Flycutter as hole saw?

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

Reply to
Peter Grey
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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

Reply to
Harold and Susan Vordos

According to Harold and Susan Vordos :

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.

Reply to
DoN. Nichols

Certainly, although it may be a while.

Peter

Reply to
Peter Grey

Yep, detailed instructions for which I provided, although they were directed towards a different individual, one that hopes to use the process in the near future. It has been a learning thing, of sorts, for those that haven't been there. I was fortunate (?) to have visited the problem some time ago and solved many of the issues.

Sometimes, it may be easier to use the hole saw

Agreed. My conversation with Peter evolved well after the fact, and my comments weren't necessarily directed towards Bill. Not that he might not benefit, mind you. The trepanning method I discussed is a wonderful backup for that special job that comes along and there's no reasonable method otherwise. Good example might be the blanking of many round pieces from plate or sheet, where a center hole may not be permitted, ruling out, or seriously limiting a hole saw.

Grinding a tool for trepanning with a boring head does require some skill, of that there's no question, but if I can master the technique, I can't help but think that others can as well. What's important is to understand how it cuts, and what clearances and rake are necessary. The rest is just applying the concept to the tool. If a person can grind their own lathe tools, there's very little difference in grinding a trepanning tool.

Harold

Reply to
Harold and Susan Vordos

According to Harold and Susan Vordos :

[ ... ]

And it was nice of you to share that information.

[ ... ]

Agreed. Though the Roto-Bor which I mentioned (if available) could have the spring loaded pilot point on a small disk of sacrifical metal placed over the workpiece. (But the shape of the cutting flutes on it result in a sharp-edged disk, so they are better for holes than making disks.

The primary thing is that you need a different trepanning cutter for each size of hole, while a lathe tool will work through a wide range of sizes. (I don't think that I saw this explicitly mentioned in the discussion.) This means that I would probably not do the trepanning unless it was a serious improvement over the alternatives possible with my existing tooling.

Enjoy, DoN.

Reply to
DoN. Nichols

That's true, within reason. As the hole size increases, it's more forgiving, but it can still be a problem. I covered it in principle in the description without making mention that the tool would be different from size to size.

This means that I would probably not do the trepanning

No doubt, when one has other means, they are likely to be better. The point here is for someone that has no other means, but has a mill drill or a knee mill, this opens door to an operation that otherwise may not be possible. It's the main reason I did it in the first place. My objective was to blank the needed "washers" for the filter press I was building. At that point in my career, I had been away from the shop for considerable time and had no interest in purchasing tools that would get used to manufacture a specific item and perhaps never used again. By using my boring head and some creativity, I managed to accomplish my task without buying unwanted tools and or tooling. Overall, it was far and away faster and easier than sawing the pieces, which would have been my next option. Another way to look at the situation is it's Saturday afternoon and you can't buy your needs. It's nice to have an alternate method for accomplishing what can be a rotten task.

Harold

Reply to
Harold and Susan Vordos

Harold, Don, everybody,

That captures the spirit(s) in which I asked the question. That, and a simple minded curiosity as to whether the flycutter that is on the way would do this job too. It's a long and sad story, but I should have a bench grinder already, and it _might_ actually still be in good shape. Failing that, I need to get one. The bigger concern is tricky tool grinding; better to start on that adventure with simple stuff.

The replies taken together seem to favor a hole saw, possibly followed by clean up with a boring head or flycutter. Suppose that I get a slightly undersized hole saw or edge drill and take out the waste with a buzz saw. Could I then reasonably/safely use the flycutter to drop through the thickness to clean up the diameter? In the edge-drilled case, there will be significant changes in the amount of metal being removed; is that a problem? Below, there is a marginal ascii drawing of what I have in mind. I think I ordered tool bits that will do it provided enough waste has been removed.

I don't know why I expect troubles with a hole saw, I just do :) It will probably work fine. If this were simply a matter of some extra wear on a $6 carbide bit, I'd use the flycutter; since there's more to it, the price of a hole saw seems justified. At least a cheap one, if it will work on the steel, will pay for itself in a hurry if I don't have to edge drill the hole.

Fair? Any recommendations on a hole saw?

Bill

/.........../ /.........../ /.........../ ~......... /

-------+~......... / ///////|~~~~~~~~-- ///////+-----+------------... /////////////|

-------------+------------...

..... Bit ~~~~~ cutting edge of bit //// section through work

Reply to
Bill Schwab

According to Bill Schwab :

[ ... ]

A flycutter as supplied would not, but with some custom bit grinding, it might work for a reasonably small workpiece thickness.

Well ... to try to trepan with a fly cutter, you *will* need to do some tricky tool grinding.

I consider the boring head to be the better cleanup option.

With the hole saw, and not too far under the desired size, yes. As you point out, the edge drilled case would be somewhat different.

Yes -- you will be performing an interrupted cut, which is more stress on either the boring head or the flycutter --- and more so on the flycutter I believe.

It will tend to produce a rather rough ID on the hole it produces, based on my experience.

And a good thing to do to help a hole saw cut better (and not clog up) is to drill one or more holes just inside the cut line, which will let chips fall clear of the teeth more easily.

Leonix? Starrett?

[ ... ]

Do you intend to go all the way through, or to leave a shoulder as shown there?

With the drilled holes to clear out the slug, the width of material to be removed will be greater than with the hole saw -- at least at some positions.

The angle of the bit will normally be more shallow than what you have shown -- though that is probably more the limitations of ASCII graphics than your mental image of the position of the bit. But essentially, as you go deeper, the ground cutting edge on the bottom end of the bit will not be the only thing which is contacting the workpiece. You will add the sloped under-surface of the body of the bit, which is not ground to cut, nor to have relief. This increases the amount of cut, especially when you get to the projections between the holes which you drilled to knock out the waste stock.

The knocking of that under surface can sometimes cause the bit to tilt in the holder, and *that* will move the tip outward so it will cut a larger circle than you were trying to cut. Since you will already be down into the circle, this will probably jam the bit into the workpiece, and attempt to pull it out of whatever is holding it in place.

The bit on the boring head comes down vertically, and can be ground to be fairly narrow if needed. Also, you can start with a reduced diameter to make the first pass, so there is less stock under the heel of the bit.

Granted -- you can grind a bit to follow a shape which will approximate a trepaning bit for a boring head -- for fairly thin workpieces.

Try something like this (again understanding the limits of ASCII graphics in portraying the angle of the bit):

/ / / / / / / _ / / | /________|

Reply to
DoN. Nichols

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

Reply to
hobo

Don,

Thin work I have going for me.

Probably best left for later. That's ok.

Unless I encounter other priorities, I will probably have one before my "production run" of this design. For now, I need to clean up a few holes, and really not all that accurately.

Thanks.

Through.

My mental image is pretty limited, but yes, I realize the angle shown is too steep.

Could that not be avoided by taking multiple passes to enlarge the hole? I _think_ I understand what you mean, and I first started to realize it from Harold's initial reply.

Agreed, that's a problem.

I think I follow. Suddenly it doesn't seem so bad, but the hole saw is probably the way to go.

Thanks!!

Bill

Reply to
Bill Schwab

According to Bill Schwab :

[ ... ]

That helps.

[ ... ]

O.K. Clean up *can* be done with a half-round file for just a few holes.

Hopefully, others will toss in more suggestions.

O.K.

[ ... ]

Good enough. Just making sure. :-)

Yes -- with the problem that it is difficult to set a fly cutter precisely to a given size, and with multiple holes and multiple passes, you will have to do the same thing multiple times -- unless you fixture the workpiece, do one pass for all workpieces, then increase and the next pass for all, etc.

The boring head has a micrometer dial to give you repeatable readings -- though it is still easy enough to get one turn off and be too small (no real problem) or too big (I have yet to see a mill with an "add metal back" feature. :-)

Good.

[ ... ]

You're welcome.

Enjoy, DoN.

Reply to
DoN. Nichols

I have a flycutter made to make large holes using a drill press, General was the brand, cost something like $7 or so when I got it. IIRC, it'll do holes up to 4" or so in thin material. I've used it in plexiglas and aluminum, it should be run SLOW. Got it at the local hardware store, it was sold as a flycutter for making holes, not as a milling attachment. It's got a pilot bit that I rplaced with a piece of drill rod, I make the hole for it first, clamp things down and have at it. Works well enough. It's about as precise as you could set the radius.

Stan

Reply to
stans4

I used an identical cutter to open holes for 3" TA's and hubs in electrical cans when I installed my 3 phase service, and drove it with a 1/2" Milwaukee hand drill. With patience, it works great. It doesn't hurt if you can grind good parting tools.

Harold

Reply to
Harold and Susan Vordos

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