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Thread: Machinist's / hobby machinist's

  1. #16
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    Carbide easier to chip if material nasty or you are a bit rough but in general it can cut at 3x the speed of hss.
    Hss better for mild steel at least as far as final finish goes. The softer materials like that. Better for nylon too and if you cat aluminium use a bit of crack or kero and has does well.
    Dont believe it's better than carbide on brass. It's all about the rake.
    Dont be frightened of aliexpress tool holders but if you are that worried put good tips in there.

  2. #17
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    My machine doesn't really have the hp to do deep cuts, it's just a light machine, not sure my skill level is going to be any where near building a 4 jaw, maybe one day, I was thinking a back plate was a stretch. So far only done stuff with simple dimensions and no real threading.

  3. #18
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    I searched the country for 6-7 months before I found something decent with a cast bed to replace my small lathe.
    Attached Images Attached Images  
    homebrew.357 likes this.

  4. #19
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    Still,I would never go back to using just HSS for most of my uses,the factory made carbide cutters are so good, and keep their edge for so long they are well worth the modest cost of them and the extra productivity they allow.

  5. #20
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    Quote Originally Posted by Markgibsonr25 View Post
    I searched the country for 6-7 months before I found something decent with a cast bed to replace my small lathe.
    I could probably get that thing between centers and turn it to chips.... [/LIST]
    bully likes this.

  6. #21
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    Quote Originally Posted by Markgibsonr25 View Post
    I searched the country for 6-7 months before I found something decent with a cast bed to replace my small lathe.
    That is a great looking machine, I hope to one day get to some thing like that, I'm quite happy with my small bench top machine for now, it can scare me enough.

  7. #22
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    Always someone with a bigger one at the trough!!!!
    Quote Originally Posted by mimms2 View Post
    I could probably get that thing between centers and turn it to chips.... [/LIST]
    rusl likes this.

  8. #23
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    Did a little bit of machine work on a lathe with a nearly 6ft faceplate/4jaw. It had a recess in the floor so could swing almost 4ish meters? Probably 5 or more? Cant remember
    Almost...almost put a pc1000 (100 ton) excavator spider frame in it to face the slew ring mount surface but the corner of the office that was put in a few years before stopped it

  9. #24
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    That Global is a very useful workshop machine. I had something similar for many years and it gave excellent service, then about 15 years ago Scott Machinery phoned to say they had traded in 5 or 6 late model Colchester Students with all accessories (ex a technical college), 1 metre BC and at a sharp price. They sold the lot over the phone before they even took delivery. I picked up a good capstan attachment a few years later and bought a new collet chuck. It is a fabulously accurate machine and cuts a large range of metric and imperial threads.

  10. #25
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    Quote Originally Posted by gundoc View Post
    Yep, there is nothing than can't be done by HSS, especially by grinding the tool rake to suit the material. TC has only been commonly available since the 1960's. For the 100 years prior to that it was all done with HSS (including the engineering output of two World wars). I don't think you can find much fault with the quality of engineering up to and including WW2.
    I am in grateful for the world wars, and all the others too.

    Without these totally shitty times in our history, we would not have the variety of firearms that we do today.
    So, thank you to all the assholes who in one way or another are responsible for the worst times in recent human history so far.

    Long live the gun, especially the old, banged up military gun.
    Use enough gun

  11. #26
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    Quote Originally Posted by gundoc View Post
    That Global is a very useful workshop machine. I had something similar for many years and it gave excellent service, then about 15 years ago Scott Machinery phoned to say they had traded in 5 or 6 late model Colchester Students with all accessories (ex a technical college), 1 metre BC and at a sharp price. They sold the lot over the phone before they even took delivery. I picked up a good capstan attachment a few years later and bought a new collet chuck. It is a fabulously accurate machine and cuts a large range of metric and imperial threads.
    I did look at a few old colchesters and missed out on quite a beat up one at auction that went for moon beams of cash,This global will see me out.It is plenty accurate for what I want and the occasional bit of gunsmith stuff for myself.

  12. #27
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    Quote Originally Posted by mimms2 View Post
    Backplate doesn't need to be cast. Indeed, machine it.
    Backplate will serve a lot better if it is cast. Less chance of seizing onto the spindle nose, and less likely to change accuracy at differing temps. I machined one up for my lathe out of steel, ended up ditching it for a pro-machined cast iron one. Was cheaper to get a chunk of cast SG rod into a machinist and give them a threaded slave the same spec as the spindle nose and go from there. The chuck ran better on the cast backplate, and didn't 'ring' as much (or sing if that's a better description).

    If I recall correctly (haha), the 9x20 uses a Boxford-spec spindle nose (got one in for the old man's hobby lathe that way). If you look at the Boxford spindle nose specs and compare to your machine unless the chinese did something weird that day it should line up. *May* also match up to the Myford Super series machines off memory, can't confirm that without looking haven't played with one of those for a decade. You can buy those backplates directly from overseas as a 'blank' - a threaded back plate, fit to your machine and turn down the register to spec (touching fit, cool the backplate so that it drops in...) and then drill through the center of a correct sized bolt, screw it into the chuck and drill out the location hole, drill to clearance size carefully from the other side using a depth stop and have at. If the chuck is the bolt head side, i.e. clearance holes no thread, turn up a guide and same procedure but opposite.

  13. #28
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    Quote Originally Posted by Mauser308 View Post
    Backplate will serve a lot better if it is cast. Less chance of seizing onto the spindle nose, and less likely to change accuracy at differing temps. I machined one up for my lathe out of steel, ended up ditching it for a pro-machined cast iron one. Was cheaper to get a chunk of cast SG rod into a machinist and give them a threaded slave the same spec as the spindle nose and go from there. The chuck ran better on the cast backplate, and didn't 'ring' as much (or sing if that's a better description).
    Of the 15 things I have that go on any of 5 lathe spindles, the only cast ones are the face plates. I also change chucks on any given machine often enough that seizing isn't really a consideration.

    Most of my machines are old, heavy, and belt drive, so might be different for new/ geared head. Honestly couldn't tell you what material the spindles/backplates are and can't say I've noticed any deterioration in accuracy. I'd think more would come from cold bearings or worn tooling, than thermal expansion of a backplate

  14. #29
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    In fact I would think CI would be less desirable at high speed/ modern machine, with a tendency to rapidly disintegrate with any shock-load...

  15. #30
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    Quote Originally Posted by mimms2 View Post
    In fact I would think CI would be less desirable at high speed/ modern machine, with a tendency to rapidly disintegrate with any shock-load...
    Dunno what you are shock loading on a lathe??? SG rod machined to size is what most of the factory Pratt and Beurnard engine chucks are made of I think - must be serviceable given the thousands of those made?

    The issue I noted was related to the chucking up of stock, I have a test bar ground to .0001" across it's length and out from the chuck mounted on the steel backplate measured over several days the end of the bar would be more or less running out of true depending on the whims of the lathe gods. Up to 10 thou variation which was weird. The CI backplate runs to the accuracy of the dial gauge. Plus, can get a better machined finish with the CI backplate fitted, same chuck. I have a beater chuck fitted to that steel backplate now and use it for any rough work like badly rusted shafts or the like.

 

 

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