Thread: Jacobs taper adapter

Has anyone ever seen adapters to change a small jacobs taper to a larger one, as in some kind of sleeve? I have a southbend drill press with a jacobs 33 taper built into the spindle. The largest chuck I can find to fit a jacobs 33 maxes out at 1/2 inch. I would like to use a chuck that goes to say 3/4 inch. The reason is I plan to do light milling and I have obtained a pile of large new single end mills. Machine power is not the issue. As I said light milling. Even a brand new jacobs superchuck uses a #3 taper. Seems to me since I am going from small to large, a sleeve about an inch long would work. Jacobs 33 on the inside and say a jocobs 3 or 4 on the outside. Somewhere in this world, this problem has been solved before. Suggestions would be welcomed.

Ähheeeemmmm , such an item could be made, no sweat...
Still, bad idea.

First rule: You dont put an endmill in a jakobs chuck. Let alone a big one....
Second Rule: You dont expose a taper without drawbar to side forces.Let alone a short taper....

And yes.....this happens. Was filing round the edges of some 8mm threaded rod in a drill press, huge overhang. (Was at a place i had no acces to a lathe) Clank plonk boom, the chuck fell off the spindle and hit the floor. The radial loads and the associated flexing disengaged the jacobs taper....

Ditto. It's a good recipe for catching the chuck in the teeth. Years ago my cousin was polishing the cylinder from British Webly .45 in a sears drill press, had the speed cranked all the way up, when the chuck let go. It hit him square in the chest, and it looked like someone had hit him with a hammer. If it would have hit him a bit higher, it would have killed him.

Dennis

Some Sears and Rockwell (and probably other makes) drill presses had a 33JT chuck mount with a threaded locking collar that made it safe to put a side load on the collet chuck, drum sander and shaper cutter arbor they sold for those machines. Any other drill press spindle design is an absolutely dangerous thing to side load.

Larry

Nahh

Its not that bad. On our trusty lil old drill you can do bout anything.
The motor is 1/4 hp , high speed can't be more than 1000 rpm.
The Jt is seated so well, you cant get it off, even if ya want to.
Brushing , Sanding etc. are no problem there, its worn to hell (80 years old) but one sweet machine, easy to use and safe by Design. Aint got the speed or the power to hurt anybody.

Lots of ideas here. However the pursuit must continue. A mid 1940's southbend drill press is built like a brick ****house. I am sure it can sustain some side load, especially when the quill is not extended. As I said before light milling. I am sure a couple hundred rpm will do just fine. Looking at a jocobs superchuck , I see it has a thru countersunk centerhole. Since I have a southbend lathe, I could put the spindle arbor in it and bore and thread the j33 taper with a 10-32 thread. Then use a countersunk allen screw thru the chuck, much the same as is done on many electric drills to keep the chuck from comming off. Hence back to my question, where does one find the adapter?? Since I don't have a taper adaper for my lathe, me making it is out. Any more suggestions.

"I am sure it can sustain some side load, especially when the quill is not extended. As I said before light milling. "

No, it will not. You are not only going to risk injuring yourself (which will probably be a good lesson, since all these guys have warned you already), you are going to beat the spindle bearings out of your drill press in short order. A SB drill press is built like a Buffalo, old Craftsman, or many other decent old drill presses, it is not built for milling. You are also going to wallow the taper on your machine and ruin the spindle. As for how heavy it is built, my 7,000lb 3hp Fosdick radial drill with a 3" spindle is not built for milling either, and will do no better if you are naive enough to try it.

Drill presses are made to take thrust loads on the spindle, as the drill itself takes the radial load in the peripheral lands. A milling machine has much larger and beefier bearings capable of handling heavy radial loads that will be created by milling. The table of the drill press is also nowhere near stable enough to handle milling loads without turning around the column and flexing downward. There is no adapter as you describe because you have 1/2" capacity drill press. It has a lowest speed suitable for a 1/2" drill, not a 3/4 and it probably doesn't have near enough hp to pull a 3/4" drill at anything near a reasonable feed rate.

You are going to ruin every endmill you put in it. You know how a drill will sometimes wobble around and make a five sided hole when you first start it? That's due to the lack of radial stability in a drill press quill. Now multiply that times ten and that's what your drill press is going to do when you put a 3/8" endmill in it. Times 100 for a 3/4" endmill. Everytime it tries to make that five sided hole, the endmill will grab and bite in. It's going to snatch the table around the column, break the endmill and probably bend your spindle.

You are going to ruin your chuck. Drill shanks are soft, so the chuck bites into them to drive the cut. Mill shanks are hardened HSS, cobalt, or carbide. They are harder than your chuck jaws and are going to round over your chuck jaws as soon as you tighten them hard enough to prevent slippage. First time you spin an endmill, it'll really do the damage, rolling the edges of the chuck and knocking it out of round. Milling machines hold endmills with collets or endmill holders for this reason.

As if inferior bearings are not enough, hanging a 18N Superchuck on a machine this small is going to run your overhang out about 7" by the time you get an endmill in it. Milling machines use a collet instead of a chuck to keep the overhang and resultant load increases to a minimum. Imagine trying to turn a 3/4" shaft in a lathe that is sticking out 7" long and you might understand what this means. It's like putting really long wheel extensions on you car and eating up the wheel bearings. Also, the endmill in this chuck is going to grab and make a circle around the point where the cutter bit, probably slamming the table around the column, breaking the endmill, gouging the work, and possibly bending your spindle.

We are all trying to keep you from ruining your drill press, ruining all your endmills and possibly hurting yourself. Do what you like, but I'll assure you the outcome is not going to be what you expect.

Originally Posted by curious george

Lots of ideas here. However the pursuit must continue. A mid 1940's southbend drill press is built like a brick ****house. I am sure it can sustain some side load, especially when the quill is not extended. As I said before light milling. I am sure a couple hundred rpm will do just fine. Any more suggestions.

You refuse to listen to the voice of experience, so..........
Before your first attempt at milling on a DP, take out a sizeable life insurance policy, naming Don at Practical Machinist as your beneficiary.

I really appreciate all the thoughts, but maybe I should clarify a bit. A man with a big trailer mounted pressure washer once told me " You can do just as good as I can with a cheap unit from Home Depot but It will take a lot longer". This is my point. Very light milling, probably on soft materials at a very minscule rate. Spindle bearings are not a problem as they are cheap and easy to replace. Acurracy needed is maybe on a 1/16' scale. I recently found out while putting the spindle back togeather with new bearings, that Southbend has already treaded the taper for a locking screw.

I should point out that I graduated tech school as a machinist, worked at Walter Kidde as a machinist for years, and then got lured over to electricity by General Electric. Been pushing electrons ever since. If I wanted a milling machine I would just go buy a brideport, but If I wanted to make a slot in thin aluminum, I will use the drill press. If need be I would put the milling attachment on my southbend lathe and then put the 3/4 mill in either a collet or the chuck.

The fact of the matter is that drill presses, and drill press spindles, aren'd designed for side loads. And you compound the problem by exceeding machine capacity. The facts:
1. Drill presses do not have spindles, bearings, speed range, or frame rigidity to handle milling.
2. Jacob's taper chucks aren't designed for side loads. You can get away with sanding drums on wood at low speeds, if you have a collar on the JT33. But larger Jacob's tapers, and certainly Morse tapers, don't have collar locks. So you chuck WILL come loose under side load. It's not even a question. It WILL come loose. Mr. Murphy being active here, it will come loose two minutes before you finish, after you've put 30 or 40 hours into your project. Just about the time you say "Aha, I'll show those know-nothings at PM. As soon as I finish, I'm posting a picture of this beautiful piece of work!", the chuck will let go, and your end mill will drill through the work piece, your DP chuck, and the DP table.
3. Any machine has spindle strength limitations. There's a reason the designers didn't put an MT3 or a JT3 or JT4 on that spindle. If they could have put a higher-capacity spec on their machine, don't you think they would have?
4. An end mill is designed to be held in a tool holder, not a collet chuck, and not a jacobs chuck. Chuck jaws don't get a good purchase on mills, and the tool slips. And drills into your work, chuck, table, etc.

So you are exceeding machine capacity in four dangerous ways. Dave Utidjian recently posted a note about a putting a large chuck on a JT33 spindle, which promptly broke and sent the chuck flying into the wall. You are proposing to do exactly the same thing: hanging a chuck much larger and heavier than the one the DP was designed for, and using the contraption with a side load. Your rationale (previous post) is undercut by the fact that you want to put a friggin' massive 3/4" chuck WITH A 3/4" END MILL IN IT. Dude, this is NOT "Light milling".

If you convince folks here that this is a righteous plan, let us know. If it works, I'm putting a 5 inch diameter, 6 inch wide slab mill into my Ryoki wood planer. I only want to take 1/4 inch off of schedule 160 pipe flanges, so it should work....

You wrote in, asking for advice. You've heard from several people who have a lot of experience saying that the proposed course of action is not only not practical, it's not safe. Is there not an alternative way to achieve your goal?

monkey see. monkey do

"" You can do just as good as I can with a cheap unit from Home Depot but It will take a lot longer"."

Comparing a large pressure washer to a small presure washer, I totally agree. Same goes for big and small drill presses and big and small mills. Comparing a drill press to a milling machine is like comparing a screwdriver to a cold chisel.

If you were trained as a machinist and learned anything from the training, you should be able to clearly see the dangers and problems with what you propose. How many times did you put a Jacob's chuck in a milling machine and chuck up an endmill?... why not? How many drill presses have you seen set up for milling in the past?... why not?

Good news is somebody might get some South Bend drill press parts out of this for a restoration, once you blow this one up.

here here!

I know from experience, they DO come out!

Originally Posted by curious george

I should point out that I graduated tech school as a machinist, worked at Walter Kidde as a machinist for years, and then got lured over to electricity by General Electric.

Based on the statements you made above, you should have known the answer to the question before you even asked it.
A 3/4" endmill would probably be exceeding the limits of the milling attachment on a SB lathe as well.