Options for replacing 0.01" teflon sheet on HLV-H carriage
Close
Login to Your Account
Results 1 to 15 of 15
  1. #1
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    233
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    123

    Default Options for replacing 0.01" teflon sheet on HLV-H carriage

    I was googling about the subject but see only old posts and no real definitive solutions.

    As the topic name suggests, I have a need to replace the teflon sheet under the HLV-H carriage, the dovetail piece looks ok, but the top is scored and around 30% of it has delaminated already and the rest looks like it wants to come off, I see some corrosion of the steel under delaminated portions, so I want to replace the whole thing.

    I measured the sheet to be aprox. 0,3mm (0.01"), and the sheets themselves seem to be quite cheap, but then there is the question of gluing it to the steel, I see that there is a Permabond TA4610 (datasheet) adhesive that supposedly can adhere to PTFE, and there is even adhesive backed sheet available (waiting to get info about the adhesive from the seller).

    Has anyone here done this with sheets this thin and is willing to share details? With the Permabond the plan was to do few test runs, spread it out using a fine comb working in one direction (miniature version of the sort masons use when they lay tile), do few tests to see how big the comb notches need to be to achieve near 100% glue contact with PTFE yet keep glue thickness to minimum.

    I know about the Turcite and Rulon, but those are thicker, and I don't want to do any machining on the carriage, that would be the last resort if the 0.01" PTFE won't stick.

    Before anyone asks, the dovetail itself is also quite scored, but I know of no grinding shops in 1000km radius that I would trust regrinding it, so for now it will stay as it is, the wear in the middle is minimal (when measured with mic, to the peaks of score marks), only 0.015mm dip (0.0006"), so the new teflon sheet would work as a temporary measure to get the machine operational and prevent more damage (it will see light use, no production, and no real precision required of it either, for now at least).

  2. #2
    Join Date
    Feb 2019
    Country
    UNITED KINGDOM
    Posts
    58
    Post Thanks / Like
    Likes (Given)
    11
    Likes (Received)
    11

    Default

    Gluing a material with one of the lowest coefficients of friction, tricky

    I found this video if it helps, looking at how much he bends the plate the bonding looks strong:

    YouTube

    I've seen this used successfully to bond PTFE to astronomy telescope mount slides but there not under the same kind of load

  3. #3
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    9,798
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2556

    Default

    Quote Originally Posted by jz79 View Post
    I was googling about the subject but see only old posts and no real definitive solutions.

    As the topic name suggests, I have a need to replace the teflon sheet under the HLV-H carriage, the dovetail piece looks ok, but the top is scored and around 30% of it has delaminated already and the rest looks like it wants to come off, I see some corrosion of the steel under delaminated portions, so I want to replace the whole thing.

    I measured the sheet to be aprox. 0,3mm (0.01"), and the sheets themselves seem to be quite cheap, but then there is the question of gluing it to the steel, I see that there is a Permabond TA4610 (datasheet) adhesive that supposedly can adhere to PTFE, and there is even adhesive backed sheet available (waiting to get info about the adhesive from the seller).

    Has anyone here done this with sheets this thin and is willing to share details? With the Permabond the plan was to do few test runs, spread it out using a fine comb working in one direction (miniature version of the sort masons use when they lay tile), do few tests to see how big the comb notches need to be to achieve near 100% glue contact with PTFE yet keep glue thickness to minimum.

    I know about the Turcite and Rulon, but those are thicker, and I don't want to do any machining on the carriage, that would be the last resort if the 0.01" PTFE won't stick.

    Before anyone asks, the dovetail itself is also quite scored, but I know of no grinding shops in 1000km radius that I would trust regrinding it, so for now it will stay as it is, the wear in the middle is minimal (when measured with mic, to the peaks of score marks), only 0.015mm dip (0.0006"), so the new teflon sheet would work as a temporary measure to get the machine operational and prevent more damage (it will see light use, no production, and no real precision required of it either, for now at least).
    .
    turcite is glued on then machined. it can start much thicker but after machining can be much thinner. usually one side of turcite is acid etched so glue sticks better. its far more sophisticated then many realize.

  4. #4
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    233
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    123

    Default

    I'm fully aware of the challenges, and I'm quite certain it is not turcite or other types of "filled" PTFE, it looks and feels like pure PTFE, on couple Fadals I've seen around here, turcite/rulon seems to be quite thick, there are obvious signs of epoxy (or other type) adhesive used to bond it to CI, and even after it was machined/scraped and after decades of neglect it is over 1mm thick, but on this HLV-H (and as far as I could find other people talking about this subject), the material is indeed pure PTFE sheet, and final thickness is very close to what I see on my machine, I haven't torn it off completely, but so far I haven't seen obvious signs of glue used to hold it, so one guess is that it might have been a cyanoacrylate glue to hold it, which supposedly could be used with etched PTFE and the right kind of primer.
    One person suggested that originally it was glued thicker, fly cut and scraped to fit, I'll take a closer look at the remnants on this machine to look for scraping signs, which should be there, since the CI gib that rides directly against the steel dovetail does show scraping marks, worn, but they are there, but I didn't see any on the PTFE sheer, not on the top piece, nor the far dovetail. I don't exclude the possibility of the gib being tampered with though. Thankfully the dovetails don't have the typical wear ridge, they actually look quite good considering the condition of the top surface, which was probably due to excessive use of sand paper, which I found lots of small pieces in the cabinet and other recesses of the machine... way wipers were a distant memory, some pieces were still left under the screws on the tail stock side of the carriage.

    The machine in question would have otherwise be most likely parted out and scrapped, things like lever collet closer, change gears at the end of the threading gearbox and feed motor were already missing, top slide has been "adjusted" with a steel hammer more than a few times, the thing has endured some tough time in the hands of French machinists which didn't seem to give any love to it, so as far as I'm concerned, any effort in trying improving it over leaving as is in fear of making it worse, is overall positive for it.
    p.s. The idea is to keep the machine, not just prop it up, slap some fresh paint on and sell to some unsuspecting victim.

  5. #5
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    9,798
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2556

    Default

    a lot of turcite is machined and not scraped and its milled smooth enough you could easily think it was ground.
    .
    there are "tape" out there, some various materials like uhmwpe that some maintenance person might put on as a quick fix. adhesive already applied in a roll, although how good the adhesive is is hard to say. its right up there with aluminum foil tape that a maintenance person might apply as a quick fix. sometimes it works ok and sometimes does not last long
    .
    teflon normally doesnt glue that well unless treated like acid etched. part of it being slippery and not much sticks to it also makes teflon hard to apply.
    .
    uhmwpe (polyethylene) is often confused with teflon
    .
    also have used a fiberglass tape with teflon coating. used on conveyor side shoots so boxes move along easier. its tough cause its fiberglass, only outside is teflon coated

  6. #6
    Join Date
    Feb 2019
    Country
    UNITED KINGDOM
    Posts
    58
    Post Thanks / Like
    Likes (Given)
    11
    Likes (Received)
    11

    Default

    Quote Originally Posted by jz79 View Post
    I haven't torn it off completely, but so far I haven't seen obvious signs of glue used to hold it, so one guess is that it might have been a cyanoacrylate glue to hold it, which supposedly could be used with etched PTFE and the right kind of primer.
    It might be a stupid question but can you tell if the underneath surface has been etched, after you've torn it off is the back in good enough condition to see what the surface might have been like?

    And just a warning, if you do glue on something thicker and machine it down using a fly-cutter or similar, PTFE is slightly compressible as well as slippery so the cutter (unless it's extremely keen) will skid over the top and you will end up somewhere between 0.005" and o.010" over size, the effect get's worse the smaller the cut you take so after the finishing cut the dimensions end up wrong. You may know this already, sorry if you do

  7. #7
    Join Date
    Dec 2008
    Country
    UNITED STATES
    State/Province
    New York
    Posts
    9,798
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    2556

    Default

    i machine turcite with uncoated honed inserts made for aluminum (sharp).
    .
    coated inserts that leave a mirror finish on cast iron are often dull or edge rounded to apply a type of burnishing action. when used on plastic they often push material and leave burr at edges of mill pass often sticking up many .001", that is new out of the box they are not sharp enough to bite into a soft material and its not good to be pushing the plastic surface around

  8. Likes Ember liked this post
  9. #8
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    233
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    123

    Default

    here are few pictures of the sad carriage, lighter patches have already delaminated, that one pic shows embedded dirt/grit in the leading edge of the teflon piece (that is a mm scale btw), and the pic where I hold a corner up, that corner I tried to lift to see the bond holding power, and it felt like taring off a good masking tape, it isn't sticky, teflon face looks matte, probably a sign of etching

    talked to a teacher in local tech uni that does some material testing research, and he agreed to do some comparative compression tests on the worn piece still glued to the carriage, and the replacement material I ordered, I ordered both the plain teflon sheet (with one side already etched) and the adhesive backed variant, I'm curious how spongy the adhesive backed one will be compared to the original and the replacement

    tried touching it with soldering iron, it wouldn't melt even at 400C, that is the max the iron would go to, so it is quite safe to assume it is pure teflon

    one thing I forgot to mention, the place where the carriage dovetail faces meet, on the far side, there is a relief cut there, and the top teflon piece was "hanging over" into this relief, meaning - it had no support when it was glued, measured thickness of that overhung material - basically the same as the scored/worn portion, so I'm starting to think it might have not even been fly cut, because the cutter definitely wouldn't have cut that unsupported overhung teflon, should have been thicker if there was any machining done

    I'll update the thread after the load tests

    img_20190305_153800.jpgimg_20190306_105102.jpgimg_20190306_105110.jpgimg_20190306_105137.jpg

  10. #9
    Join Date
    Jan 2002
    Location
    West Coast, USA
    Posts
    7,331
    Post Thanks / Like
    Likes (Given)
    439
    Likes (Received)
    4808

    Default

    Have no idea if it would work (I suspect not), but I buy and apply self-adhesive Teflon sheets for re-surfacing microscope stages. The stuff is very sticky -- once set in place only a lot of heat and a razor blade at the bond line seems to disturb it. The point being that the makers of this stuff seem to offer an adhesive, in a fairly controlled thickness, that sticks.

    I've bought this stuff in sheets from (if memory serves) from .008" to .040". I'm not at all sure it would hold up under a carriage - indeed I doubt it -- but sheets are cheap enough ($30 or so a square foot) that someone might want to try this??

  11. #10
    Join Date
    Feb 2019
    Country
    UNITED KINGDOM
    Posts
    58
    Post Thanks / Like
    Likes (Given)
    11
    Likes (Received)
    11

    Default

    Quote Originally Posted by jz79 View Post
    talked to a teacher in local tech uni that does some material testing research, and he agreed to do some comparative compression tests on the worn piece still glued to the carriage, and the replacement material I ordered, I ordered both the plain teflon sheet (with one side already etched) and the adhesive backed variant, I'm curious how spongy the adhesive backed one will be compared to the original and the replacement

    tried touching it with soldering iron, it wouldn't melt even at 400C, that is the max the iron would go to, so it is quite safe to assume it is pure teflon

    one thing I forgot to mention, the place where the carriage dovetail faces meet, on the far side, there is a relief cut there, and the top teflon piece was "hanging over" into this relief, meaning - it had no support when it was glued, measured thickness of that overhung material - basically the same as the scored/worn portion, so I'm starting to think it might have not even been fly cut, because the cutter definitely wouldn't have cut that unsupported overhung teflon, should have been thicker if there was any machining done

    I'll update the thread after the load tests
    Looking at how flexible it is, and it won't burn, it's unlikely to be filled, even if it is and you use pure it will still work, it just won't last quite as long. If there's an overhang that's still the same thickness it's not been machined. Can you tell if there's evidence of glue on the back of the overhanging piece? if there is it might mean it's been replaced in the past with an adhesive backed sheet

    you could get some adhesive and try gluing a small piece of the etched to a scrap piece of metal as well as a small piece of the adhesive backed, then measure the height with a depth gauge to check the glues don't raise it up to much. Try to pull them both off, use which ever is harder to pull off, (if it's stuck better than the old PTFE sheet was, if not you'll have to rethink)

    Quote Originally Posted by DMF_TomB
    i machine turcite with uncoated honed inserts made for aluminum (sharp).
    .
    coated inserts that leave a mirror finish on cast iron are often dull or edge rounded to apply a type of burnishing action. when used on plastic they often push material and leave burr at edges of mill pass often sticking up many .001", that is new out of the box they are not sharp enough to bite into a soft material and its not good to be pushing the plastic surface around
    Thanks for the tip, I tried it - beats using HSS Steel and honing the edge with an oil stone

  12. #11
    Join Date
    Jul 2001
    Country
    UNITED STATES
    State/Province
    North Carolina
    Posts
    1,894
    Post Thanks / Like
    Likes (Given)
    148
    Likes (Received)
    363

    Default

    Watching this thread for recommendations as to where
    to buy this Teflon sheet that is able to be glued
    or stickied to the carriage. I have an HLV-H that
    the Teflon sheet is coming loose as well. Please
    post again when you find a source for material that
    is suitable.

    Thanks.
    -Doozer

  13. #12
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    233
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    123

    Default

    I found this site via google search - ETCHED PTFE SHEET STOCK - Order Lab Supplies Online & Save , they also responded to my email quite quickly, I haven't placed an order yet though

    First I'll test out the Permabond TA4611 glue, should be here next week, it supposedly works on unetched PTFE, if it does, I have already ordered some sheets from asian sellers on ebay which should be here soon as well, if the glue works on the un-etched PTFE, I'll stick to the cheap asian PTFE, if not, will place an order at scicominc.com, shipping will probably cost me more than those PTFE sheets

    I did try Loctite 770 (polyolefin primer) for gluing low energy plastics, and it seems to work, but not all CA glues I have performed the same, "rubber reinforced" CA worked much better than regular CAs I tested, in fact, the rubber filled CA stuck to the PTFE piece when I glued it to a steel substrate, meaning when I tore the PTFE off, the glue residue was almost all on the PTFE piece, nothing on the steel (and it was cleaned properly), other CA glues stuck to the steel better but the bond with primed PTFE was much weaker, when I tried to peel the rubber filled CA test piece off of the steel, it held pretty much the same as the yet un-peeled pieces on the HLV-H carriage, suggesting that this is what they probably used at the factory, but I think it will be quite difficult to glue such a large piece using the CAs I have, they cure nearly instantly when pressed thin enough, so getting a good level bond might be complicated, that Permabond 2 part acrylic has some working time, not a lot, few minutes, but I figure I will have a much better shot using that than the CA, I just hope it sticks to the un-etched PTFE well enough...

    I'll update once the Permabond stuff arrives and I'll have time to do some tests with it

  14. #13
    Join Date
    Jan 2005
    Location
    The Netherlands
    Posts
    5,620
    Post Thanks / Like
    Likes (Given)
    252
    Likes (Received)
    1397

    Default

    I did have a material once for this purpose Also white I do not think it was PTFE
    The back had a hairy surface to improve bonding
    Do you think you can hold the thickness of the glue in the tolerance that you need
    I would keep it in the back of my head that I need to scrape it anyway

    Peter

  15. #14
    Join Date
    Sep 2009
    Location
    Apex, NC
    Posts
    1,425
    Post Thanks / Like
    Likes (Given)
    1
    Likes (Received)
    706

    Default

    Someone else will probably chime in, seems I recall one of the rebuilders commenting on adhering and scraping the teflon. Teflon can be glued, but as noted above, it's etched and/or plasma treated (plasma-treating is very effective, but effectiveness "ages" away unless glued relatively soon). McMaster has some etched bondable PTFE films (McMaster-Carr).
    Looks like someone may have used water-based coolant, a big nono with HLH's.
    Attached are some pictures of good-condition teflon, still with some scraping textures present (I may have posted these before).


    img_4936.jpgimg_4935.jpg

  16. Likes Stradbash, jz79 liked this post
  17. #15
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    233
    Post Thanks / Like
    Likes (Given)
    59
    Likes (Received)
    123

    Default

    Quote Originally Posted by Peter from Holland View Post
    I did have a material once for this purpose Also white I do not think it was PTFE
    The back had a hairy surface to improve bonding
    Do you think you can hold the thickness of the glue in the tolerance that you need
    I would keep it in the back of my head that I need to scrape it anyway

    Peter
    I tried heat on a piece I peeled off, and it wouldn't melt at 400C, it feels (cuts with a scalpel) like PTFE, glues (meaning nothing wants to stick to it) like PTFE, looks like PTFE, so there is an argument to be made it is PTFE

    when I peeled off the piece, the back side was not semi glossy like virgin PTFE materials usually are, it was smooth and matte, I presume it was etched as a preparation for bonding

    regarding the glue, I ordered some extra for testing, I plan to use something alike a notched trowel to spread the glue in even lines so air can escape and when pressed it should flow and make (hopefully) an even thickness film, that is the plan anyway

    the really difficult part it seems will be to find a place that can grind the top of the dovetail to remove the scoring marks, probably 0,1mm would need to come off, there are only ex soviet era machines around here, no machine building was really done in the country, and I doubt those might pop up somewhere around here would be in a condition to hold even 0,05mm over the 1050mm length of the dovetail, there used to be a machine building plant in Lithuania in soviet times, but I have no contacts in Lithuania at all, will have to do some digging...

    edit: I just realized I posted the wrong link, same site, but the product I was looking for was "film" not "sheet" - ETCHED & ADHESIVE BACKED PTFE FILM - Order Lab Supplies Online & Save

  18. Likes Doozer liked this post

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
  •