Flycutter as hole saw?

Hello all,
I am getting closer to doing the job that involves clamping open boxes, DB 9 holes, etc. There will be some round holes, and my first thought
was a boring head. That would be overkill in precision capability, but I'd like to learn how to use one, so it seemed reasonable.
The acrylic and facing problems came along, and a flycutter is officially in transit (3/4 shanks). Can I (ab)use that as a hole saw? Is it safe? Should I clamp the waste to avoid catching on the bit?
I still plan to get a boring head, but would rather wait a while to let my wallet cool off a little. Another reason to wait on the boring head is that I am not convinced I will take to flycutter. If it gives me the creeps for facing, I might prefer a face mill to a boring head as my next purchase.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's very easy to make your own adjustable boring bars. A length of 3/4" or bigger steel bar, drill a 5/16" or 3/8" cross hole at one end and drill and tap for a grub screw to hold the cutting tool that goes in the cross hole. If you drill the cross hole at 45 degrees to the shank instead of 90 degrees to it then the non cutting end of the tool sticks up out of the way of the workpiece i.e. you can use longer tools with more diametrical adjustment on them. Cutting tools can be ground up from old milling cutters, drill bits or use carbide tipped tools on round shanks which are cheaply available from engineering suppliers.
Start your hole with the biggest drill bit or milling cutter to hand and then enlarge it as required with the boring bar.
I've made loads over the years in various sizes to bore from 3/4" up to 4" or more. Whatever size bar I use for the shank I generally turn a 3/4" end on it and run it in an R8 collet. -- Dave Baker
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I made my flycutters/boring bars the same as Dave except I drilled and reamed a 1/4 hole in the bottom end. Ream to a slip fit and use a dowel slipped into the hole to measure over to the edge of the tool bit. (Subtract half the dowel dia.) Drill a 1/4 inche hole in the center of the work piece, install the flycutter. Index the 1/4 dowel into the drilled hole and you stabilize the tool to the workpiece. Hole will be dead nuts. Remove the 1/4 inche dowel for flycutting, of course. Oh, one more thing, you can slip a small spring over the 1/4 dowel to hold the scrap down, if you wish.
Warren
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Depending on the construction of the fly cutter, you may not be able to install a tool such that it will serve as a hole saw. Fly cutters are generally intended for tools that somewhat parallel the face being machined. If you have one that permits the tool to be installed at a right angle, parallel to the spindle, it might serve your needs, but you may not have the option to select the diameter you desire. An operation such as that is called trepanning, where you remove a core piece without reducing it to chips. It can be accomplished easier with a boring head, but even that can be challenging---especially when machining tough materials like the majority of the 300 series stainless alloys or the chrome moly series.
Regards clamping the piece that comes loose---it's usually a good idea to use a slightly angled tool, so the cut will be quite thin at one edge, the outer one preferred, so you don't leave a lot in the hole. When it's about to break through, you stop cutting and remove it manually. By setting a quill stop, that's easy. Often, when you break through, the core piece will shift enough to bind and break the tool, so it's not a good way to get the piece out. If stop cutting at the right point, it's real easy to remove the core with a light tap of a hammer on one side. Needless to say, you should be on parallels, not working off the table face. Be mindful of the tapered edge remaining--it can be quite sharp if you stop at the right place.
Using a boring head for fly cutting isn't likely to work much better than using a fly cutter for trepanning. For one, it may not run smoothly if you are running at reasonable speed. The advantage of fly cutting is the ability to run fast, so your single point tool will permit a faster feed rate. As mentioned in a different thread, you're limited by the tool's ability to cut at the limits of the material, but some materials have literally no restrictions. Aluminum, for example. If speed isn't a concern, you might get away with the boring head, but I'd advise keeping the slide locked to avoid movement sideways, under cutting pressure. Surface finish would likely suffer otherwise.
If you don't have a boring head now, and you're debating between a face mill and the boring head, that should be a no-brainer. Buy the boring head. You can face mill with a fly cutter, which can be shop made with ease, or even end mills, A face mill won't bore holes, so running without the boring head would be the greater restriction.
Harold
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Harold,

I need to read this more and ask some more questions. However, my question is not so much about using a boring head for flycutting, as it is using either a flycutter or boring head to make large round holes in thin steel and some truly awful gunk passing as metal: when cut, it reduces to a mix of what seems like cast iron dust and razor sharp oat meal - terrible stuff.
A hole saw might be the right answer, but I have relatively few such holes to make, and have more faith in a carbide bit than the hole saws at Lowe's.
All of that said, I might see the problem with the flycutter for the job. I'll think it through some more and post again once I can explain it. Boring bars can be had cheaply, and given that I don't care about precision in diameter, I might do well to rig my own holder as suggested elsewhere. Also, I can afford an import boring set; I was simply hoping to put it off a while given the additional measuring tools I just bought. No worries about the flycutter; it was cheap and I will certainly get use out of it, so it was a great place to start for facing if nothing else.

I bought a $27 (for about half price it turns out!) flycutter set and some bits; they should arrive early next week. I reserve the right to be scared silly of it (always thinking of "Lefty" and the blurry area), in which case I might opt for the face mill. If the flycutter and I get along (seems likely), then I agree the boring head would be next.
Thanks!
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Harold,
Are there bits commonly available for trepanning in a boring head? If I wanted to make one, how would it be shaped? I'd start with round stock so that it could be mounted in the head, yes?
Regards,
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I was faced with this challenge years ago, when I built a gasketed filter press for my gold refining operation. I had to cut about two dozen washers from an unknown (austenitic) stainless material, roughly 3/16" thick. Finished washers were roughly 3" diameter, with a bore of 1-1/2" as I recall. The press is long gone now, having been sold along with the refining business I sold when I retired, so I may be off on the sizes. No matter, the principle remains unchanged.
I used a 3/8" HSS end mill shank, on which I ground what resembles a parting tool for a lathe, with a slight cant to the cutting edge, so it would leave a very thin section on one side of the part being removed (the washer), so there was little material to machine afterwards. You stop cutting before breaking through to avoid the tool binding on the part being removed from the stock, and the thin section makes it easy to get the piece out. The problems of cutting stainless in this fashion were difficult to overcome. I ended up buying a BoeLube setup, which solved all the machining problems. Sulfur oil alone wasn't adequate. That would likely not be true on other materials.
One runs the boring head very slowly, using the finest feed. With a chip breaker properly ground in the tool, it works great, but would certainly become a serious challenge if the cut was very deep. There's considerable chatter, due in part to the rather flimsy setup. You can often eliminate the chatter with proper speed and feed selection, however.
One of the things you have to address is considerable side clearance on the tool, where it must clear the radius of the cut on the outside edge of the circle. The tool looks somewhat odd, but works fine. Should you decide to try it, remember, the material you select for your tool will leave the tool edge ahead of center unless you reduce it at the point of the cut to the centerline of the tool. That the cutting edge is on center, or not, has a serious effect on how the tool sees the material, and the relief angles. Does this make sense to you? If not, lets talk. It's important that you understand it well.
Harold
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think what you're saying is that if the entire cutting edge is to be square to the cut, the tool itself may need to be curved, and the inside and outside cutting edges will be on the centerline, making the edge look "slanted" in relation to the rest of the tool (I suppose if the tool were short enough that it wouldn't need to be curved, then one would get more chatter...?). Unlike a bit where the cut is straight, although each relief may look different, when measured in reference to its own cutting edge it'll be the same as the other. Am I understanding this or have a disappeared over the horizon on a tangent?
I just finished a job where a setup like this would have made sense. I was drilling 2.250" holes in .250 6061 plate and then finishing them with a boring head. I did 12 of them. The hole saw was pretty sloppy, and although it wasn't all that important that the holes be of similar size, the diameter of the holes made by the hole saw varied quite a bit. The goal was to have holes with a decent finish and it would have satisfied my sense of propriety if the first holes were accurate and finished well enough so that passes with the boring bar were unnecessary. It's probable that I'll end up performing this operation again, so I'm interested in how to do it quickly and cleanly.
As always, thanks.
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

the
the
to
not,
important
and
relief
it'll
Sigh! Trust me to say something in such a way that I use up all the words I know, but fail to hit on the point at hand.
OK----lets try it this way:
Boring heads (at least the ones I have) are made such that the centerline of the cutting tool is the centerline of the head. For boring, that's exactly where you want the tool to fall, due to the position of your boring tool. For trepanning, that isn't the case. That means that when you make a tool such as I described, the actual cutting edge will be in front of center unless you grind away half of the shank you use to grind your tool. Does that make sense? You'd grind what is a D configuration, with the straight side of the D the cutting edge, which will parallel the slide of the boring head. This tool, when installed in the boring head, would have the cutting edge on the centerline of the head. You then grind away the sides to establish the width of the tool, grinding greater relief on what will form the outside of the circle you'll generate, so the tool clears the circular slot it generates, and much less on the opposite side, for the same reason. The tool should also have back clearance, so as it goes deeper into the cut, it doesn't drag on the portion behind the cutting edge. In simple terms, the point of contact, the cutting edge, will be the broadest portion of the tool, with clearance in all directions ground on the tool. Hope that makes it somewhat more clear. It's easy to do, just hard for me to describe. One more thing to remember. Make the tool cut in a clockwise direction, so you don't unscrew the boring head from its shank. The tool you'll grind will be handed because one side has considerably more relief than the other.

was
the
was
that
up
I fully understand about the hole saw. They're a dreadful tool, although they are good for opening a large hole. Like you, I've experienced various sizes from the same saw, and am never pleased with the quality of the hole.
A note to remember. When you open a hole by the means I've described, it may not come out really pretty. You'll have some trouble with chip flow if your tool isn't perfect, and the cut well lubricated, so the size could vary to some degree ( a few thou) from hole to hole, depending on if you have chip problems, or not. Finish would be a reflection of chip flow and lubrication. Bottom line-----if you want all the holes to have sharp, square corners, with a nice finish, treat the trepanning operation in keeping with what it really is-----a roughing operation. Shoot for a hole that is somewhat undersized----maybe .020/.040", depending on how well it goes. That will allow for a finish pass with a boring head after the fact, providing a uniform hole and finish. That's called good workmanship, and should be practiced unless the hole just plain doesn't matter.

You're welcome, Peter. Hope some of this helps. All of it has been used with success, so if you have any particular problems, let me know. Could be I've been through the same thing and may recall how I got around it.
Harold
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes. I understand your point now. That makes sense, as does the rest of your post.
Regards,
Peter.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I had another thought/realization. One ouwld be able to use a higher spindle speed with a boring/trepanning setup than with a hole saw (chatter being a gating factor obviously), yes? This would be an advantage to those of us with a minimum spindle speed of 330RPM... A VFD is looking pretty good at the moment.
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote in message

used
those
By nature of the design of the trepanning tool for this type of application, the tool tends to be rather flimsy, which is part of the problem, so you are likely to be well restricted by chatter. If not, so much the better. In aluminum you should be able to achieve a good speed, so long as you can keep the cut well lubed. That, or machine 2024, which is quite forgiving of dry machining. Remember, my project was one of the worst case scenarios, a tough grade of stainless, so I was very limited as to RPM. You may have good fortune and not be so restricted.
Love to hear how it turns out when you give it a go. Can we count on a report?
Harold
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Certainly, although it may be a while.
Peter
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bill Schwab wrote:

Non-standard sized large round holes? Thin metal (steel or aluminum?) boxes? Using a drillpress or a mill or something else?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm a big fan of punching sheet metal as opposed to drilling it. - GWE
Dave wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Greenlee punches can get expensive but they make clean holes. For round holes the other option might be one of those multi-step hole cutters. I don't like the flycutter/boring head idea.
Grant Erwin wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dave,

Sorry - large holes, not necessarily non-standard, thin metal, one steel, one a mix of various metalic substances. If I really get lucky, I might be able to negotiate the steel out of existence, leaving just the dusty/grity/disgusting metal that must be penetrated. That stuff would probably yield to the cheapest of hole saws, assuming I can get one of a suitable size (likely).
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
    [ ... ]

    One thing to consider is that hole saws tend to make rather ugly holes in metal -- at least based on use in a drill press.
    What I always like for aluminum or steel panels is a Greenlee Chassis punch -- but that can be *very* expensive.
    And if you're working with the die-cast aluminum zinc boxes, I think that the stresses of a chassis punch might lead to cracking.
    What I've found to do a nice job of making clean holes in sheet metal on a drill press is something called a "Roto-Bor". I have two sets, covering a size range from about 1/4" to 1". They have a spring-loaded pilot which fits into a center punch mark or a center drill hole to precisely locate the cutter.
    The cutter has two flutes for the smaller sizes, or four for the larger sizes.
    The major disadvantage of this is that as far as I can determine, these are no longer made.
    Note that using a boring head on the mill will not eliminate the need for a hole to start with -- and the bigger the hole the better, because a boring head is rather a rather slow way of removing material. So, a hole saw to produce an undersized hole is a good thing to use *with* the boring head.
    Enjoy,         DoN.
--
Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snip----

You missed the part about trepanning, DoN. I've done it with outstanding success. You can, indeed, create large holes without having a starter hole. That was the point of our discussion above.
Harold
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

    Yes -- but that needs greater skill in grinding the tool to go into the boring head. Sometimes, it may be easier to use the hole saw followed by the boring head with standard boring bars. After all, the original poster does not yet have tool grinding skills. (Nor do I remember whether he has even indicated that he has a bench grinder.)
    Enjoy,         DoN.
--
Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.