Boxford Screwcutting box / Leadscrew binding

[andrew wrigleyParticipant @andrewwrigley45179]

Sticking Leadscrew?

[andrew wrigleyParticipant @andrewwrigley45179]

Hi Folks, this is my 1st post on here so hi to all other home engineers out there.

I’ve just purchased a Boxford AUD which is generally all ok, with no issues other than when making a cut using a feed with the clutch occasionally the machine binds up. The feed speeds are from normal to slow and I’ve tried using a variety of gear combinations, the gears aren’t jumping or grinding it simply tightens up and stalls. Once the clutch is released and the motor restarted all is ok. The motor sounds like it’s starting to labour as soon as the star wheel is tightened. On a hand fed cut this is not happening.

i suspect there may be an issue with the gearbox (to leadscrew) output shaft but I dont know how to remove the screw cutting gearbox. The 3 screws that I believe secure the box to the bed are covered by the main headstock casting?

Any thoughts or ideas or advice on how to remove the box for a service. Or is there something I should look into before I dive in?

Thanks

[Speedy Builder5Participant @speedybuilder5]

follow this link and print yourself the boxford manual.

**LINK**

[Yngvar FParticipant @yngvarf]

Do the same thing happen if you use the half nuts?

That will tell you if the problem is in the gearbox or the apron.

[andrew wrigleyParticipant @andrewwrigley45179]

Thanks for the manual link, unf. there’s nothing in there about removing the box.

I’ve just tried on the half nuts, as it only happens occasionally I can’t be 100% sure, but the symptoms appear the same. It really slows the motor if u add resistance to the hand wheel, but I this could be normal?

[HopperParticipant @hopper]

Posted by andrew wrigley on 12/03/2019 21:31:22:…

…It really slows the motor if u add resistance to the hand wheel, but I this could be normal?

That sounds odd. Could it be you have a motor problem? Will the lathe cut metal in the normal manner with heavy cuts etc without stalling the motor? Or it could be something inside the apron jamming up under load.

There is a parts manual here **LINK**

that might show how the gearbox comes off.

Edited By Hopper on 12/03/2019 22:25:53

[BazyleParticipant @bazyle]

Taking the gearbox off is not the first thing to think of when you don't know if it is the gearbox or the saddle.

First run the lathe spindle only to make sure that and the motor are fine with the belts slack in case something does get stiff.
Then run the geartrain up to the box with both the gearbox handles dropped down so they are not in a setting detent hole just right down. They are then out of mesh. Run for a while.
Then engage only the left one, run for a while, then both, engaged.
Obviously without the saddle moving just running the gearbox (but make sure you have oiled it) and the belts slack.
If that is all fine the gearbox is checked out.

Put oil in the saddle gearbox with a small tray under for the drips. Move the saddle using the handwheel but apply varying amounts of longitudinal pressure to the saddle to see if that a affects it.

Finally try autofeed. If it has problems that is the apron not the gearbox.

I'll post later how to remove the bits.

[HopperParticipant @hopper]

Could it be that somehow both the halfnuts (lever handle) and the friction feed clutch (star handwheel) are being allowed to engage at the same time, thus trying to move the carriage at two different rates at once, resulting in jamming? Could be the halfnuts out of adjustment and not disengaging all the way? Or something adrift inside the apron behind the feed change lever allowing double drive?

 

Edited By Hopper on 13/03/2019 07:03:28

[andrew wrigleyParticipant @andrewwrigley45179]

Thanks all, I’ll have a work through some of the suggestions this evening. I’ll work up from the motor through to the headstock and then onto the box.

I have tried some of this already where I think I’ve established that I can get a reasonable cut on if I hand feed it, but once the screwcutting box is engaged and then underload, ie cutting, the motor is loading up more than I expect. This is what made me think of the thrust bearings on the lead screw.

[Clive Brown 1Participant @clivebrown1]

Just to add a little to above; with the gear-train disengaged from the spindle, and the saddle and cross feeds disengaged, the input shaft of the gear-box should turn easily by hand. With the lead-screw rotating check that it isn't slightly bent. Temporarily slacking off the 2 bolts holding the R-H lead-screw support allows a bit of float if the lead-screw is binding. It's a fairly close fit through the saddle gear, which supports it.

Does the saddle easily traverse the full length of the bed by hand?

Don't try to remove the gear-box yet, but it should be possible without removing the headstock, ball-ended allen keys are a help for the 3 screws into the top of the 'box.

Edited By Clive Brown 1 on 13/03/2019 08:51:05

[HopperParticipant @hopper]

You would think that if the bearings on the lead screw were seizing up solid enough to stall a 1hp motor, those bearings would have to be too hot to touch and probably screeching in protest. Touch test might soon tell.

Good idea by Bazyle above there too to slacken your belts so you don't damage the drive line or burn out the motor while trying to locate the source of the problem.

[Brian WoodParticipant @brianwood45127]

Andrew,

I think the tests to try and pinpoint the trouble have been described and should help track it down.

Bur before you pull the apron apart to get to the star-wheel clutch, have you tried oiling it? I know it is a basic question but there are long drillings involved and plug like wicks that can dry out and effectively seal the oil way. The clutch itself consists of two disc springs [ Belleville washers] fitted facing each other and it works by varying the compression between them. If those components are dry in their housing, they will tend tighten up from frictional effects within the housing and apply an overload which may be sufficient to overcome the drive.

Hopper for information The interlocks that prevent double selection are completely effective and can be disregarded as a possible explanation

Regards

Brian

[HopperParticipant @hopper]

Thanks Brian. Long time since I fondled the innards of a South Bend clone. Ah the grey cells, the grey cells. I just can't picture the exact set up. (Although, as a famous man once said, all things can be broken. )

Edited By Hopper on 13/03/2019 12:53:26

[HollowpointParticipant @hollowpoint]

I may be completely wrong but it sounds like a bent lead screw to me?

[Bill Davies 2Participant @billdavies2]

Perhaps my PC has a virus or malware, but the Boxford manual link asks me to install an exe file, 'ReimageRepair.exe' which my Norton Security flags as a file that could harm my computer. I attempted this twice, but did not download the file.

Bill

[Alan CharlestonParticipant @alancharleston78882]

Hi Andrew,

If you want to get the gearbox off you'll need to slacken off the bolts holding the headstock in place and slide it forward which will reveal the cap screws holding the gearbox in place.

This is not easy as the front bolt holding the headstock down is really awkward to get at and there's very little room to swing a spanner between the sides of the bed. I ended up buying a good quality 15mm ratchet ring spanner to get it out. Due to the restricted swing available, it needs to have a fine ratchet action so a cheap one won't do.

Regards,

Alan

[HopperParticipant @hopper]

I'd avoid all that to remove the gearbox until every other possibility had been eliminated. Brian's suggestion about the clutch belleville washers binding or running dry would certainly be something to check first. As would feeling for heat around the bearing areas in the gearbox housing.

[andrew wrigleyParticipant @andrewwrigley45179]

Hi, I’ve been through a few checks including checking the leadscrew for straightness, it is. Checking things are running ok without the gearbox connected etc. and all is ok on the saddle. I’ve measured the current draw on the vsd and checked a few parameters, and think it’s possibly the vsd settings. So I’ve been through all the settings, optimized what I can upped a few parameters such as the ‘torque boost’ that ups the volts when under load (I think). Anyway things seem a little better and it’s not bogging down quite the same. Not having another lathe to compare it with leaves me guessing a bit, but I’ll try it for real tomorrow and report back.

Thanks for all the support so far

[SillyOldDufferModerator @sillyoldduffer]

Posted by Bill Davies 2 on 13/03/2019 22:52:38:

Perhaps my PC has a virus or malware, but the Boxford manual link asks me to install an exe file, 'ReimageRepair.exe' which my Norton Security flags as a file that could harm my computer. I attempted this twice, but did not download the file.

Bill

Quite right Bill – don't download and install it. The link is a honeypot; it's to a website pretending to have desirable content so that search engines will list it, but actually delivers something else. In this case it's a program that pretends to find faults on your computer in hope that you will then pay for another program to 'fix' them. Other examples are nastier. Norton correctly identified the link as malware.

Dave

[andrew wrigleyParticipant @andrewwrigley45179]

Same here! Fortunately didn’t download it either.

[HopperParticipant @hopper]

Posted by andrew wrigley on 14/03/2019 20:11:16:

…I’ve measured the current draw on the vsd and checked a few parameters, and think it’s possibly the vsd settings. So I’ve been through all the settings, optimized what I can upped a few parameters such as the ‘torque boost’ that ups the volts when under load (I think). Anyway things seem a little better and it’s not bogging down quite the same. Not having another lathe to compare it with leaves me guessing a bit, but I’ll try it for real tomorrow and report back.

Thanks for all the support so far

Rule #1 of trouble shooting: Always check the last thing that was worked on. In this case, the installation of VFD.

Should not bog down under load if its functioning correctly. You might try putting the belt in the lowest speed position on the multi-step pulley. This will get the motor revving a bit higher and maybe give it a bit more torque.

[SillyOldDufferModerator @sillyoldduffer]

Posted by andrew wrigley on 14/03/2019 20:11:16:

Hi, I’ve been through a few checks including checking the leadscrew for straightness, it is. Checking things are running ok without the gearbox connected etc. and all is ok on the saddle. I’ve measured the current draw on the vsd and checked a few parameters, and think it’s possibly the vsd settings. So I’ve been through all the settings, optimized what I can upped a few parameters such as the ‘torque boost’ that ups the volts when under load (I think). Anyway things seem a little better and it’s not bogging down quite the same. Not having another lathe to compare it with leaves me guessing a bit, but I’ll try it for real tomorrow and report back.

Thanks for all the support so far

Might be worth getting a feel for how stiff the powered-off lathe is in normal conditions by turning the chuck by hand whilst everything is engaged. Then, next time it binds up, switch-off immediately and repeat the test. If it feels harder to turn the chuck likely something is binding. If it turns as freely as before, the motor/VFD is suspect.

Dave

[HopperParticipant @hopper]

Sorry, I misread VSD as VFD last post. Is it the factory variable pulley system? I would be suspicious of that as source of problem. The reason as I said in a very early post being that it seems odd that a leadscrew or apron problem coiuld seize up the system sufficiently to stall a 1hp motor. With the reduction gearing through the change gears and gearbox, it would take massive jamming force on the leadscrew to stall the motor. You would expect gear teeth to be flying off in all directions from the change gears, or at least a shear pin to shear somewhere along the line.

[HopperParticipant @hopper]

Or could be a combination of drive/motor and something like that apron clutch Brian Wood mentioned.

[Speedy Builder5Participant @speedybuilder5]

Don't overdo the headstock greasers. On a cold day, if I screw the greasers down a couple of turns, it will reduce the speed of the headstock until things warm up. The headstock bearings don't need much grease. What gear train have you got between the headstock and the leadscrew ?

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