Lathe halh nuts

This topic has 29 replies, 9 voices, and was last updated 24 December 2012 at 08:53 by Joe M.

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15 May 2012 at 19:27 #22103
Joe M
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@joem
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15 May 2012 at 19:27 #90908
Joe M
Participant
@joem
Hello.

I have bought a pinnacle 918 hobby lathe, very accurate, but the half nuts have been worn so badly that theres no thread in them at all. I have ordered some new one from the supplier, but they can't tell me about delivery or anything, I was looking at the old worn ones which are made from aluminium and it accured to me maybe I could get these nuts made from cast iron or with a little help maybe make them myself.

Year of manufacture 1978

Anyone help!

Joe M
15 May 2012 at 19:53 #90909
Les Jones 1
Participant
@lesjones1
Hi Joe,
Have a look at the thread "Lead screw nuts" This should give you some ideas on how to make some new ones.

Les.
16 May 2012 at 22:04 #90973
Joe M
Participant
@joem
Hello Les.

I've just sent you a posting thanking you for your advice. I don't know if I pressed the wrong button or what happened. So I'll thank you again.

I've looked at the web sites which have given me some ideas and need to learn more about the processes.

Once again.

Thanks Les.

Joe M
19 May 2012 at 10:06 #91151
Joe M
Participant
@joem
Hello.

Can anyone give advice on good indexable turning tools with 15 / 16mm shanks suitable for small

pinnacle hobby lathe. reasonable prices.

Many thanks.

Joe M.
19 May 2012 at 10:56 #91153
Russell Eberhardt
Participant
@russelleberhardt48058
For your 918 lathe advice it's woth looking here: **LINK**

The 918 and 920 are virtually identical.

Russell.
20 May 2012 at 16:23 #91247
Joe M
Participant
@joem
Thanks Russell.

Food for thought.

Joe M
31 October 2012 at 22:22 #102427
Joe M
Participant
@joem
Hello. I'm still looking for hobby lathe half nuts for my Pinnacle hobby lathe.I'm going to have one last go at finding a manufacturer / supplier before making them myself. Some people have been kind in offering advice on how to repair them useing various compounds but the nut wall thickness is so small I feel it might not be strong enough to support the new inserts. Is it possible to find a good supplier at a reasonable price.

Any help would be appreciated.

Joe
31 October 2012 at 23:00 #102430
Ady1
Participant
@ady1
I made one in T6 aluminium for my lathe, fine after about a year so far

If you're stuck make one from delrin then make an aluminium one with the delrin one

Improvise

A basic leadscrew nut is a doddle to make because it's exactly the same TPI as the leadscrew

I burned through two new ones in 12 months on my 3.5inch hobby lathe because they were made of what seems to be an extremely soft bronze

I presume this is to minimise leadscrew wear

Once you learn to make your own it's a doddle, you need never worry again

Edited By Ady1 on 31/10/2012 23:03:43
1 November 2012 at 20:47 #102482
Joe M
Participant
@joem
Thanks Ady.

Where would I get delrin from? and what is it? You advise making an aluminium set from the delrin,

How do I do that? Really interesting.. I'll consider anything, it's all new to me.

Thanks again.

Joe
1 November 2012 at 21:46 #102484
Andyf
Participant
@andyf
Delrin is a trade name for one type of acetal plastic, Joe. Acetal is engineering plastic, used (for example) to make the change wheels for small Chinese lathes. It can be had from many of the places which sell metal to the hobby, and can be found on Ebay, too.

Here's a thread on making a nut from it "the easy way" link .

Andy
1 November 2012 at 22:13 #102487
Joe M
Participant
@joem
Thank you so much Andy. ( I think I spelt your name wrong the first time)

I'm going to have a good look over the weekend at the sizes and hopefully buy some Acetal to get

this job started. Im looking forward to this interesting task. Maybe I'll contact you for some advice.

kind Regards.

Joe.
2 November 2012 at 00:14 #102492
Andyf
Participant
@andyf
Joe, it's just something I've seen on the Internet but never tried myself, so I can't really offer any advice. The only half nut I've ever made was in brass to fit a baby lathe which had a solid nut before, making the saddle a pain to wind along the bed.

That said, I doubt if making the thread will be the hardest bit. Each of your half nuts will have dovetails or something so they can slide in and out of engagement, and some sort of slots or pins to link up with the cam action lever which operates them. A milling machine may be needed to create the dovetails (or whatever).

Andy
2 November 2012 at 13:10 #102516
Ex contributor
Participant
@mgnbuk
As the 918/920 lathes are Emco Compact 8 clones, would the Emco parts not fit ?

Pro Machine Tools list both metric and inperial half nuts here :

http://www.emcomachinetools.co.uk/EnterShop/tabid/268/List/1/CategoryID/62/Level/a/Default.aspx?SortField=UnitCost+DESC%2cProductNumber

They also have a parts lsiting for the Compact 8 that shows a sketch of the parts.

HTH
4 November 2012 at 10:26 #102721
Joe M
Participant
@joem
Hello Nigel.

Thank you for trying to find the right parts for my Pinnacle hobby lathe. I have left a message with pro machine tools and I suspect I'll hear something tomorrow monday 5th. I did go on the Emco site and brought up various drawings of the half nuts, but there different to mine. There's have a slot cut down each side where lt looks like a retainer strip must locate, where the set I have are dovetailed.

Thank you for trying to help.

Thanks

Joe
4 November 2012 at 15:51 #102755
Russell Eberhardt
Participant
@russelleberhardt48058
The dovetails are fixed to the apron with a couple of screws so it should be relatively easy to make and fit the other type of guide. Easier than making new leadscrew nuts at least.

Russell;
4 November 2012 at 16:17 #102758
Ex contributor
Participant
@mgnbuk
Thank you for trying to find the right parts for my Pinnacle hobby lathe

Pinnacle is a brand name used by Excel Machine Tools, Coventry. When I was first investigating getting a small lathe for home use, the Excel Pinnacle 918 was one of the machines I considered. As it happened, I ended up with a Boxford CUD followed by a Super 7. But I have always liked the look of the Emco machines and have a Taiwanese FB2 clone milling machine.

http://www.excelmachinetools.co.uk/contact.html

Have you tried them directly ?

Regards,

Nigel B.
4 November 2012 at 16:32 #102759
Another JohnS
Participant
@anotherjohns
There's also the Grizzly G4000 lathe:

http://www.grizzly.com/products/9-x-19-Bench-Lathe/G4000

Check that one out.

BTW – the belt idler for headstock drive on the original Compact-8s have friction bearings, looks like the "clone" has improved roller bearings. I have bearings to re-do TWO Compact-8s, as the bearings (or, shafts) wear, and loud rattling occurs. I've fixed one once, now to try doing the rollers…

Another JohnS.
4 November 2012 at 22:13 #102793
Joe M
Participant
@joem
Hello Nigel.

I have been waiting for six months or more for information regarding the half nuts and I'm always fobbed off when I chase my order at Excel. The Emco does look strangly like the pinnacle. I checked the Half nuts drawing out on the web site and they are different, and maybe they could be altered / adjusted to fit my lathe eventually. Maybe thats the way to go if I cant get Acetal to work.

Thanks again.

Joe M
4 November 2012 at 22:27 #102795
Joe M
Participant
@joem
Hello John.

Thank you for the info and link to grizzly. I Checked the site just now. The G400 lathe looks exactly the same, in fact, I have the original instruction manual / service parts list for the pinnacle and it's exactly the same as the G400 on the grizzly web site, even the same part numbers are listed with identical drawings of the various components. I'm thinking, could this be the actual replacement parts. I'll contact them within this coming week and ask for actual half nut sizes to compare.

Thanks again.

Joe
4 November 2012 at 22:40 #102798
Joe M
Participant
@joem
Thanks Russell.

I have actually thought of maybe altering / adjusting Emco half nuts to suit my Pinnacle lathe. I am considering useing Acetal but worry the half nut wall thickness is so thin it might not be strong enough to support the acetal inserts, so this is a real possibility.

Joe
13 November 2012 at 21:36 #103608
Joe M
Participant
@joem
Hello. I have been able to acquire a pair of Half Nuts for my Hobby lathe. Thanks to everyone who offered advice and help. The ones I bought are aluminium and I look forward to trying to fit them over this coming weekend and if not, over the Christmas holidays.

If anyone has ever repaired / fixed half nuts on a similar lathe, I would apperciate any advice on how to re-assemble.

Many thanks

Joe M
13 November 2012 at 23:27 #103618
MICHAEL WILLIAMS
Participant
@michaelwilliams41215
Hi Joe ,

Before putting new half nuts in place you really need to find out why the original set wore out so completely and so quickly .

There are many possible reasons but these are some of the most common :

Rough lead screw – go over the whole length of yours both with finger and visually with a magnifying glass . Identify and polish away any burrs , rough bits and gouges .

Engaging half nuts at random positions either without using indicator at all or with misaligned indicator . This means that on every engagement chunks of the nuts get chopped away .

Overtight gib strips on saddle so that big forces needed to push it along .

Over heavy cuts on a regular basis .

Lack of effective swarf protection and/or inadequate lubrication .

Regards ,

Michael Williams .

Edited By MICHAEL WILLIAMS on 13/11/2012 23:32:23
14 November 2012 at 00:50 #103623
Andyf
Participant
@andyf
Hi Joe,

As they say in the car manuals, re-assembly is the reverse of disassembly .

I don't know your lathe at all, but on mine the procedure is to put things back together and then move the leadscrew up, down or sideways until the half nuts will close easily on it at the headstock and tailstock ends.

Up and down is dealt with by loosening the leadscrew bearing block fixing bolts at one end, clamping the half nuts up at that end, then tightening the bolts up. If the leadscrew doesn't rotate freely, the holes in the bearing blocks may need enlarging to allow a bit of wriggle room. Then repeat at the other end of the leadscrew.

Sideways adjustment can be accomplished, if there is sufficient wriggle room on the bolts which hold the apron to the saddle, by loosening them, closing the half nuts, and then tightening the bolts up again. If that doesn't work, shims behind the bearing blocks, or skimming a bit off their backs, may be necessary.

You can often diagnose what treatment is needed by closing the half nuts half way along the leadscrew, while observing closely to see if it flexes at all. If so, the leadscrew will be put under severe strain when the carriage gets near one or other (or both) of the bearing blocks.

Andy
14 November 2012 at 08:28 #103632
Ex contributor
Participant
@mgnbuk
I have been able to acquire a pair of Half Nuts for my Hobby lathe

Out of interest & for the benefit of others who will eventually be in the same position, where did you manage to source the replacement parts, Joe ?

Nigel B.

(I would have italicised the quote, but the "editor" won't let me ?)
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