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Stevelr
10-29-2003, 05:03 PM
Can our experienced machinists help me with another question?

Here's the problem. I need to face a piece of steel (4x3x.375) by attaching it to a faceplate. But I can't drill holes in the work and attach it by screws through to the faceplate. The entire work must be faced, so I can't use clamping (T type) bolts that hook over the edge of the work and hold it in place.

A friend of mine offered one solution.
He said that while in the Navy his unit had come up against a similar problem and solved it in the following way. The work was placed in the approximate center of the faceplate and then bolts were put on each of the four sides (up against the edge of the work). The bolt head was pressed against the work on all four sides, in effect, wedging the work into place. The nuts were tightened on the faceplate from behind. Because the bolt head was lower (less than) the thickness of the work, the heads did not get in the way of the facing operation and the entire piece could be faced.
"But how did they make sure that the bolt heads were firm up against the work?" I asked. "Weren't they worried the work would shift or move?"
"They used a large C-clamp against the bolt heads on opposite sides of the work to press the heads securely against the work edge," he replied. " Then they tightened the nuts behind the faceplate. There wasn't that much to worry about. The bolts prevented the work from moving laterally across the faceplate. Because the facing tool pressed inward (toward the spindle) the cutting force was directed against the faceplate."

So my questions to you...
Is it possible to mount a piece of work this way? Is it safe?
Is there a better (different) way to mount work on a faceplate and face the entire surface without drilling mounting holes in it?

Thanks much for your help.
Steve

SGW
10-29-2003, 05:09 PM
Ummmm.....

I'd be inclined to bolt a good clean, flat, piece of aluminum to the faceplate, put double-sided tape on it, and stick the work to the aluminum plate. With clean surfaces, double-sided tape will hold a surprising amount...but don't rely just on that.

Also drill/tap the aluminum plate and fabricate some side clamps on all four sides to keep the work from shifting...sort of like your idea of the bolts, but I think I'd be a little more formal about it. The work is pretty thin relative to its other dimensions, so it won't have any tendancy to tip. With the tape, you ought to be fine.

Then turn in slow backgear. Relatively light cuts, of course.....

[This message has been edited by SGW (edited 10-29-2003).]

Evan
10-29-2003, 05:09 PM
Is this a special piece to be done? Can you not make a piece oversize and bolt it conventionally and then cut to size afterward?

John Stevenson
10-29-2003, 05:43 PM
Steve,
I have had good results by liberally coating the faceplate with white woodworking PVA glue, then stick a sheet of decent drawing paper to it, coat the top side with PVA again and clamp your piece to it and allow to dry.
As it's square it would help to have a couple of bolts at the cormers to act as driving dogs and stop the interupted cut from ripping it off.
Obviously light cuts need to be taken.
I have used this method to machine stainless disks down to 10 thou in the recess on some parts.

To remove from the faceplate just run under very hot water and the glue will let go.

John S.

darryl
10-29-2003, 06:49 PM
One option I have used is to cross drill and tap the bolt heads, which are then bolted to the faceplate in the appropriate positions. Using setscrews will allow you to tighten against the work, and gives some small room to shift the workpiece around. The setscrews can be used as is, with a small concave to give some grip, or ground to a point, or to a flat. The flat will leave less mark on the workpiece, but could allow slippage.
Press the piece up against the faceplate, tighten the setscrews, and face.

BillH
10-29-2003, 07:01 PM
How about rigging a Magnetic Clamp to the face plate?

Stevelr
10-29-2003, 09:00 PM
Thanks for the many responses posted so far.
Here's a little more info.

-The work piece is already at size and so there is no excess where I could drill holts and attach it that way.

-We only need to face about .010 from it.

-Mr. Stevenson. I'm very intrigued by your idea with the glue. I assume that the faceplate must be very clean (of oil etc.) for the glue to adhere properly. Have you tried other glues? I'm thinking of contact cement which I know is sometimes used to bond certain metals in the aircraft industry.

Again thanks for all your comments and help

jdr86
10-29-2003, 09:49 PM
If you mill the bolt heads at an angle they will be drawn into the workpiece as you tighten them.....sort of like the bench dogs on a woodworking bench.

charlie coghill
10-29-2003, 10:02 PM
Does both sides need to be faced?
Could a piece of pipe be tack welded to the back side and latter be ground off?
I am glad you asked this question as I have a project comming up quite simmilar to yours but the metal will be about 1.250" thick.
Good luck
Charlie

Oso
10-29-2003, 10:11 PM
Did something similar by using 4 jaw chuck.

Put in chuck, with parallels under to let it stand just past the ends of the jaws. Tightened it up, and ran slow and easy with a sharp cutter. If it had shifted, the cut would have told me in time to stop it.

PS take out the parallels before starting machine!

These days, I would just slap it on the shaper table, using toe dogs and a stop to hold down, and plane off whatever is required.

Another approach if you have a milling attachment is to fly cut the surface while holding the part in the milling attachment. Flycutter goes in chuck, end mill adapter, or collet. Its a pain to set up, but it works.

[This message has been edited by Oso (edited 10-29-2003).]

Al Messer
10-29-2003, 10:43 PM
I'm with Osso: use a 4 jaw chuck as he has described, unless you have access to one of those wonderful litle obselete machines called a "Shaper"!!

wierdscience
10-29-2003, 10:46 PM
Superglue and solvent to release.

CCWKen
10-29-2003, 11:25 PM
I have a face plate with 4 jaws but you can make "jaws" for your face plate. I wouldn't use the "wedge" method--too risky. They can be made from square stock.

Drill and tap two holes in the block. One will be perpendicular to the other. Bolt the block down to the face plate with one and run a bolt through the other. You could even put a step in the blocks if necessary.

I guess you don't have a mill?

SJorgensen
10-30-2003, 12:00 AM
I would use the doublestick tape and clamps to secure the work. Also a couple of stop blocks the direction of rotation. Do the face from the center out until near the clamps. Then remove the clamps and bring the tailstock up to help keep clamping pressure on the work. Very light cuts and stop blocks keep the work from twisting off the tape.
Makes me appreciate my mill, but I'm also learning about work holding and I don't know all the tricks yet. Please let us know what you try and how it works out.

Thanks,

Spence

Joel
10-30-2003, 12:38 AM
I would use the double sided (carpet) tape route. For anyone who doesn’t know, when using tape or contact cement, hammer the part down to (sometimes dramatically) increase the bond. Instead of making custom bolts, I would simply drill a couple of holes in some 1/4" or 5/16” bar, and bolt that up tight to the sides. Put the bolts well beyond the part so clearance isn’t a problem. I would probably stick it right to the faceplate. As said, slow feed/speed, small nose radius, and easy on the lead angle. Shouldn’t be a problem, just a few minutes to set up.
Now that I think about it, how about a “V” notch on the 2 pieces of bar. Put them on opposite corners, that would positively locate the part.

SteveC
10-30-2003, 12:38 AM
Maybe I'm missing something here..... just chuck it in a vise and mill it.

John Stevenson
10-30-2003, 04:31 AM
I missed the stated thickness at 3/8" so my reply although still valid would have been a bit OTT when a 4 jaw or even a vise on the mill would do exactly the same job.
Funnyly enough I have a job in at the moment that requres the glue trick.
I have about 12 shims of various thickness fron about 5 thou to 30 off a racing motorcycle to bore out to accept a larger cylinder barrel. What I shall do is cut 12 pieces of cartridge paper to the outside shape and starting with the thinner pieces glue a stack up with the two thickest ones on the outside so I have a sandwich.
Put under the press to allow to set and then with the last sheet glue this on the faceplate.
Once set this will allow me to bore about 5mm from the inside bore of these all at one setting without distorsion.
Using PVA allows you to release it easily just using very hot water as it disolves the paper and then allows you to clean the residue from the surface.

John S.

chipeater
10-30-2003, 08:50 AM
Do you have access to a surface grinder with a mag chuck? Granted, it would take a bunch of passes, but it still might be quicker and easier than the alternatives.

Steve

debequem
10-30-2003, 09:10 AM
Hmm, seems to me that I remember seeing some special bolts for a mill's T slot that are asymetrical. That is, as you tighten the head the "bolt" head the head moves in toward the work. It is designed to pinch the work from multiple sides.

I have seen variations of these that work not with asymetric bolts, but a form of a thick rectangular washer that has a slight taper to its outer face. When clamped down they also pinch the work.

I think these clamps are designed to do exactly what you want to do.

Crashtest
10-30-2003, 11:34 AM
Try toe clamps or mightybites. As you tighten them down they force against the side of the work. Remember, small chips and lower than usual rpm.

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