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Remachining pacemaker compound

Ianagos

Stainless
Joined
Sep 23, 2014
Location
Atlanta
My 73" pacemaker was pretty well worn when I got it but the worst was the the compound it looked like it had been used hard and sat in coolant and it just rusted away. But anyways it's always difficult to cut good tapers with it. A while ago i just machined it a little but didnt touch the dovetails and I probably only removed 10 thou from the flats of the female dovetail and same from the top of the male and it's still pretty bad.
So can anybody help instruct me on how to remachine the thing because I really have no experience in this and I might just screw it up worse. I may scrape it but I don't know how and neither do I have a surface plate but I do have the other stuff and could probably whip up a copy of a Anderson scraper as I have a bunch like several pounds of random carbide blanks. But I mostly want to learn how to machine it on the mill I think I can probably find the scraping info otherwise but if you would like to pitch in any help is appreciated.
I will add photos when I can.

So can anybody give me a guide on how I should go about this? I have a excello knee mill. ImageUploadedByTapatalk1429740021.349728.jpg
The top of this surface also got cut
ImageUploadedByTapatalk1429740068.061089.jpg
The blued surface got cut
 
Don't machine it! It needs ground and scraped. If you don't know how, have it done by someone that does. Or learn how to do it yourself.

It was machined when new, it isnt hardened, machining should be fine for a light clean up so you can scrape it to fit. I think the first order however would be to do some measurements and checking to see if that much really needs to come off first. Your photos are not clear enough to show how much wear there is. Only when you know where it is off and how much will you know the best way to attack the issue.

There are several people near Atlanta who attended Richards scraping class held here. Any of you wish to have a look at his parts for him and offer advise?

Charles
 
You need to get you some feeler gauges like a .001", .002" in thicknesses up to around .010". Try to insert between the two slides when it is assembled. See if you can get them to go in especially at the end that sees all of the wear, tool post end of the compound. If they go, keep increasing the thickness until you get a thickness that will not go. This will give you a general idea of how much wear you have. If you cannot get a .001" feeler to go in anywhere. Leave the slides alone!
 
There is almost 15 thou of wear in the middle ill draw a diagram of it when I have time. I am not gonna waste time scraping all of that wear when I can machine it and then only scrape 1 thou or so. It's worn to the point to where the slides fit each others but are roundish so they don't really move when the gib is tightened.
Moonlight machine: I disagree with what you say I think it needs to be machined first there was not a sing surface that was worn less than 10 thou. So I think if I scraped all that I would be wasting time and as far as getting it ground can you recommend a shop that can grind dovetails.
 
shapers are ideal for work like that. or planers, if the work is a little bigger.

Even the simple, but necessary tasks such as restoring the clearance areas where ways have moved too close together.

smt_planerslide2.jpg


smt_planerslide20.jpg


Planing the ways themselves:

smt_planerslide3.jpg


Doing the recesses necessary to clear a straight edge/scrape into sharp corners.

smt_planerslide4.jpg


smt_planerslide6.jpg


smt
 
FWIW, though, I am kind of ambivalent about machining the actual ways unless like the one photo above there is bad, deep damage in one area. Most ways are banana shaped one way or the other. If the clearances are machined open, it is pretty easy to scrape the actual way straight down, or to bias it in one direction or another to recover geometry.

Each case is different, and depends on an accurate thorough inspection and assessment of where the ways surfaces need to move, before scraping or machining. I'll often scrape .015 off the high ends, or high center of a way before machining just because it is faster than trying to set up to machine much closer.

smt
 
What tool you use makes little difference, although the shaper is an excellent and traditional tool for this kind of work. It is not the size that must necessarily be accurate but the Geometry. Geometry is what matters here more than anything else. Those surfaces that should be parallel and straight need to be made that way. Other surfaces, like those on a tapered gib must match up well enough to maintain that geometric relationship.

I am sure there is someone around ATL that will be willing to offer a little time to help you out with this. Of course the offer for you to visit is still open with me.

Charles
 
Stephen hit the handle on the head or how ever that old saying goes...lol, but not many planners or shapers are as heany as they once were. You can look on Ebay and find a dovetail cutter to mill it. 50 degree's or 45 degrees. Mill it, or if your good you could tilt the head, indicate the dovetail and fly cut the dove (both sides) and the flats all in one set up. But 4GSR makes a good point as what ever you remove you will need to either epoxy on a shim like turcite, rulon or phenolic to compensate for the original .010 and what ever you take off now. Remembering the minimum most rebuilders put on is .047" plus .005" for the epoxy. So once you scrape it, you have at least .040" left.

So you will have to machine off more cast iron material. 4grs is trying to tell you to shim the flats and dovetails and gib so when you screw the compound screw up close to the bracket it does not bind. If you only machine off metal and not bring it back to the "original center line" it will bind up when you screw the nut to the solid ens of the screw or normally it is on the operators side.

You should be able to do this if you play detective and have a plan. Many old war machines were not scraped, they were planed and stoned, so if your not a great scraper, don't get to upset about it.

We can help you learn to scrape, but think of how many years the machine and compound ran after the wear and the scraping marks wore off. Think about it. Rich
 
Well I shouldn't have to worry about the centerline of the screw because the nut is fit into a bore and can slide up and down. I am mostly worried about the gib. I don't know how to make a good gib and the original probably won't fit after the machining but the original is all beat up anyways. You guys have convinced me and this weekend I plan to remachine it. The bottom I plan to turn as that's how it was done originally I just need to figure out the no compound situation to do that. Or maybe ask Charles if he has a lathe capable. I do have a dovetail cutter that I think is big enough (provided the angle is right). One question though is how should I go about cutting out the relief. Would I be able to do it in the same setup? Or should I do it in another setup. If so how should I set it up. I'm thinking tiled head and slitting saw or small endmill.
 
Stephen hit the handle on the head or how ever that old saying goes...lol,

:D

Richard, I've been known to hit myself in the head with the handle too; but never gonna admit it here, in this crowd. :)

Ianagoes, if you are going to build back up with rulon or similar (I have absolutely -0- experience with that) you will not really need to improve clearances because the add-on way material will take things back to near new relationships.

smt
 
Rather crude, but vary effective. I used a hack saw and file to relive the corner of the dove tails on my logan 200. It took maybe 10 minutes of elbow grease, about the same for setting up the mill.
 
That seems like a decent idea and probably what I will do unless somebody gives me a better easy solution.
 
You'll want a little more space than the thickness of one saw blade so you can stack two together in the hacksaw frame. Or if you happen to have a thicker blade from something like a power hacksaw, that would be an alternate tool.

One more alternative is a cutoff wheel in a grinder to whittle into the corner. It won't look nearly as professional as the Stephen Thomas job but once it's assembled no one will know.
 
Don't make the slot bigger then it has to be, its just a place for chips and dust to collect. I don't risk using a hand held grinder to make the slot, too easy to gouge the ways with a slip of the wrist.

Here I had a made the slot with a hack saw, then scraped to the corner with a reground wood chisel.
IMG_2116.jpg
 
I'm maching the bottom right now I'm just turning it on the lathe.

Edit: I'm done came out pretty nice tommorow or something ill cut the dovetail side. The only problem I'm having is on female dove tail I can't cut all the way through with the cutter because the part that holds the feed screw is in the way so I think I'll skim as far as I can then come back with a scraper or something and just cut that little peice out. Ill post pictures later but currently it's not letting me post pictures.
 
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Sitting here and reading this, I hope you understand many of us are professional machine rebuilders or have done this the correct way. We come here to assist first time rebuilders and machine owners, with advice.

No offense, but from what I have read and reading what you wrote, you seem to be hell set on doing it your way and not listening to our advice. A few photo's from you lanagos would help us a lot to understand and prove me wrong. Cutting the bottom on a lathe sounds like a Cluster mess-up. I have never heard of anyone cutting it in a lathe before. If it worked, congratulations, if it didn't, oooooops.

As they say a picture shows a 1000 words. Showing how you indicated and cut it in your lathe and mill as Steven did would help a lot. He gave you and us some super photo's and captions as a guide and show everyone one the right and simple ways to do it. I hope the readers don't end up reading and seeing right way to do it and I hope your way doesn't turn out to be the wrong-way.

Many of us who rebuild machines for a living, hate to rebuild someone else's first time attempt to rebuild like this. It takes 2 times as long to fix up some-else's mess .
Rich
 
:D

Richard, I've been known to hit myself in the head with the handle too; but never gonna admit it here, in this crowd. :)

Ianagoes, if you are going to build back up with rulon or similar (I have absolutely -0- experience with that) you will not really need to improve clearances because the add-on way material will take things back to near new relationships.

smt

I wrote that with jet lag ...lol...daaaa.. "hit the nail on the head" is what I was trying to write...LOL Rich
 
So Richard it came out great as far as I'm concerned much much flatter than it was before maybe it's not surface plate flate but it is close enough considering what it's going on is not very flat. And on the dove tail I will be machining it and then if I'm not satisfied I will be scrapping it in but understand this I am not a professional machine reconditioned so I do not have any of the tooling required such as surface plates scrapers or anything like that. Any well to me it costs the same to have it rebuilt by a professional if I have too whether I did what I did or not. There was no surface that was still flat or machined from factory.
Here is a photo I indicated it from the pin in the middle and the surface.

ImageUploadedByTapatalk1430152273.114266.jpg
ImageUploadedByTapatalk1430152303.663428.jpg
 
I was just concerned if the bottom would be parallel to the top flats. The turning looks good and as I said if it turns out good, congratulations. I can see with the center stud in there, it may have been turned when new. I assumed you used a 4 jaw chuck. You may consider using a fly cutter on the dovetails. You can use a short tool bit and single point it on the side near the nut housing. Rich
 








 
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