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View Full Version : Some thoughts on machining various materials using a router



Rustybolt
12-26-2008, 11:04 AM
I recently tad to machine the perimeter of an alum disk 3/4 of an inch thick and five feet in diameter. It had a 1&3/4 in shaft in the middle , but the rim was - as cut. I built an arm to mount the router out of a shaft collar and some flat stock. Adjustment was through two 1/4-20 screws in elongated holes. Fine adjustment was done using scribed lines on the mating angle that held the shaft collar and the flat that held the router.
Using a 1/4 HS right hand spiral right hand cut two fluke bit the aluminum cut very easily as long as WD40 was sprayed ahead of the work. The shaft that held the disk was clamped so that the disk wouldn't rotate and keeping tension on the arm and walking compleatly around the disk without stopping , there was only a tiny divot where the cut ended. Granted it is not for reducing the diameter to a precise amount , but in this case that wasn't neccessary. Our only requirement was to get a good 90 deg. refrence from the top to the circumfrence.
The other material was fiberglass reinforced garolite(phenolic)3/8 of an inch thick. I don't reccomend using HS on this material at any time. Again I had to make a disc out of several square pieces and the circumfrence had to be 90 deg to the top. the diskes were 24 inches in diameter once roughed out on the bandsaw the bandsaw blade was dull and had to replaced. Again a router was used and carbide two fluke endmills were used. They quickly became dull. A diamond burr was then used to rough cut the edge and that worked very well. Heavy cuts (1/8 of an inch) could be taken. The finished edge was done with a carbide rotary burr taking very light cuts. This worked well and did not appreciably dull the burr.
On graphite reinforced phenolic it is possible to use HS as long as it is sharp. It does dull the tooling, so if there is going to be a lot of production , use diamond tooling if the cost warrants it. If not then Carbide will do.
The dust from either of those phenolics is nasty so I had a vacuum cleaner setup next to the bit to collect the dust.
This is just a heads up to anyone contemplating using this stuff. Hopefully someone will find it useful.

darryl
12-26-2008, 06:19 PM
Done that myself. It's very satisfying to be able to rig up something to do the job, even as unorthodox as it may seem. Have not worked much with FRGP, but I can appreciate the difficulty keeping cutters sharp.

I've cut quite a few discs out on the table saw. The main requirement is to be able to attach a pivot point to a suitable place, and be able to support the disc so the blade can be raised through it in successive passes as the blank is rotated by hand. I once cut out a 4 ft diameter disc from mdf on the table saw. By paying enough attention to the process, you can get a very good result which actually is a milled edge.

I like to use carbide skil-saw type blades on the table saw, with stabilizing washers mounted alongside them. They are cheap enough that when required you can just throw a new one on and not worry about damaging it or getting a sorry cut because the blade was dull. The smaller diameter blade also doesn't need to take out as much material when carving a disc out in this way.

Scishopguy
12-27-2008, 11:47 AM
I have had several occasions to use the router as a hand portable mill. I had to make a rather large plexiglass tank for wave modeling. It was 2'x2'x16' long and was made from 5/8" cast acrylic sheet. The tank was made from 4'x8' sheets and joined in the middle. I used an 8' straight edge, clamped to the slabs and adjusted the cut using a depth mic, a 24" mic, and an edge following attachment. I found that by using a single flute carbide cutter and limiting my cuts to .015" per pass it cut just like the mill and left a clear finish. It took me a couple hours for each pannel but worked like a champ. There is no way I could have done this job on the BP without start and stop lines. Besides, even then I was getting too old to horse those pannels about without help. :D

topct
12-27-2008, 12:56 PM
More router fun,
http://img.photobucket.com/albums/v78/topct/Track.jpg

BobWarfield
12-27-2008, 04:16 PM
More router fun,
http://img.photobucket.com/albums/v78/topct/Track.jpg

Yo, my Pantera antennae are raised. Do you have one?

Best,

BW

Scishopguy
12-28-2008, 07:36 PM
Nice looking track, man!!!

topct
12-28-2008, 08:45 PM
Nice looking track, man!!!

Thank you. I thought it might be on topic as far as cutting various materials, and using a router. Did all the slots with just one carbide bit. HSS would burn up on just one turn. That's high density particle board and it's murder on bits.

It was also very scary to bend. The turns had to be pulled into that shape.

dixdance
12-28-2008, 09:12 PM
20 years ago I saw a big Martin table saw which had a narrow Starrett ruler inlaid in the cast iron table as a reference for setting the fence. It was actually slid into a very shallow dovetail groove, which the guy had made with a hand held router running along a fence. He first cut a straight groove, and then went back in with the dovetail bit. I know he used regular woodworking router bits, don't remember if they were carbide, but seems like they'd have to be. Looked factory installed!

darryl
12-28-2008, 09:18 PM
Well, I did some trimming on cast iron with a carbide burr in a router. That part worked fine, though the project itself is moving along at the pace of frozen molasses.

Rustybolt
12-28-2008, 10:14 PM
Thank you. I thought it might be on topic as far as cutting various materials, and using a router. Did all the slots with just one carbide bit. HSS would burn up on just one turn. That's high density particle board and it's murder on bits.

It was also very scary to bend. The turns had to be pulled into that shape.

There is metal in HDP and to a lesser extent MDF.

Silverback
12-29-2008, 04:35 PM
20 years ago I saw a big Martin table saw which had a narrow Starrett ruler inlaid in the cast iron table as a reference for setting the fence. It was actually slid into a very shallow dovetail groove, which the guy had made with a hand held router running along a fence. He first cut a straight groove, and then went back in with the dovetail bit. I know he used regular woodworking router bits, don't remember if they were carbide, but seems like they'd have to be. Looked factory installed!

I've run into my cast iron table saw extension table with a 1/2" straight cutting router bit in my big freud plunge router and honestly, barely felt any change from the 3/4" MDF that I was cutting and got a seriously clean cut in the cast iron. The straight cutting bit doesn't seem to be any worse for it either.

derekm
12-29-2008, 07:49 PM
Routers are high speed spindles so all the rules apply.
Given carbide at 4000 to 35000 rpm this means:
ally upto 25mm dia
cast iron and carbon steel upto 10mm dia.

Holding it steady to do the cut is another matter.

j king
12-29-2008, 08:22 PM
I work as a mobile machinist now.This is crazy but I milled a 1/2 keyway in on a coupling using a router.I made a jig up and had used a carbide endmill.It came out perfect.Held .002 tolerance.Wished I took a pic.

oldtiffie
12-29-2008, 08:48 PM
A good industrial router is a rugged precision tool. This is mine:
http://www.triton.com.au/product.php?id=27

Using spiral-fluted metal-machining end-mills will work fine as the reaction of the cutter under load is to pull the work and cutter toward or "hard-up" against each other - which helps no end!!

Using (non-spiral fluted) "wood" TC dove-tail or other cutters on cast-iron or brass works fine as even at "zero" "Hook angle" (aka "back rake") but the "hook" is often quite larger (up to 20 degree).

The router really needs to be "taken charge of" as it is very powerful and fast and can cause a lot of damage if it "gets way" (from you) as it isn't the least bit fussy about what - or who - it cuts!!!

With a bit of thought it can make very versatile portable milling head.

Greg Parent
12-30-2008, 12:56 PM
I made the mistake of taking a 1 HP table mounted router off its base to router some slots in a piece of lumber that would not fit the permanent fence setup on the table router. Everything was going fine until I hit a knot. Let me be the first to tell you that I cannot hold a 1 HP router at full rev. It grabbed into the higher density knot and yanked itself out of my hands and flew across the shop. All my co-workers looked over, shook their heads and went back to work. I did hear a little muttering of unrepeatable words under their breath. They probably remembered the "Flying Plywood Triangle of Death" tablesaw incedent when I first started in the shop and added this mishap to the long list of my screwups.