How to pick the right straight edge length

*D'B=6bk · Feb 21, 2021

What is the minimum practical size for a straight edge to scrape in a Bridgeport Series 1 9x42? I am looking at dgfoster's 18" and 26" featherweight castings. Machine Tool Reconditioning mentions methods for using shorter SEs on longer surfaces but doesn't provide any guidance on the limits of these techniques.

To be clear, I'm sure a SE as long as the longest surface is ideal, but suppose a guy is doing this purely for enjoyment and would rather spend his time and energy than his money on it, how short is too short for the purpose?

thermite · Feb 22, 2021

*D'B=6bk said:
suppose a guy is doing this purely for enjoyment and would rather spend his time and energy than his money on it, how short is too short for the purpose?

How low is down? How high is up?

All you REALLY need is the Series 1 machine itself. Determination/patience/perseverance.... brains. Plus natural stone you can find on the ground.

It is EASIER if you cheat, though!

I'd FINISH with one my Fosters. As the "authority". The largest and heaviest of that whole tribe is easily 1100 lbs lower mass than the medium-sized Herman Grade A SP!

Which has never seen Ink. And may never. But that's a World War One Daimler Aero-engine build-team trick.

I'd start with metrology and accessories easily held in one hand.

Continue with but a heavy steel rule.

Switch to a slender Eastern European sourced 50 cm plain dovetail. Just tried to get a weight. Too light to register the scales I have handy. Prolly only a couple of lbs, Avoir?

One could do the whole job with that. Slavic craftsman did.

Anyway... the goal is to get the BIG variances progressively knocked-down to smaller and smaller variances.

Over the course of the project, I would have lifted and manipulated, toted, smeared, rubbed, stoned, and cleaned .... easily a ton or three less cumulative mass.

Lazy, Iyam. Also old and creaky!

The only "belly push muscles" here b'long to my wife's collection of the souvenirs of fine meals ... and other enjoyments.. of times gone by.

"Run what you got!"

Then savour the memories!

lucky7 · Feb 22, 2021

Three straight edges for me, but could do with two. I use a 48” King HKA for the table. I’m guessing a pro would get the table ground, but I’m not a pro and there’s no good grinder locally.

For the other bits, a Denis Foster 36” for the flats, and a 24” HKA for the dovetails. Now that Denis makes a 26” dovetail straight edge I think a guy could use just that for the knee. A guy could also get one of Stephen Thomas’s 30” straight edges. I have one and use for some projects.

Using a shorter straight edge than what you’re spotting is a pain. Wouldn’t recommend.

You do have a big enough surface plate, good tenths indicator, granite right angle, lifting gear, etc...?

Have fun!

L7

lucky7 · Feb 22, 2021

Still thinking about the OP’s question. Now may be the best time to purchase straight edges. Seems to be so many more types available, both as rough castings and second hand, than when I started scraping five years ago. More expensive too! If a guy can, I think he should take advantage of what’s available now as at least one supplier is making retirement noises. Get several different length SE’s for future projects...

L7

Richard King · Feb 22, 2021

I see your in TN and there is a GREAT machinery rebuilder and machine shop in Tullahoma who could grind the table for the price of a HKA-48 or other SE that's machined and scraped. Schmiede Corporation | Way Grinding You could also ask them what they would charge to grind all the ways for that matter. I just did a class in Fayetteville - SJS Machine and they fly cut a Bridgeport table to less then .002". As lucky 7 said you can lap scrape long ways with a shorter SE, but it takes 2 times longer and less accurate then using a longer one. I have been scraping for 50+ years and would not do it. A real PAIN. I just spoke to Stanley the owner at SJS and he said he would host another class there, so if your not in a hurry, come next time. I used to rebuild dozens of Bridgeport's and I always got the table ground. Top, bottom, sides and dovetails. I have scraped them heck 5o years ago when I was an apprentice I suppose, It took 3 or 4 days when I was handscraping. Check with Schmied first. I am here to help you if you need me. Rich

lucky7 · Feb 22, 2021

Richard, curious why you as a pro would grind the sides (I think you are referring to front and back face?) of a B-port table?

I scrape the front face 90deg to top and parallel to t slots so I can put the table front face down on a surface plate and use dowel pins alternating with SE for the back dovetail. Once back dovetail is done I do the usual with a mike and pins across both dovetails. All this, I think, is not needed if you grind the table. Correct?

L7

thermite · Feb 22, 2021

lucky7 said:
Richard, curious why you as a pro would grind the sides (I think you are referring to front and back face?) of a B-port table?

I scrape the front face 90deg to top and parallel to t slots so I can put the table front face down on a surface plate and use dowel pins alternating with SE for the back dovetail. Once back dovetail is done I do the usual with a mike and pins across both dovetails. All this, I think, is not needed if you grind the table. Correct?

L7

? I think you already know that whilst not ALWAYS an issue with mills, the "long", but relatively thin table BP's are among the most notorious for getting so much peen and sag and parking space at one of both extreme ends for vises, rotabs, DH, and general odds and sods into them by the time they NEED significant re-work ...that grinding needs done TWICE as they move from the effects of the off-side's grinding?

Even so, it is probably still a savings in downtime vs 100% "by hand".

One could ring Schmeide on the yellyphone and simply ASK?

Richard King · Feb 22, 2021

For looks plus it lines up with the dovetails. In the Testing Machine Tools / slesinger book it says the Tee-slots need to be parallel too. I never checked it though, and never had a customer complain. More for looks like new. http://totallyscrewedmachineshop.com...hlesinger).pdf

thermite · Feb 22, 2021

Richard King said:
More for looks like new. http://totallyscrewedmachineshop.com...hlesinger).pdf

Unless.. you have simply garbled it.. that URI "appears to be"....over five years out of date, Rich:

8 January 2016 website changelog:

Machine Reconditioning and testing (thanks to Ken)

This section is removed at one of the document owners request, so to be safe the rest also,

Can't disagree with his logic. More important things in life than arguments.

M.B. Naegle · Feb 22, 2021

IMO, you kinda answered your own question. Yes, as long as the longest surface. Shorter are better for the shorter surfaces of course, but it seems like the 18-24" and 48" pair of SE's tend to cover it for most guys.

That's what's ideal. Working with shorter SE's you can make it work the same as they do on big big machines with long cast ways, but you're adding time and potential for trouble to the mix. On those bigger machines, the long way castings have the ability to adjust to a certain degree and their size often means that a little error doesn't matter. .005" over 30 feet is better than .005" over 24". Taking the longer surfaces like the table and column for example, you could make it work printing them multiple times with a 12 or 18" straight edge, but you will spend much more time linking those prints together with an indicator and watching how the ends hinge and print.

IMO it's worth it to get the ideal size of SE, then sell it when you're done with it. Maybe you could even borrow or rent someone's, but I think you'd have better luck borrowing a friends seasoned cast iron dutch-ovens.

Richard King · Feb 22, 2021

I just called my OLD friend Rick at A D Machine Rebuilding in Roberts WI. He said he grinds the top and sides of Bridgeport tables for approx $300.00 and he plainer-mills the bottom and dovetails for another $250.00 He said that's an estimate, but close. We had a nice chat with him as he's the fellow who bought my Cleveland planer and Thomson Surface grinder. He said he is swamped. The 8' camel back on his website used to be mine...A & D Machine Tool Rebuilding, Inc. | Machine Tool Rebuilders, Way Machining and Hand Scraping, Turcite and Rulon Application

thermite · Feb 22, 2021

M.B. Naegle said:
I think you'd have better luck borrowing a friends seasoned cast iron dutch-ovens.

GAWD! The day I came home to find my lovely but "unaware" wife had chore-balled my best Griswolds then run 'em through the bleedin DISHWASHER!

She awakes next morning to the lovely smell of bacon.. comes into the kitchen hungry, sees me throw the last of two pounds of singed bacon into the trash.

"What are you DOING!"

"Seasoning a fine black Iron skillet."

"NOW I can cook with it!"

Never was one to Wok a hot dog on a cold day, let alone eat friggin' teflon with home fries, sausage, eggs over easy, nor Crepes Suzette.

Richard King · Feb 22, 2021

Again I have photo's and can reference friends in the business unlike some people who like to write nonsense and copy cats info real people write about. Ignore button is handy. I also have a Forum on Facebook called King-Way Scraping Consultants, I have had several PM members join lately too. On the forum, no nonsense is allowed. Thanks PM for letting me write here.

*D'B=6bk · Feb 22, 2021

Thank you for the great information. I'll contact Schmiede. I'd love to attend a Richard King scraping class. How does one find out the locations, costs, etc and get registered?

Richard King · Feb 22, 2021

I advertise them on Ebay, soon on my new Website and I usually post it here, my forum on facebook, or email me . [email protected]

lucky7 · Feb 22, 2021

thermite said:
? I think you already know that whilst not ALWAYS an issue with mills, the "long", but relatively thin table BP's are among the most notorious for getting so much peen and sag and parking space at one of both extreme ends for vises, rotabs, DH, and general odds and sods into them by the time they NEED significant re-work ...that grinding needs done TWICE as they move from the effects of the off-side's grinding?

Even so, it is probably still a savings in downtime vs 100% "by hand".

One could ring Schmeide on the yellyphone and simply ASK?

Thermite, yup, well aware, and tables also move with scraping. I measure how convex the table top is, then blind scrape top without wasting time printing. Check the hinge to make sure I haven’t screwed up the math, then flip and rough scrape bottom flats. When they are at about 5ppi, flip again. This time finish top taking care that top is parallel with bottom. I only do top to about 5-10 ppi as it isn’t a bearing surface. Then finish bottom flats to 20 ppi. Pretty easy really and while I’m sure it’s not profitable for a pro, it doesn’t take that long for a guy who scrapes just for fun and doesn’t have a grinder shop next door. And I won’t do a B-port table that needs more than 5-6 thou of droop corrected. Actually, just did a small horizontal mill that was 7thou convex but only a 31” long table...

If I was doing a #3 K&T or similar size machine, my answer may be different ;-)

L7

Richard King · Feb 22, 2021

Lucky, Are you now scraping for money? Or are these scraping jobs on your own machines? I would think your full time job would pay a whole lot more then pushing a scraper....lol

thermite · Feb 22, 2021

lucky7 said:
Thermite, yup, well aware, and tables also move with scraping. I measure how convex the table top is, then blind scrape top without wasting time printing. Check the hinge to make sure I haven’t screwed up the math, then flip and rough scrape bottom flats. When they are at about 5ppi, flip again. This time finish top taking care that top is parallel with bottom. I only do top to about 5-10 ppi as it isn’t a bearing surface. Then finish bottom flats to 20 ppi. Pretty easy really and while I’m sure it’s not profitable for a pro, it doesn’t take that long for a guy who scrapes just for fun and doesn’t have a grinder shop next door. And I won’t do a B-port table that needs more than 5-6 thou of droop corrected. Actually, just did a small horizontal mill that was 7thou convex but only a 31” long table...

If I was doing a #3 K&T or similar size machine, my answer may be different ;-)

L7

You may have the "handle, but I am the guy as "got Lucky".

The USMT Quartet - 1960's vintage Adam Booth figured- his (late) Dad I wrote the check to when I flew to Pensacola to haul it home - has a very similar work envelope (for its vertical head) as a BirdPort. but... it shares its 48" x 10 1/4" table with the 5 HP 40-taper Horizontal.

Seems it has LESS longitudinal traverse that the length indicates vs a BP?

Well. the saddle adapter bears over two feet long. And the table is half-again as DEEP, vertically. FAR more massive ram.. 5205 Avoir all-up? Three motors plus juice?

And so on.

Long and 'straight" of it is that despite its age, I can only measure about 3 thou deviation high center to low ends of that table with a known-good B&S 48" SE.

So the table ain't getting scraped atall!

So far, neither is anything ELSE.

I did say "lucky"?

Downside is the design is a really bad idea vs a Rambaudi or the like. Switchover means releasing 8 bolts, one shot-pin for tram, then hand-cranking the turret 180 degrees. And securing those 8 bolts.

PITA, but BFD.

I'm seldom in a rush!

How to pick the right straight edge length

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