Member postings for Paul Fallert

To help readers, I have created an album which contains Ted Wale's Fig. 2

Neil:

Thank you for considering this problem (I'm now assuming it was never answered in Scribe-a-Line). I am a retired accountant, not an engineer so I have a lot to learn.

I am also now in the process of machining a backplate, so this issue is front and center in my thinking (although so far I don't need to make an insert). The insert would be Plan B if the threading does not go as planned.

At Fig. 2, at the point where the inner right edge of the insert intersects with the backplate in the drawing, there is only 1/4" of metal (cast iron) in the (vertical) cross section. Is that considered a "shear or stress point"?

I was trying to compare it to a spigot. If this were a spigot, 2"OD and 1-1/2"ID made of cast iron, would there be a weakness at that same point that is overcome by the insert or by the fact that this is a tube? Tubal Cain and others suggest that cast iron is much better than steel for backplates, but cast iron is supposedly not as strong in tension as steel. The other concern raised by Ted Wales was to not press the insert it into the backplate due to the possibility of cracking the cast iron.

Paul

In MEW #59, Ted Wale asked Scribe-a-Line about sizing an insert for a chuck backplate. The purpose of the insert was to afford a "second chance" at cutting the threads, which had gone askew on the first effort. Cross-section drawings were provided.

I have searched subsequent issues without success in finding a Scribe-a-Line response.

The question asked, I believe, about adequate metal to provide strength for safely supporting a lathe chuck. This question arises in other areas of model making, re-use and general repairs.

Can someone point to the answer?

Peter Smith suggested a rather clever solution to lathe swarf problem.

1) Is it a case of gravity nesting the folds of the bellows? Or is there something else not obvious to me? I have been trying this idea and the sticky slideway oil on the ways tends to stick the loose bellows rubber to the ways.

2) The large bellows piece (toward the headstock in the photo) appears to be very close to the chuck diameter.

Paul

In MEW 59 (Scribe-a-Line) Ted Wale provided a sketch of a chuck back (or mounting) plate and how to size a threaded bush. Subsequent issues (67, 69, 70) discussed the pinning options (two at 90 or 180 deg, 3 at 120 deg), but I have not been able to locate an answer to the original question about the size of the bush relative to the "boss (spigot)" in which the bush was to be secured. The spigot was 2 inches and Ted's colleagues suggested the bush be 1.5 inches, thus equalizing the wall thickness of bush and boss.

Anyone know the answer?

Paul

I have a Maximat-Compact, 1966 era. As I understand, the Austrian manufacturers were attempting to compete with/copy? the MyFord and they do bear some similarities to a MyFord. The spindle bearings are SKF tapered roller bearings. Each bearing has a grease nipple, aka Zerk fitting and the instructions say to grease every 500 hours.

Since it is not a good idea to fill the bearing/housing with grease, how would one know that the bearing/housing was 40-50% full? From correspondence with other Maximat owners, who in earlier years were able to correspond with the factory or the factory's representatives, I learned that the factory assemblers would slowly fill the bearing until grease oozed out from the rubber seal. The new owner was told that grease would come out from the seal and that the new owner should not run the spindle at higher speeds until this stopped occurring. Another tip was to feel the spindle housing and if you could not comfortably keep you fingers there, the speed should be reduced or the lathe stopped and allowed to cool.

Any thoughts or advice?

Paul

I wish to thank each of you for your thought provoking remarks.

You have certainly surfaced a number of different approaches.

I now recall (when making a follower rest for the lathe from 19 mm thick CRS) that I resorted to the use of metal cutting blades in a handheld (wood butcher-type) variable-speed jigsaw. It was slow going and I broke a blade, but it made a nice enough cut and required only a bit of hand filing to finish. Given that the 8mm (not 6mm) slot drill might not comfortably cut the total depth, the final cutout (after removing from the mill and drilling a starter hole in the slot through the piece), would be easy work for the jigsaw. Then the file would be used to clean up the rough edges.

Paul

Ah! You have provoked another thought or two. You have convinced me to avoid the drill press.

I forgot that I have a rotary table.

Might I proceed as follows on the mill?

Place a thin hard board under the plate to prevent milling the rotary table's top face. Attach the sandwich of plate and board to the rotary table (there is room for four clamps). Maybe use double faced tape.

Then use a 6 mm center cutting end mill to slowly cut a 50 mm OD channel, stopping before the cut has reached the bottom depth of the plate, to avoid a jam-up from a loose 38 mm "wheel". Remove all and punch out the 38 mm wheel from behind. Clean up with a roundish file, or use a boring head (a precision not needed in this particular case).

Certainly, a lot fewer chips. A round piece saved for future projects. Maybe less work than chain drilling and filing? No risk of a "catch" of the boring head in the hole, given that a MT2 shank is a weak point, especially on an interrupted cut.

Thank you all for your collected and stimulating thoughts !

Paul

Edited By Paul Fallert on 01/02/2014 20:05:04

Plate is ordinary black steel, but is too long for the lathe faceplate, which

was my first thought. It drills reasonably well, but it is not free-machining.

The roundness or the hole or lack of it is not critical.

I do have a 1/3 Hp floor drill press and 1/2 hp 6x24 vertical mill,

but,

My largest drill bit is 1-1/4" Silver & Deming or 1" MT2.

I first considered drilling , then using a boring head

and taking off 0.10 mm per pass. (My boring head is MT2, which matches my mill and drill press. The drill press has has sloppiness in its runout.

Is there a better method to approach this task?

ps, it's for a friend and the steel belongs to him, so I don't want to botch it.

Thanks in advance,

Paul

Thanks for the suggestions.

Instructables.com (with 500 postingst) on the subject of sugru and "oogoo" made from cheap 100% silcone purchased in tubes from a home repair materials store.

VERY interesting experiments and samples are discussed and pictured.

A bellows tube or sheet could be made from fiberclass cloth or screen and coated with oogoo.

When we construct engineering models, there are needs for rubber-like material that could be cast or formed for gaskets, plugs etc.

Instuctables.com has examples of oogoo used to make a mold and then oogoo rubber can be cast in the mold. This would be good for making multiple parts. One poster used oogoo to make a mold and low-temperature metal cast in the oogoo mold.

Paul

The simple answer is that zinc is almost 3 times heavier than aluminum.

By practicing on sample bits (by comparison), I should be able to detect which is which.

Since zinc density is close to iron, that might help with the learning process.

Once this skill is acquired, no need to have access to acids or other special equipment.

Thanks to everyone for their assistance.

Paul

Other than melting temperature, is there a quick/simple way to distinguish between zinc and aluminium?

If I throw a bit of gray metal into the melt pot and it is zinc when I was expecting that is was aluminium, the resulting casting will be spoiled.

What do others use to keep these metals separate? The alchemists must have had some simple method of testing their bits of metal.

Paul

Jason:

I easily found sugru, but not Home Brewed "ougoo". Is this the proper spelling ?

BTW, I am looking for a pourable polymer / rubber-like material that will cure in a mould (without excessive exposure to air) and can have it's hardness modified (goal = 25 Shore A).

Paul

Sir John:

Right you are. It was in MEW #131.

Tony Jeffree's article is also reproduced at:

**LINK**

Drawings there illustrate how the incremental in-feed of the hob forms the involute teeth.

1) Tony "gashes" the longitudinal cuts in the hob with a Dremel tool.

2) For smaller gears, only 3 "lands" were required. Larger gears would require more "lands".

3) In a different article, another author relieved (backed-off) the teeth with a hand file, before hardening.

Very minimalist equipment, indeed.

Paul

The URL link should have been encoded as a "Link".

**LINK**

Paul

Edited By Paul Fallert on 04/10/2013 21:48:22

Finally found a short treatise on the Straight Hobbing Method.

The following URL explains the "Straight Hobbing" method. Be sure to look to the left side of the referenced web page to get access to the discrete sections, e.g. See pages titled "Involute Gears", "Method", "Cutter", "Cutting".

http://homepage.ntlworld.com/peter_harrison/workshop/gearcutting/index.htm

That site provides step-by-step method and pictures. Note: Neither "Straight Hobbing" nor "lands" are used in that article.

Thanks to those who provided all of the useful information.

Paul

Edited By Paul Fallert on 04/10/2013 21:46:25

For those of you still having trouble with this concept, MEW #131, page 26 does have pictures of how the progressive cutting of the teeth do form an involute gear tooth.

If you follow that article, you will find that you can "easily" produce workable gears.

To answer the suggestion about purchasing a spiral hob from say CDC in Hong Kong, the choice of available spiral hobs is limited. In my case, I need a 30 deg Pressure Angle with a 44DP for a repair part for a friend and not wishing to buy an odd tool that will only ever be used once.

Once you understand the process, with the Straight Hobbing technique, you can produce gears with unusual diametral ptiches and pressure angles at virtually little or no cost. You just need a piece of drill rod and the drill rod can be as small as 12mm. And one individual used a piece of tool steel from an old power chisel bit, first softening the steel, making the hob and then re-hardening the steel.

Maybe this thread would make a subject for an illustrated series in a future magazine article. (just kidding).

Paul

After the hob has been finished, the part of the process that I have not elaborated on is as follows [using vertical milling machine nomenclature for simplicity]

Position the gear blank on the table in an indexing fixture with it's axis aligned parallel to the length of the mill table. Lock the indexer spindle from rotation.

Place the hob in the vertical spindle. Align the Straight Hob's central land to the centerline of the gear blank.

Start the hob rotating and move the table's Y axis (the narrow table axis) so that rotating hob moves closer to the gear blank. Lock the mill table's Y axis. Now the gear blank is locked from rotation and the Y axis is locked, fixing the depth of cut.

Cause the table to move past the hob. The table would move on its X (long) axis, normally that would be a table moving from the Left to Right, assuming the gear blank had been positioned to the left of the spindle.

Return the table to its starting position. Do not climb mill with the hob.

Index the gear blank by one tooth. Unlock the Y axis and bring the hob closer to the gear blank so as to be able to make a deeper cut. Tighten the Y axis table lock. Make the next cut, again moving the table L-R. Repeat until all of the spaces between the gear blank's teeth have been cut.

Note: It should now be clear that you do NOT simultaneously index the gear blank while the hob is cutting, as that is what happens with a spiral hob, not applicable to a Straight Hob.

Paul

Andrew:

Thank you for your complete and most helpful reply.

Straight Hobbing is new to me, too. The hob is prepared without a helix ! Each land is perpendicular to the axis of the hob.

The term "straight hob", unfortunately. does not search well, but some books on gear hobbing make reference to the process, and Ivan Law makes a curt reference to the process in WPS#17.

You should have at least 5 lands for the method to work (even 3 will work on a small diameter gear) to create an involute tooth form. You cannot, for example have but one land, for it would not generate an involute tooth form. On a large gear, you need 7 lands.

As you surmised, you must manually index the gear blank for each tooth and you must make shallow passes of the hob cutter into the gear blank. The concept is for the lands above and below the central land to gradually remove a bit of metal with each index pass. The central land is the middle land (#3 in a 5 land hob) and it must be cutting on the centerline of the gear blank.

Straight hobs are EASY to make. The lathe tools are easy to grind accurately and quickly, unlike buttons. The process automatically corrects for all but the most egregious errors. It is best to file a thin sheet metal template for guidance in grinding the angle of the lathe tool to the pressure angle (PA), as in my case a 30 deg PA requires a lathe tool to cut a 60 deg groove between each land. Land spacing equals the Circular Pitch (CP), but to cut the grooves forming the hob lands since they are parallel, you only need to use your lead screw micrometer dial or lacking a lead screw micrometer or even lacking a lead screw, a dial indicator poised against the side of the saddle will accurately measure the distance moved between the lands. A screw cutting lathe is net required to make a Straight Hob, even a wood lathe could do it. The diameter of the material used to make the hob is not important, but of course you must take the diameter into consideration when deciding where to form the teeth. The number of teeth is not important. Each tooth must be relieved or it will not cut. I am thinking that rake might be helpful if the mill used to hob the gear blank/pinion is not substantial. The entire process could be done on a lathe with a milling attachment.

I suspect this is very old technology and may pre-date the screw cutting lathe, maybe going back to early clock and watch makers who needed a way to make gears and pinions more quickly than hand filing.

Paul

Andrew:

Restatement of the question:

Looking at the end of the hob, if I were to draw a "+" sign on the face of the hob with the center of the "+" sign crossing through the center of the hob and the horizontal bar of the "+" sign on the horizon, should the face of the first tooth formed in the hob be on this vertical line? or set back from the line by .010" to .062" as I have seen in some published articles?

Or, are you saying to place the face of the tooth on a radial line would be the same as placing it on this vertical line?

Paul