The Home Machinist!

Hello all,

The tapers we discussed are (for now at least) getting replaced with flat-bottomed holes. Think of starting with round stock, put an endmill in the tailstock, and crank on the ram for a while; do that from both ends until the holes almost meet. End up with a tube that is blocked by a disk, then drill a small hole in the disk.

Just for grins, is there any reason I could/should not do the above? I am thinking of using an endmill in the tailstock to do the roughing. Is that safe? For now, my 3MT options are drill chucks; I bought a Rohm that is not too bad.

After roughing, I plan to use a (yet to be ground) boring bar. Can I leave 10 thou or so and then take a final cut that takes a little off the ID and then faces the bottom of the hole? Any pointers?

For the future, what do you think of

http://www1.mscdirect.com/CGI/NNSRIT?PM ... O=57240979

I have a nice set of ER32 collets, so it or something like it would be nice to have.

Bill

I have used an endmill in the tailstock chuck but be aware that the quill in the tailstock has slop in it and you may have to snug the quill lock to keep the endmill from jumping around.

What's wrong with drilling it all the way from one end, or, do you plan to leave the "disc" in the center of the hole?

Try it on some scrap first. End mills can create some nasty chatter when drilling. Clear the chips often, use a steady rest if the part length is very many diameter multiples.

Schwabw:

The shank of an end mill is harder than drill chuck jaws. One slip of the end mill is a quick way to ruin a new drill chuck.

Plunged end mills do not leave a flat bottom holes - they are factory ground on the bottom with anywhere from 1deg. to 3deg. toe-in which is why they leave a marked circular track and are able to cut a path with the end.

Due to the toe-in, instead of a leading point, standard end mills do not plunge well and tend to walk in an off-center circular path. This tendency is only made worse by the "conventional mill" effect.

Sometimes things can be more shits than giggles.

Take Care,

Amigo

What Amigo said, although the chance of ruining a drill chuck from spinning isn't of too much concern. Because the jaws and shanks are both hardened, it generally just spins and shines up the shank a little. Still, not a good idea. Drill chucks, unless they are made for gripping heat treated items (there is such a chuck), should not be used with hard shanks. If you must do so, avoid heavy cuts.

End mills, even center cutting end mills, do not make good drills. The geometry is totally wrong, so you often experience chip stacking, stopping any cutting action. That can also yield a ruined part, when the end mill is forced off center by the loaded flute, creating an over-sized bore. Remember, end mills are sharpened to cut on the periphery, unlike drills and counterbores.

The problem with drilling with an end mill revolves around the large size of the center of the end mill, the part that would be considered the web on a twist drill. While some end mills are center cutting, there is limited space for the chip when it is plunged, so loading of the available space often leads to chip welding to the end mill.

If you'd like to use an end mill for cleaning up a hole, do so after roughing with a twist drill, so all you do is remove the taper of the drill point. Better yet, grind a flat bottom drill, the same size as the desired roughed hole, and use it after rough drilling with a standard twist drill. Drill the standard drill shy of the desired depth (at the point), then clean up the bottom with the flat bottom drill. That will leave a surface that is ready to bore and face.

The use of flat bottom drills is something I recommend anywhere that would require the use of a pilot, except for spot facing. If you can drill deep enough to produce the drill diameter, a flat bottom drill will out- perform any other means of metal removal.

It's easy to grind a flat bottom drill---it can be done quickly, by hand. No special grinding equipment needed. All you need is a dressed wheel, a square and steady hands. I recommend a separate drill index be kept for such drills. Once ground, they have many uses.

Harold

I see nobody has tackled your er-32 chuck idea yet, so I'll take the first shot. There was discussion elsewhere a couple of weeks ago about this. Can't remember if it was here or HMEM or HSM. Anyway, since this style of chuck will not allow the stock to pass through the spindle, the consensus was that a different style of chuck would be preferred.

LMS has a couple of er-32 chucks that will pass stock through (#2532, 3046). Also, here is a link to a myford chuck that will pass stock (2nd & 5th pictures):
http://www.rdgtools.co.uk/acatalog/ER32 ... STEMS.html

I've used the er-32 style that your link refers to, but the part actually sticks out as far or farther than in a 3 or 4-jaw chuck. Hard to get accurate run-out, maximize rigidity and minimize chatter!

It's on my list to buy/build a er-32 chuck like the LMS models. The nut is pretty difficult, so I would just use the er-32 nut I have. Although if it's on the mill, that is hard, so I may have to buy another one!

Andrew

Yup, I love flat bottomed drills for this kind of job. I use them all the time for making recessed holes for SHCS bolts. Much nicer looking to have the head recessed even if it is only half way. Although, there are a couple that are recessed 1" deep because I couldn't find a long enough bolt! I only have flattened drill bits for the sizes I need, as I need them, but you are right Harold - it is very easy to do.

I only have a couple, so don't have them in a seperate drill index. Was originally looking at a drill bit organizer - steel case, steel drawers, pre-labelled - nice. Guess what? So was the price - $250.00. Yes that decimal is in the right spot. No drill bits, just the case. Said screw it, went to the hardware store. Bought a multi-drawer cabinet for holding small parts (5 rows of 5 small drawers and 2 rows of 4 large drawers) and made my own labels. I think it cost me $30.00 Holds 1/16" - 1/2" by 1/64". Around 10-12 3/8" fit in one drawer. I think that is what I have the most of. This way, there isn't part drill bit sets with the common sizes missing (broken) all over the shop!

Andrew

Thanks for the replies. Looks like it's time to regroup a bit on the idea. For now, I have run into some dumb questions on chucks, but I will start another thread.

Bill