Radiused edges on holes in sheet

||> >I think the plates were tumbled originally, ||>

||> By all means a vibratory tumbler de-burring setup ||> is the way to go with this. ||>

||> Jim || ||Pretty worthless where it comes to putting a nice radius desired on the ||holes.

I think "nice radius" exceeds the OP's spec. He just wants it to not cut the lacing. Sounds like vibratory tumbling is the way to go, assuming the media can be had in a small enough size to pass through the 1/8" holes. Texas Parts Guy

Reply to
Rex B
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My concern with the boring head in this case is that - and maybe I'm reading something into this that I shouldn't be - there doesn't seem to be any particular degree of precision in the location of the holes or the curvature of the parts. Using a single-point cutter in a boring head, rather than a piloted cutter that is allowed to "float" the piece into alignment, means that you will have to crank the table into alignment for each piece.

OK, I do see a way to to it. Make a curved base to fit the part. Two bases actually, one concave and one convex, unless you grind your cutter to cut both sides of the sheet at once. Bore a .125" hole in the base. Locate the hole under the boring head. Loose pin in hole, place part over pin, clamp in place, remove pin, bore. Still seems like an awful lot of work.

My whole point is that, given the thinness of the workpieces to begin with, it probably doesn't matter a whole hell of a lot whether he puts a nice radius on the holes or a cruder chamfer followed by some abrasive easing of the edges. A couple of quick twists from each side with a hook-type deburring tool will probably be as good as anything.

Let's take it to an extreme. Let's say his plates are not 18 gauge steel, but are made from good old Gillette double-edge Blue Blades. Some might debate about the benefits of a chamfer vs. a radius, but you and I both know that either one is going to chew through his laces in pretty short order, right?

I've broken a lot of boot laces in my time. But I've also worn through more than a few eyelets - aluminum, brass, and even some steel I think. He'll get those nice radiuses eventually. And, no matter what he does to the holes, he'll also wear through some laces.

John Martin

Reply to
JMartin957

As I understood the problem, the piece was bent in only one direction, so had flat faces, but each face at a slight angle to the other. By using a narrow support base, the angle had no bearing on holding the part. I don't recall reading about any curved surfaces, but at this point I'm not really sure what I read.

Assuming we got back to the original post, where the hole was 1/4", and the thickness was such that a radius of approximately .040" would have been desirable, a boring head used with a pair of toggle clamps and a removable pin would have yielded a beautiful radius, necessary or not, in very quick order. Certainly much faster, and more consistent, than anything done by hand. That was my point. When you have a large number of items to handle, the quick spin of the hand can become a slow way to arrive at your destination. To remove enough material to establish even remotely what he had asked would have required a few turns, not just one or two. All bets are off when the changes were suggested.

Given the hole is now 1/8" and the radius quite small, you may be right.

Chuckle! Yep.

I agree. I also agree that the closer he can come to a full radius, assuming he has enough plate thickness, the longer will the laces last. I get the idea he was hoping for that scenario. He'd get results consistent with his efforts. Again, I think he was cognizant of that fact. That's why he was asking about achieving the radius, and why I posted a tried and proven method of achieving his goal. I chuckled a great deal when the arm chair *machinist* suggested the use of Cratex to remove so much metal, especially from sharp edges. You'd spend more time changing rubber than you would establishing a questionable radius, and that boggles the mind. There's one hell of a difference between polishing something and removing metal to form it. If I didn't learn anything else in my years in the shop, I learned that.

Harold

Reply to
Harold & Susan Vordos

Hi, it's me, the OP. The plates were manufactured en masse by some third party who punched, bent and tumbled them. My friend/client is interested in getting the holes smoother than they came.

Yes, the pieces are bent/folded along the centerline, roughly 10 degrees. Unfortunately they were bent _after_ the punching and four of the eight holes are on that now-bent centerline. :\

Not changes, realizations. I hadn't seen the plates in a long time (years). I remembered them having more reasonable-size lacing holes.

So now I'm looking for a 'deburring' tool small enough to do the job. I'll probably have to make it. If I can make it a portable hand tool that's nearly foolproof (yeah right), maybe based on a 'Yankee screwdriver', I can actually hand the job off to the owner of the plates. He's only so good with his hands, but this he could do. And he is patient.

On the other hand, I'm having a vision of a tool to go in a drill(press):

| | | | | | | | |/\/\/\/\/\/\/\/\/\/\/\| | _ _ | | / \ / \| | \_/ \_/| | | |__________________| \ || / \ || / \ || / \ || / \_||_/ | | | | | | \ / || || || || || || || || || || || || || || || __________|| | || |eccentric|| | || | weight || | || |_________|| || \\ ... I chuckled a great deal when the

A lot of people seem to have read 'radiused' as 'deburred' and that led to quite a number of interesting and informative yet non-helpful suggestions.

Reply to
Carl West

Ouch! That pretty much rules out my idea.

You could probably make a radius tool of sorts that could be mounted in a small drill motor. Have you given some consideration to a tool somewhat like a countersink that has a cross hole that is used as a cutting edge? A small radius tool with a like cross hole might work. They tend to be self limiting (depth-wise), although not completely. I'm thinking it would work, even on the bend, so long as it's not too large at the head.. For sure, it would probably work in something like a Yankee screwdriver, but any reversing could be a death knell for the cutting edge. A one direction drive would be desirable. A small battery driven drill motor, or screw driver, would be super good.

I trust you'd be relying on centrifugal force to aid in cutting? My opinion is the shank won't hold up, and it would be somewhat clumsy to use, considering you'd have to stop the spindle each time you changed holes. It would also be very delicate, very easy to damage when bumped.

Chuckle. Yep, it is! I think I'd avoid a setup like that. One of the problems would be getting enough force without spinning the tool at outrageous speeds. You'd get into trouble in a hurry considering the large area of tool in contact with the work, especially on such a slender shank. .

This job just might get down to a hand operation.. If your man is patient, set him to work with one of those revolving hand deburr tools. He could do them while watching his favorite TV program and be done with the project in a couple evenings. I final touchup with Cratex, or a spinning bit of abrasive cloth would be a great idea. That would remove any whiskers that might be a bit aggressive.

A full radius that is smooth is likely to be as good as it gets.. I think it would be worth the effort, personally.

Sort of goes with the territory. I guess we all think we're clever and know how to best do things. There's no substitute for good experience, though.

I'd be interested in hearing how this all shakes out, even the things that don't work. Why don't you keep us posted on the progress of the project?

Harold

Reply to
Harold & Susan Vordos

You've said (or implied) several times that nothing seems to be feasible considering the number of parts. Soooo!

Scrap them. Have them remade to your specs which of course have the holes with proper radius and surface finish prior to the bending.

On the other hand, if doing by hand is what is required, then do them by hand.

Reply to
Lurker

How authentic do these need to be? How about leaving the holes as they are and using kevlar laces? I've never used kevlar cord, but I imagine it would hold up quite a while for this application, even with the slightly rough holes.

Reply to
Bert

The owner is trying very hard for completely period materials in his entire rig. Once he's had the experience, we may find him experimenting with more modern, lower-maintenance materials. Or not.

He'll be quite a sight with the silk-laced lamellar over a riveted mail hauberk over a linen gambeson stuffed with cotton fiber. And very well protected. Maybe a little less fleet-of-foot than he'd like...

Reply to
Carl West

Getting in late to this but why not run an abrasive brush through the hole? As I understand the use of the brushes, they have softer bristles that have an abrasive bonded to the ends. If, and this is only a thought, you bought some about

5/32-3/16 diameter and run them back and forth through the hole from >You've said (or implied) several times that nothing seems to be
Reply to
R. Wink

Kevlar is marvelously strong -- but there are several things it won't do well -- the primary one being bent over small radii. Also not too good on abrasion. It will wear out a lot faster than nylon in this application.

Boris

Reply to
Boris Beizer

What a lot of silly fuss over a non-problem. I just don't see ancient armorers measuring hole-edge radii with tiny radius gauges and optical comparators.

  1. I took a standard deburring tool (e.g., Vargas) and tried that. Without modification. In three passes on each side, holding the tool at a slightly different angle each time, I created a nice, soft, rounded edge on the inside of the hole. Then I modified the tool slightly using a diamond burr and created one with an appropriate radius. That took only two passes at about two seconds per hole.
  2. Took a small stone and shaped it with a diamond point tool to create an appropriate edge radius. A bit slower than the de-burring tool, but gave a nicer finish.
  3. Took a piece of small diameter (e.g. 3/16") tool steel rod machined a rounded slot in it. Heated the sucker up to red hot and then used a small file with a rounded edge of the right radius to impress the file's edge teeth into the tool. Reheated and quenched to harden. The result is a concave burr. Maybe you can buy them, but I didn't find any in my Jeweler's or dental supply catalogs. Works great on soft metals -- doesn't last too long on steel.
Reply to
Boris Beizer

As I understand the use of the brushes, they

is only a thought, you bought some about

the face directions, wouldn't the abrasive action

in large chunks of steel, brass and other

normal hones.

Hmmm. maybe #56076 or #56078 from

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a saber-saw.

This part of the description: > Designed for ultra-fine deburring and cleaning of holes produced by micro drilling, but will not alter the diameter or surface finish. makes me wonder whether it'll do the rounding I'm looking for.

Reply to
Carl West

I just posted an article on what I believe to be a suitable tool for your purpose. You would have to slightly rock it for the holes along the bend.

See

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the associated photos.

Ted

Reply to
Ted Edwards

I posted a description of a tool that might help you. See

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associated photos. You would rock the tool slightly to do the ones on the bend.

Ted

Reply to
Ted Edwards

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