Myford ML7 feedscrew misalignment

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Myford ML7 feedscrew misalignment

This topic has 16 replies, 9 voices, and was last updated 18 March 2022 at 09:36 by Chris Bill.

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9 March 2022 at 21:57 #14498
Chris Bill
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@chrisbill23191
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9 March 2022 at 21:57 #588995
Chris Bill
Participant
@chrisbill23191
Hi all,

I just replaced my imperial, standard length feed screw on my ML7 for the long cross slide metric one.

Immediately I noticed the cross slide has become EXTREMELY tight. Stepping backward in the assembly I noticed that tightening down the knob holding bracket (not sure of real name) caused deflection in the feed screw, which spun quite freely before being assembled.

I went back to the old feedscrew and examined it – the wear pattern in it seemed to support this as the screw 'rocked' within the nut even if the end-play was not significant.

Has anyone had any issues where the Myford feedscrew bracket was not correctly alligned? Shimming it out doesn't seem an option as the hole in the bracket is quite tightly toleranced against the feedscrew and would cause binding.

I'm hoping for some advice before I go back and oval out the holes on the mounting bracket – I'd hate to go modify original parts (beyond having to drill out the apron for the long feedscrew :/

Thanks!
9 March 2022 at 22:04 #589000
Chris Bill
Participant
@chrisbill23191
*Saddle – not apron. I had to drill out the saddle for the long feedscrew. Anxiety-inducing for sure.
9 March 2022 at 22:11 #589003
Hopper
Participant
@hopper
It is usual for there to be a bit of room to manoeuvre that end bracket for alignment. Usually, with the bracket screws loose, you wind the cross slide right in so minimum feed screw is sticking out and then tighten up the two screws holding the end bracket in place.

But if that does not work, something is out of line. You need to find out what. It could be one of several things such as the face on the bracket not machined square where it sits on the end of the cross slide, the screw holes being in the wrong place, the hole for the feedscrew not being correctly located or not being square. It could also be the thread in the brass feedscrew nut is not square to the OD and flange.

First thing I would do is check everything for squareness. If all that is good, then elongating the screw holes is probably the best option. Or buy a new end bracket.

Edited By Hopper on 09/03/2022 22:13:03
10 March 2022 at 12:57 #589124
Chris Bill
Participant
@chrisbill23191
@Hopper good advice. Based on the old nut also showing signs of wearing in to a misaligned status I'm willing to bet that any out-of-squareness starts with the bracket, but will get out the square and have a go.

As an add-on, I was surprised at the amount of wear on the bottom of the saddle from eating chips the way wiper didn't catch. I may be in the market for a new saddle before this is all done.
10 March 2022 at 14:07 #589137
KWIL
Participant
@kwil
Chips can also enter from the right hand no wiper side.
10 March 2022 at 21:22 #589234
Chris Bill
Participant
@chrisbill23191
I ended up filing down the bracket – things got better but only near full insertion of the lead screw. 'Lead's me to believe I've sorted out the alignment issue – remaining stiffness when lead screw is sticking way out (where alignment should be less of an issue) may be due to poor manufacturing tolerances (aren't all the new Myford parts getting made in India?). I backed off the gib strip screws to control for this, no change.

I don't have thread wires for micrometer measurement of minor diameter, but I may try to get a caliper on the threads tomorrow to see if I can get a repeatable result on the minor and major diameters at each end tomorrow and see if this shows anything.
10 March 2022 at 21:50 #589235
speelwerk
Participant
@speelwerk
To set the gib strip correctly you remove the bracket and lead screw from the cross slide. Niko.
10 March 2022 at 23:16 #589246
Hopper
Participant
@hopper
Posted by Chris Bill on 10/03/2022 21:22:57:

I ended up filing down the bracket – things got better but only near full insertion of the lead screw. 'Lead's me to believe I've sorted out the alignment issue – remaining stiffness when lead screw is sticking way out (where alignment should be less of an issue) may be due to poor manufacturing tolerances (aren't all the new Myford parts getting made in India?). I backed off the gib strip screws to control for this, no change.

I don't have thread wires for micrometer measurement of minor diameter, but I may try to get a caliper on the threads tomorrow to see if I can get a repeatable result on the minor and major diameters at each end tomorrow and see if this shows anything.

Take the bracket off and take the feedscrew out of the bracket. Then try screwing the feedscrew into the nut. If there is a problem with the screw thread, you will feel it when you get to that part of the screw. If it gets tight, have a close look at it. There might be small burrs on the thread you can remove with a fine file. Or you may be able to buy a die from Tracy Tools and run it down the thread to make it uniform all the way along. (Or preferably send it back to Myford as unfit for purpose and get a new one in exchange. A new screw should not bind at all.)

As Nikko says above, set the gib strip screws without the feedscrew in place. Once you have the cross slide sliding nicely without binding or slop, no further adjustment should be needed. Feedscrew adjustment is a completely separate matter.
11 March 2022 at 08:37 #589264
Martin Kyte
Participant
@martinkyte99762
When replacing crosslide feedscrews(Leadscrew) the proceedure is :-

With Leadscrew removed clean and lubricate the dovetail slide and adjust the gib for smooth hand action without play.

Assemble the leadscrew nut and and the leadscrew end plate with the leadscrew in place with the endplate floating ie fixings inserted but not tightened.

Screw the leadscrew into the nut so that the cross slide is in it's max infeed position and there is minimum distance between the end cap and the nut. This will correctly align the end plate and the endplate fixings may now be tightened up.

regards Martin
11 March 2022 at 10:04 #589281
John P
Participant
@johnp77052
Posted by Chris Bill 09/03/2022 21:57:14

Hi all,

I just replaced my imperial, standard length feed screw on my
ML7 for the long cross slide metric one.

Seeing the problems that you are having with this ,there was no
indication from where that you obtained this replacement leadscrew.

There have been 2 such similar threads on replaced Myford
leadscrews that have had the same problems as you have.
Just as a matter of interest did this screw come from RDG.

The two similar thread postings are below and may be worth reading .

https://www.model-engineer.co.uk/forums/postings.asp?th=175278

https://www.model-engineer.co.uk/forums/postings.asp?th=173467

John
11 March 2022 at 10:19 #589284
john fletcher 1
Participant
@johnfletcher1
Out of interest, Scarborough Mates (Shed) has several brand new "Beeston Myford" cross and top slide screws for sale. Should any one be interested please feel free to contact me via a PM. and I'll contact the SHED next week. John
11 March 2022 at 11:10 #589294
David-Clark 1
Participant
@david-clark1
You need to set up the feed screw between centres. Check for eccentricity, both ends of the feed screw and both ends of the handle end.

If out of true, you will have to return it to the seller or lightly skim the handle end so it is true.

Use a collet chi/ck if you have one.Now you need to bush the handle support bracket so it fits the re-turned portion of the feed screw.

It might be worth getting hold of Martin Cleeve’s articles in Model Engineer about doing this although it may have been George Thomas who added ball and/or a thrust race to the cross feed screw. I think it may have been published in George’s Red workshop book.
11 March 2022 at 12:42 #589316
A Smith
Participant
@asmith78105
Did you fit a S7 crossslide by any chance? If not, ignore the following. The S7 cross slide comes in a least two versions. The relationship between the feedscrew and the two securing screw hole centres (handwheel bracket) differs between the two that I have. This would cause the problem that you've encountered. Check the ML7 slide against the S7 by placing them on a flat surface and comparing the vertical position of the tapped holes.

Andy
18 March 2022 at 08:40 #590391
Chris Bill
Participant
@chrisbill23191
So I think it came down to a fit-finish of the feed screw. Looking closer, I see what I believe to be some chatter on the major diameter of the screw. Also, the edge between major diameter and where the pitch descends is quite sharp. Any 'rocking' of the feedscrew within the nut immediately causes it to bind. I ran the screw through the lathe with a file riding on the sharp edge and got some improvement in cross-slide movement.

The cross-slide gib was set without the feedscrew engaged, so I'm pretty confident it's not gib adjustment related.

@A Smith, unsure if this is the ML7 orS7 long cross slide. It was on the lathe when I bought it, though the original owner had never added the long feedscrew to match.

@John P part bought from myford_ltd on Ebay. I will say I was quite upset with how it shipped – a long, narrow tight-tolerance screw was put in a bubble-wrap lined bag. No box, so high probability of getting bent in transit.
18 March 2022 at 08:54 #590396
Hopper
Participant
@hopper
Time to return to sender as unfit for purpose. They should send you another one.

You can tell the Super 7 cross slide from the ML7 cross slide easily. The Super 7 cross slide has a much larger hole in it to accommodate the different Super 7 topslide. Quck check is the Super 7 topslide can be rotated the full 360 degrees because it is located by two screws on the sides of the cross slide. The ML7 topslide can only be rotated 45 degrees in either direction because it is held down by two bolts on top of the cross slide going down into T nuts in the slots. Those bolts are in two curved slots that limit the rotation of the topslide. If you have the ML7 topslide, you have the matching ML7 cross slide.

This is the ML7 topslide with the curved slot visible at the front.
18 March 2022 at 09:36 #590410
Chris Bill
Participant
@chrisbill23191
@Hopper It appears I have the ML7cross-slide then, but as it came with the machine I do not know from where it was sourced. Based on wear on original feedscrew nut and alignment issue I am experiencing I THINK the issue remains that the mounting bracket holes are incorrectly positioned (roughly 3/32" off center at all travel positions) with respect to the feedscrew nut center. I've hogged out the bracket a bit which has improved cross slide movement.

I left some ebay feedback for the feedscrew seller – postage is quite steep from the UK to Italy so unless the seller will cover 100%, I will probably move on to sourcing this somewhere else or making my own without BSF threads on the end. The BSF threads of the original feedscrew are making it hard for me to make improvements – again, expensive postage makes it annoying to buy a BSF tap and die set.

Chris
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