# Camelback Straight Edge Scraping



## wcunning (Mar 9, 2018)

I have a 6' camelback that I bought on eBay a while ago with no confidence in its scraped surface -- probably not too far out given that it has been scraped before, but likely not Grade A anymore. My biggest surface plate is 18"x24", so I picked up a 5' granite parallel when it dropped in my lap for reconditioning my straight edges. It's also not particularly recently certified, but it was used by a CMM installer, so I have some reasonable confidence in it.

My question is this: how do you blue/scrape to get a flat surface on a very long camelback when you don't have an 8'x8' plate? I've seen sideways mentions of carefully overlapping passes and checking one half and then the other, but never a real description of how to do it with some certainty. I can scrape for flatness pretty damn well, and I have reasonable measuring equipment, but nothing that I'd 100% trust to do 6' x 2" of a camelback surface. Does anyone have any guidance on this? Rich? 

Thanks,
Will


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## ThunderDog (Mar 9, 2018)

wcunning, I'm DEFINITELY a newbie for your questions.  I'm not sure if any of this helps, but section 9.9 through section 9.13 (pages 54-57) of Connelley's Machine Tool Reconditioning might be a good place to start.  As a beginner, I'll be watching this thread to learn more on the topic.


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## Bob Korves (Mar 9, 2018)

Any precision flat tool that is long and skinny and made from metal is always suspect WRT flatness.  Metal has residual stresses, and it moves over time, even when stress relieved multiple times and properly stored.  It probably should be checked using a oversize high accuracy (AA) surface plate before use each day.  However, the things also move with heating and cooling, and when the temperature is not the same throughout.  If a guy is selling a granite parallel that was used for CMM calibration, I would ask, why did he sell it?  Machine tool repair specialists use smaller plates to test and calibrate longer tools, but also have the knowledge and experience to interpret the prints as they move the longer tool along.  They also do the reverse, use a shorter camelback to test and scrape in a long lathe bed or other surface.  I KNOW that I do not have the skills and experience to do that, and so I would not try to do so on anything important.  In a few weeks I will be attending a Richard King scraping/machine tool conditioning class and hope to start to learn and practice some of those skills.  All I know for sure is that guessing is just guessing, and proof is derived from valid steps of proving the work.


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## wcunning (Mar 9, 2018)

The CMM calibrator was retiring, sold it to a neighbor of mine who used the parallel as the base for an exceedingly accurate autocollimator setup. It's likely not AA, but I'd be pretty shocked if it was below the requirements for grade A. He got rid of it because he, like all of us, needed the room in the shop. Again, not *guaranteed* and *warrantied* but more accurate than my worn out machine tools for sure. 

Honestly, if I could find someone who had a serious granite plate, guaranteed to be A or AA who would let me, I'd go rent time and scrape those straight edges in in a better environment, but I don't even know where to start to ask that question. 

As to temperature, my basement shop is 60*F +/-1*F over basically the whole thing. It gets a bit warmer in the summer, has a bit more of a temperature gradient in the winter, but the duct work for the house runs all through the basement, the furnace is in the middle and the mass of everything averages it all out quite well. I should probably do more testing with the IR thermometer to know for sure that it won't be a major source of inaccuracy, but the machines are definitely more worn than the coefficient of thermal expansion issues I might run into. When I get down to finish scraping in a couple of years on the mill and lathe, I'll worry about making sure that it's done in optimal conditions, but right now it's not too much of an issue.

I'm only 5% better than absolute amateur. I have the proper equipment -- surface plates, camelbacks, Biax scraper and flaker, AccuFinish sharpener, etc -- and I can scrape for number of points. I cannot interpret the bluing with any real confidence, and the granite is close enough to the width of the camelback that I can't do much hinging. That's why I'm trying to get the discussion going and hopefully learn a few things.

Thanks,
Will


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## dlane (Mar 9, 2018)

Quote::Honestly, if I could find someone who had a serious granite plate, guaranteed to be A or AA who would let me, I'd go rent time and scrape those straight edges in in a better environment, but I don't even know where to start to ask that question.

I would think in Detroit there should be someone with a good plate, might post on CL to rent time on one.


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## Richard King 2 (Mar 9, 2018)

I have a ton of chores today and will write more later.  I would build a platform to set the Granite SE on so it sets on the Airy points, so you can rub the SE on it with confidence it won't fall on the floor.  I would also drill and tap a hole in one of the  out side ends so you can hang it and ring it as storing straightedges this way is the way I have found they stay straight better then any other way.   Please post a picture of the SE and a pic of the end before drilling it so we can talk about it.   You will have to lap scrape it. 

Also if you haven't scraped before look at the one post I linked to here about a Studer grinder I taught the owner how to scrape over the internet.  Got to go....Rich

PS:  On the You Tube Show Stefan G who attended the Denmark class last year....he shows you how we rang a straight-edge ,,


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## wcunning (Mar 9, 2018)

It's a 30+ year old Challenge camelback, so I'm not sure it needs much stress relieving or ringing I'd hang it from one of the hand holds, personally. I haven't quite figured out where I'll have space to build a rack to hang my collection of straight edges, since it's a pretty complete collection and thus will take up plenty of space. I'll post a couple pictures of the collection tonight.

I do, sorta, know how to scrape, at least scrape flat and for bearing surface. I got lessons from one of your students, Rich -- OtherBrother from PM. 

Thanks,
Will


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## Richard King 2 (Mar 9, 2018)

ahhh well Daryl can help you out...one of my A++ students....I have seen 60 year old SE's take a set or twist if they are sitting cocked eyes for a while...
When you become a bit more experienced you will understand a ringing helps maintain all straight-edges as the get work hardened just from rubbing them on parts.   I have a few more years experience working with SE's.  You can do what you want, but for others reading this I would hang it and ring it to vibrate the stresses out while scraping old SE's.     Also I have learned over the years hanging them from the holes and not an eyebolt they bend .  But as I said, your choice.


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## wcunning (Mar 9, 2018)

I didn't realize they built up that much new stress from use/sitting, and all the discussion I'd seen on ringing was about taking stress out of fresh castings. I'm always happy to listen to experience. I'm a little unsure how to setup and drill the eyebolt hole in the narrow ends of the simple flat straight edges, as opposed to my dovetail ones. I'll take some pictures this evening, and see where you'd recommend putting an eyebolt/how to drill for it. 

Unfortunately, Daryl hasn't found a place to use a big surface plate on his straight edges either. I should check in with him and see if he'd be interested in looking again. Honestly, I need to get a hold of him and see if he'd be interested in using the big granite parallel to check his straight edges, too, though his longest is 5 ft, if I remember right.

Thanks,
Will


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## woodchucker (Mar 9, 2018)

Sure makes sense that hanging them straight up and down will avoid the gravitational forces and keep it straighter. 

Rich: When you say ringing, are you saying like a tuning fork, or like gauge blocks. I'm taking it that because your talking stresses, you are saying tap it with a brass hammer or something to ring the stresses out.


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## Richard King 2 (Mar 9, 2018)

Tuning fork.....as in ringing a bell vs wringing a gage block.   I usually lay the SE on it's side on a pipe and find the balance point  and drill a 1/4 20 hole and tap it.  If you don't have a lot of storage space you can set them on  felt or styrofoam at 30% out to 25%  on each side of scraped surface.  I just checked and I see Challenge is still in business.  I see they have the wood pads on the back, so you can flip it over and set it on those pads and braced so it doesn't tip over.  http://challengeprecision.com/products/straightedges.html or email them and ask them.


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## Richard King 2 (Mar 9, 2018)

Here is the You Tube showing how Jan S. Rung 2 on the King-Way Brand Straight-Edge and scraping them.   The show was filmed by Stefan G in the Denmark class he attended  the ringing takes place at the 6 minute mark.  You can also see how Jan cleans the dirt off the surface plate with his hands so he can feel the dirt on the granite.  You can also see me wiping the Straight Edge with my hand before he sets it on the plate.  Also see how he "hinges" the SE to see where it is high.  Plus when he flips it over you can see the blue on the ends to support the hinge.  Isn't You Tube amazing!


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## wcunning (Mar 9, 2018)

Richard King 2 said:


> ...find the balance point  and drill a 1/4 20 hole and tap it...



I don't quite follow that -- balance point in which plane/dimension? Is 1/4-20 really strong enough for a 6ft camelback (175~200 lbs, based on how much it sucks to pick up). If it is, then my concerns about having enough meat to drill and tap are largely alleviated. 

I have been keeping mine in cases with Bessel point pads, here they're set out for the picture. I don't have space for those cases long term, nor do I have one for the 6ft'r yet, since that case would be *huge*. I think that hanging is a better long term solution, so once I have a game plan, I'll probably do that. 

Thanks,
Will


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## Richard King 2 (Mar 9, 2018)

It's as easy for you to look up eye bolt specs as it is for me.  
http://www.rigging.net/Eye Bolts.htm
1/4" is 400 pounds, 5/16" is 800 lbs, 3/8 is 1400 lbs.  You can decide on which one is safe for you.
I am trying to educate everyone.  You do what you have to do.  The others reading from the world wide net can do it there way.  I just know I have had 50 years of success doing it my way and over 30,000 students have never told me my methods don't work.


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## ThunderDog (Mar 10, 2018)

So, all of this good information has got me thinking.  I have a straight edge that has a large eyebolt at one end.  I keep it hanging while in storage.  I also have a 4' camelback but it is stored on the bessel pads.  If a proper point were located to hang the camelback by one end would that be a better way to store it?  Just curious.


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## Richard King 2 (Mar 10, 2018)

About 10 years ago I taught a class at Honeywell in Minneapolis.  Back in the 1950's and 60's my Dad did some rebuilding at that plant and taught their men how to rebuild.  I knew that but did not know they had bought a set of his straight-edges.   So in 2008 I got a call from them and asked to come and teach a class there as like many companies they got away from rebuilding  machines when people retired or left the company as this happened to Honeywell all those old timers my dad taught were long gone.

The first day of the class I asked them if they had any straight-edges we could touch up as a project for the class?   One of the students said there were a bunch of them in a closet behind one of the maintenance shops milling machines.  We had to move the bridgeport to open the door.

The foreman said that that door hadn't been opened in 20 year he had worked there.   We opened the door and were shocked.  There was about 15 straight-edges in there hanging from eyebolts.   They had a thick oil on them and dusty as heck.  We pulled out the HK-72 out first.  That is a 72" camel back with no angle.  Looks like your 72" Challenge.   We cleaned it, lightly stoned it and set it on a blued surface plate and it hinged perfect and when we flipped it over it was as good as the day they hung it up in there. We then pulled out the others and they were also perfect.

That is the day I started to hang my straight edges from an eyebolt and tell people to hang them.   Rich

Pictures are KingWay SE's. The one set is in my station wagon I just brought back from machine shop that were sent to Norway. The SE's shown in the Denmark You Tube. I make Camelbacks with and with-out 45 degree angles.   The others are castings I have made and another one I have machined.


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## wcunning (Mar 10, 2018)

I'm still a bit confused as to the balance point you mentioned, Rich? 

I did try to look up the spec, but had a bit of a confusion regarding thread depth/engagement vs. rigidity in cast iron. I get that an eyebolt is good enough to pick up a machine from, but I'm less than certain of the strength of the castings of straight edges that already have chips and cracks off of parts. Particularly when I don't see a spot that I'm sure I can drill with lots of meat around it after tapping.

All of that said, I'd like to reiterate my original question: is it possible to check flatness of a longer part (6ft camelback) from a shorter master (5ft granite parallel)? If so, what is the procedure for doing so? I don't see one definitively laid out in Connelly, though I do see hints that it should be possible.

Thanks,
Will


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## Rex Walters (Mar 10, 2018)

Hi, Rich. Looking forward to seeing you again soon. Now that I’m about to start scraping in one of your 36” straightedges, I need to start thinking about storing it.

Like Will, I’m not 100% sure I understood your description of where to put the eyebolt. Let me know if I’ve got it right:

The goal is to put an eyebolt in one end of the straightedge so that it hangs as vertically as possible. Put the straightedge on its side on a bench. Then put a pipe underneath it as long as the straightedge and parallel to the long dimension. Find and mark on the end of the straightedge where it balances across the short dimension. Drill and tap in the center at the marked location for eyebolt.

Cheers,
—
Rex


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## Richard King 2 (Mar 10, 2018)

Have to be a detective again. First set the Granite on the Airy points or 30% from each end.   What works good in a pinch is Jorgenson 12" 2 screw wood clamps.   2 of them and C -Clamp them to a table.  Then clean the granite and cast iron, stone the SE and use a single edge razor blade  and a couple squirtrs of windex to lightly go over the granite then  wipe with a white cloth or paper towel until it wipes clean white on white.

Then wipe SE and Granite with you hand.  Pick up the SE alone or get some help and slowly set the SE down and listen as it sits down.  If there is dirt on it you will hear a noise like sand under a shoe.  If there is no sound set it down centering SE on Granite  If it's a 72" SE and a 60" granite 6 inches will hang out on each side.   Hopefully the granite is wider then the SE.  now carefully hinge  the SE on the granite looking for the rotation points or hinge points on each end.  mark that spot.  Then cut 3 same thickness shim stocks, say .002" thick.  Either plastic or steel like 1/2" wide Precision Brand ona roll.

Then lift one end at a time and slide in a feeler under the rotation point.  then take the 3 rd feeler and slide around the SE looking of feeling for gaps. Mark them, if there are not any then carefully slide (one side at a time) the SE so each end and check the ends.   Depending on what you see you can get a game plan as to where the lowest points are on the SE.   I always scrape the lowest area first and after that 60" area is flat and about 20 PPI I do the other 12".  Then  after you get 20 PPI on everything and it hinges or rotates in the same places you do it again and get 40PPI.   Never slide the longer SE back and forth like your sawing wood as this could give you false readings.  when you blue up the first 60" make sure to keep the one end 2" from the end and never let it move over the edge.  rub it about 2 " each way.   Be sure to ring it a few time while scraping it.

The reason we ring it is when your using it when your done and didn't ring it and it gets bumped accidentally it could ring like a tuning fork and and twist.  It's a precautionary step.


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## Richard King 2 (Mar 10, 2018)

Rex you you have a way with words...thanks....and if your uncomfortable using a 1/4 inch, use a 3/8" industrial grade eye bolt, not a hardware store eyebolt.  Be sure to drill it in the nearest mass.  Be a detective as I can't look into a crystal ball and say her 1" in and 2",  up..
Rex how about you start a new thread showing where and how you did it, please.   Rex just bought one of my  HKA-36" castings he had John York milled it.  Rich

PS:  Rex took one of the Keith Rucker scraping classes I taught last spring i think it was..


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## Rex Walters (Mar 11, 2018)

Putting an eyebolt into the end of my 36” camelback won’t be nearly as interesting a thread as Will scraping in his 6’ monster, but I’ll be sure to take a couple pictures when I do. 

I’ve got to build some sort of wooden saddle or clamp out of scraps first to hold it while scraping, especially the dovetails. I just need something to hold it canted at 45deg while I scrape the dovetail. 

I’m thinking of basically just a couple of wooden vee blocks (milled out of a two by four) clamped to a bench. I’m pretty tall, but I still might need to stand on a platform while scraping with it that high up. If you’ve got any suggestions, I’m all ears.

Will, Richard’s comment #19 above looks to have answered your original question completely (yup, it’s doable). Now it’s on you to take a bunch of pictures and document your progress to entertain the rest of us! Really looking forward to seeing how it goes. 

You’re leading a purer life than me, by the way, if five foot lengths of precision granite are falling into your lap. (Laugh)


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## Richard King 2 (Mar 12, 2018)

There is a few ways to hold it.   I used to have a 32" Bridgeport table I camped it to and leaned the table up on scrap wood.   I also sometimes will drill & tap 2  - 1/2" /13 holes one on each end and use a long bolt fed trough a jam nut and set it in wood V blocks and either use 2 Johnhanson wood clamps or machine vises to hold the nut.   I have a picture someplace.   Some use wood V block and use a wood  1 x 4 clamp screwed in with a electric drill   and long wood screw .    Use your imagination and you'll get it  
Pic's L to R  -Using 2 screw wood clamp to tip grinder table to 45deg.  More of my cash of SE castings, 2 wood clamps holding nuts n end of SE,  Tom Utley's wood jig he built at K. Ruckers class 2 holding non ribbed SE, Rex testing his part at K. Rucker class 4


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## wcunning (Mar 12, 2018)

I like those methods Rich! Seeing that kind of setup is half the battle -- once you see one picture, you can modify it to suit your situation, but without ever seeing anything you have no starting point. To throw another one out there, Ken (@4gsr) posted pictures of using the Harbor Freight tilting weld table to hold a lathe cross slide at the right angle to scrape into the dovetails. I thought that looked like a particularly good design.

On a related note, I'm nearly done building the "Moravian Workbench" per, or at least inspired by, Will Meyers' design, and my intention is to make up a set of hold fasts so that I can use basically random scraps of lumber to hold parts for scraping, make corners to butt a compound or a slide or the like into, etc. As a fellow woodworker turned machinist, does that basic plan seem reasonable @Rex Walters ?

Thanks,
Will


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## 4GSR (Mar 12, 2018)

The only problem I have with it, you have to hold it down with one foot. If you don't, it starts dancing around on you.  Works real well for those inverted vee's and dovetails on the saddle of your lathe.

Ken


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## Rex Walters (Mar 12, 2018)

Richard King 2 said:


> Rex testing his part at K. Rucker class 4



Sadly, I wasn’t able to walk away with the squaremaster. Apparently the owner wanted to keep it!


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## Rex Walters (Mar 13, 2018)

wcunning said:


> On a related note, I'm nearly done building the "Moravian Workbench" per, or at least inspired by, Will Meyers' design, and my intention is to make up a set of hold fasts so that I can use basically random scraps of lumber to hold parts for scraping, make corners to butt a compound or a slide or the like into, etc.



I’d love to see your bench! (I actually own some property in Pittsboro, NC where Roy Underhill has his shop, but I’ve not been back there since before he opened it.)

In my VERY limited experience (a box square and a few small straightedges) a woodworkers bench is extraordinarily useful for scraping. Lots of workholding options and they’re heavy enough not to move around while scraping. Hold-downs are definitely useful for clamping a handscrew or whatever in place. I use both the traditional “whack it to clamp” style as well as the Veritas screw type hold-down. The latter is particularly useful as you can control the clamping force and don’t have to worry about table thickness to get good clamping. Don’t forget holes on the sides/legs for the holdfasts (especially with the Veritas holdfast where extra thickness isn’t a concern).

Fair warning, though. As I’m sure you know already, scraping is gloriously filthy work. My bench is now so filthy with embedded scraping swarf, bluing, and miscellaneous oil stains that I can’t let an instrument or fine piece of lumber anywhere near it. One of these days I need to make a hardboard cover for the thing to protect it from metalwork. Before that, I need to handplane away the filth (with a fore-fore-fore plane and disposable blade!).


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## Richard King 2 (Mar 13, 2018)

4gsr said:


> The only problem I have with it, you have to hold it down with one foot. If you don't, it starts dancing around on you.  Works real well for those inverted vee's and dovetails on the saddle of your lathe.
> 
> Ken



He had 2 on there, but took it off so i could take the picture, it worked pretty good.  EDgar who has taken 4 classes now. He was at the Texas class you parked on the grass ken..lol.  That picture was taking at the Peter Ross NC class and he has been at 2 Keith Rucker classes and  he assisted me on the 4th one.   what sucks now his prostrate cancer is back...


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## Rex Walters (Mar 15, 2018)

Richard King 2 said:


> Rex how about you start a new thread showing where and how you did it, please.



Not worth a whole thread, but here’s a photo of the result. I just found the balance point using a piece of pipe on the bench as Rich suggested, marked with a sharpie, and drilled and tapped for 1/4-20. Since the web is only about a quarter inch wide, I just milled a hole in the web so I could use a jam nut. The eye bolt was a bit of a loose fit, so the nut is definitely stronger.


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## Richard King 2 (Mar 16, 2018)

Be sure to weld the eyebolt.  I also would have prefered you would have drilled into the thicker angle just under the rib webbing end and not cut into the rib itself.    Have to keep an eye on it and see what happens doing it that way (first time, i have seen that).   Have you rung it while scraping it? 

Andy one of the Rockford students also bought (HKA-36) one and is scraping it in class this week.  He's ringing it and it first time changed .001 he said and 2nd time only .0005".  We suspect the 3rd will be the charm and not move that we will do today .  I'll add some photos in a couple of days.  

Just got 2 more orders for castings this week.  Picking up some HKA-18 from foundry next week and I'll be dropping off the HKA-72 pattern as I got an order for one going to Australia.


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## Rex Walters (Mar 16, 2018)

Are you joking about welding the eyebolt? THAT would cause it to move, surely!

I should probably have picked up a smaller eyebolt than quarter inch. Then I could have just drilled into the web. The hole I milled is more for appearance than anything (no way I’d have drilled exactly in the middle of the web without blowing out one side).

The nut is just to keep the bolt from spinning/rattling - not because I had any worry about threads in cast iron being strong enough. It was a very loose fit, however. I could have used loctite, but it came with a nut from the hardware store, so I used it.

I’ve not started serious scraping, I just took a few initial passes to remove the milling marks and break up the surface. I’ve not blued it up yet (I won’t have access to a large enough plate until the class).

I’ve got one more surface I plan to scrape (the 90 degree side). I’ll ring it a bit more after I take a couple passes along that side. I think removing metal unevenly will cause as much movement as anything (except maybe heat from spot welding!).


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## wcunning (Mar 16, 2018)

Hey Rich,

Any chance you could take a picture of where you had Andy put his eyebolt to hang for striking? 

Thanks,
Will


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## Bob Korves (Mar 16, 2018)

Rex Walters said:


> Are you joking about welding the eyebolt? THAT would cause it to move, surely!
> 
> I should probably have picked up a smaller eyebolt than quarter inch. Then I could have just drilled into the web. The hole I milled is more for appearance than anything (no way I’d have drilled exactly in the middle of the web without blowing out one side).
> 
> ...


Some blue Loctite and it will not come apart until you take it apart.  Room temperature welding...


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## wcunning (Mar 16, 2018)

@Rex Walters -- I'd like to start a separate discussion of scraping work holding and spend some time talking about the woodworker's workbench for the purpose. Would you be interested in contributing to some of that? I'll be actually putting the wedges in the stretchers and pins to keep the top from sliding next week to finish my Moravian, and then I want to start figuring out how I want to setup to scrape some of the more complicated bits for my machines, even if I won't get to the actual scraping right away. 

Also, side note, would a drop cloth with some holes to run the holdfast shanks through keep a sufficient quantity of the swarf off of the bench? Tarp maybe? Stefan Gotteswinter's scraping videos mention that he uses a vacuum every time instead of a brush to keep the scraping swarf from getting everywhere.

Thanks,
Will


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## Rex Walters (Mar 16, 2018)

wcunning said:


> Would you be interested in contributing to some of that?



Sure. My posting here is a bit sporadic as I get sucked into other things, and I doubt I’d have much of interest to add, but happy to help.

A woodworkers workbench is basically just a large special purpose clamp — it’s whole purpose in life is workholding. No special techniques I can think of, but holdfasts clamping handscrews to a bench make for nice quick workholding for scraping and similar jobs.

Vacuuming regularly will definitely help with some of the mess (I suspect I have more iron dust in my lungs and nasal cavities than is healthy) but the bluing, solvents (windex), and lubricants for stoning (WD40) are just as messy. A tarp or paper/plastic will definitely help to protect the bench if you care about appearance. I’m considering making some semi permanent removable covers out of hardboard (since I do more metalworking than fine woodworking these days).

I’ve noticed that the machinists who do the best work tend to keep their shops and workspaces VERY clean and organized (constantly taking the time to clean as they go). My shop is currently about knee deep in accumulated swarf and other filth from the past umpteen projects, with barely any flat surfaces remaining to set something down. That should tell you all you need to know about the quality of my work!


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## Rex Walters (Mar 16, 2018)

Bob Korves said:


> Some blue Loctite and it will not come apart until you take it apart.  Room temperature welding...



Yup. As I said, I had a nut in hand so I opted to use it rather than loctite. That eyebolt isn’t going anywhere. 

It doesn’t seem worth fretting much about a simple hanger — I just didn’t want it spinning freely. By drilling where I did (at the balance point) it hangs nice and vertical. If I’d drilled a bit lower as Rich suggested in his last message, I could have avoided cutting into the webbing or using a jam nut, but it wouldn’t hang vertically.

(Unrelated: A million years ago I studied statics and dynamics. I’ve forgotten 99.999% of what I learned about trusses, but I do remember enough that I’m not losing any sleep about that tiny little hole I made in the webbing having any measurable effect on stiffness.)


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## Bob Korves (Mar 16, 2018)

Rex Walters said:


> Yup. As I said, I had a nut in hand so I opted to use it rather than loctite. That eyebolt isn’t going anywhere.


I meant for you to use Loctite on the bolt to nut interface, so it cannot rattle loose...


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## Rex Walters (Mar 16, 2018)

Bob Korves said:


> I meant for you to use Loctite on the bolt to nut interface, so it cannot rattle loose...



Ah. I think my use of “jam” nut wasn’t clear. The hole in the straightedge is threaded - no point in a nut at all if I use loctite.


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## Rex Walters (Mar 16, 2018)

wcunning said:


> Hey Rich,
> 
> Any chance you could take a picture of where you had Andy put his eyebolt to hang for striking?
> 
> ...



Pretty sure it was in roughly the same place as my photo. It’s possible he milled less off the bottom so the balance point was closer to the “meat” of the straightedge, but I think the point is just to put it where the straightedge will hang vertically. 

This makes intuitive sense to me. 

Same reasoning as building a vertically oriented rather than horizontally oriented box for a cylinder square or (rectangular) box square — gravity effects on the shorter sides will have less effect than on the longer. 

In other words, while supporting a beam on Bessel points will minimize the average displacement,  shorter beam lengths will minimize the TOTAL displacement regardless of the support points (and the long vertical scraped side should remain quite flat).

Hanging from an eyebolt is a lot easier than building a vertical box/stand to store a camelback on end, but I suspect either would accomplish the desired result of minimizing gradual deviation from flatness due to gravity effects.

I’m not much of an engineer, so I have to think in overly simplified, extreme analogies. Imagine you made a six foot “camelback” out of two inch strips of card stock (cereal boxes). The scraped “reference edge” is a 2” x 72” strip on the bottom, connected by a 2” by 73.33” arch on top (creating a six inch tall “camelback”). Maybe you even imagine some card stock truss work or paper webbing between the arch and the reference edge.

If you found the balance point on the end of the arch, near to the reference edge, such that you could hang hang the “camelback” on end, the reference edge would remain pretty flat/straight, even if the whole thing sagged and distorted significantly. If instead you  rested it on the long reference edge, the whole works would sag and deform to match whatever it rested on. If you rested the reference edge on two cylinders about 22% of the way in from the ends (the Bessel points) you would average out the deflections, but the reference edge would be a long way from flat.

(I’m writing this after a healthy dose of good bourbon and after a long week, by the way. It’s possible it affects me differently than normal people.  Apologies in advance if this comes off as at all preachy. I just enjoyed thinking it through and thought I’d share.)


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## Richard King 2 (Mar 17, 2018)

NO I didn't say to weld the hardware store bolt to the casting!  I said to weld the eye-bolt as it is is a cheap hardware store bent bolt.  I also have been thinking about the way you did it.I said to drill and tap a hole. I did say to put it on a pipe to find the balance point and drill and TAP a hole.  Usually people drill the hole before they are machined.

You need to do that and don't do what you did as that little rib the weight on it will surely bend.

Here are some pictures of Andy scraping his HKA-36 straight-edge like yours.  He worked on it at the Rockford Scraping class we just finished yesterday at Bourn & Koch Machine Tool Company.


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## Richard King 2 (Mar 17, 2018)

wcunning said:


> @Rex Walters -- I'd like to start a separate discussion of scraping work holding and spend some time talking about the woodworker's workbench for the purpose. Would you be interested in contributing to some of that? I'll be actually putting the wedges in the stretchers and pins to keep the top from sliding next week to finish my Moravian, and then I want to start figuring out how I want to setup to scrape some of the more complicated bits for my machines, even if I won't get to the actual scraping right away.
> 
> Also, side note, would a drop cloth with some holes to run the holdfast shanks through keep a sufficient quantity of the swarf off of the bench? Tarp maybe? Stefan Gotteswinter's scraping videos mention that he uses a vacuum every time instead of a brush to keep the scraping swarf from getting everywhere.
> 
> ...



Did you see Sefan was a 2 class student of mine?  I also had him interpret for me on my last trip to Germany where he scraped and helped me.


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## wcunning (Mar 17, 2018)

Richard King 2 said:


> NO I didn't say to weld the hardware store bolt to the casting!  I said to weld the eye-bolt as it is is a cheap hardware store bent bolt.  I also have been thinking about the way you did it.I said to drill and tap a hole. I did say to put it on a pipe to find the balance point and drill and TAP a hole.  Usually people drill the hole before they are machined.
> 
> You need to do that and don't do what you did as that little rib the weight on it will surely bend.
> 
> Here are some pictures of Andy scraping his HKA-36 straight-edge like yours.  He worked on it at the Rockford Scraping class we just finished yesterday at Bourn & Koch Machine Tool Company.



I'm not seeing any pictures in that post? Did the upload not go through or something?


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## Rex Walters (Mar 17, 2018)

Richard King 2 said:


> I said to weld the eye-bolt as it is is a cheap hardware store bent bolt.



Ah! (Laugh) That makes a lot more sense — I thought you might have been making a strange joke. You just meant to weld the eye closed.

Leave it to me to screw up simple instructions, but I don’t think it would have been that much stronger if I hadn’t made the hole in the web. Even if I hadn’t blown through one side, there would have only been paper thin walls in the web portion.

I’m not too worried about the quarter inch bolt opening up or the cast iron rib bending, or more likely fracturing — the thing isn’t all *that* heavy — but I’ll let you inspect it in a couple weeks. If you think it’s better to drill and tap a hole into the meatier part on the other end and let the thing hang off kilter, I’ll do it and install a better eyebolt.

Seriously, though, I think the concerns may be a bit overblown for a 45 lb. casting. If it were a hundred pounds or two heavier, I’d worry a lot more.


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## Rex Walters (Mar 17, 2018)

Rex Walters said:


> and install a better eyebolt.



Rich’s disdain for my hardware store eyebolt made me self conscious — how can I hold my head up at scraping class? (Laugh) 

So I just threw a grade 8 1/4-20 stud and lifting eye ring into my latest order from McMaster. To hide the shame of having made a hole in the webbing, I’ll fill the hole with weldment, grind it back flat, and paint it over. You’ll never know it was there!

(I’m KIDDING about the welding — the hole is permanent, I’m afraid. I may bring some red electrical tape to class for camouflage, though!)


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## Richard King 2 (Mar 17, 2018)

Give it a try and see what happens.  

But to whom it may concern in the future drill the hang up hole in the casting about 1/2" lower then the ribs.  Please do out hang the straight-edge from the ribs.

Andy did not drill a hole as he got the straight-edge from Texas where it was planned on Tuesday night. He lived in WI and drove back and forth to class.   He was in a hurry to scrape it before the end of class as he doesn't own a long granite plate.


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## Rex Walters (Mar 17, 2018)

Richard King 2 said:


> But to whom it may concern in the future drill the hang up hole in the casting about 1/2" lower then the ribs.  Please do not hang the straight-edge from the ribs.



Thanks, Richard. I’m looking forward to speaking again in person. Too much written on the web gets misinterpreted — I certainly mean no disrespect — but are you now suggesting to ignore your advice about finding the balance point? Drilling the hole a half inch below the ribs is a solid inch away from the balance point in my case, and will cause it to hang well off of vertical.

No problem either way, I’m just trying to understand.


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## Richard King 2 (Mar 17, 2018)

Yes....I have never seen or recommended drilling into the ribs.


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## Richard King 2 (Mar 19, 2018)

Rex,  Also I see you have the outside support hole wrapped with rope.   That is not a handle if that's what your thinking.   You hold the straight-edge when using it at the 30% in from each side ribs. I have wrapped those ribs with red rags and tape when i am using them when scraping Jig bores.  I doubt you will see any deformation when handling it bare handed.

Don't get me wrong,  I appreciate your enthusiasm on buying my Straight-edge brand, but please email or call me when your working with it.  I am sure i can save you some time .


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## Rex Walters (Mar 19, 2018)

What about the paint color? Red okay, or did I screw that up too? I’m half expecting a lecture on unevenly applied, cheap hardware paint affecting the accuracy. (Laugh)

I also already made a couple wooden feet for the back so I can rest it upside down (roughly on the Bessel points). I can’t go back in time, but I’ll be sure to talk to you before I touch anything else on the straightedge again (for the rest of time .


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## Richard King 2 (Mar 19, 2018)

Rex Walters said:


> What about the paint color? Red okay, or did I screw that up too? I’m half expecting a lecture on unevenly applied, cheap hardware paint affecting the accuracy. (Laugh)
> 
> I also already made a couple wooden feet for the back so I can rest it upside down (roughly on the Bessel points). I can’t go back in time, but I’ll be sure to talk to you before I touch anything else on the straightedge again (for the rest of time .


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## Richard King 2 (Mar 19, 2018)

I generally set it upside down in some of those 2 screw wood clamps.   Red is fine...Last week one of the guys told me to use a glass paint that is brushed on.   I usually tell folks to buy tractor engine paint.


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## KBeitz (Aug 1, 2018)

Any precision flat tooling can be checked with a laser...


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