10” Utilathe (Miss Metric) Overhaul Repair

[Susquatch]

I like using a larger forward and reverse switch wired through the VFD logic but I want to keep my oily dirty fingers off the control pad and not having to look away

There is a blank cover for what I assume would be the coolant pump - it would make for a good work light switch location.

I would have assumed that you know that many VFD's can be externally wired for switches and whatnot. So you could put a big HUGE GNARLY BEEFY switch anywhere you want and not have to look away to find that "teeny" little button elsewhere....

 

[Brent H]

Making the new cross feed nut today.

A little layout on the surface plate:

A little gold flying around:

 

[trlvn]

Newbie-level question but...how did you determine the height of the centre of the through hole?

Craig

 

[Brent H]

Hey @trlvn so I had the original, measured the root diameter for the threads (0.404” or a Y drill bit)

The distance from the top of the old nut to the inside thread was 0.625”. Basically the centre of the hole had to be 0.625 + 1/2(0.404) = 0.827”.

I set that up and scribbed the line. Then halved the width of the block (0.980/2= 0.490) and scribed that distance on the block. I used a centre punch to create a reference mark for aligning the piece in the 4 jaw chuck.

Using the centre hole scribe lines I was able to get the jaws in rough alignment - just a second and I will make some sketches.

The tap I used is a trapezoidal 1/2” x 2.5 mm pitch I bought on eBay- worked great - perfect fit.

 

[Brent H]

 

[Brent H]

I ran out to the shop and did this mock up for you as an example.

 

[Chicken lights]

Yo @Brent H

Why the three thread pitches for M10?

 

[Brent H]

Hey @Chicken lights - there are 4 actually Dave and it’s all based on the force you want the bolt to be able to apply to a given application. As the pitch reduces the more torque you can give the bolt so a 1.5 pitch can take a torque of 49.8 N-m for an M8.8 and as the pitch reduces- 1.25 (52.7 N-m), 1 (55.7 N-m) and 0.75 you can torque to 58.7 N-m.

Practically speaking it gets a bit silly as you “should” go to the next size bolt. Sometimes space is the issue and they increase the material strength or the pitch or both. It is enough to drive you nuts / hahahaha

The car I am restoring - M7 bolts in places - difficult to find. Also some silly small M5’s in a place better suited for M 8 - argh!

Miss Metric may get a work out!!

 

[Chicken lights]

Hey @Chicken lights - there are 4 actually Dave and it’s all based on the force you want the bolt to be able to apply to a given application. As the pitch reduces the more torque you can give the bolt so a 1.5 pitch can take a torque of 49.8 N-m for an M8.8 and as the pitch reduces- 1.25 (52.7 N-m), 1 (55.7 N-m) and 0.75 you can torque to 58.7 N-m.

Practically speaking it gets a bit silly as you “should” go to the next size bolt. Sometimes space is the issue and they increase the material strength or the pitch or both. It is enough to drive you nuts / hahahaha

The car I am restoring - M7 bolts in places - difficult to find. Also some silly small M5’s in a place better suited for M 8 - argh!

Miss Metric may get a work out!!

That’s silly, who has M5 or M7??

I thought it was bad enough trying to match up what M10 thread was being used. It’s “usually” m10.1.5 but man it’s hard to tell

Metric system is goofy

 

[YYCHM]

That’s silly, who has M5 or M7??

I thought it was bad enough trying to match up what M10 thread was being used. It’s “usually” m10.1.5 but man it’s hard to tell

Metric system is goofy

What does M10.1.5 stand for?

 

[Brent H]

That would be a 10 mm diameter bolt with a 1.5 mm pitch and then you have to cypher out the grading. Typical is 8.8 or 10.5 or 12.2 it’s all …. Argh!!

 

[Chicken lights]

That would be a 10 mm diameter bolt with a 1.5 mm pitch and then you have to cypher out the grading. Typical is 8.8 or 10.5 or 12.2 it’s all …. Argh!!

It makes no sense

Back to miss metric repairs please

 

[Susquatch]

The tap I used is a trapezoidal 1/2” x 2.5 mm pitch I bought on eBay- worked great - perfect fit.

So, not to be a trouble maker, but given my recent laugh at the Ali folks and your discussion about metric shenanigans above, I feel a bit awkward asking "what the heck is a 1/2 x 2.5?" Is that mixed metric and imperial, or is it a 1/2 inch mini auger with just 2.5 threads per inch?

 

[Brent H]

@Susquatch : this tap is the perfect example of why dumbass scientists and theoretical types should remain in their own “space” when you enter reality.

To “update” school learning in the big 70’s push to make Canada Metric, idiots felt the need to change lathes in school tool rooms to metric. The Metric “system” works fine for weights and other measures but drops the ball when it comes to practical “building or creating”. They sold this bill of divisions by 10 - make it all easy but then, it’s a lie. “It’s all based on decimals / no fractions- no ratios” total bull schite. Gravity is like 9.81 - not “10” thread pitch of 0.33 - yep super “10” factor So many things could have been simpler and have some scale -

So yep, the tap I needed is 0.500 inch outside diameter (plus a bit of clearance) with a 2.5 mm thread pitch with a trapezoidal profile - verses a standard Acme.

This was the way to pervert a perfectly good lathe over to a bastardized Miss Metric version and satisfying the cheap government.

I have found that to “save the old” they pinned the gear on the cross feed screw with a roll pin and re-drilled holes rather than fitting the “0” taper pin. - screws up back lash - fixing that. Noticed the same on the lead screw. Couple other mods that were poorly done to achieve sudo metrification.

Metric has its place - someday I will find out where …..

 

[Susquatch]

So yep, the tap I needed is 0.500 inch outside diameter (plus a bit of clearance) with a 2.5 mm thread pitch with a trapezoidal profile - verses a standard Acme.

Not to beat an old horse too much..... But 2.5mm is awful close to 10tpi. In fact, just under two thou (1.6 thou) per thread. Ie +/- 8 thou over an inch wide nut. Might be a pretty effective equivalent to a split nut!

Is it possible that's its actually 10 TPI and simply called 1.5 for stupid sake?

How does it work after 100 turns or so?

Assuming the Leade screw really is 2.5mm, could you get away with 10tpi on just the nut?

If not, can you thread on the lathe instead of buying a wierdo tap that will cost a fortune - if you can even find it?

I think you and I are on the same page though about the stupidity of the way the whole world was turned upside down.

You might recall that my mill/drill has a similar (the opposite) lead screw problem.

I should probably fix mine too. It's just hard to justify given that I have an awesome mill that works great.

 

[Susquatch]

Yet another thought along the same line.

Why is a metric leade screw and nut required when there is a 127 gear in the handwheel assembly? More and more I suspect that there is a metrication gremlin hiding under the skirts with a metric pen in its hand......

 

[Brent H]

@Susquatch : yes, the 10 TPI is very close but combined with the trapezoidal tooth profile and just that hair of pitch difference- not gonna fit.

I was able to get a custom tap made and delivered for $70 - took a chance on eBay and won! Yeh me!!

When the conversation happened a new feed screw was assembled into the lathe. This screw has the drive gear pinned to it with a tapered 0 pin - or let’s say that it should heave been fitted that way. The person fitting the gear did a poor job and used a roll pin in a re-drilled hole 90° offset from the original holes and not properly centred. This gear sets the allowable movement of the cross feed table relative to the feed shaft -not including the back lash that develops on the feed screw and nut. In this lathes case you could push and pull the cross feed table 0.022” back and forth.

Today I need to clamp the assembly- re-drill the gear/shaft pilot hole just a scoash and ream it for a proper #0 taper pin. After that I will make a foot levelling bolt and it’s then up to the motor.

 

[Hacker]

Hey @trlvn - yes Craig the lathe is 3 phase as I my other lathe and mill. I am essentially just using the VFD to give me the third phase and then I use the headstock in all it’s geared glory. I don’t use the VFD for any speed control. It does yield the benefit of braking - which is nice.

I like using a larger forward and reverse switch wired through the VFD logic but I want to keep my oily dirty fingers off the control pad and not having to look away from the lathe to find a small button.

The original control was interesting, a single throw three pole “light switch” allowed power to the machine, that went to a relay box with the motor starter circuit. You selected FWD or REV and then pushed the start button, push the stop to interrupt power to stop the motor. There is a blank cover for what I assume would be the coolant pump - it would make for a good work light switch location.

That is a very clever use of a three way switch. I will have to remember that!!

Nice work and thanks for the update.

 

[Brent H]

Reaming out for the taper pin. Enlarged the hole to 1/8” and made sure the gear was held tight

Reamer now through. Hammered in tight the taper pin, hacksaw’d it flush and then cleaned up with a file.

Inserted into the lathe and all is good. No cross slide play and everything turns properly.

Threaded a new 1” x 14 TPI leveller for the lathe:

Used the upside down tool bit and running in reverse as it was pretty close to the chuck for straight threading

Milled some bolt flats to give the top a 1” wrench option.

And the reproduction:

The idea is that you level out the lathe and then bore 1/2” hold downs into concrete. Insert the hood downs or ready rod into the levellers and you can then seriously bolt the lathe to the workshop floor.

 

[Susquatch]

Milled some bolt flats to give the top a 1” wrench option.

Very clever use of hexagonal collet holders! I wasn't planning to get one like that. Just changed my mind!

The idea is that you level out the lathe and then bore 1/2” hold downs into concrete. Insert the hood downs or ready rod into the levellers and you can then seriously bolt the lathe to the workshop floor.

I'm jealous. My feet are hidden inside the cabinet. I had to use paint to locate them.