[balsaman]

First chunk is in progress...before and after. More operations to do on this part. It's the top half of the crank case.

[nick.gilling]

Good wor there, very interesting to see this one come together.

[balsaman]

nice radius'

[balsaman]

more progress

[nick.gilling]

Looking good, you must be chuffed with your DIY cnc mill!

How many cuts did it take to profile the inside? How long did it take?

Also, how did you cut the external radii? with some kind of router bit?

Excellent stuff!

[nick.gilling]

or did it just take a lot of cuts stepped down?

You've probably gathered I don't have a clue how a CNC works!

[balsaman]

I love my mill.

Inside took an hour or so to cut out with a .25 em., .050 deep steps down.

Outside radii was done with a .375 ball mill with .005 step over

I used a cheap edge finder to find the edge for the inside pocket and that's the last time I use it. The inside pocket is out by over .010. Won't matter but it bugs me.

Eric

[Stevie]

Eric

Use a 1/4 dowel pin
Run it about 500rpm
Lightly touch it with a magic marker
Move it to the edge very slowly (like 0.001 at a time)
Once you see a scuff of the black and see the steel showing through; you have the edge

[nick.gilling]

10 thou isn't much!

Steve, this conversation was brought up at local model engineering club last night.

I haven't used the mill much but I always wondered how people find the edge!

How do edge finders work?

I was thinking along the same lines of you, get some ground steel in the chuck, set it running and see when it just touches. I was thinking of some way of using a multi meter or led circuit to check for continuity but the marker will be easier.

So once you see a black mark on the workpiece you stop. And you will see the steel of the pin in the chuck too?

Someone else mentioned lazer finders but these will have a width of lazer beam? and are probably expensive.

Another guy says he uses a 0.010" feeler gauge, not with it running but just take it up until you can slide the feeler in and out. You have to make sure the edge of the cutter is at its nearest point to work though. You might as well just do what you said with a bar of known diameter.

Thanks

Nick

[Stevie]

10 thou isn't much!

Steve, this conversation was brought up at local model engineering club last night.

I haven't used the mill much but I always wondered how people find the edge!

How do edge finders work?

I was thinking along the same lines of you, get some ground steel in the chuck, set it running and see when it just touches. I was thinking of some way of using a multi meter or led circuit to check for continuity but the marker will be easier.

So once you see a black mark on the workpiece you stop. And you will see the steel of the pin in the chuck too?

Someone else mentioned lazer finders but these will have a width of lazer beam? and are probably expensive.

Another guy says he uses a 0.010" feeler gauge, not with it running but just take it up until you can slide the feeler in and out. You have to make sure the edge of the cutter is at its nearest point to work though. You might as well just do what you said with a bar of known diameter.

Thanks

Nick

<10 thou isn't much!>
0.01 is a country mile to a tool and diemaker

<How do edge finders work?>
not very well unless you buy the best


<Another guy says he uses a 0.010" feeler gauge, not with it running but just take it up until you can slide the feeler in and out. You have to make sure the edge of the cutter is at its nearest point to work though. You might as well just do what you said with a bar of known diameter.>

If it's running the runout can be allowed for; no ch/k will be dead on
A good tool holder (say CAT40) would be
If it's running out; you simply use this method but watch for at least 1/2 the marker to be scuffed around the dowel pin; then the run out is eliminated
Runout might only be 0.0005; but it's important if your working to 0.0002

[balsaman]

.010 is a country mile.

Up to now I have been using the dowel pin method with decent success but figured a "real" edge finder would be more "profesional" and better. Ha! Why do I never learn to stop experimenting on the time consuming parts! I plan on recutting the inside .010 bigger all around so at least it "looks" right. I also have to re-spot drill the 5 oil pan bolt holes as they are currently off by the same .010". I spoted them .050 deep so will go .100 deep the second try around and then drill them at the same time while it is in the vice. They will be tapped 6/32 eventually.

E

[nick.gilling]

yeah if the holes are out too you'll see a slight step were the next bit bolts on I guess.

It'll be great though, I have every confidence!

[balsaman]

It'll be great though, I have every confidence!

At least one of us does!

[Ken_Shea]

Eric,
Here is a quality edge finder, that will work and work every time.
1000rpm - 1200rpm

Precise, repeatable, affordable.

http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=4822373


Ken

[Stevie]

those don't work; I have 35yrs experiance; and they are no good

You need the chair type if your going to actually use one

[balsaman]

Ok, I did some measuring of the part and stuff was not making sense. I know now what actually happened. When I cut to top side, I was using what I thought was a .375 EM. when I cut the bottom, the pocket seemed off center by .010 - .015. measuring the wall of the part, I found that the one side was ~.250" like it should be, and the other (farther from 0,0) was ~.270". If it was off center because I don't know how to use an edge finder, it should have been ~.240 with the other side being ~.260.

Measuring the outside I discovered I am ~.020 big in both x and y. Turns out the .375" cutter I was using was reground to something like .355". When I found the edge with my edge finder, it did a fairly good job, but since the part is .020 larger than it should be, it placed the pocket .010 off center.

What I will probably do, is recut the inside .010 bigger, but add (subtract?) .010 to/from the edge when finding the edge, so it ends up in the middle, if that makes any sense.

man I hate when that happens. It seems I learn the hard way.

E

[Ken_Shea]

those don't work; I have 35yrs experiance; and they are no good

OH GOOD GREIF, what ever........

[nick.gilling]

Never mind, just add the 0.010" on next time for the decreased cutter rad and all will be ok!

[Stevie]

those don't work; I have 35yrs experiance; and they are no good

OH GOOD GREIF, what ever........

well if you don't want to learn from experiance

I'll just take my toys elsewhere

[balsaman]

Hey, let's just agree that what works for one person, does not always work for another. Let's everyone just do/use what works for them and be done with it.

I appreciate all the experience and advice from everyone. In the end I will try lots of stuff and do what works for me.

No one is allowed to take the bat and ball and go home.

Eric