DSM-59 clone vibration

[Swissmat]

I've been trouble shooting a bad surface finish on a Feeler FTS-27 (DSM-59 clone) for a while.
I am currently turning 1/2 brass with about 1.5in of stick out from a 5C collet and I get chatter marks and a consequently undesirable surface finish. I am not able to figure out where the looseness is and how to correct it. Here is what I do know:

1) 1-2 thou of radial play on spindle nose 5c taper (3 high spots (1-2 thou) that I believe correspond to overtightened 5c collets maybe?)
2) a few tenth of needle chatter on the axial runout of the spindle
3) collet closer yoke vibrates - I replaced the bearing, yoke bearing holder spring washers and set screws .. better, but no cigar .. the draw tube dimensions vs. the ID of the spindle are the same as published in another thread and commented on by Larry, IIRC 1.437 vs. 1.438 respectively ..
4) when using a box tool to turn the brass (zero top rake on grind) the work appears to grab the advancement of the tool .. so, the cut is jerky .. after a full dimension forward cut, it cuts more on the back stroke .. so I find myself going back and forth a few times to get a half decent surface finish and a final dimension

so .. is my problem:
a) spindle bearings? (they are completely quiet, don't run warm and axial runout is I think negligible?)
b) bent collet draw tube or misaligned yoke pins?
c) too much stickout? (1.5in in 1/2 brass)
d) is the problem on the turret side maybe? loose gibs? loose turret lock?
e) is it a potential motor or reeves drive vibration that shows up in the work?
f) all of the above
g) none of the above

Hoping to get some insights from you guys,
thanks for your time
best
Mat

 

[jim rozen]

I've been trouble shooting a bad surface finish on a Feeler FTS-27 (DSM-59 clone) for a while.
I am currently turning 1/2 brass with about 1.5in of stick out from a 5C collet and I get chatter marks and a consequently undesirable surface finish. I am not able to figure out where the looseness is and how to correct it. Here is what I do know:

1) 1-2 thou of radial play on spindle nose 5c taper (3 high spots (1-2 thou) that I believe correspond to overtightened 5c collets maybe?)
2) a few tenth of needle chatter on the axial runout of the spindle
3) collet closer yoke vibrates - I replaced the bearing, yoke bearing holder spring washers and set screws .. better, but no cigar .. the draw tube dimensions vs. the ID of the spindle are the same as published in another thread and commented on by Larry, IIRC 1.437 vs. 1.438 respectively ..
4) when using a box tool to turn the brass (zero top rake on grind) the work appears to grab the advancement of the tool .. so, the cut is jerky .. after a full dimension forward cut, it cuts more on the back stroke .. so I find myself going back and forth a few times to get a half decent surface finish and a final dimension

The three lobed wear on the interior of the spindle, where the collet seats is a classic high-wear condition. Will not cause chatter or other turning problems.

The 'grabbieness' on the box tool means you are not using a brass turning tool. It should have zero back and zero top rake. Postive rake tools will do what you are seeing.

 

[Swissmat]

hey Jim, thank you so much .. I'll have to re-investigage the tool .. I was sure I had it right (tested it on the Colchester and worked great) .. but I appreciate the potential solution!

 

[FredC]

"1) 1-2 thou of radial play on spindle nose 5c taper (3 high spots (1-2 thou) that I believe correspond to overtightened 5c collets maybe?)"

Worn spots on the taper and radial play are 2 different animals. On the radial play while not rotating the spindle and you are developing movement by pushing and pulling on the end of the spindle? If so, you are using moderate pressure by hand and not a 5 foot cheater? If you have .002 play in the spindle that is excessive. If this thing is really a copy of a Hardinge there is no adjustment and I think you need new bearings. If there is adjustment, then it is not a true copy.

Is it possible the draw tube is bent or maybe one of the closer cam/levers is worn more than the others? Vibration back there will cause the bearing are on the rear of a 5C to move. That cannot be good.
Do the motor and the varidrive yoke rotate without vibration under power?

Are your rollers on the box tool tracking when the diameter is finished to size? if they have clearance and are no longer touching that may be part of your problem. Maybe the rollers were correctly set on the Colchester and a little off when moved to the Feeler?

If you do need bearings maybe by fixing other issues you might be able nurse it along till you get your ducks in a row to replace the bearings.

On that spindle taper wear, I always put high pressure graphite-moly grease on the collet taper when doing production. I feel that lessen the wear on both the spindle and collet as well as get a little more closing power for given handle pressure. You already have some wear, lubrication might slow future wear.

 

[FredC]

Another point or 2 on the box tool. The last job I ran with one the rolls were on the bar diameter. If you are doing that make sure they are not too tight or loose. My Machinery's HAND BOOK SAY THE FRONT EDGE OF THE TURNING TOOL SHOULD BE 10% BELOW CENTER. Caps lock. Grrr. I always thought that was too much below center and used .01 to.03 below for everything. Too high might resist cutting and make the feed jerky in fits and starts. Box tool cutters can have some pretty aggressive chip hooks and feed pretty well by hand when everything else is correct. Photo is off the shelf cutters and inserts from Somma. Note these commercial cutters have a visible flat before the hook starts.

 

[jim rozen]

Worn spots on the taper and radial play are 2 different animals. On the radial play while not rotating the spindle and you are developing movement by pushing and pulling on the end of the spindle? If so, you are using moderate pressure by hand and not a 5 foot cheater? If you have .002 play in the spindle that is excessive. If this thing is really a copy of a Hardinge there is no adjustment and I think you need new bearings. If there is adjustment, then it is not a true copy.
.

+1

If the bearings are worn (preload gone from wear) then the easiest way to see that is axial play. There should be zero axial play, an play there means the bearings are toast. From his three spot comment I
take that to mean, he swept the collet seat with a dial indicator. Often high mileage machines will "grow" three lobs that are over a thou tall. That's where the collet slots are when the collet seats.

 

[Swissmat]

hey Jim and Fred, precisely, I swept the collet seat thinking it would indicate radial runout .. I'll re-do that measurement as you suggested Fred and report back .. I will tackle the tool grind first and see what happens and will have to devise a way to measure the collet draw tube for runout (or bend?) .. I can see the collet closer yoke physically move up and down .. so, clearly something's off .. on that note, does anybody know of a method to properly align the two yoke set screws on these closers? (the one that Hardinge tells you NOT to take apart when removing the closer from the machine) ..
thanks! I'll have more info and photos next time (when kids allow me a visit to my shop!)

 

[FredC]

Looks like the 2 screws with the 2 lock nuts on the link could allow you to raise or lower the yoke. Besides the tube being bent, the 3 collet closing lever/cams could be unequal in size and cause what you are seeing. Think that would be more likely than a bent tube.

 

[Swissmat]

Ok, I did some more measuring .. and, I think the bearings are shot after all .. well, at least the rear one .. but first things first. Here's the machine:

View attachment 340189

I measured the axial runout at the front of the spindle as suggested, by pushing hard but not with a 5ft cheater and still couldn't get the needle to budge ..

View attachment 340190

on the rear however, it's a whole different story .. I measured 15 thou by simply applying finger pressure .. I did take the back handwheel off and checked to make sure the bearing nut was tight .. I was able to tighten it a bit more but it did not significantly change the axial runout I could get on the dial indicator with simple figure pressure.

Since this is a clone I am hesitant to go buy the Hardinge bearings in the hopes they will fit this machine .. I guess I'll have to take these bearings out employing the "Gunner" method and then check the bearing numbers ..

Thanks a bunch for your guys's advise, I'll keep you posted!

 

[FredC]

Ask yourself what took out the rear bearing. If something about the collet closer/tube was hammering the bearing? If so, you need to fix that also. If the tube is squirming because it is bent or the fingers are wrong it will take a toll on the back bearing area of the collet then unduly wear the angled surface.

 

[Swissmat]

Fred, you've mentioned the fingers being wrong before IIRC .. can you elaborate on this?

The collet bearing was definitely shot by the wobble of the collet closer tube .. whether that had been misaligned for eons with the previous owner or not I can't tell .. I bought it in a pretty sorry state and gave her the once over .. but obviously now, using it, more things show their ugly head .. I'll have to strip that collet draw tube down and measure it ..

 

[FredC]

It has been a while since I have disassembled a collet closer but every Hardinge closer I have worked on had 3 fingers that are actuated by a cam surface and push against the collar with the notches. Those 3 levers need to apply pressure equally and the tube needs to be centered by a close fit in the end of the spindle. They need to be disassembled and greased every few years anyway even if you do not find anything wrong. Even if most of it is OK you have something going on in there. I had a bad closer on my Tsugami chucker and talked nice to the parts guy at Hardinge and they sold me one for an HC chucker. Everything fit except the link which needed be reamed from 1/2 to 13mm. I would assume you could get parts from Feeler for yours. Tsugami lost a court case for copy right infringement and part of the consent decree was that Tsugami would provide zero parts and assistance for their Hardinge copies.

 

[Swissmat]

I contacted Alpine Bearings and spoke with Derek .. he knew exactly which bearings were required .. I have a set on the way, pre-greased .. a lot of people comment on the very high price for these, but I was pleasantly surprised at 210$ for the pair .. the Chinese manufacturer wanted 180$ for each .. so I'm hopefully optimistic they'll solve my problem!

In case anybody else stumbles across this thread, the bearings are: Nachi 7011CYDU/GLP4

 

[Peter Colman]

Having machined brass on screw machines and capstans over the years, I have never used a roller box, if the turn is to a small diameter over a long distance, I use a twin tool, Ie a pair of tools set across the diameter so balancing the cutting forces. No top rake and 5* side and front clearance.
I have used this on machines with very worn spindle bearings and had good results.

 

[Swissmat]

Thanks Peter, I'll take that twin tool approach and see what happens ..

 

[Swissmat]

Ok, so I removed the bearings and I may have stumbled over some differences between the Hardinge DSM-59 and the Feeler FTS-27 .. it appears to my untrained eye, that the ********* B7011 BB bearings I removed are sealed bearings? While removing the spindle towards the tailstock, the bearings did not separate .. the rear bearing (drivepulley side) stayed in the casting and the front bearing came off with the spindle and nose ring .. I had to subsequently press off the bearing .. Can you guys enlighten me about the V-markings that are on the outside race .. upon re-install, should the small ends of the Vs point at each other or away from each other?

The Nachi bearings should be arriving today .. more soon ..