Colchester Chipmaster

This may sound like an odd request bearing in mind I have owned my Chipmaster for more than ten years. The lock on the saddle is engaged with a 7/16” square bolt to the rear of the saddle and from aquiring my machine I used an old brass stop tap key which has suddenly gone walk about I cannot find it anywhere and I’m wanting to replace it but it is not listed or mentioned in the manual and everyone I have asked about it are as puzzled as I am as no one has ever seen one, could anyone shed any light on this item please.

Regards

Ernest

Ernest,

You may have to make one by filing out a square hole in a piece of drilled bar and then welding or brazing a T handle or similar to it.

If you Google square chuck keys all you see are the male versions and looking for hollow square keys only seems to go up to clock winding key sizes, nothing in the size you need..

Brian

Ernest

T handle box spanners in 7/16" from Smith & Francis here :- **LINK** . Site has an "expensive" look tho'.

Probably plenty of suppliers if you knew what to search for without getting umpteen million results for square drive sockets.

As Brian says easily made by welding or brazing if you have the kit.

Clive

I do not think Colchester ever supplied a spanner for this.

Whatever you make, it needs to be fairly shallow or it will foul the topslide when it is parallel to the spindle axis.

A good place to start might be a gas bottle spindle key and a file. Older ones appear to have more meat surrounding the square hole.

Thank you for all your replies and suggestions but I believe I have actually found the supplied tool list for a Chipmaster and now I know what I’m looking for I bet I have pushed them aside looking through second hand tools at steam rallies and model engineer shows. As soon as I found the list it stood out like a sore thumb and made perfect sense it is a combination spanner 7/16 sq. x 1/2” AF and it makes sense as the 1/2” AF is for the two locking nuts on the compound slide swivel... Doh

part number 81-153

again many thanks for all who replied and as a stop gap until I find one I’m going to make a new locking bolt with a 1/2” AF hex head and just use a standard 1/2” combination spanner.

if anyone would like to see the full list just let me know and I will list everything.

Ernest

Edited By Ernest Shirt on 20/07/2019 23:38:10

Edited By Ernest Shirt on 20/07/2019 23:38:39

Before you make the new bolt, try a 12-point 1/2" A/F ring spanner on the existing square bolt. Because of the chamfered corners, it fits with no more slack than a 7/16" A/F open ended.

If the original spanner was 7/16" square x 1/2" A/F, then maybe a drum brake adjusting spanner can be modified to replicate it.

Please post the tool list if you are able.

The list as requested

81-151 15/16 a/f x 3/4 a/f open end spanner

81-152 9/16 a/f x 11/16 a/f open end spanner

81-153 7/16 sq x 1/2 a/f combination spanner

81-154 15/16 x 11/16 a/f box spanner

81-155 Tommy Bar

81-156 3/8 a/f Allen hexagon key

81-157 5/16 a/f Allen hexagon key

81-158 7/32 a/f Allen hexagon key

81-159 3/16 a/f Allen hexagon key

81-161 1/8 a/f Allen hexagon key

81-262 3/32 a/f Allen hexagon key

that is the complete list for the Colchester Chipmaster and also I believe for some Bantams

Regards

Ernest

Edited By Ernest Shirt on 21/07/2019 18:31:27

Latest update

A very nice young lady from Colchester (thank you Lynnette) has sent me a copy of two manual pages one showing the toolkit items and the second being the list of these items. Please sent me your email if you would like a copy.

Ernest

Call me a heathen, but I have always used a 13mm ring spanner for this function. A bit of a loose fit, but given that not much pressure is required to lock the saddle, it works well enough for me.

You can only escape that epithet if you stipulate that it is the Continental model. As any fule no, a 1/2" ring spanner should be used on the imperial machine.

My Chippie has dual dials, does that count

If we are getting personal mines an hermaphrodite it’s fully DRO but it’s still got imperial nuts and as far as I’m aware even a metric chippy is imperial in everything but it’s feeds-screws and their nuts lol

Continental units have a different screwcutting gearbox as well the leadscrew. Mine is imperial, but does have the dual dials. which i have been told is quite rare. Very useful though.

From across the pond Mine has dual dials. Wondered what the funny numbers were for!

And strangely enough, although the Continental model has an impressive range of imperial threading abilities, I believe the dual dials only work on imperial feedscrews. Hence, you could have imperial threads on a Continental but could not have imperial dials.

The only serious thing an imperial machine cannot do is M12 (x 1.75) threads. However, with 36t and 63t change gears from an ancient Drummond, it can.

Hi DC31k,

"The only serious thing an imperial machine cannot do is M12 (x 1.75) threads. However, with 36t and 63t change gears from an ancient Drummond, it can."

Can you tell us more about it?

This is interesting. I mean where should these two above mentioned years be mounted on a Chipmaster?

Thanks!

Let's start slightly at a tangent: Chipmaster gears are 14DP, 14.5 degree PA, same as a Drummond or Myford M-type or Harrison L5 or 140 (and possibly an older Colchester Student or Master). The six-spline centre detail is discussed here: https://www.model-engineer.co.uk/forums/postings.asp?th=84252&p=1

There is someone on eBay called you_engraving who will cut these gears in delrin, including the centre detail, for what I consider a very good price.

Standard gears on a Chipmaster are 66t and 33t, giving 2:1 or 1:2 ratio. This does not change when you put the (55t/65t) metric translation gear into the train.

The theory behind it is: the relationship between 1.75mm and 1mm is 7:4 so if you put the location bar in 9, which gives multiples of 1mm pitch, alter the 2:1 (66/33) or 1:2 (33/66) ratios to 7:4 (63/36) or 4:7 (36/63) and flip the other lever between A, B, and C, one of the six possible combinations will give 1.75mm and another will give 3.5mm.

That ends the factual bit. Now everything that follows is potentially incorrect. It is a long time since I did the experiment so details are hazy and there might be a mistake below.

My pencil note in the handbook says 63/36 9C for 1.75mm and 63/36 9B for 3.5mm. What I cannot recall is if this was my initial calculation or is the final, correct result. I do remember that the first time I tried the gears, I did not get the expected pitch. I then either swapped the gears around or moved the A,B,C lever and it eventually worked. So what is written in my book may be correct or incorrect, but there are only six possibilities so it will not take long to find out which two are correct.

If the Saddle lock is 7/16" square, would not a 7/16" A/F spanner operate it?

I happen to have a Continental Chipmaster.

If anyone should stumble over a set of changewheels to cut imperial threads,

please let me know. I know a thread dial indicator is out of the question.

While the imperial version has it integrated in the apron - lucky you...

Cheers

Erik

PS: If your Chippie has a working variator - take care of it. Ask, if you don't know how.

Well I'll be....

Just bought a Myford M type with set of change gears, but the 36 and 63 are not here. The here are

65, 60, 40, 35, 30 and 20.

But thanks anyway, good to know that someone can make it from delrin , although I would make my own from steel or cast iron.

Howard Lewis, the saddle lock, mine is 7/16 square and the spanner says 7/16 on the star end, and 1/2 on the open end.

Erik Werner Hansen, mine still has the original variator. I change oil quite often, installed an hour counter on two of the motor's wiring. I keep a chart with oild changes and workimg hours. How do you take care of your variator?

Tiger