Date: Fri, 16 Oct 2020 18:39:28 -0700
Reply-To: Alistair Bell <albell@SHAW.CA>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Alistair Bell <albell@SHAW.CA>
Subject: Re: OT Friday , hard turning on the lathe with ceramic inserts
In-Reply-To: <A6462B55-9990-4482-81D4-F03FD944D960@comcast.net>
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Hey Eric,
I like that you liked the inside baseball type rambling on the turning.
And I’ll say, any mechanical win at home, no matter how trivial it might seem, is a bigger win than one at work.
And that lead to another trite observation. When I get home I’m done. I have little mental or physical energy to do much. It’s getting less so as I get more experience in the three machines I’m responsible for at work. But the learning curve on those cnc machines was steep for an old man like me.
It’s a paradoxical situation, I now have fantastic resources to make things but little energy left to do it :-)
Alistair
> On Oct 16, 2020, at 8:16 AM, Eric Caron <ericcaron96@comcast.net> wrote:
>
> Thanks Alistair,
>
> I enjoy learning from these stories.
>
> And, though my versions are kindergarten level compared to yours here’s mine.
>
> I noticed the old bulkhead doors were not functioning well. One opened pretty easy and the other very heavy.
>
> I took some time to try to figure it out.
>
> Turns out a long rod is bent cleverly to act as a spring loaded hinge. One side had two broken rods.
>
> After going to the hardware store to purchase rod stock I hand bent them with a vice. I channeled the do it yourself spirit of VW bus owners, and now have an easy to lift correctly opening door.
>
> Now, fingers crossed I get a bus back soon to improve my skills on!
>
> From aviation parts to bent rods, is a steep drop, but I share and enjoy your creative spirit!
>
> And, I’m still dreaming of a rear light compartment hinge.
>
> Eric Caron
>
>
>
>> On Oct 16, 2020, at 10:29 AM, Alistair Bell <albell@SHAW.CA> wrote:
>>
>> My family and friends just look at me blankly when I come home and tell tales of work. So I’ll bore you guys too.
>> And it’s not meant to be some boasting or war story type thing. I’m just pretty excited at being able to experience something new and I think there are listmembers with some machining skills who might be interested and maybe, maybe, give me some pointers.
>>
>> Been very busy at work with an ongoing project of many little aviation parts. But another job came in recently that was kinda cool. It’s to turn down 100 or so Igus linear guides. 20mm diameter, one end to have shoulder 14 mm diameter , 14 mm long. The other end drilled and tapped m10x1.5.
>> The rods are case hardened to 55-60 Rockwell. The hardening about 1.6 mm deep.
>>
>> My best carbide inserts would cut , but not nicely. So we got some sandvik ceramic inserts. Triangular, no rake, no chip breaker. I’ve never used this kind of insert before. There is, as you might guess, a range of ceramic insert types. These seem to be the most basic.
>>
>> The info on them points to running them hard and fast . Chips coming off red hot, sparks etc. Oh and either with flood coolant or dry. Intermittent cooling supposedly shocks and cracks insert.
>>
>> The lathe is a Haas TL-1 (cnc)
>>
>> I immediately broke one insert on a hand fed test cut. I mean, it broke so easily...
>>
>> Finally got the speeds and feeds right. About 400 surface feet per minute, 40 thou depth of cut, and 0.001 inch per rev. And I used constant mist coolant. I found the surface finish on the softer inside of the rods was better with the mist blasting. Note about measuring units. Lathe is set up in imperial, part was dimensioned metric.
>>
>> The cool thing was, once I got the offset dialled in, I could repeatedly get 10 micron over target diameter. It was extremely consistent. Id bring to final dimension with a quick touch of 400 grit paper. The paper gave a nice polish. I had a 50 micron tolerance on the diameter.
>>
>> So after about 15 parts done, and feeling cocky and happy, and the insert showing no sign of wear, the insert shattered on number 16.
>>
>> So the plan is to index insert after 10 rods. Have potentially 6 cutting edges on each insert. Inserts were only 13 bucks each. Oh and if these inserts didn’t work, our tool salesman guy was recommending CBN ( cubic boron nitride) inserts. They cost 10 X more.
>>
>> Drilling and tapping the other end was anticlimactic. Yes, drill and tap were expensive, but nothing exotic. And the drilling and tapping were done by lathe, rigid tapping.
>>
>> Well that’s that. I wish I could say more about the aviation parts. They are kinda cool shapes and made mostly from 7075 aluminum. That stuff is now my new love. It cuts so nicely and is noticeably harder than 6061. Of course it is, but you can really feel it when working with it . It’s a bit of an stretch to say it’s like steel, but in some ways not far off.
>>
>> Cheers
>>
>> Alistair
>
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