Tom Senior M1 Z axis problems

Hi,

I have just purchased a Tom Senior mill (my first mill) and it seems to be in generally good condition. However, I'm having some issue with the Z axis, and I wondered if anyone could help.

Both the X and Y axis' turn very smoothly but the Z axis is very hard to turn, I need both hands to move it. I appreciate the Z axis is lifting a lot of weight, but I had thought it would be easier than this, however I have nothing to compare it to. I have briefly tried to adjust the gibs but don't really know what I'm doing and have possibly made it worse. Is there some methodology I can use here or is it mostly about feel?

I'm also finding that at some positions I can turn the handwheel and nothing happens and then the knee will suddenly drop like it was bound up and suddenly released.

I have noticed that moving the X axis seems to ever so slightly change the Z height so I'm wondering if the knee is tipping forwards slightly?

Finally I can also very much feel the bevel gears at the top of the lead screw engaging with each turn, almost like they are set too far apart. I don’t know if this is an issue or not but I wondered if there was any way I could adjust that or grease it to improve the feel?

Thanks very much in advance for any help. This is my first foray into machining so apologies if I'm doing anything wrong or missed anything obvious.

Thanks

Hello Thomas. I have the Tom Senior light vertical, but i think the lower parts are all the same.

The thud you are hearing is a result of the column being tight. You are turning the handle & taking the tension off the table etc. If the gibs are too tight or the gib lock is engaged at the left side, then the table will at some point drop & take up the play in the Nut.

I have had it happen a few times when i have forgot to undo the Gib locking handle. Old Mart on this forum is a guru with the Tom Seniors. He is rebuilding parts right now. He may give you some good advice.

I have a youtube channel where i have done quite a lot of alterations to my machine. You may find some of interest.

My channel is just my forum name so should be easy to find.

Hope you get things adjusted ok.

Steve.

Hi Steve,

Thanks for your reply, I'll have a bit more of a play next week when I get back to the workshop. Can I ask how stiff the handwheel should be when everthing is adjusted correctly? On my mill there are two sets of bolts on the Z axis gib, three square headed set screws with nuts to lock them and three large bolts. What is the difference between these in terms of correctly adjustig the gib? The gib lock is definitely off though.

Yes I've seen your channel, there's a lot on there I plan to watch.

Tom

Hi Thomas. I think old mart has probably got a more defined answer than i have. I had all that section off , as when purchased it came in 4 parts. That gib block was removed. I refitted it & i think i asked the same questions about adjusting. I got it ok in the end . But cannot remember just how i adjusted it.

There are a few members on this forum with Tom Seniors. I will leave it to them to answer your questions. I would hate to give you the wrong info.

Steve.

Like Steve, I have a light vertical and believe the arrangement is the same. The three large hex headed bolts that face the rear of the machine should be tightened fully in use as they clamp the gib firmly to the knee. The three grub screw with locknuts on the side are the ones that adjust the gib. The procedure is to slacken the three large bolts just sufficiently to allow the gib to move but no more. The adjustment is carried out by slackening the locknuts and turning the grub screws and relocking. The three large bolts are then retightened fully.

I have found the adjustment is a bit tricky. Unlike the X and Y adjustment, gravity is involved and the parts are heavy. When carrying out the adjustment, it's important to centralise the table using the X and Y handles so that the centre of gravity is as directly as possible over the Z feed screw.

Even when properly adjusted, I get the jerky operation you describe if the table is extended fully to the right or left and especially if there is a heavy vice off centre in the same direction as the table. As Steve says, it can be a reminder too that you've forgotten to release the table lock.

As for the lumpy gear movement, it sounds like they could benefit from some lubrication. If you wind the knee up to the top, you can get at them from below.

Andrew

That might be the issue then, I had slackened the three large bolts as I thought the might be locks for transport or something. I'll try what you said and report back as to how i get on. When everything is properly adjusted should I be able to easily wind the handle one handed?

I probably need to start a whole separate thread on lubrication but for the bevel gear, would you guys use oil or grease there?

Cheers,

Tom

Hello Tom. It's certainly possible to raise the knee singlehanded with the handwheel, but I wouldn't describe it as 'easy' when going up. Coming down is easy by comparison.

As regards lubrication, there are two ball oilers on the left hand side of the knee. One is for the horizontal shaft that carries the handwheel and small bevel gear. The other is for the thrust bearing of the Z axis feed screw that takes all the weight. In theory surplus oil from that might find its way onto the large bevel gear teeth but mine, when I just felt them, were quite dry. I've treated the teeth to some grease and that has made the gear operation smoother.

I had a ton senior a few years back. One of my reasons for selling it was the weight of the Z axis. With a heavy vice and work on the bed it became a job at times to move it. Apart from that they are nice milling machines for light work. Make sure that there is no old oil on the ways and the gib,s are set right.

That was my reason for fitting the z power drive. Saved my shoulder a bunch.

Steve.

There are several reasons for the difficulty, wear in the leadscrew nut which allows the knee to drop when lowering, lubrication and the setting of the gib which can vary in tightness due to uneven wear throughout the travel. I have not been able to entirely eliminate the problem even after making a new nut which reduces the backlash to about 0.004".

I bought a long lever to quickly replace the wheel when there is extra weight on the bed which makes raising much easier. The lever might be off a Myford mill, it has 7 indexing lugs rather than a Bridgeport's 8 lugs and is smaller.

You should enter Tom Senior into the keyword box and Manual machines into the topic box. There is a lot of specific TS info there.

Edited By old mart on 14/08/2022 16:16:57

The gib for the knee is held on by three SHCS which are not noticable at first. They should be only just above finger tight when adjusting the three adjusters with the square ends and lock nuts. You need to carry out the adjustment in the least worn area when the bed is about 5" below the spindle. When the movement seems good, but not binding, then tighten up the three SHCS and recheck. If there is a lot of wear , you might have to run it slightly tight at the ends of travel to give the best results in the middle. Plenty of oil on sliding surfaces and dovetail and on the leadscrew does help. Page 13 in the manual from Denford.

Denford forums have some data sheets and manuals which can be downloaded, the knee mechanism is there.

https://www.denfordata.com/bb/viewforum.php?f=53

Edited By old mart on 14/08/2022 16:34:15

Edited By old mart on 14/08/2022 16:37:27

Not the same machine, but my Raglan mill recently developed similar symptoms. The feel of the gears was very rough and the handwheel difficult to turn. Proved to be the bevel gear mesh moving out of adjustment, ie too far into mesh. This was caused, in this case, by unscrewing of an adjustment nut at the top of the "Z" leadscrew next to the gear. Easily cured with a "C" spanner.

Maybe worth checking on your Senior.

Unfortunately, to get at the Z raising mechanism in the knee, everything above it has to be removed, and then the knee itself. A taper pin has to be knocked out to dismantle the bevel gears. There is a thrust bearing taking the load at the top of the leadscrew.

Thanks for all the replies everyone.

I’ll definitely be sure to give it all a good grease and oil and work it in. I get the impression the mill hasn’t been used much for a while and the more exposed Z axis has dried up a bit.

@old mart, thanks for the info on properly setting the gibs. The square headed bolts, do you just adjust them with pliers or are the specific tools for that? Interestingly on my mill the SHCS seem to have been replaced with standard hex bolts.

@Clive Brown, Whilst I do suspect the bevel gear is not set right (I can sort of rock the handle back and forth between the teeth of the gears) I really don’t want to start dismantling anything just now, I plan to just get everything working as well as I can before I start doing anything too drastic.

Thanks again everyone.

Old Mart,

Now that’s something fairly easy to do, thanks.
The usual ‘Why didn’t I …”

ThomasW,

My M1 has the same hex bolts for locking the Knee.

Geoff - Not melting today phew!

Edited By OuBallie on 15/08/2022 14:02:59

The square heads can be adjusted with pliers or any spanner that fits, even mole grips or an adjustable. They won't have to be tightened much over finger tight, but need the locknuts to keep them from unscrewing by themselves. You will find that TS used Whitworth, BSF and BA fasteners, so get some spanners specifically for work on the machine.

Our mill has the hex headed bolts on the knee, I was muddling them up with the Y axis gib screws.

Some 1/4 drive socket sets have a couple of double square sockets which fit square bolts, you might have some.