Help!!! Poor man's Straight Edge for a scraping standard???

jgedde

jgedde

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As I posted a month or two ago, I scored a Boyar Schultz 6x18 surface grinder with 2 axis hydraulic feed for $500. I've since restored the machine but recently encountered a problem. I've had trouble getting the chuck truly flat. After a bunch of debugging, I found the problem. The Y-axis bed ways rock on the base ways. It's a bit weird since there isn't much wear on the ways. In any case, there may well be some way scraping in my future for which I'll need a straight edge. Pricing new and used straight edges suitable for use in scraping ways was enlightening. I'm looking at $250 - $750 for a suitable unit that I'll only use a few times in my lifetime.

We don't have any at work so I'm out of luck there. Any ideas for a poor man's straight edge for a one time job?

Anybody in my local area (Long Island, NY) have one they'd mind renting or loaning?

Thanks,
John
 
Hi John,

Not sure what is the best avenue for a cheap straight edge. Maybe Richard King or others will offer up some advise.

David
 
When I needed to scrape in a dovetail, I made a 55 degree prism out of a piece of continuously cast iron bar. It's not cheap, but probably cheaper than a cast piece. How long are the ways?
 
Not to discourage your pursuit of a suitable straight edge or anything, but have you considered having a professional machinery rebuilder give you a quote to grind/scrape the ways? I have a similar sized machine currently being reconditioned, albeit slowly in my driveway, and I've come upon the same quandary. I've heard of folks having lathe beds ground for less money than the cost of a large and accurate straight edge.
 
Just a thought - years ago I had a straight edge ground at a shop that sharpened knifes for large wood planers used in the lumber mills, I believe the limit was either 47 or 49 inches in length. I used a piece of bandsaw blade that originally was 12 inches wide but got destroyed when it hit a spike in a log. This makes me think perhaps you could find a suitable straight edge using a new planer knife? or if the timber industry is prevalent in your area I'm sure there is someone out there that can grind one fairly cheap.

Good Luck!
 
I found a suitable straight edge. Oddly enough it is a 24 inch length of 6061 fly cut in our CNC mill here at work for use as a soft jaw for two vise setup. The fly cuts have a mirror finish that I can see my reflection in. (They use a 8 cutter shell mill with Sandvik inserts)

I checked it on our big surface plate and this sucker is flat and parallel (on two opposing faces) to within 0.0001! How that came to pass I can't even fathom. What's strange is those two fly cut faces aren't the clamping faces

In any case, my current theory is that I'll not need much if any scraping. The amount of rock in the saddle is about 0.005. I can slip a 0.008 feeler gauge between the bed and the saddle! If that was due to wear, clearly I'd see a wear ridge on the bed or the saddle ways. Thing is I don't see anything like that.

I'm thinking the saddle or the base is tweaked... Most likely the latter. There's three fixed mounting pads on the dust collector/base, and one adjustable pad (in heigth). If this isn't set right, when the bolts are tighted down it might twist the base out of whack. So, hopefully by adjustment and if necessary, shimming, I can straighten this out. If it's the saddle (which I doubt), I'm likely up the creek without a full regrind.

John
 
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Did you check with a DTI, or by touching off with blue? If you only used a DTI, I would recommend a test with some bearing blue on a surface plate. You may need to scrape a reference surface on that aluminum block, but what you had is probably a good start. It's going to take a light touch in aluminum. I would also be careful when touching off on your ways, that aluminum is going to be much softer than the ways, and if you are not gently, you will turn up a bur that is going to cause you grief.
 
DMS said:
Did you check with a DTI, or by touching off with blue? If you only used a DTI, I would recommend a test with some bearing blue on a surface plate. You may need to scrape a reference surface on that aluminum block, but what you had is probably a good start. It's going to take a light touch in aluminum. I would also be careful when touching off on your ways, that aluminum is going to be much softer than the ways, and if you are not gently, you will turn up a bur that is going to cause you grief.
Click to expand...

I don't have any blue (yet), so I used the DTI. Right now, my plan is to use this as a simple straight edge with a feeler gauge to map out the problem and see how it relates to the base mounting pads.

Since, hopefully, I won't need to do any scraping to fix this problem, I can get by with the aluminum bar (despite its softness) and a machinist's level. I figure if I can achieve level on each way horizontally, vertically and diagonally by use of the one pad adjustment and shims, I can be reasonably sure that each of the 4 way surfaces are all coplanar (since my current theory is that coplanarity issues are causing my woes rather than individual ways that aren't flat).

If scraping is necessary, I'll likely not consider the aluminum. That, as you say, may be a recipe for trouble.

So, I'm still soliciting suggestions for a poor man's way scraping standard since I haven't ruled out the need for scraping. Plus, if I can pull it off for say under $100, I might just jump at it as a valuable shop accessory.


Thanks,
John
 
Froneck said:
I'd avoid scraping the grinder. It don't seem to be worn but slightly twisted probably from sitting in some corner. If it twisted out you can twist it back. I've straightened many lathe beds.
Frank
Click to expand...

That's my current theory as well... Still a known flat standard for blueing will be useful in untwisting it (I think).

Can you suggest as a viable method of measuring the twist so I can correct it? Maybe I'm overlooking a simpler method .


Thanks,
John
 
Here's what I found... The saddle is near perfect, the base has issues. Refer to the picture...

Under, the base, in each corner are mounting bolts holding the grinder's base to the dust collector/stand. The mounting pad on the front right of the stand is adjustable in height.

As you can see, the base ways are in fairly good shape. The left hand way, and the two center ways are all coplanar. The right hand way, however is 0.005 high in the front and about 2-3 thou high at the back. I'm guessing if the way went all the back to the rear corner it would reach zero with respect to the other three. All in all, this made me think the adjustable pad was simply too high and required adjustment.

So, I lowered it A LOT and retightened the mounting bolt. It made only about 0.001 worth of difference and the front right is still high by about 3.5-4 thou. What gives? Does cast iron take a set? Obviously the base is twisted a bit. What will it take to straighten it out? Is this a situation like tooth braces where steady pressure over time will slowly move it back?

Or, should I just adjust the mounting pad to a zero stress condition and grind/scrape the right hand way coplanar with the other three? Ugh!

IMG_1428.JPG

I guess the good news is that since the saddle is off, I can paint the areas I couldn't get it with the saddle in place!

John

IMG_1428.JPG
 
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