1/4" BSF. Only the outer 0.350" or so is threaded. The rest measures 0.193" dia or 4.9mm (just a BSF clearance) and is about 0.750" long with a bit of a lead-in taper at the inner end. Overall length is about 1.080". I have a used spare in my hand but new Myford will sell you one. Part A1987 Backgear eccentric screw. Same on Mk1 as the later ones up to metrication.

Good luck, Dennis

Well now, what size drill did you use? BSF tapping is 5.3mm for a good fit. If you have drilled out much bigger than that you are going to have to form a new thread area at some bigger size and make a special screw to fit or do as you suggest yourself with a plug. If you have gone off-centre with your drilling (which is likely) then a plug would be better with a pre-drilled and tapped central hole. Since your new screw is tight there is a chance you can form a fresh 1/4" BSF thread in what is left, but it sounds as if you have drilled out too big to do that. Note that the hole/thread must be fairly square to the original hole for the eccentric shaft to lie in the right place. Whatever you do, you need a right size set of second and plug tap.

As a second thought your new screw from new Myford may have a 6mm metric thread.

Edited By DMR on 31/12/2018 22:51:47

Hello Paul,

While you have the eccentric dismantled, if you have the ability to do so, run an end mill along the shaft that carries the combination reduction gear to act as a reservoir along the bearing surface on either side of the oil feed hole.

A previous owner on my lathe had pumped grease into it from the nipple, it had set stiff and semi rigid, thus severely restricting oiling and the gear had partly seized on the shaft as a result

Regards Brian

Paul,

Absolutely, but I won't tell the ethics police if you are discrete about it !!

The slot doesn't need to be deep by the way, I cut mine to about 1/2 mm..

Brian

Paul,

It would be nice if you can use the genuine screw, the anchoring duty is light in the extreme and it keeps that fitting as would be expected for anyone following on with it as another owner.

I dislike mixed thread form screws on a machine; some of them are nearly right in terms of engagement in one direction, but it is not of course reciprocated in the other. On my ML7R for example, the apron is held on with imperial cap screws, but the bed jib with the laminated shins behind it that controls lift is fastened with two very similar looking metric cap screws.

Mix then up in a rebuild and you find this out when one hand is holding the apron in place and the blasted bolt engages but goes no further.

Regards Brian

Agree with the sentiment of not using metric threads on an Imperial machine., only a source of confusion in the future for you or someone else.

Maybe I've misunderstood, but having used a 5.5mm drill, a) M6 would be a loose fit (Tapping drill should be 5mm) and 1/4 BSF will be 6,354mm OD anyway.

If a 1/4 BSF bottoming tap won't clean the threads sufficiently, my advice would be, if enough meat is present, to drill and tap to 3/8 (BSF or BSW). If you drill out in small increments, the drill should follow the original hole.

Make a bush with 3/8 external thread and 1/4 BSF internal and use an anaerobic sealant to lock it in place. As a fitting tool, put a nut on a 1/4 BSF setscrew and run the bush into place, flush with the surface, back off the nut and remove the setscrew. Once the anaerobic has cured, (allow 30 minutes minimum) reassemble (It may be worthwhile to grease the new eccentric screw, so that the thread is contaminated, and any stray anaerobic does not cure on to it) and you should be back in business.

Howard