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Grinding a steel bar to create a lathe ways scraping reference

Joined
Oct 10, 2017
Looks like I can't get a good 3' long camel back scraping reference for under 300$. And as a home hobbyist, that's pretty steep. It would require getting a reference granite plate too that's at least 3ft wide or long to even scrape in a used one, which means also a boat load more money.

Enter the idea. I was going to take a stock bar of cold rolled or hot rolled steel and have the surfaces ground to create a long bar that I can use as a reference to scrape the ways. I would send the bar to a local shop to be ground on a machine, which would save me money. And I could buy a smaller reference granite plate because for the most part, my projects won't come anywhere close to that 3ft width.

So...which kind of steel should I use? Cold rolled or hot rolled steel? And, does this seem like a good idea? The machine shop I'm going to use guarantees parallelism/flatness to within .0001" with a surface finish of 8 micro-inches.

If I get enough feedback to go ahead with this, I will give it a shot and post updates of my scraping progress for others to follow.
 
They make shafting material that is already turned, ground and polished. Commonly referred to as TG&P. It comes in many grades far better than hot rolled or cold rolled steel. Shoot, you can even get “chrome rod” used for linear bearings. Any of these options will be way better and likely cheaper than having a shop custom grind some crappy low-grade bar.
 
They make shafting material that is already turned, ground and polished. Commonly referred to as TG&P. It comes in many grades far better than hot rolled or cold rolled steel. Shoot, you can even get “chrome rod” used for linear bearings. Any of these options will be way better and likely cheaper than having a shop custom grind some crappy low-grade bar.
You do understand, he's talking about making a master straight edge?
What makes you think a bit of TG&P round bar, makes a master reference? Short of dowel pins over micrometer, I've never used a round master. Incidentally TG&P / Thomson Rod has no tolerance for straightness.

Why are you here?
 
Forget making anything really precise out of steel bar, especially something like a straight edge, unless you are really experienced.

When I was young and foolish I tried milling a 4 ft length of 1.5" X 1.5" mild steel bar to hold a " Vernier " scale on the cross travel of a Hor bore. It's the sort of thing you only do once, it bent like a banana in both planes once I released the clamps !

When I first posted on here I thought engineers were just normal Joes. Some posts on here ( wobbly drills ? ) make me I realise we are all geniuses.

Regards Tyrone.
 
The machine shop I'm going to use guarantees parallelism/flatness to within .0001" with a surface finish of 8 micro-inches.
Pure Bull Shit. 3 foot long, and they grind within a tenth? That will be the case until they turn the magnet off. Then it will bend like a banana. There's a reason the rest of the world uses seasoned, weathered, stress relieved cast iron castings.

Your being feed bull shit, if they are claiming 0.0001" in 3 foot, (Exception DMF Tom). He seems to split the atom.

In summary. No one's ever done shit with steel masters. They're a prickle thumbfest at best. Doesn't scrape for shit.

And your at $300 per 30 inch, and that's too expensive? Thats $10 bucks per inch.

No offence, but given the "Eclectic_Hobbyis" handle. Are you sure you are in the correct place

The Hobby-Machinist Forums

Richard King still does some pro - bono work down there.

That wont change the fact, steel masters are lame.
 
Indeed I am a hobbyist. Just a hobbyist, and I have a 100 year old south bend that I want to restore to working condition (within my means). That said, even a professional business would avoid unnecessary costs if they can still produce an equivalently quality product. But if this post was officially in the wrong place then I apologize. That said, thank you Richard for the link to the Dura-bar info. And I'm grateful to everyone who pointed out that the steel won't scrape well and that even if I send it in to be ground it'll bend because it hasn't been stress relieved. I had thought grinding to be less intensive on the metal than milling but oh well.

If I get a Dura Bar, they offer a few treatment options for the G2 Pearlitic Iron including stress relief, normalize, and annealing. I'm thinking I need to select stress relief and grinding?
 
Why not seek out the correct tool,

It seems there are folks who have used ones as well as new and unfinished castings that could be considered as starting points.

Consider the job as well...The target of the project must be worthy of the tool..Meaning it must be something that can benefit from the use of the tool in proper hands and there are a lot of tasks to be done to make it complete.

A plan may be to attend one of Richards classes to get a better understanding of everything involved then continue from there.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk
 
A solid round or square bar would make a poor choice for a straight edge of any length vs section. Tube round or square is better but stills sags more than you want. Rectangle tube or I beam shape a little better yet but not really there. A triangle weldment, normalized, carburized, quenched & tempered very good (but really heavy).

The cast straight edges mimic the I beam or “triangle like shape” and stay stable when handled correctly.

If you prop up a “perfectly ground” 1 inch dia. by 3 foot long solid steel bar on the ends the center will droop around .00038” at the center (near ½ thou low…) tubing will be about ½ that bad (still not really cool for this purpose).

Good luck,
Matt
 
Why not get the bed of the south bend ground or planed and eliminate all this hassle. Call around to the local grind houses and rebuilders and get a quote. Their cheaper then you think. I am planning on a scraping class at John Saunders in Ohio this summer. He has some great info on scraping on You Tube. His name on there is NYC CNC. One is "what is scraping".

Come to the class and after you get the bed ground I can teach you how to scrape the rest.

If you buy dura bar, I buy # 2 gray iron sawed and It doesn't move on me, never get it stress relieved as it is extruded and is stressed in the process. But IMHO get the bed ground as Southbend's double V's are a nightmare to scrape and I have been scraping for 50+ years. Phil...you would be amazed as to how many hobbyists want to learn to scrape. :-) Rich

PS: Call ED DYJAC or ESDYJAK CO in Milford MI and ask him who is a good rebuilder as he is the DAPRA rep (scrapers) in MI and knows them all.. His Dad was a rebuilder for Pratt & Whitney. He doesn't rebuild, but he sells rebuilding tools.
 
I can't seem to find a machine shop in Michigan willing to grind my bed yet, which has lead me to this means of thinking. Most of the grinding shops near me or those that I get into contact with seem to not wanna tackle those v ways but I'll keep trying haha. And I'm an avid viewer of NYC CNC's vids, that guy's love of machining is contagious.

But say I do get the bed ground, can I bring the bed/ways/headstock/saddle to the scraping class in Ohio? And how much do classes cost? I have my own scraper already, an Anderson from Ebay, but no power scraper (I saw people using them in videos of the class).

And if I do get the bed re-ground, is it a good idea to get the saddle/head stock/tail stock ground too? Those look like they're in decent shape. Especially the underside of the head stock. The tail stock I have isn't originally with the lathe (got really lucky and found a wide 9 tail stock on ebay).
 
Looks like I can't get a good 3' long camel back scraping reference for under 300$. And as a home hobbyist, that's pretty steep. It would require getting a reference granite plate too that's at least 3ft wide or long to even scrape in a used one, which means also a boat load more money.

Enter the idea. I was going to take a stock bar of cold rolled or hot rolled steel and have the surfaces ground to create a long bar that I can use as a reference to scrape the ways. I would send the bar to a local shop to be ground on a machine, which would save me money. And I could buy a smaller reference granite plate because for the most part, my projects won't come anywhere close to that 3ft width.

So...which kind of steel should I use? Cold rolled or hot rolled steel? And, does this seem like a good idea? The machine shop I'm going to use guarantees parallelism/flatness to within .0001" with a surface finish of 8 micro-inches.

If I get enough feedback to go ahead with this, I will give it a shot and post updates of my scraping progress for others to follow.

.
you can buy precision ground flat stock in 18, 24 and sometimes 36" long lengths. it aint going to be accurate to .0001" but better than cold rolled.
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you can buy linear bearing rails already hardened and ground i believe 6 foot is possible. usually they bolt on and need checking to make sure they are straight and dont have a minor curve. i once aligned a linear rail to concrete floor with optical alignment equipment to .001" per 6 feet. next day it was bent like a banana. colder concrete and warmer steel rail expending at different rate. longer steel rail compared to concrete floor needed to go some where so bimetallic action it tends to bend. day after it was back to being straight. having it under a skylight window maybe not the best ideal. rail was measuring a 20 ton cast iron wheel 18 feet in diameter. the rail needed to be at that spot. not like we were going to move 20 ton wheel. other option was cover up the skylight so sunlight dont shine through
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by the way steel ground to 8 micro inch can rust in 24 hours if not protected. usually got to spray stuff on to protect from rust
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buy linear rails and shim and align straight. but they are not cheap. might find you can buy a used lathe for the price of new linear bearing rails
 
That's an interesting thought. I do have some HIWIN rails for a DIY 3D printer project, but the longest is only 500mm. I'll keep that idea in mind.
 
To the OP, if money's a concern, it's usually cheaper to do things right the first time rather than having to repeat. If industry uses cast iron camelbacks, don't you think natural selection weeded out the other options as unworkable? Watch ebay and this site- medium sized straight edges to show up from time to time at very reasonable price.

L7
 
That's an interesting thought. I do have some HIWIN rails for a DIY 3D printer project, but the longest is only 500mm. I'll keep that idea in mind.

i saw a factory where the had linear rails on steel beams for a mill over 20 foot long and rails were set straight with optical alignment equipment
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if you have 2 each .03mm feeler or thickness gage stock thats .0024" and on other end if you have .0010 and .0015" thats .0025 or .0001" difference
.0010 and .0012 thats .0002" difference
.0012 and .0015 thats .0003" difference.
.
you can shim linear bearing rails. its time consuming and temperature changes can effect straightness. many linear rails are made to go end to end for longer travel and or you can buy longer lengths of linear rail.
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but dont be surprised if its easier and faster to buy a used lathe. a large factory buying in bulk can manufacturer in large quantities far cheaper than a person can make one of something with crude equipment. also a well designed machine usually better than home made design
 
If this is just for hobby work, how bad is this machine worn that you feel it needs to be scraped? I can understand the need if you were planning to make parts with .0001 tolerances, but few hobbyists work to that level of precision, and I'm guessing more than a few of us have run old worn out machines and still made parts to spec, you just have to creep up on those final cuts.

Unless that machine is so swaybacked that you can see it from across the room, put it back together and make some chips, if your part comes out off dimension you can blame it on the machine. With a perfect machine, if your part finishes off dimension, there is only 1 person left to blame:D
 
i saw a factory where the had linear rails on steel beams for a mill over 20 foot long and rails were set straight with optical alignment equipment

Jesus bud, how far off in the rhubarb can you get? The guy's talking about scraping a 36" long South Bend lathe. What does linear rails on a 20 foot machine have to do with anything?

To the OP, you can buy a cheap Chinese granite parallel that will be plenty flat for your needs. Shars shows 24 and 36 inch versions for $250 or $380, but currently they seem to be out of stock.
 
I second the comments of several posters who insisted on two things:
1) Evaluate if the level of wear justify the effort of planing/grinding and rescraping the bed.
2) There aren't shortcuts to the proper equipment: it's better to start accumulating and making tools that you could need for your scraping job(s), then tackle first the jobs proportionate to your tools. If you figure out that scraping is not for you, you can easily get your money back by selling the tools that you've accumulated waiting patiently for the right deals.

One thing I've learned is that a too big surface plate almost doesn't exist: if you invest in a small one, you'll soon realize that you need a larger one.
Probably a few members would disagree with me, but I would prefer a larger "B" grade plate to a smaller "A" grade plate: for the precision required for most of the hobbyist scraping jobs, you can cover over 95% of the needs with a large "B" grade plate. It's not too hard to "map" a plate and identify the best and worst areas.

Regarding scraping the bed of a South Bend and pretty much any small lathe with tiny inverted Vs, I haven't tried yet, but I have thought about the challenges. Here are my concerns: the Vs are much narrower than most straightedges, making it very easy to "roll-over" while spotting (resulting in convex faces of the Vs). Unless one cuts a relief at the bottom of the V, it is very easy to leave a "shoulder" at the bottom of the V, where all the scraping strokes end (i.e. similar problem to scraping dovetails). Lastly, by being so narrow, it is rather difficult to hinge the spotting tool and fairly easy to make various mistakes while spotting.

If it wasn't for the issue that it would be fairly prone to twisting, I was going to propose using a thin slab (5/8-3/4x5-6x36 in) of DuraBar, lightened by large holes in the "web". But I like much better Wes's suggestion of using a 36" granite parallel, making sure to avoid the above-listed issues.

Paolo
 
You do understand, he's talking about making a master straight edge?
What makes you think a bit of TG&P round bar, makes a master reference? Short of dowel pins over micrometer, I've never used a round master. Incidentally TG&P / Thomson Rod has no tolerance for straightness.

Why are you here?


I realized that right after I posted it. The OP’s talk of using cold roll or hot roll for some reason made me think round stock. Thought about correcting it, but I figured you guys would be quick enough to point it out.
 








 
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