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Non Marring Shc Screws...?

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by EmilioG, Jan 1, 2017.

  1. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    What is the best way to put flat ends on SHC screws? There are no non-marring versions, only in set screws.
    Can I just grind a flat end and polish or is this a lathe or mill job? I built a steel armature that uses SHC screws to clamp the bars, but the SHC screws leave ugly marks on the steel bars. I bought non marring set screws for my boring head so the boring bars don't get marked. Not available for cap head screws, unless someone knows
    a source.
     
  2. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    How about non marring washers in between?
     
  3. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    The NM washers Won't work for my application.
    The SHCS must be faced off or ground I imagine., leaving them flat and smooth.
     
  4. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    Wait, I think you are speaking of the end of the threaded portion. If the screws are big enough you can drill out the ends and make brass or aluminum inserts to the thread ID dimension. If they will not fall out in use, just drop some slugs of the correct diameter down the holes and follow with the SHCS. If the screws protrude below the armature, leaving a space before contacting the steel bars, you could put cup shaped end protectors on them.
     
    Jimsehr likes this.
  5. projectnut

    projectnut United States Active Member Active Member

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    McMaster offers a series of non-marring socket head screws. They're either brass or nylon tipped and range in size from 6-32 to 3/8-16. Here's a link to the index page. The non-marring ones are in the second from the bottom row:

    https://www.mcmaster.com/#standard-socket-head-screws/=15q3xan
     
  6. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    Thank you. I've purchased every type of SHC fastener and set screw. I prefer steel alloy or SS. Bob, I may go with the inserts, I can just glue a brass or bronze "cap"
    to the SHCS. Why can't the ends just be ground or faced flat on a lathe? Is the alloy steel too hard? I have a Criterion set screw that came with my Criterion boring head that has a machined flat set screw for the boring bar. IMG_20161106_122348802.jpg
     
    dfletch likes this.
  7. Bob Korves

    Bob Korves H-M Supporter - Premium Content H-M Supporter-Premium

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    If the hardness of the fastener tip is near the hardness of what it is rubbing on, oar harder, the surface will be marred, regardless of surface finish, due to galling. A highly polished hard surface might not scratch the surface as much, but it will indent it. A softer, more lubricating material that is not abrasive is usually the choice for non marring fasteners. I still do not know the nature of what you are specifically doing here, but if there is room in between the surfaces you might be able to get by with just a strip or pieces of brass shim stock. Is the photo related to this job? I thought you were using SHCS, not socket set screws...

    Stainless makes for poor fasteners in most every respect except corrosion resistance. Many have found that out on Aloris type tool holder set screws.
     
  8. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    That image is a set screw for my boring head. The end looks like it was machined flat. so I thought that a similar SHCS could also be machined flat.
    I use SS fasteners when I want to avoid corrosion and galling. The soft inserts may be OK temporarily, but I'd rather have flat ends on the SHCS.
    Can they be machined flat?
     
  9. dulltool17

    dulltool17 United States Active User Active Member

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    Emilio- I think we're struggling to better understand your application. Maybe a sketch would help. Based on his post here, I'd say Mr. Korves is one of the sharper knives in the drawer; if he can't decipher your needs, I'd say a bit of clarification is needed.

    Certainly, you can machine anything flat, but how well the configuration holds up depends on the whole picture. Also, for what it's worth, 300 series stainless is notorious for galling.

    just my $0.02
     
    EmilioG likes this.
  10. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    Thank you, yes, I know Bob knows his stuff. I respect his opinions very much.
    I took care of it. Ground them flat, works perfectly for my needs. I've had no problems with galling since it's 303 SS SHCS against mild steel rods. I also use various Dow Corning MolyKote anti seize pastes made for threads, including SS.
    It's a metal free, silicone based compound, DC Molykote M77. Great stuff.

    I just wanted to know if anyone has ever ground down SHCS flat. Alloy steel screws. Thanks to all. It can be done, EZ PZ. :) Chucked them up in DP and lowered them onto a stone.
     
  11. mikey

    mikey Active User H-M Supporter-Premium

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    I usually just face the end of the screw, drill it and fit a Delrin tip with a nub to fit the hole in the end of the screw. Last for years, does not mar and locks down solidly. If locking onto a dovetail, I make a separate insert with the nose of the insert matching to slope of the dovetail. The rear of the insert is flat and the locking screw bears on that end.
     
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  12. EmilioG

    EmilioG United States Active User H-M Supporter-Premium

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    That's what I had in mind, but I don't have any Delrin. I'll have to order some from McMasters. Excellent.

    EDIT: I found the shorter pieces of Acetal rod for less from Msc and free shipping.
    Mike, Did you use acetal w/PTFE? slippery delrin?
     
    Last edited: Jan 2, 2017
  13. wmgeorge

    wmgeorge United States H-M Supporter - Premium Content H-M Supporter-Premium

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    I hate to say this but those of you who are shooting sports people a HMR 17 or .223 copper jacketed Lead bullet tip makes a nor marring sub for a factory made non marring set screw. If you want to make a brass one then do so but this works.
     
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  14. mikey

    mikey Active User H-M Supporter-Premium

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    Just plain acetal/Delrin rod - its all I have in my stash.
     
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  15. richz

    richz United States Active User Active Member

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    On smaller set screws I have used .090 weed eater line.
     

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