Toolpost Spindle Drive: Motor off Cross Slide

[Antman]

Sorry to bring back memories of your local house-of-pain, but I was wondering if anyone remembers the type of dentist drill that worked off a system of pivoted arms with pulleys at the joints giving the handpiece almost total degrees of freedom. I would want to make a simpler, heavier system with only 2 arms, so I could mount the motor on the lathe bench to drive a toolpost cutting frame first (for slitting saws and external grinding) then later a toolpost spindle (for internal grinding), and giving the cutting frame or spindle freedom of movement on the cross slide. Can someone please direct me to a diagram of that type of dental drill with detail of the arms, pivots and pulleys. Last time I saw one I must have been about 10 and didn’t take in the details.
What kind of power and rpm (at the spindle) should I be looking at if I want to drive a slitting saw of 32mm diameter, 80 teeth, 0.3mm wide or 32mm x 64 teeth x 0.6mm? Will round 8mm belting be up to the torque required?
Thanx guys,
Ant

 

[Antman]

Well, after much Googling I did find this PDF of an old patent form. I wonder how practical a long round belt would be in transmitting the required revs and torque.
Ant

View attachment 282044 Dental or surgical engine Bonwill 1883.pdf

 

[sssfox]

Here is one still in production:

http://www.kabdental.com/small-dental-equipment/lab-equipment/Buffalo_belt-driven-motors.htm

It may be notable that they consider theirs heavy duty @ 1/5 HP.

As an aside, about 10 years ago, there was a guy I worked with who had an old dentist. This dentist used one of the belt-driven drills. The difference was that his was driven by his nurse, riding on something like a stationary bicycle. Talk about memories.

 

[rake60]

I can't give you the specs, but I do see one of those old drills every 6 months.
My dentist still uses 2 of them in his office.

He loves to share stories about his classic cars and old stainless steel StreamLine camper.
I'm sure he'd love to tell me about the drills as well.

I'll ask next time I'm in for my semiannual grinding and scraping.

Rick

 

[Herbiev]

Why not use air tools and hose. Sounds a lot simpler and longer lasting

 

[Antman]

Hey Herbie, thanks for the reply,
When I first started thinking about a toolpost spindle, I was thinking seriously about using my air grinder but then there was a post that said something about the bearings having too much runout and on mine I can feel the wobble on the bearings. Also, if I try to regulate the speed by dialing down the air pressure the torque just goes, I think it will just stall if I don't run it full blast. So I've been looking at Harprit Sandhu's spindle plans. He makes no mention of driving them. Herbie, are you suggesting that I use my air tool as a motor, say with a pulley in the chuck and a short belt to the spindle?
I don't know why I am so hung up on making gadgets, when I started with my workshop I thought I'd be wanting to make engines as soon as, but I'm still having fun making tooling and I'm a bit daunted to make an engine that won't run.
Regards, Ant

 

[hammer2100]

Antman, I found your post and I have one of those drills I think it still runs but doesn't have the handpiece. I can check to see if it runs if you would like to buy it. Say $75.00 plus shipping? Let me know.
Hammer2100
ps:I'm in West Virginia

 

[Antman]

Howdy Mark,
I don't really want a dental "engine" I was trying to suss out the pulley, belt and arm geometry of the thing. I think for a toolpost mounted spindle I won't need so much freedom of movement and I have sort of CoC'd an arrangement using only 2 arms, but with heavier construction, the dental engines are very lightly built.
As an aside, $75 might not be much to an American, but when that is converted to our local currency, the thin, flat South African Rand (ZAR), with shipping, bank rip off charges and goverment taxes on forex it would come to over ZAR1500. My workshop budget rates pretty low on the scale of our household priorities, I have one kid in university and our youngest cleverest one still in high school, so thinking ahead to 2014 I will have 2 kids at university. Also my big boy works like a slave but gets very little out, but he has a lot of ambition and I think is going places so he needs help most months.
Thanks anyway,
Ant

 

[Noitoen]

You should take a look at this [ame]http://youtu.be/Y1bvyFG3hWM[/ame]

 

[Antman]

Helder, thanx for the YouTube links. It seems like all I really need is one arm with pulleys on both ends and an adjustable pillar to mount it. Glad this thing is starting to look simpler. I think a powered toolpost spindle is a must have, I'm sure a lot of operations will work out simpler than transfering the workpiece to the milling machine.
Isn't that Lorch something! Where do you get a casting set? Don't like the idea of using the compound slide for long feed though.
Regards,
Ant