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[Nikon1975]

I think the lesson #0 of the home machinist should be:"Don;t leave your mug next to the milling machine" ... I guess I will not need iron supplement for a while :-)

D.

[TomG]

I used to work in a die shop as a shaper hand and one of the guys I worked with was so good at grinding tools that he could direct the chips pretty much anywhere he wanted. If you left your cup anywhere near his machine, it would soon become filled with chips and he would just stand there smiling.

Tom

[Nikon1975]

Hi,

I am slowly exercising. I wanted to show a part I made and would like your advice on few issue:
           

I did this vee-block in Al6064 as I wanted to try the tilting of the head and because I might need it. 
For the flat surfaces I used a surface mill 50mm and the 45 degree cut and groove have been done with 6mm endmill two flutes coated. I started with a block 60 x 60 x 70 (approx).

Here are my issues:
1) When I put a round bar inside in the vice using the block, around 50 cm long, I have a 0.5 mm deviation between up and down, meaning the 45 degree thing is not perfectly parallel to the face.

2) In general, I really have problem in having accuracy in what I do: I cannot really see the scratches I do on the part with the scribe and I have difficulties to measure the mart while in the vise. If I take it out of the vise, I lose reference completely. 

3) I have marks in the surface finish. These are one each turn of the lead screw. I built a power feed, in order to be more consistent in my feed, still have to experiment.

4) I also noticed that the surface marks get better if I tighten the play of the table, but then it becomes very hard to turn it.

5) My mill is sitting on a wooden table and it is not attached to it. When the cuts get a bit more demanding the machine jumps.

I am looking at ways to improve the overall process and (correct me if I am wrong) I think the following would help:
a) Move the machine to an heavy table where it can be bolted. I made a design of a structure that should be rigid enough and add approx 50 kg to the assembly. It would be easier to buy the support cabinet, but this just weight 15 kg. Price would be approximately the same.

b) DRO: I think it would help me a lot not to get lost. I am looking at models from http://www.machine-dro.co.uk. They recommended the magnetic tape sensor and they are quite cheap. I don't see the point in going extra cheap, as these are things that I might also reuse if I change machine. 

c) Measuring equipment. I have calipers and that's it. What tool would you think will help to improve accuracy ? I was thinking first a set of micrometers (and the blue ink to improve the marking)

Thanks,

Davide

[EdK]

(05-25-2018, 03:14 AM)Nikon1975 Wrote: and the blue ink to improve the marking

Yes, get some layout fluid. I use it a lot and it definitely helps.

Ed

[TomG]

First of all, the part looks great. Accuracy and surface finish will improve with experience. Now for those questions:

1) I would not have tilted the head to mill the V in the block. It's much easier to rotate the part than the head. If the part had been held in the vise by the ends, rotated on a 45º angle. the V would have ended up parallel to the bottom. A quick fix after the fact would be to put the block upside down in the vise, resting on a round bar and take a clean-up cut on the bottom. Don't forget to tap it down before making the cut. A strip of paper under each end will make it easy to tell when the bar is seated on the vise.

2) The way to achieve accuracy is to use the graduated dials on the table, not machine to scribed lines. Take a trial cut, measure the part and set the dials to zero. Then you will know how much more needs to be removed. A DRO will help. but dials will work as well, just slower.

3,4) It sound like the gibs are too loose on the table. They need to be tightened enough to remove the play, but not so tight that you can't turn the cranks. Looking at the marks on you part tells me that the rpm is way too slow for aluminum. Be sure to use a calculator based on the diameter of the cutter and cutting speed of aluminum.

5) Unfortunately the jumping sounds more like a limitation of the machine, than what it is sitting on. You'll just have to learn its limitations. Just the same, a sturdier base couldn't hurt.

Micrometers are a necessary measuring tool in machining. Calipers require more skill to use accurately and are generally used for non-critical measurements.

Tom

[Nikon1975]

It's a bit of a chicken and egg problem: if you have a set of parallel, it's easy to make other parallels. If you have a 45 degree reference plate, it's easy to make another one. But I did not have a reference to flip the part 45 degrees in the vice. Additionally, I was loosely following a Youtube video in doing the vee-block and he was tilting the head.

But this is one of the things I have in mind: should I buy a set of parallels and angle plates ?

Thanks,

D.

[Vinny]

(05-25-2018, 03:14 AM)Nikon1975 Wrote: (and the blue ink to improve the marking)

I find the red layout fluid to be easier to see.

[TomG]

(05-25-2018, 10:29 AM)Nikon1975 Wrote: It's a bit of a chicken and egg problem: if you have a set of parallel, it's easy to make other parallels. If you have a 45 degree reference plate, it's easy to make another one. But I did not have a reference to flip the part 45 degrees in the vice. Additionally, I was loosely  following a Youtube video in doing the vee-block and he was tilting the head.

But this is one of the things I have in mind: should I buy a set of parallels and angle plates ?

Thanks,

D.

A set of parallels is mandatory, you will use them all the time.

Tilting the head will definitely work, but then it needs to be trammed in so it's perpendicular with the table. There are lots of other ways to achieve the 45º angle without messing with the head, but it does involve other tools for reference; a protractor, sine bar, angle plates or blocks, another V-block, etc. The machine is only the beginning. :)

Tom

[Highpower]

(05-25-2018, 11:40 AM)TomG Wrote: The machine is only the beginning. :)

Tom

Understatement of the year right there.

I feel it's roughly a 3:1 ratio. For every dollar/euro you pay for a machine, you need to spend 3 times that for the tooling needed to use it.

[Nikon1975]

Is it a bad idea to buy second hand micrometers? What should I look to see if they are good?

Thanks,

D