The Myford lathe has obviously been abused at some stage in it's life the top surface of the shears has numerous dings. It can still turn very accurately though which suggests it's been in some training facility rather than industry.
I've been experimenting with using inserted tip parting tools in the last few weeks and noticed a lot of movement in the saddle. Having done some research it seemed like the face of the saddle that bears on the rear face of the front shear (see pic below) was likely to have worn. The accepted fix seems to be to mill off this face so that the rear of the saddle bears on the rear face of the rear shear. Moving from a narrow guide to a wide guide. See Graham Howe's Model Engineering Site. For more info on this idea.
I had psyched my self up for this drastic change as so began to strip down the saddle assembly. First the cross slide was wound all the way forward until the lead-screw disengaged from it's nut. The red arrows point to mysterious tapped holes which are good for collecting swarf.
After bit of head scratching the 5 cap head bolts (green arrows) were removed, luckily the half nuts had been engaged as they were the only thing stopping the Apron from dropping. A bit of hasty propping followed!
Next the 4 gib strip adjusting screws were slackened right off. I could then remove the gib strip as the saddle was slide towards the headstock.
Next job was to remove the saddle "keep plates" which stop the saddle lifting. The front one is held in place by two different length cap head screws. The rear by three hex head screws which are underneath (yellow arrows). Be careful I found shims on both keep plates.
The front keep plate has one shim per bolt.
The Rear has two shims per bolt. Note large hole in the Rear plate to give clearance to the saddle lock.
It is now possible to lift the saddle from the lathe and examine the underside. It seems the more forward hole on the saddle is for the moving steady. I don't know what the one behind it is though. The other mystery hole at the rear is for the suds delivery tube mount. All of these holes are tapped 1/4" BSF - luckily I had a tap so ran that through a few times to clear the swarf. A quick rummage through the scrap bin turned up some Hex head bolts in lieu of the correct grub screws. Should make attaching the Steady easier.
The underside was given a good clean up and I flushed through the lube points with Myford's improved oiler. Previous owner has mistaken the oiler points for grease nipples so any excess grease was removed.
I then measured the distance between the two front shear bearing faces using a digital caliper. I couldn't actually measure any wear. It was difficult as their is a line crud below where the shear bears but it wasn't near as bad as I was expecting. Time for a change of plan. I refitted the saddle (shims are very fiddly) and adjusted the saddle until it would just move with two handed pressure. I could slide the saddle the full length of the bed without any binding. Hurrah. Next job is to clean up the apron.
I didn't remove the apron there was room to get in with a variety of tooth brushes and copious amounts of WD40 to dislodge the accumulated crud. I paid special attention to the half nuts and the pinion gear that engages in the rack. The whole lead screw and rack was also given a good clean up.
The apron was offered up to the saddle and the 5 cap head screws were put in hand tight. I then engaged the half nuts and traversed the saddle and nipped up the screws.
Last time I went to Myfords (luckily only 30miles away) I purchased a couple of the felt wipers so I decided to put in a new one after soaking it in oil.
Another purchase was the official improved Myford Oiler which doesn't leak like my converted grease gun. The nozzle isn't a perfect fit on the oil caps though so I'll modify it to match the nozzle I made. It is heartening to see the oil being pushed out from under the saddle.
Next up was a really dirty job - cleaning the Cross-slide - this was filthy the top surface is very stained and has huge dents/ridges where something bad has happened the tee slots were so full of crud I couldn't get the tee nuts in. One of the slots had been closed up where the top surface had been deformed :-( not good. There is a circle of wear where the top slide is mounted. I think I'll see if Myfords have any on offer at the next open day in April. If not I might skim the cross slide on the milling machine.
I've used wire wool and WD40 to clean off all the crud and used a smooth file and stone to remove the high spots caused by the damage. I carefully opened up the damaged Tee slot too (see the Tee Bolt I used as a gauge fits now!)
The gib strips had any crud carefully stoned off. I paid particular attention to the ends of the gibs. I also marked them with a permanent marker so they would be replaced where they came from. The gibs were fixed with the four holding screws being slight loose. The gib adjusting screws and nuts were given a quick clean and again loosely attached.
A quick splash of oil was applied and the cross slide re-fitted to the saddle. To adjust I moved the slide so that the front gib was centrally placed on saddle i.e. not over hanging the saddle. The screws were Nipped up and then slackened off just enough for it to move smoothly. Then the slide was pulled forward so the rear gib was central on the saddle and adjusted that to suit. The 4 gib securing screws were then tightened. Result was a smooth and secure cross slide with no discernable rocking - NICE!
The final part of the cross slide was replacing the leadscrew. When I bought the lathe it came with a replacement leadscrew, nut and handle. The new parts had a number of problems one was the screw was bent near where it attached to the handle and the other was that the brass pad that the grub screw bearss on was missing. This meant I had damaged the thread. I had a look at the old assembly and it seemed okay just the dial was stiff and dirty. A quick clean up with emery and it's loads better. Still a bit stiff so I might swop the dials over at some point. I have a new nut to try with the old screw if they is any backlash.
Here's the complete top slide assembly you can clearly see the triangular section slot that is used to hold the base to the cross slide. There is plenty of dirt to clean off and much abuse to sort. You can see the Quick Change Tool Post is still in place.
The QCTP has been removed here revealing the damage to the top slide top surface. The Post is wobbly too!
The two halves are seperated by unscrewing the lead screw. I loosened the four gib screws first.
The handle assemly was removed by unscrewing the two cap head screws and it was put to one side. You can see the grime on the casting and gib strip here.
These were cleaned up with wire wool and WD40. Any dings were carefully stoned out. You can see it is looking a lot brighter here.
The scraping marks on the slideways are still clear.
Heres the top slide base mounted back on the cross slide. This did not need much work, just the angle dial cleaning with emery, it is much clearer now.
Unfortunately the top casting needs a lot more work. The post was pushed through from the top. And the three small grub screws also removed. I'm not certain what these grub screws do. They may allow you to adjust the post if it is not vertical. STOP PRESS I've just been told these are blanking screws. The detent assembly is mounted via these holes when you use the Myford Four way tool post.
The top face is very pitted and worn convex, well either that or the casting has been distorted by over tightening. I first tried to sort this by carefully filing the top surface.
I followed this up with some emery on the surface plate. A bit of engineers blue was then employed to see what we had.
As you can see there is still a high spot in the centre. I thought this was small enough to scrape out so I spent a hour or so scraping with a flat scraper. It's hard to see a difference on th ephotos but the high spot has grown outwards. But still tons to do.
I've decided to machine the top surface on my shaper as it is too bad to correct with scraping. I also need to drill and tap a couple of holes, so that the gib strip can be locked when the top slide is not being used.
Getting the shaper setup was not too bad clamping was pretty straight foward I always follow the don't use one clamp when you can use two rule when using the shaper because if you get it wrong it's pretty dramatic - low flying castings anyone! The clamp at the left of the picture is stopping any lateral movement of the top slide and the top clamp is stopping it lifting. Adjusting the shaper throw to avoid hitting the top clamp took a little trial and error but I'm still learning how to use the shaper effectively.
It only took a couple of passes to (1 or 2 thou each) to get a nice level surface. We'll not talk about the small gouge I made setting up the shaper.
I'm using indexable tooling in the shaper which doesn't leave a great surface finish so a few minutes on the emery on a surface table cleaned up the worst. Its started to get very polished which I didn't want - I've had problems with the tool post rotating under heavy cutting loads! I'm pretty pleased with it, about 90% of the pits have been removed.
Next job was to mark out the two clamp screw holes these are drilled 4mm and then tapped 2BA to match the existing grub screws. You can just see I've clamped the top slide to an angle plate to keep it level.
Here's the four gib screws and two locking screws in position.
The top view the tool post has been refitted and the three grub screws. I'm still not sure what the screws do.
The top slide lead screw is quite accurate but the graduated collar had locked solid and took some persuasion to remove (soft faced Hammers are your friend) The problem was acombination of fried dirt and possible abuse. I cleaned up the shaft with some emery and polished the collar so the numbers stand out. Bit of Nuto and it's a smooth as a babies proverbial. I adjusted the locking collar and grub screw so the handle turns nicely but with no backlash.
The nut was reattached to the base with two pan head screws and the screw assembly was screwed into the nut. The assembly was attached to the moving part of the slide with the lead screw in as far as possible to the base. This keeps the whole thing in alignment.
Now it's done phew! I can get on with doing some model engineering now....
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