Chainsaw Repair

Chain - Grinders - Filing - Wood Milling - Tools - Welding - Machinist - Mowers - Tillers => Metal Lathe Milling Machinist => Topic started by: Al Smith on December 21, 2015, 06:15:10 am

Title: Methods
Post by: Al Smith on December 21, 2015, 06:15:10 am
Everybody has a method of machining cylinders and pistons and they all work .This is mine.

First on the piston I just chuck it in a long jawed 3 jaw with softeners .Shown is a 200T getting a pop up of maybe 10-15 thou .Budweiser can for softeners but I suppose Pepsi would work just as well.It holds pretty square believe it or not .Ya gosta remember it's a pert for a chainsaw not part of the space shuttle
Title: Re: Methods
Post by: Al Smith on December 21, 2015, 06:26:25 am
Next the cylinder.I stumbled on to this one night whilesipping on several brews reflecting my thoughts for the day.What if I said to myself,why not try --so I did .

I've got a Hardinge -Jorgenson 5C collette chuck that runs dead on .Using a piece of cold roll and screw on nylon arbors it cuts dead nuts .I make the arbors just short enough that the chamfer can be cut in the same operation .The arbors of which I have several are tight enough in the bore you have to tamp the cylinders on .

Shown is a 200T cylinder .It dawned on be I had no way to measure because it was so tiny so  I used a snap gauge and a set of 2-3 mics .Half azzed but it worked
Title: Re: Methods
Post by: Al Smith on December 21, 2015, 06:29:55 am
The one pic shows the wedges you use to remove a tapered drill chuck .They also work to remove a stubborn bearing from a Stihl chainsaw ;)
Title: Re: Methods
Post by: Cut4fun on December 21, 2015, 02:21:28 pm
Is that the lathe needing fixed now?
Title: Re: Methods
Post by: Al Smith on December 21, 2015, 08:49:59 pm
Yes, the electrons went funky and I got tired of fooling with it. I have a new solid state controller but working 7-12's haven't had time to install it .That ole gal is a good one when it runs .I think I could put threads on a darning needle .
Title: Re: Methods
Post by: awol on December 24, 2015, 08:35:45 pm
   The collet chuck makes it real handy, but I may use the screw on mandrel idea with my standard three jaw. I've been using one piece plastic mandrels, but they have a lot of deflection, even when supported with the live center.
Title: Re: Methods
Post by: mdavlee . on December 25, 2015, 09:41:55 pm
   The collet chuck makes it real handy, but I may use the screw on mandrel idea with my standard three jaw. I've been using one piece plastic mandrels, but they have a lot of deflection, even when supported with the live center.
What kind of plastic are you using?
Title: Re: Methods
Post by: awol on December 26, 2015, 11:51:28 am
    I don't know for sure what it is, I just picked up a couple long sticks at the scrap yard. It machines really nice, and works well enough for base cuts. I noticed when I run the live center up against the jug, if I apply to much pressure the runnout increases near the center, even though both ends are good.
Title: Re: Methods
Post by: mdavlee . on December 26, 2015, 12:03:30 pm
Some of what I had I was putting too much pressure on as well. Half the time I use ash rods for bases and sanding mandrels. Make them tight as will slide on there. I'm not getting any deflection that I can notice when cutting the base. I need to get a little more aluminum or Type 2 PVC. Hard to beat for rigidity on there.
Title: Re: Methods
Post by: weimedog on January 02, 2016, 12:08:21 pm
Very nice and obviously effect set of concepts. I found round nylon and Teflon blanks on ebay for arbors. I've since went to aluminum.

Stuff like this...these are usually "cut off" scrap

http://www.ebay.com/itm/1pc-New-100mm-Long-Dia-50mm-2-PTFE-Teflon-Round-Rod-Bar-/290951521113?hash=item43be0fe359:g:-~MAAMXQTT9RsTzm
Title: Re: Methods
Post by: Al Smith on January 03, 2016, 06:32:53 am
I'm not exactly certain what those nylon arbors are .They are scrap ends of round stock from the tool room at work .

The tool and die makers use this material for certain lifting fixtures etc to handle crankshafts cylinder blocks etc used in the manufacture of automotive engines .They use this hard nylon to prevent damage to the finished parts .

It might be some variation of nylon 66 .The material comes in blue,white and black ,assuming  the colors denote the duremeter hardness .At any rate those that I make run very true .

When I cut the arbors to size it's on the shaft and  in the collet with a live center in the tail stock so it's pretty much dead on .I've checked a cylinder when chucked for the cut with a dial indicator and it's right on ,almost no variation ,less than 1 thou .
Title: Re: Methods
Post by: mdavlee . on January 03, 2016, 07:04:08 am
The type 2 pvc is about the hardest plastic. I've started buying aluminum to make more mandrels in smaller sizes. Just takes me a while to get them turned taking small passes. Wish I had a gear drive lathe for that part.

Any one use belts for their small lathe that are Gates size 5m710? I needed 730 and didn't pay attention when I was looking at it and ordered 2 of them. Someone can have them for shipping.