Adventures in Milling; My machines want a new owner.

[Mark Lossner]

Your speed is kinda fast, It's great to use "book" speed if you know exactly what your cutting! I'd start slow (700rpm) and increase speed as required. If your end mill is burned you better to try another or cut deeper in the wood so that the steel is cutting with new sharp edges. 1008 is a low carbon steel, are you using 2 or 4 flute?

The cutter has four flutes.

Is the flutes clean of have chips stuck to them of jammed full? I think what was happening is you part was lifting and probably damaged the tip of the mill.

The chips do get packed in pretty tight, and I had to use the point of a scribe to dislodge them.

Your better off Milling the other way. Turn the piece 90 degrees, use something better than wood on the bottom and use a long piece of steel along the full length of the cut same as you have on the bottom, End mill will lift the work. I see that you are feeding down, start with the mill thru the work and move in rather than down.

This all makes good sense. The table won't move in-and-out enough to mount the work the other way.

Thanks for such detailed answers.

Mark

 

[george wilson]

Have you tried climb milling? It gives a MUCH better finish on aluminum. Also,pay attention to the feed & speed suggestions and use a larger end mill.

I haven't used 1008 steel. ,do you mean 1018? I can tell you from experience working in a museum,that cutting genuine WROUGHT iron is messy,and 1008 is VERY low carbon. Wrought is no carbon,and it is gummy to file or machine. Perhaps get some higher carbon steel? 1008 means .08% of carbon. That is very low.

 

[Mark Lossner]

Your .54" per second figures to 32.4 inch per minute. Calculated at .002" chip load you should have had a feed rate of about 10"-10.5" per minute which means you were feeding it around 3X to fast.

I could only turn the handle at one second per revolution. That should have been only .1" per second. I bet that was still too fast. Please tell me more about calculating with "chip load". That might be the key to the problem. (So is the sheet hold-down technique, no doubt.)

Sheet metal usually machines badly but with your feed rate you made it worse.

I seem to have captured a record. )

Mark

 

[Mark Lossner]

Have you tried climb milling?

I will give that a try.

Thanks,
Mark

 

[george wilson]

See my edited post above,too.

 

[Mark Lossner]

...I haven't used 1008 steel. ,do you mean 1018?

Fair enough question. Here is a link to the spot that sourced the material:

http://www.onlinemetals.com/merchant.cfm?pid=12780&step=4&showunits=inches&id=944&top_cat=197

Mark

 

[Mark Lossner]

...I haven't used 1008 steel. ,do you mean 1018?

I thought I replied to this, but I did link to "Online Metals" to show you the specs of the sheet. Maybe it was sent down the rat hole.

I'll try someting else:

If you need some help deciding if this is the right material for you, consult our new Product Guides. There is a wealth of both technical and non-technical material that will help you in deciding which materials to buy. Click here for the mild steel guide.

Hyperlinks were disabled:
[TABLE="width: 0"]
[TR]
[TD]

• 0.0239" (24 GA.) MILD STEEL A366/1008 COLD ROLL SHEET
• 0.0299" (22 GA.) MILD STEEL A366/1008 COLD ROLL SHEET
• 0.0359" (20 GA.) MILD STEEL A366/1008 COLD ROLL SHEET
• 0.048" (18 GA.) MILD STEEL A366/1008 COLD ROLL SHEET
• 0.0598" (16 GA.) MILD STEEL A366/1008 COLD ROLL SHEET

[/TD]
[/TR]
[/TABLE]

 

[Mark Lossner]

One thing to remember is the speed chart on the mill is never correct! ... so I'm guessing 1800rpm. Speed charts are usually calculated at name plate rpm so you running at a fast speed than you think!

Hmmmm. I will find a tach and check this. Good call. Chinese motor, methinks.

Thanks,
Mark

 

[McRuff]

Chip load is based on the type of cutter you are using and the function you are doing. HSS versus Carbide or treated endmills, versus side milling, plunge milling and the profile of the cutter. Cutter manufactures can give it to you. There are also some charts in the machinist handbook. Here is a reference chart (table 2) to use if you do not have a machinist handbook. This will help you better calculate the feedrate. I heard this years ago when serving my apprenticeship, good rule of thumb for chip load was never to exceed 1% of the cutter diameter, so for a .250 endmill, .0025 per tooth would be the max amount, I always round it down as a starting point.

http://its.foxvalleytech.com/machshop3/speedcalc/feedratecalc.htm

 

[November X-ray]

Hmmmm, This makes me think CNC Plasma would be a viable tool for this job!