Thread: Cross slide lead screw wear issue

When you get it into position to make a cut, do up your cross slide lock or tighten up the gib up if you don't have a lock, that will hold it solid enough so it doesn't move.
These are usually left hand so you will be cutting left to right so you don't need to worry about with drawing it as it will run off the end. But if your set up needs it, do turn the compound around and use that to with draw the tool instead.

Dave

I dont think slop in the crossfeed nut should be a major problem. Even with a new nut and a new screw you arent going to get rid of all the slop. If your tool is pulled into the work you may have the wrong tool angles for the material you are turning.

Am I crazy? I know my crosslide has heaps of slop

Stuart

Why don't you make a ACETAL nut ..the process was described here somewhere ..........
Making Acetal leadscrew nuts the easy way - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

And here ..............Having Trouble With Acetal Nuts - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

maybe try again making the lead screw again. im shore your last try tought you a thing or two. just pay attention to the details,.. grinding the cutting tool is something that needs to be right. after saying this i should let you know ATM im trying to buy and not make a cross slide screw.

Stuart is right in saying it shouldn't be pulling in, so your tool shape might be wrong.
This would have to be the best documented thread on making a new cross slide screw, complete with pictures of grinding the tool etc.
Making a new Cross Slide Acme Screw - Practical Machinist - Largest Manufacturing Technology Forum on the Web

Dave

thanks dave good post

Dave

My lathe doen't have a cross slide lock and the jib adjustment is mounted on the front of the cross slide. Tapered jib moves in and out with a pair of nuts. The short answer is I am not sure there is enough adjustment left to lock and very fiddly. I will look at possible lock methods tho. Just use the compound is a good idea. The compound ways are nice and firm.

Stuart

Maybe you are right about tool angles. I ground my own tool from HSS blank. I just had a quick look at
Making a new Cross Slide Acme Screw - Practical Machinist - Largest Manufacturing Technology Forum on the Web
as listed in a later post. That is how I ground my tool except I did not have a guage. Material was mild steel. 4 deg was listed as angle of grinder table to provide relief. I think I estimated a suitable angle by eye but was similar. I think my angles were ok but I am always open to suggestions.

I have just picked up on a potential reason for my issue. I am skipping back and forth from the page above as I type this. I did not set the compound at 14.5 deg. Classic mistake. It did not cross my mind.

Making a new nut without replacing the lead screw would be pointless as there is more wear in some places than others. All lathes wear their lead screws and ways more at the main cutting position. This is very obvious on my lathe.

I will try again and typing this post has taught me something, well reading instructions from another site while typing this has. Thanks for the link Dave. I will study it carefully.

I need a nut insert first tho. From what I have seen of those instructions he already had a nut available. I was going to buy a bronze nut insert and press it into my existing nut after machining it out. The existing nut is pure cast iron. What is the best nut material to use? I am going to read about the acetal nuts but I would like to start with the best material.

Azzrock

I am going to ring next week to see what parts are available and at what cost but I am not holding my breath on that.

Dean

Originally Posted by Oldneweng

Making a new nut without replacing the lead screw would be pointless
Dean

Dean
Not necessarily. Depending on the amount of wear you might be able to set the screw up and chase out the flanks of the thread. Then machine a new nut to fit. It wouldn't be a perfect acme profile but would still work fine.
I did this 20 years ago on the cross slide spindle of an old Purcell lathe I owned at the time. I was lucky in that I had access to another lathe which made it easier but if I hadn't had the access to another lathe, I would have made up some sort of temp cross slide adjustment using thread bar.
What I did was certainly a lot quicker than making a complete new spindle from scratch.

regards
bollie7

Yet another possibiliy to consider. That would be a perfect use for the easy acetal nut method Morrisman linked to. It should work fine although my leadscrew / nut has a lot of wear. To machine the screw I think clamping the slide and using the compound would be ok. I will also need to give thought to how to hold the end. My centre may be too big. The travelling steady will impinge on it, not to mention the cutting tool. Much to think about. Thanks for the idea.

Dean

Hello Dean,
I converted my lathe cross slide and compound slide from Imperial to Metric a few years ago.I was able to buy the cross slide screw and dial from Hare and Forbes in Sydney (They had a box of dials and screws out the back and I was fortunate to find just what I wanted). I made a steel body for the nut and cut the thread in a piece of round phosphor bronze which I intended to press into the steel body,but the bronze piece crushed because of the thin wall. I then made another bronze piece which I machined to a slide fit and I loctited it into the steel body. Success. It may be preferable to buy a screw and adapt it to fit your lathe than try to cut one because the accuracy of the cut thread will be dependant on the wear on the leadscrew on your lathe. What are the dimensions of the screw on your lathe?
Russell

The original cross slide lead screw was 5/8 inch diam, 8tpi left hand acme and the thread section is about 205mm long. I would prefer to stay with imperial for simplicity but I actually use metric when I machine and convert as I go so no biggie. I have made a handwheel with imperial markings ( from a metric stainless steel tape measure LOL).

I understand what you are saying about the main lead screw and you are correct. I have no idea how worn it is in truth. I have had no luck yet in finding a supply of suitable threaded rod which is what started this thread. I have had one email stating only 6 TPI in 12 ft lengths available and another where 12 ft lengths only available but no mention of TPI so maybe 8 like I requested (or maybe not). $115 dollars plus gst for that so does anybody else want some? LOL.

Dean

Yeah maybe. I think my small lathe uses 5/8 for the CS but would have to check pitch. $115/12= $9.50/m. Pretty cheap if you get enough takers.

I have no problems there. I was going to pay $8.30 per foot from US but the postage was a bit of a problem. It was 3 times the order cost, about $US180. I would not be adverse to buying the whole length normally but finances are tight at the moment. I don't know what freight would be from the Gold Coast but I think it would be less than from Kirkwood, Missouri.

Actually I made a mistake. That price was for the 6TPI rod. The correct price is $118.00 for 12 feet. A nut would cost $16.10. Both prices are ex gst. I don't know what type of nut yet.

Dean