short / very short end mill(s) or drill bit(s)

I've turned some bearings from 841 bronze from McMaster-Carr for a non-precision application. The largest part of the outside diameter is 3/4", 9/16" long overall and turned into the shape of a flanged bearing, which are in turn, then pressed into its mount. The bearings have a 7/16" diameter through hole, which I've been drilling with a drill bit held in a Jacobs chuck in a lathe tailstock. The tip of the drill bit is more than 4" past the fingers of the chuck and even further from the point at which the chuck's shaft is supported by the lathe's tailstock. So there's lots of opportunity to lever the drill bit. The chucked work piece is pulling the bit off of the axis of rotation, despite having used a center cutter to establish the center, and a pilot hole, which hole suffers from the same problem. I don't have a lathe boring bar that small, and don't have what I need to hold the work piece on the mill.

I need to make 6 more bearings and I'd like to be able to make them quickly, easily, and accurately without the off axis Macarena of the cutter.

If anyone has purchased an index of very short drill bits in 1/64" increments or knows where to source very short bits or end mills, please let me know. Or do I just plan on cutting an end mill? (which is probably going to be a PITA.)

Thanks in advance

I have cut quite a few holes with end mills and that can help. With a long drill sticking out of the tailstock, you can get some drift even with a good hole made with a center drill. When I start to get a little wiggle in the bit I take the holder off the QCTP and very lightly touch the drill to stop the wiggle. Then I back off and it's good to go from there. When I first started out in the dark ages I would flip the Armstrong holder around and use the butt of it to steady the bit to get it started properly. Of course you can't beat stubby for proper drilling but a stubby bit often requires a change for depth.

crossthread said:

I have cut quite a few holes with end mills and that can help. With a long drill sticking out of the tailstock, you can get some drift even with a good hole made with a center drill. When I start to get a little wiggle in the bit I take the holder off the QCTP and very lightly touch the drill to stop the wiggle. Then I back off and it's good to go from there. When I first started out in the dark ages I would flip the Armstrong holder around and use the butt of it to steady the bit to get it started properly. Of course you can't beat stubby for proper drilling but a stubby bit often requires a change for depth.

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maybe this needs more explanation. can be done with the center drill also. put the cuttting edges horizontal. then push the drill off center. it will cut with one edge only. tapered hole will be centered. best to predrill a bit larger for center drill.

Look for a set of “stub” or “screw machine” drills. They’re shorter than jobber drills, made for the close quarters of screw machine tool holders.

Yeah, buy "screw machine" length drills, not "jobber" length drills. And if you really must, start the hole with a stout center drill.

I'd tell you to just cut the excess length off the tail ends of your regular drills, but that wouldn't stiffen up the flutes. Screw machine drills have shorter flutes, and center drills have effectively the shortest possible flutes.

Since you are rotating the part to drill a hole it will naturally seek to center the tool. It sounds to me that your tailstock is not centered to your spindle.

Tail stock alignment check for sure. When I need something like that I just cut the drill and resharpen it.With a pilot hole the web thickness won't matter or just thin the web. I'm sure that Symmco has that size in stock.Heck I probably do.

I got so tired of making bushings that I bought a whole assortment,straight & flanged and It has been quite a time saver. I bought the longest in various sizes to cut down on the pn's and just trim to fit.

ratbldr427 said:

I got so tired of making bushings that I bought a whole assortment,straight & flanged and It has been quite a time saver. I bought the longest in various sizes to cut down on the pn's and just trim to fit.

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^^^ THIS ^^^ boxes of them.

Everybody and his bruder, Zoro, Grainger, MMC other "usual suspects" stock the "top hat" flanged as well as straight in Old Skewl or "soft" Oilite.

Some also stock the Iron-Bronze Oilite 2 / Oilite 16. Or Oilite-Plus (with teflon) as well as various plastics. All PROVEN STUFF!

See the maker's site for the types of material:

Oilite(R) -Superior Synthetic Performance Difference(R) Sleeve & Flange Bearings, Lubricants, Flexible Couplings - Beemer Precision, Inc.

Life is too DAMNED short to DIY nuisance components sold as commodity goods.

If No Joy as to fit?

I prefer altering the host, not the bearing.

Ever-after it DOES take a stock bearing - no further machining of either required.

Page Two;

Nought to do with bearings, "general case", rather.

You REALLY DO need to ... learn to start a drill properly.

Seriously. One of those "universal need" items in machining .. or even the least of hobby-now-and-then working, regardless of material, or whether lathe, DP, or hand-held.

It just ain't that hard ... once you grok that a DRILL "generates" a hole off the guidance of its own tip! "pointing at" ... where you want a hole is optimistic.

First-contact with the material to be drilled? Tip has to be "there". On-Axis. Not some other dam' place.

PLACE the tip .. in the right location, IN a divot from a centre punch (at least) ELSE use the stiff-as-a-wedding-night hard-on center-drill. Get it right, it JF works. "Experiment" until you have several ways that work for YOU!
Until you can "JFDI" one way or another without even thinking about it.

Technique. Skill. Less NEED of buying any more tooling than a(ny) decent quality ignorant drill, long or short. WTH? I can "start" a bleedin' "bellhanger" drill and have it track true. "Gun" drills are what they say they are. Really deep holes and right where they are meant to be.

Stiffness is a poor substitute for "correct", if only because "correct" is free and always in-stock, whilst specialty mills and boring-bars are never free and often days away if not also on back-order.

"Get it right!"

It will pay back EASILY a hundred times over, going-forward

.. vs half a lifetime wasted f*****g-with off-axis holes and whining you need a plunge end-mill or a balanced boring-bar.

Not to mention the divorce costs of off-axis holes when they are NOT on a machine-tool...

Thanks for the input

How interesting the different perspectives, some focused on the economy of their time, David Scott focused on the physics of the cut, some focused on the equipment, and others on technique. Learn, learn, learn, all from a simple bearing.

The tailstock alignment was not the issue and the poor alignment is probably operator error not chucking up the piece carefully enough. The piece was easily saved by using a lathe tool bit as a "boring bar" (similar to dian's suggestion) which happened to be small enough for the hole.

I didn't use pre-made bearings because I had three items I wanted to use 841 on, each of which with their own peculiarities, and I figured I'd just get a slug of material. Since the hosts' (thanks to Thermite for the vocabulary refinement) holes are no longer concentric, turning a bearing to a tolerance where it could then be pressed in turned out to be a good approach. Each bearing was turned to the point where it was close to the host's hole and then pressed in and the small flange kept provided help seating it. If it turns out there will be more bearings in my future, I may resort to keeping an assortment on hand.

Thermite's, dian's, crossthread's, others focus on technique is appreciated. Now having completed one of the "841" tasks, I see that regardless of how I get the hole size close, the final bore size should have been made with a reamer.

I think its probably worth it to get a set of machine screw length drill bits. I have wire size bits from Chicago Latrobe that beat the pants off anything I have ever gotten from Fastenal or anywhere else. If some has had a good experience with a particular brand, I'd like to know.

Do not expect to produce bearing quality holes with ANY length of drill bit. Build a boring operation into your process and you will not regret it.

1dogandnoexes said:

The piece was easily saved by using a lathe tool bit as a "boring bar" (similar to dian's suggestion) which happened to be small enough for the hole.

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"Along similar lines..." I keep a hand-graver handy to crown stuff... deburr.. hasty chamfer.. and generate starting divots for .....drilling..

I see that regardless of how I get the hole size close, the final bore size should have been made with a reamer.

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"D" reamer finish has always worked really well. Because.. I didn't really have to make all that many sizes. They were made to exactly the size I needed. And it was cheaper than investing in a store-bought set that was the wrong size nearly all the time!

Mind, "D" drill doesn't usually need a reamer, so... more than one way to get rich by stealing from yourself..

I think its probably worth it to get a set of machine screw length drill bits. I have wire size bits from Chicago Latrobe that beat the pants off anything I have ever gotten from Fastenal or anywhere else. If some has had a good experience with a particular brand, I'd like to know.

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C-L, Cle-Forge, CTD, etc.. and "parabolic grind" whenever I can.
And all at their best if bought a long time ago. "Sets" I hide away as last-ditch save-the-day, so several of mine really ARE old.

"Daily Driver" drills I buy 3 to a dozen at a go for the specific tasking - a small subset of "set" sizes are ever actually used for most work.

In the fullness of time, yah acquire the Huot storage "drawer" cabinets as well as the flip-up cases, and then you've "built" sets of what you use the most, US & metric.

Wire sizes:

1-60 & 61-80 here are CTD. Dunno if they are still as good or not.

Dalian Top Eastern out of China owns most of the old-line tap & drill companies for Donkey's Years already. some are still made in Chinese-owned US located factories. Others not.

And we don't necessarily get to know nor choose "which", so....

I hear, "right here, on PM" that Ford makes better drills these days that some others? I need some 61 to 80's anyway... time I did some fill-in and a new set or sets.

Thanks for the reminder..

I usually drill smaller and ream to size. For close quarters I use these type of reamers.

frankly i dont get the idea behind the short drills. if the tail or chuck is off they will not be on center either. a center drill has a better chance. spot drills i cut off. if you manage to get a starting hole centered, the short, stiff drill will rather hinder than help. its not stiff enough to act as a boring bar but stiff enough to mess up the hole. think of a reamer that is long and you chuck it up short to give it flexibility.

and the "self centering action" because the work rotates is whishfull thinking more often than not.

dian said:

frankly i dont get the idea behind the short drills. if the tail or chuck is off they will not be on center either. a center drill has a better chance. spot drills i cut off. if you manage to get a starting hole centered, the short, stiff drill will rather hinder than help. its not stiff enough to act as a boring bar but stiff enough to mess up the hole. think of a reamer that is long and you chuck it up short to give it flexibility.

and the "self centering action" because the work rotates is whishfull thinking more often than not.

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Consider the fact that when entering a drill is cutting on one side before the other sees any metal. What is happening right then, that tiny time before tip two sees any work?
Shorter or stiffer reduces the start "wandering". Once this action happens it is hard to stop and tends to build to a certain point.
Unlike a reamer or gun drill the margin can not guide.
A whole lot of this centering is tip grind and entry deflection so the make/grind matters when new along with what part of the drill hits.
Sometimes it is better not to have a pilot hole. Sometimes a "studder start" with a few tiny pokes in/out helps.

Once on the way drills go as they please. I think all have seen deep drill holes walk in unexplained directions, every single part different and think it all madness. It is not.

If depth and flute allows my go to is always, always stub drills. For the vast majority of work I do not know why so many use full length standard.
I guess this is a matter of have it in my toolbox.
Reamers I like long and bending as sizing tools.
Bob

Excellent / vocabulary lesson

tommy1010 said:

I usually drill smaller and ream to size. For close quarters I use these type of reamers.


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I like that solution and thanks for posting the pic. What's the name of that style reamer? New stub or machine screw reamers seem to be for use on CNC, which means they're probably designed to be used at speeds much higher than on a lathe. Have you used your reamers on a lathe? What brand are they?

Thanks in advance.

If I get a set of stub drills, do you have a brand to recommend? I'd like to get the set it in 1/64 increments and then use reamers for the final sizing. I saw one reference here at PM to an American made stub drill bit set, but I haven't been able to find it again.

From McMaster web site:

9/16" Jobber bit = 6 5/8" length

9/16" Short (screw machine) bit = 4" length

That gets you 2 5/8" closer.

But I like the idea of reaming. Perhaps drill 35/64" and finish with a 9/16" reamer. But get a full length reamer so it can follow the hole.

tommy1010 said:

I usually drill smaller and ream to size. For close quarters I use these type of reamers.


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