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19th Jun 2021, 08:43 AM #61Member: Blue and white apron brigade
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In most cases I reckon sanding above about 400 is a waste of money.
If you want a shiny surface it's probably better to jump from 400 to a buffing wheel.
But just like fine abrasive paper a buff won't remove scratches.
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19th Jun 2021, 06:30 PM #62Most Valued Member
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Chris
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19th Jun 2021, 06:55 PM #63
Finish
Hi
I think you would achieve a better finish if you use a tool with a small radius on the point , your tool appears to have a sharp point on it which isn't the recommended shape for a decent surface finish.
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19th Jun 2021, 07:28 PM #64
Hi Mathu,
Those two pictures don't even look as though they have been turned on the same machine !
I don't think even sanding or filing would produce such a rough finish. Something else is going on here !
That finish looks like the lathe tool has been run back and forth on the work, and the lathe saddle is not set up properly so its able to rock as its moved. Check the saddle gibs for play. You will find that the saddle will get tighter as you get closer to the tailstock. The difference will be due to the wear in the shears near the chuck end.Best Regards:
Baron J.
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19th Jun 2021, 08:31 PM #65Member
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19th Jun 2021, 08:33 PM #66Member
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19th Jun 2021, 08:38 PM #67Most Valued Member
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It is just a plate mounted at the rear of the saddle, there will be 2 set screws , screwed up from underneath to secure it .
If you grab the back/rear of the saddle you should be able to lift it until the (gib) keeper plate hits the underside of the bed.
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19th Jun 2021, 08:53 PM #68Member
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19th Jun 2021, 09:02 PM #69Most Valued Member
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Don't know about tightening it up to much, normally there could be upwards of .060" or more clearance.
If you feel it needs to be closer you will need to shim it, you will also need to check the the carriage does not bind along it's travel.
Are you power feeding or still feeding manually?
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20th Jun 2021, 11:57 AM #70Most Valued Member
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20th Jun 2021, 06:21 PM #71
Hi Mathu,
I've not been able to find any drawings of your lathe parts to be able to identify the gibs or the adjustment screws for it.
On my lathe the gib and the adjusting screws are on the front of the saddle just below the crosslide feed handle. And are adjusted to prevent the saddle twisting as it is traversed along the bed. There are anti lift plates at the back where on the Myford the saddle lock is fitted.
It might be a good Idea to get a copy of the Southbend book "How to run a lathe" its well worth having !
Edited to add this picture from the South Bend lathe manual !
Saddle Gib Screws.pngBest Regards:
Baron J.
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21st Jun 2021, 04:08 AM #72Member
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this is the underside of the carriage rear ( towards the wall ) I tightened this us and yeah, the carriage is a lot more firmly pressed against the bed/ways and take a fair amount more 'oompf' to move from side to side, and yes it's a bit more easier to move the closer you move towards the chuck.
195881738_415522666138137_6428517296112283035_n.jpg
This is a fresh piece i am working on.
just turned it down to the diameter/thickness i needed and this is the outcome.
199709787_783970738918964_3821105638462825376_n.jpg202238660_316644016801502_8799718782319088832_n.jpg
same tool as before
198646887_267051945217739_8039311089065180746_n.jpg
hmm, that seems odd to me, but yet also makes sense at the same time. i do see the chatter on the left side shoulder that the left face of the tool comes up to. i only cut about 0.5mm at any pass and the chatter i expected when i got to the face as its about 10mm contact area instead of 0.5mm and is too much for the machine, but i wanted to get it cut all the way to the corner so i turned the machine off and reset my tool the moment the chatter began at the end of each pass ( i hope that makes sense )
maybe i just need to go and get a carbide bit holder and inserts.
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21st Jun 2021, 05:37 PM #73
Hi Mathu,
If you haven't got a copy of the book I mentioned, drop me a PM with your Email and I'll send you a copy !Best Regards:
Baron J.
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22nd Jun 2021, 12:05 AM #74Most Valued Member
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If that’s a piece of hot rolled, that finish is about as good as it gets.
You may get a little better using a tool with a radius at the nose, but hot rolled is hot rolled, you will never get an Instagram machinist picture from it.
Picture attached is hot rolled mild steel cut with a DCMT carbide tool on my 9”. The insert has a .4mm radius on it, the finish is only marginally more consistent than what you achieving, that will be largely due to the power feed on both axis.
To cut shoulders like that, work along to the left, withdraw the tool along the shoulder in a facing type cut, return to the start, touch off (dials should match where they were last cut) and go again (if you can keep track of the dials in your head then you can skip the touching off and advance the tool). If it’s a precision part either set a stop or an indicator to establish the shoulder in the same place each cut.
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22nd Jun 2021, 09:24 AM #75Member
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Thank you
left one is hot rolled which i got before i knew what to get, right one is machining steel i got from a local machine shop ( i asked for 12L14 )
194238914_549239736458989_2857886596862305643_n(1).jpg
i've been just measuring with tape on the piece itself as what i've been making aren't needing precision and also i can't really do the whole imperial system and the dials on the lathe are imperial.
oh and the latest piece i've been working with is hot rolled, the thicker section is as it's finished by the initial tool(right side ) , the thinner section has been polished up to 2000 grit sand paper. ( left side ) Sadly i got a bit of chatter on a spot half way down the thinner section which you can feel :'( but alas, it's just a home made piece.
196315197_314527870144647_5313800958601720643_n.jpg
I watched this video ( and more of the series she has and found it helpful )
https://www.youtube.com/watch?v=yBVo8wufsCE
I'll post back when i get a pice of 12L14 done and see what it looks like but for now, i'm still getting those weird semi random scratches in all parts.
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