Power Hacksaw refurb

[Charles Lamont]

I am afraid setting the scene seems to have needed a rather long introduction.

In 2007 I bought this power hacksaw on Ebay for £75, plus a 3 or 4 hour round trip with a borrowed trailer. It is a Qualters & Smith Sawmaster 150, sometimes labelled 'Terrier'.

It came with a 3-phase motor with a plate that was beyond deciphering. It would need a single phase motor and, not being needed for the projects in hand, it was pushed into a corner and used as a shelf, with a bit of head scratching and tatting about now and then until I made time for a more determined go at it.

In early 2018 I stripped it down. Several parts were cleaned, rubbed down and painted. However, after an hour or two of work with a wire brush in the angle grinder, I decided that if the main body and side cover panels were ever going to be repainted, someone else was going to shot blast them for me first. Although the saw was generally in pretty good condition, with little evidence of ham-fisted use round the vice, for example, the dovetail slide for the saw bow was badly worn and had obviously not seen much lubrication.

I was able to scrounge use of a big Herbert vertical mill to re-machine the dovetail on the main slide casting which sits inside the fabricated arm. The mating slides on the bow are steel bars and these were filed and scraped to fit, removing a considerable amount of curvature.

At this time I bought a new 1450 rpm 1ph motor, and made some adaptor bars to fit it to the existing mounting slots in the base plate. When the saw was reassembled and switched on it was obvious that it was running too fast. The original motor must have been a slower, 6-pole job. The saw got pushed back into its corner while I had a think. I had observed that, at 9-1/2" diameter, the countershaft pulley might fit in the gap bed of the Myford. Hmm.

Now, building a Quorn uses a fair amount of steel bar stock, some of it in diameters that are a bit big for either hand sawing or parting off comfortably, so I decided it is the right time to have another look at the power saw.

Well, it turns out the pulley will fit in the lathe, but only just. In the photo it is just resting on a packing piece. The plan is to turn the big A-section pulley sheave down to take a J-section Poly-V belt, and to make a new steel motor pulley about half the outside diameter of the original alloy one. But there is no way the topside will reach a tool far enough to the left to get at it.

After staring at it a few times, it dawned on me that I could perhaps reduce the secondary driving pulley as well, enough to pass over the cross slide. That would give much better access to the sheave next to the faceplate. It would also contribute to reducing the speed of the saw. However, it would mean reducing the diameter to no more than 4-1/8" OD. Some study of various belting sources indicated that while that was below the minimum recommended diameter for the original B-section wrapped V-belt, a BX-section, cogged, raw-edged belt uses the same groove profile and the minimum pulley is 90mm. I worked out the new lengths and ratios and checked belt availability. Belts are readily available and the resulting speed would be just over 100rpm.

Looks as though it is a goer.             

[propforward]

Excellent! I love the detailed intro - slways good to see a hood machine being brought back online - and modified to suit the user. Inventive approach! I will certainly enjoy the progress.

[Charles Lamont]

The first, easy, job was to re-drill the motor mounting adaptor pieces again (yes, re-drill again) to suit the smaller width of the new motor pulley.

Next up was drilling the big countershaft pulley for some bolts to fix it to the faceplate. Working at the edge of my shop's capabilities, as is so often the case with this kind of job, I was able to grip just enough of my longest slot-drill's shank to make a spotface so the drill would not wander off down the conical surface.

This setup involved a piece of quite impressive idiocy. I checked I had plenty of Y movement of the saddle to drill the holes on a 6" PCD fore and aft. However, twiddling the handle and counting turns for the front hole I was actually surprised when it stopped part way. The bit of the pulley overhanging the rear of the table had encountered the column. Fool. After completing the hole in the photo I put stops in the front T-slot against the rim either side so that I could use the already drilled hole opposite to line up a 180° rotation of the pulley. If I had thought about it properly, there would have been just enough room to do all the holes in one go by working on the diagonals. Anyway, problem solved. The holes have been tapped and the face cleaned up ready for mounting on the faceplate.

Meanwhile, with the lathe already covered in steel swarf and cutting oil, I decided I would make the motor pulley before cleaning down to a dry machine for a cast-iron session.

[Roger B]

A nice tool to rebuild       

It looks like you are entering my area or stretching your machines as far as you can   

[Charles Lamont]

Here is the motor, wearing it's newly minted pulley, with the old one and the countershaft pulley, which has some packing pieces glued onto the face so that I can machine it (hopefully) without nurgling the faceplate. The lathe is cleaned down ready, and the new secondary belt is on its way. The primary belt can wait until I can measure things in situ.

[Charles Lamont]

The gap end of the lathe bed shears are as-cast and not square across. I had to file a lump off the front of the front shear to get the pulley into the gap, now that it has packers in place.

Clocking up was rather trying and I let it go at a couple of thou TIR, measured on the OD and in the bore. Most jobs I would try for better than that.

Turning down the B-section sheave at the outer end was easy enough, though with a 1-1/8" reduction in diameter, there was quite a lot of metal to be turned into swarf. The new BX section belt has arrived and fits nicely into the groove. I did not know, before starting this job, that pulleys for nominally 40° v-belts are machined at 38°, unless they are smallish in diameter like this one, in which case they are grooved at 34°.

Machining away the A-section sheave next to the faceplate was not so easy, involving juggling tools and toolholders at the extremes of topslide reach. I even considered gaining an 1/8" by taking the felt wiper holder off the front of the saddle, but eventually managed without.

The polly-V grooves were a pain. They ended up not entirely free of chatter marks, even though it was all done in bottom back-gear (nominally 25 rpm) and sometimes with the VFD wound down to minimum, giving just 5 rpm. The pulley is large, the amount of work the saw will have to do small, the belt lightly loaded and slow running, so I do not expect belt trouble even with slightly dodgy grooves. In fact it would probably have been perfectly happy without any grooves in this pulley.   

[Charles Lamont]

The secondary belt drive is now all assembled and the belt tensioned. The pulley support bracket ended up in more-or-less the same place as before.

There is plenty of lattitude in the position of the motor. I have placed it where I would like it to end up, measured the centre distance, arrived at a belt length, and ordered one.

I found the bow was loose on its slide, so I adjusted the gib. It now slides pretty smoothly by hand without play. I filled the wick-feed oil reservoir with slideway oil, and replaced the wrist pin.

I was a bit concerned about the next job. The hydraulic drop control worked when I got the saw. As of this morning, not. Some web research gave me an idea how it works. I disconnected the top end and unbolted the lid to have a look inside. Unable to see any oil in it, I was encouraged. A plate on the machine says to use "Century PWLL" for oil points, slide reservoir and hydraulics. Century (and Silkolene and Royal Snowdrift) are now part of Fuchs, with UK headquarters on the old Walkers/Century Oils site in Hanley. I sent them an email enquiry at lunchtime, but unsurprisingly have yet to receive a reply.

Meanwhile I decided to fill it slowly with light hydraulic oil (as used for the Myford spindle). There is what seems to be a level plug half way up the cylinder barrel, but after filling until oil came out of the hole, I had to put a lot more oil in (after replacing the plug) before anything happened. Eventualy the ram met some resistance, with gurgling and slurping as I pulled and pushed the ram up and down. More oil, more resistance. It is now working as it should. It remains to be seen if the return stroke lifting function works when running.

I want to fit a proper contactor/overload and push buttons. These and their boxes are all to hand. I just need to decide where to put them.  I have not decided whether to replace the missing limit switch that stops the saw once it is through the workpiece.       

[cvairwerks]

Charles: I would definitely replace the limit switch.

[Charles Lamont]

The Poly-V belt for the primary drive arrived today, as well as some crimp terminals. I did not get to it until late afternoon, but I wired the motor temporarily, fitted it, and switched on. It works.

A nice sedate speed of about 85 cutting strokes a minute, rocking slightly on its castors, and once a little grease was applied to the countershaft, by far the loudest sound is from the motor. The back-stroke relief and hydraulic feed is working as it should. I have not tried cutting anything yet.

The next job will be to fit the new switchgear. I did buy a limit switch.

[gerritv]

That will be as satisfying to watch as a shaper.

Gerrit

[cvairwerks]

That will be as satisfying to watch as a shaper.

Or a big hydraulic planer....

[samc88]

That will be as satisfying to watch as a shaper.

Gerrit

I can confirm, I love watching my rapidor doing its thing. For such a simple mechanism it is mesmerizing to watch working