Removing work-holding tabs - and finishing

[FoxCNC1]

Hello everyone,

I have been cutting Alum, with my CNC router which some good success (profiling). The cut finish is okay but could be improved, and part of the marks I see are sometimes due to the multiple steps I am using to separate the part.
I know I can always go back and so a "spring pass" or a full depth finishing pass at a very slow feed. Regardless, my biggest challenge is removing the tabs I am using to hold down the parts.

I found these threads which suggest to drill holes to screw the parts to the spoil board and not use tabs etc, but what happens when the actual part does not need or can't have any holes, or only has one hole.
http://www.cnczone.com/forums/genera...53881-cnc.html

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[alan_3301]

use a straight flute brazed carbide bit with a bearing on the end. let the bearing ride on the finished surface, and the bit will remove what's left of the tabs.
Get a bit smaller than your part's smallest inner diameter to make sure the bit will reach all areas you need, or make sure the tabs are accessible with the bit you choose.

[FoxCNC1]

use a straight flute brazed carbide bit with a bearing on the end. let the bearing ride on the finished surface, and the bit will remove what's left of the tabs.
Get a bit smaller than your part's smallest inner diameter to make sure the bit will reach all areas you need, or make sure the tabs are accessible with the bit you choose.

This is a manual process isn't it?

[alan_3301]

I don't have a router table or handheld, i just put it on the cnc, and move the part by hand.
A fence helps a lot with flat edges, to help keep the part straight and flat, safely.

It's probably not the safest way, and I wouldn't do small parts that your fingers get anywhere near the bit.

[diyengineer]

Use .005" tabs, razor knife them off, or like suggested use a router to take them off. That is how they do it at my work, and yes all manual. don't use tabs if you don't need them. If you have holes in your part of any kind bolt it down.

[FoxCNC1]

The problem is that one part I have been making one has one hole and is a triangle. (hole at near the base).

[siggma]

Hello everyone,

I have been cutting Alum, with my CNC router which some good success (profiling). The cut finish is okay but could be improved, and part of the marks I see are sometimes due to the multiple steps I am using to separate the part.
I know I can always go back and so a "spring pass" or a full depth finishing pass at a very slow feed. Regardless, my biggest challenge is removing the tabs I am using to hold down the parts.

I found these threads which suggest to drill holes to screw the parts to the spoil board and not use tabs etc, but what happens when the actual part does not need or can't have any holes, or only has one hole.
Need Help! Work holding

Definitely use tabs to hold work while cutting. I use a 3D tab about 1/16" to "1/8" thick about 1/4" long, depending on whether I'm using an up or down cut mill to cut the profile. Then easy as can be chuck up a flush panel trim bit in the spindle, spin it up to 10,000 rpm, run the bearing end (Z axis) down against the spoilboard or any height that runs the bearing below the tab thickness on the workpiece and using the spoilboard as a router table those pesky tabs fly right off. Even if you use a nasty keyhole saw to cut the tabs... Others suggest difficulty removing the part without the tab or trying to use the panel bit to remove the part but it's very easy to cut the tab on the "spare" or "spoil" side of the work leaving as much of the tab on the piece as is easy, then use the panel trim bit to remove the tab. Works well even on small parts. I ended up with numerous panel bits that came as part of a set (Ryobi?) that work fine for this, even the gigantic 3/4" monster bearing flush bit. What I have done is use my spoilboard as a router table on many occasions. It's useful for cutting a dado without a program or cutting form edges in trim without having to come up with an elaborate way to attach small stock to cut moldings or whatever.
Just a thought...

[FoxCNC1]

Definitely use tabs to hold work while cutting. I use a 3D tab about 1/16" to "1/8" thick about 1/4" long, depending on whether I'm using an up or down cut mill to cut the profile. Then easy as can be chuck up a flush panel trim bit in the spindle, spin it up to 10,000 rpm, run the bearing end (Z axis) down against the spoilboard or any height that runs the bearing below the tab thickness on the workpiece and using the spoilboard as a router table those pesky tabs fly right off. Even if you use a nasty keyhole saw to cut the tabs... Others suggest difficulty removing the part without the tab or trying to use the panel bit to remove the part but it's very easy to cut the tab on the "spare" or "spoil" side of the work leaving as much of the tab on the piece as is easy, then use the panel trim bit to remove the tab. Works well even on small parts. I ended up with numerous panel bits that came as part of a set (Ryobi?) that work fine for this, even the gigantic 3/4" monster bearing flush bit. What I have done is use my spoilboard as a router table on many occasions. It's useful for cutting a dado without a program or cutting form edges in trim without having to come up with an elaborate way to attach small stock to cut moldings or whatever.
Just a thought...

That is pretty ingenious. Its basically and upside down router table what you are describing.
so you are flitting the part upside down right? (never used one of those bits)

[siggma]

Yes, that's it exactly, an upside down router table. And if you don't have a good panel bit, here's a nifty 3/16ths panel trim although it's a tad spendy for just trimming tabs but it all depends on how and how many you use of them I guess.

Amana MR0105 Flush Trim 3/16.

Oh those clever boys at Amana... I can probably even make a video when I get a chance. I have a very cool circular, clamp-on LED light that's perfect for filming such events. Now I just need to find my camera and tripod...

[siggma]

Yes, that's it exactly, an upside down router table.

Something I didn’t think of before. You could just as easily use a laminate trim bit if your parts are difficult to flip over so the tab is above the bearing.

I think I have both so I’ll try a video. It’ll be good practice.

Tom


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[wmgeorge]

Depends on the job, on wood I use my bandsaw to cut the tabs and sand off the burrs. Metal could still be a metal cutting band saw, hand held power jig saw or Dremel tool. File or sand as needed.