things very steady and gradually. You might get away with it for a while, on the other hand, it could bite you the first time you use it, but bite you it will, eventually, unless of course you can walk on water.

John

Darren:
Some good advice there from John,

Chris,
I'm new to milling as well, that is why I recently undertook a mundane task of making those T-nuts. My first time with steel.
I learnt a awful lot making these. My point is, make something simple to start with, take it slow, keep the speeds slow and work your way up.

Above all take tiny cuts, don't try to sink the cutter in and do it all in one pass.

But listen to the machine, it will talk to you..... :thumbup:

raynerd:
I appreciate everything you have said regarding safety. I have had the machine over a week now and I only turned it on for one minute to check the motor was still running after transport. I bought it because it had been well looked after and at a price that suited me, I`m in no rush to use it - but at the same extent - you can sit looking at it all day but if I don`t ask the questions I`ll never learn - the next step would then be turning it on.

I have no option but to wait for another few weeks before I try it as I need a collet set before I dare hold a cutter. I`m not trying to rush - things have moved fast - I now have three machines, but I`m learning, taking my time and doing my best. I need to start with the basics and that is why I am asking basic questions. Reading back over my post - I suppose I`m not necessarly asking "how would I make that part", I`m wanting to know the basics about how that part is made....just trying to learn! It is difficult with only books and the internet...

I mean simplify the first one - lets just say I wanted to turn a 0.5" ally block 8"x4" into a 0.5" ally block 2"x2".
Would I cut the excess by hand or cut it directly out of the block on the mill? Presuming I can set the block up square - would I mill the edges true with the side of the end-mill with the piece on an overhang or would I hold the piece vertically on vice and use the end of the endmill?

It is these sort of basics I want to know .... I`m no-where near the mill yet.

Darren:
Cut it down nearer to size with some sort of saw first, milling is slow  :thumbup:

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