Pull My Finger

[Kim]

Nice parts, Zee! 

See, being forced to stay at home can have some benefits? Maybe? 
Kim

[zeeprogrammer]

See, being forced to stay at home can have some benefits? Maybe? 

Maybe?

I'm optimistic but I haven't figured out how to get out of 'outside duties' such as gardening, weeding, and mowing.
(I know many of you are into that. But that's what it takes.)
Not to mention toilet bowl or bathroom cleaning.

I'm okay with the dish washing (for the most part  ). I eat well and have T to thank for.

Ah...I see I've strayed.

[crueby]

Reminds me of the commercial where the guy is teaching his retriever dog how to drive. Going past the pond, starts yelling "no duck, no duck!" As the dog drives into the pond...

[zeeprogrammer]

Still plugging away at learning about these Sherline machines.
Or perhaps I should say, still learning about how to machine. 

The eagle eye amongst you missed the fact that I had drilled and reamed a 1/4" hole in the lever that should have been an 8-32 tapped hole.
I think I have a way around that without remaking the part but we'll see.

The connecting rods were 'made' but I still need to make some buttons to round the ends.
Also started on the finger tabs. I still need to make the recess and knock the corners off.
The posts are done (other than sanding).

A few issues....

1) The crank is supposed to be made out of steel but I have none. I don't know why aluminum couldn't be used.
2) Not sure what I'll do about flywheels. I may make them out of flat aluminum or try and order some that would work.

The biggest thing bothering me...

Using an end-mill to trim a part to size....
I would repeatedly drop Z and trim some off. But all of a sudden I was cutting air.
I kept dropping Z (by a few thou) and still cut air. That happened a few times.
Then finally I was cutting metal.
What gives? It was as if turning the Z knob wasn't doing anything.
This happened on two parts...and always nearly at the point I was trying to machine to size.

[AOG]

Zee, it sounds like backlash in the z axis. The best way to avoid it is not to reverse when coming off the part. If you do have to come off the part in the z axis make one complete turn of the handle. If you do that in both directions it will automatically take up the backlash.

Tony

[zeeprogrammer]

Thanks Tony. That was my first thought. But I hadn't done any reversing (-Z). Only positive. And strange it only happened when I was trying to make my final cut.

[crueby]

Other thing to check is that the end mill is not slipping in the holder - if the flat in the notch is not lined up well when you tighten the set screw, it can slip a little. That reminds me - I learned to have a few spare setscrews, with a lot of use they do wear out, and the hex wrench can slip. Pain in the elf-tootie to get the screw out if it strips the drive socket.

Tony is right about the backlash, when lowering the headstock I like to go past the setting and raise it back to the tick I want.

Oh, and did you sort out the hot belt/pulley isssue?

[zeeprogrammer]

Thanks Chris.

I'll check the end mill. I haven't swapped it out of the end mill holder since I started this...but screws tend to loosen.
The thing is...this only happens after I've milled down several times and am looking to do the final finish pass. (I don't think I raised the Z axis at any time).
And it happened on two parts!
I have to think it's something about my process and not the machine but I'm stumped. I did the same thing every time except the last pass was at -.035 instead of the -.05 that I was working with to get 'close'.

It would be easier to fix the machine rather than to fix me. 

As for the backlash, yes that's the way I'd do it but for the first time. If I'm just lowering Z (after the first engagement) I wouldn't think I would have to take care of backlash each time. No?

I haven't taken care of the hot belt/pulley issue yet.  I'm ashamed. I'll do that next.

[crueby]

When lowering the headstock, always go past and raise back up to the spot you want. Between the backlash and how tight the gib is, its the only way to be sure of the position. You are using the lock on the z axis, right?

[steam guy willy]

The body of the post is just aluminum, so it drills/taps very easy.

I got my QCTP from LMS. According to their product documentation, it's all steel construction.
I don't know if it's been treated to make it hard or not.

I can always give it a try and see what happens.

I got a QCTP for my Unimat lathe and it was too tall ..so ..I sawed off the bottom.about 1/4 " and turned up the bottom face . This was just mild steel with no Hard spots..

Willy..

[Art K]

Zee,
Good to see you are still making progress. I generally use a Bridgeport style knee mill. It moves the table up into the cutter. If I understand Chris right that on the Sherline column type to get rid of the back lash go down past and back up. The opposite of what I'm used to doing on a Bridgeport.
Art

[zeeprogrammer]

You are using the lock on the z axis, right?

Oh yes. To some extent in tandem with moving the z axis...to slow it down and lock at the point I want.

On that note...for this project anyway...I haven't done anything with the X and Y locks. One doesn't work (I need to make that mod) and the other is nearly impossible to get to (because of the way covers - which I may get rid of.)

When lowering the headstock, always go past and raise back up to the spot you want.

For every movement down even if there was no movement up?
Or are you talking about moving the first time from an unknown position to a known position?

Ah no...I see. Must be every time. If I only go down the head may not go down due to backlash.
Geesh... Seems so fundamental.

That would explain it only seemed to happen at the end...because I was moving a smaller amount.

Thanks.

[EDIT: Got interrupted in my post. Thanks Willy. I did get the QCTP sorted out. At least so far.  Thanks Art. It may have been so long since I milled to size that I forgot a fundamental. Most likely I had a dum-dum moment.

[Flyboy Jim]

When lowering the headstock, always go past and raise back up to the spot you want. Between the backlash and how tight the gib is, its the only way to be sure of the position. You are using the lock on the z axis, right?

Yes...........what Chris said..........every time, as well as using the lock. It's actually pretty much the same way for the X and Y axis. Always come to your desired setting from the same direction. Takes backlash out of the equation.

Jim

[zeeprogrammer]

Still feeling foolish. I'm having to go back to 1st grade and have a couple of questions...

1) Let's say I'm milling a pocket. How does the process of lowering past target and then back up work? Can't go past. What I've done is touch off a piece of paper and then plunge to depth.

2) On my PM25 mill, I've typically used the fine Z control to move the quill to depth (after using the big Z knob to get near the target). Does the same process apply? As I recall, there was resistance when moving down to target but significant play when I raised it.

[crueby]

Still feeling foolish. I'm having to go back to 1st grade and have a couple of questions...

1) Let's say I'm milling a pocket. How does the process of lowering past target and then back up work? Can't go past. What I've done is touch off a piece of paper and then plunge to depth.

2) On my PM25 mill, I've typically used the fine Z control to move the quill to depth (after using the big Z knob to get near the target). Does the same process apply? As I recall, there was resistance when moving down to target but significant play when I raised it.

For a blind hole, best you can do is press down on the headstock while plunge cutting in. Remember to check that you have a center cutting end mill bit, where two of the bottom edges go to the center. Otherwise it won't do a plunge cut.  And the sherline only has one knob, so the same process as your pm25 can't apply.
No dumb questions, only ignorant machinists that won't ask! All stuff everyone has to learn. Wish we had classes on this stuff when I was in school!