adjustable tailstock 1/8" drill holder for sherline

[ttrikalin]

I have broken more small carbide drills than I care to remember while drilling on the lathe.
I use small diameter drills with 1/8 shank purchased for peanuts from Horrible Freight. They break because of suboptimal headstock to tailstock alignment. The alignment in my Sherline is 5" off. I am typically using the tailstock chuck, which adds some misalignment of its own.

I decided to make an adjustable 1/8" drill holder for the tailstock. It emulates several adjustable tailstock tools sold by Sherline. I made it out of a 3/4" steel bar -- it would be better if it were a bit bigger, but this was the only stock I had. I wish I had taken photos while constructing the tool. These 2 are the only ones... Here i bore the hole that will accept the shank of the drills. I'm using a home made mini boring bar, held in a microtool holder built as per Luis Ally's instructions:

Needs patience, the boring bar is small, shaves two thou at a time.

This is the adjustable tailstock drill holder. I use two broken bits for alignment. The purple one on the left is held in a collet on the headstock - this is the spindle axis (my headstock is parallel to the bed better than 0.0005" at 3 inches ). The blue broken bit on the right is positioned to match the spindle axis, by loosening the two socket screws and moving the holder head a bit.

After a couple of minutes the alignment is quite good. Under 10X magnification:

I center drilled a 0.044" diameter tube (hole 0.026"), which is part of the air supply for my 1/4 scale version of Elmer's Tiny... soon to come.

More soon...

take care,

tom in MA

 

[peatoluser]

what a clever idea. Have a similar problem with my taig lathe. When i've finished any offset turning with the tailstock, i've always found it a pain to realign it using a DTI. Know which method i'm going to be using from now on! Thanks for the post.

yours

Peter

 

[Jasonb]

Is it just me or does the hole in that tube look well off centre ???

I think I would find it hard to visually align the ends of two broken drill bits, would it not be possible to hold a straight 1/8" bit of drill rod or an old drill shank in the collet, grip the other end in your holder with the adj screws loose and then tighten them up, this should get the two 1/8" holes aligned well and quickly

Jason

 

[ttrikalin]

Is it just me or does the hole in that tube look well off centre ???

I think I would find it hard to visually align the ends of two broken drill bits, would it not be possible to hold a straight 1/8" bit of drill rod or an old drill shank in the collet, grip the other end in your holder with the adj screws loose and then tighten them up, this should get the two 1/8" holes aligned well and quickly

Jason,
The tube has been parted off with a mini cut-off tool and then passed on a diamond file to remove the burrs - the hole is centered, but its entrance has a flattened burr that has not been removed completely. I may take a pic under the microscope before assembling the engine.

As you said, visual alignment is a tad tricky -- the solution you propose is very smart, superb!

thanks for this pointer,

tom in MA