[How do I?] Make a box square and set of small dovetail gages (straightedges)

I made a straight edge and finished it with a 3/4" wide pull scraper.
This produced a very flat surface without the low spots generated using normal procedures.
I found that the blue had to be very very thin when spreading it on the straight edge or it would give
bad readings and the straight edge wouldn't hold blue because it had no low spots.
Blue had to be applied and carefully spread with each check.
While this allowed some very good finish readings it was slow and not so good for most of the process.
Another member pointed out the flaws in having such a flat tool surface.
Because the straight edge bowed over time it was re-scraped with a rougher surface and is better to use.
The rough surface holds blue and is much faster to use.
Jim
 
Rex or others would you mind pointing me to How to build a hand scraper...clamping styles etc. By the looks of the dapra's Might be a good idea for me to build one that would take all of those they make.
 
Whoops. Sorry, I've been traveling and forgot to reply to this.

It wouldn't be too hard to make a handscraper of the Dapra design. If you value your time at nothing, it's definitely possible to make one cheaper than buying one for a hundred bucks from Dapra, especially if you've got some mild steel bar stock scrap lying around. I opted to just buy one, though.

Keith Rucker had some dimensioned drawings he made up. Please contact him directly as I don't want to redistribute his drawing without permission.

You could also braze up some carbide blades rather than buying them from Dapra, but I doubt you'd save much money. If I only bought one, I'd opt for the long 20mm wide one with a 60 degree radius. IIRC the part number is 20-150.

Regards,
--
Rex
 
Rex Walters said:
Whoops. Sorry, I've been traveling and forgot to reply to this.

It wouldn't be too hard to make a handscraper of the Dapra design. If you value your time at nothing, it's definitely possible to make one cheaper than buying one for a hundred bucks from Dapra, especially if you've got some mild steel bar stock scrap lying around. I opted to just buy one, though.

Keith Rucker had some dimensioned drawings he made up. Please contact him directly as I don't want to redistribute his drawing without permission.

You could also braze up some carbide blades rather than buying them from Dapra, but I doubt you'd save much money. If I only bought one, I'd opt for the long 20mm wide one with a 60 degree radius. IIRC the part number is 20-150.

Regards,
--
Rex
Click to expand...

I REALLY like to buy tools. When you use words like I do "value your time at nothing". It makes me twitch. lol Even if I do that occasionally.
...I still need a snug for that TDI you pointed me to.

Paul
 
Heh. Well, there are definitely reasons other than cost to build rather than buy: modifying dimensions or design to suit your specific frame or other needs, for practice machining to a drawing, or simply for the fun of it.

The design is only six parts including the handle, and three of the five parts are clamps that don't need any particular care in manufacturing. The main bar is just a 1" x 12" flat mild steel bar 0.1875" thick. No particular challenge to make one if you have a mill and some taps. If you have a wood lathe or have a hand rest on your metal lathe, it's easy enough to make a handle, too.

Regarding the snug: every surface gage I've seen comes with a "universal" snug with at least a couple different hole sizes. Usually the smaller hole that holds the pointer arm can also hold the smaller diameter post that came with your dial test indicator (DTI). Annoyingly, there is no standard though and you really need something rigid and secure -- if the hole size is too far off then you'll need to scrounge up or build something better.

Regards,
--
Rex
 
A hand scraper is dead easy to make. No drawings are really needed. It can be done with a couple feet of 1 x 1/8" hot rolled bar stock, a file handle, and a carbide blank. And a few basic skills and tools. Or you can reinvent the wheel, create a new design, and get as fancy as you desire. Maybe you will be selling thousands a year before your design is copied offshore for 1/4 the price...
 
Bob Korves said:
It can be done with a couple feet of 1 x 1/8" hot rolled bar stock
Click to expand...

True. You can even skip the carbide and just repurpose an old file for that matter (though you'll spend an awful lot of time sharpening and would probably appreciate more flex).

I've tried both Anderson style tubular scrapers and the Dapra design, and I'm with Richard King in preferring the latter. It's also a big win being able to use multiple blade types and widths (and share them with your Biax power scraper if you have one or plan to obtain one).

In a pinch, I'd be willing to use a chip of carbide brazed onto the end of a steel rod. If I was going to spend more than a couple minutes making something, though, I'd definitely copy the Dapra design.
 
Rex Walters said:
True. You can even skip the carbide and just repurpose an old file for that matter (though you'll spend an awful lot of time sharpening and would probably appreciate more flex).

I've tried both Anderson style tubular scrapers and the Dapra design, and I'm with Richard King in preferring the latter. It's also a big win being able to use multiple blade types and widths (and share them with your Biax power scraper if you have one or plan to obtain one).

In a pinch, I'd be willing to use a chip of carbide brazed onto the end of a steel rod. If I was going to spend more than a couple minutes making something, though, I'd definitely copy the Dapra design.
Click to expand...

Yeah Bob and I messed with my re-purposed file last time I was there. It certainly cut better freshly sharpened. Of course the operator probably has a lot to do with that. I haven't scraped much.

A clamp style carbide holder probably would do me a lot of good. Plus I am certainly going to buy a Biax power scraper. I've got it on auto watch on ebay. If I catch one at a decent deal it's going to be mine. :)

Paul
 
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