Lathe bed in need of trueing up!!...

[johnbaz]

Hi all

My old Sheffield made Faircut lathe has wear on the dovetailed bed close to the headstock, it needs an overhaul and years ago i worked in a machine shop (Sanderson Kayser), whe the bearing surfaces were in need of attention, there was a group of blokes that came and scraped them level and true again, does anyone know of such a company that still does this??

Failing that, can anyone say what i would search for?? (dunno what their job title/ company name etc) was

Even looking through the yellow pages, i wouldn't know what the service would be called (damn i hate being thick   )


Cheers, John

[Bluechip]

Hi John

Just done a search on Bing ( UK sites ) for slideway grinding.

Lots of sites ... probably not cheap   

No help am I ??

But I think that's maybe what you need to look at.

Dave BC

[johnbaz]

Thanks dave

I didn't have a clue what to look for

It's only just occured to me to go over to our machine shop and ask in there, they should know where to get them seen to!!


Cheers, John

[bry1975]

We use to always use Shaw and Goodwin at East Goscote, Leicester for precision grinding sadly they've shut down or moved!

[johnbaz]

Unfortunately it's the way of the world Bry

From what i recall (it was over thirty years ago), they didn't grind the beds but rather, scraped them with special scrapers, some were made from files, they had the teeth ground off and the edges were ground back, when they had finished, the beds were perfect again and the pattern looked like feathers laid out on the bed...

Immensly skillful!!


John

[Lew_Merrick_PE]

Franklin Jones, the original author of Machinery's Handbook also wrote (among many others) a text on the scraping of ways.  It does not leap into my hands (and about 40% of my library is still in boxes, so it may be extremely buried), but I remember the title as being something to the effect of precision machine and tool maintenance.  Just about any of the texts Frank Jones or Frank Colvin wrote are worth having to hand.

Does that help at all?

I have scraped numerous ways in over the years.  It takes a good reference flat (I have been using monochromatic light and a 1/8 wave optical flat) and a lot of patience.  The true "key" is patience.

[Trion]

Scraping seems to be a lost art. But you can find much useful info if you are willing to take on the task yourself.

Connoley has written a large book on machine reconditioning, covering scraping. There are also quite a few posts on other forums regarding scraping, where people are sharing their experiences regarding both tools and methods. I aspecially like this one on cnczone http://www.cnczone.com/forums/general_metal_working_machines/95594-my_scraping_education.html
YouTube also has a few useful movies.

Good luck

[one_rod]

Hi John. Didn't know you were a member here.....

Hand scraping in not quite a lost art, yet. There are still a few of us old fogeys who can do it.

I honestly would not want to take on anything as time-consuming as a lathe bed these days. Seems that my attention span decreases as my age increases.

If you seriously do want it doing I can give you the phone number of a chap. You might want to be sitting down when you hear how much he charges.......

and the pattern looked like feathers laid out on the bed... 

It's known as "frosting" and the evenness and regularity of the pattern is taken as an indication of the skill of the man doing the work. Even these days there is no better method for getting an accurate sliding fit between two metal parts.



one_rod.

[bry1975]

Haven't done hand scraping since I finished first year at college, certainly an interesting skill once done but very slow and tedious.

[johnbaz]

Hi John. Didn't know you were a member here.....

Hand scraping in not quite a lost art, yet. There are still a few of us old fogeys who can do it.

I honestly would not want to take on anything as time-consuming as a lathe bed these days. Seems that my attention span decreases as my age increases.

If you seriously do want it doing I can give you the phone number of a chap. You might want to be sitting down when you hear how much he charges.......

and the pattern looked like feathers laid out on the bed... 

It's known as "frosting" and the evenness and regularity of the pattern is taken as an indication of the skill of the man doing the work. Even these days there is no better method for getting an accurate sliding fit between two metal parts.



one_rod.

Hello Rod

I only found this smashing place a couple of days ago!! (it's just so interesting!!)

I'll have to start saving me pennies up then if the levelling is so expensive to have done

I had thought of having it milled as i presume this would be how they were done from new, we have a machine shop at our place but the lathes are about 90feet long dunno if they could do something as small as my lathe bed



Cheers, John

[bry1975]

Good read here:-

http://www.practicalmachinist.com/vb/general/hand-scraping-dixi-jig-mills-186035/

90foot long hell our back gardens only 100foot!

[one_rod]

I had thought of having it milled as i presume this would be how they were done from new, we have a machine shop at our place but the lathes are about 90feet long dunno if they could do something as small as my lathe bed



Cheers, John

Traditionally, good quality lathe beds would be planed, and then hand scraped, never milled. This was considered the only way to ensure sufficient accuracy, even on a small lathe.
Nowadays, most far-eastern machines are finished on CNC surface grinders. Fast, economical and perfectly good enough for most purposes.  I think Myford still scrape their beds in by hand. A fact that's reflected in their prices. 

There are firms that will surface grind a lathe bed for you. Depending on how much damage or innacuracy you need removed, this can involve removing quite a bit of metal. If the headstock sits on the ground bedways, (like Boxford, Southbend etc) then it's no problem. If not then you will have to shim up the tailstock to maintain the centre height alignment.



one_rod.

[RichardShute]

does anyone know of such a company that still does this??


Cheers, John

Hello John,
I can thoroughly recommend Brian Caddy at Slideway Services (http://www.slidewayservices.co.uk/) in Nuneaton. He reground my lathe bed and it is almost certainly better than new and he's a very decent guy as well. I also know of CMT in Colchester (http://www.douglascurtis.co.uk/dcmt.htm) who I have been told are good, but I've not used them myself.

I just looked up your lathe on Tony Griffiths site and while I'm sure the guys above could sort it, for a machine as small as that, I expect you could find a more local precision grinder who could do the job. A flat top and two dovetails should be well within the scope of a reasonable surface grinder.
Richard

[johnbaz]

does anyone know of such a company that still does this??


Cheers, John

Hello John,
I can thoroughly recommend Brian Caddy at Slideway Services (http://www.slidewayservices.co.uk/) in Nuneaton. He reground my lathe bed and it is almost certainly better than new and he's a very decent guy as well. I also know of CMT in Colchester (http://www.douglascurtis.co.uk/dcmt.htm) who I have been told are good, but I've not used them myself.

I just looked up your lathe on Tony Griffiths site and while I'm sure the guys above could sort it, for a machine as small as that, I expect you could find a more local precision grinder who could do the job. A flat top and two dovetails should be well within the scope of a reasonable surface grinder.
Richard

Ahhh Thanks Richard

Yes it's quite a small machine and really needs doing (all my parallel turning comes out ever so slightly tapered


Cheers, John

[MrFluffy]

Not to teach granny to suck eggs, but are you sure its bed wear causing it?
Theres loads of potential causes for taper cutting and Ive seen old significantly worn machines that could still turn out parallel work. Someone will be along shortly with links to rollie's dad's method of alignment checking and other ideas Im sure

[johnbaz]

Hi MrFluffy

When i adjust the shims of the carriage whilst it's close to the chuck, it won't reverse very far before it stops, similarly, if i adjust them whilst it's at the dead end it will go forwards but the at the chuck, it's very sloppy 

I'm fairly sure it has wear in front of the headstock as this is where most of the work is done...


Cheers, John