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Tony Jefree`s CNC conversion of the Myford ML7 Lathe (MEW May 2008)

CNC conversion of the Myford Super 7

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GLENN BUNT20/03/2010 07:27:46
10 forum posts
34 photos

Hi,
I am looking into Tony Jefree`s CNC conversion of the Myford ML7 Lathe (MEW May 2008). Tony recommends fitting your Myford ML7 Cross Slide Bearings Set (Part no MYFML7CSBS) to the ML7. My conversion will be on a Myford Super 7 and I see that the kit it doesn’t fit the Super 7. Why is this? Is the cross slide lead screw diameter larger? Does anybody know of an alternative kit / bearings I could use?

Many Thanks

Edited By David Clark 1 on 20/03/2010 08:48:16

John Stevenson20/03/2010 08:37:42
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5068 forum posts
3 photos
There are actually three different cross slide arrangements for the Myford.
The ML7 which has a 3/8" bearing diameter.
The Super 7 which has a 1/2" bearing diameter.
And the Super 7 with power cross feed which has a 9/16" diameter.
 
I have done conversions for all 3, well 2 actually as the ML7 was already done and this is being written up for MEW and Ketan at ARC is making the kits up.
 
John S.
David Clark 120/03/2010 08:50:13
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3357 forum posts
112 photos
10 articles
Hi John
Thanks for letting me know.
When will I receive the articles?
Just about to plan the next three issues of MEW out this weekend.
If it is not planned into them it will be five months before it can appear in print.
 
regards David
John Stevenson20/03/2010 09:04:51
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5068 forum posts
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David,
I'll get on to them this weekend and keep in touch.
 
John S.
John Haine20/03/2010 14:38:17
5563 forum posts
322 photos
I have taken a different approach with my PXF S7, as I didn't want to take any risk with Myford's engineering.  I have made a new feed screw, bracket and feednut, so the Myford components can be safely stored un-modified in case I want to revert.  I looked at the Myford screw and bracket and couldn't see an easy way to add ball bearings anyway (looking forward to seeing John's article therefore).
 
I use an M12 x 1.75 threaded rod (stainless) with an 8mm silver-steel stub let loctited in one end for the X-feed screw.  I bought suitable ball thrust races and a needle roller race from Arc with 8 mm bore.  All the bracketry is made up from aluminium sheet suitably machined.  Rather than the arrangement that Tony used the stepper is bolted to a sub-plate, spaced off a plate on the end of the new bracket.  I used 16 to 28 tooth belt timing pulleys to correct the feed to 1mm per rev of the stepper.  On the lead screew I used a similar approach to Tony but simplified the structure - there is no need for the sleeve that he put inside the plain P-bracket bearing to centre the roller races, these are just aligned with the dust caps.  I'd be happy to share photos of the approach if interested. 
 
I'm delighted with the results - despite using commercial studding for the cross feed screw (with a bronze nut) it is dead accurate as far as I can measure and no more backlash than Myford's original screw and nut.  I'm sure it will wear quicker but I can easily make a new one!
 
John.
KWIL20/03/2010 16:23:56
3681 forum posts
70 photos
I kept the original Myford leadscrews on my non CNC S7s but fitted needle thrust races in a modified Myford bracket. [shorter bearing length and with a shortened adjusting "ring" to set end load]
John Stevenson20/03/2010 16:49:58
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5068 forum posts
3 photos
The ML7 can be modified by just modifying the bracket, the rest isn't touched and this is to fit one ball race and two needle roller thrusts.
 
The same applies to the Super 7.
 
The S7 PF is a different animal as it has a larger bearing diameter that cannot be reduced because the bearing diameter is 9/16" and the screw is 1/2"
Also there is a cross drill hole to take a pin that knocks the power feed out if left unattended, boring into this will weaken the pin.
 
 In this case only the needle thrusts are fitted to get zero backlash but it means the bracket, screw and dial have to be machined.
 
Because it's a "Myford" many of the flat earth society, sorry purists, will not do this because it's not British Standard Myford.
 
You make your own choice.
 
John S.
John Haine20/03/2010 21:27:32
5563 forum posts
322 photos
Actually John, flat earth has less to do with it than the cost of a new PXF leadscrew and matching nut if one cocks up, not to mention the difficulty of using a lathe to machine its own feedscrew.  Now if I had the space and cash for a second lathe....
John Wallett13/09/2010 12:49:43
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18 forum posts
John S I have been waiting for the mods for the S7 PX but I gather they have not got as far as ARC yet.  
Can you point me in the right direction in respect of what I need to have a go!
Thanks,
John. 

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