Cross feed problem

[Phil MogerParticipant @philmoger15177]

There is a gritty feel to the cross feed mechanism on my Super 7 when taking the cross slide from near to far side although much smoother winding back.

I’ve inspected and cleaned and oiled both the cross feed screw and the cross slide feed nut and whilst they look OK, clearly there is significant wear to one or both.

The feedscrew and can be purchased together for around £76 and the feed nut can be bought separately for a less painful £22.

Is it likely when one needs replacing due to wear, that they both need replacing or is it worth the risk and just buying the feed nut?

The gritty feel is throughout the length of the feed screw which makes me feel that the fault is with the feed nut.

I’d appreciate any informed views on this.

Thanks.

[Phil MogerParticipant @philmoger15177]

[SkarvenParticipant @skarven]

To me, this sounds as if it could also be a problem with the bearing for the leadscrew.

I have no Super 7 experience, so take that for what it is worth.

I would check it, though.

Kai

[KWILParticipant @kwil]

As Kai says, look at the front bracket where the leadscrew passes through. Strikes me that it could well be worn on the front face due to swarf etc. but the rear face, as it is more protected may well be in good condition. Check how smooth the leadscrew thread is when passing through the nut on its own. The nut should be a good close fit, without excessive rocking.

Tell us what you find.

[Clive HartlandParticipant @clivehartland94829]

If you have a vertical slide for your Myford it will have the same bracket as the crosslide, you could do a swop and see if there is a difference in the feel of the traverse.

One other thing, when you tighten up the bracket screws make sure the crosslide is screwed in towards the saddle and then tighten the two skt.hd screws. This will ensure that you have minimum deflection of the bracket and the spindle is centered.

Clive

[AndyfParticipant @andyf]

I had trouble with a cross slide (non-Myford) where the dimple at one end of the gib was out of alignment with the adjusting screw, so that end of he gib was beig forced down to foul the slide base (i.e. the saddle). This resulted in the gib strip trying to dig in in one direction, but work more smoothly in the other.

In your case, the problem would be at the far end of the gib, but the grittiness would ease once the cross-slide was overhanging the back of the saddle. However, you say the grittiness is along the full travel of the slide, so it is probably due to some other cause.

Andy

[Phil MogerParticipant @philmoger15177]

Thanks to all for the speedy responses.

I dismantled the cross-feed screw and its components again and confirmed that there was no impairment of function between the screw and the cross slide end plate and that the grittiness was definitely related to the screw and the cross slide feed nut.

I wondered if there was some roughness of the threads in the nut and took a few turns of 400g abrasive paper around its bore with virtual elimination of the problem.

For the time being!

[Chris GunnParticipant @chrisgunn36534]

The Super 7 leadscrew nut is awhite metal casting, and could easily pick up swarf. If is is worn and the screw is OK, you can replace just the nut.

CG

[William(Bill) PooleParticipant @williambillpoole97014]

Similar problem with my ML7 last year but on retraction of the cross slide. Found that the CI locating pierce which I had made for my zeroable dial was picking up on the cross slide, I replaced the existing small tufnol washer with one I made from Teflon to cover the whole of the two mating surfaces which resolved the problem .

Trust this is helpful.

Bill.

[Ady1Participant @ady1]

Make your own nut and see how it goes

[Phil MogerParticipant @philmoger15177]

"Make your own nut and see how it goes".

Nice one. I wonder how many beginners have a 3/8" Acme tap on hand?

And the cheapest one I can find cost about the same as a new nut.

[Les Jones 1Participant @lesjones1]

Hi Phil,
I do not know how much space you have around the leadscrew nut on your lathe so I do not know if any of the suggestions on these two thread would help.

Lathe halh nuts (NOTE half was miss spelled in the title which makes it hard to find.)

Lead screw nuts

Les.

[AndyfParticipant @andyf]

If you can stand the thought of a Delrin nut, there's always this method, using an electric paint-stripping heat gun rather than a tap.

Andy

[Ian S CParticipant @iansc]

Had a friend how was having trouble with the cross slide, he thiought that maybe the nut was warn, but when we pull it down, the nut was OK, the lead screw looked like a warn out Whitworth thread, the soft nut had picked up grit, and lapped the steel screw, he was all for using the old nut on a new screw, but he went to the shop that had in years gone by had been the Myford agents in Christchurch, and one of the older shop assistants found one in the stores dept, It was labled 2 pound 10 shillings, so we got it for $5, lead screw and nut. The lathe had from new been used in a country garage, and had suffered from a lack of maintainance. Ian S C

[Ady1Participant @ady1]

"Make your own nut and see how it goes".

Nice one. I wonder how many beginners have a 3/8" Acme tap on hand?

—–

Don't use a tap

Make a nut on your lathe

Practice with delrin and aluminium which are very easy to machine

A delrin one is good for about a month on a cross slide

I've been using a home made aluminium feed nut on my leadscrew for about a year now

Can't even remember whats in my cross slide now, it's been there for so long

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

You can do a temporary improvised emergency repair that lasts for years on a worn Myford feed screw nut by simply scrunching the nut onto the screw .

Just scrunching works but cut a fine axial slot BDC if you want a class job .

[Ady1Participant @ady1]

If you use your lathe a lot you will burn through feed nuts

So learning to make your own will save you a load of hassle and expense

edit:

I think it's a bronze bit in my cross slide, I made the cross slide leadscrew as well, from silver steel

You don't really need to worry about mega accuracy if you use a DRO on your machine because you can use the digital stuff to check the distance moved

So 8 turns on the leadscrew SHOULD be exactly one inch, but the DRO means you can check it and make sure of what's going on: i.e. quantify any errors.

This also means you can check before you cut something like a 17tpi thread

Turn the headstock 17 times by hand and the leadscrew dro should read one inch.

 

Edited By Ady1 on 26/02/2013 11:29:46

[Phil MogerParticipant @philmoger15177]

Thanks again to all the interesting pointers and a particular mention of: "Make a nut on your lathe".

To a beginner like me it's a bit like that response to the question "How do I get to New York at next to no cost?" – Answer – swim the Atlantic.

Or maybe I'm just not even at the beginner level!

[Ady1Participant @ady1]

If you practice with a soft material like delrin you can make a useable cross slide nut in 5 mins

Move up to aluminium and tougher materials as your ability and confidence grows

 

Most feed nuts are made of softer materials by design so that most of the wear is taken by the nut and not the far more expensive and harder to make leadscrew

Edited By Ady1 on 26/02/2013 15:17:00

[NobbyParticipant @nobby]

HI guys
When restoring my S7 Mk1 I made the x slide nut out of brass & the acme thread leaadscrew out of
mild steel. the tap was made from H&T S.S
Nobby

[Ian S CParticipant @iansc]

Ady1, the soft nut theory sounds OK, until some grit gets embedded in the soft material of the nut, it then becomes an efficient lap, and grinds the hard lead screw quite quickly. Ian S C

[MadMikeParticipant @madmike]

At the prices quoted by Myford I really do not see the point in trying to do a bodge job by messing about with Delrin, or other random materials. The lathe is presumably an essential part of your workshop, so for what is by any stretch of the imagination a cheap item treat yourself to a matching screw and nut. Remember that if you have power feed then you must buy a matched set.

If you do the job this way you can really maximise your effort in the real issues of turning and/or model making.

Other opinions are undoubtedly available, but that is my 2 Drachma.

[Phil MogerParticipant @philmoger15177]

Are the (non-power fed) screw and nut matched?

The ads state only that the power-fed screw and nut are matched, implying non-matching of the manual fed unit.

If they are not matched, I am tempted to buy just the nut in the first instance.

And how does on machine a 3/8" acme thread in a nut with apparent ease? What size the boring bar? Remember this is in the beginner's section so forgive any obvious ignorance on my part.

[NobbyParticipant @nobby]

As I said before I made a tap with ss h&t . when using again it broke so what I done after a resharpen put it in the toolpost like a boring bar and srewcut the next nut I made . to make a cutt not under power I  used a mandrel handle having retracting the tool after first cut just reversed the lathe by hand with the handle . with half nut still closed and put the next cut on using the x slide etc It was a good question Phil thats how we all learn from each other on this forum .

Nobby

Edited By Nobby on 27/02/2013 16:44:08

Edited By Nobby on 27/02/2013 16:44:58

[NobbyParticipant @nobby]

Hi Again
Here is the tool from broken tap for 3/8" x 10 tpi acme form Its a bit worn now

Nobby

[Author]

Posts