X-Y Crosstable Quality?

I'm not a machinest or metal worker.
I seek the opinions of the experts, please.
I want to add a small (4 or 6") cross table
vise to my drill press. I see similar tables
all the way from $40 (Harbor Freight) to over
$100 (Craftsman) and I would imagine there are
some even more expensive versions.
Are the Harbor Freight models junk? Do the
higher priced styles have finer adjustment
resolution? Are some made with magic dust?
Thanks -
L
Reply to
Lumpy
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The black Indian-made ones, IMHO, are not worth the effort to carry them home, even if they were free. Very crude, with tons of slop in them. Harbor Fright used to have one that was a bit more expensive (maybe 120 or 130) that was matte-finish steel, and at least 10:1 more accurate. I don't see it on their website, but maybe they still have them in the stores, or maybe someone else knows where they can be had.
Here's one (new, undoubtedly Chinese) on eBay if you want to go that way, but shipping will cost you a bit: 7533595166
Whatever you get, especially if you want to go cheap, try to go in and look at it before buying. Those black ones are execrable, wretched poop. IMHO.
Best regards, Spehro Pefhany
Reply to
Spehro Pefhany
The main difference between the various models is how smoothly they operate, and how little slop from side to side motion in the ways.
Also, there are variations on how much metal is present in the assembly, thus giving it varying rigidity.
I do feel that I should ask what you are planning to do with this. The reason for asking is that while these are fairly nice for drilling holes in some predefined pattern, by cranking in the locations, they also tempt people to use the drill press as a milling machine. *This* is a disaster waiting to happen for several reasons. I'll put the most important one first:
1) Drill chucks are attached to the spindle or arbor in the drill press by a "self-holding taper" -- usually a Jacobs taper, with possibly a Morse taper socket in the drill press's spindle.
These are great for *drilling*, but anything which applies a side load to the cutting tool is very likely to work the chuck loose from the taper -- and then you have a heavy drill chuck with a very sharp cutter in it, spinning madly and bouncing around the shop -- perhaps hitting (and cutting) you, or chasing you around the shop.
There are some drill press designs which include a threaded retainer to hold the chuck in place. This helps somewhat.
2) A drill press has a lot less metal in the path from the chuck, up through the head, down the column and out to the table to which your X/Y table is bolted, and back up to the workpiece.
This means that it is not nearly as rigid as a milling machine (even a small cheap one), leading to chatter, and poor finish, even if you can keep the chuck from falling off.
3) The quill in a drill press typically has a lot of side to side slop, resulting in yet more problems with rigidity and chatter.
4) Drill chucks are good at gripping drill bits, which have soft shanks and hardened cutting edges.
Milling cutters (end mills), however, are hardened more universally, and even have some problems being gripped in R8 collets (an end-mill holder is better). Trying to hold one in a drill chuck increases the chances that it will walk out of the chuck slowly increasing the depth of cut. (There are drill chucks made to mount in milling machine spindles which have diamond grit in the jaws to grip the hardened shanks of end mills.
5) Most drill chucks are not that good in terms of concentricity, so even if they manage to hold onto the end mill, they will be running it slightly off center, so it will cut an oversized hole, and will typically be cutting only with one flute, leading to faster wear.
There are probably some other reasons to avoid milling on a drill press that others can think of. So -- if you intend to use this for placing patterns of drilled holes -- fine. If you intend to try milling with your drill press -- *please* don't.
Good Luck, DoN.
Reply to
DoN. Nichols
D> I do feel that I should ask what you are planning to do with
Not milling. Drilling .100 inch spaced holes in printed circuit boards. No side load.
Two drill presses. One a conventional Craftsman 1/2" chuck. The other a dremel, 28k rpm through a 0.7mm dental burr. Dremel is for the smaller stuff like component leads. Craftsman is for the larger holes like mounting holes. PC board material is generally laminated glass cloth, 1 oz copper clad.
Thanks DN and SP for the responses.
Lumpy -- In Your Ears for 40 Years
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Reply to
Lumpy
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Great! This is an entirely appropriate application for the X/Y table. Be sure to always feed in the same direction (and if you overshoot, back up far enough so that you take out the slack when you feed forward again).
I've drilled a lot of that. Ideally, you'll want solid carbide drill bits for this. I once drilled about 80 holes in a small board using a brand new #70 HSS drill bit (in a Cameron Precision sensitive drill press), and by the time I was done, the drill bit was so worn that it looked like a needle in shape -- and the holes were lined with fibreglass fur. :-) Once I got some solid carbide bits, the problem went away. (Be careful with them to not allow the workpiece to shift sideways, however -- that will *certainly* break a carbide bit in an instant.
What you might want for the small drilling is a sensitive drill adaptor for the big drill press (so you can still use the X/Y table, and yet can feed gently enough so you won't break drills.
O.K. No examples on eBay at the moment, so I'll try to describe it:
1) 1/8" chuck (probably Albrecht, though I have seen them with Jacobs chucks as well.
2) There is a 1/2" hollow shank to be gripped with the main drill chuck, and a smaller shank sliding inside it -- with a key to keep them rotating together. The smaller one has the small chuck attached.
3) There is a spring to retract the small chuck back to the top.
4) There is a ball bearing assembly surrounding the smaller shank, with a disc of aluminum press fitted to the OD of the ball bearing assembly.
This allows you to use the drill disc to gently feed the drill chuck (and whatever bit it is holding) into the workpiece, instead of having to use the rather excessive leverage that the drill press' feed arms offer. Thus, it is a lot easier to keep from breaking the drill bit.
A sensitive drill press works well for the smaller drill bits (I've used mine down to #80 bits), but usually has trouble reaching to the center of a large PC board.
There are versions of the Cameron Precision which offer such access, but mine does not. I think that it will reach to the center of about a 4" -- maybe 5" board.
Enjoy, DoN.
Reply to
DoN. Nichols
Perhaps visit cnczone.com and have a look at the CNC routers people are building for drilling and milling PCBs.
Pete C.
Reply to
Pete C.
I've drilled many hundreds of boards (tens of thousands of holes). There are two approaches. One is to use a stiff carbide bit (which lasts forever unless/until you break it (assuming manual drilling). Pretty much wherever the drill touches, the hole appears unless it's at the edge of an etch, in which case the drill may skate and may break. This is what the professional CNC equipment uses.
The other approach is to use decent quality steel bits and create the etch artwork with holes left open. The drill flexes to self-center on the pad and you get the hole precisely located to the etch pattern. You still want to run the bits pretty much as fast as you can for small sizes (like 0.04"/1mm and under). You can drill pilot holes with 0.8mm or whatever and open them out with your Craftsman with little effort. You just need a good light and some safety glasses (and to blow away the swarf now and then), no X-Y table required. You can do this with carbide bits too, but the slightest slop in your drill setup or any other sideways force will snap off the bit in your face. It's probably counter-productive to leave the holes open, better to try to center them on the pad by eye. Usually the broken-off drill bit chunk sticks in the PCB material, but you never know..
Fibreglass PCB material like FR4 is pretty abrasive and will dull the bits, but the cheap ones can just be discarded when dull (they are very inexpensive compared to the value of time). A backup material of some kind will improve the finish on the back of the board. Paper-based phenolic is less abrasive, but cracks more easily and tends to be less heat resistant.
You're welcome.
Best regards, Spehro Pefhany
Reply to
Spehro Pefhany
[some excellent stuff about drilling PC boards]
Thanks once again, SP. Valuable info, much appreciated.
Lumpy -- In Your Ears for 40 Years
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Reply to
Lumpy

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