Bantam Finishing Problem.

[Alan .204Participant @alan-204]

Hi chaps I'm having a finish issue with the Bantam Lathe it doesn't seam to mater what different tools I use the problem is still the same, what I end up with are lines in the finish but they are not the same on any piece of steel what I'm trying to say is there is no pattern to the lines I've checked everything I can think of and all seams well. no lose gib's or motor but there is something lose that maybe I can't find, could there be something wrong in the apron a missing tooth on a gear perhaps but if it was that the line that's left on the steel would be in the same place I thought, I've been using mild steel and have tried all different speeds and feeds but it still does it, you could have the first 1/4 inch ok then all of a sudden you see a line appear then it be ok again a bit further on it will do it again, if these lines we the same distance apart it would tell me something but they are not there random, the lathe has always been like this since I bought it but now I seam to be getting a bit better at this hobby I would like to get to the bottom of this problem, hope someone can help.

Regards Alan.

[Alan .204Participant @alan-204]

[JasonBModerator @jasonb]

Random pattern would suggest the tool is cutting then being pushed away before cutting again. What type of tool are you using and does it do it on all tools or just the one.

Pic would help

[Alan .204Participant @alan-204]

Hi Jason I was hoping you might reply, I've used different HSS tool's of all different grinds from knife tools to finishing tools and also carbide tip tools factory and home made and they all do the same, have tried from 59rpm and 1thou feed rate up to 6thou feed 800rpm basically as many combinations as I can get, when I first bought the lathe and noticed this problem I had a friend of mine come and have a look at it and he could not understand it, he ground up some of my tool steel as well as brining some of his own he uses on his Southbend Lathe to great effect I've seen him working and the finish compared to mine is of a different standard with out trying to hard either, mine seams to either stop momentarily or bounce some how, I tightened up the gib strip on the carriage enough so it's now hard to turn the carriage wheel at the other end of the bed, the cross slide seams to be ok as does the top slide, I even made a new tool post bolt to take that out of the equation, no I'm a bit stuck and that's what lead me to thinking could it be something with the drive in the apron.

Al.

[JasonBModerator @jasonb]

Does it only do it when feeding under power? if its ok on hand feeding that would tend to eliminate the spindle and drive train.

Have you got a load of swarf packed into the half nuts on the feed?

[Alan .204Participant @alan-204]

Hi Jason it does it just the same by hand or power feed, have lost the book for the lath so not sure how to get into carriage to check the half nut, it drops in and out smoothly if that's any help, one thing I haven't done is to disconnect the change gears and feed by hand that way and see if that makes any difference because if you don't set the gears up just right it can sound awful.

Al.

[Alan .204Participant @alan-204]

This is the best picture I have at the moment will try to get a better on tomorrow when I get home from work.

Al.

[Nick_GParticipant @nick_g]

.

Hi Alan,

I have started suffering exactly the same problem as yourself recently. Likewise I have tried different steels, speeds, feed rates and 'known good' tools.

I am beginning to convince myself it's the headstock bearings as I am running out of other things it could possibly be.

Frustrating ain't it.?

Regards, Nick

[Alan .204Participant @alan-204]

Hi Nick I know what you mean, I did have a book for the Bantam and it showed how to set the head stock bearing's so I took them out completely cleaned and checked them over and they seamed fine I tried to get some new ones but you can't get them anymore, although I managed to find one set but at £600 plus I couldn't justify the cost, went through the book and set the bearing's as it said and it made no difference so don't think it's the bearings, but suspect it could be the apron or somewhere in the gear box or head stock drive, one other thing the motor has no rubber feet under it and remember a while ago someone saying this turned out to be there problem, will try to get some better photo's of it tomorrow in the mean time it just keeps going through my mind but I'm stumped.

Al.

[mahgniaParticipant @mahgnia]

Alan,

I had the same problem on my lathe. It turned out to be the crossslide screw nut was loose under the crosslide. Tightened it up and fixed the problem.

It may be worth checking that the tool is set properly to centre height also, and not moving in the toolholder. A slight error in tool height (too high) will reduce the back clearance of the tool, especially when turning small diameters, causing the tool to alternately cut and rub on the workpiece.

Andrew

[Ian S CParticipant @iansc]

Alan, is the lathe single phase, or three phase, some times the vibration of a single phase motor may cause a pattern on the work, if this happens, it's possible to isolate the motor from the lathe with a thick rubber sheet under it's foot, and rubber or plastic bushes in the mounting holes. If the primary drive is by belt, a link type belt is better at eliminating vibration.

There are other threads on this subject.

Ian S C

[Trevor WrightParticipant @trevorwright62541]

Allan,

Looks like "good commercial quality" mild steel from the photo. Pretty awful stuff but cheap. What finish do you get on Aluminium?

I have a single phase Bantam and get no vibration problems but cheap MS can only be machined with HSS tools with a 1-2mm radiussed point and 15-20° rake with oil, WD40 or suds and slower cutting speed if you want a finish. Or polish with emery if you are in a rush……

Trevor

[Alan .204Participant @alan-204]

Posted by Trevor Wright on 16/06/2014 13:06:57:

Allan,

Looks like "good commercial quality" mild steel from the photo. Pretty awful stuff but cheap. What finish do you get on Aluminium?

I have a single phase Bantam and get no vibration problems but cheap MS can only be machined with HSS tools with a 1-2mm radiussed point and 15-20° rake with oil, WD40 or suds and slower cutting speed if you want a finish. Or polish with emery if you are in a rush……

Trevor

Hi Trever your right it's just normal mild steel I thought it would turn OK but you may well be right, will try some ally tomorrow night hopefully, I use HSS pretty much all the time but I haven't tried 15-20 degrees so will give it a go, I have a small piece of EN24 will try that as well,

Thanks chaps it gives me something to think to think about, but the gut feeling is it's something to do with the drive somewhere.

Regards Alan.

[Alan .204Participant @alan-204]

Posted by Ian S C on 16/06/2014 12:51:19:

Alan, is the lathe single phase, or three phase, some times the vibration of a single phase motor may cause a pattern on the work, if this happens, it's possible to isolate the motor from the lathe with a thick rubber sheet under it's foot, and rubber or plastic bushes in the mounting holes. If the primary drive is by belt, a link type belt is better at eliminating vibration.

There are other threads on this subject.

Ian S C

Hi Ian it is single phase but I have nothing at the moment to make any anti vibration pads or feet for the motor but I'm looking it's a normal v belt but seams OK.

Regards Alan.

[Alan .204Participant @alan-204]

Posted by mahgnia on 16/06/2014 08:51:52:

Alan,

I had the same problem on my lathe. It turned out to be the crossslide screw nut was loose under the crosslide. Tightened it up and fixed the problem.

It may be worth checking that the tool is set properly to centre height also, and not moving in the toolholder. A slight error in tool height (too high) will reduce the back clearance of the tool, especially when turning small diameters, causing the tool to alternately cut and rub on the workpiece.

Andrew

Hi Andrew I will check the nut tomorrow night the tool is tight and on centre will keep trying different thing's and hoping.

Al.

[Ian S CParticipant @iansc]

Alan, If you ever find a mud flap off a truck, there's a good start to go under the motor. Great what you find when out and about on the bicycle. Another place to get a bit of rubber sheet, a tire repair shop that services trucks, my only trouble there is that I end up with the whole inner tube, when I only want a few square inches. These tubes are quite thick, but you can of course double it, and a bit of it wrapped round can do as a bush in the mounting holes.

Ian S C

[Alan .204Participant @alan-204]

Hi chaps tonight I ground up the tool again (should have taken a pic) this time put a bit more relief on all angles as Trevor suggested and nipped up the cross slide and top slide a bit more, now they would be to stiff to use but left them as just to see what happened, starting from the left ally and then a bit of a drill arbour from my core drill set it was bent so thought I would give it a go, next EN24 followed my mild steel, used WD40 with the ally and cutting oil with the others, all cut at 340rpm 1thou per rev feed, will try doing something with the motor next and see what happens, tonight's adjustments have made things better but not sure if was the extra relief on the cutting tool or nipping things up a bit, what does every one think, sorry for the photo quality IPhone I'm afraid.

Al.

[Andrew EvansParticipant @andrewevans67134]

Looks fine to me

[Trevor WrightParticipant @trevorwright62541]

Allan,

The surface finish is exactly what I would expect, your drill arbour is pretty good quality metal. EN24 and the mild steel always look like that when machined on mine, or any lathe I have worked in the last 40years old and new, so I doubt there are problems with your machine – more likely to be the old iron bedstead thrown in the melt to make the mild steel. You will get a similar finish with Silver Steel.

Trevor

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