What is the Chuck Taper Size? MasterForce model # 240-0064 12" Drill press

The chuck could be threaded like an average power drill.

Respectable drill presses use a hollow quill shaft that is likely to be machined into a taper that is likely to be number 1, 2 or 3 Morse taper.

Morse taper drill bits are used a lot - the shank is tapered and will grip and drive when inserted into the quill with just a small force. When the bit is to be removed the quill is turned by hand until a slot in the quill lines up with a slot in the housing and a wedge-shaped steel tool is slid in and tapped breaking the taper fit.

Most such drill presses are supplied with a chuck for light duty drilling already mounted. The chuck is often a Jacobs type mounting by means of a Jacobs taper onto a Morse taper adaptor.
The adaptor is tapered at both ends - at the lower end the taper is steep and the chuck must be pressed on with some force. The upper end will have the same gentle taper of the Morse taper drill bits and is removed in the same way.

Using the chuck drilling is limited to the capacity of the chuck, typically 1/2" or 5/8" unless blacksmith's drill bits are used that have stepped shanks.
Morse taper drill bits will allow heavy duty drilling far in excess of the chuck capacity.

Hopefully your problem is caused by the chuck rather than a bent quill.

16 speed should have a Morse taper
for the std drill chuck

to fit a different chuck the morse taper needs to be emery sanded
and the replacement chuck should stick
after using the wood block pressure press method

if not you need a new morse taper for that spindle chuck


hint
i had my drill accuracy and off center spin tolerance down to one thou

with stretched old belts I got more speeds than 16
for special jobs
my 16 speed used a morse taper two for the drill chuck


this picture says its a spindle chuck
morse taper

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If its possible, pop along to a local machine shop and ask nicely if they could help with identifying the Morse Taper, if its a Morse. Go online for what tapers would have been used around that period. Drill chucks are usually 1/2 UNF mount even if its a late metric unit. You would need a Morse to 1/2 UNF or taper to taper if you buy a taper fit chuck.

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the drill press shaft has a taper in the end and a slot in the side The chuck you will use will have a taper in the back and the adaptor will be tapered to fit in the shaft. The slot is to put in a tapered drift to remove the chuck assembly so that larger drills with tapered shanks can be used. Most twist drills stop at 1/2 inch but reduced shank drills are available with 1/2 ''shank but a bit size up to say 3/4'' After that you will need taper shank drills.. If the drill shaft has a hole from top to bottom you can use special router bits that allow for ma threaded rod to hold them in during milling otherwise the chuck will vibrate and come loose and fall out. It is essential to select the right speed for the drill size being used and I have found that by using combination vices that allow the job to be moved in - out and side ways the jobs you can do are limited by your imagination

I would chuck a good size steel pin, unlock and swivel your table over to the side, clean both the taper and the socket with brake cleaner spray or electrical contact cleaner (or even Fondu Alcohol Fuel will work) to leave no oil film at all on the parts. Also run a stone around on all the male part taper surface to check for invisible burr spots and dents left when it was tossed around during manufacturing. Dry every bit of cleaner out by waiting or blowing with a hair dryer. Then tap it in with a piece of wood against the steel pin bottom. Professional shops can make the taper match so it will transmit 5 HP or more without spinning or falling out, but many workers today just don't get the quality training or buy the measuring tools to be able to do that. My Chineese machine didn't even have the draw bar threaded with the matching thread to lock in the chuck in for it's milling head, so you know they are not a detail oriented outfit. Great Guns and all facing the one way!

You should really be using end mill tool holders for milling. The torque is too great for drill chucks. You will get better results machining with surface finish, size as well as longer tool life. Side note..take care with reassembly of drill chuck. Tapers must be dirt and burr free or chuck will have run out as well as taper lock will break and come apart on you more often. If there is damage to the tapers replace the arbor and or chuck with new.

without the model number I am going to guess that as a general rule most smaller drill presses are a #2 morse taper socket and a #2 jacobs taper arbor (where the chuck presses on) you should have been supplied a knockout pin to remove the chuck assembly from the internal socket.

Grizzly sells a nice variety of quality chucks at good prices. Look at the numbers on the chuck you have to determine what to buy. You should remove and re-use the taper from your present chuck. You probably have a Morse #2 taper up into the spindle like the picture shown below. I assume you know how to get that out of the spindle. What is not shown in this picture is the taper that is inserted into the chuck. This is probably a Jacobs taper. To separate that you need to support the chuck in a vise with the long taper pointing down. Put something below it to catch it without damage when it falls out. Open the chuck as far as it will go. Get a bolt (about 3/8) that you can hit with a hammer inside the chuck straight down to knock the taper out of the back of the chuck.