Tapered axle jigs

[Bigfish]

I've just ordered a High Level Jinty chassis kit for a first go, & Colin says I need 3 tapered axle jigs. Are these the right things, from Markits?

"M4RALJ-1ss S/Steel Alignment & Hornblock Jig to suit 1/8" Bearings (3)".

Or, if not, as usual, help!

Alan

[David B]

I couldn't find them in the Markits catalogue, but I got mine from London Road Models. There's an image you can open on the page.

David

[Jan]

I'd be wary of the Markits ones. The set I have are no-go in 1/8 axle bushes.

[martin goodall]

I'd be wary of the Markits ones. The set I have are no-go in 1/8 axle bushes.

They're not the only ones. At least one other well-known set of axle jigs turns out to be more than 0.125-inch diameter (and was mentioned, though not by name, by Barry Norman in his editorial in MRJ 120). I happen to know which one Barry meant but, like Brer Rabbit, "I ain't sayin' nuffink". The old rule of caveat emptor (Let the buyer beware) applies here as it applies everywhere else.

[Tim V]

I agree Martin, but one has to be an "informed" buyer. That was Barry's point.

There are "other" methods of building chassis, without relying on dubious jigs, or even expensive jigs Alan. Have a look around, you might be surprised what you might find.

[David B]

You engineers might quibble over the odd thou, but I have found the LRM tapered axles to be quite helpful (once one remembers to mark which piece goes on which side). Unless you are prepared to be more specific or at least explain, your coy comments are not helpful to those of us who are not engineers or 'in the know'. It is difficult to be 'informed' if problems are not explained and shared.

There are, as you say, other methods of building chassis, some of which are not cheap. Do you have any particular ones in mind which Alan might find useful?

David

[Jol Wilkinson]

The current LRM jigs are supplied by Markits, so it is possible that the "un-named" brand refers to LRM.

LRM taper end jigs were manufactured specifically for LRM, but were then "copied" and manufactured by Markits. It became more economic for LRM to purchase from Markits when stock of the original LRM version ran out.

The original LRM jigs and the early Markits version were produced from nominal 1/8" aluminium rod. Recently Markits changed over to 1/8" stainless steel. Markits claim that the aluminium would not fit in the colletts on the their auto if it was more than one and a half thou over sized i.e. 0.1265", which could occur if any surface corrosion affected the stock.

I emailed John Redrup this evening who has done some further investigation. Checking a selection of the stainless jigs in LRM stock with a micrometer gives measurements of 0.124" to 0.125". In theory the aluminium version were never larger than 0.1265" and I suppose it is possible that post manufacture surface corrosion could cause the diameter to "grow". However, polishing the jig with fine w&d would take care of that.

There have probably been six LRM customers over the last 15 years who have said exactly the same thing, "they will not fit my bearings". The reasons usually have been that the bearings have not been reamed or the bearings have a machining burr at one end. John believes it is possible for the jig to have a burr but he has never found one, although the ali ones did sometimes need cleaning to achieve a smooth surface.

I have two sets of the aluminium jigs that I have used with LRM bearings and hornblocks for a number of years without problems. However, I have found some other makes of bearings do need reaming with a 1/8" hand reamer before they will accept either a 1/8" axle or jig.

Jol

[Bigfish]

Many thanks to all of you for pitching in on that one. I'll give the Markits stainless axle jigs a go,& report back on diameter,but it sounds like they'll be fine.
I was going to invest in a one eighth parallel reamer in any case. Are all parallel reamers the same.?
BTW due to a Senior Moment I meant to write "Chris" (Gibbon) in my first post. What a nice man.
Alan

[Russ Elliott]

Checking a selection of the stainless jigs in LRM stock with a micrometer gives measurements of 0.124" to 0.125".

That is excellent.

Moreover, there is virtue in having bearing bores initially a tight fit on such jigs, because this will eliminate rod-to-chassis error when setting up the hornblock positions in the frames. After the hornblock positions have been set, the bearings can then be reamed to give a nice free running tolerance on 1/8" axles. The reaming process will remove material concentrically, thus preserving the true correlation of the axes.

[David B]

Thank you, Jol, for your clear and useful explanation.

David

[Alan Turner]

a 1/8" axle won't go in a 1/8" hole. You need a running clearence.

Alan

[Tim V]

I have argued, on my workbench thread, that matching the wheelbase to the rods is the wrong approach. An easier approach is to match the rods to the wheelbase. This dispenses with the need for any of these jigs. It is "another" way. There are other ways as well.

[Jan]

Checking a selection of the stainless jigs in LRM stock with a micrometer gives measurements of 0.124" to 0.125".

That is excellent.

Moreover, there is virtue in having bearing bores initially a tight fit on such jigs, because this will eliminate rod-to-chassis error when setting up the hornblock positions in the frames. After the hornblock positions have been set, the bearings can then be reamed to give a nice free running tolerance on 1/8" axles. The reaming process will remove material concentrically, thus preserving the true correlation of the axes.

I've checked mine - Markits aluminium - with my trusty M&W vernier mic, and get 0.1258" to 0.1260". I ream my axleboxes 0.125".

[Bigfish]

Just to report that my 4 quid's worth set of three stainless tapered axle jigs just arrived from Markits, 0.1245" - 0.125" by my vernier, ie spot on I should have thought, nice sliding fit in a 1/8" bearing.

I've just got to find some bits of spring to turn them into the deluxe version.

Thanks again for your advice on this, chaps.

Alan

[Horsetan]

I used to have loads of jig springs from Perseverance days, but can't remember where I put them. Have only been able to unearth two so far.....

Surely jig axle suppliers should include these again

[Bigfish]

Horsetan, well you would think so wouldn't you! As a newbie I have yet to assemble a box full of useful bits that will one day come in, so if you ever find the third one... On the positive side, my High Level Jinty kit just arrived. The etch is so lovely it's a shame to chop it to bits. Time for some soldering practice!

Alan

[Paul Willis]

On the positive side, my High Level Jinty kit just arrived. The etch is so lovely it's a shame to chop it to bits. Time for some soldering practice!

Alan

As has been said many times before, read the instructions very carefully, for they are excellent and if anything is going wrong it is more likely to be you than Chris. Stated in a kindly way, if you see what I mean.

Also, there is a comprehensive article by Tim Shackleton on improving a Jinty using the High Level chassis kit in MRJ 160. It was, entirely by coincidence, right next to my elbow when your message arrived.

Enjoy the kit! I'd rather be building High Level stuff than anything else.

Flymo

[Bigfish]

Thanks for your encouragement Flymo! The instructions are outstanding, aren't they?
Alan