New to me - Colchester Triumph

[Lewis_RX8]

These are the exact results I used to get. Drove me mad .

Tell me about it

These are the exact results I used to get. Drove me mad .
I know you said you were using the same tools as me. Are they EXACTLY the same?

I am quite sure, same eBay link and everything, unfortunately, JB tools are closed so they are import ones. Same liney result on other tools

 

[fizzy]

Tell me about it


I am quite sure, same eBay link and everything, unfortunately, JB tools are closed so they are import ones. Same liney result on other tools

I tried tools that looked the same but results weren't great. The JB tools ones solved my problem. Maybe a slightly different rake angle or tip radius or something but I finally had something I was happy with.
The accuracy you are getting means there isn't much wrong with your lathe!

 

[Lewis_RX8]

I tried tools that looked the same but results weren't great. The JB tools ones solved my problem. Maybe a slightly different rake angle or tip radius or something but I finally had something I was happy with.
The accuracy you are getting means there isn't much wrong with your lathe!

Yup glad its holding good tolerances the cosmetic look of a finish wont matter too much for most parts anyway but ya know I want stuff to look nice

 

[prepman]

Had a little go at trying to check the spindle bearings, This was done while cold but to be honest, not sure what I am looking for here getting maybe 0.05mm/2 thou depending on pressure but the highest was with bodyweight pulling back and forth on nearly 2 feet of 2" bar securely held in the 3 jaw . I also hope my dial position was okay as didn't want any movement in the bar affecting it too much.

Feel free to completely disregard these readings if the technique is wrong I will have to have another go with any better ideas. Also would be interesting next time the forum triumph owners are dialing anything in on their machines what sort of play they have

Maybe the play is causing these odd lines where it feels smooth to touch but surface finish varies alot.

I think personally I would put the dial on the chuck to rule out flexing or even better on the spindle? On end of bar as one suggestion would magnify any movement? Like you I'm not sure what to expect as the Manual glosses over it.

No doubt someone will disagree?
But as Sherlock Holmes said," Once you have eliminated all other possibilties, the one remaining is the solution no matter how improbable" Or some such?

IMHO I think the lines are an entirely separate issue form the vibration as some else commented. More to do with tool shape and feedrate. Have a look at this link.

How to adjust Colchester spindle bearings

I recently bought an old 15" Clausing Colchester. I've had to make parts (cross feed screw, longitudinal feed pinion) and had the motor rewound. Now I'm ready to use it, and a test cut on 2"aluminum leaves chatter/wavyness on the OD regardless of depth of cut. I see that there is a threaded...

www.practicalmachinist.com

Ironically it's now made me rethink my parting issues. Preloaded (Gamet) bearings are not something I'm familiar with. On vehicles wheel taper bearings were finger tight when spun and then backed off. Looks like a mistake on preloaded could be a costly and heart wrenching excercise if wrong. circa £1,000?

 

[Sean64]

Had a little go at trying to check the spindle bearings, This was done while cold but to be honest, not sure what I am looking for here getting maybe 0.05mm/2 thou depending on pressure but the highest was with bodyweight pulling back and forth on nearly 2 feet of 2" bar securely held in the 3 jaw . I also hope my dial position was okay as didn't want any movement in the bar affecting it too much.

Feel free to completely disregard these readings if the technique is wrong I will have to have another go with any better ideas. Also would be interesting next time the forum triumph owners are dialing anything in on their machines what sort of play they have

Maybe the play is causing these odd lines where it feels smooth to touch but surface finish varies alot.

I'm probably going to get called out on this but anyways ,try a nice sharp hss hand ground tool with a tiny radius on the cutting corner ,take a 0.5mm cut .

 

[Ubique]

Sorry to jump in on this - it may have been already mentioned, could it be a harmonic resonance related to the inverter? maybe shift the frequency slightly either way (I know this will affect the speed) and see if there is any change for better or worse?

 

[MCKDAVID]

Belts can cause the vibration,however it’s unlikely. As the belts get older,the shore hardness of the rubber increases. You can for some reason,land up with belts with hard spots in them,that can induce vibration. Best bet is to get a relationship going with an industrial belt supplier. Order two sets of belts and mix and match until they are the same tension. You dont need to run it to do this,so, as long as your pulleys aren’t dripping with oil or grease,you can return the unused belts.

Totally agree, ask the supplier for matched sets, each belt has a production tolerance, they can match them pretty closely if you ask them, if you don't you'll just get any belts off the rack, could be one at the minimum, and one at the largest tolerance, on a multi belt drive you'll never get them tensioned correctly without at least one of them slapping. That's what causes the resonance, or pulsing (read vibration).. Changed probably thousands of belts over the years on fans, pumps maintenance etc, if you can stick to Fenner, without doubt the most reliable / consistent quality belts I've used, ok not the cheapest, but the least agrivation, especially if you've to take half the machine off to get to them.....

 

[waddycall]

I had vibration issues on my old lathe. It didn’t cause lines in the finish but it did cause a helical pattern on the part which is hard to describe - it was almost holographic! Wide helical stripe with quite a large pitch. It was a very lightweight lathe with the motor on the lightweight homemade angle iron stand. Bolting the motor to the wall solved it. I also had issues with lines in the finish. That was a speed vs feed rate vs tool geometry issue. I found a hand ground HSS tool set to rub slightly (as per LH Sparey) gave a mirror finish every time. My lathe was much less robust than yours (3” centre height).
Have you tried dropping the feed rate right down? Looks like your cutting a very fine thread.

 

[Munkul]

Maybe the play is causing these odd lines where it feels smooth to touch but surface finish varies alot.

If that's the insert you're using to turn a test bar, it's the wrong one!
That insert looks like a negative rake roughing type with a huge nose radius. You'll NEVER get a great finish from that tool unless you're feeding it hard and at a good depth.

For a test bar, your depth of cut should be a thou - with the SHARPEST tool you own. Either HSS or an ultra sharp aluminium positive rake insert. The idea is to take as much pressure out of the equation as possible, so any taper is due to alignment... (or slop in the headstock/chuck, hopefully not)
Also it's advisable to use a 4jaw for test bars for the increased clamping rigidity.

BTW 0.01mm on an old lathe is pretty normal

Buy some finishing grade DN** inserts and you'll start loving life.
Also, I learned the hard way, cheap carbide inserts look fine and work fine for roughing but still give a variable finish.

 

[prepman]

Belts can cause the vibration,however it’s unlikely. As the belts get older,the shore hardness of the rubber increases. You can for some reason,land up with belts with hard spots in them,that can induce vibration. Best bet is to get a relationship going with an industrial belt supplier. Order two sets of belts and mix and match until they are the same tension. You dont need to run it to do this,so, as long as your pulleys aren’t dripping with oil or grease,you can return the unused belts.

As far as I can remember,the top multi vee pulley is keyed to the shaft. Remove the pulley and check it hasn’t started to roll the key in the key way. This definitely causes vibration.

Also,wind up all the machine levelling bolts apart from the four on the corners. Level the machine and then snug down the remaining adjusters.

Lastly, hopefully this isn’t the cause in your case,but these spindles are easy to bend. Especially when numpties lift the machine by lifting it with a bar in the chuck instead of slinging it around the bed. I scrapped a seemingly little use Colchester Truimph 2500 for this very reason. Wasn’t worth the effort and expense of a new spindle and new gamet bearings to sort it out. There are at least three different spindles as I found out when I bought a secondhand spindle to try and rectify the issue of it trying to walk out the workshop at 450rpm or higher. So it got scrapped….

Good point about the pulley. As to lifting it's supposed to done with a eye bolt. I bought one after it arrived for future use, but no idea how it was maneuvered previously. On the Colchester Student Mk1 there a 3 feet and jack points. Grim story on the spindle issue.

 

[prepman]

It was a learning curve. I bought another one, and made one good one out of the two, scrapped the rest so that nobody down the line landed up in the same position I had found myself in

A noble gesture sir. Most people just paint over cracks and pass it along. As to experience.... in the words of the song 'The more I find out the less I know'

 

[Hood]

@Lewis_RX8
With those inserts in the pic if you chuck up a bit of 50mm or so with maybe 75mm protruding then do a 1.5 to 2mm DOC with a spindle speed of say 700rpm or so and a feed of .2mm or .3mm what is the finish like? Use flood if you can.

 

[Lewis_RX8]

Wow thanks for all the help on this folks

Pretty sure the belts are not the issue as same problems with running 1 belt as with running 3 and they are matched so no issues there.

@Munkul I know what you mean with the insert that was a photo from before I knew better just to show the finish , I was trying some of those ultra sharp alloy inserts and it still gave a line finish on lowest feed rate but it did feel smooth to touch just not a ground type finish others experience with them.

This is the alloy VCMT finishing insert result, Some of the Kennametal 0.4 radius inserts gave a nice finish but still lines unfortunately.

@prepman yes I am less inclined to fiddle with bearings when messing them up would pretty much scrap the lathe lol. Will have to try the play test once the lathe is warmed up aswell see if that changes the amount of play.

@Fortis maybe should have a go at the black art HSS sharpening

Sorry to jump in on this - it may have been already mentioned, could it be a harmonic resonance related to the inverter? maybe shift the frequency slightly either way (I know this will affect the speed) and see if there is any change for better or worse?

Intresting idea , The vibration is worst when the frequency was about 40hz which equated to near 1000RPM. When above and below the vibration is a lot less so this is certainly worth considering.

I had vibration issues on my old lathe. It didn’t cause lines in the finish but it did cause a helical pattern on the part which is hard to describe - it was almost holographic! Wide helical stripe with quite a large pitch. It was a very lightweight lathe with the motor on the lightweight homemade angle iron stand. Bolting the motor to the wall solved it. I also had issues with lines in the finish. That was a speed vs feed rate vs tool geometry issue. I found a hand ground HSS tool set to rub slightly (as per LH Sparey) gave a mirror finish every time. My lathe was much less robust than yours (3” centre height).
Have you tried dropping the feed rate right down? Looks like your cutting a very fine thread.

Intresting to have it rub slightly rather than cut , Would you have any photos of the grind on the tool as I say I have only ever used carbide. My motor is mounted in the lathe cabinet.

@Lewis_RX8
With those inserts in the pic if you chuck up a bit of 50mm or so with maybe 75mm protruding then do a 1.5 to 2mm DOC with a spindle speed of say 700rpm or so and a feed of .2mm or .3mm what is the finish like? Use flood if you can.

Coolant pump is nearly set up but will have a go without it and post some pics.

@Johnnybravo Good call on the levelling , I had a loose foot which made vibrations even worse that is snugged up now and I am hopeful that the vibrations are not caused by a bent spindle as they are worse at 1000RPM at full speed 1200RPM they still vibration but less so where as I imagine a with a bent spindle the faster it is the worse it is.

 

[waddycall]

ntresting to have it rub slightly rather than cut , Would you have any photos of the grind on the tool

Sorry, no I no longer have a lathe sadly. It was a technique I got from “the amateurs lathe” by LH Sparey (not JR Hartley), a book aimed at people with small lathes. A lot of it is based on myfords. Hopefully the following pic will give an idea. Used to get a perfect finish and really good accuracy on a flimsy old bitsa lathe by doing this.

 

[daedalusminos]

Had a little go at trying to check the spindle bearings,

You need to get the gauge on the spindle nose behind the chuck - the way you're doing it you'll be measuring bar flex and chuck movement. I would measure cold and then repeat warmed up.

 

[Lewis_RX8]

You need to get the gauge on the spindle nose behind the chuck - the way you're doing it you'll be measuring bar flex and chuck movement. I would measure cold and then repeat warmed up.

Like this ?

Should I just spin it and measure runout or try and flex it in some way?

Thanks

 

[Pete.]

When you're checking for loose bearings do it by lifting up on the chuck not barring it front to back. You'll be lifting against the weight then and any looseness will cause a jump in the needle.

 

[Hood]

It is hard to tell from pictures but I think you are just seeing the feed lines. You will always get them, how far spaced out will depend on the nose rad and the feedrate. Material also plays a big part in how visible they are.

 

[daedalusminos]

Like this ?

You need something in the spindle to act as a lever and have the gauge perpendicular to the axis for an accurate reading.

Mount the gauge on the headstock contacting the top of the spindle behind the chuck

 

[Hood]

Here is an example of what I am saying.
Both were same insert, same spindle speed, same depth of cut, same feedrate.


First is some kind of mild steel, no idea exactly what.

Next up is a piece of F51