Help in making a tiny bushing
Re: Help in making a tiny bushing
Something that I hadn't considered is that you may be running the spindle way too slow.
This combined with cutting tools that are not real sharp and the rod sticking out a bit too far from the chuck could cause all sorts of finish and size issues.
With a bushing of that size in brass I'd most likely be running the lathe at its fastest spindle speed.
I can't think of a manual lathe that could possibly turn too fast for a small part such as this.
This combined with cutting tools that are not real sharp and the rod sticking out a bit too far from the chuck could cause all sorts of finish and size issues.
With a bushing of that size in brass I'd most likely be running the lathe at its fastest spindle speed.
I can't think of a manual lathe that could possibly turn too fast for a small part such as this.
Glenn
Operating machines is perfectly safe......until you forget how dangerous it really is!
Operating machines is perfectly safe......until you forget how dangerous it really is!
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Re: Help in making a tiny bushing
I was just making 7 mm long bushings, 0.08" diameter, 0.067" ID. I start with 3/32" low fuming brass welding rod. Why? Had some! Face. Spot. Drill. Turn OD. Cut off.
No real problem, save for being careful not to let the hole wander- sharp drill with equal flutes and frequent lube. The tool was HSS sharpened to a razor edge as described on my site. IMO, that was about as long as one might dare go without support, and longer than many would feel comfortable with. Did 'em at work on the HLV, but it would have gone the same on my Logan.
No real problem, save for being careful not to let the hole wander- sharp drill with equal flutes and frequent lube. The tool was HSS sharpened to a razor edge as described on my site. IMO, that was about as long as one might dare go without support, and longer than many would feel comfortable with. Did 'em at work on the HLV, but it would have gone the same on my Logan.
Conrad
1947 Logan 211 Lathe, Grizzly G1006 mill/drill, Clausing DP,
Boyar-Schultz 612H surface grinder, Sunnen hone, import
bandsaw, lots of measurement stuff, cutters, clutter & stuff.
"May the root sum of the squares of the Forces be with you."
1947 Logan 211 Lathe, Grizzly G1006 mill/drill, Clausing DP,
Boyar-Schultz 612H surface grinder, Sunnen hone, import
bandsaw, lots of measurement stuff, cutters, clutter & stuff.
"May the root sum of the squares of the Forces be with you."
Re: Help in making a tiny bushing
No-one has yet mentioned that it is possible to use, say 3/8" or 7/16" rod, drill the center and then do the o.d. in 1 deep and 1 very shallow finish pass. The deep pass can be done because the full diameter rod is supporting the cut. The finish pass may or may not be necessary depending...
Something I learned from an old Serbian toolmaker.
--earlgo
Something I learned from an old Serbian toolmaker.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
Re: Help in making a tiny bushing
I'm going to assume that the situation at hand does not present any problems with how it's held. Either in a good three jaw, a four jaw, or collets.
There's no real need to use larger material. The length of the bushing is well within the three times the diameter in length for machining.
If diameter is critical, it's real dangerous to take a large cut, hoping to hit size. It often results in parts that are not round (deflection between jaws if the chuck is not good), or taper that would have been removed in the finish pass(es).
It's also risky taking a deep cut, followed by a shallow cut. Because tool loading isn't consistent, the second pass generally results in material being removed that one might have hoped remained. That said, I've always taken finish cuts in three passes. One, which is one third the amount of stock remaining, then a second pass of equal depth. Measure, and take the part to size. By following this procedure (which I acknowledge to be slower than other methods), you can generally produce good parts when tolerance is tight.
Harold
There's no real need to use larger material. The length of the bushing is well within the three times the diameter in length for machining.
If diameter is critical, it's real dangerous to take a large cut, hoping to hit size. It often results in parts that are not round (deflection between jaws if the chuck is not good), or taper that would have been removed in the finish pass(es).
It's also risky taking a deep cut, followed by a shallow cut. Because tool loading isn't consistent, the second pass generally results in material being removed that one might have hoped remained. That said, I've always taken finish cuts in three passes. One, which is one third the amount of stock remaining, then a second pass of equal depth. Measure, and take the part to size. By following this procedure (which I acknowledge to be slower than other methods), you can generally produce good parts when tolerance is tight.
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Help in making a tiny bushing
Well that explains why no-one mentioned it.
I'd ask the fellow who used it frequently, and explained it to the rest of us, but unfortunately he is, and will be, unavailable.
Some suggestions are good, some not so much.
--earlgo
I'd ask the fellow who used it frequently, and explained it to the rest of us, but unfortunately he is, and will be, unavailable.
Some suggestions are good, some not so much.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
Re: Help in making a tiny bushing
earlgo-
That method has its place, and can be quite useful. I've used it myself, but only when there are no other options.
When I was running my shop, a test fixture I made for Litton required a half dozen pieces of 5/8" diameter brass with a projecting piece about a half inch long, but only thirty thou in diameter. I was restricted to the 2,000 rpm offered by my Graziano---but making the parts was a piece of cake. I did as you suggested, turning the desired diameter slightly oversized, and taking the cut in only two passes. First one, short, to remove the majority of stock, the second one to take it to size. Repeat until I had the desired length, then I turned to polishing to establish final size and to blend the cuts. Turned out great!
Harold
That method has its place, and can be quite useful. I've used it myself, but only when there are no other options.
When I was running my shop, a test fixture I made for Litton required a half dozen pieces of 5/8" diameter brass with a projecting piece about a half inch long, but only thirty thou in diameter. I was restricted to the 2,000 rpm offered by my Graziano---but making the parts was a piece of cake. I did as you suggested, turning the desired diameter slightly oversized, and taking the cut in only two passes. First one, short, to remove the majority of stock, the second one to take it to size. Repeat until I had the desired length, then I turned to polishing to establish final size and to blend the cuts. Turned out great!
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Help in making a tiny bushing
Have any pictures of the coupler ? From what I imagine you should be dealing with something like this :
http://losmandy.com/hi-rez-images/MC.jpg
What is the mount your repairing ?
I'm all into the astronomy thing ....
Steve S
http://losmandy.com/hi-rez-images/MC.jpg
What is the mount your repairing ?
I'm all into the astronomy thing ....
Steve S
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Re: Help in making a tiny bushing
Steve,Steve S wrote:Have any pictures of the coupler ? From what I imagine you should be dealing with something like this :
http://losmandy.com/hi-rez-images/MC.jpg
What is the mount your repairing ?
I'm all into the astronomy thing ....
Steve S
I doubt that a spur gear on the end of a flexible coupling is a good idea -
The coupling will need to be rigid, not flexible,Ramv wrote:Hi,
I am attempting to make a small bushing that has an internal diameter of 3/16" and outer diameter of 6mm. This bushing connects the shaft of a servo motor to a spur gear that drives a worm/wheel arrangement of a telescope.
- Nick
Re: Help in making a tiny bushing
Depends, doesn't it? If both components run in bearings, and are rigid in and of themselves, then it wouldn't matter how they were coupled, assuming the coupling was self centering. If the coupling is expected to carry either of the components, then I'd agree.Magicniner wrote:The coupling will need to be rigid, not flexible,
Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Re: Help in making a tiny bushing
So what mount are you working on ?
Curious , no gearbox between the motor and drive ?
Steve
Curious , no gearbox between the motor and drive ?
Steve
Re: Help in making a tiny bushing
Oppsss , Sorry Magicniner , though you were Ramv .
Most mounts use a gearbox between the servo motor and spur gear . If the coupler is rigid it can cause the tracking to jump . Not as important if the scope is for visual or video astronomy . But awful for long exposures , compound possible by the focal length of the scope .
Just Saying ...
Most mounts use a gearbox between the servo motor and spur gear . If the coupler is rigid it can cause the tracking to jump . Not as important if the scope is for visual or video astronomy . But awful for long exposures , compound possible by the focal length of the scope .
Just Saying ...
Re: Help in making a tiny bushing
As these guys all say, ditch the carbide and just simply grind a HSS bit. You may have to experiment for best angles
Start with over sized brass solid rod,
Drill and ream to the inside diameter.
Part off the thick walled bushing at this point.
Using Loctite, glue the bushing onto a steel shaft. (the drill shank if you have nothing else).
Chuck up on the steel shaft and turn your bushing to finish diameter.
Remove bushing form bit or shaft with heat.
Start with over sized brass solid rod,
Drill and ream to the inside diameter.
Part off the thick walled bushing at this point.
Using Loctite, glue the bushing onto a steel shaft. (the drill shank if you have nothing else).
Chuck up on the steel shaft and turn your bushing to finish diameter.
Remove bushing form bit or shaft with heat.
Charlie Pipes
Mid-South Live Steamers
Current Projects:
Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
20 Ton Shay (Castings and Plans Purchased for future)
Mid-South Live Steamers
Current Projects:
Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
20 Ton Shay (Castings and Plans Purchased for future)