Chamfering holes.

MarsFab

MarsFab

Will work for money
Joined
Oct 24, 2007
Location
Harrisburg, NC
What do you fab guys use to chamfer holes in metal? I've tried countersinks 6 flute, single flute, no flute. I've tried uni-bits. I've tried small hand de-burring tools. I've even tried custom grinding my own larger bit. No matter what tool I use I can't get a clean finished hole especially in aluminum. I always end up with a flared ring around the hole where the cutting tool rolls up an edge.
This becomes a pretty irritating problem when you build something out of nice clean un-scratched aluminum and the holes need to be sanded to get the rough edge off of them. I can't sand it. That's the whole point in using clean metal.
 
Strange. I did a quick google to try to find a picture of the bit I used to do 256 holes for my old beadlock rings with no luck. I really don't think it was anything special but now that I can't find it I'm wondering. I borrowed it from a friend that inherited a machinists collection of tools:eek: I may still have it. I didn't have any flaring with the metal but some with the aluminum. Thinking about it, I'm also wondering how you would get a clean cut on aluminum like you want. That was useless, I know:flipoff2:
 
A good zero-flute, slow rpm, and a pretty forceful feed should get you there. Don't let it run. That's where the ridge should be coming from. I have good luck with this approach on stainless. The chip may still try to scratch a little. You can use masking tape on the hole to help with that.
 
3003 is the worst obviously. I switched to 5052 just for this reason and it helped some but not enough. I've tried slow rpm's and both single and 6 flute. Even a brand new sharp USA made cutter has the same effect. Seems as if I need a flatter angle. I think I'll try a counterbore next. Maybe just a touch will flatten it out.... Maybe.... Unfortunately I'll have to have a full set for every size hole though. That's gonna get pricey!
 
Yes. Used to use wd40. Then switched to stp stick wax which is awesome stuff just not awesome enough for this lol. No it's not annealed. Don't really wanna have to anneal everything I work with.
 
I've always used a single flute fed pretty quick/hard with slow rpm to get the finish I was looking for, at the last little bit, pecked it with the chamfer a few times and it was good.
 
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6 flute low speed is about the best cut quality I can get.
 
I usually use a four flute 90 degree HSS, just like everything above. Fast hard feed fairly slow rpm with cool tool 2 for lube.

Anything else I use the one pictured below with adjustable stop collar for flat head skid plate bolts to drill hole and countersink to a repeatable depth in one step. Came from mc master and I ground corresponding flat spots on dedicated bit for set screws.

ImageUploadedByTapatalk1395846804.195781.jpg
 

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Ahhhh gotcha . Because usually with thin aluminum and drill bits things get ugly as the hole matches the flutes and gets a burr on one side or both?

Thick aluminum .250 and up I always use regular drills but for .188 and down I drill 1/8 pilot hole and use single flute step bit and barely chamfer each side with next step in bit.

Are you doing a single diameter often or multiple size holes often?
 
Predominantly .25, .375, and .5". Step bits do work decent but using the same step over and over on panels and what not usually kills them pretty quick even on aluminum.

Depending on the size of the hole I'll usually drill a pilot to keep the hole shape nice and round. .5" holes will come out octagon shaped if the bit doesn't have a perfect tip or if the material is thinner than the angled face of the cut.
 
I know you like building your own tools, have you thought about building a punch just for all the reasons above.

I paid $46 per size to get a new punch and die, at that price in the long run may be more economical than drill an step bits. Just build your own punch. I don't remember the last time I punched holes in any aluminum, but I'm curious how bad it forms a burr on the backside. I'll try it this evening and post some results.

I had a tonnage chart set up for my 20 ton shop press that showed what size hole I could punch in what thickness steel.

Just trying to think outside the box.
 
Have you tried a zero flute? The ones with a through hole? Also, what are you backing that material up with? The thinner aluminum might be flexing enough to create rub.

Sent from my XT907 using Tapatalk
 
catfishblues said:
Also, what are you backing that material up with? The thinner aluminum might be flexing enough to create rub.
Click to expand...

This. It looks like you are doing it in a drill press by hand, and the material is walking slightly. What is the RPM of the low speed?
 
We use these at the shop. Low-medium speed medium-heavy feed. Aluminum is the worst for rolling a bur, we use 6061 and 7075 high grade stuff so it deburrs pretty good. We have cutting oil just for aluminum, it's medium weight and green in color. Has a funny smell when it gets warm. I can't remember the name right off hand. I will look tomorrow and see if I can find a can.

http://www.moderntoolsupply.com/1-1..._content=pla&gclid=CIWShZiesb0CFQ8OOgodrDIAQg

EDIT: Just went back and looked at your pictures. That thin stuff is even more difficult to deburr because it deflects and vibrates. Make sure it is on a firm surface when you try to deburr. May need a table with a hole in it just larger than your thru hole and deep enough to clear the tip of the chamfer tool.
 
Mac5005 said:
I know you like building your own tools, have you thought about building a punch just for all the reasons above.

I paid $46 per size to get a new punch and die, at that price in the long run may be more economical than drill an step bits. Just build your own punch. I don't remember the last time I punched holes in any aluminum, but I'm curious how bad it forms a burr on the backside. I'll try it this evening and post some results.

I had a tonnage chart set up for my 20 ton shop press that showed what size hole I could punch in what thickness steel.

Just trying to think outside the box.
Click to expand...

:) I always need a reason to build another tool! :evilgrin: I may just do that. It'll probably need a 40" throat though. I may see a new combo bead roller deep throat punch build in my near future. Hmmm....
 
catfishblues said:
Have you tried a zero flute? The ones with a through hole? Also, what are you backing that material up with? The thinner aluminum might be flexing enough to create rub.

Sent from my XT907 using Tapatalk
Click to expand...
A zero flute is what I was using originally. To me it seems like the less flutes the more solid face area to mushroom the material. But.... In theory slow enough speed should truly only take one to two revolutions to de-burr the hole I suppose. I haven't actually thought about using a backer plate. Have to try that good idea
 
What about a knockout?
 
Kamel said:
This. It looks like you are doing it in a drill press by hand, and the material is walking slightly. What is the RPM of the low speed?
Click to expand...
Yep usually a hand drill. Normally the panels and what not are larger than the throat of my drill press will handle. If I had to guess maybe 60rpm or one revolution or less in a second.
 
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