Member postings for Henry Rancourt

I need a new motor for my Boley Leinen 8mm lathe and my web searches have led me to thinking brushless DC motors have very good characteristics for mini lathes. Is anyone here using one on their lathes and if so, what brand?

Thanks,
henryr

Is there a variable rpm speed controller, that can be used to control watchmakers lathe ac motor, that uses a knob instead of a foot pedal?

Thanks for the reply. I was an inspector in a state of the art metrology lab in one of the largest aerospace companies from 1969 to 1974. I was just curious about accuracy of these old lathes.

Now this may be hard to believe but the Boley Leinen 8mm lathe, I've owned for 15 years has amazing, to me, spindle runout accuracy.

About 5 five years ago I measured the spindle runout, starting with a last word indicator with .001 divisions and the indicator never moved. I switched to a .0005 division dial indicator and again no movement. So I switched to a .0001 division indicator and saw very slight hard to see movement.

Since then I’ve acquired a Mahr Klein Millimess 9129 and last night I went through the .001 to .0001 indicators again and got the same results. So I set up the Mahr indicator and the pointer moved about 1um which is equal to .00004 (1um actual vale is .00003937…..). This is amazing to me or is it normal for watchmakers lathes? All my indicators are calibrated using my Mitutoyu height gage.

I had read the bazmonaut spindle replacement but missed the sliding bearing bit.

The manual shows two snap rings that rest against shim washers that rest against the inner bearing faces. Based on that it seems that the rear bearing must be a sliding fit on the spindle so it can be removed before tapping the spindle out towards the tailstock. Is that a valid assessment?

Since I have to replace the bearings I think angular contact bearings with tighter tolerances make sense. They don't cost much more than top quality tapered roller bearings.

I emailed many distributors, in the US, UK and Japan and Timken, SKF and Nachi technical support, and all told me they only make tapered roller bearings in the lowest tolerance class like 0 or K. It seems there is one company, Gamet, that makes them but cost is around $1000 for one bearing. So i'm considering using angular contact or deep groove ball bearings. My research has started.

My Prazi SD300 uses tapered roller bearing for the spindle.

I’ve spent hours over the last three days looking for tapered roller bearings with tighter than normal tolerances and didn’t find any. Timken and SKF sites list tapered roller bearings with standard and tighter tolerances but I couldn’t find any. So I spoke with their technical support people and was told that, while they list them with tighter tolerances they don’t make them but if someone ordered 1000 they might make them. I’ve also searched many bearing distributor sites, in the US, UK and Japan and even sent emails to a few and got replies that they only have standard class K or class 0 tolerances. Does anyone know where to get tapered roller bearings with tighter tolerances?

Thanks,

henryr

So after making the handles it seemed time to make a carriage lock. Here are pics and dimensioned drawings.
The round black locking pads are a very hard plastic that I tapped to accept 10-24 screws. After tapping them I put super glue around the edge of the cover and closed it so when they get screwed on to the threaded adjustment screws the cover won't pop open.

My instruction post is chopped up because site has post size limits.

Here are pics & dim. drawngs.

I designed & made locking handles 4 my prazi lathe. To make them see pics & dim. drawing in another post. File size limits have been reached.

Installation steps

1. Use M6 allen wrench to rotate M8 locking screw so assembly is firmly locked.

2. Slip handle mounting ring over locking cap screw head

3. Rotate handle to position you like

4. Secure handle to locking screw head with ¼-20 set screw with locking patch or a liquid thread locker

Optional & recommended to ensure handle won’t work lose over time

1. Lock assembly & remove handle locking set screw

2. Hold handle in position you like

3. Stick magic marker into set screw hole & make a mark on locking screw head

4. Remove handle & locking cap screw

5. File or mill small flat at mark for set screw to lock against

6. Reassemble everything & secure handle using set screw with locking patch or liquid thread locker

For tailstock spindle locking handle

1. Cut 6” long 1/4” diameter piece of aluminum rod

2. Bend rod 90 degrees so handle section is about 3 1/2” long

3. Mill M6 hex on short end

4. Put handle in vise

5. Apply epoxy inside head of locking cap screw & sides of hex on end of handle

6. Push cap screw on to handle hex & with small hammer tap cap screw so it sits firmly aligned on handle

7. Leave it in vise for epoxy to cure overnight

Thanks for the answer and it makes perfect sense. My confusion was because I took the screw names to literally. I assumed that all locking screws went through the gap such that when tightened the gap was reduced and that all the forcing screws pushed against the surface on the opposite side of the gap thus widening it. Had I checked out the screw length it would have become obvious.

I’ve owned my SD300 for about 13 years and it has always worked great. Recently I started using it more and was bugged by having to bend over the bed to get the 6M allen wrench into the right locking screw. So I decided to make handles that would stay attached to the locking screws and be very easy to reach. They are now part of the lathe and make locking/unlocking a piece of cake. So now I was bugged having to use the allen wrench for locking/unlocking the tailstock spindle so I made a handle for that task. The 6M allen wrench is now in the tool box.

But now I realized something odd. To lock the carriage its locking screw is rotated clockwise and to lock the tailstock its locking screw is rotated counter clockwise. The carriage and tailstock have always been a very good fit, with the locking screws only needing about 15 degrees of rotation to go from locked to unlocked. Does anyone, with an SD300, have the same clockwise/counter clockwise locking action

Hi Diogenes,

In my posts on lubing the step pulley I was basing my remarks on hobbymat md65 manuals I found online. Those manuals have differences in the parts list section and also don't have a detailed breakdown of the step pulley shown as part #5.

So I found my original manual that came with the Prazi SD300 I bought about 15 years ago. The parts list and schematic section has some differences from the manuals found online. Some components have a more detailed breakdown and the biggest difference is the motor and drive section. It has a detailed breakdown of the #5 step pulley and all related parts. It lists and shows two radial grooved ball bearings that go on the pulley holder shaft that the pulley rides on.

Thanks for the info. It would have been difficult to learn it has a sealed bearing without taking the pulley off its stationary shaft because the two copies of the manuals I have don't show that in the parts lists. They also don't show the snap ring.

Very interesting that your MD65 has a sealed bearing. The Hobbymat MD65 manual shows, on pages 19 and 20, their lube instructions. Maybe I'm reading it incorrectly but is looks like an arrow points to the step pulley. I would have included the manual but can't find a way to add it to this reply.

Hi all,

I have a Prazi SD300 lathe (same as Hobbymat MD65) and the manual has lube instructions. One of the components to be oiled before every use is the stepped drive pulley. That pulley has no lube fitting or oil hole but it can be taken off its stationary shaft by reducing belt tension, taking V belt off the pulley and removing a snap ring. For something that is to be lubed before each use it seems there should be a simpler way to do it. Is there an easier way to lube it?

thanks