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Machining aluminium - what grade do I need ?

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Phil Catchesides20/04/2017 13:42:00
71 forum posts

Needing some good quality ali for con rods I begged a pair of redundant bike cranks from a friend and set to work on the vertical mill. I quickly got a problem which looked like the ali was 'melting' onto the cutter (a 3/16 slot drill running at about 2500 rpm) when doing a .050 cut. No lubricant was used but I had no problems drilling. Was I doing something wrong (speed, cut ?) or what grade of ali should I buy from where ? I would need about .5" square (or .75 round) by about 2" long to make each con rods from. I have recently done the crankcase nose in unspecified ali with no issues

Emgee20/04/2017 13:50:41
753 forum posts
155 photos

Hi Phil

You don't say what type of motor but HE14 or 7075 are both used for model engines and easily machined, you may get away with 6082, I would suggest some kind of lubricant is used to prevent build up on the cutter.


spelling edited

Edited By Emgee on 20/04/2017 13:51:41

JasonB20/04/2017 15:53:13
12318 forum posts
1095 photos

Most model conrods are spec'd with HE15 which is 2014 and that is what I tend to use on them. A bit of paraffin or WD40 will help stop the metal sticking to the cutter and I generally don't run as fast.

College Engineering or M-Machine will have 2014 in those sizes, round seems to work out cheaper than square/rect section


Edited By JasonB on 20/04/2017 15:54:46

Emgee20/04/2017 16:23:12
753 forum posts
155 photos
Posted by Emgee on 20/04/2017 13:50:41:

Hi Phil

You don't say what type of motor but HE14

Should have been HE15 as Jason says, NOT HE14, my error.


JasonB20/04/2017 17:58:17
12318 forum posts
1095 photos

Think it is his Matador. At the time that was published they may well have said "Dural" on the drawing. HE15 (2014)being about the same.

John Reese21/04/2017 03:44:03
478 forum posts

Aluminum does tend to weld to the tool if cut dry. I use a spray bottle with soluble oil. The occasional squirt seems to be adequate. I have tried an inexpensive mist coolant outfit but is is more trouble than the spray bottle. If you work a lot of aluminum you should consider a polished flute endmill designed for aluminum.

Ian S C21/04/2017 11:02:26
6698 forum posts
219 photos

I made a con rod from a bike crank a few months back, the small amount of milling work done was at a fairly modest speed(can't remember what), the tool used to bring the bulk to thickness was a 2" 3 cutter face mill, finish, smooth as, virtually a polished surface.

Ian S C

John Durrant21/04/2017 15:54:49
44 forum posts
4 photos

Diesel makes a good lube for aluminium, apply it with a brush.

Neil Lickfold23/04/2017 00:03:04
362 forum posts
45 photos

2024 is also very good for conrods. It is important to have the grain of the material in the direction of the rod. Can't really fail with round bar, but sheet stock, some suppliers just cut material from the sheet in the most convenient for them situation. A cross grain rod will fail, especially if it is 7075


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