Technical Machinists, what is the technical name for this?

Because the cutting edge is on the other side of clockwise rotation, as in a valve seat cutter, right?

 

I actually may have spoken too soon, did not look that close, the ones we used had a different style of drive arbor with a much more positive retention like the one below.


"Manual reverse counterboring tools are one of the oldest back counterboring systems around. This system requires that you feed an arbor through your workpiece, stop your machine spindle and then manually connect a HSS or brazed carbide back counterboring head on the backside of your part. The obvious downsides to this type of system is that it is inherently slower than an automatic system and there will always be more risk involved when a machine operator is reaching inside a machine and physically locking on the cutting head. The upsides to these type of tools is that they are generally a more price conscience option compared to the automatic tools and they are stocked in U.S. in 1mm increments from Ø10mm (.394″) to Ø76mm (2.992″) in HSS. Brazed carbide cutters are available in Germany and typically require no more than a week delivery. Because these tools are 4-flute and piloted you can also reach long length to diameter ratios."

https://www.steinertechnologies.com/blog/which-reverse-counterboring-system-to-use/

 

Both of these are listed as shell end mills on the internet (yeah I know, therefore it must be right...). Go to TraversTool.com and use the search function. You'll find things just like this.

So I stand on the statement that generically they are called shell mills, and if you peruse that website where they are listed, you will see many different types. Oh well, heap on the abuse

 

Do both of those have a shoulder in the hole?

 

Can't tell. And Travers website is not fun to navigate on with an 8 year old never updated tablet. I know others that sell tooling have them also. You may want to peruse TraversTool.com or your tooling supplier of choice to see what is available. I go to Travers first as I have been buying from them since the early 70's and have never had a problem with their services. But I also get their paper catalog every other year, because I'm more comfortable looking for stuff that way.

Call me a troglodytic luddite or ludditic troglodyte! I can take it!

 

No name calling from me, just open honest discussion. What you are calling a "shell" mill is actually a "shell" mill. While my memory isn't that great on lots of little technical differences.......added to the fact that many times people (real card carrying machinists) also used a lot of the terminology somewhat loosely...........a shell mill is/or can be used as a spotface. The backs of the cutting tools can come in different shapes so that they fit different kinds of holders.

A holder for a milling machine is generally stronger than a holder for a drill press. The reason for that is that a milling machine will make a lengthwise cut.......like surfacing a head. There can be a lot of pressure exerted on the cutter and the adapter and the machines spindle when making a "sideways" cut as opposed to a "plunge" cut like a drill press does.

A milling machine also has the capability to make an actual plunge cut just like a drill press. A drill press is not built to handle the sideways pressure. Some people adapt drill presses by adding a moveable table to them, but they have to make very shallow and slow cuts because the spindle in the drill press isn't built to handle that pressure.

So back to the shell mill thing. Generally "spotface cutters" are smaller in diameter and may have a different type of holder or adapter that they mount to. As you saw above there are several variations in how they are made. By no means do I know of any exact definition that says "spotfaces" are limited to a certain diameter..........but I guess the defining factor would be that they usually (maybe always) have some type of pilot in the center of them that sticks in a hole and keeps them cutting concentric to that hole.

A "shell mill" can be somewhat small, but generally are larger than spotfacers. They also have no pilot in the center. If memory serves me, I believe there is a bolt which goes thru the center that retains them to the tool holder adapting it to a milling machine. Someone could make an adapter to hold a shell mill so it would fit a drill press, but the drill press probably would not have enough power to cut anything..

What I am trying to say is this...... A spotfacer is made to plunge downward and make a round cut with a flat bottom in a specific spot surrounding an existing hole. It is NOT designed to cut sideways on a flat surface such as machining a head flat.

A "shell mill" looks similar to a countersink but has no pilot in its center. It "usually" comes in sizes larger than a countersink and fits on a different type of adapter (for a milling machine). It is designed to cut sideways as you would do when milling a head.

The caveat here is that in a pinch someone could also use a shell mill to create a spotface if they didn't have a spotfacer that size, and the area under the center of the shell mill was a big enough hole to reach the inside diameter of the shell mills cutting flutes. Clearance in other words.

Good point, but the problem with making a spotface with an endmill is that an endmill usually can't cut well right at the center when making a plunge cut. There needs to be some type of hole or relief in the center area. If someone needs a spotface but does not want a hole thru the part, they can drill to the depth they want to spotface, and then come back with the end mill and cut to the same depth they drilled to.

 

Here is what a shell mill adapter looks like. Basically the hole in the center of the shell mill is the same diameter as the shiny part below the washer.......but the outer diameter of the shell mill can be different sizes. Allows interchangeability and fewer/cheaper tooling.

Correction: Bobss396 pointed out that I incorrectly identified the mounting shaft on the tool above as a "Jacobs". It should have been labeled an "R8". They are two completely different shapes by different manufacturers. When buying tooling for industrial milling machines, these are the normal two choices, and I had a brain fart and switched them in my mind. Thanks for pointing that out Bob, as I strive to post correct information and truly appreciate the opportunity to correct it.........

Oldtimers disease is a pita.

 

Roothawg, if you will send me a picture of the part you are trying to machine, I can probably tell you a way to do it, but right now I don't know if its a big or small part, and just how much supporting metal surrounds the spotface. Depending on what the part is, there may be other ways to accomplish what you need. I assume that since its a spotface, it isn't a "precision" diameter outside of trying to stay about the same diameter. If I'm wrong, tell me that too, if you would like my help.

 

Thanks for the offer. I have put this back on the Engineering group. They weren’t offering up any solutions, so I needed to educate myself. I think I have done that via this thread. Thanks to all that has contributed.

 

Not sure how often if ever you make it to Wichita, but stop in at The Yard Store on E Central, they have all kinds of used tooling, and new as well, most of it surplus from the aerospace shops in town. Prices are typically by the pound (cheap). I think I recall seeing these there on one of the shelves, idk if you could call them to have them look for one, I know they ship.

 

They are online, too!

I buy stuff from them frequently.

The used stuff has been checked well.

 

That is actually an R8 taper, used on milling machines. Shell mills are tough on small machine spindles, I see most of them used on CNC mills using a #30 and #40 morse tapers and larger. I also used them on large manual vertical and horizontal mills. Real workhorses like Van Normans amd Cincinnatis.

 

I used to go up quite frequently when I was working the floor. I used to take orders for buddies…

They are talking about sending me to Wichita next week. It’s still up in the air. It would be a good field trip.

 

Root, I hear you about know the correct name for something you are unfamiliar with, It seems us rubes have names for piece like you have posted, doo dads, thingamajigs & doohickeys. HRP

 

Might check Goodson.com they sell a lot of engine machining specific tooling. If it matches a common size (sbc valve seats etc) they probably have it.
I'm not a machinist, can't help other than a source recommendation.

 

The official term is "hootis".

 

Good Catch Bob, and you are correct. My oldtimers caused me to "brain fart". Thanks for pointing that out. I will insert a correction in my original post.


The Jacobs taper is commonly used on drill bits of larger sizes for lathes and large drill presses. The machine will have a large taper and then tapered sleeves are used to get the correct size. You slip a tapered sleeve on the taper on the drill bit until its the correct size for the tapered hole in the machine. The flat end prevents the drill from turning as the tapers seat into the machine.
Adapters

 

I was just using my 3" 5-insert shell mill on the manual mill last night.

It does work pretty well at S: 340 F: 0.7

That makes a perfect gasket sealing surface, but it takes a while.

I have a 5" shell that can hold 14-inserts.

That one I run, fed slowly, with just two mounted in it, for larger surfaces, for a very shallow cut.

The Haas has some big ones, and doesn't mind ripping them through anything.

 

And bonus points are given to the purpose of the slot at the top....

 

On the adapter? So you can get the other tapered tool out. Heck, even my old Post Tool import press came with the tapered piece to remove the chuck

Oh, tip when sticking another inside, keep the flat sideways to the slot, not inline with it. So much easier to remove what was in there.

 

Not really sure what you mean by that. The flat at the end of the taper should be in alignment with the slot before sliding them together. Thats the only way it works. Then when someone wants to separate them later on, a taperered "punch" called a "drift" is inserted into the slot and smacked with a hammer to cause them to separate. Really basic and simple.
Smaller drill presses have a "drill chuck" that accepts straight shank drill bits.........but the chuck itself is mounted to the machine spindle via a jacobs taper. It usually is not removed and often does not have a slot to facilitate removal.

On a lathe, the tailstock will have a jacobs taper and its common to insert either a drill chuck or just a drill bit into the tailstock. There will be a slot to allow quick removal when done, but generally the machinist just cranks the movable tailstock till it bottoms against the tang on the end of the drill or chuck.....and it pops free. Can't do that on a drill press.

The point here is that when drilling smaller holes (5/8 and smaller) a drill chuck will first be inserted into the tailstock. The drill chuck will have a jacobs taper that is inserted into the tailstock, and usually at least one of the adapters will be needed to get it to the proper size to fit the tailstock.

If drilling holes larger than than appx 5/8, a chuck will have a hard time gripping the drill bit tight enough to resist turning in the chuck. While bits smaller than 5/8 are available with a tapered shank, for purposes of explanation just consider that larger drill bits require a stronger method to hold them .....so the jacobs taper is used and they are mounted directly into the tailstock by using the adapter sleeves.

Anyway the "drift" punch is simply a tapered flat sided punch that is driven like a wedge into the slot causing the tapered surfaces to separate.

One additional thing is that some machines use a "morse taper" which is simply a different angle than a jacobs.......but for most things we deal with you will probably use the Jacobs or the R8 type holder mentioned earlier.



Removing a Jacobs taper from a lathe tailstock
oogle.com/search?q=inserting+a+drill+in+a+tailstock+video&rlz=1C1GGRV_enUS751US751&oq=inserting+a+drill+in+a+tailstock+video&aqs=chrome..69i57j33i160.15310j0j15&sourceid=chrome&ie=UTF-8#kpvalbx=_t5LyYpHyNZqg5NoP6Yye2AQ10

 

Not related but......
The Silver and Deming drill bit was the best invention since the introduction of the drill chuck.

 

Here’s an Albrecht 1/2” keyless chuck with a #2 Morse and a #6 Jacobs taper nose inserted.



Correct me if I’m wrong but the nose of this adapter has a Jacobs taper while the long end is Morse taper that will fit spindles or tailstocks.


The Morse taper is easily removed with a drift punch, but the Jacobs taper, when clean and nick free at installation will hold tight, like an early Ford rear axle hub.

 

In the past, I always dealt with large drill presses and mills in a manufacturing environment. The drills that fit the lathes also fit the large drill presses. I never really gave much thought to small drill presses because they always had an existing chuck that never needed removal. Assumed they were the same. However, here is a guy that deals with the smaller stuff and he knows the correct info for the smaller drill presses. So this video tells you what smaller ones use. Notice that this doen't tell you about making spotfaces or using any shell mill. Good video.

 

Annular cutter.

 

I’ll try to find time in a bit before work to take a pic of what I mean. Currently have a weak signal and can’t upload now, but can when I get to work.

 

The taper of the drill shank never came up to block the drift hole, so the drill could easily me knocked out of the holder taper. Most drift keys were chained to the drill press table so they wouldn't get lost.

 

Yes, they help a lot when trying to drill larger holes with a chuck rather than a direct mounted tapered shank. Notice the 3 flats on the shank of the drill which help the chuck get a better grip on the drill. When using a large drill like that, those flats really help.

 

Those are nice drills. Years back my brother shows up at the shop with a new set of drills he got at a garage sale. They LOOKED nice, but on the first hole he drills, the drill bit folded up like wet pasta.

 

This photo just popped up in the “What Happened to Hilborn” thread, it’s a back facing table used with the cutter shown in the first post here.



You put the workpiece over the spindle, slip the cutter on the spindle and step on the pedal to bring the rotating cutter down on the hole to be spot faced.