Axle Jigs MRJ212

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Tim V
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Axle Jigs MRJ212

Postby Tim V » Wed Jan 18, 2012 6:48 pm

What did anyone think of the "ultimate" axle jig?

I couldn't decide what scale that chassis was in.
Tim V
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Jan
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Re: Axle Jigs MRJ212

Postby Jan » Wed Jan 18, 2012 7:31 pm

by Tim V » Wed Jan 18, 2012 7:48 pm
What did anyone think of the "ultimate" axle jig?

I couldn't decide what scale that chassis was in.
Tim V


Me neither. I wouldn't have described it as 'ultimate' but it looks like another option to consider for those with suitable workshop tools to produce their own. My "ultimate" axle jig would be something with the technical cojones of the 'connect everything together' of the Avonside tool, but the cost-effectiveness (and downright cleverness) of the tapered spigot (a la Rice/Markits...) Oh... and a free upgrade to 'Perfect Sight v2.0' for the operator....

Jan

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Jol Wilkinson
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Re: Axle Jigs MRJ212

Postby Jol Wilkinson » Wed Jan 18, 2012 8:10 pm

Jan wrote:
by Tim V » Wed Jan 18, 2012 7:48 pm

"but the cost-effectiveness (and downright cleverness) of the tapered spigot (a la Rice/Markits...)"
Jan


Invented by Iain Rice, put into production (some time later) by John Redrup of London Road Models, then copied by Markits.

Just to get the record correct.

Jol

Philip Hall
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Re: Axle Jigs MRJ212

Postby Philip Hall » Wed Jan 18, 2012 10:46 pm

I thought it quite useful, but I've used the tapered type for many years without problems. I always assumed - and I know that's dangerous - that the coned bit was concentric with the axle bit, and mine look to be so. Ditto for the parallel types.

Perhaps Jol could advise how they are turned - either in a collet or turned as one piece maybe?

Philip

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Ian Everett
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Re: Axle Jigs MRJ212

Postby Ian Everett » Thu Jan 19, 2012 12:13 am

I thought the article was about a solution to a non-existent problem. O.K., there may be a theoretical degree of inaccuracy but the commercial coned jigs seem to work well enough in my non-too-perfect hands to allow me to produce many free-running chassis - even in one case on an eight-wheeler.

Ian

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Jol Wilkinson
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Re: Axle Jigs MRJ212

Postby Jol Wilkinson » Thu Jan 19, 2012 9:00 am

Philip Hall wrote:I thought it quite useful, but I've used the tapered type for many years without problems. I always assumed - and I know that's dangerous - that the coned bit was concentric with the axle bit, and mine look to be so. Ditto for the parallel types.

Perhaps Jol could advise how they are turned - either in a collet or turned as one piece maybe?

Philip


Philip,

I'm afraid I don't know how they are turned.

John had them manufactured by an outside supplier (in a large batch as is typically the case with items like this). When Markits copied them and the original LRM batch had sold out, a repeat order became uneconomical, so John now gets his from Markits.

Jol

John Palmer
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Re: Axle Jigs MRJ212

Postby John Palmer » Thu Jan 19, 2012 5:55 pm

The article's author actually acknowledges that by reversing the workpiece in a chuck in order to turn both ends he will be generating surfaces around two different axes. Never mind, the incriminating step in the surface that results can then be concealed by relieving it away!

This is a job that I would have thought was better accomplished by turning between centres. Make the geometry of the machine work to your advantage.

Terry Bendall
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Re: Axle Jigs MRJ212

Postby Terry Bendall » Fri Jan 20, 2012 8:50 am

The author of the article correctly mentions that when using a three jaw chuck it may not be totally accurate. A new one should be, but it is wise to check, but one that has had a lot of use may not be sufficiently accurate for this job. Doing what is suggested in the article, and turning down a larger bar working from both ends and reversing the work in the chuck will, as John suggests still not be accurate, and in fact could make the problem worse. Turning in one setting between centres will be far more accurate. Alternatively using a collet chuck, which are normally far more accuate than a three jaw chuck, will give a greater accuacy, and a four jaw independent chuck will also be accurate, provided that you also have a dial test indicator and the patience to set the work running "true" - ie no ecentricity.

I brought a collet chuck and a set of collets some years ago and have found them very useful. Often you can by the collets separately so there is no need to by a full set of each size, just those that you are likely to use. One that is a nominal 3mm size should be able to accept a 1/8 inch axle for example.

Terry Bendall

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Ian Everett
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Re: Axle Jigs MRJ212

Postby Ian Everett » Fri Jan 20, 2012 9:15 am

Terry Bendall wrote: ie no ecentricity.


I would have thought that a little eccentricity was essential in an P4 modeler?

;)

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Tim V
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Re: Axle Jigs MRJ212

Postby Tim V » Fri Jan 20, 2012 3:40 pm

Terry Bendall wrote:I brought a collet chuck and a set of collets some years ago and have found them very useful. Often you can by the collets separately so there is no need to by a full set of each size, just those that you are likely to use. One that is a nominal 3mm size should be able to accept a 1/8 inch axle for example.

Terry Bendall

The colletts I've seen/used would not accommodate the difference between 3mm and 1/8"!

Other than that I entirely agree, why didn't Mr Ross use a collett?
Tim V
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Alan Turner
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Re: Axle Jigs MRJ212

Postby Alan Turner » Fri Jan 20, 2012 5:37 pm

The easiest thing to do is buy some 1/8 SS tube from Eileen’s and then make stubs with the requisite ends that fit into the tube. That way you can achieve the concentricity with a three jaw.

Alan

Terry Bendall
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Re: Axle Jigs MRJ212

Postby Terry Bendall » Sat Jan 21, 2012 8:49 am

clecklewyke wrote:I would have thought that a little eccentricity was essential in an P4 modeler?


Or in my case a great deal! :D

Tim V wrote:The colletts I've seen/used would not accommodate the difference between 3mm and 1/8"!


Could be the case Tim, perhaps it depends on the make and perhaps also the holder. 3mm is 0.118" and 1/8" is 0.125" so only 7 thou difference. I have some ranging from 3mm to 6.5 mm is 0.5mm steps, They were brought from Cowells and are intended for the Cowells lathe. They will accept the imperial sizes within that range.

Terry Bendall

Philip Hall
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Re: Axle Jigs MRJ212

Postby Philip Hall » Sat Jan 21, 2012 6:13 pm

I think the point that was being made in the article is that the critical part of the jig is that the end spigot should be completely concentric with the axle part. This is achieved by turning; but I take the author's point that by reversing and turning the other end there will be eccentricity in the middle of a (say) 35mm long jig axle, but it is some way from the bit where the coupling rods will sit - about 17mm. At that distance all the difference of a few thou is lost over the 17mm, and that the worst that could happen is that the axle boxes would be fractionally skewed in the hornblocks, if you could detect it.

This makes sense to me, although doing two stubs pressed into a central tube would be even better. Either way, I seem to get on fine with my tapered jig axles, so won't be changing.

Turning in a collet chuck also makes sense, although not an option available to me as I have a Unimat SL, for which such things are no longer available. Unless anyone out there has one and some axle sized collets they'd like to part with?

Philip

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Tim V
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Re: Axle Jigs MRJ212

Postby Tim V » Sat Jan 21, 2012 7:04 pm

I think the hole through the mandrel on your SL is 8mm. I don't think it will take 8mm WW colletts, but it I think it can take 6mm WW (WW - Webster Whitworth I think it stands for). I got a selection of 8mm colletts off Ebay, I've seen 6mm ones on there. Just have to make a drawbar......
Tim V
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shipbadger
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Re: Axle Jigs MRJ212

Postby shipbadger » Sun Jan 22, 2012 9:25 am

Hi all,

Cowells collets will accept a very small tolerance on either side of their intended capacity (which is why I have a metric and an imperial set) as will most of the older designs of collets but if you have a lathe able to take the chuck for ER type collets
these have a considerably greater ability to cope either side of their nominal capacity.

Tony Comber

nigelcliffe
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Re: Axle Jigs MRJ212

Postby nigelcliffe » Sun Jan 22, 2012 3:06 pm

Philip Hall wrote:Turning in a collet chuck also makes sense, although not an option available to me as I have a Unimat SL, for which such things are no longer available. Unless anyone out there has one and some axle sized collets they'd like to part with?


For the part in the MRJ, and if lacking collets, I'd have solved it by creating a collet for the job:
1 - turn one end of the axle jig in the three-jaw, including the parallel part along the axle;
2 - put some circa 4mm to 5mm brass bar in the three jaw, protruding by around 5mm, if its a key-tightened 3-jaw, then note which key hole is used. Drill then bore the brass bar to be a tight slide fit on an axle diameter.
3 - place a mark on the outside of the brass bar indicating alignment and depth to the "no 1 jaw" on the 3-jaw. Remove brass bar, slit lengthways with a fine saw opposite the mark, clean up any burrs.
4 - refit brass bar into 3-jaw, aligning marks, place axle made in (1) in hole, tighten on known key-hole, and complete work on other end of brass bar.

- Nigel


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