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New Project. Chuck Back Plate.

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by Hukshawn, Dec 20, 2016.

  1. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    So, I bought a 6" 4 jaw chuck. Quite happy with that. Issue... the store does not supply a back plate. Even a blank back plate. Crazy... and my other avenues in which I purchase equipment only have a 5"... looks like I'm making my own.
    Fun situation... I have a 5" 3 jaw chuck and zero way to grab my stock. I bought a 7"x7"X1" slice of hot rolled plate steel. I did some reading just now and they say cast is better.... but, this is what I have. I asked the guy at the metal supply his opinion and this is what he came up with. And they are a full out machining shop.

    So here's my plan, please critique it.

    I have a 1" thick piece. My lathe spindle is 1 1/2" 8tpi. The shoulder to the tip is just less than 1". So I think I'm fine on thickness. Would be happier thicker, but again, I'm using what was avialable and affordable.
    I am going to centre drill on the drill press to the largest hole I am capable of, (which I believe is 3/4"). Make a jig to mount this between centers on the lathe and carefully hog out about 1/2" and form a rough collar where the threads will be. Just taking enough material off to allow me to then grab that collar with the chuck jaws. Then bore out the spindle hole and thread it. Mount it on the spindle and from there basically machine the final profile of the back plate to my satisfaction... i feel doing the final machining with the plate mounted on the spindle gives me the best hope of being true with a minimal runout.
    in my relatively inexperienced mind, (aside from the safety issues of slinging this chunk of steel across the garage...) i think this works...

    Thoughts!?

    I'll deal with the fact that the mounting bolt holes are not thru holes so I can't use a drill hole punch, later. I have to measure and scribe and hope for the best or make the holes big enough to... essentially... throw the hot dog down the hallway... and do the final truing with the chuck mounted with a dial gauge and tighten once satisfied.
     
  2. MozamPete

    MozamPete South Africa Active User H-M Supporter-Premium

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    I have a similar plan but I think I will be able to hold my blank in my 4 jaw (which is larger than my existing 3 jaw) to bore and thread it, but then would mount it on the spindle to do the majority of the machining similar to your plan.
    So I say go for it and let me know if it works . But seriously I would also so be interested in the the professionals opionon of this approach and any pitfalls to watch out for.
     
  3. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    That is precisely why I bought the larger 4 jaw. I plan on building a milling jig. So need the 4 jaw to hold erregilar stock. Also bought the angle plate today. The Christmas break should be fun. Several good projects... pending my wife gives me the time...
     
  4. 682bear

    682bear United States Active Member Active Member

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    I'd say you have a good plan... I just machined one for a 9 inch chuck this morning on my old South Bend.

    I did the final machining with the plate mounted on the spindle also.

    -Bear
     
  5. Joncooey

    Joncooey Canada Active Member Active Member

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    When I did mine, I bored out a piece of round stock for the threads (Boss) and then counter-sunk it into the plate and welded it. Allowed for more threads in the round bar stock; say 2 inches. Make sure everything is as true as you can get it when you weld and then true up the rest on the lathe.
     
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  6. brino

    brino Active User H-M Supporter-Premium

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    Agreed!

    One small issue is how square with the plate your first drilled hole is. Once you put it on an arbor or mandrel I think you will notice some "wobble" of the face of the plate. However, when you complete the (possibly interrupted) facing cut, you can find the new square plate within. Just be aware that you lose some thickness.

    Once bored and threaded you can mount it on the spindle and take a final facing cut to make the big face square.
    One key is to get the shoulder that registers against the lathe spindle to be square to the threaded bore.

    It can be tough finding an appropriate lathe speed for facing. You're really aiming for a particular sfpm (surface feet per minute) based on the cutter and material.
    However since the diameter changes so drastically from the centre to the outside rim of the plate the sfpm changes too.

    -brino
     
  7. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Yeah exactly, I wasn't going to rely on turning between centers to get me anywhere near true it was merely to get enough material off to allow the Chuck Jaws to grab the collar. That would allow me to thread it and then I can mount it on the spindle and do all the final truing.
    I should be able to face both the front and back this way, just take the back plate off and spin it around and screw back on, and face that side.

    Do you think hot rolled was a good choice?
     
  8. f350ca

    f350ca Canada Active User Active Member

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    Im not an expert on threaded spindles, guess the one on my indexing head has one though. You said you measured the thread as just under 1 inch, but you need to machine a tapered recess for the shoulder just behind the thread on the spindle. The chuck centres on that shoulder, the thread only holds it there. Im thinking your plate isn't thick enough for the full thread and shoulder.
    I'd try using you're three jaw as a face plate. Remove the jaws and grind bolt heads to fit into the slots, same idea as t-slots. Then drill 3 holes in your blank to bolt it on. Drill, bore, thread and cut the bore for the shoulder with it there. You can face it from the new bolt circle to the centre and clean up the rest after its mounted on the spindle. With the bore done mount it on the spindle and do your machining for the chuck mount.

    Greg
     
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  9. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I did account foe the shoulder. From the shoulder to the end of the spindle is just less than 1". Even still, there is room beyond the back plate inside the chuck if the thread sticks out a bit. Shouldn't cause any issues, you're right, as long as the shoulders seat fully to align.

    I do like the mounting to the 3 jaw chuck idea tho, at least to bore and thread. Best case scenario to get a good straight thread. Straighter than trying to turn between centers then trying to grab the collar with the chucks. And since I don't have parallels, seating true would be tricky.
     
  10. f350ca

    f350ca Canada Active User Active Member

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    I use HSS tool blanks for small parallels all the time. You have to check the Chinese ones for size, they vary.

    Greg
     
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  11. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Ya I've done that before. Didn't think of it this time...
    Actually, I'm getting 4 nice, brand new 3/8 hss blank tool bits. Was planning on making a nice set of lathe tools for the qctp
     
  12. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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  13. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Okay... here we go...
    I hogged off the corners to save time and work.
    I drilled the center hole, drilled and tapped holes and mounted the plate on my 5" 3 jaw back plate.
    Faced it and started rounding it out... slow process... the material is hard. I have a cobalt 3/8" tool bit and I burnt it out. Changed to a carbide and so far so good.

    What is the best tooling to use on hot rolled?

    ...when I put my band saw away... the shelf in the cabinet fell down..... I swiftly solved that problem by quickly and firmly closing the door!
     

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  14. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    What kind of speeds should I be focusing on with hot rolled? Faster or slower?
     
  15. 682bear

    682bear United States Active Member Active Member

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    You should be turning fairly slowly with that interrupted cut... once it cleans up, you can probably bump the speed up a little. The interrupted cut combined with too much speed can be rough on any kind of tooling.
     
  16. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I'm not home now, but I think it's about 700 rpm. That second pulley on front gears seems to be my go to speed.
     
  17. f350ca

    f350ca Canada Active User Active Member

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    Under 200 rpm would be more in line for HSS, till it got round I'd be at about 100. Carbide will want faster, but not till you get it round.
    I prefer HSS for cold roll, if its harder then switch to carbide.

    Greg
     
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  18. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I'm at 700ish rpm using a big 1/2" carbide bit and it seems to be handling it reasonably well. If I try to cut too deep it stalls the lathe. So, it's a long slow laborious process that's making one hell of a mess... I'm considering rigging up my shop vac and just sucking the chips off as they cut... but that'll probably start a fire inside the vacuum. Lol
     
  19. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Sweet Jesus... this is the slowest process in the world...
    I have the overall diameter turned down and now I'm facing off the material to form the collar that butts into the spindle face. I'm planing on taking off about .500". Turning at about 125 rpm with a 1/2" carbide bit. The max it'll let me take off in a pass is about .030". Slooooowwwwww.....
     
  20. Fortis64

    Fortis64 United Kingdom Iron Registered Member

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    Patience Patience ...... I turned down a 8" od 1 1/2" thick plate that was about 3/4 " out of round after it had been cut with a torch . And i also just finished making a back plate for my 6" 4 jaw out of cast iron messy job lol. Once you've knocked the high points off speed up the lathe and use carbide tool with a new cutter make a world of difference . Threading and getting the register right will be the challenge for you . I actually made a dummy tread and register on a bit of stock so i could test fit as i was going along . Threads are important but you can get away with being a tad lose on the thread but it's the register that's the important bit to get spot on.

    Good luck

    Sean
     
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  21. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Progress.

    Boring out the center hole.

    My lovely wife bought me a new CCMT boring bar for Christmas (my request, how the hell would she know otherwise?) Stupid me, wrote 3/8" on the list instead of 5/8". Oops... maybe I'll use it for smaller holes if I ever need to.
     

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  22. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I'd call this a flaming success so far....
     

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  23. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    I got told to come inside... I guess 1am IS pretty late......
     

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  24. Fortis64

    Fortis64 United Kingdom Iron Registered Member

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    Doing this in steel would've been a toughy .... good job :)... Funnily enough I gave my wife a couple of side notes too nothing ever came of it ..... :congratulate:
     
  25. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    This is hot rolled steel.
     
  26. 12bolts

    12bolts Global Moderator Staff Member Active Member

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    Just depends on your perspective.
    In 6 months time it wil stil be daylight then wont it?

    Cheers Phil
     
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  27. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Okay ladies.
    I'm done machining the back plate. Really nice fit into the back of the chuck.
    Next step is to drill the bolt holes. However, the bolt holes in the chuck are not through holes so I cannot use a center drill hole punch. What's a good method to scribe out those blind holes into the back plate?
     

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    Last edited: Dec 28, 2016
  28. brino

    brino Active User H-M Supporter-Premium

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  29. Hukshawn

    Hukshawn Canada H-M Supporter - Premium Content H-M Supporter-Premium

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    Oh great idea! I have a bunch of those for wood. I can make up a few for this. Right on.
     
  30. brino

    brino Active User H-M Supporter-Premium

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    I was trying to find some references either on this site or a tool catalog to a similar product, but could not.
    They are basically a piece of threaded rod, but with a centre point on one end and a allen-key hex hole on the other end.
    (that allen drive won't help with your blind holes though)
    They are used exactly like the dowel centres, but would actually thread into the chuck holes, and be a little adjustable by changing the insertion depth.
    -brino
     

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