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Long Square Stock

Running True

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woody121/05/2020 22:17:03
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91 forum posts
21 photos

Evening all, hope well and safe.

I have a bit of a problem, my stock is 32mm X 170mm 6082. I indicate near the chuck then move to the far end and tap with my wooden mallet to get running true. However when I return to the chuck I'm out again and visa versa. I know I'm doing something wrong. Could I have some advice please. Do I need to place the indicator in the same position laterally when I am moving from end to end?

Thank you,

Woody.

Ady121/05/2020 22:48:01
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4129 forum posts
576 photos

"Turning between centres" is one of the most difficult things you can do on a hobby lathe

Square stock makes it even more awkward

All I can say is for roughing down use a live centre but you MUST use a dead centre for those critical final accurate cuts

I sometimes use an extended dead centre at the chuck end, it projects just far enough forwards to push stock away from the chuck surface, then I secure the dead centre at the tailstock end, then with the stock locked between the two dead centres, I close the chuck jaws

GL

Hopper22/05/2020 01:22:47
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5040 forum posts
112 photos

Draw two diagonal lines across the square end and carefully centre punch or prick punch a small divot at the intersection. Place the tailsock centre in the punch mark while setting the other end true in the chuck. The far end may then require final adjustment with mallet but should only be a few thou so should not mess up the chuck end.

Are you wanting to turn the OD of the job or drill a hole up the middle? A round sleeve and fixed steady might be in order for the latter.

woody122/05/2020 09:09:51
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91 forum posts
21 photos

Thanks for the advice, yes I'm going to drill but need to do so from either end then bore to final size. I have my steady and suitable sleeve. I'm just waiting for bearings to arrive. Just mocking everything up and playing in the meantime to get the best set up.

Thanks,

Woody.

woody122/05/2020 19:49:38
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91 forum posts
21 photos

Thanks for the tips,

I got it Sussed . First attempt was a failure, second third and forth all improved and set up time is down to 20mins. I learned my mistake. I was clamping chuck end to firmly to soon. I found if I clamp the jaws loose about .002" move to the tail, tap to get within .002" and repeat the process slowly increasing clamping force I can get to almost zero both ends. I also found my punch mark was way to aggressive and the centre just kept springing the stock back.

So my method goes, mount stock with sleeve and steady in place, indicate either side of set up ( difficult with the limited space), put fingers of the steady in place and then remove tail stock/centre and a final indicate🙂.

Thanks once again for poking me in the right direction, I'm well happy, I thought something was drastically wrong.

Woody.

John Reese23/05/2020 01:41:20
864 forum posts

Tap the outboard end until it runs true. Center drill it. Set the center in the end of the bar, then go back anf true up the chuck end.

Option: center the outboard end with a steady rest before center drilling.

Are you sure your chuck is tight against the shoulder of the spindle? (Only if you have a threaded spindle.

John Reese23/05/2020 01:44:22
864 forum posts

Oops! I forgot you said square stock. A sleeve that fits the square corner to corner is needed if using a steady rest.

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