Tom Senior LV modifications.

I could but, the motor on my X axis is by curtesy of Ford motor company, namely a 2003 Ford Mondeo. Bought for a pricely sum of £8. So probably not a good idea.

On the other hand have you seen the size of a bridgeport table & the depth of cut folk do with them. The Tom Senior is only a baby at the side of one of those.

I never had a problem winding my table up & down apart from i have a old war wounded shoulder. So gives me jip whenever i do that job, same as hacksawing, kills me. If as you say it goes up in smoke then i will have to look further into it. One thing is it looks like the footprint is very similar on the larger model.

Also i will not be lifting any heavy items on the table. Or have not done since owning it. Home , Hobby use. Thanks for the heads up anyway.

Steve.

I do hope it works ok, I would like one on the X axis of the museums mill, but the cost at the moment is putting me off.

The 5 ACME internal insert came from APT today, and I found my mistake when making the toolholder. It will have to be modified after lockdown as the insert hangs off the end by 3mm. I will have to move the housing 10mm to fully clean up, but the bar is plenty long enough. The bronze is 2 1/2" long, and there will still be 85mm to fit in the tooplpost.

How long is the actual nut..

Steve.

I cannot remember the length of the original TS nut, but I have enough gunmetal to make two 2 1/2" long nuts. The flange with the bolts in it and the lower part diameter will be finalised when the knee is removed. The flange might be screwed on and locked in place, it's too early to decide. Only one of the bronze bits has had the 0.800" bore done, the other remains 17mm, I might look at the Y axis nut, who knows?

Yes i have a fair bit of play in the Y axis nut. Also my knee does as yours, bumps on the way down. Usually when the bed is offset one way & near the bottom. If it is in the centre it is usually ok.

I am surprised that no other forum members with the Tom Senior have not commented.

When i bought this mill i was looking for a Chinesium model but came up with nothing. I wanted to buy a Seig SX 3.5 twin turbo thingy from ARC. But was told that they would probably not sell me one. Maybe because they did not have any to sell. A real shame but it was to my advantage .

The reason i say that is that even though there is play in the nuts on my machine, it is so far superior to anything offered at the money from over the water for this far superior mill.

Steve.

Having both the TS and a large Taiwanese drill mill at the museum, I can say that the TS is nicer to use, but slightly smaller in capacity, and the end results are about equal. Neither can compare with a Bridgeport, which I recon is the ultimate home shop machine.

I may have to get another bit of gunmetal if I decide to make a new nut for the Y axis of the TS, I have a feeling the leadscrew is 3/4", too small for a 17mm starting bore. That particular nut was the best of the three on the machine, probably only 0.007" backlash.

It certainly sounds like you know what you are doing. I would not know where to start creating acme threads.

The guy i bought the mill from had just bought a Bridgeport & was rebuilding it. Very nice machine. Very large though. Made the Tom Senior look like its very little brother.

Good news. I have finished the Z axis build. I have quite a few video's & pics to edit & compile. I will put a link once done.

I was looking at the different units from China & was amazed at the figures they were giving for the torque. Mine said 135 lb-inch Some for the Z were quoting 300+ there was one quoting 750.

All i can say is it works very well. I put my whole body weight on the bed as it was rising & it did not slow at all. A success sort of. There is a problem with the internals. There must be some clutch mechanism within that free's when in neutral, Sometimes it is not engaging properly & sometimes it is fine. Probably twice in 10 attempts it does not engage properly. So it maybe a strip down to find the issue.

Steve.

Edited By Steviegtr on 09/11/2020 00:29:01

It should be ok as long as you keep alert for signs of distress from the motor, particularly when it is at the lower end of its speed range. The Align model intended for the Bridgeport Z axis has 760 inlb, but the weight involved must be three times as much as the TS. I wish I had taken some measurements of the knee mechanism and the length of the housing that the Z leadscrew dissapears into. I would like to put a 1" thick plate between the base and the main body to give a little extra Z height.

I have finally finished the video of the powered Z axis conversion on the Tom Senior light vertical. I am sure this could be made to fit any small to medium sized mill with a movable knee. The unit was intended as a X axis for a Bridgeport.

After fitting & testing it was found to be not completely engaging the dog clutch inside the unit. I removed the motor drive & stripped it down to see if any problems could be seen.

The internal workings of these type of units is basically the same. Just some larger than others. This unit is obviously a cheap copy of some branded model, so i was sceptical of what i would find inside. After the cover was removed, the internals seemed to be quite good quality. I could see how it worked & soon realised the shaft that moves up & down to drive the pinion was very stiff in operation.

The shaft, bearings & the drive sprocket were all covered in the blackest treacle like grease i have ever seen. I removed all this with GT85 spray & regreased with some LM35. After pulling & pushing the main spindle up & down ,it started to get much easier in operation.

Conclusions are yes it works properly now. It works very well with no presence of any labouring , underpower.

It is quite noisy in operation & i am sure a branded version would be much quieter. But the whole thing cost £139 so i think it was a worth while conversion for anyone thinking of doing on the cheap.

Steve.

Powered Z axis

I forgot to post a picture of the finished item. In the end i had to tilt the motor as i had not realised when the X axis was driven to the far right, the end housing was going to hit the speed control pot.

Steve.

The thoughts of using the unworn end of my spare Smart & Brown lathe leadscrew will probably be shelved. It is 6tpi as against the 5tpi of the TS knee. Mechanically, this would be the easiest option, but the scale would end up being a compromise. the Z would be 83.33 thousandths on an inch per turn. I know some lathe cross slides have the 6tpi pitch with the result of a scale of 0-80, but I think I will keep with the 5tpi and 0-100 as the gearing is 2:1. I will check carefully any uneven wear and address that.

Just a thought old mart on the length of the screw. If you remove one of the covers at the side of the nut base. Could you somehow see inside the cabinet for thread stick out. Or is that part enclosed around the nut.

Steve.

I don't think those covers would work, they are for coolant. The Z leadscrew goes down into a sealed tube to keep the coolant away from it. I could wind the knee as high as it will go and block it up. Then if the bolts holding the nut were removed, the nut could be screwed up the leadscrew and measured, and the depth of the tube could be measured as well. I want to find out the depth of the tube as I have enough bronze to make two nuts, and the magic word "antibacklash" comes to mind, but the length of the nuts and the length of the leadscrew are factors as well as the depth of the tube. If there is some leadscrew showing above the nut when the knee is fully lowered, then the antibacklash nut could be above the existing nut position. It is frustrating not to be able to even see the mill during lockdown.

So you want to know the distance the screw has left when the knee is wound fully down. I could measure mine by putting a straight edge across the knee base & using a mirror/ camera see how much thread is left. Minus the distance the nut & holder stand above the cabinet , that would give you the gap you required to know.

Steve.

I took a pic & did some measuring. This is the result.

Steve.

If you want tomorrow i could chock the knee from the bed & undo & retract the Nut to see the length of the assembly.

Steve.

Thanks, I will be able to incorporate the antibacklash above the level of the existing nut easily in that length of screw. I will also add some sort of cover to keep the threads clean. The two nuts could be screwed into an external tube and the adjustment would be easy to do. That thread in your photo must me unworn as it never reaches the nut.

I don't know much of my machines past life & not had it long. But with the knee fully down you only have 5mm of gap left. Is that enough to build in anti backlash.

Steve.

I may have misunderstood your first two posts of the 12th, I thought there was about 75mm of thread showing when the knee was fully down. Or are you saying that the base of the knee is close to the drip tray when it is fully down? If it is the latter, then nothing to worry, the knee backlash adjustment can be done with the knee partly raised.

Excuse me for butting in chaps, but.....

So long as the gib lock isn't engaged, If the weight of the knee isn't sufficient to overcome the friction of the gibs, in the Z axis, then the gibs are adjusted wrongly.

Given the weight of the knee is always in contact with the upper face of the Z axis leadscrew, there is no backlash.

There is still a modicum of backlash in the bevel gears conrolling the leadscrew; one would hope this was insignificant.

Rgds Simon