Harrison M300 screw feedbox issue

[Crazeewelder]

They no longer supply the Rubber Bellows ...even at those prices

As I mentioned earlier in the thread, there has been an issue with the gears not aligning correctly when gears are selected.
I’m going to address this when the gearbox is back together by turning the selector shaft sleeves 180 degrees and re drill the locating holes for the ball bearing in the knobs while setting the gears in their correct positions.
This along with replacing some of the plain oilite bushings for flanged bushings where required to eliminate some of the lateral movement in the top gear shaft should keep everything aligned better and reduce the risk of crashing gears.
BTW the machine was bought with the ‘R’ gear not working so the initial cause of the damage is unknown.
I have however discovered that the clutches on the leadscrew and feed rod were tightened to the max and have too many discs in them(according to the manual) which means all the load went straight into the feedbox causing destruction of the 19T gear.
If anyone has any knowledge/experience setting up the clutches I’d appreciate the help.

Remodelled steering boot for a tenner does the job.
View attachment 171212

Only problem I've found, the oil eventually melts the vulcanised joint

well guys I finally got it all back together and she purrs like a kitten.
All new bearings and bushes in the gearbox, 19T gear replaced, all cleaned out and rebuilt as good if not better than new.
Re drilled all the selector positions on the sleeve shafts and stripped cleaned and re built the torque clutches on the feed screw and saddle drive( after picking a fitters brains at Colchester Machine Tool Solutions/formerly 600 group) with all the Belleville washers set up as per O.E.
Just need to set the torque on them when I’ve finished a few other little jobs off.

And yes Milkybars, I did the steering rack gaiter trick too.
I reckon it’s the detergents in hydraulic oil that eat away at the rubber(maybe).

So alls good now, just in the process of tracking down a fixed steady.

 

[Crazeewelder]

Here’s a few pictures

 

[scottmk1]

Good work. Can you tell us what the fitter at Colchester told you about setting up the clutches?

 

[Crazeewelder]

Yes Scott, the Belleville washers are in packs of 16 in the feed screw and 12 in the saddle drive.
The packs should be divided in half and set opposite so the smaller diameter faces come together.
They then need to be set so they release at 800lb to 1200lb of force, or use the machine and apply a heavier cut than you would normally to judge the break point of the clutch.

 

[scottmk1]

That's great thanks. Did they say how to check the force?

 

[Crazeewelder]

That's great thanks. Did they say how to check the force?

Unfortunately not but he did say that special tooling was required to do this but he’d never seen it done.
You would think that a torque wrench with a modified pin socket would do the job but what the torque setting would be to replicate the force from the headstock/gearbox through the shaft I have absolutely no idea.
A bit of trial and error needed I think.
If I do ever get it set right and the modified tooling then I’ll post the results on here.

 

[scottmk1]

OK thanks again. I have 2 sets to rebuild at some point, one set as per yours on my M300 and another on my M350.

 

[Pete.]

View attachment 171657 Yes Scott, the Belleville washers are in packs of 16 in the feed screw and 12 in the saddle drive.
The packs should be divided in half and set opposite so the smaller diameter faces come together.
They then need to be set so they release at 800lb to 1200lb of force, or use the machine and apply a heavier cut than you would normally to judge the break point of the clutch.

You can adjust the spring force of bellville washers by doubling up.

 

[scottmk1]

I guess you could work out the compression required on the springs and that would translate to an amount of turns of the nut.

 

[Crazeewelder]

You can adjust the spring force of bellville washers by doubling up.

That would work if the Belleville washers were alternately opposing (“in series”), doubling up would make the configuration “parallel series”.
But this configuration requires 6(or 8) in parallel left hand and 6(or 8) in parallel right hand and the inner diameter faces meeting together in the middle as per the diagram.
This gives way more compression than “series” or “parallel series”.
You could also install them all in parallel like who ever rebuilt the ones on my machine and I can guarantee that if you over tighten them your feedbox will require new parts if it ever experiences more torque than it should, but they’ll never slip!!!!!!!!

 

[Pete.]

What I meant is that you could add them singly to the stack to adjust the overall spring force. My bike's drag racing lock-up clutch had spacer washers for just that purpose.

 

[Crazeewelder]

Maybe you’re more knowledgeable on Belleville washers than many of us, I’m only sharing the information given to me from Colchester M T S.
If you have any configuration/settings that work on both the leadscrew and saddle drive of the M300 please share it with us, I’d really appreciate the help.

 

[scottmk1]

I will have a look later and see if I can work out the equivalent spring stiffness which will then tell us what compression is required on the springs to obtain the correct force.

 

[Crazeewelder]

I will have a look later and see if I can work out the equivalent spring stiffness which will then tell us what compression is required on the springs to obtain the correct force.

The difficulty is working out the rotational force of 800-1200lb and transferring that into compression of the Belleville washers.
May the force be with you Scott

 

[scottmk1]

You probably have to factor in the coefficient of friction of the spring/clutch assembly to figure out the torque on the shaft.

 

[Crazeewelder]

You probably have to factor in the coefficient of friction of the spring/clutch assembly to figure out the torque on the shaft.

Good luck Scott

 

[Pete.]

Maybe you’re more knowledgeable on Belleville washers than many of us, I’m only sharing the information given to me from Colchester M T S.
If you have any configuration/settings that work on both the leadscrew and saddle drive of the M300 please share it with us, I’d really appreciate the help.

I don't have any particular knowledge on those lathes but I do know the process for setting spring pressure. If you have a target load to hit you need to assemble the stack and compress it in a spring tester until you hit your target then measure the stack height. If there's an adjusting mechanism like a nut you can adjust the stack height with that or if not you can adjust it by adding washers.

Personally I would just fit it up with the number of washers they say to use then do some test cutting and see if it slips.

 

[scottmk1]

Pete, the stack can be adjusted by means nut to add compression. By knowing the spring rate and arrangement of the stack you can calculate the required amount of compression. Obviously knowing the pitch of thread on the nut you can determine the amount of turns required on the nut to get the correct compression. That's all axial forces, so it would then need translating into torque on the shaft.

 

[scottmk1]

@Crazeewelder are you able to measure the disc springs? The dimensions in the M300 manual seem to refer to wavy type preload washers rather than Belleville washers.

 

[Crazeewelder]

@Crazeewelder are you able to measure the disc springs? The dimensions in the M300 manual seem to refer to wavy type preload washers rather than Belleville washers.

Yes, I’ll measure one for you tomorrow as I have a few spares, because the previous owner decided he wanted 20 in the leadscrew instead of 16?