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  1. #21
    HuFlungDung is online now Diamond
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    I have also experienced this problem at various times. I suspect it may be due to the small amount of support given to the part, and the pressure of broaching allows the part to tilt and then the broach hogs in.

    What seems to work is to put a C clamp (or a parallel clamp if you have one) over the leading end of the broach, to clamp it down firmly to the bottom of the guide bushing groove. As you can imagine, this rigging does not last very long as the advancing broach tends to push the clamp right off the end of the bushing. But usually, after cutting an inch or two this way, the broach will be properly seated and behave itself for the remainder of that pass.

    In an arbor press setup, I have even managed to reach underneath and just with finger pressure, have managed to make the broach stay seated until it is fully engaged in the cut, so it does not take enormous pressure to make it stay. Relax and re-advance the press frequently to give the broach and the work a chance to square up to the press table.

    I usually use a 4 to 6 inch long guide bushing, so I have ample room to reach underneath to apply pressure (or a clamp) to the end of the broach to seat it in the bushing.

  2. #22
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    jackal is offline Titanium
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    Hello TOH,

    How long is the part ? How long is the broach bushing? I have had the same problem with broaching and if you have say; a 2" bushing and a 4" long part this will happen. Also you might try shimming under the part. Put maybe some banding material or something about .020 or .030 under the side where the broach is coming through. Sometimes this will allow for the angle and the bottom side won't be as deep.

    I am like you on the matter of the tool. Some jobs I do for friends or family , I just charge for the tool that has to be bought and consider it a free tool for the labor. If is is something I may never use again. If it is something like a grinder or a saw ,I might go with the better brand, and through that job and others I will have the tool for free.

    Glad to see you doing this . You have to start somewhere.

    Jackal

  3. #23
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    One other thing that sometimes helps is to very lightly grind the teeth. I've done this with a compound magnet sine vise & surface grinder (6x12), but it wouldn't be too hard with most any milling vise with 6" jaws.

    Start by measuring the height of the first tooth (the shortest one). Then measure the height of the last tooth. Finally, measure the distance between those two teeth. Trig out the angle needed so the broach teeth are parallel to the surface grinder bed and set the broach to this angle.

    Dressing the entire length of the teeth, as little as one or two thou, will completely change the way the tool cuts.

    Tapmagic works well for broaching (and boring on the mill or lathe ).
    --------------------
    Barry Milton

  4. #24
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    Please don't let GaryE be a turnoff, he's our resident extremist on the Buy American issue.
    Nope. Sorry.

    I am.

    You buy a tool for $20 and it doesn't work. You saved $30, ruined a couple of parts, and wasted a bunch of time. And how much did the ruined parts cost in time and material?

    So you go buy another one, for another $20, which may or may not work. Now you've saved yourself $10, wasted more time, and possibly damaged more parts if the second one doesn't work.

    False economy is just that. Buy the right tool to do the job. If you underpriced the product, at least that shortfall went to buy a good tool and a good lesson.

    Leigh

  5. #25
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    Buy the right tool to do the job.
    Sometimes it's hard to figure out which is good, better or best. For a long time, I looked for a Bridgeport. Finally, a machinery dealer called & said he had a nice J-head variable speed with chrome ways.

    The BPort was sweet. A 1990 machine, quiet head, etc. $5500 without DRO or power feed, which meant $7000 as I wanted it. Right next to it was a homely ENCO mill-drill, Acu-Rite DRO & power feed already installed for $1600. The ENCO got purchased, a decision I've never regretted. It makes money every time the spindle turns & it refuses to quit.

    Would the BPort make more money? Maybe for someone who needs all the features that are built in to that machine. But the ugly ENCO keeps chugging along, drills & taps three or four hundred holes every month, and left me with $5400 in the bank.

    I'm not an advocate for ChiWan tools, whether it's a machine tool or a broach. But I'd have probably done the same thing as TOH, buy a disposable tool, do the job, move on.
    ----------------------
    Barry Milton

  6. #26
    hkotyre is offline Aluminum
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    The hydraulic press you are using, does it have a set of guide rods and use a standard jack if so I have found that the arraignment tends to walk one way or the other with a broach and have had to offset the broach a little on starting it. It was cutting deeper on the lower end when the play in the push plate on the press walked one way. I think the idea with the rod is a good one for that problem letting the push plate walk without rocking the broach.

  7. #27
    TheOldHokie is offline Aluminum
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    Thanks all for the helpful thoughts. I compared the profiles of the broach to one of the Dumonts and they looked identical. Out of curiosity I made up a test piece with a slightly larger bore and ran a Dumont 3/16 C broach through it. Same problem so it seems it's not the quality of the tooling. That's good as I'm a firm believer in that old maxim "it's a poor craftsman that blames his tools" I'm beginning to suspect Brian's observation about 12L14 may be close to the mark. If I find the time I'll try a test piece made from a different material.

    FWIW I also happened to note that the "cheap Chinese import" was actually made in Poland although that probably doesn't sit any better with the tool police. And since this is a favor for an acquaintence who doesn't mind taking a hub with a second botched keyway in the bore no material was wasted - just the time to cut the second keyway.

    Thanks again for all the helpful tips - I'll especially keep in mind the advice about quill shaping on the mill - I suspect that's going to come in handy in the not too distant future. That's what I like about this hobby - so many different and clever ways to skin the same cat.

    TOH

  8. #28
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    bluchip is offline Stainless
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    Ill tell you what to try and usually it works.Lay a dowel pin on top of the broach so it lays perpendicular to the cutting teeth.This will allow the broach to straighten itself up and not kick as its pulled in.Try it. Jim
    Jim, I like that idea. Thanks.

  9. #29
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    the "cheap Chinese import" was actually made in Poland
    Geez, now I've sinned twice. My ENCO mill uses an ER-40 collet set made by Bison in Poland Talk about ethnic diversity, South Bend, Enco, Bison, Iscar, etc., my shop should certainly qualify for a Government Funded Grant

    although that probably doesn't sit any better with the tool police
    As long as Gary & Leigh are the hallway monitors, we can all sleep soundly.


    ----------------------
    Barry Milton

  10. #30
    mark costello is offline Hot Rolled
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    I have been told about another trick that I have not had a chance to try out yet........Place part and broach with teeth facing left or right and problem is SUPPOSED to dissapear magically. Will get to try when arbor press is found. Anyone have one to sell?

  11. #31
    dkmc is offline Diamond
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    Had similar problems from time to time with my DUMONT broaches. Mostly due to the bore being
    quite a bit longer than the bushing. Sometimes with
    the small broaches they do tend to cock back and hog in. And I have a couple import broaches that seem to work JUST FINE and similar to the ones in the USA DUMONT set in shorter bores.

    dk

  12. #32
    boozer is offline Aluminum
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    Ive seen the same problems, and have only USA DUMONT broaches, and was alway's courious as to what i was doing wrong, It seemed to help quite a bit, if i released the arbor from the broach on every stroke, but not always, Im going to try the Dowel trick, to se what that does,
    Also i found the when im boring and broaching sprockets, they seem to do alot better, but when working with parts made from Cold rolled, it seems to taper more often. it might have something to do with the softer metal, allowing the broach to dig in, Id hate to try it on my Broaches, but maybe dulling the cutting edge a bit might help, I alway dull the edge of a drill bit when boring brass so it doesn't grab.

  13. #33
    DieselBoot is offline Aluminum
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    I've never bought a broach . . . don't do nearly enough keyways to justify it. But I've broached a few keyways on the lathe by chucking the gear or pulley and using the carriage wheel to force an appropriately ground HSS tool through the 3 o'clock position. Use the cross slide to advance the tool 10 thou or so per pass. Works in a pinch.

  14. #34
    Forrest Addy is offline Diamond
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    I've made long bushings for parts that don't want to broach straight. They're easy to make.

    For what it's worth, there's no cure for the import stuff Nazis. They seem to utterly deny the nearly complete absense of US built machine tools that are either affordable or sized or in usable condition to the home shop user. They also have a black and white mind set. Import = bad; Domestic = good. Two legs = bad; four legs = good.

    Tune them out. I do.

  15. #35
    maus is offline Junior Member
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    first make bung that fits the part correctly. next move to a large arbor press. when you push the broach stop every so often and bounce the ram on the broach. not real hard, just enough to help re-center the broach. do this every couple of inches,and the broach should cut within a thou. or so. american,chinnese,or polish as long as the cutting tool is hard enough for the matl. it don't really matter

  16. #36
    maus is offline Junior Member
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    first make bung that fits the part correctly. next move to a large arbor press. when you push the broach stop every so often and bounce the ram on the broach. not real hard, just enough to help re-center the broach. do this every couple of inches,and the broach should cut within a thou. or so. american,chinnese,or polish as long as the cutting tool is hard enough for the matl. it don't really matter

  17. #37
    sandman2234 is offline Titanium
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    I think our tooling problems here in the States are much further advanced than what one broach is going to do to correct it. When a Ford Mustang is considered an import due to it's lack of USA Parts, and more of a Toyota is made here than a Tahoe, we have much bigger problems than an import broach is causing.
    Glad you got your keyway done and that it didn't mess up too many parts during your learning curve. Glad you broach experts were able to help. I enjoyed the reading.
    David from jax

  18. #38
    Perk is offline Cast Iron
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    Sounds like the problem could be any one or combination of the things covered here. In our shop we use “Pull Broaches” on vertical broach machines, never seen the type of problem you’re describing using this method. I realize this type of setup would be hard to justify for the average shop.

  19. #39
    pepo is offline Hot Rolled
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    Short part and coarse pitch on the broach equals blowout on the back side. Easy to cut materials like bronze and leaded steels are the worst. Ideally there is at least 3 teeth in contact with the part all the time. If you are using one of those hydraulic presses with a bottle jack and a plate suspended with some extension springs it gets worse. An arbor press is best. This is because the cutting action of the broach makes it want to "lay down" on its back with the teeth facing up,think about it. Any "slop" in the press plate front to back or right to left lets it get crooked. Supporting the broach on its back, opposite the teeth,and ABOVE the part will make a big difference. It seems simple but there is a lot of things happening at once.

  20. #40
    Greeno is offline Cast Iron
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    Cathead:
    support the plug high in the bore rather than it sitting on the face of the hub
    Pepo:

    Supporting the broach on its back, opposite the teeth,and ABOVE the part will make a big difference.
    From my experience with the same problem, using Dumont - an import for me - these guys are steering you the right way. Stick a bit of 3/4 square or some such under the lip of the bushing opposite the broach.

    It's a bit of a bugger when broaching is the last op in a complicated part.

    regards, Jim

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