Thread: Mars lathe crosslide scraping and taper gib

HI Ewan,
It looks like it was originally done on a shaper.
I'm with Stuart, time to make some shaper tooling

Phil

Originally Posted by Stustoys

Whats wrong with the dovetails you have again? How big are they?
I think steel is ok,,,,,,, but I've never tired it.

Stuart

Hi Stuart,

Basically, the bottom part of the compound is far from parrallel and so it either binds when fully housed or it is loose when wound out. Also the contact surface (as with all lathes like these) is somewhat lacking. Also, the top slide is high at the tool post end by about 0.04mm. I figure the easiest and quickest why to remedy that would be to purchase a 60 deg dovetail, skim all the required surfaces and spot and scrape as required ..... Oh and make a new gibb strip!

WRT the 0.04mm difference in height from one end to the other on the top slide, should it be brought flat by taking material from the top (tool post) or from the flat ways at the bottom? I'm thinking the flat ways. It's a huge amount relatively speaking, I wouldn't want to scrape that and that's why I'm thinking a skim with a fly cutter to start with?


Don't mean to hyjack your thread Ueee.

Simon

Hi Ewan,
I just used a "lathe" tool holder like much like your is one here.(though I think its offset the other way if we are going to be picky)

https://www.woodworkforums.com/f65/al...ml#post1506642

With a 5/16 HSS tool sharpened much like a parting tool.
If you take the second picture in that post swing the tool holder to the left a little, I've have thought you would be dam close.
(you might need to rotate the slide some also to get the clapper angle)
I dont have any pictures of my set up sorry.


Hi Simon,

"It's a huge amount relatively speaking, I wouldn't want to scrape that "
Young people of today, no stamina! When I was younger I knocked 0.075mm off the bottom of my cross-slide
Not exactly sure about all you are asking, but I'd say given the size of the compound slides scraping shouldn't be to time consuming.
As far as removing the 0.04mm goes(assuming I am picturing your compound correctly) I'd make the flat ways flat, fix the dovetail, then do your parallel alignment on the top.
You're going to need a slitting saw to make the new gib aren't you?(that's how I plan to make mine but as yet I haven't made one.)


Stuart

Yep, i can get the tool to reach the dovetail, with the clapper out of the way (just), but then the ram ways hit the saddle.....

I have just finished milling the bottom of the saddle parallel with the top. I used a 16mm cutter as the mill is out of tram by a tiny bit and i didn't want to create more scraping work later

I then flipped the saddle over and re milled the crosslide ways, the twist ended up being just shy of .003".
I then spotted the saddle to bed again, much better, i have contact all the way along the back now, and also spotted the cross slide flat ways, also good contact. Now to make a small scraper and i have to get myself a slip stone that will fit into the dovetails.

Hijack away Simon!

Fixed the link to the post I was talking about above. I think you'd be better off then the offset toolholder, but thats just a guess.

You're a braver man the me Ewan!

Stuart

Originally Posted by Ueee

Yep, i can get the tool to reach the dovetail, with the clapper out of the way (just), but then the ram ways hit the saddle.....

Why not either drop the table more or lay the saddle down? Looks straightforward from here...

Originally Posted by jhovel

Why not either drop the table more or lay the saddle down? Looks straightforward from here...

It does doesnt it......but it isn't. The first think i tried was laying it down and the clapper hits the saddle. I eventually managed 1 side, by extending the head right down and droping the table, but i cant do the other side. So i used a 3mm slot drill in the mill, twas very slow....

I was thinking of grinding a piece of 3/8 HSS, welding it to a handle and grinding the end, but i had a brain wave.

I have a box of 12x12mm carbide inserts for a router cutter. So i machined a piece of 20x10 MS to suit, tapped it M3 and fixed the insert on. Then i ground it to shape, took a bit of meat off the screw head and it works a treat!

Hi Ewan,
This is the sort of thing I had in mind....... but it dont matter anymore its done.

You scraper looks like it will do the job.

Now just a few hours of Chi centering scraping and you're done

Stuart

I probably could have done that Stu, but the only holders i have are for 1/2" HSS, and the thought of either milling an adapter or grinding a bit of 1/2" down was too hard.

Oh, and i don't know if i'm braver than you, just remeber i probably paid less than 10% of what you did for my lathe.

I am getting there with the flat ways, but it is in the high 30's out there now, and although the thermometer in the shed says 22 it feels way hotter.
I'm really liking the little scraper for the finishing cuts, i have found i have trouble with the 25mm wide one finding where on the edge i am cutting, but not so with the 12mm wide little one.

Firstly a big thanks to Phil T for dropping by and having a chat.

I sorted out the lathe feet this morning and got the lathe re-leveled.

Then this arvo after Phil left i started scraping the underside of the saddle to the T/S end of the bed. I'm wasn't aiming for perfection, just enough to spot the head end of the bed to see what the differences are.
The news is not so good. The V way is Ok, good contact on the front and about the bottom 1/3 at the back. But the flat way is terrible, only 2 tiny streaks next to the T/S v way and in the middle of the way.

Not sure what path to go down now.....I need the lathe back working, an i know the contact is a hell of a lot better than it was, but can i really turn may back on this? Should i maybe try to scrape the saddle to a happy medium, after all it spends far more time at the head end than the tail end?

Hi Ueee,

So if I understand, you have scraped the saddle using the HS end of the bed as a template and (due to bed wear) it shows poor contact when spotted near the HS end?

I would assume that short of reconditioning the bed (I assume that you are not even considering this as an option) then you would have to come up with a "happy medium" and either scrape the saddle somewhere in between the HS and TS, or, like you said, look at the bed where the majority of your work is done and scrape to that area as a template.

If the wear is not major, perhaps you can scrape to a point where both ends show some acceptable contact?

If you have a precision level, perhaps it would be advantageous to "map out" the bed wear along it's length using the level to get another perspective before any commitment is made?

Be interested to hear what other people have to say.....

Cheers,

Simon

Hi Ewan,
How much of the bed in that picture will be under the headstock?
With scraping the saddle Vee have you been checking for square with the cross -silde?

As for what to do next I'd say it depends on your plans. Is this going to be it or will you revisit it some day soon?

Stuart

None Stu, its a gap bed.
I think this will be it for a time, i really only did this to fix the cross, gib and backlash issues. I'm watching square as well, i really don't have the gear to do it "properly" i'm using a parallel in the 4 jaw like you did.

Simon, i could map the ways but i have no way of fixing any problems, i don't have a master big enough or a granite plate big enough to make one (yet).

The bed has been scraped at some stage, and marks can be seen most of the way along, but the job was obviously not very good. What i though was a worn low patch on the rear way (where the contact is) is actually a high spot getting worn down.