Milling, Drilling and Tapping .75" Thick Fiberglass...

[Cyre]

I have a project here at work coming up that requires I mill the periphery, drill and tap holes for inserts in .625 thick fiberglass. I am a relatively new machinist (just over a year) and this will be my first encounter with this material. I have searched the net for info, but came up empty and the only person here that has milled any fiberglass didn't have to drill and tap. I'll be using a Mazak Nexus 510 VTC.

Does anyone have any tips and pointers or know of a web page with some info?

Thanx in advance!!

[Chuck Reamer]

Hey there I have milled a bit of fiberglass, and turned lots of it.

The milling was done on a cnc converted First vertical mill. Not quite a Mazak to say the least. I had to do some drilling and hand tapping on a few parts. It drills and taps nice, just use sharp tools all around.

Solid carbide 4 fluter's work well, try using aluminum feeds and speeds should work pretty well. How many parts do you have to do? Use a solid carbide or powdered metal drill if you have more than a half dozen holes. Super abrasive and will do a real number on HSS. If you have a lot of holes to do you may want to price out a solid carbide tap as well.

Don't run coolant or an air blast, when the cycle is done use a shop-vac to get rid of the dust. If it is a large run you may want to have the vacuum hose rigged to the mill table. Running it while machining should work well if there is a ton of dust.

I wear those big white Tyvek coveralls when I am turning the stuff on a manual lathe. Blue nitrile gloves are a must, latex makes your hands sweat like hell. I also wear a respirator if I am getting serious about making a mess.

Your tools will be dusty and it never seams to all clean off. I just ordered a Brown & Sharpe IP67 caliper and cant wait to test drive it.

[naytep]

I have machined it on several ocasions. I found that carbide bur type cutters leave the smoothest edge. I run them high rpm (1/4" = 10k) and feeds around 25ipm work well. As far as driling and tapping use the same theory. Like the previous post said, if you are making more than a couple holes go to a carbide tipped or solid carbide drill and tap. Considering the cost of c'bide taps you may want to try a coated HSS or Cobalt tap. MSC has many drills and cutters designed for fiberglass.
Good Luck

[Cyre]

It's just 2 parts, 7" x 18", each with 12 tapped holes for 3/8-16 keylocked inserts and 6 tapped holes for 1/2-13 keylocked inserts.

I appreciate the help!

[naytep]

Invest in the carbide to mill the outside. I am sure you can get away with the HSS drill and taps for the holes.

[JROM]

The main enemy when cutting fiberglass or and plastic or composit material is heat.
That said alot of these materials are porous so you can't use cutting oil or coolent or
you ruin the parts. Try using a light air stream and a vacuum to collect the chips and dust. You don't want to breath this stuff of get it on your body! I've used cold air guns on composit materials with a lot of good results. The cold air saves the tools making them last a lot longer because they don't get hot. Good luck!