[How do I?] Chamfering large hole on manual machine

[mmcmdl]

They make boring bars that hold cutters at 45 degrees , they came in all BP sets .

If you're worrying about chatter , step it down to 3/16" .

 

[BGHansen]

How consistent does the chamfer need to be? If it isn't for show, you could use a deburring tool (you'll be hard pressed to get to 3/16") for starters. I'm a big fan of pippin files. If it's just one part, maybe file it by hand. The pippin files have varying radii (section is in the upper LH corner of the image below). I find them much easier to use than a rat tail file. With rat tails I tend to go too deep and have more trouble blending along an edge. The pippin file has more contact surface and is easier to use in my experience.

Bruce

 

[mmcmdl]

This is what you would be looking for . I have 50 or so if you need one .

 

[Alexander McGilton]

Just to add a photo of what was said above. The people who modify cylinder bore encounter this problem regularly. Below they operator has mounted what appears to be a 1" dia chamfering tool in the boring head and running the machine backwards. You can place the the below style of 45deg in the boring head, on the right side, then you have an adjustable chafering tool.

Should you machine be under powered for taking 3/16" * 2^.5 chip engagement for this materiel you can take the cut progressively. Paint then scrip a line .1875 deep in the bore. Set the bring head .125 to .1875 under size radius. Set the quill stop to the full depth with the knee a little lower than needed, then take a fist cut full depth and bring then knee up to where the scribe line is met and the bottom most section of the chamfer is satisfactory and raise the quill. This is the interesting part, stop the machine to enlarge the boring head .010" (or more if confident) radius and lower the knee also .010", power on then lower the quill again to the stop. Raise the quill and repeat until the cutter is only cutting air. You will have taken multiple passes with progressively more tool rubbing of the lower section to make the one deep chamfer.

Some tips for dealing with chatter. Run the machine much slower than usual and initiate the cut with a quick jab of the hand wheel, followed by an aggressive feed. It sounds outrageous but it works, you want the machine to growl not sequel. Use thick tapping fluid as cutting lubricant.

http://www.centroidperformanceracing.com/images/block_cylinder_chamfering_600x450.jpg

Accusize Industrial Tools 3 pc Indexable Carbide Countersink Set 90 Degree, 1/4 Inch, 1/2 Inch, 1-1/4 Inch, 0046-0990: Amazon.ca: Tools & Home Improvement

Accusize Industrial Tools 3 pc Indexable Carbide Countersink Set 90 Degree, 1/4 Inch, 1/2 Inch, 1-1/4 Inch, 0046-0990: Amazon.ca: Tools & Home Improvement

www.amazon.ca

 

[projectnut]

There are several large diameter 45* countersinks available on eBay. Here are a few:

2" 45 degrees DEBURRING MULTIFLUTE CUTTER COUNTERSINK 'Severance Industries'USA | eBay

Kennametal 3.37141R332 45° Combo Chamfer and Countersink Drill 1245727 32mm Body | eBay

Severance 1 1/2"/45 Degrees Single Flute Countersink | eBay

Severance CK 2" 45 Degree, 6 Flute Countersink | eBay

HSS Countersink MA Ford 2"x45deg .500 Shank | eBay

Severance 1 1/4", 45 Degree Single Flute Countersink | eBay

When you're finished boring you can just chuck up the countersink, find the zero point, and raise the table 3/16". It might be hard to find the 3/16" mark on the Z dial, but you can always raise the table .187" which should be close enough

 

[schmidty13]

Is this aluminum? How thick? If its aluminum and thick enough, just use a 45degree chamfer bit with a flush bearing in a hand held woodworking router. I have even done this, even with a piece of steel with a variable speed mechanism to get the routers speed down so you don't burn out the cutter.
Just a thought anyways
Cheers
Martin

Thanks for the idea Martin. It is thick enough (1") but it is A36 HR.

 

[schmidty13]

If it's just one part, maybe file it by hand.

Thanks for the idea, Bruce, but it will be a "production" run. Not sure exactly how many, but likely somewhere around 10-30 at a time.

I appreciate the pippin file info, though. I will "file" that away for future use.

 

[schmidty13]

How about something like this? I bought a set of 3 and I believe the largest is about 3 inches in diameter.
Joe

There's the head-slap I needed. I didn't even think to look for XL sized countersinks. I just assumed they stopped at around an inch or so. I will look at these more. Thanks!

 

[schmidty13]

Just to add a photo of what was said above. The people who modify cylinder bore encounter this problem regularly. Below they operator has mounted what appears to be a 1" dia chamfering tool in the boring head and running the machine backwards. You can place the the below style of 45deg in the boring head, on the right side, then you have an adjustable chafering tool.

Thanks for the links as well as the operation tips! I will certainly look into this.

 

[schmidty13]

A big "thank you" to all of you. A bunch of good ideas here. My tooling/workholding wish list just got much larger!