Need a small solution for a Prazi SD300 mini lathe.

[RaisedByWolves]

I aquired this machine recently and have played with it a bit and it seems very accurate. I say seems as it cuts nice and will take a heavy cut if I do my part, but the handwheel dials are for ****.

They reference no known measurement, not imperial or metric and are the exact same dial for the tailstock cross slide and saddle handwheel which all have different screw pitches. It was made extremely well in communist east Germany for export, and the only real area they missed is with these dials.

So what I'm looking for is the absolute smallest reader/scale combination that will give .0005 readout reliably.

Also I'm hoping the TouchDRO is programmable for a lathe cross slide? Ie diameter reading vs direct?

Would magnetic tape and read heads be the way to go?

 

[markba633csi]

What do you have currently in the way of measuring tools? I do a lot of one-off parts for projects and seldom use the dials on my machines but instead rely chiefly on frequent measurements with my calipers and micrometer. I have a Unimat lathe and an Atlas; the Unimat doesn't even have dials (the screws are some flavor of metric but I've never checked) and on the Atlas I sometimes use the cross slide dial although it's small and hard to read.
I've used these machines for so long I have a good feel for how they cut and can judge pretty closely when I'm at size. The lack of DRO isn't a terrible hardship, at least for me.
-Mark

 

[RaisedByWolves]

Depends on what Im making.

Im a toolmaker so I get into some weird **** sometimes.

The job that frustrated me was making a tiny pin for the gear change box on my steienl mill.

Time to fix up my old Steinel SV4 milling machine.

If anyone needs a manual for this machine you can download it here. Takes it a bit to download so be patient. https://onedrive.live.com/view.aspx?resid=FF09154D1189EB47!201 What is a Steinel mill? Mine looks like this. This is where it sits as of now. I had to drag it out of its...

www.hobby-machinist.com

I need to import more of this project over here, but Im almost done and making the pin for the feed change gearbox was frustrating as it needed to be a press fit. With that it took me three tries to get the fit I wanted, partially due to this being the first real job I put this machine through, but mainly as there is no "There" there on these dials and Im not used to that and it was a lot more dicking around than I would have preferred.


Taking a dozen spring cuts to get what I want out of our large lathe at work is no issue, but with this and the tiny pin needed it was frustrating.

The pin.


.180ish tip by .2345 by .360L with the .2345 necessary for the press fit and heat treated.

A simple 10min job took nearly an hour.

Full thread at JG. https://www.garagejournal.com/forum...nel-sv4-milling-machine.515731/#post-10147697



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[Eddyde]

Yes, Magnetic tape and read heads are the most compact and you can even get them to read down to 1 micron which will get you .00005"!

 

[Capo.]

Yes, Magnetic tape and read heads are the most compact and you can even get them to read down to 1 micron which will get you .00005"!

@RaisedByWolves, Mag tape is a great way to add a scale to your cross slide and there are examples of installations on Myfords that should be adaptable to your machine. The key to these installations is embedding the tape in the underside of the cross slide, that makes for a very compact installation on a smaller machine and avoids having the scale getting in the way either on the chuck side or the tail stock side.

There is a thread over on CDN Hobby Metal Workers about a Myford installation: Myford Embedded Cross Slide Thread. Take note of the discussion about ordering the scales/tape etc. from Ditron, don't just go to their AliEx page & click, engage them on chat for a better deal and sizing tailored to your requirements.

I've done the same thing on my Myford and it makes for a nice installation. I also added a compact glass scale for my carriage and mounted it on the back of the machine. All my scale pieces were Ditron of 1 micron resolution and of course the DRO is TouchDRO running on a Lenovo Tab10.

Yuri has a number of options for the scale adapters etc. but that is a subject for a different thread. For me the scales, scale adapters and DRO were plug and play. If you haven't, you should do your homework and read the TouchDRO site from end to end, it will answer pretty well everything you need to know.

Oh, and about your handwheel scales, could you figure out how many inch/mm they are per turn and print out a scale on paper/vinyl decal etc. and overlay them as a guide while you use the DRO for the accurate work?

Good Luck!

C

 

[RaisedByWolves]

@RaisedByWolves, Mag tape is a great way to add a scale to your cross slide and there are examples of installations on Myfords that should be adaptable to your machine. The key to these installations is embedding the tape in the underside of the cross slide, that makes for a very compact installation on a smaller machine and avoids having the scale getting in the way either on the chuck side or the tail stock side.

There is a thread over on CDN Hobby Metal Workers about a Myford installation: Myford Embedded Cross Slide Thread. Take note of the discussion about ordering the scales/tape etc. from Ditron, don't just go to their AliEx page & click, engage them on chat for a better deal and sizing tailored to your requirements.

I've done the same thing on my Myford and it makes for a nice installation. I also added a compact glass scale for my carriage and mounted it on the back of the machine. All my scale pieces were Ditron of 1 micron resolution and of course the DRO is TouchDRO running on a Lenovo Tab10.

Yuri has a number of options for the scale adapters etc. but that is a subject for a different thread. For me the scales, scale adapters and DRO were plug and play. If you haven't, you should do your homework and read the TouchDRO site from end to end, it will answer pretty well everything you need to know.

Oh, and about your handwheel scales, could you figure out how many inch/mm they are per turn and print out a scale on paper/vinyl decal etc. and overlay them as a guide while you use the DRO for the accurate work?

Good Luck!

C

Great info, Thanks!


I plan on remaking the hand wheel scales to reflect whatever the screw thread pitch is. Its something like .0023 per line as made and is not direct reading so talking 1 on the dial takes almost .005 off of the diameter. Wont be pretty for taking full revolutions, but for bumping the tool .0005 or .001 it will be fine.


Am I correct the TDRO will allow me to set it for diameter reading vs direct on the cross slide? Ie .001 on the dial will take .001 off of the diameter?

 

[Capo.]

Am I correct the TDRO will allow me to set it for diameter reading vs direct on the cross slide? Ie .001 on the dial will take .001 off of the diameter?

You are indeed correct, you can set the display to read diameter.

Lots of those goodies in the manual.

C