Silver and Deming Drills - Need Info

[JWB_Machining]

Hey,

So my Boss and I have a set of Silver and Deming drills. We went to drill a hole in a workpiece on our Haas TL-1 using a Jacobs Precision chuck. The problem we noticed is that the shanks of these drills are much longer (around 1 1/2" longer) than our chuck is deep (lil over 1"). When we tried drilling we got a lot of chattering. However on our old manual lathe we have a Jacobs chuck that goes about an inch deeper than our new Jacobs chuck. So we used the manual lathe for this job. My Boss Called Jacobs and inquired about a deeper chuck but they claim they don't make one, he also called another manufacturer n they said the same thing. So now I'm curious how are Silver and Deming drills supposed to be held or do they have specific applications? Also does anybody know of a Drill Chuck that is deep enough to hold these drills that either has a Morse 4 Taper or can be adapted to Morse 4?

[Geof]

One solution is to hack half an inch off the end with an abrasive chop saw; this is a crude approach and has the disadvantage that the three flats on the shank do not extend all the way along so now the chuck jaws grip on round material.

Another solution, which is my preferred one, is to drill from the toolpost. It is fairly simple to make a holder or use a reducing bushing in the one that comes with the machine.

Regarding the chatter you experienced it is not too likely that the cause was the shank protruding from the chuck. New drills frequently chatter and jump a bit as they first enter the hole but they normally calm down once they are cutting full diameter; unless you have drilled a pilot hole then they tend to chatter and grab all the way in. A pilot hole is not necessary with the Silver and Demming drills because they have a split point and do not require much force to drill. A shallow spot drill to start them on center is a good idea.

[JWB_Machining]

Geof,

Thanks for your help once again. Could you elaborate a little bit more on this tool post or reducing bushing idea? I do have a toll holder that hold collets, I assume for boring bars and such. Could I use this collet holder to hold the drill? Obviously the problem would be getting it perfectly centered with the chuck. Any advice on how to do that? I'm thinking putting a turned down piece of stock in the chuck and adjusting the collet holder until the collet smoothly slides over the piece of stock. Good or Bad idea?

[Geof]

Have a look at the pictures I posted in these threads.

TL1 takes up the slack

Tool Shift for gang tooling

The holders are just blocks of cold rolled steel machined to fit in the turret with mounting holes drilled and reamed from the chuck so they are on center.

If you machine the holder with a step that comes against the upper part of the turret it will always go back in to the same location so all you need to do is make a record of the X position when the mounting hole for the drill shank is done and you have the center position.

After drilling just tap setscrew holes in the top.

I have to admit that these holders aften do not go back perfectly on center but all this does is make the drill rub a bit on the side as it gets deeper. If you are trying to drill a hole to +/-0.001 in size and parallelity this can be a problem but trying to drill to really fine tolerances is not easy, that is what reamers are for.

Holding a 1/2" shank drill in a collet is possible but dubious especially if the cutting diameter of the drill is much larger than 1/2" because the torque needed can spin the shank in the collet, especially if the drill grabs.

For getting boring bar holders on center I put a piece of 1" round bar in the chuck and another piece of round bar in the holder. Bring these together side by side and use either a bit of paper or a feeler gauge between them. The center position when the feeler gauge is just nipped is more negative by the sum of the two raii and the feeler gauge thickness. With care you can get to within less than +/-0.001".