Gavztheouch's Mk2 Laser

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Ball Screw Test Ends Lathe work

Postby gavztheouch » Sun Jun 17, 2012 3:56 pm

Thinking of possible ways to machine the ends of my ball screws. They are too hard to turn well in my Myford hobby style lathe, so I will need to aneal the ends of the screws or weld/glue a softer steel to the ends.

Here I have bored a 6mm hole in a piece of m12 threaded rod representing my ball screw. Then I turned down my steel rod at one end to slip inside the bore of the screw. This time I welded them together but I have heard some types of loctite will glue these part together just as well and this means I do not have to expose my screws to the heat of the welder.

As my welded in steel ends are about 18mm in diameter I will be removing plenty of material meaning the OD will become conentric to the rest of the ball screw.

BallScrewTestEnd.jpg

BallScrewEnd.jpg
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Re: Gavztheouch's Mk2 Laser

Postby Enraged » Sun Jun 17, 2012 4:06 pm

they are usually hardened, so you need to grind off the top layer of metal. once you are through that, they cut very easily. it's also a great excuse for buying more tooling for your lathe :)
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Re: Gavztheouch's Mk2 Laser

Postby gavztheouch » Sun Jun 17, 2012 4:19 pm

Do you use a bench grinder to grind of the hard part, or do you need some sort of specialized lathe mounted grinder?

The problem with this option is my bearings are 12mm and the screws are 15mm. At 12mm I may just be under the surface of the lower part of the screw threads making threading difficult. I could maybe change to 10mm support bearings but this would mean faffing around with mail order returns, but I would then be well under the hardend areas.
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Stopmotion fun

Postby gavztheouch » Sun Jun 17, 2012 6:36 pm

I though while I was cutting threads on my lathe for the first time I would try and make a stopmotion animation of the process. Here are the results.



This was made with a GF-1 camera, Linux Ubuntu and ffmpeg
Last edited by gavztheouch on Sat Jun 23, 2012 2:51 pm, edited 1 time in total.
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Re: Gavztheouch's Mk2 Laser

Postby Enraged » Sun Jun 17, 2012 6:38 pm

we used a lathe mounted grinder, but you can even use something like a dremel grinder as long as you set it up right and take your time.

a quick search led to this: http://alisam.com/page/1gu8y/Metalworki ... lders.html

something like that would work, and I would imagine you could fab your own rather than buying one.
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Re: Gavztheouch's Mk2 Laser

Postby gavztheouch » Fri Jun 22, 2012 10:21 am

Ball Screws and bearings arrived today, one of the ball screws was bent quite a bit in multiple directions which was a bit disappointing but I think I can bend it back into shape. There are four "threads" running alongside each other, so in the photograph the screw appears to have quite a short lead. The lead of the screw is 20mm and the diameter 15mm.

LaserBallscrews.jpg
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Bent Ball Screw

Postby gavztheouch » Fri Jun 22, 2012 12:21 pm

bent.jpg


Here is a picture of the ball screw. You can see the "s" shaped bend towards the end of the screws, which looks difficult to remove.
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Re: Gavztheouch's Mk2 Laser

Postby Liberty4Ever » Fri Jun 22, 2012 4:50 pm

That begs the question... how does someone bend a 15mm diameter ball screw? Did they use it as a pry bar to lift concrete beams to free victims trapped in earthquake wreckage before shipping it to you? I know kids with that special power. Give them an anvil for Christmas and they'll tear it up Christmas morning.

Bummer about your ball screw. Hopefully there is a replacement coming soon.
Apparently, I didn't build that! :-)
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Re: Gavztheouch's Mk2 Laser

Postby macona » Sat Jun 23, 2012 9:56 am

Good luck straightening one. It is an art to straighten a ball screw to a point where it does not wobble when being used.

To machine them you just need a carbide insert. You can cut past the hard surface without too much of a problem. I had the do the 1-1/2" diameter one on the Z axis of my mill. Hardened steel is not too big of a deal as long as you have a solid machine. Also cermet inserts work even better.
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Re: Gavztheouch's Mk2 Laser

Postby gavztheouch » Sat Jun 23, 2012 11:19 am

Good luck straightening one. It is an art to straighten a ball screw to a point where it does not wobble when being used.


Hopefully this will be a last resort, Im hoping my supplier will replace the screw free of charge. He has gone rather quiet after I sent photos of the screw. :?

To machine them you just need a carbide insert. You can cut past the hard surface without too much of a problem. I had the do the 1-1/2" diameter one on the Z axis of my mill. Hardened steel is not too big of a deal as long as you have a solid machine. Also cermet inserts work even better.


I only have a Myford hobby lathe which I assumed would not be up to the job of cutting through the case hardening. Would you advise against welding an easily machinable end onto the screw, apart from looking rather messy im hoping it will work fine?
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