Starting out and looking for help and resources

Hi All

I'm just starting out in machining and am going to get myself a manual mill as I like the idea of creating pieces by hand. My main reason is to build my own dive gear so I'll mainly be machining plastics at the start (Delrin) and I have a couple of questions about the mill I should get and the equipment I need along with more specific ones about plastic feed rates and cutting speeds.

Firstly the equipment I am thinking of getting is a standard mini-mill, DRO's, Rotary table, and then the milling bits and consumables.

In relation to the rotary table I have a question as one of the pieces I may be machining will be about 180mm (7 1/2") in diameter but the rotary tables that fit on the mini mill are about 4" diameter so that leaves a massive discrepancy. Are there jaws available for a chuck that essentially overhang the exterior radius of the work piece so you can hold larger pieces in a smaller chuck? Would this cause vibration issues even with soft plastic?

Secondly if anyone has any tid-bits of info, or can direct me to useful guides on the web about cutting speeds and machining Delrin, the types of tools to use etc I would greatly appreciate it.

Cheers

Jools

jools said:

Secondly if anyone has any tid-bits of info, or can direct me to useful guides on the web about cutting speeds and machining Delrin, the types of tools to use etc I would greatly appreciate it.

Cheers

Jools

Click to expand...

Dont buy a mini-mill.
They are essentially junk except for model-making/watch making sized work in plastic and aluminum only.

You will discover its limitations and outgrow it very quickly.


Yes you can find lots of videos on youtube where people made acceptable stuff with a mini mill....but what they didnt tell you is it took them 10 times as long as it would have on bridgeport sized mill.

THEY SUCK.

"But they are within my budget and it will be good enough for my needs."
NO IT WONT.
THEY SUCK.

"But I can buy a NEW mini-mill for the price of used bridgeport, so it will be more accurate"
NO IT WONT.
THEY SUCK.

" I dont need a full size mill "
YES YOU DO.
THEY SUCK.
DONT GET ONE.

"But Im just...."

THEY SUCK.
DONT GET ONE.

"But..."
THEY SUCK.
DONT GET ONE.

The thing you need to understand about the "work envelope" of any machine is that if you are using all of it, you will be working very, very slowly. And if there are any other difficulties, like working with a difficult alloy, then it is going to be almost impossible. There is an old saying in machining work, everything is made of rubber. That mini-mill is more like foam rubber when you are attempting work like this.

I have a 10 inch rotary table. It is great for work that is up to about 6 inches. Yes, I can do larger stuff. But it gets harder and harder to do so. Ideally, you really want to have a machine and accessories that can hold work that is around twice the size that you will be working on. You are talking about going the other way with a 7.5" part on a 4" rotary table. That's almost twice the size of the table. Anything beyond drilling holes is going to be real difficult and slow. And just HOW are you going to hold that part on the table? Some kind of fixture? You will need to make that. Bolts through holes in it? Glue? Magic? The extra diameter of a table is often used for clamps. It is often NEEDED for clamps.

If you are serious, I would look for a full sized mill on the used market. And a larger (8 or 10 inch) rotary table. Seriously.

See Machinery Discussion Guidelines sticky thread for why this was locked.