Re: Scraping Turcite or rebuilding a lathe

Hello Marcus, Allan, Raymond and others,
Its soccer time, my wife and the kids watch national championship. So I
have time to continue. Most of what i will list here comes from George
Brandau who rebuilt hundreds of Turcite bedway while I did only 3 until
now.
The biggest difference from cast to turcite bedways is that turcite is
soft and pretty compressible. Its a point you have to take in account.

A) You should use turcite only where you have enough surface area!

B) Better use turcite only on a slide that does not travel out of the
bed! If there is no other way and the slide must travel out of the bed
then: DO NOT USE LUBRICATION GROOVES ON THE PART THAT TRAVELS OUTSIDE
AND PROVIDE EXCELLENT CHIP PROTECTION AND WAY WIPERS. If you put here
grooves they will catch chips and destroy the turcite and bedway.

C)Turcite you glue with a special 2 component epoxy that cures in 10 to
24 hours.

D) Turcite has two different sides: the glue side gets wet when you put
the stripe in water. The sliding side repeals a little more the water.

E)Scratch with a hardmetal scriber point the base metal and CLEAN
PERFECTLY with solvents like thinner or special solution the faces and
the turcite.

F) make yourself some profiles of flat iron that fit into the profile
you mount the turcite onto if you have a special profile like a
dovetail.

G)Mounting: Mix well the compound in the right relation. (a mail balance
helps), spread it on both sides with a painting filler. put newspaper.
put a rubber stripe (tire tube works well). put your back up profile.
Align and clamp with c-clamps.
It is important that the sides and ends are well glued. If there is a
small failure in the imbedding oil may crawl under the turcite and it
may come up. Or it may get cached on an end.

H) With Turcite there is no inconvenience to grind it to get close to
the final measurement and more than one person will say "wherefore to
scrape" (because its compression.) But I see that because of the
clamping force of the magnet plate it is always convenient to finish
scrape to get perfect alignments.

I)Because of the compression it is difficult to get the perfect fit.
Therefore it helps to scrape mostly dry. The turcite itself marks like a
kind of mirror on the high spots.

J) On Turcite You need lubrication groves. BUT PLEASE USE ZICK ZACK
GROOVES ONLY ON THE PART THAT STAYS INSIDE THE BEDWAY!!!! Straight
grooves do not bring oil to where it is needed. (Check the lubrication
pump and lines!)

K) Best wipers are Kabelschlepp BAS18 or 25 wipers backed up with felt.

L) Dovetail guides you must pretension a little if not they stay sloppy.

M)On the longitudinal carriage don't forget to scrape the lower clamping
bedway to parrallel and the clamp guide! A longitudinal carriage that is
not properly clamped will start to vibrate. (I don't mean the fixing
clamp but the guide that doesn't permit the carriage to get lifted)

I hope this helps a little.
OK Guys the Alajuelan Liga is the new costarican champion with 4:0
against the Saints.
Good night
Sven Peter

Marcus & Eva wrote:

>
> Hi Sven:
> It is a pleasure to read your words.
> They confirm much of what I'm doing and much of what I am planning to do.
>
> I began as you say, by cleaning the machine and stoning away the burs.
> I measured the reference surfaces and recorded them, so I know where the
> components sat relative to each other before they were worked on.
> I measured the deviations from nominal for things like "not flat" and
> "twisted".
> I planned what to machine and what to scrape.
>
> Here's what I found:
> The carriage was quite twisted and rocked on the ways.
> It was impossible to find its proper position anymore and it was bad enough
> to pull the leadscrew up when the half nuts were engaged..
> It was far more than I could scrape without throwing the leadscrew out of
> position even worse.
> So I needed to build up the ways and I chose Turcite.
> Of course, I also need to re establish the correct height.
> I want to indicate the leadscrew movement when the halfnuts tighten as my
> guide.
> I will make the apron level both ways and fit the carriage to this
> reference.
> This lathe is also good because it has very wide ways and two wide flats
> that are on the same plane.
> So I can reference from these surfaces with confidence.
>
> When I mill or grind, I shim the job until it does not move under an
> indicator when I turn on the mag chuck or tighten the clamps. (Needs lots of
> indicators and sometimes the whole day just to set up)
> I was roughing away BIG errors from wear (0.006" to 0.007")
>
> When I grind, as you suggest, I use a very open wheel and flood cooling.
> I rough the batter marks away on the milling machine (less thermal stress
> than grinding) and then grind to just clean up.
> I take the casting off the machine and let it sit for a week.
> I then finish grind (0.0001" steps with relieved wheel) and blue in on the
> surface plate (it is a new plate that only I use for best precision work.)
> I then use this for my reference surface to scrape in the mating part.
> I think I get pretty good precision this way; the parts don't rock together
> more than 0.0001" to 0.0002".
>
> When I scrape in the longitudinal saddle I can use the flat ways to re
> establish level.
> I have a good way to get exactly square too.
> (I was going to put an indicator on the faceplate and swing over a roll in
> the cross slide dovetail and also on the edge of the cross slide (I've
> ground it parallel to the dovetail within 0.0002").
>
> Sven, I have to go now...work is calling.
> Thank you again for all your help
> Cheers
>
> Marcus
> ----- Original Message -----
> From: "Sven Peter" <peteryco@...>
> To: "Marcus & Eva" <implmex@...>
> Sent: Tuesday, April 30, 2002 8:07 PM
> Subject: Scraping Turcite or rebuilding a lathe
>
> > Hello Marcus,
> > Scuzzy, when there come emergencies they come all together: 5 machines
> > in 2 days, kind of nice runaroundsquirrel.
> > Late but here we go:
> >
> > Primary before you start any machining, you stone away all burrs
> > originated by hits and craters from all reference and contact faces. I
> > use diamond wet stones or boride polishing stones (grain 600 or 800)
> >
> > Marcus & Eva wrote:
> > >
> > > Hi Sven:
> > > This is actually another machine from the one I was talking about on
> the
> > > list earlier.
> > > I bought it sight unseen from a company in Ohio.
> > > It is a 1948 machine that came out of a gage making company, so it
> hasn't
> > > seen production.
> > > The ways show very little wear: the original grinding marks are visible
> > > along the entire bed length, and the indicator readings show wear of
> about
> > > 0.0006" on the cross section of the prismatic ways in the worst area.
> > A Monarch of that year with grinding marks? That sounds very strange to
> > me!
> >
> > > I have decided to leave the bed alone for now.
> > Depending on how you measured you might have later a surprise.
> >
> >
> > > The headstock bolts onto a separate mounting pad on the bed casting.
> > That gives you a little liberty at the moment you determine the geometry
> > because normally you can true these pads. (After you finished the
> > machine: plane a big plate. with a grinding post and run the indicator
> > over the hole face. Then you know exactly how much to realign the
> > head.)
> >
> > > The spindle still shows less than 0.0001" runout, so I'm leaving that
> alone
> > > for now as well.
> > Sounds good. Any noise when you listen with a steel bar against the
> > bearing points?
> > Any radial or axial play when you push it standing? Use a handle or bar.
> > (Runout means to me centre truth of the running spindle.)
> >
> > > The saddle was worn about 0.006" in the worst places, and was no longer
> > > flat; that's why I put Turcite under the saddle without regrinding the
> bed.
> > With saddle you mean the longitudinal carriage, right?
> > Here we start you must take care for:
> > height: headstock side and counterpoint side must have the same height.
> > The V you check measuring over a gauge bar.
> > total height must be that way that the apron lines up with the leadscrew
> > and advance shaft. (by the way: check well the pitch of the leadscrew on
> > the hole length and the condition of the nut and guide bushings)
> > squareness: transversal carriage and longitudinal carriage must be
> > perfectly square!
> >
> >
> > > I also remilled the cross slide dovetail, and ground the slides.
> > > (I have a decent 10 x 24 surface grinder that will hold 0.0005" flatness
> > > easily over that length.)
> > Grr... and have you any idea how much you bend the slide with it? Only
> > the magnet plate itself bends the slide a lot. It is only good for rough
> > machining. The heat bends the slide and produces a nasty peel that will
> > give you a tough time. The clamping force on the mill bends the carriage
> > enough to twist the line. So when you will be ready with scraping you
> > must adjust the height of the transversal nut to align it again with the
> > leadscrew bearings.
> >
> > (By the way: when you retouch the magnet plate every 6 month or so: be
> > sure it is sitting dead flat on the table. First time after many years
> > better grind the table surface and the bottom face of the plate too. Use
> > a very well balanced and sharp wheel and abundant refrigeration. make
> > absolutely minimum cuts: maximum 0.07mm=0.0003" if not the heat bends
> > your plate first up and later you have a hole.)
> >
> > Check the bottom plate of the centre point nearly always the are worn on
> > the front side and point downwards. check with a round gauge bar the
> > height. Take measurements and surface grind ONLY the flat part as little
> > as possible. Then SCRAPE the V. if you grind you may throw the
> > counterpoint away! You must be a super perfectionist if you are able to
> > grind the V exact. On my last counterpoint I made with the indicated
> > method my calculated control height was 67,30mm and when I felt
> > comfortable with the prussian blue marks the height was 67,29mm.
> >
> > >
> > > My experience is as a moldmaker; I have been in the business for 23
> years.
> > > I have a fully equipped machine shop, but no scraping equipment.
> > Fathers saying is: a good toolmaker master is more worth than a dozen
> > engineers.
> > Although I am a dumb engineer myself, I lurk everytime I am able to into
> > every toolmakers shop I get hold of. And learned there more then in
> > University.
> > The equipment you do not get you make yourself. (Ha... easier said then
> > done. When do you have time between the clients?) Good Scraping
> > handles I have no idea where to get them. Decent ones (but for me too
> > short and stiff) you get from Sandvik distributors. Use their grade K10
> > scraping inserts 1" or better 1 1/4" wide. (A machine is only good for
> > production and roughing. (I do not like the half moon finish for various
> > reasons))
> >
> >
> > > My only reference surface is a surface plate.
> > In how good shape is it? (I do know only one place where they rehone the
> > granite plates.) Because the granite plate is the master for your
> > rulers.
> > (have one brand new one sitting in the store room only for truing
> > rulers)
> > First work with prussian blue and later dry on the cleaned plate. You
> > get mirrors all over the rulers face and it starts to stick to the plate
> > like a gage block.
> >
> >
> > > I have a decent milling machine (Bridgeport) and a decent surface
> grinder
> > > (Kent).
> > English ?
> >
> > > I have built machinery before, but I have never rebuilt a machine.
> > > This is going to be a limited rebuild to get the machine functional
> again.
> > > I will think about having it fully rebuilt by Gallery of Machines in New
> > > York in a couple of years when the antique drive system quits.
> > > I have two other lathes, so I can lose the use of it for a while without
> > > inconvenience to me.
> > >
> > > It is interesting, even with the problems that the machine has after 60
> > > years of use, it is still a far better machine than a brand new imported
> > > machine of the same size.
> > Where I bought my mill the owner offered me his own lathe from 1927 too.
> > The shop master and and the 2 mechanics instantly protested. One
> > adjustment, one cut! Forget all the modern flimsy stuff.
> >
> > >
> > > Sven, I really appreciate your willingness to share your knowledge with
> me.
> > > Thank you very much!
> > > Cheers
> > >
> > > Marcus
> >
> > Marcus I do not share it only with you most things I try to collect and
> > write later articles. In these weeks I work on an article about
> > philosophy in maintenance. Only it is in spanish. If you are interested
> > I pass it over.
> >
> > Best wishes
> > Sven Peter