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MYFORD SUPER 7 HEADSTOCK

TORQUE DOWN SETTING

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neil mackay28/09/2011 12:16:07
4 forum posts
 
I am rebuilding a myford super 7 circa 1976. The bed has been
reground and I am refitting the headstock. Does anyone
on the forum have data on the correct torque setting for
tightening the four M8 x1.25 x 25mm socket cap screws which
close the headstock onto the cast iron bed?
Any information would be most appreciated.

 

Many thanks

Edited By David Clark 1 on 28/09/2011 12:31:27

KWIL28/09/2011 15:46:02
3681 forum posts
70 photos
I have never needed to torque them down when rebuilding but my fingers tell me when, I could measure one I suppose.
 
Another point, was the saddle ground as well? If not you will need to be very particular when setting up the leadscrew etc.
neil mackay28/09/2011 16:36:45
4 forum posts
Thank you very much Kwil for your prompt reply. Yes the saddle was reground and fitted by a Myford fitter one of the last ones to be done before Myford sadly went out of business!
Ive re- fitted the apron and lead screw with no problems. I dont want to strip the threads
in the cast iron but would like them to be as tight as possible so if you could give me
a test figure without too much trouble this would be most helpfull. My fingers are not
as good as they used to be as I suffer from arthritis!
 
Best Regards, Neil
Richard Parsons28/09/2011 16:45:55
avatar
645 forum posts
33 photos

Neil,


First of all I would use a very thin smear of engineer’s blue (not marking out blue) and do a trial fit to the lathe bed. If the fit is less than 85% get the Headstock base reground as well.


Second get a nice straight bar just pinch up the headstock and with a sensitive DTI check that the bar is parallel to the bed OK if not well think about the use of a scraper.


Torque the bolts up by hand slowly in a star pattern leaving about 15 minutes between each tightening for the stresses to come out. Use a thin smear of oil on the bed when you do it.


There are no values in my Super 7 hand book (am I allowed to mention this by the new owners?)
RGDS


Dick

neil mackay28/09/2011 17:17:31
4 forum posts
Dear Dick,
Thanks for your reply. I have checked with a dial indicator with the head bolts
pinched down and I am getting a reading of 0.0002" over 4" on a test bar parallel to
the bedways so I hope this will be OK!
 
Best Wishes, Neil
Clive Hartland28/09/2011 17:26:44
avatar
2929 forum posts
41 photos
Neil, nip the bolts to about 5ft lb and then tighten to 12ft lb and then finally 20 - 22ft lb.
Criss cross between the bolts to even the load as you tighten.
There is no need to wait between tightening sequences, do not lubricate the bolts but put thin grease or oil on bed beneath the headstock. This will stop cutting fluids migrating under the head.
These are nominal figures for 8M x 1.25
 
Clive
Tony Pratt 128/09/2011 17:43:27
2319 forum posts
13 photos
Hi Neil, .0002" over 4" is I would think very very good and completely acceptable!
Tony
KWIL28/09/2011 19:28:29
3681 forum posts
70 photos
Neil,
 
By my fingers and then tested with a torque wrench 12 lbs. ft / 15 Nm.
 
Looking at the torque wrench charts for 5/16" BSF (8mm approx) they give 11.7 Lbs. ft. for a 20 ton tensile bolt, which I would use as OK.
 
Regards
 
K
neil mackay28/09/2011 20:03:02
4 forum posts
The information and advice is all very much appreciated. Thanks for all the new
contributions from Kwil, Clive and Tony.
 
Cheers, Neil
ady29/09/2011 00:14:31
612 forum posts
50 photos
I wouldn't get too hung up on the setup until I started chopping metal up.
 
Tie it down and then see what you can do with it.
 
 

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