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quick change posts, etc.
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Geoff Steckel
I bought the Harbor Freight lathe and the advertised quick change
toolpost some months ago. The only way I've been able to use any tool bigger than 1/4 inch is with the quick change unit, and only then by lowering the tool holder well below the level of the cross slide. It works, but it's not pretty. After spending about 10 hours tightening every gib in sight, polishing the ways, and other miscellaneous fixups, I am now trying to replace the spindle bearings in hopes of getting less play and flexing. The Harbor Freight model had straight roller bearings, so I'm replacing them with angled bearings to take thrust loads. The stock bearings had about .8 mil static runout. The dynamic runout was bad (> 5 mil, AFAIK) at speed. We'll see if this improves it. |
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Michael Wood, Cincinnati
Can you give us the play by play on this modification? I'd like to know how it turns out. Mike Wood
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Geoff Steckel wrote: I bought the Harbor Freight lathe and the advertised quick change |
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The "standard" fix is to machine most of the "step" off the top of
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the compound & some off the bottom. JWE has posted details, IIRC, in the 7x10 files. Are you sure about the bearings? The HF I've got uses 6206ZZ bearings; 62 mm OD, 30 mm ID, deep groove ball bearing, double shields. Bearing preload/end play is adjustable with the 2 nuts on the geared end of the HS. Loosen the outer nut, adjust play with the inner nut, tighten the outer (lock) nut against the inner nut. Repeat as necessary to allow for the outer nut moving the inner nut against its threads! Roy --- In 7x12minilathe@..., Geoff Steckel <gwes@o...> wrote:
I bought the Harbor Freight lathe and the advertised quick change |
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Here's a link to info on JWE's mod:
Frank Hoose --- roylowenthal <roylowenthal@...> wrote: The "standard" fix is to machine most of the __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software |
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John
Hi Geoff,
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The mod to the compound rest is very helpful when you use a QCTP. Since I don't have a mill I took advantage of the offering from LMS: ProductID=1777 This mod reduces the height and also moves the pivot point which aids in reducing chatter. Check the 7x10 group's messages for JWE's suggestions on toolpost positioning vs the compound location. My understanding of his comments is that the TP center bolt should be to the right of the compound's pivot; the mod's re-positioned compound pivot aids in achieving this (this mod idea was JWE's) while maintaining good engagement of the compound's dovetail. Ultimately, what you want is reduced overhang of the tool relative to the compound -- using a QCTP tends to increase overhang so you must then work around this. Its all about leverage - the farther the tool point extends from the carriage the greater the chance of chatter. One point with small lathes is that they are inherently not as rigid as larger lathes so you must try to accommodate this reduced rigidity in a number of ways, as you are doing. Another thing which may be helpful is to grind tool bits to sharper points rather than the rounded points suggested in many texts. The broader the point the greater the forces generated which cause flexing resulting in chatter. Sharp tools with good clearance angles reduce the force generated by cutting rather than tearing the metal. Having tried all the above I still get chatter sometimes, mostly when facing steel and taking a light cut... John In 7x12minilathe@..., Geoff Steckel <gwes@o...> wrote:I bought the Harbor Freight lathe and the advertised quick change |
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