Making a Gib Strip and Acme Rod Sources?

**Doc Nickel** · 03-26-2009, 02:39 AM

1) No, it's pretty common to use mild steel as a gib strip against cast iron. Cast against cast works (after all, that's what the ram ways are) but there's nothing at all wrong with just making your new one from a strip of mild steel.

2) If it were me, and I had access to a surface grinder, yes, I'd definitely grind it. It'll probably have an odd shape, though, so be ready with a good sine plate or two.

If it's just a flat gib, adjusted by simple set screws in from the side, it'll be easy- and you can probably get away with just milling three sides, and only grinding the one that mates up with the clapper slide.

3) Yes, that sounds okay. I don't know precisely what you're working on, but as long as you make the rod stout- due to the considerable upward force it'll see in use- it'll be fine.

4) If it were me, I'd buy the best chunk of screw I could get, within reason. Ground will be both more accurate and typically smoother, which will help longevity. (Not that it sees a lot of use, but hey...)

She's a monster, and you're working on a rather key component. It's worth splurging a bit on.

Doc.

**Forrest Addy** · 03-26-2009, 07:10 AM

I'll probably chime in on this later but I do want to forcibly assert that it's best to make a tapered gib with extra length for fitting allowance and hand scrape it for full length bearing. You can cut to leength and add djustment features later including gib heads and adjusters by silver brazing.

How is the opposite way bearing? Now is a good time to correct for wear.

**Duffy** · 03-26-2009, 10:02 AM

I am not sure about relative "precision," but Keystone Threaded Products will probably have better selection and price than McMaster-Carr. I just bought some suff from them, and they even had 9/16"-8 LH acme. I think it was about $17.00 for 3 feet. They said ground and hardened, but I have not seen it yet. Just a suggestion. Duffy

**daryl bane** · 03-26-2009, 11:04 AM

Not a expert by any means, but have been successful making a new tapered precision gib. I would use cast iron absolutely. I would mill it to shape and finish scrape it in. Making a prismatic tapered gib(if that is what yours is?) is a interesting machining exercise.

You could grind it but it would probably warp in the process. As usual, Mr Addy's advice is spot on and you will be ahead of the game by taking every kernel of his advice. But making a gib is just a piece of the accuracy puzzle if you are going for a proper job.

**lazlo** · 03-26-2009, 11:46 AM

Keystone only sells low-precision rolled acme thread intended for jackscrews: +/- 9 thou per foot. You'd be a lot better off with the precision acme thread from MSC or McMaster, which isn't a whole lot more expensive, and even cheaper if you catch them on sale.

As far as the gib, like Doc says, mild steel, cast iron, or even bronze would work. I'm not sure about a tool steel gib. I know some machines use them, but I think that's against a hardened dovetail, like the Hardinge HLV-H.

**Fasttrack** · 03-26-2009, 12:59 PM

Thanks guys. I don't mind "splurging" so long as I know the money is going somewhere worthwhile! I'll take some measurments of what's left of the gib. Unfortunately, I only have the slide with me. The rest of the head is still on the ram about 5 hours away. I still need to clean it up good with some scotch brite, but after I do, whats the best way to assess the wear?

Forrest - Please do chime in when you've got some time!

edit: Question about the threaded rod - I'll definitely get one of the "precision" threaded rods, but should I get one out of alloy steel or one out of regular 1018 carbon steel? I have to machine a keyway in the threaded rod for the auto-downfeed feature, and I'm not sure how difficult that will be to do if the screw is "alloy steel".

**pcarpenter** · 03-26-2009, 01:41 PM

Warning Will Robinson

I appear to have bailed out and restarted before I submitted what I typed....argh... I went to check to see keystone's web site because I was pretty sure that they made some higher precision threaded products. Their site appears to have been hijacked and my AV immediatly grabbed and quarantined two threats. It was clear that I got a redirect to a site that loaded a fake AV warning in the browser window...which is the mark of one of the threats. Anyhow, do not go there for now.

What I wrote before was that likely even the low-precision threaded rod will account for less runout than his worn feed nut. This is not a feed rod, but rather an adjustment for the feed depth. It adjusts one direction, so minor looseness is not that critical.

Same for the gib, fortunatley. Its not a way surface in the traditional sense, so likely an imperfect fit will be OK...which is good since you may not be set up to scrape everything back in. Grinding a tapered gib and getting a good fit can be difficult even if you have the luxury of grinding the mating surface. Take away that ability and about the only practical solution is to scrape the two to match, or to machine until they are close and call it good. The latter would not be so great in so far as a working way surface....you see milled ways (with some fake "flaking" to make people think they were then hand scraped) on some cheap import stuff. On the other hand, this is just a tool adjustment slide and it does not require the precision that a working way surface would.

Paul

**lazlo** · 03-26-2009, 01:49 PM

Originally posted by Fasttrack

should I get one out of alloy steel or one out of regular 1018 carbon steel?

The alloy steel is usually 4140. Based on your description and Paul's comment, I don't see any reason why you'd want/need a high-tensile/hard leadscrew. Those are really intended for a hardened (aluminum bronze) nut.

**Tinkerer** · 03-26-2009, 03:20 PM

Fast... I made a new gib for my Atlas shaper some time back (posted on in with pixs) out of bronze. It's been working great. As for the acme rod 1018 should work just fine as well as a harder rod can promote more ware in the nut.

**lazlo** · 03-26-2009, 04:02 PM

Originally posted by Tinkerer

As for the acme rod 1018 should work just fine as well as a harder rod can promote more ware in the nut.

I've asked that question on PM, but never heard a good answer: if you use a softer material for the gib than the way itself, following lapping rules, won't the grit embed in the softer part, and wear the harder part (the way)?

So by extension, does that mean that a hardened gib would be good, since the grit would embed in the way, and abrade the hard gib, instead of the opposite?

**Fasttrack** · 03-26-2009, 04:07 PM

Thanks Tinkerer! I'll do a search and see if I can turn up the thread.

Paul, I think your right. I looked at MSC and their "precision ground" screws are made by Keystone, along with the rolled thread variety. I didn't think the gib would have to be too precise, either. But then, I don't really know much about shapers. I don't have the nut here with me, but I'm hoping I can make a replacement for it, too. Maybe a steel body and then press in a pre-made bronze nut.

Robert, thats good to know! Not only is the 1018 about half as much as the 4140, but it ought to be alot easier to mill a 1/4" keyway in.

**Tinkerer** · 03-26-2009, 06:51 PM

Originally posted by lazlo

I've asked that question on PM, but never heard a good answer: if you use a softer material for the gib than the way itself, following lapping rules, won't the grit embed in the softer part, and wear the harder part (the way)?

lazlo... we are talking about things that make chips... grit should no be a big issue. I removed my gib and inspected it it has no measurable ware on it and the matting surfaces are perfect. I never like idea of lapping in mating surface as in get a mill or lathe and a tin of grit and do the push pull till it's a shinny surface. You can never really clean all the compound off. Bronze is used as a bearing on hard shafts all the time with no issue.

Originally posted by lazlo

So by extension, does that mean that a hardened gib would be good, since the grit would embed in the way, and abrade the hard gib, instead of the opposite?

Why would it be a good thing to ware the way... which is way harder to repair then just replacing the gib strip which is an adjustable sacrificial piece? Wait I read that the wrong way.. and see what your saying but I think we are pointing in the same direction. I guess it the old chicken and egg thing... best to move the grinder away from the machines.

**Fasttrack** · 03-26-2009, 09:46 PM

Personally I don't think it should matter. In fact, I would tend to think that a harder gib would be better like Lazlo suggested. After all, there *should* be a film of oil between the two surfaces at all times. That's why you use way oil and not chain saw bar oil or etc...

Besides, the ways wear regardless of the material for the gib.

i.e. a bronze gib clearly works well, but it's not going to protect the ways from wearing since it only contacts one of the 4 bearing surfaces.

**Fasttrack** · 03-26-2009, 09:56 PM

A problem?

So the little stub of gib may be too short to get a good measurment for the taper. Any suggestions on how to handle this issue? I guess I need to take some careful measurments of the dovetails and try to work out what the gib strip needs to look like?

<sigh>

Making a Gib Strip and Acme Rod Sources?

Making a Gib Strip and Acme Rod Sources?

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