Hey Gerry

Ok, so I'm not Gerry.

I have a round column mill/drill similiar to the HF link you posted recently. So far I haven't had to move the head and re-center for any my operations. The only time I have to be careful is when I drill and tap. I put the tap guide in the chuck and then adjust the head up/down until I can put the tap holder into the guide and the tap is just over where the hole would be. With 5" of travel that is long enough for the drill to reach and be able to drill the hole. The older Bridgeports with 4" of travel would probablyrequire you to move the table up.

So the round column isn't too much of problem as long as you plan in advance. Given that I'd probably prefer to be able to move the table up/down anyway.

Wayne D.

========== You may want to consider using screw machine length drills. These are much shorter than the standard jobber length drills and also "stiffer." You won't need a complete set, just the tap drill sizes you use. I like the 135 degree split points for everything. Black oxide or bright finish seems to work about the same for me. Cobalt and carbide are brittle and will almost always break or chip before they wear. While these are great for very hard materials, high volume production and using in a very rigid machine, most likely these are not the best choice for the typical home/hobby shop.

see

?PMSECT=0000000623Most other mill supply stores will also carry these.

Unka' George [George McDuffee] ............................... On Theory: Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.

G. C. Lichtenberg (1742-99), German physicist, philosopher. Aphorisms "Notebook J," aph. 77 (written 1765-99; tr. by R. J. Hollingdale, 1990).

OK , I can see why a longer drill , with more flex , and a longer "lever" can be a problem . I also have reasons (for the present) I'd rather not have the size and weight of a full size machine, mostly a weight issue . Whatever I buy will be a companion to a 1951 Wards/Logan 10 X 31 . I'm just afraid the mini mills won't have the rigidity to do what I want to do , which is make motorcycle small parts out of stainless . I've already had issues trying to run a form tool (1/8"w X 1/16" t half round) in some 304 on my lathe . Bad chatter , rough finish , because my toolpost isn't rigid enough (money can fix that - so can having a mill ) . In fairness , there are better machining stainless steels , 303 has been recommended . Even so , I'm hesitant to spend the money on a machine that may not be capable of doing the task I got it for . On the alignment issue , one solution that was suggested was a laser/mirror combo with an index plate on the machine . The mirror mounts on the wall , reflects the laser back to the plate on the machine . Effectively doubles the base leg and therefor doubles the sensitivity . I'd have to do some math to get the actual ratios , but I would suspect that a thousandth plus or minus should be do-able , with care .

Hi George, I should have explained better. The tap guide, tap wrench, and tap provi= de the longest tool pieces in the operation. So with the quill up, there =

should be just enough room to put them in and still have the tap clear the part. You need the jobber length drill and 5" of quill travel in order to reach the part to drill it. Wayne D.

============ Actually what you want are called spotting not centering drills. Center drills do exactly that, drill holes for live/dead centers. Generally these are short, but the manufacturers have begun to introduce longer ones.

see

?PMK0NO=785203most mill supply stores should have a verity in stock.

The reason I like the split point drills is the reduced end thrust. Rig a magnetic base indicator to measure column deflection and drill a hole with the normal 118 point and then one with a 135 split point.

Is there any reason that you simply don't hold the tap in the drill chuck? I have seen several plans for a "yoke" that fits over the chuck with a pin that goes in the holes that the tightening key normally fits for leverage. You won't need to tap more than the first few threads as the tap to bore/surface is "fixed" at that point so you can release the chuck, retract the quill, move the part/tap out where you can get to it and complete the operation with a normal tap wrench.

How big a tap are you using?

Unka' George [George McDuffee] ............................... On Theory: Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.

G. C. Lichtenberg (1742-99), German physicist, philosopher. Aphorisms "Notebook J," aph. 77 (written 1765-99; tr. by R. J. Hollingdale, 1990).

He wants spotting drills, not split points.

Gunner

"Deep in her heart, every moslem woman yearns to show us her t*ts" John Griffin

F. George sez:

"> Actually what you want are called spotting not centering drills.

Sorry if I wasn't clear. I was echoing your idea of using screw machine drills and starting them with center drills.

Bob Swinney

most mill supply stores should have a verity in stock.

Gunner sez:

"> He wants spotting drills, not split points."

Precisely. There is no good reason for a person with machine tools to use split points. All accurately located holes are done so with center drills. There is no point in following a center-drilled pip with a split point.

Bob Swinney

Aside from the fact that they cut better?

Split point is a vast improvement over conventional grinds for twist drills. The web of the standard twist drill, where it would be split, doesn't cut material, it displaces it, where it's cut by the lip. It doesn't cut because of the huge amount of negative rake created by the included angle of the drill. When the point is split, what was negative rake is replaced by a cutting edge with anywhere from 0 to a few degrees positive rake. If you understand cutter geometry, you can easily see that if you'll examine a split point drill. The grind is not a relief, it forms a new cutting edge.

There is a negative side to split point drills. They are somewhat more fragile due to the extra grind. You have to balance the easier drilling against on often shorter lifespan.

One other advantage to split points is that you can drill holes with your mill without the use of a spotting or center drill, depending on circumstances at hand. They are much less prone to skating----especially if one tarries ever so slightly when first touching the drill to the work. Care must be exercised when drilling stainless, it goes without saying. I'm not suggesting they be used in that fashion, but if you recall, short split point drills are referenced as screw machine drills. They were, indeed, used without a center drill when starting holes when running old world automatics (screw machines).

Harold

When split point drills are ground correctly, they're as close to the perfect drill as one can attain. Somewhat similar to the difference between a center-cutting endmill and a non center-cutting one when plunging (the normal operation for a drill). They begin to cut as soon as contact is made, unlike the web of common drills, as Harold points out. The common drill requires pressure to make the web displace the metal surface, before it begins to cut. The split points continue to cut for the depth of the hole (except for when a pilot hole is utilized, obviously).

Any common twist drill can be reground to a split point type. One doesn't need a wheel with a sharp edge to ease into the web area, although this approach seems to be a common belief. Grinding the back side of the web first, will allow the split point to be properly ground when the cutting faces are properly ground as a second operation.

The original common grind should just be ignored when grinding to form split points. Using a broken drill with no visible signs of the original grind can be helpful to grasp the concept of performing the back grinding first.

WB metalworking projects

I have not been able to find a dovetail cutter other then 45 or 60. I could use about 20 or 30 in HSS this is for brass 3/4" for the bottom of the cutter. I have been using 60 on my dovetails for my infill's but it is hard to get the metal peened into the corners.

I also have grizzly's basic swivel milling vise the 6" one but it has some issues the sides of the jaws and tops are not flat or parallel to the side jaws so it makes setup harder. I have had no luck milling them without chipping endmills up. also there is a bit less then a 1/2" gap on the bottom of the vise under the non moving jaw. so if course parallels don't sit well there. but I do like the 2 1/4" high jaws since I put a lot of tall thins in there and plane blades and such to mill the edges. I could use as tall of a vise but one made better. 5" would be fine too.

For the dovetail cutters I can offer no advice - however: My general rule of thunb when it comes to a milling machine vice in the 6 inch range is "If the price wasn't in the four figure range it will be an inaccurate PITA". As you seen to be doing repeat setups it would be far better to rig clamping directly on the table. A collection of inexpensive 123 blocks and some thought will give you the necessary *repeatable* accuracy. Perhaps a sub-table designed for each operation would be cost effective. Hope this helps.

================ You may want to consider a shaper. You can get any angle you want, the tools are HSS lathe blanks @2-3$ each, and you can resharpen as desired. By changing tools to one with a point you can get the corners of the dovetail "sharp."

Unk'a George (George McDuffee ===================================

A man may be a tough, concentrated, successful money-maker and never contribute to his country anything more than a horrible example.

A manager may be tough and practical, squeezing out, while the going is good, the last ounce of profit and dividend, and may leave behind him an exhausted industry and a legacy of industrial hatred.

A tough manager may never look outside his own factory walls or be conscious of his partnership in a wider world.

I often wonder what strange cud such men sit chewing when their working days are over, and the accumulating riches of the mind have eluded them.

Robert Menzies (1894-1978), Australian Liberal politician, prime minister.

Make your own holder for a carbide insert.

MSC will quote specially ground tools if you send them a drawing. I have had them grind several special taps for me. When they do that all the thread data is etched on the tap shank. For special ground drills and endmills I use a sort of local tool and cutter shop: Application Specialties. I use them because they can turn around cutters fast and they have reasonable prices. I'm sure they also would quote a cutter if provided with a sketch with numbers no matter where you are. They are about 80 miles from me so everything is done with faxes and UPS. ERS

I don't need that accurate I only have a mill drill hate for the vise to be far better then the rest of the machine (G)

I mostly a few things of the same at once. so I make setups as fast as possible. if I could I would have a mill for every job I do often so I don't have to screw around with setups.