Hi there. I'm very new to the machinist world. As a hobby I build aircooled VW engines for people, and wanted to get away from having to pay a machine shop to do some of the work. I purchased a South Bend 9 with hopes of being able to do some of the machining myself. I've been working on getting all the parts I need to have a proper machine, and am at the point where I need some advice/guidance on how to properly shorten these cut to length pushrod tubes. They are a hollow steel tube, that I need to shorten to custom lengths. I'm at a loss as to what type of tooling I need to do this. Any advice will be greatly appreciated.
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Need to learn how to machine pushrods
- Thread starter Oildrips
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- Joined
- Feb 1, 2015
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Modifying existing push rods should not be difficult. A means of measuring the length of the mofdified rod to your specification is needed. If the degree of accuracy is a thousandth of an inch or more, dial or digital calipers will work. I would add a spindle stop to the list which will make the process much easier. The spindle stop would insert in the spindle bore and the rod inserted to touch the stop. This will give you a repeatable position for the rod when inserted in the chuck. Once you have set up your tooling to the correct length, each additional rod can be cut to the same length. You will need some sort of deburring device to dress the newly cut end. Ammunition reloaders have a deburring tool that caqn dress both inside and outside diameters. Depending on the hardness of the push rod, you will want either HSS or carbide tool bits.
Thank you for this. Any idea of what type/shape of tool I should be using? Would I be using a parting tool or machining from the tip down to my mark? I'm really really new at this stuff. I was playing around with a test pushrod last night, and couldn't get my tool to cut properly without beveling the ends.
This is the tool for deburring that RJ mentioned in his first post ( I think).
https://www.forsterproducts.com/product/inside-outside-deburring-tool/
About the cut off tool, what steel is the pushrod made of and what wall thickness?
How much does the blank need to be shortened?
https://www.forsterproducts.com/product/inside-outside-deburring-tool/
About the cut off tool, what steel is the pushrod made of and what wall thickness?
How much does the blank need to be shortened?
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Thanks for the link. The tubes are 3/8" diameter chromoly tubing 0.032in thickness. In need to cut off roughly 1/2 inch on each of 8.
What are you using to hold the tube in the lathe, a chuck, 3 jaw or 4 jaw or collet?
Do you have a QCTP with several holders?
And since you are 'really really new' to machining;
I would consider using a plumbers tubing cutter to get within 1/8th of the mark then face the end to final length. If you have a stop in the spindle like RJ mentioned then using a carriage stop for the facing operation should get them all the same length. If not just face to a mark on the rod.
For facing I would use a standard very sharp HSS facing tool.
I have both a 3 jaw and 4 jaw chuck available. I was using the 3 jaw last night, experimenting with grinding my own tool bits on an old pushrod. I don't have a QCTP.
Just on principle I would prefer the 4 jaw in order to have more grip on the rod and be less likely to deform it. I would not think that using a parting tool would go well for you with either chuck. With a collet maybe but I really think that a plumbers tubing cutter would serve you better.
Would you have a photo of your cutting tool for facing?
Would you have a photo of your cutting tool for facing?
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- Feb 1, 2015
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I don't think that I would bother with a parting tool. The tool has to be set up exactly on center to successfully part the tube. If there is any runout, there is a possibility of the tool breaking through one side of the wall and bending the rod . If the amount to be trimmed is small, I would just use a facing tool to cut it to the right length. If there is a fair amount to trim, I would cut the rod off with a hack saw, band saw, or cutoff saw, leaving about 1/8" for finishing in the lathe.