Modify an end-mill holder; cut off tang and add draw-bar threads....

[brino]

Hi Gang,

I just picked up two new, old-stock B&S #11 end-mill holders.
I couldn't get them in draw-bar style, but that's really what I need.

I would like to put a 5/8-11 threaded hole for my draw-bar where the tang end is now.
You can see that I tested one tang with the corner of a file, and it should be machinable.
And I will be sure to not cut/drill into the end-mill pockets (some are deep for using double-ended end-mills).








I had two ideas for modifying them:

1) on the lathe
mount an appropriate bar in the lathe 3-jaw chuck
put the end mill holder on the bar and tighten the set-screw(s)
put the tail-stock centre into the hole on the tang
start the cut-off operation with the parting tool, stop early and finish on band-saw

However, then I cannot drill a hole for the draw-bar on the lathe as there's no good way to hold it.
I suppose I could find a way to hold them vertically on the drill press for drilling, the draw-bar does not need to be exactly on centre.

If I had a fixed steady rest, I could first turn a cylindrical section near the tang-end to run in the steady rest for drilling.....but I don't!
other ideas?

2) cut off the tang with angle grinder and TIG weld on a coupler nut for the draw-bar.
Not as pretty, but functional.....

Anyone got some useful experience or advice?

Thanks,
-brino

 

[T Bredehoft]

Both holders appear to have a cylindrical area near the tool, hold that in the chuck and very carefully spot and drill for your 5/8 thread once the tang is cut off. Or am I missing something?

 

[JimDawson]

^^^^^^ What Tom said

 

[Chipper5783]

Make a nice fitting taper bore sleeve (OD not critical), then chuck a suitable bar (larger than the endmill holder size) and skim the bar to a close fit to the size of the holder - do not unchuck that mounting pin - it is now perfectly aligned to your lathe (the flats for the set screws are important, but they can be crudely added with a file). Mount the sleeved end mill holder on that new mounting pin, with tailstock support - skim the mounting sleeve OD for a steady rest. Remove the tailstock and part off the tang (could even cut it off with an angle grinder) - then clean up the end to suit, drill and tap.

Let us know how you make out.

 

[darkzero]

When I need to shorten & face off the tang end of morse taper shanks I use a MT straight sleeve. Seat the arbor in the MT sleeve real good & hold the straight sleeve with a chuck. You could try making a similar sleeve with the OD larger than the endmill holder OD & see of that will hold enough.... assuming your chuck through hole & spindle bore is big enough to fit the head of endmill holder. I've never needed to drill & tap the end of an arbor with this method though but I have taken semi heavy cuts & it held fine.

 

[cathead]

You could start the drilling procedure using the centering hole. I don't see much value in cutting off the tang. I have a MT4
arbor with 1/2 x 13 draw bar hole machined that way and the tang is still usable if you ever need it. I guess you would have to
see how much meat there is on the end to see if 5/8x11 would be workable in your case. Just curious, Brino, what kind of
machine are you using this in?

 

[brino]

Thanks for all the replies.......

Both holders appear to have a cylindrical area near the tool, hold that in the chuck and very carefully spot and drill for your 5/8 thread once the tang is cut off. Or am I missing something?

What Tom said

Tom and Jim,
Sorry I did NOT include a scale in those pictures, but these tool holders are 10 and 10.5 inches long.
I guess it just feels wrong to have so much unsupported work hanging out of the chuck.

But I suppose your logic is that I'll only be doing drilling, with no side forces; so no problem.
I will chuck it up and see how it feels/looks.....

Mount the sleeved end mill holder on that new mounting pin, with tailstock support - skim the mounting sleeve OD for a steady rest.

Right, but I do not have a steady rest........
Building one is on the never-ending project list though.

When I need to shorten & face off the tang end of morse taper shanks I use a MT straight sleeve. Seat the arbor in the MT sleeve real good & hold the straight sleeve with a chuck.

Will, what a clever trick that is!

.... assuming your chuck through hole & spindle bore is big enough to fit the head of endmill holder.

Nope. The spindle thru-hole on my SouthBend 9" is only 3/4 inch.

Just curious, Brino, what kind of
machine are you using this in?

This one: https://www.hobby-machinist.com/gallery/img_3548_cropped.94577/
A 1916 Cincinnati 3S. Both the horizontal and vertical spindles are B&S #11.
Neither have any drive for a tang.

It's tough to find original B&S tooling at reasonable prices, so I bought 4 end-mill holders and 3 shell mill holders of different sizes recently when I found them. Most are threaded for the 5/8"-11 draw bar. Only these two need to be modified.

Thanks again!
-brino

EDIT: Previously I was using stacked adapters; like a B&S #11 to MT4 sleeve, then a 3/4" MT-4 collet with draw bar. Besides the loss of Z movement and the compounding inaccuracies, I once had an B&S #11 adapter sleeve stuck in the vertical spindle. I had forgotten to put on a little "top hat" adapter I made that the draw-bar goes thru. That top-hat gives me a way to slide a solid shaft thru the spindle to knock-out the whole works....but here I couldn't get it to catch on the stuck sleeve due to the taper shape of the hole in the spindle.

These "new" tool holders should simplify everything!

 

[RJSakowski]

I drilled and tapped an MT@ to JT3 adapter for a drawbar years ago. I left the tang on.

I would use the cylindrical portions for holding in the chuck. Use a center in the tang to center the far end while clamping. You should be able to drill and tap without problem. At the speed you will be running, I wouldn't worry about the unsupported length. A steady rest would be nice but the drill will keep the part centered.

 

[projectnut]

When attempting to drill and tap the hole I would think you would want to use either a 4 jaw independent chuck, or a "Set True" style 3 jaw chuck. Most standard 3 jaw scroll chucks have some runout. .003" runout is not uncommon. I would think drilling and tapping the hole even slightly off center would at the least make it more difficult for the drawbar to engage the threads, and if the runout is excessive might bind the holder in the taper.

 

[RJSakowski]

The existing countersink will ensure that the start of the hole is properly centered. A hole drilled and tapped at .003"/10" off true centerline will not cause a problem for the drawbar. There is easily that much play in the threads.