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magicniner
22-04-2016, 03:22 PM
Has anyone else here discovered Kopal milling clamps?
My local tool shop had some second hand ones in and I bought a pair, stripped & cleaned them and tried them out.
Then I bought another pair, then a larger pair for clamping tool plates on my fly press, I've started calling them Frosties 'cos They're Gr-r-reat!

- Nick

sinnsvak
23-04-2016, 09:22 PM
No idea where I would get em around here, but they look nice. They clamp good enough for metal milling?

cropwell
23-04-2016, 09:31 PM
Has anyone else here discovered Kopal milling clamps?
My local tool shop had some second hand ones in and I bought a pair, stripped & cleaned them and tried them out.
Then I bought another pair, then a larger pair for clamping tool plates on my fly press, I've started calling them Frosties 'cos They're Gr-r-reat!

- Nick
You must be rich, Nick. I have looked at the price of these things !

magicniner
23-04-2016, 11:06 PM
No idea where I would get em around here, but they look nice. They clamp good enough for metal milling?

Oh yes, you can apply some serious clamping force with relative ease.


You must be rich, Nick. I have looked at the price of these things !

Not really, they were second hand, had sat for many years unsold, and needed a good strip and clean, I got them for a song and I can't sing very loud ;-)

Jay
22-08-2016, 06:06 AM
We used Kopal clamps on a Hmc at work to hold 350x350x25mm plates for machining and they gave great clamping force but I would recommend making some steel bushes that you can knock on the knurled part of the screw to increase the strength of the Allen socket because they are prone to breakage if you over torque the screw so the coller stopes it ripping apart and becoming useless. They will be a pain to get off if you want to service the clamp but it's doable.

magicniner
22-08-2016, 09:53 AM
We used Kopal clamps on a Hmc at work to hold 350x350x25mm plates for machining and they gave great clamping force but I would recommend making some steel bushes that you can knock on the knurled part of the screw to increase the strength of the Allen socket because they are prone to breakage if you over torque the screw so the coller stopes it ripping apart and becoming useless. They will be a pain to get off if you want to service the clamp but it's doable.

I've milled the hold-down bolt hole on two of mine out to a slot to take M10 custom bolts but it's a common misconception that the hold down bolts need high torque, they don't.
Kopal clamp hold down screws should be hand tight and not swung on, they only need to be tight enough to stop the clamp easily moving out of position before any clamping force is applied, the tool provided has the right dimensions to stop the uninformed swinging on the screw and applying excessive torque ;-)
The whole point of the design is that applying the clamp uses the hold down bolt as the pivot point of a lever with the work contact and the back end of the clamp as the pressure points.
If you break the screws you're not understanding the correct usage of the clamps :D

- Nick

Jay
23-08-2016, 03:04 AM
I fully understand how the Kopal clamps work and worked very close with Kopal along with a few work colleagues 19 years ago when we found that although the clamps where good on material with a clean edge they where pretty crap when it came to a flame cut edge or rough edge.
The problem we found was that the foot of the clamp wasn't in full contact with the edge of the plates we where using because they where flame cut so after having a few plates come flying off our HMC (one littereley taking the enclosed doors off the runner and bending the frame) we had talks with Kopal to look in to the problem. After we looked at the job and found what was happening and Kopals rep having seen what was happening the answer we got and only solution was to dog them down as much as possible until all the clamp was in contact with the edge of the plate which worked apart from blowing the heads of the screws out which is where we had to fit collets to the screw head. In all they are pretty good clamps but you have to torque them up more on anything than a good clean edge especially on a HMC.

magicniner
23-08-2016, 10:03 AM
In all they are pretty good clamps but you have to torque them up more on anything than a good clean edge especially on a HMC.

It's common in industry to misuse and abuse equipment that is used outside it's design parameters but to describe that as a fault of the equipment rather than operator error is unfair on the product.
The correct solution to your problem would have been custom feet for the clamp noses which incorporated spherical contact surfaces to allow free alignment of a lower section with 3 distinct high points allowing clean 3 point contact on uneven surfaces, the rep sounds like he had no engineering background or problem solving capabilities beyond "big spanners" and when all you have is a hammer, every problem looks like a nail ;-)

Jay
23-08-2016, 11:18 AM
No body blamed the equipment. What I said was that they where only designed for clamping on a good clean edge or otherwise you would need more force if the edge was slightly out or serrated for instance. The idea of havin clamps made as you describe would not have worked at all and would have offered even less clamping force as flame cut plates can come out with all manner of edge shapes. I hope I'm coming across ok as I sometimes hate this where you try to describe something over the Internet but it's so much easier face to face.
By all accounts as uv said above they are good clamps and I liked them even to the point where I suggested the use of them to a few companies uv worked for but as always cost played a part and if you know Kopal then you know they where not cheap. In fact while I write this I seem to remember I bought a few sets home after my brother did a management buy out of the company and sold the machines off and they where sat in the tooling locker so I grabbed them before someone else did.
I'll have to have a rummage around and see if I can't find them and if I can then I'll stick them on here if their of use to someone as iv packed in due to terminal cancer so they are no use to me and never will be now. Got an old emco compact 5 Cnc gathering dust with loads of stuff and tapes with it to if their still being used by people or is it a case of scrapping because people are not interested in them anymore? ( been out the game a while so no idea what's the in thing these days you see...lol)

magicniner
23-08-2016, 11:34 AM
Got an old emco compact 5 Cnc gathering dust with loads of stuff and tapes with it to if their still being used by people or is it a case of scrapping because people are not interested in them anymore? ( been out the game a while so no idea what's the in thing these days you see...lol)

The EMCO stuff is still cutting chips, most now use MACH3 or LinuxCNC, some use parallel port & break out board, others USB or Ethernet and an external motion controller. Some use the old steppers, some replace them but the base hardware is good and is still worth having,

- Nick

Jay
23-08-2016, 03:39 PM
Cheers that's good to know. Will have to dig it out and freshen it up and take some pictures then bang it on the bay and see what happens. Might pay for a days fishing....lol