Workshop assets – Page 7 – Woody's Workshop

October 30, 2020October 30, 2020

Tormach PCNC440 Oiler Replacement

I have never been over the moon comfortable with the manual slideway oiler as supplied with my Tormach PCNC440. It has a hand pump that you pump once or twice and this fills a cylinder with oil. Inside the cylinder is a piston that empties the cylinder under pressure from a compressed spring. There are two O rings, one on the piston and one on the cylinder access end cap.

original Tormach manual oiler — Original Tormach manual oiler

In the course of my ownership of the 440 I have had to replace the O ring on the cylinder a number of times. Once replaced the device works for a limited time and then fails again. The problem is made worse in that I can never find the right size O rings in the UK and have to resort to replacements from Tormach. These are not expensive but when added to carriage costs from the US it does become an issue.

In frustration at the latest failure I found and bought in an alternative manual pump on Amazon. The action is slightly different in that pulling the pump handle action generates the pressure to feed the oil rather than leaving it to the spring return action. When the handle is released, the cylinder refills itself.

Replacement oiler as found on Amazon — Replacement oiler which is available from a number of suppliers including Amazon

Physically the replacement device is slightly larger and I needed to make an adapter plate to fit it in the same position on the rear of the 440. The new device also has twin output feeds. This allowed me to replace the existing T splitter assembly with two separate feeds – one to the X and Y oil distribution manifold and one to the Z manifold.

Replacement oiler in place on the rear of the PCNC440

So far so good and it seems to push the oil out to all oiling points. Clearly this is something that has to be monitored or there is the danger of dry slideways and dry ball screws damaging the mill operation. I will report how the new style oiler performs longer term.

It has got me thinking that maybe using an Arduino I could create a ‘time to pump’ prompt beep at switch on and say after 4 hours of operation … a rainy day job ?

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October 23, 2020

BK3 Burgess Bandsaw motor drive shaft pulley replacement

A Potential JSN Job with a Hidden Benefit

Since publishing details of the blade guide modifications on the Burgess BK3 bandsaw I have received a lot of interest and also a request for a replacement motor shaft pulley and a replacement blade drive pulley.

After dismantling my machine to check the dimensional details I discovered that the red plastic motor shaft drive pulley on my BK3 was severely worn to the extent of the teeth looking very distorted. (See image below). It would appear I need a new pulley also.

For those not familiar with the BK3 genre, the red drive wheel is a sliding fit on the motor shaft and has a helical slot in the end which locates into a cross pin through the motor shaft. The gear wheel is forced tight into the slot by virtue of the direction of rotation during cutting. Reading the handbook for the BK3 it seems that this pulley is designed to slide off to allow it to be swopped with an eccentric pulley mechanism when the BK3 is used as a fret saw.

The drive belt on the BK3 is 9mm wide and 5mm pitch (with 102 teeth). The red pulley has teeth extending axially over 25mm. This is to allow the one pulley on the motor shaft to drive two different pulley diameters on the blade drive pulley with only a change in belt length. This gives two blade speeds of 106m/min and 396m/min. My BK3 never had the second pulley combination when I bought it second hand. The BK3 is a well thought out machine and despite its vintage is very popular and commands relatively high prices on EBay etc.

Back to the plot.

My first instinct was to 3D print a replacement red pulley and this was successfully done using the Fusion 360 gear wheel design script. Rather than trying to model the helical slot I opted for a simpler solution of a pair of diametrically opposite ‘L’ slots. This worked well as a concept when trialled on the 3D printed version.

Rather than ship a PLA version to the client I opted to modify a standard off the shelf 14 tooth x 25mm wide x 5mm pitch pulley. These are available from Bearing Boys (14-5M-25). The one slight problem is that the boss on the pulley needs to be drilled out to 9.5mm to match the BK3 motor shaft. This does not leave a lot of meat on the boss. To get the best possible strength from such a modification I opted for a steel pulley rather than aluminium.

First operation is to drill out the centre bore of the pulley. The motor shaft appears to be 3/8″ (0.375″ or 9.5mm ish). I incrementally drilled the centre bore upwards from 5.5mm to 9.5mm but the pulley was still reluctant to slide onto the motor shaft. Not having an adjustable reamer I ended up using a letter ‘V’ drill to get a closer fit and then a light skim with a boring bar. After the shaft had been cleaned this combination gave a nice sliding fit

The red plastic pulley had a tooth width of 25mm. The teeth on the bought in steel pulley are wider (~28mm). The red pulley only has the single outside belt retaining collar. On this basis I gripped the boss end of the pulley in a collet and turned back the teeth width by 3mm. Note there is one slight problem. The belt retaining collars are not an integral part of the steel pulley casting but a thin dished additional fitment. The result is that at some point in the turning this fitment starts to rotate independently of the pulley body and I had to use the Dremel to cut this residual ring free before I could continue.

Having reduced the teeth width to 25mm, the ‘L’ slots need to be cut. I cross drilled the pulley boss with a 3.5mm hole. I then rotated the pulley in the mill jaws by a few degrees and then cut a diametric 3.5mm slot axially down to the same level as the 3.5mm hole and then hand filed the break through from the slot into the hole to create a retaining notch. The pulley bore was then cleared of any induced burrs.

The pulley now pushes onto the shaft and with a twist anticlockwise, the shaft cross pin locates into the ‘L’ slot notch.

BK3 motor drive pulley replacement — Top image is a dimensional sketch of modifications to the standard off the shelf pulley. Lower image shows the new black pulley with a ‘L’ locking slot and the original red pulley. Note the wear on the original pulley and the helical locking slot.

So far so good. Next job is to recreate the large drive wheel pulley.

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September 8, 2020April 16, 2021

Burgess BK3 Bandsaw Disaster and Repair

Some pieces of workshop equipment generate a sentimental attraction that is hard to break. One such piece of kit is my Burgess BK3 bandsaw which is ancient but has up to now worked reasonably well for my needs. I bought it on EBay from an owner in Lancashire and remember a nice day trip to collect it.

It is a very useful machine and gets pressed into use day in and day out. That is until the other day when the blade came off with a loud twang. On inspection the drive wheel had lost part of its blade outer retaining flange. It appeared to be very old brittle plastic and the damage was really to be expected given the vintage of the device.

After head scratching I designed a replacement edging strip in Fusion 360 which I 3D printed and glued in place. Fingers crossed that will give the machine a reprieve and extend its life.

In the course of looking for possible spares (no chance) I came across a reference to modifications to the BK3 in Model Engineer to improve the blade tracking and speed settings. Here is a link to the articles burgessbandsaw2. I am indebted to the members of my local model engineering club who came up trumps with copies of these articles for me.

The guide modification consisted of replacing the two stud guides with ball bearings. While the machine was in pieces it seemed like a good idea to implement this modification. The Fusion 360 3D model is shown below. The blade is sandwiched between the two ball races and these can be slid in and out and then be fixed in place with the cap head screws once the correct location is found to guide the blade.

I drew the replacement guide block assembly in Fusion 360 and milled it on the Tormach CNC from brass. The 1/2″ bearings came from BearingBoys.

All is now re-assembled and running really smoothly. The blade prefers to run in straight lines which is a revelation.

Update : Since this blog entry I have made other modifications to my BK3 and these are contained in this link BK3 Modifications v2.

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September 8, 2020January 21, 2022

Clough42 Electronic Leadscrew Project Implementation Notes

I have been avidly watching Clough42 on YouTube. James comes over as a really nice guy and his presentation of his projects is excellent.

My principle interest is the Electronic Leadscrew modification to lathes. When installed this removes all the hassle of gearboxes and look up tables to be able to cut both Imperial and Metric screw threads and to set X axis movement feed rates.

The concept is simple but his implementation is second to none. A rotary encoder is fitted to the spindle to count revolutions of the chuck and a stepper motor (or servo hybrid) controls the rotation of the leadscrew. The resulting feed speed is derived from look up tables. The whole installation is controlled by a Texas Instruments LaunchPad C2000 microcontroller development board.

I have documented how I implemented this on my Myford Super 7 Big Bore lathe and the pdf can be downloaded below. There is also a ZIP file of all the Fusion related models for either CNC or 3D printing.

Electronic Leadscrew on Myford Super 7

Minor edits added to v3 relating to programming the servo controller

Electronic Leadscrew on Myford Super 7 v3

Electronic Leadscrew Fusion 360 Files

Updates : –

Painted control panel for Clough42 Electronic Leadscrew — Finally got the Clough42 Electronic Leadscrew control panel box painted and rather pleased with the result.

Since installing the ELS I have incorporated thrust bearings on the leadscrew mounting. This impacts on the coupling to the stepper motor.

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July 30, 2020April 23, 2023

3DConnexions Spacemouse joins the workshop

To date I have used Fusion 360 with just a mouse for screen manipulation. Over the past few months I seem to have developed Carpal Tunnel Syndrome in my right hand. (But there again it could just be old age taking its toll). This is painful at times but does depend on what activity I am undertaking. Some days just using a screwdriver can be taxing. I have begun wearing an elasticated wrist and thumb support which seems to have helped. While watching one of my many favourite Youtubers mention was made of the big improvement in 3D image manipulation that can be achieved with a 3D mouse. There is also some evidence that such a device does ease the strain on the wrist. It seems there is one major player in the market and that is 3DConnexion. I went through my previously published decision making process on a potential purchase and my Wireless Spacemouse arrived yesterday.

It is supplied with a soft storage pouch and there is a training course app with it which is straightforward. You can then play a quiz to see how good your hand / eye coordination is. Perhaps it is not good to dwell on the results of this …. Initially it is certainly weird to use but then it seems to click (?) with brain and muscle memory and then becomes a major step forward when using Fusion 360. You use your left hand on the Spacemouse and the right hand for normal mouse activity. I like it. In fact I like it a lot and wonder why I hadn’t latched onto it before now. Hopefully it will ease the strain on my right wrist and probably pass the burden to my left wrist …. arthritis rules. Similar or related subjects : –