Best way to prevent breaking teeth on holesaws when mitering tubes- Mtbr.com
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  1. #1
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    Best way to prevent breaking teeth on holesaws when mitering tubes

    Hi all,
    I've looked around, and found some threads that sort of address this, but none seemed to fully address it, so I decided to make a new thread. I've recently purchased a Barker AM horizontal mill. It's smallish, and seems nice and solid, but has limited adjustability (as is) in terms of speed, and the feed is lever instead of micrometer. I know this one was used to miter tubes in the past, but the info I could get from the seller was limited. I've been experimenting, and it seems to work well, but I'm noticing that I've already broken some teeth on the Ruko hole saws I have, and I want to see what I can do to get the saws to last longer. I've tried to use very slow and steady feed, and not really push very hard so as to keep the teeth from catching, and I didn't hear or feel any signs of catching, so the feed seems ok, but maybe not? Speed may be a bit high, but it also seems like higher speeds would make it less likely to catch a tooth. No? As I calculate it, the machine is running at about 430 rpm. Also, what do people find works best as coolant? If I remember correctly, many folks don't use anything. Is that correct?

    Thanks so much!

  2. #2
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    My only thought would be to see if the gibs on your ways need tightening down? If there's play in the assembly that could cause the cutter to take too big of a bite. Especially if your feed handle doesn't allow for smooth motion, having the table travel be a little less free might be a good thing.
    I notch in a vertical mill, and I will just barely set the quill feed lock to give the feed a more controlled motion. Not sure if there's an equivalent on your mill. I haven't tried using a horizontal mill, but I sure would like to for acute angle notching.

  3. #3
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    Yeah, Ok. The gibs seem tight, but the lever that controls the actual feed is loose. I need to make a new part for that in order to get rid of the play. It kind of didn't seem like it was a problem because the gibs were tight and everything seemed to be feeding smoothly, but that's a very good point, and I guess, to bend a saying, the proof is in the broken teeth . What do you use as far as cutting fluid or coolant? Any? Thanks much for the input!

  4. #4
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    Can you slow down the rpm?

    I have a small bench top mill and have no issues with breaking teeth on hole saws. I run about 250rpm and the feed is hand run slowly.

  5. #5
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    I have to find different pulleys, which has been a hassle so far, but that would be my only bet as far as slowing down the rpms. I do feel like the play in the bolt holes in the connecting rod that transmits the lever feed to the table/vise could be problematic too, so I'm trying to figure out a good way to make a new one of those that's really solid. Not there yet. Super frustrating, because the miters coming off this thing are stunning, and it's so fast compared to hand filing, but if I'm getting like 4 cuts out of each saw, it's going to be really pricey, not to mention wasteful....

    So it looks like I've got a couple of paths to look into.

  6. #6
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    The low range speeds were out of commission on my BP clone for a bit and I was mitering at 660 rpm hand feeding the quill for a good while with zero issues. I know, I know Iím a hack... I imagine the hole saw doesnít last as long in these conditions, but I sure canít imaging snagging a tooth at that rpm. I have heard great things about liquid dish soap as cutting fluid for hole saws from Paul at Rocklobster, havenít tried it yet, though. ALSO, if you still canít figure it out, I think the starrett hole saws I have have about double the tooth thickness of the Rukoís I have, that should last longer. Best of luck!

  7. #7
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    Some hole saws just throw teeth. Not having slop in your machine is good but check the RPMs. You can download a strobe app on yer phone that can be helpful. You'll want to run between 80RPM and 200RPM depending on the size of the hole saw (faster for smaller saws). I have a machine that only has one speed and run it at 90ish for everything. Slow speed and really slow feed.

  8. #8
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    I'm a machinist by trade, and have no idea what a Ruko hole saw even looks like!! However, if it's braking teeth, i'd suggest your tooth count is too low, ideally you always want a minimum of 2 teeth in contact with the workpiece. (that may not be possible on thin wall tubing) Next common reason for tooth breakage is slop or backlash somewhere. It's effectively pulling the workpiece and cutter together, and overloading the single tooth thats in contact. Stick a DTI on it, and SWING on it and see how much deflection you can achieve. Some VERY rough calcs for cutting steel/stainless with HSS would suggest approx 150rpm for 30mm diameter cutter. Personally i'd definitely be using some form of cutting lubricant.

  9. #9
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    A picture is with a lotta words, post a pic of your setup. I agree that there may be flex somewhere in the setup whether it being from the tube sticking too far out from the tube block (or from however youíre holding the tube), or using a long arbor with some runout, or loose gibs/table slop. I canít tell you how many photos Iíve seen of the tube sticking out several inches from the fixture and shaken my head. The tighter the setup and closer the cut is to the tube block the better!
    But it can just be the out of round hole saws and itís hard to get them NOT to snag.

    Iíve tried a lot of hole saw brands as Iím sure many here have too, itís always a gamble on what you get from any of the makers. Iíve had Starretts, Lennox, Roku, but the blue ones that I like the best (Google: Missouri precision tools rock hard hole saws). They are 10tpi and still hit or miss with roundness but donít snag as bad. Not super durable like the Lennox but the high tooth count is awesome for thinwall tubes.

    Slow speeds and feeds and no need for cutting fluid but I know a brush with Dawn soap works fine.

    Lastly, Iíd take the grinder to the bad teeth on the outside where theyíre snagging. Just take off the sharp points. It will be a tad smaller diameter but the file to fit is worth it.



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  10. #10
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    What kind of motor is on the mill? If it is a single phase, then slowing it down may be challenging. However, on my Bridgeport 1J, I installed a $99 Teco VFD to convert 120VAC to 3 phase power. The VFD also lets me run the output frequency up and down to increase spindle speed, it works very well.

    I don't build bike frames, I just like to read the forum. I use the mill for other stuff, but often notch tubes or run a hole saw in it.

  11. #11
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    I'll definitely second what Whit said, post a picture of your setup if you can. And if you're not already clamping the tube as close as possible to the cut, do so. Also make sure you have as short of a hole saw arbor as you can get away with. Although with the work envelope on a Barker, your options may be limited.

    You said there is play in the bolt holes of the connecting rod on the hand feed lever? That could allow a tooth to catch and pull your tube forward into the hole saw, breaking the next tooth that comes along. To test this, either try to find some way to put back pressure on the table (pushing the table AWAY from the hole saw) or tighten the gibs or table lock so that the table doesn't slide easily, then do a miter. Those should prevent the table from jumping forward during a cut, and if your hole saws last longer, that's the problem.

    But if it is, fix the connecting rod holes, don't just leave the gibs tight because you'll wear the dovetails out.
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  12. #12
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    Switch to these fine tooth hole saws.

    Missouri Precision Tools, Inc.: Rockhard HSS BiMetal Fine Tooth Hole Saws


    If that's not an option, you can take a Dremel or some other grinder capable of fine work and take the tips and outer edges off of the teeth. You want less back rake on each tooth. The teeth will be more rigid and won't have as much room between so they won't snag as easily.

    And then finally, slow down your feed. I have run mine at fairly high speeds and haven't had issues but if I try feed the quill too fast, I get snagging and the tube deflects etc.. Finally Finally, make the tube holding as rigid as possible as suggested above.

  13. #13
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    As mentioned before you need stiffness, in the machine, and in your workholding. Don't think I saw it mentioned, but step one is to throw away the arbor designed to fit a drillchuck and to come up with something solid,

    And looki into a VFD to get the revs down

  14. #14
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    Thanks for all the replies! I was away from the computer for a few days, but I think I've mostly fixed the issue by tightening up the feed. I remade the lever, and I think that really helped. I still need to slow down the RPMs, but because that will require new pulleys, it's going to take longer. I've been clamping as close as possible to the cut, so I think that's good, and I've also switched to a different hole saw brand (just some Milwaukee ones I had around) and haven't broken any more teeth. Anyway, I have some homework to do in terms of getting the RPMs down, but overall I think I'm making progress on this!Name:  barker - 1.jpg
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    This photo is of my next wrong turn. I'm trying to figure out how to miter unicrown blades without crazy tooling, so I'm seeing if I can rig up my drill press vise to do it. Not sure if it's going to work since I don't have a ton of purchase on the tube block, but the material is nice and thick. Note: the hole saw in this photo is one that I've been experimenting with, and it's pretty used. No broken teeth yet, which is impressive, so something must be better! Also note that this setup has the tube hanging waaaay farther out than anything I've done to this point, so that's another way it's probably going to go wrong....Hmmm on third thought, how is everyone mitering unicrown blades? Maybe that's the question I should be asking here

  15. #15
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    For unicrowns Iíve seen some use a tube block like your photo but having tried that i would not recommend it.
    The simplest method is sandwiching the blades between plate, keeps them phased that way. Several builders have photos of this type of setup on their Instagram or Flickr so should be a quick google for an example.


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  16. #16
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    Quote Originally Posted by Bpotts View Post
    Also note that this setup has the tube hanging waaaay farther out than anything I've done to this point, so that's another way it's probably going to go wrong....Hmmm on third thought, how is everyone mitering unicrown blades? Maybe that's the question I should be asking here
    Please put a machinist jack underneath and a clamp on top, that's way to much stickout and leverage

  17. #17
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    From a machinist point of view, 1st off clamping method is wrong. The easiest way that tube has of moving in it's clamp is to rotate. If the tube does rotate it results in the teeth at 1 side of the cutter taking a bigger bite, hence snapping teeth. 2nd, your clamp is too far from the cutting edge, there is tons of room for flex. As above the flex in this case results in the top teeth taking a bigger bite and chipping teeth. You need a fully rigid support under the tube so there is zero deflection, ideally with another clamp pressing down. This clamp will not need a great deal of force, it's job is only to stop the job vibrating and bouncing up off the support.

    Next up those style of hole saws have a high rake on the cutting teeth, any backlash in your saddle will result in the job being pulled into the cutter, again snapped tooth territory. Everything has backlash, it's the nature of ACME threads, they cannot operate without it. So either a low rake cutter, high tooth count (so at least 2 points in contact at any time ideally) and just leave the traverse lock partially engaged.

  18. #18
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    Thanks for all of the great comments. And yeah, I know that this way of holding the tube is totally awful, but I was hoping to get away with not making a whole new tool. It seems like everything I do requires a new tool, and I'm just getting impatient . But points well taken. Also, the holesaw I'll be using for the fork is different and should be better, though oddly, as I said before, this one, which seems to be a bad choice has had 0 broken teeth, and has cut cleanly, whereas the ruko fine tooth one I was using before was breaking teeth like nobodies business. Who knows why...but anyway, now I'm trying to figure out a good fixture for this. I'll post a photo when I've made some progress. Thanks so much for all the great help!

  19. #19
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    I think adequate clamping is a very hard part of machining to learn. Like most things, practice is important. Hopefully some of my long rambling post made sense. Set-up is always key to a good cut, hope I wasnít too negative!!!! It could well be the actual tooth geometry thatís making the difference.

    I wouldnít abandon what youíve got, the full tube clamp makes a superb starting point. Iíd just add support nearer to the cut.

  20. #20
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    Cord: Thanks, and no offense or whatever taken. I actually feel like of the things I would tend to do wrong, clamping in something too flimsy would *tend* to not be one, just because I have been using a drill press for ages, and have had some scary moments as work gets torn out of your hands and the like. But your points are all well taken, and I have gone back to the drawing board because while the setup I had there felt pretty secure, it really isn't ideal, and I think spending more time making a fixture that will keep everything in phase will be time well spent. I'll post pictures when I have something to show!

    On another point, of this now-partly-derailled thread, how are folks mitering the dropout end of unicrowns? In the past I've done all parts by hand with a file, and it's just something like days of trial and error in terms of fitup. It usually comes out all right, but it easily takes as much time to make a unicrown as a frame, just because the mitering is such a pain! Crazy! I'm actually thinking that I could go in and file the ends when they're clamped in my mitering fixture, even though I don't think it will hold the legs securely enough to do the cuts in a mill. I guess what I'm asking is: in working out this fixture, is it worth trying to design in a way to hold that end of the leg securely enough to do that process too, or is it better to do it separately? Sure would be nice to do it all at once.

  21. #21
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    You're asking a lot of questions all at once, and unfortunately the answer to most of them is a specific tool. Although you can probably get by with some things you have laying around, you may have to get creative.

    Mitering the dropout end of the fork blade depends on a couple things, like is your fork blade tapered? And is your dropout a tab-style or wright style? If it's tapered, you're going to need some way of hanging on to tapered tubing, similar to ways folks hang on to tapered seat and chainstays for mitering. If it's straight, you're good to go, just use a tube block. Slot or miter to your heart's content.

    I miter the dropout ends of my forks first, then tack them to the dropouts and my fork mitering jig hangs on to the dropouts via a dummy axle. This keeps everything in place and also give the jig more leverage to hang on to the fork blade. This is the only photo I could find of it set up:

    Best way to prevent breaking teeth on holesaws when mitering tubes-20190109_142620.jpg
    It turned the image on it's side. No idea how to fix it. You get the idea though.

    This setup isn't perfect, but it gets the job done, and it was incredibly easy to make with a couple pieces of 80/20. Toolmaking may seem frustrating and time consuming, but it's hard to avoid in certain circumstances.

    If you're hell bent on using what you have, I would turn your vice 90 degrees to where it is now and clamp the fork blade directly in the vise (no tube block) so that it holds on to the bend and has a harder time twisting. You can even turn the vice a few degrees to account for whatever rake you're going for. A bigger vise would be better.

    Good luck! Feed that cut slowly.
    Myth Cycles handbuilt bike frames
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  22. #22
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    Actually, I just looked at your picture again. Don't do what I suggested unless you find a bigger vise, that thing is tiny.
    Myth Cycles handbuilt bike frames
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    http://www.mythcycles.com

  23. #23
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    Thanks for the thoughts! I've rebuild the fixture, and have used it now and it's super solid. Also, the vise shown in that other photo is my drill press vise, which is actually pretty solid, but it is fairly small. My mill vise is much larger and definitely solid. I'm still working on how to miter the dropout end of the blades because the blades are tapered, and I'm using hooded dropouts. I'll get it, but it might take a little time.

    Yeah, I like toolmaking, but it just gets a little tedious at times, when you've been doing it non-stop and you just want to build some bikes . Things are getting there though!

    Now I just need to get better at centering the blades, so the next part of this fixture is going to be something to really securely center the blades. Right now there's a ring up in between the plates that clamp the blades, but because I can't really see it when things are clamped, it's too hard to get things really centered.
    Best way to prevent breaking teeth on holesaws when mitering tubes-img_3439.jpg
    Best way to prevent breaking teeth on holesaws when mitering tubes-img_3441.jpg

  24. #24
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    Here's something left field for you. Get the tube cut on a tube laser. Find the right supplier and the profiles will be so cheap you wont be bothered trying to mitre cut tubes ever again.....

    That said. You if your bending the tube cutting of the green afterward then mitreing like the attached photo you are a bit screwed. Back to milling, or possibly waterjet cutting.

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