Thread: Mars lathe crosslide scraping and taper gib

Hi Ewan

you are the go to man ..do you want to repair any of my lathes

I assume the original, cross slide gib was the straight type ? And, you have changed it to a tapered type . Did you choose 1/48 for any reason

BTW thats you pointing at me , laughing

Hi Ewan,
Looking good so far.
Are you going to use one or two screws?

I've just started back on my crossslide. Fitted wipers and made a tool for machining "Olympic rings".
Checking it all still spots ok tomorrow with any luck. Then I'll be making a new gib just like you.

Stuart

Originally Posted by morrisman

Hi Ewan

you are the go to man ..do you want to repair any of my lathes

I assume the original, cross slide gib was the straight type ? And, you have changed it to a tapered type . Did you choose 1/48 for any reason

BTW thats you pointing at me , laughing

Happy to come and help with any repair work Mike......on the condition you explain to SWMBO where i am.....
Yes i'm going from a rather thin (1/8") straight gib to a tapered one. The 1/48 is the standard for imperial taper pins and gibs, it is referred to as 1/4" per foot a lot. Although my machine has metric screws it is imperial everywhere else, so i'm in imp mode (just for Phil and Bruce) (plus my best DTI is imp)

Originally Posted by Stustoys

Hi Ewan,
Looking good so far.
Are you going to use one or two screws?

I've just started back on my crossslide. Fitted wipers and made a tool for machining "Olympic rings".
Checking it all still spots ok tomorrow with any luck. Then I'll be making a new gib just like you.

Stuart

I think only 1 Stuart, but it will be a stud with a pair of nuts and a tag on the end of the gib, drilled to suit the stud (does that make sense?) Only because of the lack of meat i have to play with, i cant go making the skinny end of the gib to thick, and am worried about slotting it. Once i have it made though i'll decide. I would rather go 2 so i can put wipers on like you are.
I will also add a lock to the slide, im thinking just a brass puck, dovetailed on one side and tapped for a screw so it can be pulled up pushing the gib across.

Hope the temp doesn't play havoc with your spotting, didn't you scrape most of it in winter?

Olympic rings???? That was sooooo last year (or it will be in 27 mins!)

HAPPY NEW YEAR TO ALL!

Originally Posted by Ueee

I think only 1 Stuart, but it will be a stud with a pair of nuts and a tag on the end of the gib, drilled to suit the stud (does that make sense?) Only because of the lack of meat i have to play with, i cant go making the skinny end of the gib to thick, and am worried about slotting it. Once i have it made though i'll decide. I would rather go 2 so i can put wipers on like you are.

The screw head on the thin end of mine only just catches one corner(though I believe the words used by Phil were "worst gib I've ever seen")

Originally Posted by Ueee

I will also add a lock to the slide, im thinking just a brass puck, dovetailed on one side and tapped for a screw so it can be pulled up pushing the gib across.

Something else I've forgotten to think about.

Originally Posted by Ueee

Hope the temp doesn't play havoc with your spotting, didn't you scrape most of it in winter?

I'll be grumpy if its bowed 0.003" the other way lol(it still feels pretty good so I dont think it will be to bad, fingers crosssed)

Originally Posted by Ueee

Olympic rings???? That was sooooo last year (or it will be in 27 mins!)

I think thats what Phil calls them....... though I've been wrong before.

Happy New Year

Stuart

Hi Ueee,
Rework and mod is looking good , NOW ya better get it done quick seein as ou you have a big mill coming.

The better half probably saying "Ueee, WHAT HAVE YOU DONE?"



Cheers.

Hi Ueee,

Good work thus far, as i would expect!

I have a couple of questions if I may....

WRT the taper on the slide, Is that just done by offsetting the cross slide in the mill by the taper amount (measuring the 1/48 with a DI) and then re-milling with the dove tail mill?

Once you have completed the gibb and the taper on the cross slide, are planning on hand scrapping the dovetails and gibb?

I'm interested because I'm slowly getting fed up with my ill-fitting compound on my lathe. In the past I have just put up with it, kept it fully housed (for strength and rigity) whenever I could. But now that my confidence and skills are increasing, I'm finding the urge and gravitational pull to either rebuild it or completely build a new one. Hand scraping the flats is neither here nor there but the dovetails would present me with problems. My main problem is that the bottom ways are not parrallel and they bind. I don't think I'm Robbinson Curruso with this problem!

Anyway, if care is taken with machining the dovetails, can you get away without scraping them?

I shall be watching your thread with much interest.

Cheers,

Simon

Originally Posted by Log

Hi Ueee,
Rework and mod is looking good , NOW ya better get it done quick seein as ou you have a big mill coming.

The better half probably saying "Ueee, WHAT HAVE YOU DONE?"



Cheers.

I told her how much it was and she said(and i hope your sitting down for this) "you had better get it"....... At 2450kg its the transport that will cost, at least it will need a truck and hiab for an hour or 2 anyway

Originally Posted by simonl

Hi Ueee,

Good work thus far, as i would expect!

I have a couple of questions if I may....

WRT the taper on the slide, Is that just done by offsetting the cross slide in the mill by the taper amount (measuring the 1/48 with a DI) and then re-milling with the dove tail mill?

Once you have completed the gibb and the taper on the cross slide, are planning on hand scrapping the dovetails and gibb?

Anyway, if care is taken with machining the dovetails, can you get away without scraping them?

I shall be watching your thread with much interest.

Cheers,

Simon

Hi Simon,
I set the cross slide angle on the mill table with the sine bar and DTI but it could just as easily be done with just an indicator. I then roughed off the angle, and cut the dovetail.
I will scrape all the surfaces, and although i think you could get away with a straight gib with no scraping to fit a taper gib i can't see any other way than to scrape.
I think Ben's new extended cross slide was just machined, i'm sure Himself or Peter could tell you.

This may be some use, the last post


Making a new parallelogram, tapered gib for my PM-45

I have now scraped the twist out of the bottom of the slide, just need to finish it to "10-15" PPI as it says in MTR (it arrived on xmas eve, great book, full of lots of "light" reading)
However it is now clear that the top of the slide is all over the place, it is also twisted and has a "big" hump in the middle. The biggest problem with fixing it is the graduated ally ring, i will put some heat on it and fingers crossed it will just be held in with locktight and it will fall out.

Arrrrrrgh!
Well i now have a nice bearing on the cross slide. I tried to set the shaper up with a parting tool to cut some relief grooves in the base of the dovetail's.....cant do it....don't own a single slitting saw either! Even if i buy one i don't have a lathe to make a mandrel on, unless it has a 22mm bore like the gear cutters.
It gets worse.....the saddle is twisted in the opposing direction to the slide, so the rock was compounded. it also means the back right of the saddle has no bearing on the ways. I have blued the saddle off the very RH end of the ways, the contact is awful. I also checked the saddle ways off the T/S ways, there is about a .1mm dip at the head end, both front and back. What gets me is there is still scrape marks on the rear flat way. Not a good job obviously! (although the t/s ways could be humped...i doubt it) The thought has occurred that i have just bought a mill big enough and probably solid enough to mill the ways......
The last thing is trying to scrape the bottom of the cross slide ways. There is no room, i need to make a very narrow scraper.
Anyone know a source of carbide for scraper blades (i might just braze an old insert onto a bar?)

Pic of the contact on the ways, yes there is a patch in the cast at the rear always been there.

It seems like only yesterday that Stuart started a similar thread with his cross slide scraping and the massive can of worms that was to follow!

Keep going Ueee, I'm right behind you....

I was out in the shed today and one thing I checked was whether my hand scraper reaches to the end of the dovetails. It appears that my dovetails have a generous relief cut that allows the usual 90/60mm carbide scraper blade right to the end. It would be a PITA but doable.

I'm thinking of biting the bullet and buying a 60 deg dovetail end mill and re-cutting the dovetails on the compound, using the same end mill to make a dovetail master/straight edge and new gibb and spotting it all to a nice fit. Bit scared though! It may seem silly but making one from scratch seems easier and if I stuff it up I still have what I started with!

Can you make a dovetail master/template out of mild steel?

Simon

"Down the Rabit hole" join me wont you? lol

Hi Ewan,

Why cant you use the shaper for the relief groove? Upi have an old power hacksaw blade?

You say the back right of the saddle has no bearing but if I'm looking at the picture correctly is the back left? what side it the patch on? Whats the blue at the top of the picture?

I'm not sure you will improve things with a mill.

Hi Simon,

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

Stuart

Yep, so far down the hole i cant tell my left from right.....time for a tea party?

The back LEFT of the saddle has no bearing, the other blue you can see is an ice cream container lid.

I had in my mind to set the mill up like planner....depends on the wear on the mill though. I'm tempted to completely re-machine all the bearing surfaces on the saddle, it is thicker at the back too (underside to the cross ways), by about 12thou from memory, so i can't use the 2 flats on the bed ways as my datum point and follow it through to the cross slide.

No power hacksaw blades, i tried with the shaper with the saddle both vertical and horizontal, but the clapper gets in the way even with the tool hanging right out. One of the downsides of such a big machine i guess. I'll get a 2mm slitting saw with my NT40 tooling order.

Definitely time to join the mad hatter!

Originally Posted by Ueee

the other blue you can see is an ice cream container lid.

lol so it is.... my super power is failing me.

Originally Posted by Ueee

i tried with the shaper with the saddle both vertical and horizontal, but the clapper gets in the way even with the tool hanging right out. One of the downsides of such a big machine i guess. I'll get a 2mm slitting saw with my NT40 tooling order.

You only have the tool holder with the angled head?

Maybe its time to make a specail tool holder

Stuart