[Mooser]

I need to drill some small holes (.063") into the wrench flats on the head of a handful (16) of 3/8 bolts (.375" dia x 1..250) long. The problem is each part has 2 holes in the end, on two of the wrench flats 60 deg apart
I've got a 4th axis with a 4" chuck mounted to it but I can't get down near enough to the parts for a small drill-chuck. The chuck jaws are too short to allow the part to be held away from the body far enough for clearance of the drill chuck/holders

I'm thinking of using one of the weldon style 3/8 endmill holders I have but the threads are too small and it's sloppy fit, the 3/8 er11 collet chuck will work but again it's too big around to get in there with a small center-drill etc.

Anyone have some suggestions without a ton of fabricating ???
Thanks
M

[MichaelHenry]

Can you use a 5C or some other form of collet in your 4t axis instead? For a job count that small I'd be tempted to use a a 5C hex collet block like this one:

https://www.shars.com/5c-collet-block-set

Along with a collet stop to make the head location repeatable under the spindle.

[Jim Dawson]

I would just thread the end of a piece of the largest bar stock you can fit in your chuck. Maybe taper the end for clearance if needed. Screw the bolt in and make holes.

[kstrauss]

I was running a job earlier today that is worse than your problem; you could use the same technique. I needed to cut 4 slots on the side of 0.125 diameter stock. To get sufficient clearance I mounted an ER16x20mm collet extension in an ER40 square collet block which I clamped in my vise. I only needed a few parts and it took a few minutes to setup and cut each piece.

[Mooser]

Can you use a 5C or some other form of collet in your 4t axis instead? For a job count that small I'd be tempted to use a a 5C hex collet block like this one:

https://www.shars.com/5c-collet-block-set

Along with a collet stop to make the head location repeatable under the spindle.

Unfortunately the 4th is a faceplate with the chuck mounted to it, At one company I worked at we had a 5c 4th axis with a small end around the collet, that would work perfection for this
I played tonight with mounting a er11 chuck into the 4th chuck but it didn't work out well (the 4th chuck isn't what it should be really)
M

[Mooser]

I would just thread the end of a piece of the largest bar stock you can fit in your chuck. Maybe taper the end for clearance if needed. Screw the bolt in and make holes.

I think this might be the only temporary solution, there shouldn't be any forces trying to unscrew it. I'll need to re-index the stock to align the flats but hopefully it'll be quick
Thanks
M

- - - Updated - - -

I do need to invest in some 5c or even er32 collet blocks though
M

[kstrauss]

If you want to use your 4th axis rather than a collet block get an ER collet with MT2 shank (assuming that your 4th is like mine). Add and ER extension if that doesn't give enough clearance. I mostly leave a 5c collet chuck mounted on my 4th and that gives sufficient clearance except for the small work.

[kstrauss]

I think that you'll find an ER40 collet block more useful than a 5c one. On most 5c collet blocks the closer makes it difficult to set a stop on the back side to position the collet chuck at a repeatable location in your vise plus you can't insert a long piece of stock through most 5c collet blocks.

[mountaindew]

Can you use a 5C or some other form of collet in your 4t axis instead? For a job count that small I'd be tempted to use a a 5C hex collet block like this one:

https://www.shars.com/5c-collet-block-set

Along with a collet stop to make the head location repeatable under the spindle.

+1
If I can get it to fit in a 5c fixture format "5c blocks, 5c chuck or 5c in 3-4 jaw chuck" I can literally have my way with it.
If the part is real small and problems reaching features I move to an er 20 tts style holder.
If strange shape or with thin places, I would move to a dedicated mandrel type fixture as Dawson mentions.

[Peter Neill]

An albrecht sensitive drill might be perfect for that, though you feed these by hand via a knurled ring.
Small enough to get close, and a 20mm stroke on the sliding shaft.

https://cdn.webshopapp.com/shops/367...drill-chuc.jpg

[Mooser]

I think that you'll find an ER40 collet block more useful than a 5c one. On most 5c collet blocks the closer makes it difficult to set a stop on the back side to position the collet chuck at a repeatable location in your vise plus you can't insert a long piece of stock through most 5c collet blocks.

True, but I have 5c collets as well as a couple of sets of ER32s, no ER40s
M