Mitee Bite Pitbull Clamps?

Discussion:

(too old to reply)

LillardMfg

2003-11-19 04:09:55 UTC

I'm currently machining parts that start as a 22"x5"x.750" bar of 6061-T6.
Right now my first op fixturing is pretty lame. It's a Kurt D688 vice with
2"x2"x22" jaws made out of 6061-T6. I have .250 of grip on the parts, so
there's a decent amount of bite, but I'm still scared to really start pushing
it on the roughing. I'm getting about 35% spindle load on a 40HP spindle. The
part starts at close to 8 pounds, and ends up less than 2 pounds when it leaves
the first op fixture, so there's quite a bit of material removed. The customer
is projecting a drastic increase in production, so I want to work on a new
first op fixture to make 4 or more parts per load. I'm looking for not only a
cost effective method of holding multiple parts, but I'm also looking for more
clamping force so I can utilize all 40HP.

I've been looking at the Mitee Bite Knife Edge Pitbull clamps, the 3/8-16 size.
I've asked around quite a bit, but can't seem to get any definite feedback on
the clamping force. The brochure claims 6000lbs of clamping force, but this
means nothing to me. Have any of you ever worked with these little monsters? I
just received 16 of them today that I'm using on a different fixture, but they
are just to hold down some smaller parts with practically no cutting force.

If you haven't used the Mitee Bite clamp, I'd still like to hear any other
suggestions. Keep in mind that the perimeter of the part is only cut down to
Z-.500 in the first op, so there's a solid .250 of clamping area around the
entire outside.

Thanks,
Joe Lillard

Stanley Dornfeld

2003-11-19 04:57:43 UTC

Permalink

Holding pressure is kind of a strange thing and sometimes misleading.

If you have an air vise which has a cylinder closing the movable jaw; and
the pressure is one hundred lbs. When you are machining along and say a
chatter starts it can beat against the movable jaw and the vibration can
move the jaw by compressing the air. (A sponge)

However if you have a solid steel vise which has the movable jaw locked in
place by a 1" diameter screw, the chatter will be beating against a solid
system. So the part doesn't need to be crushed with 10,000 lbs to be held.

Anyhow if you are going to use the clamps you bought, and you build a
fixture which is solid metal and pocket just the area where the clamp sits
so you don't weaken the structure; then I think you should be ok. (What a
sentence. Sheesh!)

I use Uniforce clamps from Mitee-Bite and they hold very well because when
they clamp there is solid metal contact (no sponge) through the holding
system.

I don't know if the Uniforce would work in your situation because of the .25
holding height.

It would be cool if they could because you hold two parts at once. *Smile

Regards,

Stan-

Post by LillardMfg
I'm currently machining parts that start as a 22"x5"x.750" bar of 6061-T6.
Right now my first op fixturing is pretty lame. It's a Kurt D688 vice with
2"x2"x22" jaws made out of 6061-T6. I have .250 of grip on the parts, so
there's a decent amount of bite, but I'm still scared to really start pushing
it on the roughing. I'm getting about 35% spindle load on a 40HP spindle. The
part starts at close to 8 pounds, and ends up less than 2 pounds when it leaves
the first op fixture, so there's quite a bit of material removed. The customer
is projecting a drastic increase in production, so I want to work on a new
first op fixture to make 4 or more parts per load. I'm looking for not only a
cost effective method of holding multiple parts, but I'm also looking for more
clamping force so I can utilize all 40HP.
I've been looking at the Mitee Bite Knife Edge Pitbull clamps, the 3/8-16 size.
I've asked around quite a bit, but can't seem to get any definite feedback on
the clamping force. The brochure claims 6000lbs of clamping force, but this
means nothing to me. Have any of you ever worked with these little monsters? I
just received 16 of them today that I'm using on a different fixture, but they
are just to hold down some smaller parts with practically no cutting force.
If you haven't used the Mitee Bite clamp, I'd still like to hear any other
suggestions. Keep in mind that the perimeter of the part is only cut down to
Z-.500 in the first op, so there's a solid .250 of clamping area around the
entire outside.
Thanks,
Joe Lillard

michael

2003-11-19 05:07:12 UTC

Permalink

I would have 2 vises instead of just the 1, if I understood correctly. You should
be able to romp through that stuff with .25 clamping stock. Just watch out for a
poor sectional profile of the stock, concave, convex, parallelogram, or trapezoidal
shape. In the past I have found Kaiser material to push the limits of shape
tolerances, and size too. Large variations even in same lot material.

Have not used the knife-edge Mitee Bites, but the standard hex style have worked
well for me. A friend of mine got me started using them and I was impressed with
the job he showed me. He used them to hold some 17-4 cast parts in a fixture that
held around 40 of them. The run was several hundred or more and he only had 3 or 4
parts pull out. This is a guy who really likes to push things too.
I would think for your planned application they will work fine. Make your fixture
beefy. If you have the fixture bolted down, no problem. I did some jobs with
matching fixtures and swapped them in and out of the machine. When you get several
tightened you can make your fixtures bow.

Good luck.

michael

Joe Osborn

2003-11-19 06:55:32 UTC

Permalink

Post by michael
I would have 2 vises instead of just the 1, if I understood correctly. You should
be able to romp through that stuff with .25 clamping stock.

This was my first thought also. Definitely use more than one vise. Should be
plenty beefy to hold the stock down.

Regards,

Joe Osborn

OMW Metalcrafts
"Custom Precision Machining
in all Metals and Plastics"
23 Pamaron Way, Ste. E.
Novato, CA 94949
WWW.OMWMETAL.COM
EMail: ***@AOL.COM

SPI01

2003-11-19 05:24:46 UTC

Permalink

We likewise have a machine with a 40Hp spindle, and I can say for sure that
you will stall your spinle long before you chuck a part from a Kurt 688
vise. However, as the aluminum (even at 2" thick) will bend slightly at
the ends, you will loose gripping force . a good trick to help combat this
problem is to mill an intentional bow of .003-.005" so the ends flex when
the vise is tightened. This will spread the load more evenly over the part
and eliminate the risk of having a part come loose. This is the same as
boring a back taper on long lathe jaws to compensate for the flex.

Dennis

plh

2003-11-19 15:39:40 UTC

Permalink

I have used them, in the 8-32 size. In that case I found that I had to torque
them or risk having them crack around the bottom of the counterbore. The first
set I bought did not have that problem, but then MiteeBite changed to a cast
design, presumably to reduce cost. They do develop considerable pressure, there
will be little reason for you to worry about loosing the part. I was not using
the knife edge, rather the standard edge on some O-1. I'd be careful designing
the fixture for the knife edge lest it sink into the aluminum so much that it
bottoms out. You can call them, they have a good web site:
http://www.miteebite.com/
and have always been helpful. I called complaining about the cracked ones they
sent me a couple of bags gratis, because the instructions didn't mention
anything about torque limits at the time I bought them. I'd check to see if
there are torque limitations on the 3/8-16 size.
Later,
-plh

I keep hitting "Esc", but I'm still here!

2003-11-20 19:25:48 UTC

Permalink

Post by LillardMfg
I've been looking at the Mitee Bite Knife Edge Pitbull clamps, the 3/8-16 size.
I've asked around quite a bit, but can't seem to get any definite feedback on
the clamping force. The brochure claims 6000lbs of clamping force, but this
means nothing to me. Have any of you ever worked with these little monsters? I
just received 16 of them today that I'm using on a different fixture, but they
are just to hold down some smaller parts with practically no cutting force.
If you haven't used the Mitee Bite clamp, I'd still like to hear any other
suggestions. Keep in mind that the perimeter of the part is only cut down to
Z-.500 in the first op, so there's a solid .250 of clamping area around the
entire outside.
Thanks,
Joe Lillard

We are using the knife edge Mitee Bites. It's holding 6061-T6 one
inch square bar.
We have had a few thrown out by cutting forces but they are all due to
operator error
not tightening or bottoming out the clamp. If the stock is undersize,
the clamp can be
turned past center and bottom out.

ff

"PrecisionMachinisT"

2003-11-21 02:39:53 UTC

Permalink

Post by ff

We used them quite a bit for first op workholding on the 777 wing sar
fittings......not the knife edge type, IIRC these had a square shaped clamp
on them.

Worked pretty good, the parts were ~ 3 x 3 ft and maybe 3 inches thick.

--

SVL

Stanley Dornfeld

2003-11-21 16:23:10 UTC

Permalink

Hello SVL..

Would you mind describing the Mitee Bite clamp you are talking about a bit
more? I'm not sure which one you're using.

Thanks...

--
Regards,

Stan-

PrecisionMachinisT

2003-11-21 19:57:19 UTC

Permalink

Post by Stanley Dornfeld
Hello SVL..
Would you mind describing the Mitee Bite clamp you are talking about a bit
more? I'm not sure which one you're using.
Thanks...

A pitcher is worth a thousand words, Stan....I would gladly buy the first
round if ever the occasion should arise....

Loading Image...

We had rails along the bottom and along the left side of the tombstone,
several of these clamps were along the rh side and the top.....

While we had saw cuts causing problems along the solid rails at first, we
eventually modified the rails to accept 10-32 set screws that were ground to
a point and set into the rails at a 15 degree angle.

The parts would be set on the rails and one of the mitee bites snugged on
top and on rh side, then the setscrews were tightened to pierce the
workpiece along the rails..........then the mighteebites were given final
tightening.

These fittings were a thin floor workpiece with a few webs in them, the wing
countour was milled around the periphery---two finish pieces were laminated
together for the final assembly.

The setup I have described above was used for first op only, where the raw
stock was faced off and tooling and holddown holes were put in---the
remaining subsequent processes were by dedicated fixturing.

--
SVL

Gary H. Lucas

2003-11-21 23:43:07 UTC

Permalink

Post by PrecisionMachinisT

Post by Stanley Dornfeld
Hello SVL..
Would you mind describing the Mitee Bite clamp you are talking about a bit
more? I'm not sure which one you're using.
Thanks...

A pitcher is worth a thousand words, Stan....I would gladly buy the first
round if ever the occasion should arise....
http://www.miteebite.com/images/product_pages/multi-fixture_1.jpg
We had rails along the bottom and along the left side of the tombstone,
several of these clamps were along the rh side and the top.....
While we had saw cuts causing problems along the solid rails at first, we
eventually modified the rails to accept 10-32 set screws that were ground to
a point and set into the rails at a 15 degree angle.
The parts would be set on the rails and one of the mitee bites snugged on
top and on rh side, then the setscrews were tightened to pierce the
workpiece along the rails..........then the mighteebites were given final
tightening.
These fittings were a thin floor workpiece with a few webs in them, the wing
countour was milled around the periphery---two finish pieces were laminated
together for the final assembly.
The setup I have described above was used for first op only, where the raw
stock was faced off and tooling and holddown holes were put in---the
remaining subsequent processes were by dedicated fixturing.
--
SVL

Ever tried the Kurt clamps that look a lot like the Mitee Bites? They are
hexagon shaped and split in half with an o-ring holding them together. The
screw is a flat head and the taper on the screw wedges them apart. It also
pulls down hard at the same time. The Mitee Bites use an Eccentric screw.
I think the Kurt's can hold down better. They do however cost quite a bit
more.

Gary H. Lucas

PrecisionMachinisT

2003-11-21 23:50:25 UTC

Permalink

Post by Gary H. Lucas
Ever tried the Kurt clamps that look a lot like the Mitee Bites?

Nope........

But Ive often wondered how well a standard Allen head screw with an offset
machined in the head and with also a thread turned in the head, the same
pitch as the thread lead might do all by itself......

Maybe one of the screw machine guys could make some up, never know--it could
turn into a moneymaker.

--
SVL

Jon Anderson

2003-11-22 03:16:15 UTC

Permalink

Post by Gary H. Lucas
I think the Kurt's can hold down better. They do however cost
quite a bit more.

I have and use both types. One thing I like about the Kurt clamps is you
can clamp two parts with one clamp. But even the small MiteeBite
eccentric clamps have a surprising amount of holding power.

Jon