Tube setting problems

[Kermit]

Hi all

I am trying to tube set a 5mm facetted stone.

I have cut the tube to length, soldered to the ring shank and then have used a 5mm setting burr (brand new from cookies) to make a seat for the stone.

I have used a 4mm setting burr a couple of times before and managed OK.

This time, every time I tried to use the burr it kept cutting in and snatching on the metal (if that makes sense) - I'm using a clarke flex shaft (like a dremel) and I have lubed the burr with a little oil. this happened even when I was trying to do a tiny tiny amount.

I've now wrecked the tube so I'm walking away for today and hope to have another go another day !

Really hope someone can tell me what I'm doing wrong........

Thanks

Jane

[Patstone]

Never done a tube set cab but will try soon. Can't think what could be the trouble with the burr, if its grabbing perhaps oil isn't man enough, I use beeswax on my burrs and my drills, it doesn't seem to make much difference on my sawblades - I can still break them for a pastime. Operator error on my part I think!!!!!!!

[Aurarius]

Some makes or types of setting burr are more prone to grab than others. In my limited experience there are two critical factors: speed and pressure.
Try to have the burr rotating at more or less working speed before it contacts the metal and use fairly light pressure. After the first few rotations you should get a feel for whether the speed and pressure are right or not. If the burr is still grabbing try adjusting speed and pressure up or down. For a 5mm setting burr (quite a large one) I'd use a fairly low speed.

[Summer]

Sorry no idea why it's happening, I go very slowly and I use candle wax, just dip the end of the bur into a candle while the bur is turning slowly, hope you manage to sort it :-)

[Tabby66]

I'm thinking speed (possibly too fast) and the steadiness that you're holding the hand piece with, I find burrs sometimes catch/snag, if I don't hold the hand piece firmly enough.

[mizgeorge]

It can also happen if your flexshaft is even minutely off centre which, with larger burrs, will set up a tiny amount of 'chatter' and catch the metal. I'd also agree that if you don't have a variable speed handpiece that goes down to 0rpm, ideally with a foot control, you may have problems with keeping things slow enough as well.

[Gemsetterchris]

It's a speed thing mainly, you'll want super fast or then use hand power.
I generally avoid using big size burrs as they can be abit vicious with those big teeth.
I often use much smaller ball burrs when doing big stones.

[Dennis]

Hi Kermit,

We are mostly agreed that speed is the problem. You succeeded with the 0.4mm burr, because by luck or judgement the speed was right. The peripheral speed of the 0.5mm burr will be a little faster, but not fast enough to prevent juddering for that size.

To avoid more trial and error and potential disaters, I suggest that you start your seat with a suitably sized ball burr, which also saves wear on the more expensive setting burr.

Then turn the setting burr (dipped in a little oil), by hand using a universal handle. You will get a perfect match, provided you have used callipers to check burr and stone sizes.
Although I have used rotary tools all my working life, I mistrust them so much for this application that I have both burrs ready mounted in handles and do the whole thing by hand.

Dennis. http://www.cooksongold.com/category_...iversal+handle

Oh and why not prepare the tube segment before you cut it off and transfer it to your ring?

[theresa]

I agree with Dennis on the last bit.
Since seeing a demo on Ganoksin where they worked on the tube before cutting it to length I have found this method to be the easiest.
Sometimes I attach the tube to the ring and then work on it so there is more metal to hold in the vice.
Horses for courses really....

[Kermit]

Thanks for all the suggestions - sorry it has taken me a while to respond. I have been laid low with an infection in a tooth that has absolutely knocked me for six

I think the flex shaft I'm using is probably not great, and although it does have five different speed settings, it is not a foot control that I can take right down to 0rpm. You've all given me lots to work with though, so I'm not giving up yet!