Thread: Scraping Projects

I have been scraping in the headstock on the 10EE lathe..

For someone like myself of limited experience it is pretty tricky and made even more tricky by scraping when you should be sleeping and thus you scrape on the wrong side trying to bring the spindle parallel in the vertical plane with the ways...

Then you also have to take into consideration the test bar sag.. In my case a 1 1/2" diamer bar 12 inches long will sag 0.0006"... Which is greater then the allowed tolerance which according to schlensinger is a rise of 0 to 0.01mm over 300mm

Then you also have to get the pads all sitting level.... When the headstock weighs in at maybe 70kg, it is hard to detect when this is happening just by spotting marks alone... So I am going by feel and a dial indicator measuring sideways movement which should be 0 is all pads are bearing weight..

I am finding lots of pitfalls, usually after I have fallen into them...

Would it be worth hollowing out the test bar..if its not too hard? Or does that just take the known sag away so you have an unknown sag?

What gets me is how can you align to the bed in the vertical plane if the bar is sagging? I guess it is such a small amount out that it would not be measurable.

Um..... .0006" sag, .750 rad, hypotenuse is..... .750024. yep, immeasurable (unless your Ray and Josh)

Nice work, i'll have to go through this with the leblond, with a head a damn sight more than 70kg.

Good luck!

Ew

Originally Posted by Ueee

Would it be worth hollowing out the test bar..if its not too hard? Or does that just take the know sag away so you have an unknown sag?

What gets me is how can you align to the bed in the vertical plane if the bar is sagging? I guess it is such a small amount out that it would not be measurable.

Um..... .0006" sag, .750 rad, hypotenuse is..... .750024. yep, immeasurable (unless your Ray and Josh)

Nice work, i'll have to go through this with the leblond, with a head a damn sight more than 70kg.

Good luck!

Ew

I have not tried putting the interferometer on the lathe, seems a bit pointless on chinese iron, but the attachments are there, the instruction look fiddly much like the straightness of travel on the mill.

-J

Originally Posted by Ueee

Would it be worth hollowing out the test bar..if its not too hard? Or does that just take the known sag away so you have an unknown sag?

What gets me is how can you align to the bed in the vertical plane if the bar is sagging? I guess it is such a small amount out that it would not be measurable.

Um..... .0006" sag, .750 rad, hypotenuse is..... .750024. yep, immeasurable (unless your Ray and Josh)

Nice work, i'll have to go through this with the leblond, with a head a damn sight more than 70kg.

Good luck!

Ew

the sag comes back to about 0.015mm.... That is fairly easily measurable with a DTI.... If the test bar is parallel, you only need to measure two points, either ends.. As the ways are freshly ground and the tailstock is scraped to their ways pretty well, it is just a simple job of attaching the dti to the tailstock base and running it up and down the test bar after spinning the bar to find the middle runout spot at the line you are running the dti along....

The formula to calculate the sag is in the attached picture...

I am using a overhead hoist to lift it on and off, and the tolerances I am working with would be a lot finer then you would work with the le blond.. by a significant margin..

The general lathe specs of schlesinger are headstock alignment in vertical is 0-0.02mm per 300mm and the same for the horizontal

For tool room lathes the specs are vertical 0-0.01mm per 300mm rising towards the free end and horizontal 0-0.005mm per 300mm towards the tool pressure.

With the headstock sitting without being bolted down I was reading the headstock sitting high by 0.0001" (I was using my imperial DTI)

And it was 0.0001" inclined towards the tool in the horizontal plane...

When I tightened the bolts up the vertical stayed the same, but the horizontal moved 0.0003" away.. So tomorrow evening I will have to fix that up.... I am hoping one or two scraping passes will go close to fixing it...

But I will also say this... You have to be impressed with people that rebuild machine tools fully...No doubt it gets easier the more you do, but you have to be dedicated because it can be a huge undertaking.... Especially when you have to start making custom parts..

Thanks for the sag formula.
You are working to twice what i "should" need to, the limiting factor for me will be the temp variation we get here. I guess your temp is pretty consistent at this time of year, we are getting mid 20's in the day and lows of under 5.
That would be the only thing a pro would have over any of us, temp controlled working place.

I have not considered temperature as having a bearing on what I am doing... Maybe it does have an effect, I do not know...

Here is the finished article.. Don't put too much into the dti readings, the bar is not perfect, it is only lathe turned, but I think it is very close...

Need say a laser interferometer to do a proper measuring job on it

Although the micrometers and with my chinese V blocks on the granite plate says it is pretty good... Although how good the V blocks are is another variable...

Something like this would make those scraping projects go a bit faster

Marcels Maschinen - Photo

Originally Posted by .RC.

Then you also have to take into consideration the test bar sag.. In my case a 1 1/2" diamer bar 12 inches long will sag 0.0006"...

And the above is dead wrong.... I stuffed up my calculations...

But all good now...Headstock is bolted down and finished...