Miniature Taper Lock fittings?

[Roger]

So you have your gears and your shafts: how do you connect them so they will not slip?
Yes, you can use a boss and a set screw, but that's rather crude and can slip or mash the shaft.
You can try to drill a hole through the shaft and put a pin through - good luck with hardened steel shafts.

Or you can use a Taper Lock fitting but you cannot buy small ones, for motors with shafts in the 6 mm - 10 mm range. You have to make your own. Does anyone do this?

Cheers
Roger

[ArtF]

Havent tried it..interesting thought.. You could use square holes and a square shaft, or hex holes.. of course its hard to drill
square and hex holes... :)..

[Roger]

You could use square holes and a square shaft, or hex holes.. of course its hard to drill
square and hex holes... :)..

It's even harder to turn the shaft on an existing motor or ball-screw into a hex.  ;D

I'm replacing existing XL belts on my VMC. Slide-on compatibilty is a requirement. But the motors have round 8 mm shafts and the ball screws have round 9.5 mm shafts. So far, so good: the taperlocks are made, some GT2 pulleys have been made are are in use, but I am still machining some of the pulleys. A few tricks needed.

Cheers
Roger

[Mooselake]

Can you post some pictures, Roger?  Looks like quite a project to make a taper lock bushing that small, and modify the sprocket to fit.

Kirk

[Roger]

This is a 30T GT2 pulley for a 9 mm wide belt, with taperlock, on an 8 mm shaft.
The brown bit on the right is a M12x1 mm nut which tightens it up. Yes, the taperlock has to have a split.

The vertical rod in the middle needs some explaining. When you try to tighten the nut, there is a bit more friction between the nut and the taperlock fitting than between the taperlock and the pulley. So the taperlock spins and the nut never tightens. This is normally solved with a bit of key steel, but try doing that at these dimensions! (I did try, but the results were not good enough.)
Instead the purple rod goes through the pulley and into a key slot in the taperlock: two views are given. This stops any rotation. Once the nut is fairly tight you don't need the rod any more, so it is removed.

Photos of completed unit to follow in a day or two: I am still machining the GT2 teeth on these pulleys. I have made other GT2 pulleys but they are in use, and they had bolted flanges instead.

What I would love to do is to find others who have made simialr fittings.

Cheers
Roger

[John S]

http://www.smallparts2.com/catalogs-fil ... g%2022.pdf


Page 303.

Other companies do similar, just this one was easier to find.

[ArtF]

cool robot.....

Art

[Roger]

Hi John

Ah yes, Small Parts - our favourite gold-plated unaffordable supermarket. Sorry, but their local (AU) pricing puts them out of most hobbyist's reach. OK if on a Defence contract maybe.

That coupling on p303 might be OK for some light duty work, but it would NOT suffice on the drive for a CNC axis. We need far more security than that. There has to be zero risk of slip or backlash.

However, you mentioned other sources for miniature Taper Lock fittings: please, details!

Cheers
Roger

[Roger]

Ringfeder - yes, they have small taperlocks. 8 mm, 9 mm, 10 mm, but not 9.5 mm.
Do not ask me WHY the mfr of my machine chose 9.5 mm - I don't know!

In essence, what I am making is very similar to a Ringfeder RfN 7085, but with the outer taper as part of the pulley itself. Well, I have to bore the hole in the pulley anyhow: why not bore it as a taper?

Cheers
Roger

[Nate]

The Fischer Technik construction toy uses a flimsy version of this kind of fitting where there are tapered threads on the bushing and the pulley.

Do not ask me WHY the mfr of my machine chose 9.5 mm - I don't know!

Is it possible that it's a 3/8 inch part (about 9.53 mm) and the 8mm shafts are 5/16 inch (about 7.94 mm)?

You may be able to find parts for a 3/8 inch shaft regardless.

[Roger]

Is it possible that it's a 3/8 inch part (about 9.53 mm) and the 8mm shafts are 5/16 inch (about 7.94 mm)?

What a horrible thought!
It was built by an Australian company, and Australia went metric in the 60s, but it may be that the company was still using imperial in some places where they were dependent on American parts - such as ball screws and toothed belts.

Hum ... It's possible. I will have to find out when I take the XL pulleys off and put the GT2 ones on. Fortunately, since I am using split taperlock fittings, there is some room for a few 10s of microns variation.

Thanks for the suggestion anyhow.
Cheers
Roger

[Nate]

Is it possible that it's a 3/8 inch part (about 9.53 mm) and the 8mm shafts are 5/16 inch (about 7.94 mm)?

What a horrible thought!
It was built by an Australian company, and Australia went metric in the 60s, but it may be that the company was still using imperial in some places where they were dependent on American parts - such as ball screws and toothed belts.
...

FWIW It looks like Ringfeder does make a 7090 taper lock in that size.  (No clue why it's just that model.)

[Roger]

It looks like Ringfeder does make a 7090 taper lock in that size.

Indeed. I have enquired about pricing. I await the reply with great interest (and doubt).

Cheers
Roger

[Roger]

Photo as promised below. From top downwards:

Two large pulley blanks, one in PE and one in 6061. I KNOW the PE is not as strong as the 6061, but the diameter is 3x that of the smaller 6061 pulley, and I know the teeth on that size are strong enough. I know that nylon, in quite thin sections, is often used for toothed belt pulleys. So - an experiment. I suspect the teeth on the PE pulley will turn out excellent.
The PE blank has a taperlock unit in it, with brass nut. The big Q is whether the taperlock will hold against the PE, or whether it might slip. I don't know yet. I don't think cracking is a worry with industrial PE this thick. If it does slip I can put an Al bush insert into the PE with flange screws: commercial nylon pulleys have Al bushes and the nylon is molded around the bush.

Test GT2 pulley, 30T. Just one of a number of GT2 pulleys I have made. The others are actually in use. My cutter (which I made) may deviate from the official GT2 profile by a micron or two, but should I worry about a few microns when the belt face is fabric?

2011 Al alloy pulley in middle. There will be a 3:1 ratio between the big and small pulleys when they are finished. Yes, the bore in these blanks is tapered already: 3 degrees half angle.

TL insert on mandrel. It has 8.00 and 9.50 mm ends.
Taperlock inserts for 8.0 and 9.5 mm shafts: you can see the slightly different wall thicknesses.
TL inserts showing anti-rotation key slots used only when tightening the fitting
Pulley showing pin going through plulley into TL insert. (In this unit the key slot overlays the split, which has been hacked around a bit during experiments.)

Still to do: turn the ODs of the blanks down to correct values; cut GT2 teeth onto blanks; make up side flanges and fit to pulleys; fit and test.

Cheers
Roger

[mrehmus]

Not wanting to blow my own horn but I published an article on how to make taper lock bushings in issue # 11 of Model Engine Builder magazine. This type of mount for flywheels is frequently used (and made) by Model Engineers.

Tapers are always a bit tricky to cut because not only do the tapers, male and female, have to match, they must be cut directly on center or they will not have straight sides.

If you can find suitable locks, great. If not, contact me off the forum.


Mike