Sherline First time Student/Beginner Hobbest Question

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rob_martinez03
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Sherline First time Student/Beginner Hobbest Question

Post by rob_martinez03 » Mon May 03, 2021 8:10 pm

Hoping you folks can help me determine what I am likely doing wrong... More than one thing I assume. I am consistently getting bad results when reducing a single rod of steel (unknown type of steel bought at Lowes). Seems like after trying to reduce a 4 to 8 in piece of stock from .25" to .242" (goal) it gets a little bowed in the middle and my reductions are not very consistent. I don't get much chatter but I still get lots of ridges in the finished piece - even when I make a last .01-.03mm cut (I say 1-3 since sometimes 1 wont cut anything and it takes .03 to get any chips)...

I first assumed I wassn't concentric but now that I take my time on the 4 jaw chuck I get it down to 4-8 tick marks on my dial indicator. I am using a steady rest and tail stock but I think I am still getting shake which I believe is causing a big part of my problem. Another symptom (of shake I think) is that after cutting from right to left, on the way back (left to right) it appears to still cut initially (close to chuck) and then intermittently back to the end of the part.

Sherline has a part called a 'Follow Rest' which rides on the cross slide with the cutting tool. Does anyone have any experience with that part? All 3 (steady Rest, Tail Stock and Follow Rest) might be overkill but if it eliminates part of my issue I am open to it. Any other suggestions on what this first time hobbyist is doing wrong?

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Bill Shields
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Re: Sherline First time Student/Beginner Hobbest Question

Post by Bill Shields » Mon May 03, 2021 8:29 pm

It is most likely Cold rolled steel which is difficult to get to a good finish.

Perhaps the easiest path to a good job is different material...

Add to that fact that a piece that diameter and length will require a tail and follower rest to keep it rigid enough to allow a good cut.
Too many things going on to bother listing them.

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GlennW
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Re: Sherline First time Student/Beginner Hobbest Question

Post by GlennW » Mon May 03, 2021 8:34 pm

It may also be beneficial to post an image of the tool bit you are using so that we can see how it is configured.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!

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rob_martinez03
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Re: Sherline First time Student/Beginner Hobbest Question

Post by rob_martinez03 » Wed May 05, 2021 10:11 am

Thanks for the suggestion -- here are some pictures. I took a number of pictures of my tool. I believe it is a right handed HSS tool. A terrible question to need to as but Do I have it in sideways or upside down? Is my Steady Rest in the right spot. Sometime I put it by the tailstock and other times by the chuck. With a RH tool we should only cut from Right to left correct? As you can see the marks on my rods are intense. I don't recall if I used a tail stock and steady rest for all but I do recall it didn't make any noticeable difference. My latest experiment is cutting from the center and its a lot Lot better. However, I am still not really able to consistently cut off the amount I want to.... and it will still intermittently cut when I finish my right to left cut and am returning (left to right).... I kept thinking it was a lack of consentricity but now I think its a combination of things... maybe I need to put my tool at an angle instead of straight on? Any suggestions on how to minimize the ridges on my rod and to get consistent cuts would be greatly appreciated. Again - is my tool and steady rest even installed correctly?

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NP317
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Re: Sherline First time Student/Beginner Hobbest Question

Post by NP317 » Wed May 05, 2021 10:32 am

First you need to use a Follower Rest, not the steady rest. Then there is support directly opposite the tool as it cuts.
Also it appears your feed rate is too high for the sharp corner on the cutting edge of the tool. You are cutting threads...
So: Slow down the feed rate and round the cutting edge more, and SHARPEN the tool! Use a diamond hone to make it razor sharp. Then use lubricant too.

You are indeed trying to perform a very difficult machining operation: long diameter reduction of an already small and flexible rod.
Any flex anywhere pretty much makes it unlikely to achieve success.
Key goals: Rigid setup and Sharp cutting edge, and patience.
RussN

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rmac
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Re: Sherline First time Student/Beginner Hobbest Question

Post by rmac » Wed May 05, 2021 12:16 pm

Here are a few more hints in addition to what RussN said:

1. I noticed in your original post that you want to reduce your rod from 0.250" to 0.242". That's a diameter difference of 0.008", which means you're only taking 0.004" off the radius. But (!) you say that you're seeing "4-8 tick marks" on your dial indicator when you try to get the part centered in your 4-jaw chuck.

If your dial indicator reads in .001" increments (which is likely), then the part is not concentric by more than you're trying to remove. That would mean the tool would be cutting on one side of the part and not cutting on the other. That alone could give you all kinds of trouble on your small-diameter rod. So I'd say you need to get the part centered better. Shoot for 0 ticks!

2. It's very important to have the tool height set exactly. If the tool is too high, then it will just rub and not cut. If it's too low, it will dig in and your thin rod will flex and try (probably successfully) to climb over the top of the tool.

3. As RussN said, what you're trying to do is difficult and there are a lot of factors involved. It might be a good idea to take a baby step approach and try to make sure your tool is cutting properly before you deal with the additional difficulty introduced by the thin, flexible rod. As a first step, experiment with just a short length of the rod (say 1/2" to 3/4") sticking out of the chuck. (There's a rule of thumb that says you can turn something up to about three times its diameter without additional support.) Then when you get good results, go ahead and try to work on the longer piece.

In any case, with 1/4" material 4-8" long, I agree with RussN and Bill that you need a follower rest.

-- Russell Mac

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Re: Sherline First time Student/Beginner Hobbest Question

Post by John Evans » Wed May 05, 2021 1:07 pm

Have you centered drilled the end of your material? Picture looks like you just have the center touching the end of the material. that is a No no. I have found the material bought from the big box stores to be absolutely horrid to work with . Your tool looks like it could use more top and side rake. Tool is HSS ? Don't attempt to use carbide on that little very light duty lathe,waste of time and money. Look at the tool grind pictures in the South Bend how to run a lathe book. It is online in PDF. Your tool spot on center? If your dial indicator is .001 div. your variation should be less than 1 division!. .008 stock reduction with that material ,diameter,machine and length I would seriously consider using a file and emery cloth . On small light flexible machines very sharp positive rake HSS is you friend.
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rmac
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Re: Sherline First time Student/Beginner Hobbest Question

Post by rmac » Wed May 05, 2021 1:53 pm

John Evans wrote:
Wed May 05, 2021 1:07 pm
Have you centered drilled the end of your material? Picture looks like you just have the center touching the end of the material.
Good catch! I sure didn't notice that.

-- Russell Mac

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Re: Sherline First time Student/Beginner Hobbest Question

Post by Mr Ron » Wed May 05, 2021 2:30 pm

It looks to me the tool bit has not been ground. It looks like the way it comes new.
Mr.Ron from South Mississippi

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rob_martinez03
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Re: Sherline First time Student/Beginner Hobbest Question

Post by rob_martinez03 » Wed May 05, 2021 8:58 pm

Thanks for the suggestions -- all good ideas. The Follower Rest is now on order. The best part of buying a Sherline (so far) is the ease at finding/getting extra stuff. I will also try the other suggestions of slowing down and more/better centering. Not sure I am up to sharpening my tool yet but when I feel confident enough to try it, that will be in the mix as well. Showing my ignorance here but I am not sure I understand what "If your dial indicator is .001 div. your variation should be less than 1 division!." means.... Wouldn't less than 1 division be seeking perfection? Is that even possible?

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Bill Shields
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Re: Sherline First time Student/Beginner Hobbest Question

Post by Bill Shields » Wed May 05, 2021 9:17 pm

Get used to it if you want good results

However..be aware that if your starting stock is not truly round....and rod from Lowes may very well not be round...you will have to make do with what you have to work with.

Get it as close as you can as a best practice..which includes drilling the end for the center...using a center drill.

Note that a follower rest that is pushing against something that is not round to begin with brings another set of variables into the process.
Too many things going on to bother listing them.

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Re: Sherline First time Student/Beginner Hobbest Question

Post by John Evans » Wed May 05, 2021 9:35 pm

When I use or have the need for the accuracy that a 4 jaw chuck can provide I normally try to keep the difference in readings to less that 1/2 of ONE division. And if need be less than that. We are not playing horseshoes or hand grenades here,accuracy is the name of the game in machining.
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