View Full Version : Milling Fiberglass
12-19-2010, 02:07 PM
Have a project to make some parts out of a fiberglass sheet.
From what I can get off the tubes it is very abrasive and it eats endmills up at a impressive rate. I have read that Carbide is the endmill of choice but some argument about the feed and speed.
I also have come across Diamond cutters (like the ones you get for a dremel tool) to cut Fiberglass.
Of course the fibers produced is nasty and keeping that under control is of the utmost importance. (will have a vac setup and wear a mask)
suggestions on what cutter to use? Carbide? other coating? 2,4 or more flute? Diamond cutter?
12-19-2010, 02:49 PM
Printed circuits board manufacturers use carbide bits for drilling and milling PCB's. They are usually small diameter at run at high Rpm's. If I recall 80k plus. You can find the cutters on EBay.
Or try a local manufacturer. They usually run them for so long then either resharpen or replace. I did a quick google search and there seemed to be several good answers. Sometimes the bit are burr like instead of end mill like.
12-19-2010, 02:57 PM
We used to use a 1/4 inch shank straight carbide cutter with a spiral pattern of broken up teeth- seemed to go a fair distance before they got dull. Don't doddle- when it is cutting, follow it fairly quickly. The bigger the chunks taken out by it, the longer it will last. You do need a good mask. I find the annoying white nose cover elastic band types not so good. Try to vent the outlet from the vacuum system outside if you can. There's lots of very fine dust produced, which you'll find laying on everything in the shop. It will clog the vac filter easily, sort of like gyproc dust. It's a killer of brushed power tools, just like gyproc dust.
12-19-2010, 04:54 PM
My spindle will do 4K max.
I mostly have HSS endmills (broke 2!! 1/8" carbide end mills last week on one part.....:mad: )
will have to go pick some up.
Use carbide burrs for fiberglass. They work much better than regular endmills.
12-19-2010, 05:53 PM
Milled some fiberglass boat parts a few years back, found carbide four flute end mills new out of the box or freshly resharpened worked best.
12-19-2010, 06:28 PM
Fibreglass is a horrible material to cut. And, for that matter, to make.
A very good dust extraction system is a must. The dust is carcinogenic if inhaled. (And itches like crazy if you get it in your socks.)
I've not done any serious lathe machining of fibreglass, but a mate who was asked to turn some propellor shaft tubes gave up after a few passes and told the guy to take the job elsewhere. The dust and filth was too much for him and his shop.
My own experience with boat-building was confined to drilling with twist drills and hole saws, grinding with an angle-grinder (yuk!), and to cutting out for window openings, etc., in sheet fibreglass, for which I used a jigsaw (I think you Americans call it a sabre saw?) blade which had no teeth but rather a strip of carbide grains along the leading edge. That worked very well, and I still use the same blade after twenty years. The twist drills needed frequent resharpening, and the holes saws were completely stuffed after only one or two holes.
It is, after all, glass, which is kinda hard!
12-19-2010, 06:47 PM
You can get 1/4 diameter diamond studded cutters from McMaster-Carr. I use a heavy duty router and have someone holding the shopvac hose as you go around. The dust besides being tiny particles of glass the smoke from the resin is toxic.
12-19-2010, 09:46 PM
When I worked for General Dynamics/Convair in San Diego Ca., one of my last jobs was fitting the wing fairing for the AGM-129A Advanced Cruise Missile.
The fairing was an Aluminum and fiberglass composite requiring routing using an air powered router turning a 3/8" two flute bit.
The dust and noise was such that tyvex suits,ear plugs,goggles, and gloves were needed to control the affects of routing on a tool designed to fit the missile shape. This was a two person job that became not a favorite one to do.
A shop vac was used to collect the leftover Aluminum and fiberglass but even this did not work 100% as we had computer monitors in the area that would short out and have to be replaced usually after 30 days exposure.
12-19-2010, 10:30 PM
I use to do a lot of work with fiberglass. Carbide is your best choice. High speed steel cutters won't last 5 minutes. Diamond is not good fiberglass has resin some of it is epoxy and some is not. The epoxy with melt and get gummy diamond will get all clogged up.
12-20-2010, 08:34 PM
If you can use coolant on it, that would be best. I used to do retaining ring liners for large turbine rotors, up to about 3' high and 54" D, 1 1/2" thick, tapered, about 1" flange on the bottom.
They came to me on a mandrel (this was on VBMs) cock the ram to the needed angle. Flood coolant. Washed down all the dust from the glass and the resin.
Problem was that cutting pressure forced it down tighter on the conical mandrel, so backed out 5 thou or so every inch or so. Finish cut, was able to let the tool run, as it no longer was pushing it down.
That was with carbide inserts, I forget which, the insert was about 1/2" wide, 3/8 thick, 1 1/2 or so long, pointed like an elongated Home Plate, chip breaker groove along the cutting edge. One cutting edge, only, tho' you could sharpen them somewhat.
Funny thing is that the pay on them was lousy, raised hell with the IE. His retort? "Double the feed and speed." I couldn't make a good one with his calcs unless I cheated, and he wants me to double them.
12-20-2010, 08:51 PM
Consider using a respirator, rather than a simple dust mask.