Good, cheap, material to practice with?

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dorin
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Good, cheap, material to practice with?

Post by dorin » Mon Jun 27, 2016 10:46 am

I just got my little CNC sherline going!

I have been practicing with this things like this:
1) Insulation http://www.homedepot.com/catalog/produc ... da_400.jpg
(This works ok, but tends to wrap around the cutter. )

2)old PC boards.
(Which I understand will dull my cutters quickly...but they are plentiful in my house and seem nice to work with)

3) I have also messed a bit with MDF, but boy does that make a mess.

Any suggestions...Looking for something cheap that machines sort of nicely to practice with.

THank you!

-Mike
www.chaski.com

hammermill
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Re: Good, cheap, material to practice with?

Post by hammermill » Mon Jun 27, 2016 11:09 am

cant speek for cost but they sell a wax that is quite firm and can be remelted many times to test set up


http://www.machinablewax.com/_cw4-tmplt ... W_Logo.jpg they may give some ideas.

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SteveHGraham
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Re: Good, cheap, material to practice with?

Post by SteveHGraham » Mon Jun 27, 2016 2:37 pm

Do not try my first "free" test material: a piece of an old leaf spring.
Every hard-fried egg began life sunny-side up.

Harold_V
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Re: Good, cheap, material to practice with?

Post by Harold_V » Mon Jun 27, 2016 2:49 pm

One thing to consider is that machining soft and easily machined material will not teach you the things you need to survive the real world. If you get familiar with the easy to machine things, when a demanding project comes along, you may not have enough input to understand that what you learned doesn't really apply to the project at hand.

Fiber glass boards are very abrasive. They machine reasonably well with sharp tooling, but wear reduces the cutting edges rapidly.

I'd recommend that you machine materials in keeping with your intended usage. If you hope to machine boards, stick with them, as that's most beneficial for your purpose. I recommend carbide cutting tools, however, as they resist abrasion far better than HSS.

Mild steel is one of the not-so-fun materials to machine, chiefly because it likes to tear, so surface finishes can suffer. If you master mild steel, pretty much anything else will be no greater challenge, excluding some of the exotic alloys that are notoriously difficult to machine (like titanium).

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

dorin
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Re: Good, cheap, material to practice with?

Post by dorin » Mon Jun 27, 2016 3:51 pm

Harold you do make a good point!

That sure happened last week...We practiced with plastic and foam..then through aluminum in and broke the bit right away!

-Mike
www.chaski.com

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tornitore45
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Re: Good, cheap, material to practice with?

Post by tornitore45 » Mon Jun 27, 2016 6:23 pm

I suppose the reason for a test run is to validate the program motions, obviously a soft material will not validate feeds, speed and rigidity of the set up.

I recall seeing a post somewhere how to make homemade machining wax by "cooking up" paraffin and grocery plastic bags.
A Google search should find the recipe, if you are going that way.
Mauro Gaetano
in Austin TX

dorin
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Re: Good, cheap, material to practice with?

Post by dorin » Mon Jun 27, 2016 6:32 pm

I actually gave that a try a few years back..and am digging around for the product of my labor!
I know I have some of that stuff ...somplace!

If you do try making it...make sure you have a strainer...the grocery bag print gets really stringy.

-Mike
www.chaski.com

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ctwo
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Re: Good, cheap, material to practice with?

Post by ctwo » Mon Jun 27, 2016 8:08 pm

I've seen folks melting HDPE (empty milk jugs, etc) and similar plastic in the oven, then pressing it in a mold.

I've tried plastic 2x4 (or landscaping edging) from Home Depot and it was not very homogeneous - had parts of stuff that did not melt into the mix. It might work OK just for practice.
Standards are so important that everyone must have their own...
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Disclaimer: I'm just a guy with a few machines...

Harold_V
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Re: Good, cheap, material to practice with?

Post by Harold_V » Mon Jun 27, 2016 9:51 pm

dorin wrote:Harold you do make a good point!

That sure happened last week...We practiced with plastic and foam..then through aluminum in and broke the bit right away!

-Mike
That's what I'd expect, Mike. Non-metallics tend to be quite forgiving, often machining with almost no effort, and they generally don't weld to the cutter, although some plastics may do so because of heating. A switch to metal, even aluminum, where lubrication is important, often leads to broken tooling.

Aluminum is generally pretty forgiving, but if you machine dry, there's a buildup of aluminum on the cutter, which rapidly leads to loading of the flute. You end up with a well bonded buildup that fills the flute completely to the depth of the cut. Once that happens, you have but a moment to save the cutter, especially if it's small in diameter. Use kerosene or WD-40, brush applied is fine, while cutting, and if you can, clear the chips, especially if you're in a deep cut. I use air, but some folks prefer to not do so.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.

WJH
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Re: Good, cheap, material to practice with?

Post by WJH » Tue Jun 28, 2016 10:30 am

ctwo wrote:I've seen folks melting HDPE (empty milk jugs, etc) and similar plastic in the oven, then pressing it in a mold.

I've tried plastic 2x4 (or landscaping edging) from Home Depot and it was not very homogeneous - had parts of stuff that did not melt into the mix. It might work OK just for practice.
At the GGLS, we used that plastic lumber for ties, you wouldn't believe the amount of nails and metals that find their way into it!

DavidF
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Re: Good, cheap, material to practice with?

Post by DavidF » Sat Jul 02, 2016 11:24 am

Go to a kitchen counter top place and see if they will give you some corian scraps.....

12L14
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Re: Good, cheap, material to practice with?

Post by 12L14 » Sun Jul 03, 2016 8:30 pm

POM is pleasant to machine, but nowhere near cheap...
Modern butchers blocks(thick cutting boards made of polypropylene or - most often - polyethylene) are not so pricey, but nothing beats DIY machinist wax.
Didn't try one out of HDPE yet - only LDPE so far(basically same thing except slightly different ratio to paraffin wax).


http://www.weaponeer.net/forum/forum_posts.asp?TID=8978
Tool&die maker since yesterday ;)

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