SB 9 Rebuild

[steamer]

Hey Mosey...here ya go.



In the headstock, is the test bar.   It is a precision ground bar with a 3MT shank and a straight diameter.  It is 9 inches long.

The object of the excersize is to have the end of the test bar pointing up and towards the front of the lathe by .0005"/12"

With a 9" test bar....thats .0003" up and too the front....which as close as I can measure is what I have right now.

A point of procedure here.   To use the test bar...which has some run out at 9" as you can imagine (about .001" total), you rotate the spindle until you see the high point and the low point of the run out.   Then rotate the spindle until you split the high and low.  That is where you take your readings..without moving spindle.   That's the ONLY way to get repeatable readings.

I got the 3MT test bar and a 2MT test bar for the tailstock from RDG tools LTD...so my long lost Brit cousins don't have to go very far to get these items.

The tailstock has a similar requirement, and to match the HS spindle height from 0 to +.002.   

The Check of the height is to take one of these test bars...doesn't matter which, and mount it between centers, and then run a dial indicator along the top.   The bar should go uphill by .002" max at the tailstock.

I've started the Tailstock...I'm scraping the base to match the way pretty well...I've attached a photo of in progress.  Seems taking the photo with out the flash shows the marking better....still a little bit to do there.


Dave

[Mosey]

Wow, Dave, love them pictures!!

Love your work.

[steamer]

Thanks Mosey...
More tomorrow.......Ill shoot to get the TS done.

Dave

[Don1966]

Ooooooh! That is looking great Dave. What about the height of the tail stock to the headstock? Is this what you are scraping in? I know you are trying to get the tail stock level also.

Don

[steamer]

All the TS tasks....i hope
Ts clamp
based scraped to the ways
Base milled level and high
Scrape in the ts to height and alignment

That is a full days work!.....well see if can get that much time in the shop

Dave

[Don1966]

OK Dave, I just ordered me a test bar. I need to know what is happening to my lathe. You persistence has me wanting to get mine right. And dog gone!I really don't know what I am doing, but I will try.

Don

[steamer]

Don

Check your PM...getting a lathe without twist is the KEY to getting a straight non tapered shaft.

Your lathe appears to be in good shape , and I really think it just needs a proper leveling...and at a mimimum...that is the first place to start.

Dave

[steamer]

And just to be clear...I absolutely think that modifications to a lathe should be the last thing you do if it's not performing well unless you exhaust all other avenues and have positively identified the source of the problem

....REALLY!

My SB was given to me...and it was completely clapped out but still had "good bones"......so I had nothing to loose by rebuilding it.

If I screwed up....I screwed up...I'm not out anything. My Logan is right there next to it.

I'm pleased with my progress...though I wish it had gone a bit faster...it was a real learning experience.

If you want to make your lathe run better....make sure you take the twist out of it and level it carefully with a good ACCURATE level.

Start there.  If it still doesn't behave....be the detective...and keep searching for the truth...but don't cut anything...

Dave

[steamer]

OK

This morning I finished scraping the bottom of the TS base to the bed.   Got nice bearing...remember this is a NEW base...that I machined for the solid to replace the one that was .018" low from wear.    I had stock on this one and I needed to know how much needs to come off.

Here's the set up I was speaking about yesterday.


I put an indicator on the cross slide and zero'd it over the top of the bar which is held between centers.
I moved the cross slide back and forth until I got a maximum reading. 



Now without moving the cross slide, slide the whole saddle towards the TS and note the difference in height, note it is about 21 thou high at the tailstock.


NOW ask yourself the question....is the bar parallel to the bed?.....I don't know....but lets find out.    I know the bar is round and straight.
Very carefully, move the cross slide in and out and note the position of the maxima.  Did the maxima reading get bigger?....OK now leave the cross slide at the maxima, and move the whole saddle back to the HS side where zero was.    Did the indicator come back to zero?....if the bar is parallel to the lathe...it should.    Im my case it did.

Next I took the tailstock off the base ,and noted how parallel the top of the base was to the ways.  Its about .002 until it gets to a step on the front side where it jumps another .002 for a total of about .004

NOW I need to measure how square the mortise is to the axis of the ways.   It should be good...but we know what happens with good intentions!   If it needs to be squared up, my only approach is to turn it at the Vways.

Once I confirm the mortise is square to the bed ways, , I'll set up on the F1 to take most of the excess stock off....and then scrape the rest in.

Dave

[steamer]

And Steve!

The tumbler gears on a SB come off VERY easy...the only thing holding them in is the index latch on mine, and the one (1) bolt on yours

For indexing I was going to use the spindle gear...but it's a bit worn and small in diameter...It's fine for cutting threads and such, but is a bit worn for indexing.  But If you take the tumbler assembly off...about 3 seconds on my lathe...You can put an index ring of substantial size on the back of the spindle with what ever index you want....I'm going to use a ring  with radial holes.  I have an extra dividing head index latch that I'll press into service, and mount it on the post at the rear spindle bearing.

Dave

[Don1966]

Dave, question! I see you are using a live center on the tail stock with your test bar. I thought you were suppose to use you fixed center? Wouldn't you pick up errors with this?

Don

[steamer]

Well you'd think Don....when I rotated the bar in the center..the runout error is less than .0002"...so it runs pretty well

The standard is 0-.002" high...so I think I can live with the error....but technically you are correct!

At the moment...I don't even have a MT2 Dead Center!   

All my lathe tooling is Logan...and is MT3 in the Tailstock.....it's on the shopping list........but I'm going carbide so I'm saving my sheckles....

Dave

[Don1966]

OK, so the standard is .002 high, does this mean the headstock is higher or the tail stock is higher?


Don

[steamer]

The standard it 0.000 to 0.002"  high at the tailstock end.   this is standard Engine lathe specifications

A "Toolmakers lathe" ...generally a tighter specification...the lathe is held to 0.00 to 0.001" high at the tailstock end.

And don't get too wound up about it either....it seems lathes run just fine down to about .005" low on the TS end....

But NOT .018"!

IF your fitting a NEW tailstock though...which essentially I am....you should chase the standard.

Dave

[steamer]

Don I have a blank SouthBend lathe Test card.   It lists all the alignment requirements.

I'll scan it sometime today...gotta bring my Son to the doctors first....Pesky cold virus is kicking his butt....

Dave