Startrite 175/275 screw threads and fence bars?

[sploo]

I've just taken delivery of an old Startrite 275 table saw and I'm trying to work out some of the threads used on the machine. I'd guess it dates from the early/mid 1980s; given that it has the straight blade height and tilt adjustment bars (each with two handles), rather than handwheels.

On the top of the fence there is a set of tapped holes, and I'm pretty sure they're 3/8" 16 TPI. Whether it's BSW or UNC I'm not sure.

The side of the fence has two smaller tapped holes (for attaching a sacrificial wood fence). A 1/4" 20 TPI UNC screw is too large/coarse, so I'm not sure what that one is.

Finally, the round bars on which the fence runs have female threads (to attach the "stick mike" bar extensions). It looks to be around 12mm, but definitely isn't M12. On the left end of the front rail there's a male thread, which I don't think is original (it looks as though someone's screwed in a bit of threaded rod). It appears to be around 14 TPI (thread pitch of 1.825mm). That could be a red herring, and maybe someone's jammed some random bit of rod into one end at some point, as I can't get it to come out.

So - could any knowledgeable soul give a child of the metric age some hints as to which set of hog's heads, fathoms, and ounces they used for the threads on this saw?

 

[sploo]

For context; this is what the left end of the front fence bar looks like:

The DS version of the saw (with the sliding table) appears to have a male stub at the end of the fence bar, but it's not threaded, and the bar is flush with the left side of the main cast iron table. This bar extends further out, so I'm pretty certain it's not a DS fence bar. It also has the female recess (approx 3/4" diameter) at the end, so surely someone's just jammed a bit of threaded rod in it?

The bolt I'm holding next to it is an M12, which is effectively about 14.5 TPI (so a little finer thread).

 

[Trevanion]

On the top of the fence there is a set of tapped holes, and I'm pretty sure they're 3/8" 16 TPI. Whether it's BSW or UNC I'm not sure.

More than likely UNC, Machines have to be pretty old before you encounter Whitworth.

The side of the fence has two smaller tapped holes (for attaching a sacrificial wood fence). A 1/4" 20 TPI UNC screw is too large/coarse, so I'm not sure what that one is.

Could be a 1/4 x 28 UNF thread but could also be a 0-BA thread, You do encounter them on some of the startrite kit.

Finally, the round bars on which the fence runs have female threads (to attach the "stick mike" bar extensions). It looks to be around 12mm, but definitely isn't M12. On the left end of the front rail there's a male thread, which I don't think is original (it looks as though someone's screwed in a bit of threaded rod). It appears to be around 14 TPI (thread pitch of 1.825mm). That could be a red herring, and maybe someone's jammed some random bit of rod into one end at some point, as I can't get it to come out.

Perhaps a 1/2 x 13 UNC, not certain though.

So - could any knowledgeable soul give a child of the metric age some hints as to which set of hog's heads, fathoms, and ounces they used for the threads on this saw?

The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it.

But in all seriousness, the only reason I know ANYTHING about Imperial and English threads is through old machinery. Being also a child of the metric age (21) they didn't really teach us anything about your inches and fractions in school which kinda sucks.

 

[sploo]

Thanks. I did wonder if the fence bars might be 1/2 x 13 (and someone's jammed some odd bit of rod in it). I guess I'll have to buy a few screws to test.

I don't really have a problem with non-metric standards; I just wish there was *a* non-metric standard. Trying to fix up old machinery (and old hand tools) is often an exercise in guessing which standard was used (and in some cases, which no-longer-in-existence thread standard)!

 

[sploo]

Perhaps a 1/2 x 13 UNC, not certain though.

I've ordered a variety of bolts to check, but last night I remembered I'd got a 1/2 x 13 UNC die cutter. Lacking any suitable metal stock I (badly) put a thread on a piece of HDPE plastic. It did seem to screw into the ends of the fence bars without complaint, and held well, so it does look promising.

I have (yesterday) emailed both A.L.T saws and machinespares.net regarding purchasing parts, but so far haven't had any response.

 

[sploo]

Back to square one... it's definitely not 1/2" x 13 TPI UNC. I got some suitable bolts, but they only go in a couple of turns before there's lots of resistance - just like an M12 (with a 1.75mm pitch).

Looking inside the ends of the fence bars, the thread might be slightly finer, but I don't think it's 1/2" x 20 TPI UNF. There's also the 1.25 and 1.5mm pitch versions of M12, but as everything else on the saw appears to be Imperial I'm unsure.

I'm at a bit of a loss. If anyone has the extensions I'd be very grateful if they could measure the external diameter and pitch of the thread. EDIT: Maybe BSF? 1/2" x 16TPI?

Worse, I tried to remove the threaded rod that's stuck in the left end of the front bar. Freezer spray didn't work. Even drilling a hole through the shaft to get a tommy bar in it for extra torque didn't work. In the end I started drilling it out. Judging by the fact the drill bit met free space after a while I don't think it's even engaged in the hole that far, but it's properly jammed in. I still don't know what thread it is (well, was). Externally it's about 11.8mm - the same as an M12 bolt I have, but the pitch is about 1.8375mm (13.8TPI). Beats me what that is.

 

[Trevanion]

Maybe BSF? 1/2" x 16TPI?

Really hard to say. What you need is a couple of 60 degree and 55degree centre gauges so you can tell the difference between Standard and Whitworth.

I'd probably put my money on a slightly finer pitch M12.

 

[AndyT]

Rather than trying to match an unusual thread, would it be possible to cut off the studs and drill out+tap the sockets, to take M14?
I'm guessing you want a usable saw, not an "authentic" restoration.

 

[sploo]

I could, but ideally I'd like to be able to use the standard Startrite extension bars.

That said, I think I may end up having to completely drill out the stud on the front left end as even with significant material removed I still can't extract it.

 

[MikeJhn]

On really stubborn studs I found a sharp tap on the end loosens the grit and rubbish in the threads to allow extraction, may be worth a try.

Oh and a liberal coat of WD40.

Mike

 

[deema]

I’ve worked on a few Startrite saws and found that for the older saws most threads seem to work with BSF. They may be BSP but I’ve used BSF to both chase threads and tap out when they’ve been filled with crud / misthreaded some point in their history.

 

[Distinterior]

I've also worked on a few Startrite saws and was told by ALT Saws that all the threads were BSW on their early machines with a few BA threads on some of the really small bolts etc.....apart from some of the motor mounting bolts that were Metric as Startrite didnt make the motors themselves. Startrite did start using Metric threads on their later machines, but as to what date that was, I cant shed any light on it.

I have rebuilt 2 x TA145 saws and all the threads on that were BSW, apart from the motor bolts.

 

[sploo]

Distinterior, Deema - many thanks. It is indeed BSW. I received a couple of short lengths of BSW and BSF threaded rod this morning, and the 1/2" BSW (12TPI) is the one. That's great news as it's something I can obviously get a tap for in order to fix the damaged bar.

MikeJhn - unfortunately I've tried penetrating oil, freezer spray to shock it, and even drilling it out. I still don't know what the thread is that someone bodged in (approx 14 TPI) but as I now know the hole was 12 TPI BSW it's probably mashed the internal thread in the bar and certainly isn't going anywhere.

 

[MikeJhn]

There's always something like this available: https://www.google.fr/search?q=stepped+ ... MgAZO_w0zM: drill out re-tap and insert.

Mike

 

[Trevanion]

It is indeed BSW.

That's surprised me then. I wouldn't have thought that on a fairly recent piece of kit that they would use BSW.

 

[Distinterior]

Sploo,
Do you have any pictures of your saw that you can post up...? Also a picture of the serial number plate as that should help with dating the saw.

My understanding is, all the Startrite machines were serial numbered as they were made. It didn't matter which model of saw, bandsaw, extractor, pillar drill etc, they were given the next serial number on the list.

I have a relatively early TA145 that is awaiting restoration that has a 3 digit serial number. My guess is it is from the late 50's or early 60's. Your saw may well be earlier than you think.

As you can see, this saw is number 637 off the production line.

 

[sploo]

There's always something like this available: https://www.google.fr/search?q=stepped+ ... MgAZO_w0zM: drill out re-tap and insert.

Mike

Not seen those before (very useful to know they exist) but I need to end up with a female tapped hole, rather than a male stud, so it's just a drilling, filling, and tapping job.

 

[sploo]

Sploo,
Do you have any pictures of your saw that you can post up...? Also a picture of the serial number plate as that should help with dating the saw.

My understanding is, all the Startrite machines were serial numbered as they were made. It didn't matter which model of saw, bandsaw, extractor, pillar drill etc, they were given the next serial number on the list.

I have a relatively early TA145 that is awaiting restoration that has a 3 digit serial number. My guess is it is from the late 50's or early 60's. Your saw may well be earlier than you think.

View attachment 20180812

As you can see, this saw is number 637 off the production line.

From memory it's around 44,000. Instead of round handwheels (with a single knob) the blade rise & fall and tilt "wheels" are straight, each with two knobs. From a bit of searching I believe that might be early 1980s.

The manual I downloaded from ALT Saws is (IRC) dated 1981, and shows the straight "wheels".

 

[sploo]

It is indeed BSW.

That's surprised me then. I wouldn't have thought that on a fairly recent piece of kit that they would use BSW.

It's all your fault for sending me in the wrong direction. It would totally have guessed otherwise :wink: (no I wouldn't)

Since starting to research this saw I've added yet another new hogsheads-and-fathoms thread standard to my brain (BA). I've lost count of just how many different imperial standards there are out there. Bonkers. Metric people, metric :wink:

 

[Distinterior]

All the manuals on that site are dated 1981.....It was probably the last time they were reprinted by Startrite. I would not assume the age of your saw by that as a reference.

If you look at anyone of those saw manuals, you will be able to see small areas have been whitened out after the individual part number details. Those whitened areas used to state the thread size where relevant for each part.