Thread chatter on Grizzly 4003G resolved...finally..!!!

[eww1350]

Superman...your threads look fine to me...if there is any minor chatter I cannot see it in the photo...your threads look good for threads cut at 70-100 rpm...you can finish them with some 400 grit paper or a super fine diamond file...and they will be smooth as butter.

Good photos..

Eddie in Texas

 

[TRA]

Are you doing 1 or 2 spring passes?

Your wanting the best finish to be on the back side of the threads, towards the shoulder. The action should have the best finish facing the bolt.

In reality, proper threads should have the same finish on both sides, but, jus sayin

I would use a micrometer,....those dial calipers will, remember i said will, bite ya in the ass someday

 

[frwillia]

What do you have between the jaws and the barrel.
Butch

Butch,

Good question. Looks to me like the Superman's barrel is clamped directly in the chuck jaws.

Superman,

If you have the barrel clamped directly in the chuck jaws, you might consider using something to hold the barrel that allows the breech to move in response to muzzle adjustments. This is what I do, other folks use different methods:

The ability for the breech to respond to adjustments at the muzzle is an essential element of the two most commonly used methods to align a barrel through the headstock. If the barrel is clamped solidly in the jaws, it points in whatever direction the jaws point, which will only be the same as the bore inside the barrel by coincidence.

Fitch

 

[Ron of Va]

Well I completed the Fix, and found it showed a modest to good improvement in the thread chatter, but the chatter is not completely gone at 70 rpm. But completely goes away at 200 rpm using Sandvik full profile inserts. A freshly sharpened HSS tool at 70 still showed chatter.

I did not have the “super feet” kind of neoprene washers eww1350 used. I used the old metal washers with my homemade neoprene washers next to the casting. So that might be my next step.

I have a couple of comments that might help the next guy who tries this fix.

I found the anti-vibration pad so squishy that it was next to impossible to get good belt tension on the belts, without crushing the pad. Even if the belts were properly tensioned, by the time the machine was run for a while, the belts were loose again.

The belt loosen for two reasons, the casting has a single hole for a single bolt next to the pulley. This acts as a pivot, for the fan end of the motor to drop down, thereby releasing the tension on the pulley and misaligning the pulleys. The motor twists counterclockwise due to the pressure from the belts.

I used a coupling with a bolt to act as a temporary jack to keep the desired tension on the belts. Then I measured inside the slot with a snap gauge. I measured the distance from the top of the bolt to the top of the slot. I cut a piece of 3/8 inch brass rod and put into the slot above the bolt, then tightened the bolt and removed the jackscrew. Belt tension solved.

I went to the fan end of the motor and did the same thing there with another jack screw, and pry bar, this time lifting up on the mount casting. I inserted another piece of brass rod above the bottom bolt. This lifting will increase any tension you might need left in the belts and prevents the motor from rotating counterclockwise, but I was primarily interested in making sure the pulleys were aligned. The brass rod will prevent the casting from dropping down.

I hope this helps.

The photo below shows the brass rod. I used brass to keep the threads of the bolt from being damaged. I put a piece of duct tape on the brass so I could pull it out of the slot if needed.

The final photo is of the motor as I found it prior to the Fix. It had dropped down on the fan end, and probably contributed to my bearing failure.

 

[Bnhpr]

What do you have between the jaws and the barrel.
Butch

I don't think that's a bbl, Butch. Just a piece of HP tubing or something to practice on?

 

[freddyp]

Take off the outer drive belt and pitch it, before you get extreme....it's apparent in your photos that the belts are not matched or in proper tension.
Dual V-belts are nothing but trouble. It's almost impossible to get them to not chatter.

I just started to have the same problem, chatter. I notice that the belts were getting loose with time and when I applied pressure to them the vibration would stop. I took the suggestion of removing one of the belts and problem over. The 4003G now runs quiet and no more vibration.

 

[Superman]

It's actually a take off barrel. Before I started cutting on something that mattered, I did several passes on take offs and drops my barrel manufacturer sent me.

When holding a barrel for the actual work I am using 1/2 wide .100 thick pieces of aluminum between the jaws and the bbl., much like Gordy Gritters uses. I like the looks of the wire, seems like it would let the bbl tilt easy without binding or bending when adjusting the spider. Gordy mentioned not being fond of the wire and preferring the aluminum shims.

 

[frwillia]

It's actually a take off barrel. Before I started cutting on something that mattered, I did several passes on take offs and drops my barrel manufacturer sent me.

When holding a barrel for the actual work I am using 1/2 wide .100 thick pieces of aluminum between the jaws and the bbl., much like Gordy Gritters uses. I like the looks of the wire, seems like it would let the bbl tilt easy without binding or bending when adjusting the spider. Gordy mentioned not being fond of the wire and preferring the aluminum shims.

The copper grips the barrel well and doesn't cold flow like aluminum although the barrel probably isn't in the lathe long enough for cold flow to be an issue. An unintended feature of the copper rings (I use one on each end) are that they also help to protect the barrel as it's being inserted through the headstock. Worth a try anyway. You might like it.

Fitch

 

[eww1350]

The copper grips the barrel well and doesn't cold flow like aluminum although the barrel probably isn't in the lathe long enough for cold flow to be an issue. An unintended feature of the copper rings (I use one on each end) are that they also help to protect the barrel as it's being inserted through the headstock. Worth a try anyway. You might like it.

Fitch

How did you get the copper wire to wrap around the barrel with a close fit? did you use a jig to bend it around a mandrel?

 

[frwillia]

How did you get the copper wire to wrap around the barrel with a close fit? did you use a jig to bend it around a mandrel?

I bent it around the piece I cut off the breech. Then tweaked it to be a bit smaller so it fit tight and wouldn 't slide around.

Edited to add: I clamped the cut off piece in a vise. Bent a right angle on the end of the wire to hook the vise jaw (held it there with pilers) and then bent the wire around the piece. Slid it off, pulled a bit to make diameter slightly smaller, cut it with a honking big set of nippers, and it was done.

I bent the piece for the muzzle around the part of the barrel blank that would eventually be cut off, then slid it up the barrel to where I needed it with a nice tight fit as a result.

Piece of cake.

Fitch

 

[300jcc]

Thanks for all the info, here. Yeah - the dual belt situ is problematic at best. I also tossed my "spare" belt in favor of less vibration. However, what I didn't even think about was getting one of those linked v belts another member posted. ANYTHING to keep vibration down is necessarily good.
That's a drag about Grizzly's tech staff. You'd think that with the owner being a shooter - who actually claims to have "...cut [his] teeth repairing metalworking lathes" - that he would make SURE to have the best tech support around. At the VERY least, if I'm a tech guy and somebody has a problem - but can describe their set-up and procedure and it sounds CORRECT, then why not try to investigate further to get a "real" answer?
Obviously, I don't know the particulars - but I see this as the rule rather than the exception these days. I'm just disappointed, as I have bought quite a bit of equipment from them (no lathes, though).......let's hope nothing breaks...