OT: Need workholding recommendations

[Thad]

All of the die shoes that we get in are rough burned/scaled up surfaces. We need to mill the thickness in holding size and keeping it as flat and parallel as possible. Currently this involves clamping the part down, milling around the clamps, flipping the part, repeat steps 1 and 2 (for flatness), moving the clamps and blending the previously clamped areas to the finish milled surface. Some of these plates are 15 ft long and 6 ft wide. This becomes a very time consuming PITA. Since we can't convince management to get the plates Blanchard ground, we've decided to look into hold down-type tooling that would allow us to machine the entire top of the part without having to cut around clamps and then later blend those areas in. I've seen various clamps that mount to the table that have a "jaw" that pushes down and away, to hold the part tight to the table. Has anyone ever used these, or similar clamps, and had good luck with them? Are they very strong? Can you take "normal" cuts when using them? Any advice would be appreciated.

 

Thad

[JS]

I have used these often and love them. If you put them around the perimeter of say a 1" thick plate you can machine the whole top surface with no problem. When you tighten them up the face of the clamp moves at a 45 degree angle putting pressure on the part inward and down at the same time. Give them a try.

 

Joe

[mayday]

Hey Thad,

sounds like you got some big parts. we do this all the time. We have setup blocks with keys in them for the table. around the side of the blocks are 1/2-13 tapes holes. bolt down the blocks to support your part and bolt on fence blocks and pusher blocks to the setup blocks. use set screws to hold the part against the fence blocks and start cutting. no tie downs. the part cant move cause you got it blocked in all 4 ways. this works well for heavy plates. we got a 60" x 120" mazak that we do this all the time for plate work

[Dan Schnars]

Mitee-Bite has a nice selection of clamps for what you are trying to do... I've had pretty good luck with their Series-9 clamps and their Pit-Bull clamps. Their web site actually has cad models of some of their clamps you can down-load and incorporate into your model. They give specs on clamping force so you can figure how many clamps / how agressive you can get with your cuts.

[robk]

Thad,

 

In here we use hydraulic clamping made by Vektek. The only grab the bottom .250 of the part or so, and also pull it in. Check out www.carrlane.com. They have a bunch of different clamping systems. Also www.vektek.com. Good luck.

 

Rob

 

[ 08-22-2003, 09:22 AM: Message edited by: robk ]

[Müřlıń®]

quote:

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Some of these plates are 15 ft long and 6 ft wide.

---

 

I would be careful with them if the sides of the plates are torched.

 

What I would use is boltable lathe jaws instead of the down angle table clamps.

 

They are rather pricy though.....

 

 

Murlin

[Thad]

quote:

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I would be careful with them if the sides of the plates are torched.

---

Murlin,

 

The sides are torched, but it's a pretty smooth finish. Just a tad worse than a nice clean saw cut. The straightness of those torched edges can vary.

 

Thad

[Thad]

quote:

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sounds like you got some big parts.

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Mayday,

 

That's about as big as they get at our shop. Some are only 4ft X 2.5 ft, but you've still got the same problem of moving clamps.

 

Thad

[Müřlıń®]

Well you might get those clamps to work.

 

You might try putting some emmory between the clamp and the plate for added protection against movement.

 

I use emmory under my dies when I clamp them down to prevent them from moving around since I only use 2 clamps on the handling holes.

 

Can you take a take a mag drill and drill some handling holes on the sides?

 

 

Murlin

[Thad]

Murlin,

 

We use the handling holes when we can, but it doesn't always work out.

 

Thad

[heeler]

We've had great success with the Mitee Bites. Never had parts that big, our mill are only 40" X 20". Used them on really thick stuff though.

 

HTH

 

Glenn

[Surface]

I don't know how thick die shoes are, but I do know that clamping a part 6 feet x 14 feet, by the perimeter, it is dam near imposible to get it flat. I have done a lot of machining on big stuff. My suggestion is to hold side 1 with bondo. Use Car-wax on the machine's table to prevent the bondo from sticking too much.

Bondo is cheap and it will suport and hold the plate in it's most natural state without stressing the plate with clamps. Once set, you can add a couple clamps to insure the part won't move. Bondo will machine easily off side 2 and prevents chatter.

Side 2 can be clamped down. Life is so much easier when you know you have one flat side

[mayday]

quote:

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it is dam near imposible to get it flat.

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3 solid points and a screw jack is the way to go, big heavy plates tend to sag on there own weight anyway. set on 3 points and make up the diference on the 4th point with a jack to take out any rocking you get from the twist in the plate, rough the first side. release it in case it warped, reclamp and take a finish cut

 

[ 08-22-2003, 12:01 PM: Message edited by: May^Day ]

[Müřlıń®]

Surface what a neat trick

 

I use to use double sided tape on the surface grinder to take the warp out of a part.

 

That would work as long as your workpiece remained perfectly cool while machining on it.

 

 

Murlin

[Thad]

quote:

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I don't know how thick die shoes are

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Typically 3-5 inches.

 

Thad

[Andy]

You could weld some tabs around the edges that line up with the t slots and bolt down, flip, and later saw them off.

[Hardmill]

Ever use magnets?

I got a source for milling mags if your interested.

 

 

PEACE

[Thad]

Hardmill,

 

Initially, this doesn't sound feasible, but I'd like to hear more about this. How are the magnets used?

 

Thad

[Thad]

Andy,

 

Our smallest die shoe would probably crush our biggest saw.

 

Thad

[mayday]

come up with anything yet?

I can send some pics of our 60x120 monday if you like, to show you how we do it. we are running some die plates right now

[Thad]

quote:

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come up with anything yet?

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One of my colleagues is checking into the ideas you guys have provided. I'd be interested in seeing any pics that you have.

 

The (clamp) type I mentioned in my original post seems to be the logical choice, although we're looking at all of our options.

 

Thad

[Hardmill]

sorry bout the delay

check here http://www.tecnomagnete.it/index.html

 

 

PEACE

[Thad]

Ohhh, those magnets. Not a bad idea. Maybe if I show them what these magnets cost, having them blanchard ground won't sound like such a bad idea. Seriously, it's worth looking into. Thanks.

 

This is impressive.

 

Edited to say that the link didn't work like I wanted it to. The pic of the round stock on the magnet is impressive.

Thad

 

[ 08-22-2003, 09:38 PM: Message edited by: Thad ]

[Hardmill]

Used them for the last 3yrs. If I could i'd

buy one to hold my boys down.

they really are a great tool.

 

E-mail me if you want to talk about them.

 

PEACE

[Thad]

Hardmill,

 

Your email is not available. Send me an email and I'll reply with some quesions. I'll get back to you this weekend sometime. I've got a full day scheduled for tommorow. Thanks.

 

Thad