Gallery, Projects and General > Project Logs
Elmers #25, my first engine project
sbwhart:
Tim
We all have bad days if you've read my loco build thread you'll see I scraped off a cylinder casting that cost £80 when boring it, a new one cost me another £50:- ouch :bang:
Setting it up again and taking a light cut with a boring tool as John suggested will sort you out, it,s easyer to do the bore first and not worry too much about the size then make the cylinder to fit, most people do it that way. One little tip when boring:- boring tools have a tendancy to spring it will cut as you wind it back if you don't take the cut off, zero the dial and run the finishing cut through a couple of times until all the spring gone out of the bar.
Don't throw away any bits of broken tool steel:- centre drills, drill, mills cutters etc: as you can always grind them up for other uses.
Have fun
Stew
PS Just read your question on boring bars, if you have any HSS square steel you can grind this up into a boring bar, if it would help I'll post some pics tomorrow night of some bars I've made.
Cheers
Stew
spuddevans:
--- Quote from: sbwhart on May 10, 2009, 05:20:14 PM ---PS Just read your question on boring bars, if you have any HSS square steel you can grind this up into a boring bar, if it would help I'll post some pics tomorrow night of some bars I've made.
--- End quote ---
Thanks Stew, I'd love to see those pics. I do have a couple of spare HSS square blanks, but I think they're too large for the bore. ( I think the smallest HSS is 3/8 square, and I dont fancy grinding down the whole length to make it fit. ) I'll half to get some 1/4" Hss blanks.
Tim
bogstandard:
Tim,
As Stew says, You can grind up boring bars out of tool steel, it all depends how good you are on the offhand grinder.
For commercial ones, go down the page on here a bit and you will find some.
http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Lathe-Tools
Bear in mind, the smaller they go, the shorter they are, due to the forces acting on them, small ones are very easy to break. The smallest I have made using the drill method was 1mm, and it did the job, just.
You can also use the carbide tipped ones they sell in sets for mounting in boring heads. In fact if you look at the heads on those, they should be roughly the same shape as I am showing here.
Proper boring bars are in fact very easy to make yourself. But you do need to be fairly confident on the offhand grinder.
As shown on the C-o-C, turn up the shape required from silver steel. Try to keep the turned down bit as large as possible, this will reduce the danger of breakage and keep vibrations down.
Then grind the end bit to the shapes shown
When you are happy with the cutting head shape, heat up the cutting head only to cherry red, and hold it at that for a minute or so, then plunge it into water, but don't swizzle it about, that should keep stresses to a minimum and prevent fracture. I like to leave the centre turned down section unhardened and use its natural toughness to prevent breakage. Also, because I have only hardened the head, I don't temper it.
Touch up with a stone the front and side cutting faces.
Mount the cutting tip exactly on centreline, and remember, you should NOT be removing large wedges of metal with a small boring tool, drill out the hole to about 1/2mm under, and use the bar to bring the hole up to the right size.
Once you get used to it, you can easily knock one up in 15 to 20 mins.
Bogs
NickG:
Nice instructions on the boring bar John. I've got 1 just like that , I assume my grandfather must have made it at some point as the back end of it is relatively soft, it came with a load of bits and bobs I inherited from him. I could do with a few in various sizes.
Nick
spuddevans:
--- Quote from: bogstandard on May 10, 2009, 06:01:24 PM ---You can also use the carbide tipped ones they sell in sets for mounting in boring heads. In fact if you look at the heads on those, they should be roughly the same shape as I am showing here.
--- End quote ---
:doh: :doh: :doh: :doh:
You wouldn't believe how much of a numpty I feel. When I read your post Bogs it hit me like a ton of bricks, "I have a boring bar set for my mill" :bang: ( looks around for the hole in the ground to appear ) But I will file your C-o-C for future reference thankyou very much :thumbup:
Anyway, when I finally got over my numptyness this is what I got done today. I mounted the cylinder blank into the 4jaw, centered it and then took a couple of light skimming cuts and then about 4 repeated cuts to eliminate any springing of the boring bar.
I then remounted the cylinder the other way and bored out the pivot pin socket being careful not to break through into the piston bore.
Onto making the pivot pin. I didn't have any small diameter brass bar and I didnt fancy wasting some 3/4" square bar. I thought I'd try and be clever and use a little piece of 19mm x 3.5mm flat stock and turn it down. So I cut some off and chucked it in the 4 jaw.
Then to turn down the other end I wanted to chuck it in a ER32 collet to not leave markings on the pin, but I dont yet have a ER32 chuck for my lathe, but I do have a MT3 ER32 chuck for the mill, and the headstock on the lathe is also MT3. Not having a long enough drawbar I brought up the tailstock to ensure that I wasn't chased around the workshop.
Once the pivot pin was turned down to the right size to be tapped M3, I then cut the M3 thread. You probably noticed that the tailstock is removed for this, I ran the lathe at the lowest speed ( I thread at the lowest speed so I dont run into the chuck ) and as I found out when trying to remove the ER32 chuck it was well stuck in there.
Once that was done, I removed the pin and then loctited it into the cylinder. (it was a pretty good press fit)
And that's as far as I got today. Thanks to Bog's for reminding me of what I actually had sitting in the corner of the workshop.
Tim
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