Micrometer Stop for PM 1236T 1340GT 1440GT

[mksj]

These three QMT models share the same micrometer stop, unfortunately like so many items these days the micrometer stops are on back order. I have made several of these micrometer stops in various different iterations for different individuals so they could use one of my proximity stop systems and didn't have to wait several months to wait for stock to replenish. The stock micrometer uses a barrel that extends beyond the stop, so make it a bit difficult to use if you need to work close to the headstoock, and also the micrometer shaft rotates as you advance the shaft. I just finished a more recent micrometer stop for a 1340GT owner, that uses a center thumb wheel which advances a partially threaded shaft, the shaft is slotted and uses a fixing Allen screw to prevent rotation. I make the body out of aluminum, it is easy to work with, but it could also be made out of some type of cast iron block. Most of the parts are not to difficult to fabricate, but one needs to figure out the sequencing of the steps. In this case the shaft and thumb wheel were made out of O1 rod, the base is some 1/2" steel bar that I had in my stock. Pictures and and some dimensions are posted, I made a few mods to the layout, I would verify dimensions to your lathe. This will not fit larger 1340/1440 lathes such as the ERL/TRL/RML types.

Basic parts, body, thumb wheel, shaft, base plate, hardware and I have a proximity sensor mounting plate for this version otherwise the shaft would have a flat end.

I used a rotary table to scribe the increment marks, major 0.01" increments are 0.25"x0.15" deep, minor 0.05" increments 0.15"x0.1", ticks 0.001' increments 0.1"x0.1".

Assembled micrometer stop, total travel is ~1", the slot for the thumb wheel is milled after making the thumb wheel, the fit is withing a few 1/10,00". The thumb wheel was hand tapped with a tailstock guide before parting off, the micrometer shaft was threaded on the lathe for a close tolerance fit to the thumb wheel.

Previous version I made several months ago which was modeled off of the original.

Previous micrometer I built for my 1340GT with a steel shaft and threaded steel insert.

 

[parshal]

I have the version on the left. I find I have to pull it off the lathe if I'm working close to the headstock. I love the new version!

 

[mattthemuppet2]

very pretty! I like the Mit and Starrett micrometer heads for carriage stops - you just have to make the clamp and the heads are often available for reasonable money on Amazon. That wouldn't work as well for your proximity stop, but another option to think about.

 

[mksj]

I had a few requests for custom micrometer stops for different lathes, A S&B 1024, PM-1236, 1240GT and a 1440GT, the S&B is similar to a Monarch 10EE so a larger version customized to the lathe bed rail. In these builds I made a few modifications, and decided to machine the bodies out of 7075.

Facing the rough stock with a 4" face cutter at around 3000 RPM at 10IPM, once the stock was sized the individual blocks were cut on a bandsaw and then finished with the face cutter.

The side relief was done with a 7/8" rougher just shy of 0.7" depth and 0.3" DOC per pass and then finished dimensions were done with a 1/2 end mill. The blocks were then angled to 45 degree to cut the V cut for the lathe bed rail.

Rough cutting the V

Cutting the relief

Rough notching for the adjustment wheel

Finishing and sizing to for the adjustment wheel until it just fit in the notch

Body holes and indicator line

Auto power tapping threads

Hardware modification and assembly

Finished set of stops in different configurations

Attached is the updated drawings for the PM-1236, 1340GT and 1440GT. You may need to adjust the bottom height a few thousandth as there seems to be some variation on the machines from the foot to the top of the V.

 

[davidpbest]

Looking great Mark. Having made one of there myself I know what a lot of work it is. Sure hope that the people who get them are grateful for your efforts.

The high helix rougher end mill caught my eye. How does it perform in 7000 aluminum and what is it specifically?

 

[ArmyDoc]

Beautiful work.

 

[zjtr10]

Great job on documentation and execution!!!
Thanks for sharing the information.

 

[mksj]

Hi David,

I have several HSS/CO Niagara rougher endmills, the one I use most frequently is a large 5Fl fine 7/8" and can make a pile of swarf very quickly. It is very rigid and one can take to a full depth edge climb cut with a lateral 0.3" DOC into the material. On finishing I use a high helix 1/2" 3Fl carbide for aluminum. Slotting the thumb wheel I started with the 5/8" rougher for the bulk of material removal, in 7075 you need to clear the chips, climb cut with continuous feed. Since you are taking a full width 5/8" cut when slotting with the rougher I had to cut down in 0.4" increments. The 7075 machines very nicely and is noticeable harder then 6061. The finishes are from the cutters with some light polishing and no sanding. I use the green painters tape to protect the finishes until I am done. I like the thumb wheel design mid-body and they operate very smoothly with no play. Yep, a lot of work as you well know.
Mark