R8 Drill Chuck + Screw?

Hi Chaps

I bought a drill chuck for the Myford Mill at the show last week (R8 arbour + Keyed Chuck) and the chuck is just a taper fit with no retaining screw. I'm thinking I need to fit one. Any thoughts/things to bear in mind.?

regards Martin

Hi Martin.

providing we're talking about the taper fitting for the chuck to the mandril, make sure the taper and the hole is perfectly clean (no oil) and dry........put them together with push and twist...thats it job done....some say a light tap to get them to seat together !!!!!!!!!!

clogs

Plus 1 for Clogs post as it is a DRILL chuck.

Emgee

Plus 2 for Clogs, drill chucks don't have a drawbar. If you do give it "a light tap" to seat it (I always do) use a soft mallet and make sure the jaws are withdrawn into the body before you hit it.

Well I cannot say I'm overly convinced. I do get the point about self holding tapers and I'm sure it's going to be better once it's not slathered in oil like it is at the minute. What bothers me is the tap I give to the drawbar to remove the R8 taper and I cannot get images of the trotters and the chandelier out of my mind so i keep seeing the drill taper letting go instead of the R8. Silly I know because I agree with the theory and would not care on the lathe where the chuck is horizontal. Still I will clean it off and give it a go.

regards Martin

I have just swapped a B16 mount drill chuck over from a MT3 to an MT2, it has been on the MT3 for a year. The chuck was opened to its full extent so that I could put a rod up to the base of the B16 taper, gave a sharp tap and the taper released ( as expected). Then a quick wipe on the B16 with MT2, place it in the chuck, a quick tap on the bench with the MT2 small end, job done.

Always done it this way and never had anything come off. intact it is usually the other way round, trying to get the !!!! off.

Just remember its a DRILL chuck. Dont ever think you can take the lazy route and do a quicky milling job with the drill chuck holding a milling cutter

Martin

It is a drilling chuck, the pressure on it is axial. The pressure on the drill pushes it into the taper.

Oooopsie!

Andrew

Does using a slot milling cutter count? I have to admit to using them for small counterbores, on occasions. Would agree that using the cutter's side faces is not to be recommended, with a drill chuck.

Pete

Never ever had a properly fitted chuck come off its arbor. A light tap on the draw bar top will free a R8 taper.

Tony

According to Wobblypedia "

R8

This taper was designed by Bridgeport Machines, Inc. for use in its milling machines. R8 tapers are not self-holding, so they require a drawbar extending up through the spindle to the top of the machine to prevent loosening when lateral forces are encountered. They are also keyed (see image) to prevent rotation. The drawbar thread is typically  ⁷⁄₁₆″–20 tpi (UNF). The angle of the cone is 16°51′ (16.85° with an OD of 1.25″ and a length of  ¹⁵⁄₁₆″.^[13] (source, Bridgeport Manufacturer) The resultant inner diameter is slightly over  ³¹⁄₃₂″.

Tools with an R8 taper are inserted directly into the machine's spindle. R8 collets are typically used to hold tooling with round shanks, although any shape can be held if the collet has the correct corresponding shape cut in it. The collets have a precision bore with axial compression slots for holding cutting tools and are threaded for the drawbar. The R8 system is commonly used with collets ranging in size from  ¹⁄₈″ to  ³⁄₄″ in diameter or tool holders with the same or slightly larger diameters. The collets or tool holders are placed directly into the spindle and the drawbar is tightened into the top of the collet or tool holder from above the spindle. Other tools such as drill chucks, fly cutters, indexable insert cutters, etc. may have an R-8 taper shank built into or added to the tool.

The R8 taper is commonly encountered on Bridgeport and similar turret mills from the USA, or on (very common) copies of these mills from elsewhere. The popularity is due in large part to the success of Bridgeport and other mills that were closely modeled after it and produced throughout much of the 20th century."