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Myford ML7 - Cross Slide Bearing upgrade

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This page details the process I used to upgrade the ML7 cross slide bearing.

I bought the bearing set from ArcEuroTrade for a very reasonable price, and followed their plan and instructions.

Link to the Arc Euro Trade ML7 cross slide bearings set

I spent an easy afternoon doing the upgrade, without any headaches or dramas.

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MYFORD ML7 CROSS SLIDE BEARING UPGRADE


I chose to machine the cross slide bracket on a face plate, and there are just two operations to complete.
The bracket can also be altered in the four jaw, or even on the milling machine.

 

↓ Before I dismantled the cross slide bracket assembly, I made a spigot. The spigot will be used later on, to align the cross slide bracket on the face plate.
The internal diameter of the bore in the cross slide bracket is 0.25inch or 6.35mm, which should equal the diameter of the plain end of the feed screw.
I turned one end of the spigot to 0.25inch (6.35mm) diameter, to match the diameter of the bore in the cross slide bracket.

 

 

↓ I made a block to fit on the faceplate.
The cross slide bracket will be fixed to this block.
I used a scrap piece of aluminium for the block, so there are extra holes from previous usage.
I drilled two holes to 4.2mm diameter, and tapped them M5x0.8.
I drilled two holes to 8mm diameter.

 

↓ I fixed the block to the faceplate, using two M8 bolts, and nuts and washers. I left things loose for now.

 

 

↓ The cross slide bracket was tightly secured to the block with two M5x0.8 hex head screws.
My cross slide bracket is painted black, which I think is original, and most of it has worn off.

 

 

 

↓ The cross slide bracket has to be centred on the face plate.
I don't things are too critical, and if there is some misalignment then you should still be ok.
But, it is best to be as accurate as you possibly can be; after all it is a Myford we are dealing with here!
.
I secured the spigot in the tailstock chuck.

 

 

↓ I brought the tailstock up to the faceplate and inserted the spigot into the cross slide bracket.
This centred the cross slide bracket on the faceplate.
Once centred, I tightened up the two M8 bolts.

 

↓ The spigot is a good snug fit in the 0.25inch diameter bearing hole in the cross slide bracket.

 

↓ After centering the bracket and rotating the faceplate, I noticed that the bore was not central in the boss. I could see a definite wobble. The bore was rotating on centre nicely, but the outside of the boss was not, which was a bit of a worry at first.
I measured things up and determined that there was plenty of material on the boss to enlarge the bore without problem.

 

↓ These are the bearings I bought from Arc Euro Trade.

Link to the ML7 cross slide bearings set

↓ The two bearings at the top are thrust bearings.
Each of the thrust bearings is sandwiched between two bearing washers.

 

↓ The single bearing at the bottom is a small roller bearing.
This small bearing fits over the shaft of the cross slide leadscrew, and inside the bore of the cross slide bracket.
The outside diameter of this bearing is 0.375inch, or 3/8inch or 9.525mm.

 

↓ The 0.25inch bore in the cross slide bracket has to be opened out to 0.375inch or 3/8inch or 9.525mm, to accomodate the new feedscrew roller bearing.
I had a 3/8inch reamer, so I decided to use a drill and a reamer to open out the hole, rather than a boring bar.
This reamer has a MT1 taper, so I had to rush over to Chronos and get a MT2 to MT1 sleeve, so I could fit the reamer in the MT2 taper in the Myford tailstock.
Here you can see the adapter sleeve and the 3/8inch reamer.

 

 

↓ I drilled the bore out to 9mm, and then used the 3/8inch reamer. Sorry, I have lost the pictures of that operation.
When drilling out the bore, I went up in 0.5mm drill size increments.
I could have also used a boring bar to open out the bore, but the cross slide was not functioning at this point.
The tables say to drill to 9.25mm, and then ream 3/8inch. I did not have a 9.25mm drill bit, so I opened out the bore to 9mm instead.
The cross slide bracket is cast aluminium (or something soft), and the reamer did not struggle removing the .525mm of material.
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↓ Houston we have a problem.
The next operation was to turn down the boss in the cross slide bracket.
I needed to use the cross slide to do that! Catch 22.
In a stroke of brilliance I came up with a cunning plan.
I made a temporary bracket, in order to get the cross slide functioning.
I drilled 3 holes in a scrap piece of aluminium plate, and secured the plate to the cross slide.

 

 

↓ I fitted four loose fitting spacers, and a bsf nut.
I then fitted the feedscrew handle against the bsf nut, and got things working again. Sorry I have lost the picture of that.

 

↓ This picture is of an earlier attempt, with only two spacers, and not the four I ended up using (but you get the idea).
I abandoned this earlier idea, because I realised I needed to use the dial, to test the cuts on the cross slide bracket.

 

↓ Now the cross slide was functioning again.
If I had realised all this earlier, I would have opened out the hole with a boring bar, instead of drilling it.

I proceeded to turn down the boss on the cross slide bracket. I cut off a little at a time.
The material has to be removed from the innermost ring of shiny metal (the boss) that has the hole in it, that you can see here.

 

 

 

↓ I took a small cut, and then offered the dial and outer thrust bearing and washers assembly up to the boss, to test the fit. I repeated this procedure again and again, creeping up on the final dimension. It's the only way.
The outer thrust bearing assembly is pressed against the boss by the dial.
The dial has to end up close to the cross slide bracket, without rubbing against it. There has to be a small gap between the dial and the cross slide bracket, and the dial has to press up hard against the outer thrust bearing assembly. That is what I aimed for.

 

↓ If you compare this picture with one of the above pictures, you can see how much I took off the boss.
I also took a skim off the end of cross slide bracket because there was a definite wobble there. That skim made the outer face of the bracket parallel to the face of the boss.

 

↓ I turned the boss down, a little at a time, until eventually the dial and outer thrust bearing assembly were a good fit against the cross slide bracket.
The measurement is not too critical. As long as the dial can be pressed firmly against the outer thrust bearing assembly, and not foul the cross slide bracket, then all is good.
If I had cut too much off the boss, then I could have put a thin spacer in between the dial and outer thrust bearing assembly, to make things good again. Fortunately, I crept up on it and had no problem.

 

↓ Some views of the fit of the dial against the cross slide bracket.

 

 

 

↓ That was the end of the face plate work.
Now it was time to fit the bearings and reassemble everything.

↓ The inner thrust bearing assembly was put in place.
The inner thrust bearing assembly is retained by the shoulder on the feedscrew.

 

↓ The small bearing was put in place.

 

↓ The bracket was put on the feedscrew and the small bearing went into the bore in the boss.
The bearing was a good light press fit in the bore, with no play in the bore at all; I did not struggle with it! The 3/8inch reamer had done its job.

 

 

↓ The outer thrust bearing assembly was put in place.

 

 

↓ The dial was screwed onto the feedscrew.

 

↓ With the cross slide bracket disconnected, I tightened up the dial.
The bearings and cross slide bracket are squeezed together, between the dial and the 'shoulder' on the feedscrew.
I gripped the end of the feed screw, and lightly tightened the dial until there was no play, and the dial was turning freely.

 

↓ The handle and dial were then tightened together, by gripping the handle by hand, and applying a spanner on the flats of the dial (much like a double nut affair).

 

↓ The cross slide was back up and running again, and the action was smooth.

 

↓ After testing the operation, I took it all apart, applied lots of molybdenum grease, and reassembled.

 

 

 

CONCLUSION:

The feedscrew and nut are fairly new and there is not much wear there at all.

Before this modification, I would tighten up the dial as much as I could, without the feedscrew seizing up, and be left with a little backlash and play (5 divisions or so). After a few hours/days of operation, the backlash and play would become as much as 1/2 to 3/4 of a turn. I would then have tighten up and go through the procedure again. I think the 1/2 to 3/4 of a turn of backlash was mainly due to the play that arose when the dial became loose against the cross slide bracket.

It appears to me that the backlash cannot be entirely eliminated; it will always be there between the feedscrew and its nut. But, almost all the play at the dial end can be reduced by the thrust bearings.

After this modification, the dial can be tightened up tighter. Also, the slide operation is definitely smoother, which is what I was really after.

The thrust bearings have enabled me to tighten the dial up a lot more than before; and I think virtually all the play has gone in that area. Some backlash is still present, and this is less than a division on the dial (at the moment, watch this space); and this is probably the play between the feedscrew and its nut.

It is still early days. I will use the lathe for while, and report back and let you know how it goes.

UPDATE 26-06-2020
After about a year of good use, I am please to say that the backlash in the cross-slide feedscrew is 4 divisions on the cross-slide dial. A simple tightening adjustment should reduce that.

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