Stupid Question so please dont shout at me Bridgeport knee

I have a Bridgeport clone with a pitted knee
the horizontal slide is pitted and the saddle gets tight towards the back
the dovetail looks and feels smooth with no pits or edges
Thought I have it reground was quoted about £200 + vat
So now Im ready to do this I phone the company up to arrange booking ect
but the price Im quoted is now £360
+ vat ( I need to sit down )
now Stupid Question time
Is it possible to get a reasonable finish using the following method
using a tool post grinder mounted on linear
bearings bolted to the knee (knee removed fronm colum )
a hight and cross feed would be fitted
I have all The above Items to hand so no outlay of beer barrel tokens in
this case
I do that realise I would have to scrape the surface afterwards
Please Dont Shout at me ( oh go on then)
Reply to
Andrew Bishop
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What company did yo approach? There seems to be very few slideway grinding people around these days.
I wouldn't For a good slideway the Gibs usually have to be re-ground too.
Thats an art in itself. I think JS has refered to DIY Scraping as Scrapping ;) Which is probably quite often true!
Maybe if you talk nicely, they might just do it for cash.
I think the last time I enquired about regrinding a bridgeport it was 700 for table, saddle, and Knee. An Interact with Hard Chrome ways was 900 for a regrind with no re-chroming.
Wayne....
Reply to
Wayne Weedon
I have to ask this question, but why when things have been reground does one have to scrape after? Are we talking of high spots left by grinding and why are these left.
I have seen finished products after gringing looking almost as a mirror finish
Adrian
Reply to
Adrian Hodgson
They often don't need scraping these days. A lot if the older machines were planed and not ground. Sometimes you will see scraped flaking for oil retention or so they say, Hardinge used to do it for decoration like on Lathe Apron faces!
When cnc and some manual machines are rebuilt often one face is turcited and this does need scraping to give a flat surface, as it's bonded on.
There used to be a slideway grinders down here in Dorset Run by a Phil Goodall. He's either retired or expired now, and I'd have little faith in the outfit now, if they are still going. I did look in there after he sold the business and was not left with the right impression. Even when Phil did a friends Bridgeport the table had to be done twice. Was good in the end.
Wayne....
Reply to
Wayne Weedon
reground does
machines
turcited
Phil did my Colchester Master a few years back,and when I went to inspect it I could feel the discrepancy on the bed between the main casting and the gap piece ! Showed up on a test turn as well. In fairness he sorted it - he'd removed the gap piece and when he put it back there was a bit of crud under it, when removed and cleaned after grinding it left a step (of course). I do wish when he offered to re-paint the machine he hadn't used suds soluble paint - my coolant is permenently Colchester Green !
He sold the business to another who is still trading. There is another company (well couple of blokes actually) 'Mick & Charley' in Verney Road off the Old Kent Road - they did my previous two Colchester Students and my Bridgeport. Excellent work but rather expensive.
AWEM
Reply to
Andrew Mawson
Douglass machine tools not expensive for the work involved but out of my budget at this time
Reply to
Andrew Bishop
Think by rescrape after he means putting oil retaining abilities back in ... zig-zag arrow paterns... frosting for oil retention.
all the best.mark
Reply to
mark
£360 seems like quite a reasonable price, given that dovetails are involved. Was this just the knee or was it for the table as well? What about the knee/column ways? If the price was just for the knee, are you planning to re-scrape the table ways to fit the knee ways?
Scraping the gibs to match the slideway is one of the easier operations.
If you do the job properly, have good (bought or made) master straight edges and templates and aren't afraid to take a lot of time, then scraping will do as good or better job than grinding. If you have the surface ground you will still need to do flaking if you don't want the table to stick to the knee (if the grinding is any good, that is). DIY grinding can do damage far more quickly than DIY scraping!
Reply to
Mark Rand
Significant question before your hand goes too far into your pocket... Are the pits just that. I.e. pits that may serve as oil reservoirs on an otherwise good surface or are they pits on a surface that is/was rusty all over? If the former, then ignore them. If the latter then continue with the dipping of hands in pockets.
Also If the saddle gets tight towards the back, just how much are you talking about. The difference between no play at the front and tight at the back may be a tenth of a thou and might be taken out in less than five minutes with an oilstone.
Not shouting, asking reasonably :-)
Mark Rand RTFM
Reply to
Mark Rand
It dates back to old technology. A bit like flint knapping and getting the stones to fit on the pyramids.
Lets be honest most of the old machine tools were made on even older machine tools and there were errors. The easiest way to correct these given cheap labour and Woodbines only being nine pence for ten, was to scrape the two surfaces in.
Now modern times the purists say it's to create small depressions in the ways to retain oil. No one ever mentions retaining crud.
Modern day technology and machine tools can grind to microns, surface finish to a glossy gnats bollock and retain a continuous surface film of lubricant better than anything Durex or snot can achieve.
If scraping was the answer then pray explain why on high precision articles where cost is no object do we not bother to scrape but accept the surface finish straight off a precision grinder ?
Modern machine tools run on hardened and ground linear rails - not scraped, they contain oodles of bearings of all description, - also not scraped. So if our modern machine tool using literally hundreds of bearings and a few precision slides don't need scraping why do we have to go back to the days of flattening a machined surface with the back of a shovel ??
-- Regards,
John Stevenson Nottingham, England.
Visit the new Model Engineering adverts page at:-
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Reply to
John Stevenson
Don't know the answer to your question but assuming that the somewhat unrealiable deadlines of Mr Morgan ever get met this book might be worth reading:
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I've got his scraping book and it's very clear (much better than Connolly).
Charles
Reply to
Charles Ping
that was for the top of knee a inc top dovetail and I would be scrapping the saddle to fit Its not expensive I agree just more than I can justify to myself or wife
Reply to
Andrew Bishop
Scrapping? Hehe. What did I say ;)
I think the prices I was quoted sometime ago was from a Company called Unislide in Nuneaton. Have no idea what their work is like.
Wayne....
Reply to
Wayne Weedon

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