X-Axis Feed Problem...

Good morning everyone...

So I'm going to be honest and admit that I think I screwed up! I'm a newbie here and still learning what I'm doing so please, done shame me too bad :-) I have a Series 1 J with a 1HP motor on it.

Yesterday I was taking what was probably a bit too heavy of a cut and [power] feeding in X (right to left) possibly a bit faster than I should have using a 1" roughing end mill. Things were going along alright and then the cut bogged down and the table kicked back towards the right about .250". I stopped the machine, very quickly.

Now what I'm left with a is a very strange feeding problem in X. When I spin the crank, instead of getting .200" on every revolution I'm getting more like .020" on every revolution. But, it's only doing that when I feed right to left. If I feed left to right, there's now close to .200" of backlash in the screw but once I get past that then I'm feeding the expected .200" per rev when I turn the crank. I don't understand it.

So far I have checked the following:

. Bearing blocks are both seated correctly and tight.
. Hex jam nut on the cranks are snug.*
. Power Feed will still engage and doesn't bind or grind.
. The feed nut retaining screw is snug and there is not a lot of slop in it.
. Washer head screw backing up the feed nut retaining screw is snug.
. The gib is snug and in good shape, even removed and inspected it.

* If I tighten the hex jam nuts on the crank down 'tight' then I can't turn the cranks at all - but it's always been this way too, is this right?

I'm not sure what else there is or what else I should check. I'm trying to avoid pulling the screw out or pulling the table off (which requires removing the DRO).

Any advice would be greatly appreciated!

Thanks,

-brian

Probably broke the brass nut or the table casting. Most likely previously abused as I've never heard of one popping from a cut before the endmill breaks.

Tight nuts on X cranks should NOT cause a bind ! If Servo style feed not properly shimmed gear I would think. On the left side nut can be very tight without issues.Where in AZ? Pulling the X axis nut would be a starting point.

Thanks for the replies! JohnEvans, I'm in Havasu.

If I tighten the jam nuts on the cranks down all the way it's totally bound up and won't turn. It has alwasy been this way. When I got the mill it had the old Bridgeport Gearbox power feed. I removed it, changed the screws and installed a standard bearing block while I was rebuilding the bottom before I installed the Servo power feed. All these configurations have led to the feed being bound up when the jam nuts on the handles were tight so I keep them slightly loose.

And a quick back history, my late great uncle bought this mill new in '56. When he passed in '94 it went to my cousin and was used where we work (not a family business) for ~20 years until I talked him out of it. I brought it home from San Diego to Havasu. I sent the head out to H&W for a complete rebuild and did the bottom half myself - new screws and nuts, one shot oiler, power feed, complete cleaning.

I didn't see any damage to the table nor the left side bearing block when I rebuilt the bottom so I kept those. I'd purchased a new right side bearing block from H&W but returned it after I put the Servo on as it came with a new one anyway.

Plastikdreams, you mention brass nuts on table casting? Are you referring to the feed nuts within the yoke? If so, those are brand new, I repalced when I rebuilt it 6 months ago and then I moved. This weekend was the first real use since the whole thing was rebuilt. Or, are you referring to something that was casted onto the table --- I'm not recalling anything in the table casting but yeah, I could've missed something!

Thanks again guys!

Yeah the nut that holds the screw captive so the table moves. If that's banged up that's the only thing I could think of would cause the symptoms you describe. Normally they pop when someone has a power feed and doesn't set the stops right...they put it on and walk away, the table feeds to the max, and boom shits broken lol. In your case it may have been the heavy cut who knows...I'm thinking thanking the table off is your next plan of action though. The description of the failure sounds about right for it.

Fairly surprising as I've taken some hefty cuts on a Bridgeport....if it is the issue, I'd pay the extra coin and go with ballscrews...tougher and way more accurate. And you can climb mill without worrying about the table jumping.

Check out the print below
http://hqtinc.com/customimages/leadscrew_s1.htm

I was thinking number 7 the bearing retaining rings screws may have stripped out. Or maybe you forgot one of the bearings when you assembled the screw. As what John said tightening jam nuts 13 should not make it so you can't turn the screw unless it wasn't assembled right.

Richard, thank you for the print. It will make a good reference!

This weekend I will pull the bearing blocks off both sides and see what I find. I'm really hoping not to take the table off since that requires removing the DRO and the like and that bugger is heavy! I'll post an update with what I find.

Thanks again,

-b

Good luck

BDMcGrew said:

I'm really hoping not to take the table off since that requires removing the DRO and the like and that bugger is heavy!

Click to expand...

The table is easy. Take the DRO scale off first. Pull the screw handle, dial, bearings from right side, loosen gib and shove table off the saddle onto roll around cart that you have cranked the table down or up to its level. You'll then be looking at the x-Y screw dogbone and likely your problem. While in there, clean the ten tons of chips out of everything. Hopefully no grease to remove from the PO's grease attack...

John

WHen you tighten your nuts, are the dials binding up against the bracket? You can check this by taking the dials off of the dial holders (or simply loosing the dial nut and letting the dial float freely on the dial holder) and tightening everything up... at this point, does it still bind up with both sides tight? We have seen it where there needs to be spacers between the dial holder and the dial.

Jon
H&W Machine Repair