Jump to content
Mister Mad Mower

Buma Boring Bar

Recommended Posts

Just got this on an auction site .

Buma Boring Bar , 55mm to 90mm or so bore capacity .

Looks to be in good order but the tool holder is missing .

Motor / shafts / gears are all working fine so worth making a tool holder up for it .

I think the spring loaded adjustable cutting tool approach will be the best and easiest way of going about this , as a micrometer can easily be converted to allow for rapid and accurate setting .

My Wolseley WD2 will be the 1st victim as my 2nd engine was bought with a rusted bore that will benefit from a light cleaning as it were .

Looking forward to going from tedious to plain boring .........

Buma boring bar.jpg

Share this post

Link to post
Share on other sites
4 hours ago, Triumph66 said:

I had to look twice at the heading of your post! :lol:

Not a well thought out name from a marketing point of view , though 50 years ago iff you were gay you were simply happy .

Wonder how many things will take on a different meaning 50 years from now ! .

But in retrospect a Bolens Ride a Matic could make a good stable mate for a Buma Boring bar ? ..........

Share this post

Link to post
Share on other sites

2 pictures from Blackpool illuminations , we went for a look after picking the Buma up in Lancaster .

The Old trolley bus is a delighful Old machine , as is the tower in the background.

The Tardis ( is this the oldest machine on the planet ? ) and Darleks are a 60's icon still being used today in the tv show Dr Who .



Share this post

Link to post
Share on other sites

Been busy restoring the " BUMA" , got it striped and rebuilt with a new coat of paint ( Brush on machine enamel ) to keep it good for another 50 years ! .

This turned out to all origonal , never been apart .I know this due to the knurled adjuster on the top having a grub screw to hold the centering shaft .

The grub screw had a plug over it and the knurling had been done last to hide it all ? .

I had to drill the plug out so as to be able to remove the grub screw and so split the gearnbox cases .

I have left the hole so i can easily take it apart for greasing etc in the future .

I found the grub screw after i noticed a scribed line on the front face of the knurled adjuster , pointing in line with what looked like a keyway down inside so i drilled down and found a cavity , with the grub screw 2 or 3mm below  .









Edited by Mister Mad Mower
extra information

Share this post

Link to post
Share on other sites
2 hours ago, Stormin said:

That's a nice piece of kit. :thumbs:

It's a heavy bit of kit , around 70KG / 140lbs or so .Good job the motor has a quick release to take a bit of the strain out of lifting it ! .

But yes , it is built to last .Even the main bar has twin Timken taper roller bearings with a 1 1/2" adjuster nut at the top to tighten them up .

A bit of a shock really as i was expecting plain bronze or brass split bearings .

And the metal componets which looked beyond redemption have all polished up a treat .( shiny )

I like the 2 oiler caps on the motor , even these have taper copper springs under them to keep the felt pads in contact with the shaft .

To realise the size , the main bar is 2" / 55mm diameter and the machine is 3 feet high .

I am currently working on new tool holders to fit into the head so i can use 8mm boring bars with the indexable SCLCL bits to bring it into the 21st century .

And i am still awaiting delivery of the braided wire wrap so i can wire it up nice and neat .

Have connected it up and it takes around 7 mins to wind down it;s full 12" of travel , So around 2 inches a min feed rate giving around 1 thou per revolution advance .

Wont be long before it gets a good work out .


Share this post

Link to post
Share on other sites

Mister Mad Mower,


Hello, I've just joined this group so that I could contact you. I've recently bought a Buma boring bar like yours and I'd like some advice/information if that's OK?. It came with all the tools, etc, but when I was in the motor trade 50 years ago I used to use a Van Norman boring bar and many, if not all, of the controls are quite different. I managed to figure out that the left hand thread screw item on the left of the bar (as you face it) is the lock for the screw drive to make the bar descend through the cylinder. However, there's also a similar arrangement at the top of the bar, and I haven't yet figured out what that one does. I also have no idea why there's a spindle sticking out of the left hand side of the unit that looks very like the one that the bar winding handle uses on the right of the unit. Furthermore, you mentioned a quick release for the motor. I haven't yet spotted that, so would be grateful for any photos of that item as well. 


I've attached some photos of the unit I've purchased, and included a photo of the jig it came with, that's used for holding the cylinder that's being bored.


Best regards,


Buma 1.jpg

Buma 2.jpg

Buma 3.jpg

Buma 4.jpg

Buma 5.jpg

Buma 6.jpg

Buma 7.jpg

Buma jig 1.jpg

Buma tools 1.jpg

Share this post

Link to post
Share on other sites

Hi Bob , sorry about the delay but i lost all my login details as ive not been on here for ages , Had to create a new account just to reply .

Here we go  -

For moving around it's best to remove the motor as this almost halves the weight .

The main pulley has the drive lock fitted , engage for cutting and dissengage for winding back / tool sharpening .

You found the feed lock to the right of the main pulley , as you say this locks the shaft to engage the cutting feed .

Under this is the plain shaft a pulley guard should be fitted to .

Above the motor is the plain shaft the tool holder slides onto ( center top of the image of the open box ) for sharpening the cutting tools on the little diamiond wheel behind the drive pulley .

The knurled knob on the top has 2 functions , 1- to centralise the boring bar in the cylinder 2 - to lock the tool holder in the boring bar

Basically drop the bar in the cylinder without the tool holder fitted and wind the fingers out to centralise the machine , then after clamping it in positon release the fingers and wind the knurled knob back which also raises the locking pin in the boring head so after youve set the tool in the holder you can slide it into the bar end and turn the knurled knob down to locate and lock the tool holder in place .

You should be ok with measuring the bore and setting the tool in the holder using the micrometer , the same hole that locates and locks the tool holder aligns the tool holder on the micrometer .

On the side is the auto stop , set the depth of cut on the bar so it knocks the switch off once the tool has cleared the bottom of the cylinder .

See youve got the table , mine is a portable one that simply sits atop the engine and a bar drops down the adjacent cylinder and a cross bar is used to clamp the machine in place using the engine block .

Once again appologies for the late reply but i am back on here now so should be able to keep up from now on .

Share this post

Link to post
Share on other sites

Mister Mad Mower 2,


Thank you very much for your reply to my questions. Since posting them up I managed to find someone who had an imprint of the Buma Operator's Manual, so I bought a copy and have it sitting in my garage, alongside the boring bar. Having figured out how to make it all work I was then able to sharpen one of the tools, and adjust the micrometer to get within a couple of tenths of a thou accuracy when setting the tool to cut a particular size. I practiced my reboring skills by boring out two barrels I had sitting around, and have practiced honing them as well with the two kits I bought (one from India and the other from America). I've attached some pictures to show you that underneath all the grime the old girl wasn't so bad after all, and there are a couple of photos of one of the bores after I'd bored and honed it to a nice criss cross finish. The only thing is that the new stones chattered a bit, so I'll have to dress them back a bit to stop that from happening in future.


By the way, your restoration of your boring bar is stunningly good. I'll never manage to emulate that, but after a good oiling and some slight adjustment of the Allen bolts on the main bar clamp I've managed to set the bar to move smoothly up and down almost to the very limit of it's downward movement. I've put a new drive belt on it as well, and I also found that the metal springs that are supposed to hold the centring fingers were like worn out knicker elastic, so I've used a narrow gauge elastic cord instead. It does the job, and doesn't present any problems. It's also easy and cheap to replace if it breaks, as I have a long roll of it in my garage.


So I've now started advertising my services on various forums for others who share my hobby of flying around in microlights. I've also advertised on a classic car site, but I need to start advertising on classic motorcycle and scooter sites, and I also need to make up a clamp for attaching the boring bar to car engine blocks. The clamping mechanism I used to use on the Van Norman boring bars I used when I was a full time engine reborer aren't the same as the design for the Buma, so I'll have to see if I can get one or two made up so that I can bore out anything from a Series A engine to a V8.


I'll have plenty of time for this though after the end of April when I retire from my current job. So I'm looking forward to spending more time in my garage this coming summer, and fully re-acquainting myself with the finer points of boring and honing various sized cylinders, both 4 stroke and 2 stroke. While I'm at it I also hope to recondition some cylinder heads as well. I've got hold of a valve seat grinding kit almost identical to the one I used to use in the motor trade, and I've also got a valve cutter that can recut the seat on the valves. All I need for that is a new pair of drive belts, as it uses two of them to gear the speed of the valve spinning motor down. The trouble is they aren't like V belts, but instead are flat, like a piece of inner tube, and I don't know if I'll be able to get them, as the apparatus is quite old now. I'll have to Google around to see what I can find.


Once more, thank you for taking the time to reply to my questions, and I hope your boring bar will prove to be as useful to you as I'm hoping mine will be to me.


Best regards,








Buma 2.jpg

Buma 3.jpg

Buma 4.jpg

Buma 5.jpg

Mics 2.jpg

Hone 1.jpg

Bore top 1.jpg

Bore bottom 2.jpg

Bore top 3.jpg

Buma 1.jpg

Edited by BobH
Picture appeared in the wrong place so I deleted it, or thought I had, but it's now appearing last instead of first. Doh!

Share this post

Link to post
Share on other sites

Hi Bob , yours look pretty good for it's age .Mine was solid rust but as it's British it cleaned up and polished nice and easy .

The bore looks good , love the Rotax engines .A friend had a 650cc bike .90mph in 3rd gear in around 4 seconds .

The clamp works by having a long threaded bar to drop down through one of the engine bores so you can secure a cross plate under the cylinder liner .Using a toggle bar at the top to turn the cam to clamp the machine down .( shown in your images as the plate / cam under the rear of the motor )

Belive that it works the same with the table ,

I re wired mine and added the plastic expanding cable sleeveing to the cables to stop any damage occuring to them .

The return spring for the centering fingers is a real problem , unless you realise the model Mamod steam trucks use a long one as the drive belt ........

I got one and cut it to length , then twisted the springs together and i added a spot of solder over the joint to make sure it didnt slip apart when the machine was opperating .

I am busy making a new tool holder . Bought a few small boring bars that take the tri pojnt carbide tips , Thinking along the lines of modernising to bring the cut upto modern expectations iff you know what i mean by that .

Also got the metal and a new micrometer head unit to make up a new tool setter for the boring bar unit when i get it finnished as the bars are cranked so the alignemt will be out between the center line and the cutting tool iff you follow .( the tool will be in and cutting before the head enters the bore ) .

Has your's got the number plate on it ? Mine is number 34 , just wondering mainly to see iff earlier ones were red and older ones blue ?

Share this post

Link to post
Share on other sites



Thanks for your reply. The number on mine is 5080, and it's an A.P.M. model like yours, so one of the later ones I think. There's one on Ebay at the moment in Northern Ireland, and that's blue like mine. However, there's also another one advertised on Ebay that doesn't look to be in very good condition. It's green and has a plate on it saying it's the AU model and the number 631. It's also got a very odd looking cutter mic, so I guess different models had slightly different cutting methods, and different colour schemes to help identify them. I must say I prefer the bright red of yours to the rather washed out blue of mine, but I wonder if they changed the colour scheme to prevent confusion between their tool and the American Van Norman boring bars which are also bright red.


Regarding the Rotax barrels. They are off a converted snowmobile or hovercraft engine that was used to power one of my microlight aircraft. The particular pair of barrels I've been playing with both had broken exhaust manifolds, so I decided to use them as practice bores as I don't have any aluminium welding kit to try and weld the manifold castings back on. Even if I did get them welded the face of each manifold would then have to be machined back exactly square to the original angle so that the exhaust header could bolt to it successfully. As it is I now have something to practice on with my boring and honing equipment, and I've got another spare engine sitting in the garage should I need it, so no great loss to the microlighting world.


I've attached some photos of the engine before the manifold castings broke away, so that you'll see where the barrels came from. The first photo shows the other side of the engine, but gives you a better overview of what the engine looks like in situ. Lastly, I've put two photos of the plane after it's had a clean. The last of those two shows the plane ready for me to go off on a flight, with a jerry can full of petrol strapped to the back seat as a backrest, and as a 20ltr supplementary tank to the 47ltr plastic tank that's fitted under the engine. This means the plane could theoretically fly with just me in it for just under 8 hours, at around 50 - 55mph, although I'd have to land after a while to top up the main tank from the jerry can. Also, my bladder wouldn't last that long, so I'd have to land anyway at regular intervals. :-)










Share this post

Link to post
Share on other sites

Tonly Gillam,


I had to look on Ebay for the spares for mine, but you could just google Buma Spares and see what comes up. There may be stuff on Gumtree, or on other sites as well as Ebay, but I don't know of anywhere else off hand.


Best of luck,



Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...