Thread: Is this a valid test?

Hi Stuart, I'll be interested to see what others have to say. I would have thought that the proof of the pudding is when it's actually seated in your spindle since the amount of runout will be governed partly by how well they have machined and ground their Morse taper.

Their runout spec, is that at the far end of the bar (furthest away from taper) when it's seated in the spindle? I assume that sort of test would show the worst case scenario?

Hey, since we are all prussianed up, perhaps smear some on your spindle and look at the transfer to see how well it mates up in the spindle?

Cheers,

Simon

Hi Simon,
Once it mounted in the spindle though you dont know where the run out is coming from.

They dont really say. just "Hardened and precision ground parallel to within 0.0002" Chronos Ltd Engineering Tools GIFT IDEAS 6

Well I've had it between centers on the lathe and its about 0.0003" run out, but thats with a dti. So its looking like its pretty close to being as good as they say it should be(certainly I'd say its within the noise of my measurments ATM and within the sniff test).

I'll blue it up for a look but whos to say the spindle it my lathe is correct?

Back to the shed.

Stuart

If that end you are butting it up against the cast block is not dead square to the shank when you move the rod round as you are measuring on the taper any sideways movement of the shaft will register as "runout" on the taper...

Why not put it between centres then spin it... That will achieve two things.... Tell you if the centres are in the centre of the shaft which they would be anyway as it would be ground between centres, also it will tell you if the morse taper is right... It shoul;d be as well as it should have been ground between centres..

Originally Posted by .RC.

If that end you are butting it up against the cast block is not dead square to the shank when you move the rod round as you are measuring on the taper any sideways movement of the shaft will register as "runout" on the taper...

That's true that. You can get around it by placing a single ball bearing in the centre with a dab of grease. It will be a small ball like 3/16" so it sits in the centre.

Originally Posted by Stustoys

"Centres protected against damage" Well no they aren't,

Do the ends look like this picture? With the centre in a turned depression?

http://www.chronos.ltd.uk/acatalog/info_GXee11.html

I read that spec as being 0.0002" for parallel only. That dont give you a run out spec.

Phil.

Hi Guy,
The "non MT" end is ground. but I guess that doesnt mean much.

Getting measurements at this level is tricky to put it nicely. My 0.001mm Mit Dial gauge says no runout unless its on a very short armed stand. The best I think I can say at the minute is that its less than 0.0004" run out(assuming of course my gear is close to correct).

As best I can tell the parallel is as near spot on as makes no difference(to me, at this point, I reserve the right to tighten that up later).

I'm going to have to remember that ball bearing idea Phil thanks

No the ends arent Phil.

Phil, that bed straightness scope you have. Do you happen to know what power it is and what its graduated in?

Now who did I miss?

Stuart
p.s. I should add its dirty as its half way to being wrapped up for the night

Originally Posted by Stustoys

No the ends arent

They certainly aren't safety centres. Funny how some blokes can get worlds best practice, and mere mortals like you & I just get stuck with the plane stuff.

Phil, that bed straightness scope you have. Do you happen to know what power it is and what its graduated in?

Current one is only 40x and 0.02 graduations. Marko's is 60x and 0.02.

Best one I ever had was a 100x & 0.01. Long story, short. Its still in Belguim. Consequence of a local manufacturer going into Receivership. Just as the machine was commissioned.

Phil.

I'll just have to make do.
I guess whats happened is they have just copy and paste the blurb from the smaller ones. I'll email them about it once I'm sure its as close as it should be.

That scope I bought awhile back comes off its bass, but its 20X 0.001" I wonder if I can add some power to the front.

Thanks

Stuart

Originally Posted by Stustoys

That scope I bought awhile back comes off its bass, but its 20X 0.001" I wonder if I can add some power to the front.

What are you planning on doing with it? I saw that scope when you bought it. I was going to say it looks like the good basis of an alignment scope. That next trick is finding wire.

Phil.

Well here is a quick test.
First one is as is, second with a $2 60X scope slipped inside as per third picture.

I was hoping that my lathe is shorter than a grand piano.

I think I can cut most of the plastic tube off the lens so it will go inside the scope and the piece over to the left will screw back on. I think its worth $2 to try.

Stuart

Looks like the 0.007" is the smallest piano wire on ebay. 0.009" the smallest that comes in long lengths(1157ft).
Stainless steel 0.005", Nickel chrome wire 0.004" or Tungsten wire 0.001" are other options.

Though my math says the tungsten could only hold about .36Ib and the nickel chrome only 1.19Ib.

I have 0.024" mig wire by the mile. hmmm, you're only reading the edge.... I'll have to have a look see.

Stuart

While mig wire is cheap, its also pretty tough, I wonder if that would stop it pulling truly straight?. I have a roll of thinish copper wire but I cant seem to find it, it wouldn't be as strong but it should pull straight easier... maybe.

Anyway, here is a pic of some 0.65mm(0.0255") mig wire. Comes out at about 0.077" which I think makes it about 60X graduated in 1/3 thou (0.0084mm)

Thinner wire may also help as the depth of field is less than 0.2mm, this maybe the show stopper depending how much the bed/wire sags.

Stuart

0.8mm S/S mig wire shows some promise, especially if you get the light source at the right height. It looks better than the picture, I'd say readable to 1 division. At the miunte it takes about 4 hands to hold everything were it needs to be and make adjustments.

But I have another idea lol

Stuart

Well my other idea was a laser, thats not working out so well so I will likely bin it.

Phil,
When you set up a wire do you run it from the center of the spindle to the center of the tail stock? (i'm pretty sure I've seen that writen somewhere) Its just the it would make the scope high enough to be painful to read. Having it lower would make life easier and would give the same result?
Also do you mount the scope to the carriage or your leveling jig?

I've just been looking through the pictures I have on your scope and I'd say either one was copied from the other or they were made in the same factory. Different name but all the little things seem the same.

Stuart

Originally Posted by Stustoys

When you set up a wire do you run it from the center of the spindle to the center of the tail stock? (i'm pretty sure I've seen that writen somewhere) Its just the it would make the scope high enough to be painful to read. Having it lower would make life easier and would give the same result?

I’ve done both, spindle centre line is sometimes harder, I have some little Eclipse Pin chucks that will hold the wire, if you tie a not behind the collet. You can go from the tailstock and tension the wire out the #### end of the headstock. Then you can use the tailstock adjustment side to side to get your datum’s at each end. Its also important to have the height of the wire adjustable.

You don’t want to be adjusting the focal point if you can help it. The other thing is to try and have the scope mounted vertical, so you don’t get a sin error as you move it up or down. You might have noticed, I have a large ground disc as the mount, that’s so you can clock it to vertical.

It wouldn’t matter if it wasn’t on spindle centre line, if your bed is straight, what would it matter if you have your wire strung along the front of the headstock. Straight is straight. Quite often, we wont even attach the brackets to the machine. Like on a big milling machine, I’ll round up the heavy stuff, like big angle plates, and place them each end of the machine. And set up the vee blocks and rollers on those. I’ve even dyna bolted one end to a wall.

As long as you can zero the scope at the start and the end of the bed, anything in between should be straight.

Also do you mount the scope to the carriage or your leveling jig?

Depends what I was doing. I wouldn’t pull a saddle off, unless I had to. If the machine was bare, I’d use the roller bar gizmo.

I would add, I’ve never used a wire on anything shorter than about 2 or 3 metres. Longest was 27 metres. The Waldrich Siegens at Ford Toolroom. I’d still use straight edges for short stuff.

No reason why it wont work on a shorter machine, it just more setting up.

On a short machine, I’d stick to conventional. Level and test cuts.

Level the bed, or ensure there’s no twist in the bed. That’s to ensure that when your saddle traverses the bed, it stays on the same plane. IE it doesn’t roll the tool in or out as it moves along the bed.

Test cut a bar, unsupported out of the head stock, if the headstock is adjustable, align it until you can cut a parallel bar just out of the head stock. That gets the spindle axis pointing parallel to the traverse of the saddle.

(If you a RDM kool aid drinker, twist the living suitcase out of the bed, until it turns true at two points). Thus insuring every time you put the tailstock in a different place along the bed, your centre will be in a different spot.

If not, read on, Set your tailstock by cutting a bar between centres, or the use of a ground bar that has centres. Which few of us have, so you may as well test cut.

You read it here first folks. The “three collar test” method, or “T3C” for short. If you can turn the same journal diameter at the headstock and tailstock ends, do a cut in the middle. It’s exactly the sort of thing you do, for setting up for a fixed steady. Skimming a journal.

Typically if that journal is large, you can put some of that down to deflection. If it happens to be smaller, something is horribly wrong.

Not talking you out of it, I have some good German piano wire here, you’re welcome to any amount of it.

Regards Phil.