Inspection-Guide-lathe-buy.pdf

Pre-owned Lathes

A Guide to Inspecting

before you Buy

Pre-owned

Lathes

A guide to Inspecting

before you Buy

Myford have been building Lathes

since 1934, during our most productive

period our output was about 500 lathes a

month and to our knowledge most of these

Lathes are somewhere around the globe,

many still working hard for their owners.

The fate of old Lathes depends on how

hard they have worked and how well

they’ve been treated; some are broken

for spares, others are sold on the used

machinery markets. Some come back to us

for Rebuilding and returning to full service.

This Guide is an inside view of how and

where our Lathes wear and what we do to

reinstate their working accuracies.

Myford Lathes that have worked hard will

have wear in differing areas depending

upon their history. So during inspection one

or more faults will be detected.

This Guide takes you through this inspection

process and explains how wear is detected

and accuracy reinstated. We start with

the Headstock of a Myford Super 7, the

footnotes explain Rebuild procedures and

the differences across the model range.

But irst run the Lathe...

Run the Lathe

Wherever possible run the Lathe under power.

Check that the Lathe will run comfortably at both

its highest speed in the open drive range and its

lowest speed in the back geared range.

If the machine is itted with a countershaft clutch

check that this engages smoothly, there is no

slippage and that there are no alarming noises.

Pay particular attention to the countershaft clutch

unit on early Super 7 Lathes, manufactured up to

The Headstock Spindle

Visually inspect both the bull wheel on the

headstock spindle (mandrel) and the back-gear

cluster for broken teeth. Check the condition of

the pulley and the bronze gear that forms part

of the back gear mechanism. Check that the rear

angular contact bearings have not had grease

pumped into them as it will mean dismantling

and de-greasing. All the lubrication nipples on

Myford Headstocks are for oil with the exception

of the two nipples on Series 10 Lathes itted with

taper roller bearings which should be greased.

June 1958 S/N SK8128. The clutch is an expanding

sleeve operating in the 4 step countershaft pulley.

At times they proved temperamental in service

and spares are now dificult. It is not a straight

forward job to it the current clutch.

Check that the main drive belt between the

countershaft and headstock spindle is in good

condition. Belt replacement involves dismantling

the headstock on all but 254 Lathes.

Myford 254S and Plus Headstocks

We run the headstock prior to

dismantling the lathe to check for

bearing wear and undue noise and if

required replace. Flush the headstock to clean and reit

the headstock to the bed, reset pre-load on taper roller

bearings. Replace cone pulley clamp washers, check

headstock for alignment and if required correct.

Myford ML10 Plain Bearing Headstock

We reit headstock to bed. Check

spindle in bearings for running

clearance if excessive wear it

replacement spindle. Reit spindle assembly with new

vee belt and thrust race. Adjust end collar to give

correct loading on thrust race and correct axial loat to

the spindle. Check headstock for alignment.

Now you will need a 0.0001” (0.002mm)

Dial Test Indicator with magnetic stand set to

read off the spindle register face (see photo)

Release the belt tension from the countershaft

to headstock spindle and revolve the spindle

gently by hand. You would expect to see a

reading of between 0.0003” and 0.0004”

(0.008 and 0.01mm) Anything greater

indicates that attention is necessary.

Myford ML10, Speed 10 and

Diamond 10 Headstocks

We reit headstock to bed, wash

excessive grease from the bearings,

check for bearing wear and if

required replace. Reit the spindle assembly complete

with new vee belt to the headstock, adjust the end

collar to give correct pre-load on the taper roller

bearings, check headstock for alignment.

Procedures used in Factory Rebuilding

ML7 Headstocks

We reassemble the headstock to

the bed. Re-scrape the headstock

bearing to the spindle. Reit the

spindle assembly complete with new vee belt to the

headstock. Re-shim the headstock bearing caps for

correct running clearance. Adjust end collar to give

correct loading on thrust race and correct axial loat

to the spindle. Check and correct, if necessary, the

spindle alignments.

Myford Super 7 and ML7-R Headstocks

We re-scrape headstock front

bearing to spindle and reit

headstock to the bed. Fit a new pair

of angular contact bearings to the rear of headstock.

Reit the spindle assembly complete with new vee

belt and wick to the headstock. Adjust the end collar

to give correct pre-load on the angular bearings and

make axial adjustment to the spindle to give correct

running clearance at the front bearing. Check the

spindle alignments and correct if necessary.

The Lathe Bed and Saddle

Along with the Headstock these are the

key components that form the basic structure

of the Lathe. First make a visual inspection

concentrating on the area to the right of the gap.

If the bed has indentations, hack saw marks and

generally looks untidy it will indicate hard use.

There are two types of bed for the Series 7 Lathes.

The earlier bed, referred to as a narrow guide bed

was discontinued in 1972 at S/N K107657 for ML7

Lathes and S/N SK108891B for Super 7 Lathes.

The Carriage

Again the visual inspection is very important.

First check the top slide of the saddle where the

cross slide sits. On Super 7 and 254 Lathes the

saddle is scraped to the cross slide, look at the

condition of the scraping marks. If the cross slide

has worn a groove in the saddle then the saddle

will be scrapped, as we cannot hold it in our jig to

regrind the underside, as in bed and saddle grinding.

the thickness of the bedways (shears).

A 1-2” (25-50mm) micrometer to check for

wear across the front bed ways on narrow guide

beds and a 4-5” (100-125mm) micrometer to

measure across the bedways of a wide guide

Series 7 Lathe bed. Finally a 5-6” (125-150mm)

micrometer to measure across the bedways

of a 254 Lathe.

Take a irm hold of the toolpost stud, to determine

if there is back to front movement in the cross slide

(see photo). This will indicate the backlash in the

feed screw and nut. If there is excessive movement

you may not be able to adjust it out and a new feed

screw and nut will be required (if the toolpost stud

is loose in the top slide top a replacement casting

will be required). Visually inspect the condition of the

cross slide and top slide tops, check the condition of

the tee slots. Look at the jib adjusting screws, if in

poor condition it may also indicate a hard life.

To establish what the bed measured when

new take measurements at the extreme right

hand end of the bed as this rarely gets used.

Make a comparison with a measurement taken

approximately 6-8” (150-200mm) from the

spindle nose at the point where the saddle is

most often used. If the variation in thickness of

the bed shears is more than 0.005 (0.127mm)

or the variation in the width across the front

shear or both shears is more than 0.003”

(0.076mm) then the bed will most deinitely

require a bed and saddle regrind.

Procedures used in Factory Bed

& Saddle Regrinding

All Lathe models

The nominal thickness of the shears

(bedways) on a inished new

Myford bed is approximately 0.5”

(12.70mm). The maximum that may be removed

from the top of the bed is 0.025” (0.635mm) before

complications occur in aligning the apron with the

rack and leadscrew.

Check these and 254 Lathe beds with a 0-1”

(0-25mm) micrometer to measure for wear on

During a Myford Factory Bed and Saddle Regrind

metal removal is kept to a minimum, however it may

be necessary to reduce the thickness of the shears

between 0.005 (0.127mm) and 0.010 (0.254mm)

to get back to a sound top surface. In theory it’s

possible to regrind a bed between 2 and 5 times.

Indeed, as our records show, this has been done for

a number of customer owned lathes.

Procedures used in Factory

Carriage Rebuilding

All Lathe models

Regrind the tops of both cross slide

and top slide. Reit the toolpost stud

and it a new anti torque in a new

position. When re-assembled check for facing cut against

alignment jig. The nominal thickness of the shears

Note: It is not possible to do a full bed and

saddle regrind on an ML10, Speed10, or

Diamond 10 Lathe. At best the top of the bed can

have 0.005” (0.127mm) removed, a once only

operation, so your visual inspection is crucial.

Gearboxes and

changewheels

Engage the tumbler reverse

lever and check that the drive

train to the leadscrew functions

properly. If the Lathe is itted with

a quick change gearbox run this

through the 8 speed selections on

the front of the gearbox to ensure

that neither the tumbler selector gear nor

the gears on the cone or layshaft are damaged,

these can be complex to replace. Remember

you must stop the Lathe before moving the

selector lever. Check that the selector lever

on top of the gearbox also functions correctly.

(This can be done with the gearbox running.)

Procedures used in Factory Rebuild

Super 7 and ML7 Changewheel

Check and reit leadscrew, checking

bushes in right hand and left hand

brackets, set engagement of half

nuts. Reit changewheel guard and drive train from

headstock spindle to leadscrew itting standard set

of changewheels.

nut and replace where necessary. Reit half nuts

and complete assembly. Reit apron to lathe, check

and adjust rack pinion for meshing with rack.

Super 7 Powerfeed

Fit new rack pinion, hand traverse

pinion and Oilite bushes as required.

Check leadscrew, half nut and

replace as necessary. Reit half nuts and check for

closing balance on jig. Reit apron to lathe, check and

adjust rack pinion for meshing with rack.

Super 7B and ML7B Gearboxes

Remove Quick Change Gearbox

lid and lush out. Reit gearbox to

lathe. Check and reit leadscrew

checking bushes in the right hand bracket and

setting engagement of half nuts. Reit gearbox

guard, backplate and drive train to spindle.

The Leadscrew and Apron

A visual inspection is all that’s needed.

Compare the leadscrew’s centre section where

most of the work is done with that at the back

of the machine. Are the threads worn or are they

becoming ‘sharp’? If there appears to be too

much play in the saddle when the leadscrew is

engaged a pair of half nuts will often bring the

play back within tolerances.

254S and Plus, Gearboxes

Flush gearbox, check for any obvious

wear or damage and rectify as

necessary. Reit gearbox to lathe.

Check and reit leadscrew setting half nut engagement

and checking bushes in right hand bracket. Reit drive

guard and backplate and drive train to spindle.

254S & Plus

Fit new rack pinion, hand traverse

pinion and Oilite bushes as required.

Check leadscrew half nut and replace

as necessary. Reit apron to lathe. Check and adjust

rack pinion for meshing with rack.

Ml10, Speed 10 & Diamond 10

Fit new hand traverse pinion and

counter pinion as required. Check

leadscrew half nuts and replace as

necessary. Reit half nuts and complete assembly.

Reit apron to lathe.

ML10, Speed 10 and Diamond 10

Changewheel

Check and reit leadscrew, setting engagement of

half nuts. Reit changewheel guard and drive train

from headstock spindle to leadscrew itting standard

set of changewheels.

Procedures used in Factory

Re-assembly of Apron

Super 7 & ML7 Non-Powerfeed

Fit new rack pinion and hand traverse

pinion if worn and new Oilite brushes

where required. Check leadscrew, half

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: