No, I just eyeballed it. The point being, I'm not trying to measure the deflection, just note it, and hopefully there won't be any.Pretty cool. how did you arrive at the correct curve on the pivot lever where it acts on the dial indicator point? Was it by using gauge blocks and filing to suit?
That's exacty what I've done. Ended up with zero error in the actual gear, but a different lead to that given by the textbooks.... It would have been nice to have the two exactly the same. Do I try to work ot where the error is (by evaluating every calculation to the nth degree), or just put it down to my pinion being a small tooth count non standard barsteward?Umm, after looking at the pic again it looks like you're driving the original gear past the pointer using the table travel and DH gear train, then adjusting the lead via the gear train until the pointer shows no movement. If that's what you're doing it's very clever and should produce a perfect copy.
Don't know if it would ever be of any help but I have a 3d printer and a resin printer. If you ever needed a gear creating as a sample for you to take measurements off etc let me know.Well, it’s engaging fine, but measuring the actual angle has been one of the difficulties. And this angle is the primary input of the calculation of the lead. The other being the pitch diameter of the gear. So now I know the lead, I have a pinion that closely matches the original, and sits squarely on the (slightly imperfect) rack.
The setting of the table on the mill has no effect on the lead, but it does affect the tooth profile. If I reverse calculate the equation that gave me the (wrong) lead, do I use the original, calculated pitch diameter, and derive the angle, or do I assume the angle as measured is correct and derive a new pitch diameter?
I’m tempted to use my tool to asses the tooth angle on the rack before going further, this will hopefully give me the table set angle and I can use this to recheck the lead calculation.
Did you follow that? I’m not sure I did...
The calculated lead was 5.210, indicated 4.5 thou error. 5 iterations through slightly longer and longer leads got me to 5.357 inches lead, zero indicated error. Even though I don’t have a full set of change gears most steps were attainable. My earlier attempts at calculating lead and cutting the gear used the full diameter of the gear, so we’re miles out. Potential error points are the calculated pitch diameter and the helix angle, one calculated, one measured. I’m going to measure the rack angle with my tool, which should pin down the helix angle. Then make a piece of rack gear. The easy way out would be to make the rack to match the pinion, but I’m trying to replicate the originals.I’m lucky in that the pinion isn’t worn. The rack, being MS is certainly worn. And I have to say I’m miffed that my calculations for lead didn’t come out exactly the same as the original which I took the measurements off. I’ll get the figures when I’m down there later.
It still leaves me needing to get the correct helix angle to set the table for cutting the gear accurately, as well as the rack, which luckily I have a cutter for. (Cutting the rack will be another story, but the issues here will be accurately setting and holding the work, and accurate advancing for each tooth).
There is a fellows gear cutter just up the road from me, sitting gathering dust and rust, rather large for me though...
And yes to recutting with a dividing head, just a matter of tool and work setting, taking up backlash etc, so long as the cut isn’t too small...
Made a smaller tip for my patented tool tonight, so it can get lower down between the gear teeth on the rack, so I can measure the cut angle. Turned out to be smack on 23degrees. Next to cut a rack.The calculated lead was 5.210, indicated 4.5 thou error. 5 iterations through slightly longer and longer leads got me to 5.357 inches lead, zero indicated error. Even though I don’t have a full set of change gears most steps were attainable. My earlier attempts at calculating lead and cutting the gear used the full diameter of the gear, so we’re miles out. Potential error points are the calculated pitch diameter and the helix angle, one calculated, one measured. I’m going to measure the rack angle with my tool, which should pin down the helix angle. Then make a piece of rack gear. The easy way out would be to make the rack to match the pinion, but I’m trying to replicate the originals.
Plan is to manufacture complete rack assemblies, specifically for vintage Cooper racing cars. The first customer (freeby) is the owner of the one (worn) rack we have to replicate. These rack assemblies are unobtaneum, and the castings were originally magnesium. but we can cast them in aluminium.Great work. Is this a replacement for a worn rack or are you going to be selling these? I know of a firm in Australia making custom ratio racks for classic cars. Using the original rack body, with homemade internals. Some with power steering too, pretty cool!
These will be identical to the original (racing car racks). I'm planning not to be using anything more than drill rod (silver steel) for the pinions which I will oil quench then temper back after polishing. The issue being any distortion from this process (as well as getting the hardness right, but using a non exotic steel will surely help).For racing I expect there is a market for quicker racks too
Looks great so far. Be interested on the hardening process.
...I'm having doubts the work will pass under the universal head...
Yeah, worked out I needed a bigger cutter, not so keen on a long overhang, or a flycutter tbh.For cutting a rack, you do not necessarily need a multi-tooth cutter of the style you show. A flycutter would do it and allow you to use a larger swept diameter so the work passes under the head.
The other option is a multi-tooth cutter of larger diameter.
See:
SYMMETRICAL EQUAL ANGLE MILLING CUTTERS TO FLAT FOR HORIZONTAL MILLING MACHINE | eBay
We will always help you to have a 100% positive happy buying experience.www.ebay.co.uk
The listing has 40 degree included angle and 30 degree included angle (which might need to be reground to 29 degree). Note the available diameters - more than 3".
You can also use a longer arbor but with the plain portion of rod after the teeth, that might be so long as to be too floppy.