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Harold Hall Simple Dividing Head

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Ray Caldon21/04/2015 05:10:37
15 forum posts

I am making Harolds' simple dividing head. The plans call for two cast iron bearings around 3/4", one at each end of the main body. I do not have any suitable cast iron in my scrap pile other than a 1/4" thick bar b que plate. I do have a piece of 2" brass round stock that would fit the bill. Would the brass be ok to use as a bearing or should I gang three pieces of the cast iron plate together? I am hoping the brass will be ok as it would be the easier option and the shaft will not be turning at any speed. Also the plans call for making the bearings a little undersize to allow a two part epoxy glue film to be used to fix them in the body. Is there a good reason not to use a press fit here? They will be bored through after fixing in place.What do the experienced guys on here think? Thanks in advance.Regards Ray.

Thor 🇳🇴21/04/2015 05:31:31
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1483 forum posts
41 photos

Hi Ray,

I suppose you could use brass instead of Cast Iron for the bearings, bronze would have been the material I would prefered though. Can't see any problem with using a press fit for the bearings.

Thor

Edited By Thor on 21/04/2015 05:33:15

Jens Eirik Skogstad21/04/2015 06:01:27
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400 forum posts
22 photos

I has used bronze as bearing in dividing rotary table, no problem. Bearing in dividing rotary table/dividing head must be fixed in house and the shaft/bearing must be without play and free rotating. Lubricate with grease.

John Haine21/04/2015 06:37:38
4428 forum posts
264 photos

I think brass would be absolutely fine! A DH doesn't rotate at any speed where bronze would make a difference and in its whole life is unlikely to make more than a few hundred turns. My Myford DH definitely sacrifices free rotation for low play.

Clive Hartland21/04/2015 07:41:29
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2759 forum posts
40 photos

I have made this simple dividing head and used cast iron, it did not cost much and was easy to machine when fitted into the main body. You have to make slots so that it can be clamped and I only wonder if the Brass will stay in place ? The dividing head is very easy to use and you will need a 60 tooth gear for easy dividing which if you buy for the dividing head will cost about £15 postage included. I have done several jobs now and I see it as an essential tool in my set up. Obviously you may have a gear already in a lathe set.

Clive

Ray Caldon21/04/2015 08:16:34
15 forum posts

Thanks for the speedy replies. I think you are right Clive, the slots would preclude a press fit. I see now why Mr Hall specified 2 part epoxy. I will try and source some cast iron but if that fails I will go ahead with brass and epoxy it in as per the plans. And yes I do have suitable gears already. Thanks again to all.

Regards

Ray

Harold Hall 121/04/2015 11:09:43
418 forum posts
4 photos

Just to warn you, Ray, there is a small error on the drawings, not too serious though, you do not end up with scraped parts. Rather than detail it here it is included on my website, see this page.

In use, typically, it can produce some useful divisions, such as 125 for a 8TPI leadscrew dial, and 96 used in clock making, neither of which can be achieved with the Semi Universal Dividing Head. In both cases, as in almost all others, it could not be simpler as one has only to step from gear space to gear space so it is impossible to make a mistake. If you do move through two gear spaces then it becomes obvious and it is just a case of moving back to cut the missing gear, or engrave the missing line.

For the lower number is does of coure require one to move through more than one gear space. Just mark the gear with a marker pen before placing it onto the dividing head

Even producing 360 divisions one just has to move one gear space at a time. But in this case there is a surprising result. As you move from gear space to gear space it will be seen that some divisions are missing. However, when you complete one turn of the gear being used, then going round again it will be seen that some of the missing division then start to be made. It is a case of keep going until all the divisions are completed. It is still impossible to place a division in the wrong place. One minor complication of this is that it is difficult to know where the longer lines have to be. But making them all the same length first, then going round again to lengthen those that need this is not particularly difficult.

Harold

Edited By Harold Hall 1 on 21/04/2015 11:14:15

Enough!21/04/2015 18:14:33
1719 forum posts
1 photos
Posted by Ray Caldon on 21/04/2015 08:16:34:

I will try and source some cast iron

Try the small, cast-iron exercise weights that the sports stores etc sell. Inexpensive source of small cast iron sections.

duncan webster21/04/2015 19:20:07
3710 forum posts
69 photos

Was this published in MEW? I'm too mean to buy the book!

Clive Hartland21/04/2015 19:26:25
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2759 forum posts
40 photos

When the 2 slots are cut to allow the clamping of the spindle is it possible to just mill one big slot across the body, it would save a lot of work with the slitting saw?

Clive

Zulu Timing21/04/2015 20:01:27
2 forum posts
Posted by Harold Hall 1 on 21/04/2015 11:09:43:

Just to warn you, Ray, there is a small error on the drawings, not too serious though, you do not end up with scraped parts. Rather than detail it here it is included on my website, see this page.

........

Harold

Edited By Harold Hall 1 on 21/04/2015 11:14:15

Dear Harold,

I registered to the site just to be able to ask about your site and to inform you that it is not working well. I can see the first page but the other pages (like the one in your post) seem to be missing.

I love your work and I was just checking your site to see if you posted any new work since my last visit, and the search for your name brought me to this well known forum and I took the opportunity to ask about the site.

With respect.

Regards.

Ray Caldon22/04/2015 08:01:56
15 forum posts

Harold thanks for the info re your dividing head. I have made a good start with the spindle having cut the thread, collar and shoulder to the same spec as my lathe which is an Australian made New Gregco by Brackenbury and Austin. I think it is similar to a myford, in size anyway. It is quite worn but I am enjoying the challenges it presents. I am slowly making small improvements to it as I learn. I need the dividing head to make some useable dials as the originals are too small . I may even have a go at your scribing device thats in "Dividing". Currently waiting for the Milling book to arrive as I think I need the build description so I avoid the rookie mistakes I am sure to make. Like today, spot drilling the main body to base mounting holes. I broke a centre drill in the very first hole. Could not get the tip out no matter what I tried so I have had to relocate one hole. Hahaha typical of my hamfistedness. Today I used co ordinate plotting to set out the holes mentioned and it was a lot of fun and I seem to have got an accurate result. My mill is just a chinese round column one but it does a good job laying out the co ordinates. Thanks to all the other guys that have replied. I am still racking the brain trying to think of a source of cast iron for the bearings. I have a week or so as I am waiting on a larger boring bar and a book to arrive and if I don't find any I'll go with brass. I did think of weights as a source but a guy here in Australia has warned against using them as they are low quality iron, mostly slag in his words. I don't have a boring head so I bored the hole in the body on the lathe face plate. Still laying awake at night thinking of how I will tackle the bearing bore. Maybe on a bar between centres with the body mounted on the cross slide.
Regards
Ray

Neil Wyatt22/04/2015 09:04:23
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Moderator
18899 forum posts
734 photos
80 articles

> I did think of weights as a source but a guy here in Australia has warned against using them as they are low quality iron, mostly slag in his words

They are cheap enough to experiment with. I've seen faceplates and flywheels made out of very nice CI from dumbell weights - they are big enough to cool slowly (= few chill spots), although I bet there are some nasty ones out there too - just like the untouchable sash weight under my bench!

Neil

Ray Caldon23/04/2015 06:22:13
15 forum posts

You are right Neil, nothing ventured nothing gained. I do have one of those small dumbbell type hand weights my wife used to take walking with her and the ends are round and a bit over 2"" diameter to the eye. Think I'll hack off the plastic covering and take a look. Cut in half they would be dead easy to chuck up as well.

Ray

wheeltapper23/04/2015 11:21:49
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423 forum posts
98 photos

I've got two cast iron weights from the bases of anglepoise lamps and I don't think semtex would touch them.

Roy.

Bazyle23/04/2015 13:54:04
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6181 forum posts
222 photos

This isn't a bearing belting round all day. Mild steel will do. Also brass, bronze, delrin, tufnol and wood and the bit of stale cheddar I had for lunch. The softer materials might distort a little if you were using it for super heavy cuts but not much stress in scribing dials. You can always remake later when a pukka bit of metal comes along.
Rather than make fully undersize for glue, make to a good fit then leaving a full diameter bit each end take a tad off the middle for the glue. This is a common method of making sure a bit remains to ensure concentricity. Although not essential here it can be a learning excercise.

Harold Hall 124/04/2015 09:36:39
418 forum posts
4 photos

Sorry Zulu for the delay in replying but unfortunately I cannot give you a definite reason for the pages being missing. However, the most likely answer would be that my whole website was down, for some reason, at the time you attempted to view it, but you were able to view the home page as it was stored on your PC, as most browsers can do this if they are set up for storing pages viewed.

I have visited the website for the company who host my website to see if they had shut down for any reason recently. They have though produced a new website and this information does not now appear to be included.

If the site does not reappear then all I can suggest it that you contact your service provider to ask if they can explain why the site is missing.

With my website now getting between 12000 and 14000 visits a month I feel sure at least a few would contact me if the problem was widespread

Harold

Harold Hall 124/04/2015 09:53:16
418 forum posts
4 photos

You are correct Clive, it would be possible to slit fully across the head to make the two halves adjustable and without any loss to the working of the head. Having designed the head around 13 years ago I cannot say just why I did it that way but probably felt it looked a more engineered job if the centre portion was fully part of the main body.

With it slit fully across then a single slit to the separate the two halves would also work. I would though not like to widen the two collapsible halves and even if done I would then like the closing screws to be moved to remain central in each portion. With that said, I would still go along with the two slits as drawn to separate the two halves.

Harold

Clive Hartland24/04/2015 09:57:26
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2759 forum posts
40 photos

Hi Harold, I will re-engineer my block and mill across to widen the slot to the limits of the thin slots. I will report back if any problems. In fact a long endmill would make it much easier to machine and would not affect the operation of the dividing head at all. One operation instead of two !

Clive

Ray Caldon24/04/2015 10:22:05
15 forum posts

I have my cast iron. Thanks Clive, I did as you suggested and tried the cast iron dumbell I had. After removing the rubberised protective coating I sawed it in half and chucked one half up. I have done little more than turn the end of the thin piece round but it machined nicely and the finish is excellent. Looking forward to making the bearings. Although from now on I think I will make haste more slowly.Yesterday took me hours to set out and drill the base mounting holes in both parts i.e base and body using the co ordinate method. It was a good learning exercise but time consuming especially with that broken centre drill causing me to have to relocate one hole. Today laying on the couch I had a eureka moment and realised I could have just made a simple jig with a scrap of flat bar. Setting out the hole centres, drilling pilot holes and using it to match the holes in the two pieces. Hahaha I have much to learn. Anyway thanks to Clive and Bazyle for their advice.

Ray

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