MT2 shank x 3/4" end mill looking for good home

[J Tiers]

Hahaaa! I am sorry, Welcome.

My point was you said reamers dont cut on the face and I thought they did.

The 45 lead is correct, its sharpened to be the first cut. The 45 lead in angle is the cutting face. That is how you might determine if a tool is a reamer or an end mill.. You folks are Bat Chit Crasy. And I Like it. JR

Maybe.....

The 45 deg is for reamers that are to follow and "improve" an existing hole. For a "reamer" that is to essentially bore an accurate hole regardless of the accuracy of the existing hole, which would be the case for a jig borer, the 45 deg taper might be bad, as it could provide a side force trying to shove the reamer into alignment with the existing hole, creating inaccuracy, as well as a non-flat bottom to a blind reamed hole.

So a "jig borer reamer" might look a lot like an end mill, since it needs to "ream" the hole directly on axis with the spindle, regardless of existing holes. In fact, end mills are still used for that sort of purpose, particularly when a counterbore is needed on a non-flat surface, and the like. The existing hole would only be there as clearance for the non-cutting center of the "reamer".

My question to you is how does one determine which is being looked at?

If a manufacturer calls it an end mill, that does not mean it cannot be used as a reamer/boring device. Presumably, the difference may be that the "reamer" is the same thing, but made very accurately as to diameter. Otherwise, if diameter is not precise, why does it even exist, how is it better than a drill?

[Richard P Wilson]

Doozer now says that a jig bore reamer has a back taper of maybe 0.003", so the leading end is a larger diameter over the flutes than at the end nearest the shank. As he now seems to have given up on his earlier claim that an endmill has a B&S shank and a jig bore reamer has an MT shank, then that seems to be the difference. Visually then, they seem to be identical, unless very carefully measured.

Unless they are much more precisely made than an endmill, how is the much higher price when new, justified? I suppose the diameter would need to be very carefully controlled, for a reamer, more so than for an end mill, where, for most work it isn't that critical.

[J Tiers]

Only type of "end mill" shown:





In the 1971 edition, there are numerous of what we know as "end mills", and one lonely small chart of the taper shanked ones.

[Doozer]

Machinery's Handbook has no data on R-8 taper dimensions either.
No wonder they missed jig borer reamers.

-D

[old mart]

Perhaps Paul, in post # 72 could explain how to mill avoiding "interrupted cuts"

[J Tiers]

Machinery's Handbook has no data on R-8 taper dimensions either.
No wonder they missed jig borer reamers.

-D

As that is a 1938 book, and Bridgeport Machines (developers of the R-8) had just started out that year, presumably the R-8 was simply not yet out in industry when the book was compiled.... The authors were documenting what EXISTED in use.

Sorry to bust your pretty bubble....

Perhaps Paul, in post # 72 could explain how to mill avoiding "interrupted cuts"

With most end mills, the cutting edge is a helix..... So as soon as the cut is established, and sometimes even as it starts, the cut is continuous, i.e. there is always an edge in the material cutting, no time "just cutting air".

How fast that occurs is dependent on the depth of cut relative to the helix. A deeper cut will have always at least one edge cutting.

[Doozer]

I have never seen a later edition that listed R-8 either.
Don't have to be sorry. My bubble is still intact.

-D

[SVS]

This controversy inspired me to pull this hard bound supply catalog off the shelf. Seems to be from ~1920.

There were NO straight shank endmills listed OR taper shanks with drawbar threads. Being a general supply catalog I don’t claim it to be an exhaustive list.

[J Tiers]

OK, the end mill arrived. And of course I had to test it!

It's not over-sharp, and it also did not fit the mill until I reduced the diameter of the tang on the back somewhat, since that sticks up into the nominal 3/8" bore for the drawbar normally used.

So...............

I did two cuts with it.

I installed it, and "tunked it" in place with a lead hammer (can I still say that word "lead" in these "extra-woke" times?).

First I decided to go for it, and attacked a piece of mystery steel with a DOC of 0.1". I figured that would not do well. There was a good bit of vibration, and sure enough, partway into the cut, before getting to a full diameter cut, it loosened up. Pic # 1 shows it loose. It actually simply stopped turning when it loosened.

OK, so then I went down to a DOC of 0.025". That is probably about where these things were really meant to work, since back then there were horizontal mills if you needed to hog off serious material. With that, not a problem in the world, it cut right across the material, and is as tight as when it started. Pic # 2

The preliminary results are not far off what I figured. Given the fact of machines easily available to handle serious metal removal, I figure that surface work would be something that an end mill in a vertical spindle machine would do well, and a horizontal mill would not do well, through not being able to keep two teeth in the work. Yes there are helical milling cutters , I have several, but those are wider if they can keep two teeth in the work at shallow cuts.

Since I was able to use it in only a Benchmaster, while the machines available back when these were in the catalogs included heavier vertical mills, I am thinking that the Benchmaster vibrated when a bigger mill (but not a "wet noodle B-Port") probably would have been steady. The vibrations seem to be the obvious culprit.

I'll continue the testing as time allows.

[BCRider]

Wonderful!

And I'm sure that the dullness of it means that when new it likely would have been OK with a few thousandths more than the .025.

I'm pretty sure that my mini knee is heavier than your Benchmaster. And even my mill complains a lot with a full diameter 100 thousandths cut with a 1/2" end mill. And this is 3/4. So yeah, 100 thousandths was "above and beyond" for sure.

[J Tiers]

The Benchmaster is actually very stout, and freshly scraped-in as well. But not as good as an early vertical mill, most likely.

So, I did a side cut also. About 25 thou deep, and 0.4 deep or so. It did fine, until we hit an area where the DOC suddenly went up quite a bit. Then it cut for a while, and dropped out again.

[J Tiers]

I decided to check taper fit. Not great. Here are 4 pics around the taper. I am not sure what is at fault, I suspect the socket, and will check. I have a reamer to do MT2.

I would expect that there would be a problem with side loads given where the contact ends. Not a thing up by the thin end of the taper.

I do not think I have an MT2 socket gauge, I do have one that IIRC is MT3. I'll check.

[Richard P Wilson]

Given that taper shank endmills were common in the 1930s, when horizontal mills were common than verticals, I'm wondering if originally they were intended for use plugged directly into the horozontal mill spindle, with a centre in the outboard support, which would stop the cutter coming adrift? Just a thought.

[J Tiers]

I have checked put the taper socket, and it appears to be needing some help. I did a preliminary slight ream, and the contact area has gone up by a factor of about 4. I am still evaluating, and expect to determine the status, make the remediation if needed, and give the end mill another go shortly.

I had not done anything to the taper socket before, since it caused no issues with a drawbar. However, it may be useful to correct it if it turns out to need action.

The taper gauge is not for an MT2, so I cannot gauge the end mill shank. I may have an MT2 male gauge, but that too may be for MT3. I'll look to see.

I may also sharpen the now somewhat dull cutter. A dull cutter requires a lot more pressure to cut than a sharp one.

Given that taper shank endmills were common in the 1930s, when horizontal mills were common than verticals, I'm wondering if originally they were intended for use plugged directly into the horozontal mill spindle, with a centre in the outboard support, which would stop the cutter coming adrift? Just a thought.

There were in fact longer steeper helix versions used in that way. They are found in some of the same catalogs that show the end mills.

I have no information to suggest that the end mills were meant for that use.

[mickeyf]

I suppose by now this is Way Off Topic...

I have cut one male MT2 using the taper turning attachment on the lathe and found that you have to be correct to about +- 2 seconds of arc. The only way I got it right was with a new socket and engineers blue, plus patience.

I don't have a taper turning attachment, and didn't care what the actual angle was supposed to be. Did this:

Chuck up a known good (factory made?) MT taper.
Align compound rest to indicate true to that, taking care to be at dead center height of the taper.
Now use the compound rest to cut your stock to match the taper you just indicated to.
The compound rest on my 12" lathe had just enough travel to do a MT3.

I have done a handful of these this way, pretty quick and painless, and the resulting tapers worked fine.