Q: Technique or tool for spreading blue on a dovetail
Close
Login to Your Account
Results 1 to 20 of 20
  1. #1
    Join Date
    Oct 2010
    Country
    UNITED STATES
    State/Province
    Oregon
    Posts
    5,818
    Post Thanks / Like
    Likes (Given)
    5792
    Likes (Received)
    2249

    Default Q: Technique or tool for spreading blue on a dovetail

    I've been working over the Y axis of an unmentionable, got the load-bearing bed ways and saddle ways planar, and used a dovetail straightedge to clean up the non-gib dovetail of the saddle. I now want to blue up that saddle dovetail to transfer to the mating bed dovetail in order to check/correct the mating dovetail angle, and I haven't had to do that before.

    How do I get a reasonably even coat of blue in that space? Obviously the roller/brayer will not fit. I've been thinking about a small cloth pad wrapped around the end of a tongue depressor ("craft stick"), but surely there's a better way...

  2. #2
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    14,149
    Post Thanks / Like
    Likes (Given)
    3095
    Likes (Received)
    9383

    Default

    A section of (say) 1/4" rubber sheet cut to the correct angle, and used like a squeegee? You could even comp the angle for the deflection under use.

  3. #3
    Join Date
    Aug 2017
    Country
    UNITED STATES
    State/Province
    California
    Posts
    359
    Post Thanks / Like
    Likes (Given)
    99
    Likes (Received)
    176

    Default

    I use a small paint brush.

  4. #4
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    19,568
    Post Thanks / Like
    Likes (Given)
    2486
    Likes (Received)
    3757

    Default

    Your pad on a tongue depressor (or similar) is likely the best plan. Make sure it can get to the back of the dovetail and coats well there.

    I've never used a roller but a couple times, and didn't like it even for flat open surfaces. So I use a pad all the time. Should work fine.

    Some will cringe and have many reasons why it's bad, but I use the blue paper shop towels, rolled up, doubled over, with the loose ends stuffed into a piece of tubing. For dovetails, same stuff, but wrapped on a flat piece of "something". Tongue depressors are thin and should be fine for reaching into the dovetail. You might need something thinner to reach to the back, though.

    With the "pad" approach, it takes a bit more blue because some goes into the pad. I think the coating is better than with the roller, and the pads I use tend to pick up and remove any bits that get stuck in the blue.

    Those shop towels have the fibers bonded so they do not drop loose fibers unless really shredded.

  5. #5
    Join Date
    Sep 2006
    Location
    Stillwater, Oklahoma
    Posts
    1,896
    Post Thanks / Like
    Likes (Given)
    150
    Likes (Received)
    1126

    Default

    applicators.jpg

    This guy uses pad applicators and makes small ones for dovetails.

    21-pict0085h.jpg
    Last edited by TGTool; 09-25-2021 at 01:57 PM. Reason: Added pic

  6. #6
    Join Date
    Jun 2012
    Country
    UNITED STATES
    State/Province
    Michigan
    Posts
    14,247
    Post Thanks / Like
    Likes (Given)
    4854
    Likes (Received)
    5137

  7. #7
    Join Date
    Sep 2008
    Location
    Canada
    Posts
    1,720
    Post Thanks / Like
    Likes (Given)
    673
    Likes (Received)
    686

    Default

    I make a wooden wedge and glue thin layer of rubber on it.

    Seems rare tho. Most of the time I’m spotting a dovetail from a blued straight edge.

    L7

  8. #8
    Join Date
    Sep 2006
    Location
    Stillwater, Oklahoma
    Posts
    1,896
    Post Thanks / Like
    Likes (Given)
    150
    Likes (Received)
    1126

    Default

    Quote Originally Posted by lucky7 View Post
    I make a wooden wedge and glue thin layer of rubber on it.

    Seems rare tho. Most of the time I’m spotting a dovetail from a blued straight edge.

    L7
    The OP's situation is one case where the question is completely pertinent. He will have scraped the saddle dovetail on the headstock side so that it is flat (tested with the dovetail straightedge) and transverse to the ways with that slight allowance for concave turning. The precise angle of the saddle dovetail may have changed slightly but it's not relevant.

    Now the crosslide will be scraped to match the saddle and its dovetail now becomes the master - at least for the correct angle. He may be doing an occasional crosscheck with the straightedge depending on the relative lengths of the saddle and crosslide surfaces. It would be possible to get the inside vertical dovetail of the crosslide casting slightly convex if he's not careful.

  9. Likes JST liked this post
  10. #9
    Join Date
    Jul 2005
    Location
    Cottage Grove, MN 55016
    Posts
    8,577
    Post Thanks / Like
    Likes (Given)
    4499
    Likes (Received)
    5048

    Default

    Back in the old rebuilding all the time I looked in the closet and pulled out an old work boot and cut up some leather. I've used leather belts. I've also used the corner of a red rag. If you cut off 3/4 of the bristles on a paint brush that works too, but occasionally a bristle comes off. A secret to dovetail scraping is to cut the bottom vertex. That lets you get down there deep and less likely to leave little high spots. I like the leather on wood block idea Lucky suggests.

  11. Likes JST, sfriedberg liked this post
  12. #10
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    19,568
    Post Thanks / Like
    Likes (Given)
    2486
    Likes (Received)
    3757

    Default

    If you do not recut that vertex with some clearance, you may find that the "point" of the mating part is riding on it.

    That's especially true if you had to take off a fair bit of material when scraping it.

    The other problem there is that you may (at least I seem to) find that a curved surface has developed back in the corner on one of the two surfaces, and unless there is some better clearance, you'll play heck getting rid of it.

    I've had to use a wedge-shaped piece of HSS, that looks sort of like a cutter for small acme threads, to cut down the curved surface so that it can be scraped normally. That's after re-cutting a clearance.

  13. #11
    Join Date
    Oct 2010
    Country
    UNITED STATES
    State/Province
    Oregon
    Posts
    5,818
    Post Thanks / Like
    Likes (Given)
    5792
    Likes (Received)
    2249

    Default

    Quote Originally Posted by JST View Post
    If you do not recut that vertex with some clearance, you may find that the "point" of the mating part is riding on it.
    Yep. On this particular machine, the points have been chamfered/clipped a bit so they won't ride. However there is no relief groove on the female inside corner and the Biax tips can't get all the way in there.

    I ground out an adequate groove so I could ensure the remaining surface is actually flat. The other side doesn't have this issue because the gib occupies the corner space. If I were doing this again, I would just enlarge the existing chamfer to ensure any "can't get in there" falls into the void.

  14. #12
    Join Date
    Apr 2013
    Location
    Damascus, MD
    Posts
    1,712
    Post Thanks / Like
    Likes (Given)
    5035
    Likes (Received)
    976

    Default

    I generally use a piece of Shammy backed with a piece of wood, or something similar.

    Before scraping the female side of the dovetail I cut a relieve with a slitting saw, in the case the piece has been machined, or with a large power-hacksaw blade.

    Paolo

  15. #13
    Join Date
    Mar 2002
    Location
    dallas,tx
    Posts
    2,736
    Post Thanks / Like
    Likes (Given)
    790
    Likes (Received)
    590

    Default

    Thick, hard felt cut at an angle works well for me.

  16. Likes Richard King liked this post
  17. #14
    Join Date
    Jan 2006
    Location
    Brookfield, Wisconsin
    Posts
    4,466
    Post Thanks / Like
    Likes (Given)
    338
    Likes (Received)
    493

    Default

    Has anyone used an airbrush ?




    If not, what is the reason?

  18. #15
    Join Date
    Mar 2007
    Country
    UNITED STATES
    State/Province
    Wisconsin
    Posts
    528
    Post Thanks / Like
    Likes (Given)
    370
    Likes (Received)
    248

    Default

    Quote Originally Posted by Spud View Post
    Has anyone used an airbrush ?




    If not, what is the reason?
    This is by far the weirdest question you have asked on this forum, bluing is paste. Have you ever set up an airbrush to apply mayo to your ham sandwich before school? If you have not what is your reason for not doing so?

    Scraping is hard physical and mental work, there is no time to make love with an airbrush. I found a thick piece of felt to work or just a corner of a rag or what ever I can find in the 5 seconds I have to find something.

    Digger doug's attitude is starting to rub off on me LOL

  19. Likes sfriedberg liked this post
  20. #16
    Join Date
    Jan 2006
    Location
    Brookfield, Wisconsin
    Posts
    4,466
    Post Thanks / Like
    Likes (Given)
    338
    Likes (Received)
    493

    Default

    Quote Originally Posted by MCritchley View Post
    This is by far the weirdest question you have asked on this forum, bluing is paste. Have you ever set up an airbrush to apply mayo to your ham sandwich before school? If you have not what is your reason for not doing so?

    Scraping is hard physical and mental work, there is no time to make love with an airbrush. I found a thick piece of felt to work or just a corner of a rag or what ever I can find in the 5 seconds I have to find something.

    Digger doug's attitude is starting to rub off on me LOL

    I used dykem for about 1 semester in a machining program; it was not paste like, it was free flowing liquid that would drip easily. If it was thinned a little more, would it work just as well ? At the college autobody program, I used an airbrush to do some touch-ups; it didn't seem slow compared to a thin paintbrush.

  21. #17
    Join Date
    Sep 2006
    Location
    Stillwater, Oklahoma
    Posts
    1,896
    Post Thanks / Like
    Likes (Given)
    150
    Likes (Received)
    1126

    Default

    Quote Originally Posted by Spud View Post
    I used dykem for about 1 semester in a machining program; it was not paste like, it was free flowing liquid that would drip easily. If it was thinned a little more, would it work just as well ? At the college autobody program, I used an airbrush to do some touch-ups; it didn't seem slow compared to a thin paintbrush.

    I think you're confusing layout fluid with marking compound. Time to expand your knowledge.

    Do you remember the movie, The Jerk with Steve Martin? He never realized he was adopted, even though he was the only white kid in a black family so you know where he was starting from. As he's heading off into the big world his dad is giving him some advice. That is, knowing the difference between a tin of shoe shine compound and something the same color that's found randomly in nature.

  22. #18
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    19,568
    Post Thanks / Like
    Likes (Given)
    2486
    Likes (Received)
    3757

    Default

    Dunno, maybe you could thin the Dykem to spray it, but I have no idea why that would be good. I suppose on second thought that you could maybe get a thin coat if diluted, but............... NAW........

    I'll keep using the "pad" method so I know where I'm putting the stuff. I'd get blue enough on the outside, I don't want to get blue on the inside when I breathe in a fog of solvent and blue...... I could really be "singing the blues" if I did......

  23. Likes CBlair liked this post
  24. #19
    Join Date
    Jan 2006
    Location
    Brookfield, Wisconsin
    Posts
    4,466
    Post Thanks / Like
    Likes (Given)
    338
    Likes (Received)
    493

    Default

    Quote Originally Posted by TGTool View Post
    I think you're confusing layout fluid with marking compound. Time to expand your knowledge.

    Do you remember the movie, The Jerk with Steve Martin? He never realized he was adopted, even though he was the only white kid in a black family so you know where he was starting from. As he's heading off into the big world his dad is giving him some advice. That is, knowing the difference between a tin of shoe shine compound and something the same color that's found randomly in nature.

    The T.S. said "blue" so I presumed he meant something like Dykem, but now that I think about I realize I was mistaken.

  25. #20
    Join Date
    Oct 2010
    Country
    UNITED STATES
    State/Province
    Oregon
    Posts
    5,818
    Post Thanks / Like
    Likes (Given)
    5792
    Likes (Received)
    2249

    Default

    Yes, I meant die spotting or marking compound (Canode, or Prussian Blue in grease), not layout die or colored shellac. Dykem makes both hi-spot blue and layout blue, so the brand name alone won't tell ya.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •