Table clamps

Table clamps

Webwolf
Webwolf

April 30th, 2012, 11:17 pm #1

So, while my dad and uncle are wrestling with straightening out some dented sliding cover plates on our #2 CNC mill, (Long story.) I'm trying to find some clamps, preferably low-profile ones that don't stick out overly much, so we don't run into this problem again.

Any suggestions?
Quote
Share

Maker of Toys
Maker of Toys

May 1st, 2012, 1:31 am #2

There's lots of ways to clamp/workhold/align/attach. . . but until we know more, we're not going to have much useful advice.

(magnets. . . vacuum. . . overcenter. . . camlock. . .adhesive. . . low melt alloy. . .wedges. . . featherboards. . . sacrificial masks. . . change the part geometry. . .tape. . .collets. . . change the order of operations. . .cast it in wax/resin and melt/burn it off when done. . .)

(obviously, I got LOTS of suggestions!)
Quote
Share

Doc Nickel
Doc Nickel

May 1st, 2012, 1:50 am #3

So, while my dad and uncle are wrestling with straightening out some dented sliding cover plates on our #2 CNC mill, (Long story.) I'm trying to find some clamps, preferably low-profile ones that don't stick out overly much, so we don't run into this problem again.

Any suggestions?
We need a little more information on the conditions and the setup.

Generally speaking, yes, there's dozens of different ways to hold parts down. With a regular hold-down kit, there's "gooseneck" clamps that keep the nut and stud somewhat below the top of the clamp, and for even lower, there's "edge-holding" clamps that bolt directly to the table and push to the side to clamp.

Then there's a huge range of Mitee-Bite clamps, the most common style of which is shown in use here.

Here's a homemade version of the same thing, here's another style of toe clamp, here's a Mitee type with square, serrated faces, a third style of toe clamp, and a fourth, what are called Uniforce clamps, and here's a fixture for holding parts with a round hole.

Lots of different options, but as always, it depends on the part, the setup, the cutting forces, the ease of setup desired, speed of part swapping, etc, etc.

Doc.
Quote
Share

Webwolf
Webwolf

May 2nd, 2012, 5:59 am #4

So, while my dad and uncle are wrestling with straightening out some dented sliding cover plates on our #2 CNC mill, (Long story.) I'm trying to find some clamps, preferably low-profile ones that don't stick out overly much, so we don't run into this problem again.

Any suggestions?
Okay, so, because we tend to run a lot of large parts, i.e., larger than 12 X 12, and therefore too big for the vises, what we've done with one of our mills is to take a 40 X 20 piece of aluminum and secured to the subplate, and then drill our 1/4-20 holes into it for clamping parts to the aluminum with toe clamps.

The problem is, is that this latest part we accepted is 18.95 X 39.00. There's no room for us to clamp by conventional means. So, in the interests of not crashing C-clamps or Kant-Twists that are sticking off the table perpendicular to the edge of the part and denting into the sliding metal covers that cover the wires leading to the headstock as we mill the outside profile of the part, (necessitating that we delay running the part yesterday, until we could get hose metal covers straightened out,) I need alternatives.
Quote
Share

MephitMark
MephitMark

May 2nd, 2012, 3:09 pm #5

So, while my dad and uncle are wrestling with straightening out some dented sliding cover plates on our #2 CNC mill, (Long story.) I'm trying to find some clamps, preferably low-profile ones that don't stick out overly much, so we don't run into this problem again.

Any suggestions?
If you could post a picture (that doesn't violate any secrets), that would help provide the best idea of you situation.
Quote
Share

Maker of Toys
Maker of Toys

May 2nd, 2012, 4:01 pm #6

Okay, so, because we tend to run a lot of large parts, i.e., larger than 12 X 12, and therefore too big for the vises, what we've done with one of our mills is to take a 40 X 20 piece of aluminum and secured to the subplate, and then drill our 1/4-20 holes into it for clamping parts to the aluminum with toe clamps.

The problem is, is that this latest part we accepted is 18.95 X 39.00. There's no room for us to clamp by conventional means. So, in the interests of not crashing C-clamps or Kant-Twists that are sticking off the table perpendicular to the edge of the part and denting into the sliding metal covers that cover the wires leading to the headstock as we mill the outside profile of the part, (necessitating that we delay running the part yesterday, until we could get hose metal covers straightened out,) I need alternatives.
without seeing at least the profile of the part, here are some ideas.

#include (std_disclaimer.h), YMMV, etc, etc.


Option 1: put a pocket in your Table interface plate (with, say, .375 width by .250 (or whatever) high walls on the 'covers' side(s), and then use that to clamp against 'vice' style from the operator' side(s) with whatever is handy and will fit. A set of smallish diameter set-screws bearing on a 'jaw' plate has worked for me in the past-- the trick is to get ENOUGH screws to clamp evenly. Obviously, only good against relatively light cutting forces, and the 'table' plate/pocket has to be spotless and burr-free each time you mount a part, but hey. . . .

Option 2: I have also done (for thin material or setups that won't take a conventional 'vice' type clamping arrangement due to parallelism or warp concerns) a sort of 'L" bracket out of aluminum angle or whatever is handy, held with a profusion of 10-24 or even 8-32 screws through the top of the 'L', but back a bit from the lip of the angle that contacts the part. This works best if you have a registration feature in your 40"x20" plate for the part. The angle has to contact both the part and the 'table' surface, with the 'vertical' leg just a little taller (say 0.020" to 0.050") than the part 'blank'. This option works well for low profile parts that either are already finished on the edges, or can have the edges finished in a separate step (see option 4), but I wouldn't trust it for anything much thicker than about 1.5". It does give the ability to hold parts that get within .25" or so of the column, however.

Option 3, Assuming that the part has a large, flat, solid base that you will not be machining through, is a vacuum chuck. Mcmaster-carr sells compressed-air powered venturi-style vacuum pumps that can cope with the occasional bit of coolant, etc, as long as you keep the big chips out of them. . . . Not the best at resisting heavy side forces, but you can get the part within 0.0001" (or whatever makes you comfortable) of the column.

Option 4: if you WILL be machining openings through the whole part: cut some of the openings with the part clamped as before, but put a pause in the program for the operator to insert some hold-downs through the new openings and remove the Kant-Twist/G-clamps before doing the portion of the part that the offending clamps interfere with.
Quote
Share

Webwolf
Webwolf

May 2nd, 2012, 10:52 pm #7

If you could post a picture (that doesn't violate any secrets), that would help provide the best idea of you situation.
I mean, I WISH I could tell you guys that what I am working on is being done for the ahem, "Navy" and may or may not wind up going into something that may or may not become armor plated and may or may not be remote-controlled, and may or may not house a machine gun of some sort.

Of course, if wishes were money, I'd be in Tahiti!
Quote
Share