Technical Machinists, what is the technical name for this?

I am trying to figure out what this is called. You guys will probably laugh, but I am out of my realm of expertise. I need to buy one of these for a project that is smaller than this one.

This one measures 1.2650 and I need one maybe about 1.250. I don’t even know what to call it. It’s being used as a spot facer on an aluminum casting.

Any help is appreciated. I know you guys will answer this in probably under 2 minutes.

Thanks,

Root

 

Looks like a valve spring seat cutter, without the arbor.

 

Maybe a rotary broach???? BTW I’m no machinist

 

Back spotfacer.

 

I'd like to see how it was manufactured, and the tooling involved.

 

Thanks! You guys rule.

 

My tooling for cutting the counter bore to install valve seats drives and pilots just like that one. Some one has rounded the corners of the cutter off so it leaves a radius in the bottom of the bore. Seat cutters do come in nominal sizes. Sb Chevy with 1.500 exhaust valves use a 1.625 OD seat.
Edit my dyslexia was on. And I miss read the size of your cutter.

 

You can use a end mill but you will probably need one with a reduced shank
This is a 1.5 with a 3/4 shank
Some end mills won’t cut in the center you may need a small pilot hole

 

It's actually going to be turned by hand. It's for a repair in an existing casting that does have a radius. I am having to get ugly with some folks, so I just needed to make sure I know my terminology.

 

At Imperial Eastman "now Parker" we called them Hollow Mills, ours have shanks on to drive em like Oldtmtech's pictures, yours must have had a hollow driver to make chips

 

I know nothing about this at all, but here's some hollow mills as @Tickety Boo mentioned

https://www.carbideanddiamondtooling.com/end.mill.hollow.mill.hss

 

The EM in the pic is not center cutting, high helix flutes will have less chatter, your fixture will be the secret to success. Rigidity is the key. Slow RPMs on manuals. If she squeals she’s hungry… feed her more.

 

Roothawg, is there a set screw comming in from the side to retaine a shank with a pilot ?

 

I don’t believe so. This one has a bolt that uses the tabbed washer to be able to turn it by hand.

 

I believe it's generically called a shell mill. Many different styles and flute counts are available.

 

For that small a change in diameter, get a machine shop to grind down the OD. Those are pricey new.

 

Which then begs the question, what's the name of the special tool that's used to make this tool?

 

A little explantion here, as some tools often do similar things and people get used to calling them by other names. Generally like minded people accept which ever name because they see the tool and get the idea of what you want. When ordering a tool from a supplier though, you need to look at their catalog as they need to be more specific when filling an order.

Generally, a spotface is when you cut a round flat spot on a surface. Normally that spotface is around and usually concentric to a hole......but you can make a spotface on a surface that does not have a hole .....it depend on the tool you use for the job.

Cutting a seat for a valve spring is an example of a spotface, but it uses a specialized tool because you don't want to cut the valve guide off while making the spotface for the valve spring. So the tool must center on the axis of the valve guide but clear the outside of the valve guide and cut the spotface at the base of the valve guide.

To further compound the valve guide tool some of them don't actually clear the external surface of the valve guide but cut it as well as the seat at the base of the guide.

It just depends on what the machinist wants the tool to do.

Getting back to the simple spotface.........it will have either a fixed "shaft" type protrusion or a removable one. Basically we'll say we want to cut a 1" spotface and it needs to be concentric to a .500 diameter hole. A tool with cutting flutes similar to the one in your picture will be used. A .500 diameter round guide "shaft" will protrude from the tool. As you insert the "shaft" into the .500 diameter hole, it will hold the cutting flutes concentric to the hole. A little pressure from your drill press and you have a "spotface".........NOT a BACKspotface. (more on that later)

Another way to make a spotfacing tool is with a hole thru the center of it. Then instead of a fixed shaft protruding from its end, You insert a shaft into the hole and tighen a nut on its end to hold it in place. This is much better because you can have 1 spotfacing tool, but use different size insertable shafts and spotface holes of different sizes.

With a BACK spotface, a person wants to put a spotface on the BACKside of a part. In this case a different kind of shaft is used. You need one that passes thru the part.......Then the cutting tool is mounted on it below the part. As you raise it the "shaft" keeps it concentric, and the cutter makes a round and flat cut on the backside of the part.

As I said, people tend to mix the terminology but when they know what their friend is trying to do, they understand what is meant. There is a company called MSC. They used to have great catalogs where you could look at all kinds of tools and see what you needed. I have a couple of their old catalogs and I held on to them just to look up tech info. I don't think you can get a catalog anymore (they were really thick and expensive). You might look up their website and see what they have.

2 and even 4 or more flute end mills can be used for spotfacing if its around a hole....the hole allows the very center of the tool not to have to try to cut. The bad thing is they often grab and move the part and your spotface is no longer round. It just depends on the type of metal being cut and the size of the spotface.

Hopefully I explained this so its understandable, as its really pretty simple.

One thing I forgot to add, The spotfacing tools often have a special holder that adapts them to a milling machine. Be sure you get something that fits whatever you have (drill press).
Spotfacing tool



Here is a BACK spotfacing video. It has a single cutting edge but others allow you to mount a round fluted tool to the shaft.

 

All the shell mills that I have I use are for lateral cutting, like a multi cutter fly cutter. Those are held with an arbor that has a bolt, typically a cap screw, that is past the cutting face.

What is pictured by the OP is a piloted spot facer. It is designed to cut down., more like a centerless drill, but with a non cutting pilot, that sticks out, to keep it aligned with the hole.

I use these for such things as enlarging the diameter of valve spring pockets for bigger springs, or for making flats for bolt heads, flange bolt heads, or washers, concentric with newly drilled holes, in surfaces that are unfinished, or otherwise irregular.

The quickest way of distinguishing the two is this:

Spot facer: Smooth bore.

Shell mill: Stepped bore, shoulder for cap screw head.

 

https://www.mscdirect.com/browse/tn/Holemaking/Counterbores-Porting-Tools/Reverse-Counterbores-Spot-Facers?mscNew=true&navid=2106110&refinements=Counterbore+Diameter+(Inch):1-1/4

Given that expense, unless you specifically need one to remain at this size, I would, as others have suggested, hand this to someone that can remove the extra diameter, and reprofile the corner.

 

A mill.

 

FWIW, end mills are not ground flat on the bottom regardless of whether they're center cutting or not.

 

Since you're turning by hand, go with good used tooling to save some money. I imagine you're not taking off much material and the job is more of a 'clean up'?
How about something like this so you have a "handle";

https://www.ebay.com/itm/314058028859?hash=item491f51373b:g:cfYAAOSwdV1iv4zt

If it needs detailing after you spot face it, don't underestimate the cleanup detailing you can do with a small grinding stone in a dremel.
Maybe post up a pic of what you're working on.

 

Or a reverse counterbore.

 

<Buzzer Sound> Not a shell mill.

 

I made one years ago for a special job, a stainless steel bell jar used in cryogenics at work. The tool crib gave me a piece of Vega tool steel that was labeled wrong. In heat treat, it wound up being softer that the zero-condition stock. We called it made out of Pinto, homage to that horrid car made by Ford.

 

I am enjoying reading this thread and learning something, too!

 

Appears to be a human male thumbnail, in-artfully trimmed using the biting or chewing action of human teeth.

You cannot buy a small one, but you may be able to borrow a smaller one from a young person. As long as you promise not to hurt or damage it, this is generally considered acceptable.

 

Looks like a machine specific piloted spot face. Possibly for cutting down top of valve seat insert while adding a radius to chamber. Something like a Serti(sp.) There is back clearence ground on the end only so will not cut with the OD.

 

It's actually built to surface a casting on a wing attach bolt. radius matching one on the casting. Airplanes are traditional.

Good times.