Re: [taigtools] turning endmill holders on a mill
- On 3/3/06, Jeff Demand <jdemand@...> wrote:
>Thanks for that piece of advice, Jeff. I think I did that. Quoting from my
> My experience with using a mill for lathe type work so far has been
> limited to thought games; still trying to make an adapter to fit taig
> stuff to my unimat, an exercise which has escalated to the 'no prisoners'
> stage. What DID strike me from your post was
> " is about perpendicular to the tangent of the surface being cut..." Could
> it be that you are not boring 'on centre'. Maybe try to set the boring
> cutter tip to also be in line with the centre of the drilled hole. (dial
> test indicator, +/- .001" is critical)
previous email, I "...aligned the cutting point with the center of the
drilled hole..." I think I must've not phrased it very well, but I think
this is exactly what you are suggesting. I did not dial that in, just
eyeballed it because I found that having boring bars dead-on-center is not
absolutely critical when I use them on my mill, especially for larger holes.
I think I'll play with that some more. It does seem that the carbide boring
bar was more rubbing than cutting, so I am thinking about grinding a HSS
boring bit with a fairly aggressive positive rake and making that very
sharp. Maybe it'll start cutting more than rubbing...
Thanks again for all suggestions.
> *********** REPLY SEPARATOR ***********
> On 3/3/2006 at 11:58 AM Vlad Krupin wrote:
> >Since I just asked for some insight about my not-very-cocentric end mill
> >holders, I figured I'd ask another question that stems from that. I know
> >that some people (Tom Benedict?) have successfully used mill as a lathe.
> >tried to do that yesterday, and failed miserably.
> >Since I could not make a cocentric 3/8" end mill holder on the lathe, I
> >tried drill it to .330" on the lathe, and then finish by boring it out to
> >size (.373") on the mill. I mounted a boring bar vertically in the
> >toolmaker's screwless vise, aligned the cutting point with the center of
> >drilled hole, made sure the angle or the 'top' surface of the carbide bit
> >about perpendicular to the tangent of the surface being cut, just like I
> >on my lathe. Then I advanced one axis by 0.005" so the boring bar should,
> >theory, enlarge the hole by about 0.01", and took a cut. LOTS of chatter.
> >Hmmm... maybe I miscalculated and took too deep a cut. Let's try that
> >Advance by another 0.005, take another cut - same result. Some of the
> >surface looks almost glazed, some - as if it has been gnawed by mice;
> >chatter marks in some places. Ok, maybe the feed is too slow. Increase
> >feed a little, add some cutting oil, take another cut - same result. We
> >getting pretty close to final tolerance here... Oh, well, forget the
> >we'll make this into a 1/2" holder. I want to figure out what's wrong.
> >the feed is still too slow. Increased the feed a bunch, so the shavings
> >should be about 0.003" thick. LOTS of chatter again. The surface does not
> >look 'rubbed' anymore, but still very rough. Hmmm... maybe RPM is too
> >slow... Carbide cuts faster than HSS, right? So, I doubled the RPM,
> >the feed accordingly. Same result. Just out of curiosity, I tried taking
> >0.01" deep cut. Horrible sound, smoke all over the place from the burning
> >cutting oil, the endmill holder got really hot. Not good.
> >Argh! I can cut the same steel with the same boring bar on my lathe with
> >problems! In fact, it cuts like butter, and does not even get too hot to
> >touch. My mill is relatively well-adjusted - the gibs are tight, the nuts
> >are tight, the leadscrew bearings are tight - everything is as tight as I
> >could get without having too much friction. There is less than 0.002"
> >backlash on either X or Y.
> >So, am I doing something wrong, or does the mill just 'flex' too much
> >compared to the lathe?
> >Vlad's shop
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> Demand Designs
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