Wadkin AGS fine fence adjust dimensions help

[deema]

I’m going to make a new fine adjuster for an AGS saw, does anyone know what the profile is that is cut into the gear? It looks to be just a straight cut, but I’d have thought it was a proper gear form. Thanks in advance.

 

[SammyQ]

Request seconded. Mine looks like a dog chewed it.

Sam

 

[J-G]

I’m going to make a new fine adjuster for an AGS saw, does anyone know what the profile is that is cut into the gear? It looks to be just a straight cut, but I’d have thought it was a proper gear form. Thanks in advance.

Most likely to be an Involute Gear form though that is only part of the story.

To reproduce it (or get one made) you will need to know whether it is Metric or Imperial and therefore either the MOD or DP. The number of teeth (T) can of course be counted and the OD can be measured so from those dimensions you might be able to determine what you are dealing with.

I don't know the history of Wadkin but suspect that it will be an old machine and therefore Imperial so on that assumption, the DP will be given by T+2 / OD which will always be an integer ie. 4, 6, 8 ... 20, 24 ... 40 etc. so any figure you come up with can safely be assumed to be the rounded figure.

From the photo, I guess that 'T' will probably be 14 but without a scale reference I can't deduce what the OD may be.

The other dimension that can't easily be determined is the Pressure Angle but that is likely to be either 14½º or 20º with the later more likely.

As a quick guide - to satisfy your mind that your calculations are correct - If it were a 20 DP and 14 teeth then the OD would be 0.8".

 

[Droogs]

J-G, I say this most sincerely reading that, SHOWOFF

 

[SammyQ]

J - G, great starting point. Thanks!

 

[Fitzroy]

Do you have access to one or if not I can go photo mine from a bunch of angles and with a ruler for scale.

Let me know if you need me to

F.

 

[deema]

I dint have access to a ‘perfect’ example. However, I can confirm it has 14 teeth, and appears to have a diameter of 12.72mm so approximately 0.5”. That would make it 32. What’s DP? How do I determine the pressure angle?
Really appreciate the help.

 

[J-G]

I dint have access to a ‘perfect’ example. However, I can confirm it has 14 teeth, and appears to have a diameter of 12.72mm so approximately 0.5”. That would make it 32. What’s DP? How do I determine the pressure angle?
Really appreciate the help.

DP = Diametral Pitch which is the number of teeth in 1" of 'Rack'

A 'Rack' is the straight piece of toothing that a gear runs on if it is intended to change circular motion to straight line motion.

If that is what this particular mechanism does (and I suspect this to be the case) then you can determine the PA simply by measuring the Rack. If it measures 40º between the flanks then it's a 20º PA. Likewise a 14½º PA will have a 29º total flank angle on the rack. As you can tell, the difference between 29 & 40 is substantial so absolute accuracy in measuring is unlikely to be a problem.

Determining the PA from a Gear or Pinion (rather than a rack) is well beyond my pay grade!! -- if this 'gear' runs on another 'gear' rather than a rack then you'll likely need to replace both, so knowledge of the PA becomes irrelevant ie. they need to be the same.

Whoever you get to make the new part will be able to work from the information you have so you don't need to get into more detail about addendum/dedendum/CP etc.

If you are thinking of DIY ?? - - - - Then you will need to obtain a Nº7 32 DP Involute cutter of the correct PA and be able to accurately index your shaft 25.7142º cutting the 'grooves' 0.075" - the total depth. Unless you have access to a Gear Hobbing machine with a 32DP Hob - - - - I only have 20 & 40 DP 14½º PA other than my Metric Hobs.

 

[KT_NorCal]

I can measure mine tomorrow if what you are looking for is the fine adjust off the AGS10. The outer diameter as well as the parts of the shaft that the bronze "bearings" ride on will matter as well, so it engages properly with the underside of the fence bars.

 

[deema]

Thanks for the superb detail on gear cuttings, you’ve been a great help.

I really appreciate the offer to measure up your fine adjust, that would be brilliant. I’ve measured mine, but, it’s chewed up a bit so another reference would be superb. I’ve added a picture of the dimensions I measured, if you could check them with yours I’d be very grateful. The original photo was not of mine!

I know that the sintered bronze Bush is 1/2” OD which defines I think the gear diameter as the assembly will push out. The shaft is to fit the bush ID

I have the rack, which is the bar that the main fence slides on. I think I can easily see that difference in angle by eye. I’m fairly sure it’s 14.5 as originally I thought they were just cut with something like a slitting saw, which was going to be my initial approach. I will measure it and also the pitch of the teeth on the rack just to be sure.

I’m going to have a go at making up it, just need to find a reasonably priced gear cutter! I’m no machinist, but recent bought a lathe and mill so it will provide a good learning opportunity. I have mill came with both a rotary and Indexing table, so hopefully getting the angles should be OK.

 

[deema]

 

[J-G]

I’m going to have a go at making up it, just need to find a reasonably priced gear cutter! I’m no machinist, but recent bought a lathe and mill so it will provide a good learning opportunity. I have mill came with both a rotary and Indexing table, so hopefully getting the angles should be OK.

It's good to know that my assumptions are correct and that you do have the appropriate basic equipment to enable you to attempt a DIY solution.

The measurements on your drawing pretty much confirm the detail, I suspect that the 12.72mm - just larger than ½" - is due to wear which has raised a burr on the top of the teeth. The 'root' at 9.2mm is larger than I calculate (8.89mm) but that could be due to not getting the jaws of a vernier right into the bottom of the tooth. To measure gears accurately you really need a gear-tooth micrometer which measures the tooth width at the Circular Pitch line and the addendum. For a 'one-off' job not worth the hassle.

It's also possible that Wadkin used their own 'standard' to determine the dedendum. Today it is normal to use 1.4/DP for anything above 24DP and 1.25/DP below that, whereas it used to be 1.25/DP for all and that could account for the 6 thou difference.

As far as measuring the PA is concerned - - - it's a long shot - - - but if you have a 32tpi ACME tap (or thread for that matter) that will be 29º and should fit into the rack

The next thing you need to determine is whether you have a suitable dividing plate to fit the rotary dividing head or indexing table. I presume that the dividing head would be the most likely so you need a plate with 14, 28, 42 or 56 holes. You also need to know the basic ratio of the dividing head, that is how many turns equals one revolution. Regrettably, there are a number of 'standards'. I have 40:1, 60:1 and 90:1 !!

Using a 40:1 Ratio head with a 28 hole plate you would need to move the head 2 full turns plus 24 holes for each tooth. If you have to use something else and can't fathom how many turns/holes you need post the detail and I'll work it out.

I only raise these points because, although you do seem to have the equipment, the fact that you are asking the question indicates that you haven't (yet) had the practical experience.

 

[J-G]

I need to clarify my previous assertion that you need a Nº7 cutter, I've just checked general availability with RDG, Chronos & Tracey Tools and am surprised to find a lack of adherence to the 'Standard'

RDG number theirs as 1 = 135T - Rack going to 8 for 12-13T which is as I know the standard, whereas Chronos state Nº8 as 135T - Rack (hammer)

Since I use Hobs rather than Involute Cutters I haven't needed to look at this aspect previously.

Suffice to say that you need a cutter for 14-16 teeth which should be a Nº7 but the number used is secondary #-o

 

[deema]

I really appreciate your insights and guidance.

Your absolutely correct, I have my ‘L’ plates on when it comes to metal work. I completed an evening class in MIG welding just before the lock down, and have been looking for an evening course / few weeks course as opposed to a qualification in milling / turning. There doesn’t appear to be anything available where Iive near Chester.

I was very lucky when I bought the mill, which is a Bridgeford clone.....l was actually buying a brazing hearth and chatting to the chap whom I was buying it off admiring his mill. He’d loved it for a number of years and due to ill health offered to sell it to me. It’s hardly done any hours and came with a number of bits he generously gave me. This included the vertical shaper head. I’ve wondered if there is a way of making a single point tool that fits the rack it meshes with and using this to cut out the gear profile / or is there a gear hobbing cutter for a shaper.

I started life as an engineer, originally electronics but ended up mainly running mechanical orientated company’s . Not hands on the tools though! I’m loving the challenge of learning new stuff.

I’ve found a source for the cutter, I was hoping RDG would have one, but they seem to miss out the 32 No 7 and just have the 30 no7 cutter with a 14.5 PA

If I don’t have the correct hole plate, I will look to buy one if they are available for my indexing head. Looking on u-Tube, Tubalcane shows how to make one, if I can’t.

 

[deema]

The gear is chewed up, and the monkey on the ‘Very Near’ made his best efforts on the least damaged part of the gear to take a few measurements. I’m sure it will be a proper gear form, Wadkin did seem to apply good mechanical principles and design for their products to be repaired.

 

[J-G]

I was very lucky when I bought the mill, which is a Bridgeford clone.....l was actually buying a brazing hearth and chatting to the chap whom I was buying it off admiring his mill. He’d loved it for a number of years and due to ill health offered to sell it to me. It’s hardly done any hours and came with a number of bits he generously gave me. This included the vertical shaper head. I’ve wondered if there is a way of making a single point tool that fits the rack it meshes with and using this to cut out the gear profile / or is there a gear hobbing cutter for a shaper.

That would of course be a BridgePORT clone but I knew what you meant
I wish I had room for such! Naturally, it would be possible to use a single point tool in a 'shaper' head but of course the are a number of caveats. First, it wouldn't be the shape that fits the rack - well not without a great deal more control to the rotary table - effectively making the whole setup like a Fellows hobber - but you could make a single point tool which was an approximation of an involute.

I've plotted the involute curve that a 14T 32DP 14½º Gear would have and laid on that a circular curve, actually two - one at 0.25" dia. and another at 0.24" dia.

You'll see that the curve is close but not perfect, the discrepancy being forced to narrow the tooth at the root so that there would never be an issue of 'binding'. Here is a close up :

This small discrepancy would make no difference in the real world but you will also see that the 'tip' of the cutter would need to be only 0.0287" wide. If you were making the gear out of Delrin or possibly even Alum you may get away with it. I have my doubts if using even En1a.
I would certainly fight shy of tackling such a task - even if I could get anywhere near close with grinding a single point tool to these dimensions.

I started life as an engineer, originally electronics but ended up mainly running mechanical orientated company’s . Not hands on the tools though! I’m loving the challenge of learning new stuff.

I served my time as a Toolmaker (1956-1962) but left at the end of the apprenticeship to take up other interests :roll: didn't get back to engineering 'til 2003 after my 2nd divorce :lol:

I’ve found a source for the cutter, I was hoping RDG would have one, but they seem to miss out the 32 No 7 and just have the 30 no7 cutter with a 14.5 PA

RDG are simply out of stock but that may not be resolved for some time.

If I don’t have the correct hole plate, I will look to buy one if they are available for my indexing head. Looking on u-Tube, Tubalcane shows how to make one, if I can’t.

Making one is an option but 14,28 holes etc. are difficult due to the non-integer angles - not as bad as a Prime number plate of course, but if you have a 49 hole plate that would do the job using (40:1 Ratio) 2 full turns and 42 holes for 14 or 1T+21H for a 28 hole (which gives more flexibility).

 

[deema]

Wow, really appreciate you taking the time to draw out the tooth form and or die so much information.

You’ve really got me interested in this subject. I’ve been reading a little today, and I’m wondering if it’s actually M0.8. This would have a root diameter of 9.2 and a tip diameter of 12.8. I’ve re-measured the root and I’m fairly confident I’ve got that right. The OD is limited by the bite it has to fit through, so can only be 1/2”, which doesn’t fit with M0.8. However, DP32 doesn’t fit fully fit either.

I’ve measured the number of teeth on the rack, and it’s (as close as I can determine) bang on 10 teeth per inch. The rack is a little battle scarred as most are with the operator having pushed the fence with the teeth engaged from time to time over the years.

Having had a really good look at the rack, I’m now not certain that it is 14.5 PA and it could be 20. I’m finding it difficult to determine as the rack is on a round bar.

The way the rack was made is also very interesting, I can see what I think are three score marks on each slot. Is this what you get with a Hobbing cutter or some other way of cutting the rack?

 

[J-G]

Wow, really appreciate you taking the time to draw out the tooth form and or die so much information.

You’ve really got me interested in this subject. I’ve been reading a little today, and I’m wondering if it’s actually M0.8. This would have a root diameter of 9.2 and a tip diameter of 12.8. I’ve re-measured the root and I’m fairly confident I’ve got that right. The OD is limited by the bite it has to fit through, so can only be 1/2”, which doesn’t fit with M0.8. However, DP32 doesn’t fit fully fit either.

I’ve measured the number of teeth on the rack, and it’s (as close as I can determine) bang on 10 teeth per inch. The rack is a little battle scarred as most are with the operator having pushed the fence with the teeth engaged from time to time over the years.

Having had a really good look at the rack, I’m now not certain that it is 14.5 PA and it could be 20. I’m finding it difficult to determine as the rack is on a round bar.

The way the rack was made is also very interesting, I can see what I think are three score marks on each slot. Is this what you get with a Hobbing cutter or some other way of cutting the rack?

Just a quick response - I'll have to do some serious thinking with the new information - especially the 10 teeth per inch !!!

I also considered 0.8 MOD earlier today but dismissed it on account of the ½" hole.

Racks would not be cut with a Hob and hobbing would not (normally) leave the witness marks you describe.

It might make it easier to measure the PA from the rack by first brushing it with white spirit to clear any grease and then using plasticine to take an impression. Care needs to be taken and I usually leave the cast in the fridge for an hour or so before taking measurements but it has confirmed (and denied) unknown thread forms for me.

14T and 32DP does fit with ½" (12.70mm), though not with 12.72mm but if you were able to get the shaft out through the ½" hole and it IS over 12.7mm then the hole must also be oversize . . . . . . hmmmm....

 

[KT_NorCal]

Here are some better pictures. I think the one on my fence is in pretty decent condition and I'll upload the pictures at full resolution (not sure if this site will truncate them or not) so you should be able to zoom in and get a nice view of the profile.

the measurements I got were:
- The diameter of the main shaft that goes through the casting before the splines part = 9.01mm
- The diameter of the splines =12.65mm (I got a few different measurements but that seemed to be the largest)
- The diameter of the splined part as measured between the low points in the splines = 9.50mm
- Number of splines 14
- Length of splined part 20.86mm

Hope that helps

 

[KT_NorCal]

Just to clarify. This is off a saw that was listed as a 1979 AGS 10 in case these things changed over the years. Fence is the one in the picture attached (my saw).