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Old 07-13-2019, 10:45 PM
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MetalWolf MetalWolf is offline
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Default First time turning any sort of soft materials

Well, this evening I decided to make those Teflon? bushings... had to grind my own HSS cutting tools. Was a little bit of a Challenge considering it seems to be a bit different for soft plastics as to how you grind the HSS... IJMO.

So I gave it a whirl, Not perfect but turned out smooth considering its not NASA speck crap I'm doing.

These bushings on the hydrostatic trans pump were broken and sloppy at best but were enough of the old ones left to go by. one is a one-piece and the other one is a two-piece shop Manuel gives tolerances for them so that helped out some too.

Any rate I took the old ones to a buddies machine shop and asked him what to make them out of and he handed me some high-pressure machinable Teflon
so that's what I used...

Anyway, don't laugh too hard but here are some pics to show how things are coming along with it I took off the slide bar so you can see the bushings It's a bit hard to keep this stuff clean with all the grease and oil...

One bushing was basically a big washer with slots milled in the center of opposite sides, the other was more like a washer with a shoulder the rail slides over and the other washer snaps over a grove was a little surprised I was able to get it to work as the shoulder that snaps to the other side washer was fairly thin and took me some time to get it right.
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Old 07-13-2019, 11:05 PM
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Default First time turning any sort of soft materials

Looks good from here. as long as it does the job, it is good. Machining takes a little time to learn, especially with all the different type of materials you can work with.


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Old 07-13-2019, 11:16 PM
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Quote:
Originally Posted by toprecycler View Post
Looks good from here. as long as it does the job, it is good. Machining takes a little time to learn, especially with all the different type of materials you can work with.


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Thank's Brian.

I used the HSS because I was told indexable tooling was harder to use to turn it and it would come out much better if I used HSS to turn it...

it wasn't so bad other than the mess it makes compared to other materials looked like fine spaghetti long strings over chips or strands but came out smooth.

so I apparently did something sort of right I guess the fit is nice and not all sloppy like with the worn and half missing broken bushings.

I'm happy with the way they turned out and with the slide plate arm on it; It operates nicely too. no binding or falling off issue.

I wouldn't call my self a machinist or hobby machinist... but more of having the somewhat ability to copy something like this most of what I do is minor stuff and tolerances are not of real importance for the most part... but I'm sure ill run in to such things where it does matter and by then maybe I might be able to tackle some more sophisticated things...
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Last edited by MetalWolf; 07-13-2019 at 11:23 PM.
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Old 07-14-2019, 07:48 AM
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Plastics are a different beast. It's all about controlling the heat applied to a very tiny area through friction. If the tools are too sharp they dig in, too dull and they smear.

I keep a stash of well worn tools and often have to 'hunt' for the right combination to get a good cut in plastics. Cutter taught me a little trick years ago that if you have a bit more radius on the tip of your cutter rather than a fine point, it leaves a smoother finish. The worn out tools seem to develop that edge a bit more naturally and better than I can re-create when grinding my own so it yields better results.

The stuff that's marketed as machinable does tend to work better, and I think a lot of it is usually a lot more heat resistant as well.
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Old 07-14-2019, 08:54 AM
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There are inserts for plastics, I have a couple thanks to KiethR.
The basic difference is a positive rake and a large chip relief...and sharp, of course.
Plastic is a pleasure to cut, hard to remove a 1/2 thou though. Last job I did on plastic was the bushings on an exercise machine.
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