Any ideas how to undo these screws?

[Ian PParticipant @ianp]

Posted by pgk pgk on 12/11/2016 23:22:55:

Dental handpieces are usually angled. The burs on high speed units won't last long without hooking up for the coolant. The handpieces are cheap enough on the auction site.. but you'll need some hose with the handpiece connector. The free end you should be able to cobble together to both a compressor and pressure bottle with some diy adapters. I was never successful using diamond burs to shape the odd steel implant.. much happier with steel or carbide burs – at least they cut fast until they blunt and they're cheap enough.

pgk

From your reply I gather you have some knowledge or experience of dental equipment. I used the term dental handpiece but what I had in mind was just the angled head without an air turbine. I see they are made for use with electric motors which would suit this purpose better.

Do you know anything of the internal construction of the 'contra' heads. They mostly seem to have two angles that the drive passes through which infers that there are two sets of gears internally. If it works I have inserted an image here of the type that seem to be quite common.

I can imagine that the whole head is not going to be robust but its only going to get occasional use so it might suit the purposes. I have a very old (30+ years) Swiss made straight handpiece and its motor that was used for some sort of bone surgery so was hoping I could adapt the motor to the newer mount systems.

Can you suggest a contra head that might be suitable, or any links to the internal details of construction?

Ian P

[Ian PParticipant @ianp]

Posted by peak4 on 13/11/2016 02:33:16:

Leave to soak in a 50/50 mix of AFT & Acetone dripped on regularly and keep tapping it with a small hammer or similar, ideally end on using a home made cranked punch. a la ____|—–|__

Hex or Torx insert on a 6mm or 1/4" ring spanner, depending on the insert, again shock loaded with a hammer on the spanner.

Stop it camming out with opposed wedges against the opposite face, possibly with G cramp support to save bending that side.

Cross fingers and invoke any popular spells you can think of.

Edited By peak4 on 13/11/2016 02:34:53

All sounds a good approach, I have Acetone but what is AFT? or where can I get it?

Ian P

[blowlampParticipant @blowlamp]

This way usually works for me.

Martin.

[pgk pgkParticipant @pgkpgk17461]

Posted by Ian Phillips on 13/11/2016 13:35:52:

From your reply I gather you have some knowledge or experience of dental equipment. I used the term dental handpiece but what I had in mind was just the angled head without an air turbine. I see they are made for use with electric motors which would suit this purpose better.

Do you know anything of the internal construction of the 'contra' heads. They mostly seem to have two angles that the drive passes through which infers that there are two sets of gears internally. If it works I have inserted an image here of the type that seem to be quite common.

I can imagine that the whole head is not going to be robust but its only going to get occasional use so it might suit the purposes. I have a very old (30+ years) Swiss made straight handpiece and its motor that was used for some sort of bone surgery so was hoping I could adapt the motor to the newer mount systems.

Can you suggest a contra head that might be suitable, or any links to the internal details of construction?

Ian P

I've only ever used the air-powered stuff – mostly on teeth although ocassionally I made tiny hip toggles or cut off a leg ring or other metal object.. also used them for fine spinal surgery. the high speed turbines just paint away bone with much less vibration than official orthopaedic burs (on small stuff when you can;t lean on it).

The slow speed handpieces for polishing really isnt good for trying to cut your slot and doesn't have in built coolant. You'ld get too much vibration. High speed 250,000+ rpm and it's way easier to hand hold accuratly. Slower speed handpices have the motor/turbine in the base and come as 2-parts.. the geared head adding on. Highspeed handpieces we used had the turbine built into the single handpiece. The compressor we had (a small bambi dental one) wasn't very large so I'd expect an Aldi type moderate priced compressor would run it well enough. Its just the nuisance of hitching it all up.

If you go look at schein-rexodent dental catalogue you can spend a lifetime looking at all the options.

Geared as you said.. tougher than you think…biggest killer of slow speed handpieces was eventual ingress of polishing compounds getting into things 'cos staff didn't clean and lube them properly after use. At least the seperate head part was cheap enough to replace. High speed handpieces we hardly ever killed despite them being dropped and abused.

[SpurryParticipant @spurry]

I have seen ATF – Auto Transmission Fluid suggested in the past, but AFT is a new one on me.

Pete

[John ReeseParticipant @johnreese12848]

If everything listed above fails to work I would try using an alum solution to dissolve the steel. Make a dam of modelling clay to contain the liquid. Pour alum (as used for pickling) into the dam and wait. There are several references to this product on you tube.

[Ian PParticipant @ianp]

Update

Thanks for all the suggestions which were very encouraging. I have made some progress and removed the first three screws without any problem..

I used an 8mm diameter cutting disk on a long mandrel to cut slots in the top face of the screws. I then ground a 1/4" hex screwdriver to the right thickness and curved the edge to sit in the concave slot I created. I put the bit in a small Jacobs chuck and used the chuck mounting thread to take a bolt that applied pressure to the bit.

None of the ones removed so far had any corrosion, they were just tight.

Incidentally, I made four small diameter cutting disks out of one normal Dremel disk by drilling extra holes in a standard disk and trimming each quadrant against a bench grinder. As it happens I am still using the first one I cut so I could have just used a worn down disk (except I didn't have one).

May post some pictures tomorrow.

Ian P

but

[peak4Participant @peak4]

Posted by Ian Phillips on 13/11/2016 13:39:05:

Posted by peak4 on 13/11/2016 02:33:16:

Leave to soak in a 50/50 mix of AFT & Acetone dripped on regularly and keep tapping it with a small hammer or similar, ideally end on using a home made cranked punch. a la ____|—–|__

Hex or Torx insert on a 6mm or 1/4" ring spanner, depending on the insert, again shock loaded with a hammer on the spanner.

Stop it camming out with opposed wedges against the opposite face, possibly with G cramp support to save bending that side.

Cross fingers and invoke any popular spells you can think of.

Edited By peak4 on 13/11/2016 02:34:53

All sounds a good approach, I have Acetone but what is AFT? or where can I get it?

Ian P

Yes it was a typo, ATF as in auto transmission fluid.

That's what you get for typing in the wee small hours.

Sorry for the confusion.

[ria aroraParticipant @riaarora30290]

Heii….

I am new here and want 's to discuss about shaping machine parts.

[MikelkieParticipant @mikelkie]

I like Michael G 's idea first then follow up with Stevetee's suggestion. Good luck.

[MikelkieParticipant @mikelkie]

I like Michael G 's idea first then follow up with Stevetee's suggestion. Good luck.

[Author]

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