Straight Edge For Dovetail Ways

john.oliver35

john.oliver35

H-M Supporter - Gold Member
H-M Supporter Gold Member
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Apr 26, 2014
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Hello All,

I am looking for an angled or triangle straight edge to use to print the inside dovetail ways on my Rockwell 21-100 mill. I had thought I could find a granite 45/45/90 edge or a short, thick straight edge with a 45 degree angle. I am either looking in the wrong place or just plain not finding something like this.

I have been scraping the mating flats using a surface plate to print the surfaces. 12" long would be long enough. Where can I buy something to start with? I can scrap an angle flat using the surface plate if I need to make something myseslf. If I were to do that would one start with cast iron, or would a 4140 steel work (mill it close first, then scrape it in)?

Any suggestions appreciated!
John
 
Your straightedge should never be used as master for the angle on your ways. You just use it like a normal plate to reach into the corner.

ThisOldTony on youtubr has a video on making a straightedge. I recommend you watch it, along with all his surface grinder rebuild videos.

Sent from my XT1053 using Tapatalk
 
Andre - Thank You! I wasn't clear - I am just looking for something that is flat to reach into the corner, not to use as a master for the angle.
 
I've made a few over the years and obtained a couple triangular one's too that I've used for scraping and fitting of dovetail slides. All of the one's I've dealt with were made to make impressions for both the angular and flat at the same time. You only worked with surface at a time. I know this defeats the proper way they should be built and used, but it worked. IMHO, I see no reason using a dovetail straight edge that is made to a specific angle for scraping in dovetails. Person just needs to pay attention to the impressions made to make sure you don't let your surfaces go co-planer and out of parallel on you while scraping and fitting.
 
as for the material:
take a piece of 4140 ( or any material but cast iron) and try to scrape it
you will turn to cast after a couple of minutes experience
 
john.oliver35 said:
Hello All,

I am looking for an angled or triangle straight edge to use to print the inside dovetail ways on my Rockwell 21-100 mill. I had thought I could find a granite 45/45/90 edge or a short, thick straight edge with a 45 degree angle. I am either looking in the wrong place or just plain not finding something like this.

I have been scraping the mating flats using a surface plate to print the surfaces. 12" long would be long enough. Where can I buy something to start with? I can scrap an angle flat using the surface plate if I need to make something myseslf. If I were to do that would one start with cast iron, or would a 4140 steel work (mill it close first, then scrape it in)?

Any suggestions appreciated!
John
Click to expand...
ebay search for Kingscraping Richard has 12 in beveled camelback casting
 
there is also a Canadian outfit that is offering rough straightedge castings on ebay relatively cheap
http://www.ebay.com/itm/NOS-BUSCH-P...UGH-CASTING-/390774713741?hash=item5afbfced8d

but as far as an angled dovetail reference, the reference angle doesn't have to match the dovetail angle of the intended scraping victim. But the reference does need to be able to reach the deepest part of the dovetail without interference.
for example a 30* reference could be utilized to mark/scrape a 45* dovetail,
but a 45* reference would need to be relatively small in comparison to the 30* dovetail to be able to get to the root of the dovetail.
the same is true of a 50* reference being used to scrape a 60* dovetail

and ,of course, a 45* reference could be used for a 45* dovetail

a piece of cast iron 1 inch + thickness, that had a 45* milled on one side and scraped to a flat reference could also be produced, in fact i'm doing just that same thing on a blank that was made on a metal shaper. i didn't make the blank, but a fellow member, John York, sold be the blank eatrlier this year.
it can be done... here's a link to my project, a work in progress.....
http://www.hobby-machinist.com/threads/scraping-in-a-precision-straight-edge.34485/
 
Last edited:
One of our members (sidecar) had several scraping tools for sale.
You might ask what he has left.

Daryl
MN
 
Thank you all - lots of great information that seems to be hard to find. I am cleaning and rough scraping some clear high spots on the mill, then putting it back together. Then I can find some suitable iron or casting to mill @45 and make a straightedge. There is no end to the projects! I do love trying to develop skills to do some quasi-precision work when my day job is oriented towards 'good enough'!
 
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